PTI RAW Version 30 Manual Psse

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Chapter 3
Managing Power Flow Data
3.1 Overview: Managing Power Flow Data
This chapter describes the data requirements for establishing a power flow data set suitable for use
in steady-state analyses. The application of this data for planning and operations studies is treated
in detail in Chapters 4 through 10.

In addition to the basic data set describing the network elements, PSS/E requires other data and
control element files for specific applications. Those files and their data requirements will be
described in the subsections of Chapters 4 through 10, where they are appropriate.
Objectives of this chapter are to describe several aspects of data preparation, including:
•

Specific network data required and their format for importation into PSSIE.

•

Methods of importing data.

•

Means by which data can be listed and examined.

•

Methods to check data for errors and conflicts.

•

Data editing.

•

Data exportation.

•

Building a network using the Diagram View.

•

Building a network using the Spreadsheet View.

The user should be aware that not all the data described in this chapter are needed for all applications and that some data can be defaulted. The following subsection will indicate which data fall into
those categories.

3.2 Power Flow Data Categories
Representation of power networks in PSS/E comprises 16 data categories of network and equipment elements, each of which requires a particular type of data. The data categories and the order
in which they are input are shown in Figure 3-1.

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Case Identification

Bus Data

Load Data

Generator Data

Nontransformer Branch Data

Transformer Data

Area Interchange Data

Two-Terminal dc Line Data

]

Voltage Source Converter dc Line Data

Switched Shunt Data

Transformer Impedance Correction Tables

Multi-Terminal dc Line Data

Multisection Line Grouping Data

Zone Data

Interarea Transfer Data

Owner Data

FACTS Device Data

Figure 3-1. Power Flow Data Categories

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The bulk power flow data input facility, FiIe>Open... (Section 2.6.2) imports hand-typed power flow
source data from a correctly formatted Power Flow Raw Data File (.raw) and enters it into the load
flow working case, rearranging it from its original format into a computationally oriented data structure in the process.

All data is read in 'free format' with data items separated by a comma or one or more blanks.
Tabbed delimited data items are not recommended. The FiIe>Open... command may also import
binary saved case files (*.sav) containing power flow data as well as solution values and related
options (see Section 1 .8.2).

The following sections identify the power flow data categories in the order of presentation expected
in the Power Flow Raw Data File.

3.2.1 Case Identification Data
Case identification data consists of three data records.
The first record contains two items of data as follows:

IC, SBASE
where:
IC

Change code:

0 - base case (i.e., clear the working case before adding data to it)
1 - add data to the working case
IC = 0 by default.
SBASE

System base MVA. SBASE = 100.0 by default.

The next two records each contain a line of heading to be associated with the case. Each line may
contain up to 60 characters.

3.2.2 Bus Data
Each network bus to be represented in PSS/E is introduced through a bus data record. Each bus
data record includes not only data for the basic bus properties but also includes information on an
optionally connected shunt admittance to ground. That admittance can represent a shunt capacitor
or a shunt reactor (both with or without a real component) or a shunt resistor. It must not represent
line connected admittance, loads, line charging or transformer magnetizing impedance, all of which
are entered in other data categories.

Bus

Shunt
Admittance

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Bus data has the following format:

'NAME', BASKV, IDE, GL, BL, AREA, ZONE, VM, VA, OWNER

where:
I

Bus number (1 to 999997).

NAME

Alphanumeric identifier assigned to bus 'I'. The name may be up to twelve characters and must be enclosed in single quotes. NAME may contain any combination
of blanks, uppercase letters, numbers and special characters, but the first character must not be a minus sign. NAME is twelve blanks by default.

BASKV

Bus base voltage; entered in kV. BASKV = 0.0 by default.

IDE

Bus type code:

1 - load bus or other bus without any generator boundary condition.

2 - generator or plant bus either regulating voltage or with a fixed reactive power
(Mvar). A generator that reaches its reactive power limit will no longer control voltage but rather hold reactive power at its limit.
3 - swing bus or slack bus. It has no power or reactive limits and regulates voltage
at a fixed reference angle.
4 - disconnected or isolated bus.
IDE = 1 by default.
GL

Active component of shunt admittance to ground; entered in MW at one per unit
voltage. GL should not include any resistive admittance load, which is entered as
part of load data. GL = 0.0 by default.

Reactive component of shunt admittance to ground; entered in Mvar at one per unit
voltage. BL should not include any reactive impedance load, which is entered as
part of load data; line charging and line connected shunts, which are entered as
part of non-transformer branch data; or transformer magnetizing admittance, which
is entered as part of transformer data. BL is positive for a capacitor, and negative
for a reactor or an inductive load. BL = 0.0 by default.

AREA

Area number. (1 through the maximum number of areas at the current size level;
see Table 1-1). AREA = 1 by default.

ZONE

Zone number (1 through the maximum number of zones at the current size level;
see Table 1-1). ZONE = 1 by default.

Bus voltage magnitude; entered in pu. VM = 1 .0 by default.

Bus voltage phase angle; entered in degrees. VA = 0.0 by default.

OWNER

Owner number (1 through the maximum number of owners at the current size level;
see Table 1-1). OWNER = 1 by default.

VM and VA could be set to values obtained from a previously solved case if they were available.
Normally, however, they can be set to default value.

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When entering bus data in the Power Flow Raw Data File, bus data input is terminated with a record
specifying a bus number of zero.

3.2.2.1 Extended Bus Names
When bus data records are input, each bus is identified by either its number or its name. The name
comprises a twelve character alphanumeric in single quotes.

When the 'Extended Name' bus input option is enabled in the Misc>Change Program Settings
(OPTN)... dialog, data fields designating buses on load, generator, branch, transformer, area, twoterminal dc line, VSC dc line, switched shunt, multi-terminal dc line, multisection line, and FACTS
device data records may be specified as either extended bus names enclosed in single quotes or
as bus numbers.

As for data output, reports developed by PSS/E functions can be ordered in ascending bus number
or by the buses extended bus name, in alphabetical order. The setting of bus output to either bus
number or extended name is made using the Misc>Change Program Settings (OPTN)... option
(see Section 1 .7.4).
The requirements to specify an extended bus name are:
1.

It must be enclosed in single quotes.

The twelve-character bus name, including any trailing blanks, must be the first twelve
characters.

The bus base voltage in kV must immediately follow the bus name. Up to six characters
may be used.

For those data fields whose sign is used to indicate a modeling attribute, a minus sign
may be specified between the leading single quote and the first character of the twelvecharacter bus name.

Thus, valid forms of an extended bus name include aaaaaaaaaaaavvvvvv and
aaaaaaaaaaaavvv. For those data fields cited in (4) above, -aaaaaaaaaaaavvvvvv and
aaaaaaaaaaaavvt/ are also valid forms of extended bus names.

As an example, consider a 345 kV bus with the name FRONT-STREET. Its extended bus name
would be:
FRONT-STREET

345'

3.2.2.2 Using Defaults to Minimize Bus Data
Because there are default values for some of these data, you can include only the specific information you need. For example, if bus # 99 is a 345 kV, Type 1 bus without a shunt admittance, which
lies in Zone #3, the data line within the Power Flow Raw Data File could be:

99,,345,

1,,,,3

in addition, you name the bus ERIE BLVD and it has a 200 Mvar shunt reactor, the minimum data
line would be:
If,

99,

'ERIE BLVD', 345,1,,— 200,,3

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3.2.3 Load Data
Each network bus at which a load is to be represented must be specified in at least one load data
record. If multiple loads are to be represented at a bus, they must be individually identified in a load
data record for the bus with a different load identifier. Each load at a bus can be a mixture of loads
with different characteristics, (see Section 4.5).

"Ia

Each load data record has the following format:
I,

ID, STATUS, AREA, ZONE, PL, QL, IP,

IQ, YP, YQ, OWNER

where:
Bus number, or extended
Section 3.2.2.1).
ID

STATUS

bus name enclosed

single

quotes

(see

One- or two-character uppercase non blank alphanumeric load identifier used to
distinguish among multiple loads at bus 'I'. It is recommended that, at buses for
which a single load is present, the load be designated as having the load identifier
'1'. ID = '1' by default.
Initial load status of one for in-service and zero for out-of-service. STATUS = 1 by
defau It.

AREA

Area to which the load is assigned (1 through the maximum number of areas at the
current size level, see Table 1-1). By default, AREA is the area to which bus 'I' is
assigned (see Section 3.2.2).

ZONE

Zone to which the load is assigned (1 through the maximum number of zones at
the current size level, see Table 1-1). By default, ZONE is the zone to which bus
'I' is assigned (see Section 3.2.2).

Active power component of constant MVA load; entered in MW. PL = 0.0 by default.

Reactive power component of constant MVA load; entered in Mvar. QL = 0.0 by
defau It.

Active power component of constant current load; entered in MW at one per unit
voltage. P = 0.0 by default.

Reactive power component of constant current load; entered in Mvar at one per
unit voltage. IQ = 0.0 by default.

Active power component of constant admittance load; entered in MW at one per
unit voltage. YP = 0.0 by default.

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Reactive power component of constant admittance load; entered in Mvar at one
per unit voltage. YQ is a negative quantity for an inductive load and positive for a
capacitive load. YQ = 0.0 by default.

OWNER

Owner to which the load is assigned (1 through the maximum number of owners at
the current size level, see Table 1-1). By default, OWNER is the owner to which
bus 'I' is assigned (see Section 3.2.2).

As for buses, it is possible to enter only the data items which apply to the analyses to be undertaken.
An example entry in the Power Flow Raw Data File for a constant MVA load of 100 MW and 50 Mvar,
at bus 123, with no assigned area, zone or owner, would be:

123, '1',,,,100,50
Within the Raw Data File, load data input is terminated by a record specifying a bus number of zero.

3.2.3.1 Load Characteristics
The constant power characteristic holds the load power constant as long as the bus voltage exceeds
a value specified by the solution parameter PQBRAK. The constant power characteristic assumes
an elliptical current-voltage characteristic of the corresponding load current for voltages below this
threshold. Figure 3-2 depicts this characteristic for PQBRAK values of 0.6, 0.7, and 0.8 pu. The user

may modify the value of PQBRAK by selecting Power Flow>Solution>Parameters... and modifying the Constant power characteristic threshold (PQBRAK) located on the General tab.

0
0
0.0

0.6

0.7

0.8

1.0

1.1

Voltage

Figure 3-2. Constant Power Load Characteristic
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The constant current characteristic holds the load current constant as long as the bus voltage
exceeds 0.5 pu, and assumes an elliptical current-voltage characteristic as shown in Figure 3-3 for
voltages below 0.5 pu.
Further details on load characteristic and modeling requirements are given in Section 4.5.

0
0
0.5

1.0

1.1

Voltage

Figure 3-3. Constant Current Load Characteristic

3.2.4 Generator Data
Each network bus to be represented as a generator or plant bus in PSS/E must be specified in a
generator data record.
In particular, each bus specified in the bus data input with a type code of two (2) or three (3) must
have a generator data record entered for it.

Generation

U
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Each generator has a single line data record with the following format:

ID, PG, QG, QT, QB, VS, IREG, MBASE, ZR,
STAT, RMPCT, PT, PB, 01, Fl
04, F4

ZX, RT, XT, GTAP,

where:
I

Bus number, or extended
Section 3.2.2.1).

bus name enclosed

single

quotes

(see

One- or two-character uppercase non blank alphanumeric machine identifier used
to distinguish among multiple machines at bus "I'. It is recommended that, at buses
for which a single machine is present, the machine be designated as having the
machine identifier '1'. ID = '1' by default.

Generator active power output; entered in MW. PG = 0.0 by default.

Generator reactive power output; entered in Mvar. QG needs to be entered only if
the case, as read in, is to be treated as a solved case. QG = 0.0 by default.

Maximum generator reactive power output; entered in Mvar. For fixed output gen-

erators (i.e., nonregulating), QT must be equal to the fixed Mvar output.
QT = 9999.0 by default.
QB

Minimum generator reactive power output; entered in Mvar. For fixed output
generators, QB must be equal to the fixed Mvar output. QB = -9999.0 by default.

Regulated voltage setpoint; entered in pu. VS = 1 .0 by default.

IREG

Bus number, or extended bus name enclosed in single quotes (see
Section 3.2.2.1), of a remote type 1 or 2 bus whose voltage is to be regulated by
this plant to the value specified by VS. If bus IREG is other than a type 1 or 2 bus,
bus "I" regulates its own voltage to the value specified by VS. IREG is entered as
zero if the plant is to regulate its own voltage and must be zero for a type three
(swing) bus. IREG = 0 by default.

MBASE

Total MVA base of the units represented by this machine; entered in MVA. This
quantity is not needed in normal power flow and equivalent construction work, but

is required for switching studies, fault analysis, and dynamic simulation.
MBASE = system base MVA by default.
ZR,ZX

Complex machine impedance, ZSORCE; entered in pu on MBASE base. This data

is not needed in normal power flow and equivalent construction work, but is
required for switching studies, fault analysis, and dynamic simulation. For dynamic

simulation, this impedance must be set equal to the unsaturated subtransient
impedance for those generators to be modeled by subtransient level machine
models, and to unsaturated transient impedance for those to be modeled by classical or transient level models. For short-circuit studies, the saturated subtransient
or transient impedance should be used. ZR = 0.0 and ZX = 1.0 by default.
RT,XT

Step-up transformer impedance, XTRAN; entered in pu on MBASE base. XTRAN
should be entered as zero if the step-up transformer is explicitly modeled as a network branch and bus "I' is the terminal bus. RT+jXT = 0.0 by default.

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Step-up transformer off-nominal turns ratio; entered in pu. GTAP is used only if
XTRAN is nonzero. GTAP = 1.0 by default.

GTAP

Initial machine status of one for in-service and zero for out-of-service; STAT = 1 by

STAT

defau It.

Percent of the total Mvar required to hold the voltage at the bus controlled by this
bus 'I' that are to be contributed by the generation at bus 'I'; RMPCT must be positive. RMPCT is needed if IREG specifies a valid remote bus and there is more than

RMPCT

one local or remote voltage controlling device (plant, switched shunt, FACTS
device shunt element, or VSC dc line converter) controlling the voltage at bus IREG

to a setpoint. RMPCT is needed also if bus "I" itself is being controlled locally or

remotely by one or more other setpoint mode voltage controlling devices.
RMPCT = 100.0 by default.
PT

Maximum generator active power output; entered in MW. PT = 9999.0 by default.

Minimum generator active power output; entered in MW. PB = -9999.0 by default.

Owner number; (1 through the maximum number of owners at the current size
level: see Table 1-1). Each machine may have up to four owners. By default, 01 is
the owner to which bus 'I' is assigned and 02, 03, and 04 are zero.

Fraction of total ownership assigned to owner Oi; each Fi must be positive. The Fi
values are normalized such that they sum to 1 .0 before they are placed in the
working case. By default, each Fi is 1.0.

In specifying reactive power limits for voltage controlling plants (i.e., those with unequal reactive
power limits), the use of very narrow var limit bands is discouraged. The Newton-Raphson solutions
require that the difference between the controlling equipment's high and low reactive power limits
be greater than 0.002 pu for all setpoint mode voltage controlling equipment (0.2 Mvar on a 100
MVA system base). It is recommended that voltage controlling plants have Mvar ranges substantially wider than this minimum permissible range.

3.2.4.1 Modeling of Generator Step-Up Transformers (GSU)
Before setting-up the generator data, it is important to understand the two methods by which a generator and its associated GSU are represented.

The Implicit Method
•

The transformer data forms part of the generator data list

•

The transformer is not represented as a transformer branch

Figure 3-4 shows that Bus K is the Type 2 bus. This is the bus at which the generator will regulate/control voltage unless the user specified otherwise.
As with other data sets, some of the generator data have default values and, further, it is not necessary to specify all the data for basic power flow studies.
If an implicit transformer model is used, the minimum data set needed is:

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'ID', PG, QG, QT, QB, VS,,,,,RT, XT, GTAP

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Bus K

p.u. on MBASE

TG:l
High

XT
Generator Step-Up
Transformer

Voltage
Bus

Generator

Figure 3-4. Implicit GSU Configuration — Specified as Part of the Generator

The Explicit Method
In this method, the Transformer data does not appear in the generator data. It is entered separately
(see Section 3.2.6) in a transformer branch data list.

In Figure 3-5, there is an additional bus to represent the generator terminal. This is the Type 2 bus
where the generator will regulate/control voltage unless the user specifies otherwise.

Generator
Terminal Bus

Bus K

Figure 3-5. Explicit GSU Configuration — Specified Separately from the Generator

Multiple Generators
If a generating plant has several units, they can be represented separately even if they are connected to the same Type 2 bus.

Figure 3-6 shows three Type 2 buses, each having two connected units. For generators 1 through
4, the GSU is explicitly represented while for generators 5 and 6 the GSU is implicitly represented.

200 MVA 250 MVA 200 MVA 250 MVA
X"=.26

X"=.22

X"=.26

X'=.22

800 MVA

X"=,25

X'=.25
All Transformers
At +5% Tap
on 345 kY Side

X=,033 on
100MVA

X=1B

X=1B on

800 MVA

800 MVA
1237

(345 kV)

Figure 3-6. Multiple Generators at a Single Plant
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To clarify the data requirements, Figure 3-7 shows a properly formatted listing for the generators in
Figure 3-6.
The separate transformer branches from Buses 1238 and 1239 to Bus 1237 are not included
in this generator list.

Generator Data Records:
1238 1 200
120 0
150 0
1238 2 250
1239 3 200
120 0
1239 4 250
150 0
1237 5 750
500 0
1237

500 0

750

1.03
1,03
1.03
1.03
1.06
1.06

0
0
0
0
0
0

200
250
200
250
800
800

0
0
0
0
0
0

.26
.22
.26
.22
.25
.25

0
0
0
0
0
0

0
0
0

.18
.18

1.
1.
1.
1.

1.05
1.05

50
50
50
50
50
50

1
1

0
0
1
1

200 60
250 75
200 60
250 75
760 240
760 240

1111111111111111
PG QG qT QB
(not specified)

VS IREGMBASE ZR,ZX RT,XT GTAP STAT RMPCT PT PB

Figure 3-7. Date Set for the Multiple Generators in Figure 3-6
Generator data input from a Power Flow Raw Data File is terminated with a record specifying
a bus number of zero.

3.2.5 Nontransformer Branch Data
In PSS/E, the basic transmission line model is an Equivalent Pi connected between network buses.
Figure 3-8 shows the required parameter data where the equivalent Pi comprises:
•

(R + ix) series impedance

•

Two admittance branches + jBch/2, representing the line's capacitive admittance

Data for shunt equipment units, such as reactors, which are connected to and switched with the line,
are entered in the same data record. The figure shows these shunts represented as (G + jB).

To represent shunts connected to buses, that shunt data should be entered in the bus data
record.

+j81

CII)

Figure 3-8. Transmission Line Equivalent Pi Model

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Each nontransformer branch data record has the following format:

I,J,CKT,R,X,B,RATEA,RATEB,RATEC,GI,BI,GJ,BJ,ST,LEN,01,F1,

,04,F4

where:

Branch 'from bus" number, or extended bus name enclosed in single quotes (see
Section 3.2.2.1).

Branch "to bus' number, or extended bus name enclosed in single quotes (see
Section 3.2.2.1). 'J' is entered as a negative number, or with a minus sign before
the first character of the extended bus name, to designate it as the metered end;
otherwise, bus 'I' is assumed to be the metered end.

CKT

One- or two-character uppercase nonblank alphanumeric branch circuit identifier;
the first character of CKT must not be an ampersand "&" (see Section 3.4.4.12 for
a discussion on use of the ampersand in designation of multisection transmission
lines). It is recommended that single circuit branches be designated as having the
circuit identifier '1'. CKT = '1' by default.

Branch resistance; entered in pu. A value of R must be entered for each branch.

Branch reactance; entered in pu. A nonzero value of X must be entered for each
branch. See Section 3.2.5.1 for a discussion of the treatment of branches as zero
impedance lines.

Total branch charging susceptance; entered in pu. B = 0.0 by default.

RATEA

First loading rating; entered in MVA. If RATEA is set to 0.0, the default value, this

branch will not be included in any examination of circuit loading. (See
Section 4.4.5.1.1).
RATEB

Second loading rating; entered in MVA. RATEB = 0.0 by default.

RATEC

Third loading rating; entered in MVA. RATEC = 0.0 by default.
Ratings are entered as:

MVArated = SQRT(3) x Ebase X 'rated X i06
where:
Ebase

is the base line-to-line voltage in volts of the buses to which the
terminal of the branch is connected

rated

is the branch rated phase current in amperes.

GI,BI

Complex admittance of the line shunt at the bus 'I' end of the branch; entered in
pu. BI is negative for a line connected reactor and positive for line connected
capacitor. GI + jBI = 0.0 by default.

GJ,BJ

Complex admittance of the line shunt at the bus 'J' end of the branch; entered in
pu. BJ is negative for a line connected reactor nd positive for line connected capacitor. GJ + jBJ = 0.0 by default.

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Initial branch status where 1 designates in-service and 0 designates out-of-service.
ST = 1 by default.

LEN

Line length; entered in user-selected units. LEN = 0.0 by default.

Owner number; (1 through the maximum number of owners at the current size
level: see Table 1-1). Each branch may have up to four owners. By default, 01 is
the owner to which bus 'I' is assigned and 02, 03, and 04 are zero.

When specifying a nontransformer branch between buses 'I' and 'J' with circuit identifier CKT, if a
two-winding transformer between buses 'I' and 'J' with a circuit identifier of CKT is already present
in the working case, it is replaced (i.e., the transformer is deleted from the working case and the
newly specified branch is then added to the working case).
Branches to be modeled as transformers are not specified in this data category; rather, they
are specified in the transformer data category described in the following Section 3.2.6.

Nontransformer branch data input to the Power Flow Raw Data File is terminated with a record
specifying a 'from bus' number of zero.

3.2.5.1 Zero Impedance Lines
PSS/E provides for the treatment of bus ties, jumpers, and other low impedance branches as zero
impedance lines. For a branch to be treated as a zero impedance line, it must have the following
characteristics:
•
•

Its resistance must be zero.

Its magnitude of reactance must be less than or equal to the zero impedance line
threshold tolerance, THRSHZ.

•

It must not be a transformer.

There are points to be noted, and restrictions to be observed, in using zero impedance lines as discussed below.
During network solutions, buses connected by such lines are treated as the same bus, thus having
identical bus voltages. At the completion of each solution, the loadings on zero impedance lines are
determined.

When obtaining power flow solutions, zero impedance line flows, as calculated at the end of the
solution, are preserved with the power flow case and are available to the power flow solution procedures. Similarly, in unbalanced fault calculations, the positive, negative, and zero sequence
branch currents on zero impedance lines are determined and preserved, and are subsequently
available to be reported. In other applications such automatic contingency analysis, short-circuit
scanning and in linearized network analyses, zero impedance line results are calculated and
reported as needed.
The zero impedance line threshold tolerance, THRSHZ, may be changed by launching the Solution

Parameters dialog (see Figure 4-22) from the Power FIow>Solution>Parameters option under
the General tab. Setting THRSHZ to zero disables zero impedance line modeling, and all branches
are represented with their specified impedances.

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A zero impedance line may not have a transformer in parallel with it. Although not required, it is
recommended that no other in-service lines exist in parallel with a zero impedance line.
A zero impedance line may have nonzero values of line charging and/or line connected shunts. This
allows, for example, a low impedance cable to be modeled as a zero impedance line.

While more than two buses may be connected together by zero impedance lines, buses may not
be connected in a loop arrangement by zero impedance lines. For example, connecting bus 1 to
bus 2 and bus 2 to bus 3 by zero impedance lines is allowed; adding a third zero impedance line
connecting buses 1 and 3 would form a zero impedance line connected loop and is not allowed.
It is important to note that buses connected together by zero impedance lines are treated as a single

bus by the power flow solution activities. Hence, equipment controlling the voltages of multiple
buses within a zero impedance connected group of buses must have coordinated voltage
schedules.
With large databases it is important to have the ability to easily identify which bus voltages are being
regulated and which equipment is controlling the regulation. This helps to avoid situations in which

there are potential regulation conflicts. Clicking the Regulated buses tab in the Power
Flow>Reports>Limit checking reports... dialog, will facilitate generation of a report that tabulates
those buses whose voltages are controlled by generation, switched shunts, voltage controlling
transformers, FACTS devices, and/or VSC dc line converters.

Similarly, if multiple voltage controlling devices are present within a group of buses connected
together by zero impedance lines, the power flow solution activities handle the boundary condition
as if they are all connected to the same bus.
In the fault analysis activities, a branch treated as a zero impedance line in the positive sequence
is treated in the same manner in the zero sequence, regardless of its zero sequence branch impedance. Zero sequence mutual couplings involving a zero impedance line are ignored in the fault
analysis solution activities.

3.2.6 Transformer Data
Each ac transformer to be represented in PSS/E is introduced through transformer data record
blocks that specify all the data required to model transformers in power flow calculations, with one
exception.
That exception is a set of ancillary data, comprising transformer impedance correction tables, which
define the manner in which transformer impedance changes as off-nominal turns ratio or phase shift
angle is adjusted. Those data records are described in Section 3.2.12.

Both two-winding and three-winding transformers are specified in transformer data record blocks.
Two-winding transformers require a block of four data records. Three-winding transformers require
five data records.

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Transformer

The data records for the two-winding transformer are common to the three-winding transformer.
Figure 3-9 shows the transformer winding configurations.

Bus]

BusT

Bus]

BusT

Winding 2

Winding 1

winding

Figure 3-9. Two and Three-winding Transformer Configurations Related to Data Records
The five record transformer data block for three-winding transformers has the following format:
I,J,K,CKT,CW,CZ,CM,MAG1,MAG2,NMETR,'NAME',STAT,Ol,Fl
04,F4
R1—2,X1—2,SBASE1—2,R2—3,X2—3,SBASE2—3,R3—1,X3—1,SBASE3—1,VMSTAR,ANSTAR
WINDV1,NOMV1,ANG1, RATA1, BATB1, RATC1, COD1, CONT1, RMA1, RMI1,VMA1,VMI1,NTP1, TAB1, CR1, CX1
WINDV2 ,NOMV2 , ANG2 RATA2 BATB2 RATC2, COD2, CONT2 , RMA2 , RMI2 VMA2 , VMI2 ,NTP2, TAB2,CR2, CX2
WINDV3,NOMV3,ANG3, RATA3, BATB3, RATC3, COD3, CONT3, RMA3, RMI3,VMA3,VMI3,NTP3, TAB3, CR3, CX3
,

The four-record transformer data block for two-winding transformers is a subset of the data

required for three-winding transformers and has the following format:
I,J,K,CKT,CW,CZ,CM,MAG1,MAG2,NMETR,'NAME',STAT,Ol,Fl
R1—2 , X1—2,

04,F4

SBASE1—2

WINDV1,NOMV1,ANG1, RATA1, BATB1, RATC1, COD1, CONT1, RMA1, RMI1,VMA1,VMI1,NTP1, TAB1, CR1, Cxl
WINDV2 , NOMV2

The three-winding transformer model in PSSIE is in fact a grouping of three two-winding trans-

formers models where each of these two-winding transformers models one of the windings. While
most of the three-winding transformer data is stored in the two-winding transformer data arrays, it
is accessible for reporting and modification only as three-winding transformer data.

Record I
I,J,K,CKT,CW,CZ,CN,MAG1,MAG2,NMETR,'NAME',STAT,Ol,Fl, - .,04,F4
-

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The bus number, or extended bus name enclosed in single quotes, of the bus to
which the first winding is connected. The transformer's magnetizing admittance is
modeled on winding one. The first winding is the only winding of a two-winding
transformer whose tap ratio or phase shift angle may be adjusted by the power flow
solution activities; any winding(s) of a three-winding transformer may be adjusted.
No default is allowed.

The bus number, or extended bus name enclosed in single quotes, of the bus to
which the second winding is connected. This winding may have a fixed, off-nominal
tap ratio assigned to it. No default is allowed for 'J'.

The bus number, or extended bus name enclosed in single quotes, of the bus to
which the third winding is connected. Zero is used to indicate that no third winding
is present (i.e., that a two-winding rather than a three-winding transformer is being
specified). This winding may have a fixed, off-nominal tap ratio assigned to it. K =
0 by default.

CKT

One- or two-character uppercase nonblank alphanumeric transformer circuit iden-

tifier; the first character of CKT must not be an ampersand ('&'); see
Section 3.4.4.12. CKT = '1' by default.
CW

The winding data I/O code which defines the units in which the turns ratios
WINDV1, WINDV2 and WINDV3 are specified (the units of RMAi and RMIi are also

governed by CW when ICODiI is 1 or 2): 1 for off-nominal turns ratio in pu of
winding bus base voltage; 2 for winding voltage in kV. CW = 1 by default.
CZ

The impedance data I/O code that defines the units in which the winding impedances R1-2, X1-2, R2-3, X2-3, R3-1 and X3-1 are specified: 1 for resistance and
reactance in pu on system base quantities; 2 for resistance and reactance in pu on
a specified base MVA and winding bus base voltage; 3 for transformer load loss in
watts and impedance magnitude in pu on a specified base MVA and winding bus
base voltage. CZ = 1 by default.

The magnetizing admittance I/O code that defines the units in which MAG1 and
MAG2 are specified: 1 for complex admittance in pu on system base quantities; 2
for no load loss in watts and exciting current in pu on winding one to two base MVA
and nominal voltage. CM = 1 by default.

MAG1, MAG2 The magnetizing conductance and susceptance, respectively, in pu on system
base quantities when CM is 1; MAG1 is the no load loss in watts and MAG2 is the
exciting current in pu on winding one to two base MVA (SBASE1-2) and nominal
voltage (NOMV1) when CM is 2. MAG1 = 0.0 and MAG2 = 0.0 by default.
NMETR

The nonmetered end code of either 1 (for the winding one bus) or 2 (for the winding
two bus). In addition, for a three-winding transformer, 3 (for the winding three bus)
is a valid specification of NMETR. NMETR = 2 by default.

NAME

An alphanumeric identifier assigned to the transformer. The name may be up to
twelve characters and must be enclosed in single quotes. NAME may contain any
combination of blanks, uppercase letters, numbers and special characters. NAME
is twelve blanks by default.

STAT

The initial transformer status, where 1 designates in-service and 0 designates out-

of-service. In addition, for a three-winding transformer, 2 designates that only

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winding two is out-of-service, 3 indicates that only winding three is out-of-service,
and 4 indicates that only winding one is out-of-service, with the remaining windings
in-service. STAT = 1 by default.
Oi

An owner number; (1 through the maximum number of owners at the current size
level: see Table 1-1). Each transformer may have up to four owners. By default, 01
is the owner to which bus 'I' is assigned and 02, 03, and 04 are zero.

The fraction of total ownership assigned to owner Oi; each Fi must be positive. The
Fi values are normalized such that they sum to 1.0 before they are placed in the
working case. By default, each Fi is 1.0.

Record 2
The first three data items described on the second record are used for both two- and three-winding
transformers; the remaining data items are used only for three-winding transformers:
R1—2 , X1—2, SBASE1—2, R2—3, X2—3, SBASE2—3, R3—1, X3—1, SBASE3—1, VMSTAR,

ANS TAR

X1-2

The measured impedance of the transformer between the buses to which its first
and second windings are connected. When CZ is 1, they are the resistance and
reactance, respectively, in pu on system base quantities; when CZ is 2, they are
the resistance and reactance, respectively, in pu on winding one to two base MVA
(SBASE1-2) and winding one bus base voltage; when CZ is 3, R1-2 is the load loss
in watts, and X1-2 is the impedance magnitude in pu on winding one to two base
MVA (SBASE1-2) and winding one bus base voltage. R1-2 = 0.0 by default, but no
default is allowed for X1-2.

SBASE1-2

The winding one to two base MVA of the transformer. SBASE1-2 = SBASE (the
system base MVA) by default.

R2-3, X2-3

The measured impedance of a three-winding transformer between the buses to
which its second and third windings are connected; ignored for a two-winding transformer. When CZ is 1, they are the resistance and reactance, respectively, in pu
on system base quantities; when CZ is 2, they are the resistance and reactance,
respectively, in pu on winding two to three base MVA (SBASE2-3) and winding two
bus base voltage; when CZ is 3, R2-3 is the load loss in watts, and X2-3 is the
impedance magnitude in pu on winding two to three base MVA (SBASE2-3) and
winding two bus base voltage. R2-3 = 0.0 by default, but no default is allowed for

R1-2,

X2-3.

SBASE2-3

The winding two to three base MVA of a three-winding transformer; ignored for a
two-winding transformer. SBASE2-3 = SBASE (the system base MVA) by default.

R3-1, X3-1

The measured impedance of a three-winding transformer between the buses to
which its third and first windings are connected; ignored for a two-winding transformer. When CZ is 1, they are the resistance and reactance, respectively, in pu
on system base quantities; when CZ is 2, they are the resistance and reactance,
respectively, in pu on winding three to one base MVA (SBASE3-1) and winding
three bus base voltage; when CZ is 3, R3-1 is the load loss in watts, and X3-1 is
the impedance magnitude in pu on winding three to one base MVA (SBASE3-1)
and winding three bus base voltage. R3-1 = 0.0 by default, but no default is allowed
for X3-1.

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SBASE3-1

The winding three to one base MVA of a three-winding transformer; ignored for a
two-winding transformer. SBASE3-1 = SBASE (the system base MVA) by default.

VMSTAR

The voltage magnitude at the hidden star point bus; entered in pu. VMSTAR = 1.0
by default.

ANSTAR

The bus voltage phase angle at the hidden star point bus; entered in degrees.
ANSTAR = 0.0 by default.

Record 3
All data items on the third record are processed for both two- and three-winding transformers.
WINDV1, NOMV1, ANG1, RATA1, RATB1, RATC1, COD1, CONT1, RMA1, RMI1, VMA1,

VMI1,NTP1, TAB1,
WIN DV1

CR1, CX1

The winding one off-nominal turns ratio in pu of winding one bus base voltage when

CW is 1; WINDV1 = 1.0 by default. WINDV1 is the actual winding one voltage in
kV when CW is 2; WINDV1 is equal to the base voltage of bus 'I' by default.
NOMV1

The nominal (rated) winding one voltage in kV, or zero to indicate that nominal
winding one voltage is to be taken as the base voltage of bus 'I'. NOMV1 is used
only in converting magnetizing data between per unit admittance values and physical units when CM is 2. NOMV1 = 0.0 by default.

ANG1

The winding one phase shift angle in degrees. ANG1 is positive for a positive
phase shift from the winding one side to the winding two side (for a two-winding
transformer), or from the winding one side to the 'T' (or star) point bus (for a threewinding transformer). ANG1 must be greater than -180.0 and less than or equal to
+1 80.0. ANG1 = 0.0 by default.

RATA1,
RATB1,
RATC1

The first winding's three ratings entered in MVA (not current expressed in MVA).
RATA1 = 0.0, RATB1 = 0.0 and RATC1 = 0.0 (bypass flow limit check for this
transformer winding) by default.

COD1

The transformer control mode for automatic adjustments of the winding one tap or
phase shift angle during power flow solutions: 0 for no control (fixed tap and phase
shift); ±1 for voltage control; ±2 for reactive power flow control; ±3 for active power
flow control; ±4 for control of a dc line quantity (±4 is valid only for two-winding

transformers). If the control mode is entered as a positive number, automatic
adjustment of this transformer winding is enabled when the corresponding adjustment is activated during power flow solutions; a negative control mode suppresses
the automatic adjustment of this transformer winding. COD1 = 0 by default.
CONT1

The bus number, or extended bus name enclosed in single quotes, of the bus
whose voltage is to be controlled by the transformer turns ratio adjustment option
of the power flow solution activities when COD1 is 1. CONT1 should be nonzero
only for voltage controlling transformer windings.
CONT1 may specify a bus other than 'I', 'J', or 'K'; in this case, the sign of CONT1

defines the location of the controlled bus relative to the transformer winding. If
CONT1 is entered as a positive number, or a quoted extended bus name, the ratio
is adjusted as if bus CONT1 is on the winding two or winding three side of the transformer; if CONT1 is entered as a negative number, or a quoted extended bus name

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with a minus sign preceding the first character, the ratio is adjusted as if bus
ICONT1 I is on the winding one side of the transformer. CONT1 = 0 by default.

RMA1, RMI1

VMA1, VMI1

The upper and lower limits, respectively, of either:
•

Off-nominal turns ratio in pu of winding one bus base voltage when ICOD1I is
1 or2 and CW is 1; RMA1 = 1.1 and RMI1 = 0.9 by default.

•

Actual winding one voltage in kV when ICOD1 I is 1 or 2 and CW is 2. No default
is allowed.

•

Phase shift angle in degrees when ICOD1 I is 3. No default is allowed.

•

Not used when ICOD1I is 0 or 4; RMA1 = 1.1 and RMI1 = 0.9 by default.

The upper and lower limits, respectively, of either:
•

Voltage at the controlled bus (bus ICONT1I) in pu when ICOD1I

VMA1 = 1.1 and VMI1 = 0.9 by default.
•

Reactive power flow into the transformer at the winding one bus end in Mvar
when ICOD1I is 2. No default is allowed.

•

Active power flow into the transformer at the winding one bus end in MW when
ICOD1I is 3. No default is allowed.

•

Not used when ICOD1I is 0 or 4; VMA1 = 1.1 and VMI1 = 0.9 by default.

NTP1

The number of tap positions available; used when COD1 is 1 or 2. NTP1 must be
between 2 and 9999. NTP1 = 33 by default.

TAB1

The number of a transformer impedance correction table

CR1, CX1

The load drop compensation impedance for voltage controlling transformers

if this transformer
winding's impedance is to be a function of either off-nominal turns ratio or phase
shift angle (see Section 3.4.4.7), or 0 if no transformer impedance correction is to
be applied to this transformer winding. TAB1 = 0 by default.

entered in pu on system base quantities; used when COOl is 1. CR1 + j CX1 = 0.0
by default.

Record 4
The first two data items on the fourth record are read for both two- and three-winding transformers;
the remaining data items are used only for three-winding transformers.
WINDV2, NOMV2, ANG2, RATA2, RATB2, RATC2, COD2, CONT2, RMA2, RMI2, VMA2,

VMI2, NTP2, TAB2, CR2, CX2
WINDV2

The winding two off-nominal turns ratio in pu of winding two bus base voltage when
CW is 1; WINDV2 = 1.0 by default. WINDV2 is the actual winding two voltage in kV
when CW is 2; WINDV2 is equal to the base voltage of bus 'J' by default.

NOMV2

The nominal (rated) winding two voltage in kV, or zero to indicate that nominal
winding two voltage is to be taken as the base voltage of bus "J'. NOMV2 is present
for information purposes only; it is not used in any of the calculations for modeling
the transformer. NOMV2 = 0.0 by default.

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ANG2

The winding two phase shift angle in degrees; ignored for a two-winding transformer. ANG2 is positive for a positive phase shift from the winding two side to the
'T' (or star) point bus. ANG2 must be greater than -180.0 and less than or equal to
+1 80.0. ANG2 = 0.0 by default.

RATA2,
RATB2,
RATC2

The second winding's three ratings entered in MVA (not current expressed
in MVA); ignored for a two-winding transformer. RATA2 = 0.0, RATB2 = 0.0 and
RATC2 = 0.0 (bypass flow limit check for this transformer winding) by default.

COD2

The transformer control mode for automatic adjustments of the winding two tap or
phase shift angle during power flow solutions: 0 for no control (fixed tap and phase
shift); ±1 for voltage control; ±2 for reactive power flow control; ±3 for active power
flow control. If the control mode is entered as a positive number, automatic adjustment of this transformer winding is enabled when the corresponding adjustment is
activated during power flow solutions; a negative control mode suppresses the
automatic adjustment of this transformer winding. COD2 = 0 by default.

CONT2

The bus number, or extended bus name enclosed in single quotes, of the bus
whose voltage is to be controlled by the transformer turns ratio adjustment option
of the power flow solution activities when COD2 is 1. CONT2 should be nonzero
only for voltage controlling transformer windings.

CONT2 may specify a bus other than 'I', 'J', or 'K'; in this case, the sign of CONT2

defines the location of the controlled bus relative to the transformer winding. If
CONT2 is entered as a positive number, or a quoted extended bus name, the ratio

is adjusted as if bus CONT2 is on the winding one or winding three side of the
transformer; if CONT2 is entered as a negative number, or a quoted extended bus
name with a minus sign preceding the first character, the ratio is adjusted as if bus
ICONT2I is on the winding two side of the transformer. CONT2 = 0 by default.
RMA2, RMI2

VMA2, VMI2

The upper and lower limits, respectively, of either:
•

Off-nominal turns ratio in pu of winding two bus base voltage when ICOD2I is
1 or 2 and CW is 1; RMA2 = 1.1 and RMI2 = 0.9 by default.

•

Actual winding two voltage in kV when ICOD2I is 1 or 2 and CW is 2. No default
is allowed.

•

Phase shift angle in degrees when ICOD2I is 3. No default is allowed.

•

Not used when ICOD2I is 0; RMA2 = 1 .1 and RMI2 = 0.9 by default.

The upper and lower limits, respectively, of either:
•

Voltage at the controlled bus (bus ICONT2I) in pu when ICOD2I

VMA2 = 1.1 and VMI2 = 0.9 by default.

NTP2

•

Reactive power flow into the transformer at the winding two bus end in Mvar
when ICOD2I is 2. No default is allowed.

•

Active power flow into the transformer at the winding two bus end in MW when
ICOD2I is 3. No default is allowed.

•

Not used when ICOD2I isO; VMA2 = 1.1 and VMI2 = 0.9 by default.

The number of tap positions available; used when COD2 is 1 or 2. NTP2 must be
between 2 and 9999. NTP2 = 33 by default.

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TAB2

The number of a transformer impedance correction table

CR2, CX2

The load drop compensation impedance for voltage controlling transformers

entered in pu on system base quantities; used when COD2 is 1. CR2 + j CX2 = 0.0
by default.

Record 5
The fifth data record is specified only for three-winding transformers.
WINDV3, NOMV3, ANG3, RATA3,RATB3, RATC3, COD3, CONT3, RMA3, RMI3, VMA3,

VMI3,NTP3, TAB3, CR3, CX3
WINDV3

The winding three off-nominal turns ratio in pu of winding three bus base voltage
when CW is 1; WINDV3 = 1.0 by default. WINDV3 is the actual winding three
voltage in kV when CW is 2; WINDV3 is equal to the base voltage of bus K by
defau It.

NOMV3

The nominal (rated) winding three voltage in kV, or zero to indicate that nominal
winding three voltage is to be taken as the base voltage of bus K. NOMV3 is
present for information purposes only; it is not used in any of the calculations for
modeling the transformer. NOMV3 = 0.0 by default.

ANG3

The winding three phase shift angle in degrees. ANG3 is positive for a positive
phase shift from the winding three side to the 'T' (or star) point bus. ANG3 must
be greater than -180.0 and less than or equal to +180.0. ANG3 = 0.0 by default.

RATA3,
RATB3,
RATC3

The third winding's three ratings entered in MVA (not current expressed in MVA).
RATA3 = 0.0, RATB3 = 0.0 and RATC3 = 0.0 (bypass flow limit check for this
transformer winding) by default.

COD3

The transformer control mode for automatic adjustments of the winding three tap
or phase shift angle during power flow solutions: 0 for no control (fixed tap and
phase shift); ±1 for voltage control; ±2 for reactive power flow control; ±3 for active
power flow control. If the control mode is entered as a positive number, automatic
adjustment of this transformer winding is enabled when the corresponding adjustment is activated during power flow solutions; a negative control mode suppresses
the automatic adjustment of this transformer winding. COD3 = 0 by default.

CONT3

The bus number, or extended bus name enclosed in single quotes, of the bus
whose voltage is to be controlled by the transformer turns ratio adjustment option
of the power flow solution activities when COD3 is 1. CONT3 should be nonzero
only for voltage controlling transformer windings.

CONT3 may specify a bus other than 'I', 'J', or 'K'; in this case, the sign of CONT3

defines the location of the controlled bus relative to the transformer winding. If
CONT3 is entered as a positive number, or a quoted extended bus name, the ratio
is adjusted as if bus CONT3 is on the winding one or winding two side of the transformer; if CONT3 is entered as a negative number, or a quoted extended bus name

with a minus sign preceding the first character, the ratio is adjusted as if bus
ICONT3I is on the winding three side of the transformer. CONT3 = 0 by default.

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RMA3, RMI3

The upper and lower limits, respectively, of either:
•

Off-nominal turns ratio in pu of winding three bus base voltage when ICOD3I
is 1 or 2 and CW is 1; RMA3 = 1.1 and RMI3 = 0.9 by default.

•

Actual winding three voltage in kV when ICOD3I is 1 or 2 and CW is 2. No
default is allowed.

VMA3, VMI3

•

Phase shift angle in degrees when ICOD3I is 3. No default is allowed.

•

Not used when ICOD3I is 0; RMA3 = 1 .1 and RMI3 = 0.9 by default.

The upper and lower limits, respectively, of either:
•

Voltage at the controlled bus (bus ICONT3I) in pu when ICOD3I

VMA3 = 1.1 and VMI3 = 0.9 by default.
•

Reactive power flow into the transformer at the winding three bus end in Mvar
when ICOD3I is 2. No default is allowed.

•

Active power flow into the transformer at the winding three bus end in MW
when ICOD3I is 3. No default is allowed.

•

Not used when ICOD3I isO; VMA3 = 1.1 and VMI3 = 0.9 by default.

NTP3

The number of tap positions available; used when COD3 is 1 or 2. NTP3 must be
between 2 and 9999. NTP3 = 33 by default.

TAB3

The number of a transformer impedance correction table

CR3, CX3

The load drop compensation impedance for voltage controlling transformers

entered in pu on system base quantities; used when COD3 is 1. CR3 + j CX3 = 0.0
by default.

Transformer input in Raw Data File format is terminated with a record specifying a winding
one bus number of zero.

Notes
•

When specifying a two-winding transformer between buses I and J with circuit identifier
CKT, if a nontransformer branch between buses I and J with a circuit identifier of CKT
is already present in the working case, it is replaced (i.e., the nontransformer branch is
deleted from the working case and the newly specified two-winding transformer is then
added to the working case).

•

In deriving winding impedances, for three-winding transformers, from the measured
impedance data input values, one winding with a small or negative impedance may
result. It is possible to specify a set of measured impedances which themselves do not
individually appear to challenge the precision limits of typical power system calculations, but which result in one winding impedance of nearly (or identically) 0.0. Such data
could result in precision difficulties, and hence inaccurate results, when processing the
system matrices in power flow and short circuit calculations.

•

Whenever a set of measured impedance results in a winding reactance which is identically 0.0, a warning message is printed by the three-winding transformer data input or
data changing function, and the winding's reactance is set to the zero impedance line

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threshold tolerance (or to 0.0001 Pu if the zero impedance line threshold tolerance itself

is 0.0). Whenever a set of measured impedances results in a winding impedance
whose magnitude is less than 0.00001 pu, a warning message is printed. As with all
warning and error messages produced during data input and data modification phases
of PSS/E, the user should resolve the cause of the message (e.g., was correct input
data specified?) and use engineering judgement to resolve modeling issues (e.g., is
this the best way to model this transformer or would some other modeling be more
appropriate?).

3.2.6.1 Example Transformer Data Records
Figure 3-10 shows the data records for 138/34.5 kV two-winding transformer and sample data for
clarification.

Example of 2-Winding Transformer:
Data Formats
3,

MAG2, NMETR,

CKT, CW,

STAT, alp Fl,

04, F4

R1-2, X1-2, SBASE1
WIN DV 1,NO MV 1,A N Cl ,RATA 1, RATB 1 ,RA1t 1,C OD ,C 0 NT, RM A, RM I ,VMA,VMI,NTP,

WINDV2, NOMV2

Data
615], 6151, 0, 'U, 1 1, t 0.01 0.0, 2, 'iWO-WINDINGS', 1, 5, 10
0.01 0.33, WOO

i.oi, on1 oc, 50.0,
1.0, 0.0

75.0, 1 6151, 1.11 0.9, 1225, 1.0, 33, 0, 0.0, 0.0

Bus

6150

6151

138kv

34.5kv

'Windinq 2

Non-adjustable tap

Winding 1 (Adjustable tap side)
Figure 3-10. Sample Data for Two-Winding Transformer

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Figure 3-11 shows the data records for a 345/138/13.8 kV three-winding transformer and sample
data.

Example of 3-Winding Transformer
Data Formats
I, ), K, CKT, LW, Cl, CM,

MAG2, NMETRJ 'NAME', STAT, 01, Fl, ..., 04, E4

R1-2, X1-2, SBASE1, R2-3, X2-3, SBASE2, R3-1, X3-1, SBASE3, VMSTAR,ANSTAR
WINDY 1,NOMV

1,RATA 1,RATB 1,RATC 1,COD,CONT,RMA,RMI,VMA,YMI,NTP,TAB,CR,CX

WINDV2, NOMV2, ANG2, RATA2,RATB2,RATC2
NOMV3, ANC3,

Data
3001,

30:0 '1', 1, i, 1, On, On, 2, 'THREEWINDING, 1, 5, 1.0

ICCO, 0001, 003, 100.0, O.C'Jl, 0.C35,
ICC, OD, 00,3W,
600, 0, 3Q31, 1.1, OS, 1.04, 1.0
1112, 00 OD3W, 40),
001 00, 50, 60, 75

Bus 3001
I

tap
onWindingi

.rrt

Adjustable

Bus 3002

I_-Fixedtap
onWinding2
I

'345kv
13.8kv

Figure

00
33, 0, 00, Ui)

on Winding 3
Bus 3000

3-11. Sample Data for Three-Winding Transformer

3.2.7 Areas and Zones
Areas are commonly used to designate sections of the network which represent control areas
between which there are scheduled flows. PSS/E facilitates the identification of both areas and
schedules. Alternatively, the network can be subdivided between utility companies or other subdivisions useful for specific analyses.

Designating buses to specific zones allows additional subdivision of the network to facilitate analyses and documentation but PSS/E provides no analytical facility to schedule interchange between
zones.
Although areas cannot overlap other areas and zones cannot overlap other zones, areas and zones
can overlap each other.

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Figure 3-12 shows a system subdivided into three areas and three zones, each with a unique name.
Notice the following:

An area does not have to be contiguous. Area #1 covers two separate parts of the
network.

Zone #1 lies entirely in Area #1.
Zone #2 lies partly in Area #1 and partly in Area #4.
Zone #3 lies partly in Area 4 and Area 2.

Figure 3-12. Overlapping Areas and Zones

3.2.8 Area Interchange Data
Area interchange is a required net export of power from, or net import of power to, a specific area.
This does not imply that the power is destined to be transferred to or from any other specific area.
To specify transfers between specific pairs of areas see Section 3.2.16.

Each bus in the PSS/E working case may be designated as residing in an interchange area, for purposes of both interchange control and selective output and other processing. When the interchange

control option is enabled during a power flow solution, each interchange area for which an area
slack bus is specified has the active power output of its area slack bus modified such that the
desired net interchange for the area falls within a desired band.

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Area identifiers and interchange control parameters are specified in area interchange data records
which have the following format:

ISW, PDES, PTOL,

'ARNAME'

where:
Area number, (1 through the maximum number of areas at the current size level:
see Table 1-1).

Bus number, or extended bus name enclosed in single quotes, of the area slack
bus for area interchange control. The bus must be a generator (type two) bus in the

18W

specified area. Any area containing a system swing bus (type three) must have
either that swing bus or a bus number of zero specified for its area slack bus
number. Any area with an area slack bus number of zero is considered a "floating
area' by the area interchange control option of the power flow solution activities.
SW = 0 by default.
PDES

Desired net interchange leaving the area (export); entered in MW. In the power flow
solution process there are two options for handling the interchange. One assumes
that the interchange is exported only on tie lines out of the area. The other assumes
that the interchange is a combination of flow on the tie lines plus any loads whose
area assignment is different from the bus to which it is connected. Thus the PDES
must be specified such that is consistent with these two options either of which will
be selected at initiation of the power flow solution. PDES = 0.0 by default.

PTOL

Interchange tolerance bandwidth; entered in MW. PTOL = 10.0 by default.

ARNAME

Alphanumeric identifier assigned to area I. The name may contain up to twelve
characters and must be enclosed in single quotes. ARNAME may be any combination of blanks, uppercase letters, numbers, and special characters. ARNAME is
set to twelve blanks by default.

Area interchange data input from the Power Flow Raw Data File is terminated with a record
specifying an area number of zero.

3.2.9 Two-terminal dc Line Data
The two-terminal dc transmission line model is used to simulate either a point-to-point system with
rectifier and inverter separated by a bipolar or mono-polar transmission system or a Back-to-Back
system where the rectifier and inverter are physically located at the same site and separated only
by a short bus-bar.

Rectifier

Inverter

The data requirements fall into three groups:
•

Control parameters and set-points

•

Converter transformers

•

The dc line characteristics

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The steady-state model comprising this data enables not only power flow analysis but also establishes the initial steady-state for dynamic analysis.

Data for each two-terminal dc transmission line are specified on three consecutive data records.
The three data records have the following formats.

Record I
The first of the three dc line data records defines the following line quantities and control
parameters:

I,MDC,RDC, SETVL,VSCHD,VCMOD,RCOMP, DELTI,METER, DCVMIN,CCCITMX,
CC CAC C

The dc line number.

MDC

Control mode: 0 for blocked, 1 for power, 2 for current. MDC = 0 by default.

RDC

The dc line resistance; entered in ohms. No default allowed.

SETVL

Current (amps) or power (MW) demand. When MDC is one, a positive value of
SETVL specifies desired power at the rectifier and a negative value specifies
desired inverter power. No default allowed.

VSCHD

Scheduled compounded dc voltage; entered in kV. No default allowed.

VCMOD

Mode switch dc voltage; entered in kV. When the inverter dc voltage falls below this
value and the line is in power control mode (i.e., MDC = 1), the line switches to cur-

rent control mode with a desired current corresponding to the desired power at
scheduled dc voltage. VCMOD = 0.0 by default.
RCOMP

Compounding resistance; entered in ohms. Gamma and/or TAPI is used to attempt
to hold the compounded voltage (VDCI + DCCUR*RCOMP) at VSCHD. To control
the inverter end dc voltage VDCI, set RCOMP to zero; to control the rectifier end

dc voltage VDCR, set RCOMP to the dc line resistance, RDC; otherwise, set
RCOMP to the appropriate fraction of RDC. RCOMP = 0.0 by default.
DELTI

METER

Margin entered in per unit of desired dc power or current. This is the fraction by
which the order is reduced when ALPHA is at its minimum and the inverter is controlling the line current. DELTI = 0.0 by default.

Metered end code of either 'R' (for rectifier) or 'I' (for inverter). METER = 'I' by
defau It.

DCVMIN

Minimum compounded dc voltage; entered in kV. Only used in constant gamma
operation (i.e., when GAMMX = GAMMN) when TAPI is held constant and an ac
transformer tap is adjusted to control dc voltage (i.e., when Fl, TI, and Dl specify
a two-winding transformer). DCVMIN = 0.0 by default.

CCCITMX

Iteration limit for capacitor commutated two-terminal dc line Newton solution procedure. CCCITMX = 20 by default.

CCCACC

Acceleration factor for capacitor commutated two-terminal dc line Newton solution
procedure. CCCACC = 1.0 by default.

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Record 2
The second of the three dc line data records defines rectifier end data quantities and control
parameters:

IPR, NBR,ALFMX,ALFMN, RCR, XCR, EBASR, TRR, TAPR, TMXR, TMNR, STPR, ICR, IFR,
ITR, IDR,XCAPR
IPR

Rectifier converter bus number, or extended bus name enclosed in single quotes.
No default allowed.

NBR

Number of bridges in series (rectifier). No default allowed.

ALFMX

Nominal maximum rectifier firing angle; entered in degrees. No default allowed.

ALFMN

Minimum steady-state rectifier firing angle; entered in degrees. No default allowed.

RCR

Rectifier commutating transformer resistance per bridge; entered in ohms. No
default allowed.

XCR

Rectifier commutating transformer reactance per bridge; entered in ohms. No
default allowed.

EBASR

Rectifier primary base ac voltage; entered in kV. No default allowed.

TRR

Rectifier transformer ratio. TRR = 1.0 by default.

TAPR

Rectifier tap setting. TAPR = 1.0 by default.

TMXR

Maximum rectifier tap setting. TMXR = 1 .5 by default.

TMNR

Minimum rectifier tap setting. TMNR = 0.51 by default.

STPR

Rectifier tap step; must be positive. STPR = 0.00625 by default.

ICR

Rectifier firing angle measuring bus number, or extended bus name enclosed in
single quotes. The firing angle and angle limits used inside the dc model are
adjusted by the difference between the phase angles at this bus and the ac/dc
interface (i.e., the converter bus, PR). ICR = 0 by default.

Winding one side "from bus" number, or extended bus name enclosed in single
quotes, of a two-winding transformer. IFR = 0 by default.

ITR

Winding two side "to bus' number, or extended bus name enclosed in single
quotes, of a two-winding transformer. ITR = 0 by default.

IDR

Circuit identifier; the branch described by IFR, ITR, and IDR must have been
entered as a two-winding transformer; an ac transformer may control at most only
one dc converter. IDR = 1 by default.

If no branch is specified, TAPR is adjusted to keep alpha within limits; otherwise,
TAPR is held fixed and this transformer's tap ratio is adjusted. The adjustment logic

assumes that the rectifier converter bus is on the winding two side of the transformer. The limits TMXR and TMNR specified here are used; except for the transformer control mode flag (COD of Section 3.2.6), the ac tap adjustment data is
ignored.

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XCAPR

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Commutating capacitor reactance magnitude per bridge; entered in ohms.
XCAPR = 0.0 by default.

Record 3
Data on the third of the three dc line data records contains the inverter quantities corresponding to
the rectifier quantities specified on the second record described above.
The significant difference is that the control angle ALFA for the rectifier is replaced by the control
angle GAMMA for the inverter.

IPI, NBI, GAMNX, GAMMN, RCI, XCI, EBASI, TRI, TAPI, TMXI, TMNI, STPI, Id, IFI,
ITI, IDI,XCAPI
Dc line converter buses, PR and Pt, may be type one, two, or three buses. Generators, loads, fixed
and switched shunt elements, other dc line converters, and FACTS device sending ends are permitted at converter buses.

When either XCAPR> 0.0 or XCAPI > 0.0, the two-terminal dc line is treated as capacitor commutated. Capacitor commutated two-terminal dc lines preclude the use of a remote ac transformer as
commutation transformer tap and remote commutation angle buses at either converter. Any data
provided in these fields are ignored for capacitor commutated two-terminal dc lines.
Further details on dc line modeling in power flow solutions are given in Section 4.3.5.
The dc line data input from a Power Flow Raw Data File is terminated with a record specifying
a dc line number of zero.

3.2.10 Voltage Source Converter dc Line Data
Each voltage source converter (VSC) dc line to be represented in PSS/E is introduced by a set of
three consecutive data records.

Converter 1

Converter 2

dc line data records defines line quantities and control parameters.

Record I
'NAME', MDC, RDC, 01, Fl,

04, F4

NAME

The non-blank alphanumeric identifier assigned to this VSC dc line. Each VSC dc
line must have a unique NAME. The name may be up to twelve characters and
must be enclosed in single quotes. NAME may contain any combination of blanks,
uppercase letters, numbers and special characters. No default allowed.

MDC

Control mode: 0 for out-of-service, 1 for in-service. MDC = 1 by default.

RDC

The dc line resistance entered in ohms. RDC must be positive. No default allowed.

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An owner number; (1 through the maximum number of owners at the current size
level: see Table 1-1). Each VSC dc line may have up to four owners. By default,
01 is 1, and 02, 03 and 04 are zero.

Records 2 and 3
The remaining two data records define the converter buses (converter 1 and converter 2), along
with their data quantities and control parameters.
IBUS,TYPE,MODE,DOCET,ACSET,ALOSS,BLOSS,MINOSS,SNAX,IMAX,PWF,NAXQ,
MINQ,
REMOT, RMPCT
IBUS

Converter bus number, or extended bus name enclosed in single quotes. No
default allowed.

TYPE

Code for the type of converter dc control: 0 for converter out-of-service, 1 for dc
voltage control, or 2 for MW control. When both converters are in-service, exactly
one converter of each VSC dc line must be TYPE 1. No default allowed.

MODE

Converter ac control mode: 1 for ac voltage control or 2 for fixed ac power factor.
MODE = 1 by default.

DCSET

Converter dc setpoint. For TYPE = 1, DCSET is the scheduled dc voltage on the
dc side of the converter bus; entered in kV. For TYPE = 2, DCSET is the power
demand, where a positive value specifies that the converter is feeding active power
into the ac network at bus IBUS, and a negative value specifies that the converter
is withdrawing active power from the ac network at bus IBUS; entered in MW. No
default allowed.

ACSET

Converter ac setpoint. For MODE = 1, ACSET is the regulated ac voltage setpoint;
entered in pu. For MODE = 2, ACSET is the power factor setpoint. ACSET = 1.0
by default.

Aloss, Bloss

Coefficients of the linear equation used to calculate converter losses:
loss = Aloss + ldc*Bloss

Abs5 is entered in kW.

is entered in kW/amp.

= 0.0 by default.

M1N1055

Minimum converter losses; entered in kW.

SMAX

Converter MVA rating; entered in MVA. SMAX = 0.0 to allow unlimited converter
MVA loading. SMAX = 0.0 by default.

IMAX

Converter ac current rating; entered in amps. IMAX = 0.0 to allow unlimited converter current loading. If a positive MAX is specified, the base voltage assigned to
bus IBUS must be positive. MAX = 0.0 by default.

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Power weighting factor fraction (0.0
PWF
1.0) used in reducing the active
power order and either the reactive power order (when MODE is 2) or the reactive
power limits (when MODE is 1) when the converter MVA or current rating is violated. When PWF is 0.0, only the active power is reduced; when PWF is 1.0, only
the reactive power is reduced; otherwise, a weighted reduction of both active and
reactive power is applied. PWF = 1.0 by default.

PWF

Reactive power upper limit; entered in Mvar. A positive value of reactive power indi-

MA)(Q

cates reactive power flowing into the ac network from the converter; a negative
value of reactive power indicates reactive power withdrawn from the ac network.
Not used if MODE = 2. MAXQ = 9999.0 by default.
MINQ

Reactive power lower limit; entered in Mvar. A positive value of reactive power indicates reactive power flowing into the ac network from the converter; a negative
value of reactive power indicates reactive power withdrawn from the ac network.
Not used if MODE = 2. MINQ = -9999.0 by default.

REMOT

Bus number, or extended bus name enclosed in single quotes, of a remote type 1
or 2 bus whose voltage is to be regulated by this converter to the value specified
by ACSET. If bus REMOT is other than a type 1 or 2 bus, bus BUS regulates its
own voltage to the value specified by ACSET. REMOT is entered as zero if the converter is to regulate its own voltage. Not used if MODE = 2. REMOT = 0 by default.

RMPCT

Percent of the total Mvar required to hold the voltage at the bus controlled by bus
IBUS that are to be contributed by this VSC; RMPCT must be positive. RMPCT is
needed only if REMOT specifies a valid remote bus and there is more than one
local or remote voltage controlling device (plant, switched shunt, FACTS device
shunt element, or VSC dc line converter) controlling the voltage at bus REMOT to
a setpoint, or REMOT is zero but bus IBUS is the controlled bus, local or remote,

of one or more other setpoint mode voltage controlling devices. Not used if
MODE = 2. RMPCT = 100.0 by default.

VSC dc line data input within a Power Flow Raw Data File is terminated with a record specifying a blank dc line name (' ')or a dc line name of '0' or zero.
Each VSC dc line converter bus:
•

must be a type one or two bus. Generators, loads, fixed and switched shunt elements,
other dc line converters, and FACTS device sending ends are permitted at converter
buses.

•

must not have the terminal end of a FACTS device connected to the same bus.

•

must not be connected by a zero impedance line to another bus which violates any of
the above restrictions.

In specifying reactive power limits for converters which control ac voltage (i.e., those with unequal
reactive power limits whose MODE is 1), the use of very narrow var limit bands is discouraged. The
Newton-Raphson based power flow solutions require that the difference between the controlling

equipments high and low reactive power limits be greater than 0.002 pu for all setpoint mode
voltage controlling equipment (0.2 Mvar on a 100 MVA system base). It is recommended that
voltage controlling VSC converters have Mvar ranges substantially wider than this minimum permissible range.

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For interchange and loss assignment purposes, the dc voltage controlling converter is assumed to
be the non-metered end of each VSC dc line. As with other network branches, losses are assigned
to the subsystem of the non-metered end, and flows at the metered ends are used in interchange
calculations.
Further details on dc line modeling in power flow solutions are given in Section 4.3.5.

3.2.11 Switched Shunt Data
It is possible to represent switched shunt devices, in the form of capacitors and/or reactors on a
network bus.

BUS 'I'

The switched shunt elements at a bus may consist entirely of blocks of shunt reactors (each B1 is a
negative quantity) or entirely of blocks of capacitor banks (each B1 is a positive quantity). Any bus
can have both switched capacitors and reactors.

Each network bus to be represented in PSS/E with switched shunt admittance devices must have
a switched shunt data record specified for it. The switched shunts are represented with up to eight

blocks of admittance, each one of which consists of up to nine steps of the specified block
admittance.

Each switched shunt data record has the following format:
I, MODSW, VSWHI, VSWLO, SWREM, RMPCT, 'RMIDNT', BINIT, N1, B1, N2,
- N8, B8

B2,

where:

Bus number, or extended bus name enclosed in single quotes.
MODSW

Control mode:
0 - fixed

1 - discrete adjustment, controlling voltage locally or at bus SWREM

2 - continuous adjustment, controlling voltage locally or at bus SWREM

3 - discrete adjustment, controlling reactive power output of the plant at bus
SWREM

4 - discrete adjustment, controlling reactive power output of the VSC dc line
converter at bus SWREM of the VSC dc line whose name is specified as RMIDNT

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5 - discrete adjustment, controlling admittance setting of the switched shunt at bus
SWREM
MODSW = 1 by default.
VSWHI

When MODSW is 1 or 2, the controlled voltage upper limit; entered in pu.
When MODSW is 3, 4 or 5, the controlled reactive power range upper limit; entered
in pu of the total reactive power range of the controlled voltage controlling device.

VSWHI is not used when MODSW isO. VSWHI = 1.0 by default.
VSWLO

When MODSW is 1 or 2, the controlled voltage lower limit; entered in pu.
When MODSW is 3, 4 or 5, the controlled reactive power range lower limit; entered
in pu of the total reactive power range of the controlled voltage controlling device.

VSWLO is not used when MODSW is 0. VSWLO = 1.0 by default.
SWREM

Bus number, or extended bus name enclosed in single quotes (see
Section 3.2.2.1), of the bus whose voltage or connected equipment reactive power
output is controlled by this switched shunt.

When MODSW is 1 or 2, SWREM is entered as 0 if the switched shunt is to regulate its own voltage; otherwise, SWREM specifies the remote type one or two bus
whose voltage is to be regulated by this switched shunt.
When MODSW is 3, SWREM specifies the type two or three bus whose plant reactive power output is to be regulated by this switched shunt. Set SWREM to "I' if the
switched shunt and the plant which it controls are connected to the same bus.

When MODSW is 4, SWREM specifies the converter bus of a VSC dc line whose

converter reactive power output is to be regulated by this switched shunt. Set
SWREM to 'I' if the switched shunt and the VSC dc line converter which it controls
are connected to the same bus.
When MODSW is 5, SWREM specifies the remote bus to which the switched shunt
whose admittance setting is to be regulated by this switched shunt is connected.

SWREM is not used when MODSW is 0. SWREM = 0 by default.
RMPCT

Percent of the total Mvar required to hold the voltage at the bus controlled by bus
I

that are to be contributed by this switched shunt; RMPCT must be positive.

RMPCT is needed only if SWREM specifies a valid remote bus and there is more
than one local or remote voltage controlling device (plant, switched shunt, FACTS

device shunt element, or VSC dc line converter) controlling the voltage at bus
SWREM to a setpoint, or SWREM is zero but bus is the controlled bus, local or
remote, of one or more other setpoint mode voltage controlling devices. Only used
if MODSW = 1 or 2. RMPCT = 100.0 by default.
RMIDNT

BINIT

When MODSW is 4, the name of the VSC dc line whose converter bus is specified
in SWREM. RMIDNT is not used for other values of MODSW. RMIDNT is a blank
name by default.

Initial switched shunt admittance; entered in Mvar at unity voltage. BINIT = 0.0 by
defau It.

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Number of steps for block i. The first zero value of N1 or B1 is interpreted as the end
of the switched shunt blocks for bus I. N1 = 0 by default.

Admittance increment for each of N1 steps in block i; entered in Mvar at unity

voltage. B1 = 0.0 by default.

Switched shunt data input from a Power Flow Raw Data File is terminated with a record speca bus number of zero.

The following notes apply to switched shunts:
•

BIN IT needs to be set to its actual solved case value only when the network, as entered

into the working case, is to be considered solved as read in, or when the device is to
be treated as fixed (i.e., MODSW is set to zero or switched shunts are to be locked
during power flow solutions).
•

The switched shunt elements at a bus may consist entirely of reactors (each B1 is a neg-

ative quantity) or entirely of capacitor banks (each B1 is a positive quantity). In these
cases, the shunt blocks are specified in the order in which they are switched on the bus.
•

If the switched shunt devices at a bus are a mixture of reactors and capacitors, the
reactor blocks are specified first in the order in which they are switched on, followed by
the capacitor blocks in the order in which they are switched on.

•

In specifying reactive power limits for setpoint mode voltage controlling switched shunts
(i.e., those with MODSW of 1 or 2), the use of a very narrow admittance range is discouraged. The Newton-Raphson based power flow solutions require that the difference
between the controlling equipments high and low reactive power limits be greater than
0.002 pu for all setpoint mode voltage controlling equipment (0.2 Mvar on a 100 MVA
system base). It is recommended that voltage controlling switched shunts have admittance ranges substantially wider than this minimum permissible range.

•

When MODSW is 3, 4 or 5, VSWLO and VSWHI define a restricted band of the controlled device's reactive power range. They are specified in pu of the total reactive
power range of the controlled device (i.e., the plant QMAX - QMIN when MODSW is 3,
MA)(Q - MINQ of a VSC dc line converter when MODSW is 4, and
when
MODSW is 5, where 'i' are those switched shunt blocks for which Bi is positive and "i'
are those for which Bi is negative). VSWLO must be greater than 0.0 and less than
VSWHI, and VSWHI must be less than 1.0. That is, the following relationship must be
honored:

0.0 T1. Each
F1 entered must be greater than zero. On each record, at least 2 pairs of values must be specified
and up to 11 may be entered. For a graphical view of a correction table, see Figure 3-14.
The T1 values for tables that are a function of tap ratio (rather than phase shift angle) are in units of
the controlling winding's off-nominal turns ratio in pu of the controlling winding's bus base voltage.

Although a transformer winding is assigned to an impedance correction table, each table may be
shared among many transformer windings. If the first 'T' in a table is less than 0.5 or the last 'T'
entered is greater than 1.5, 'T' is assumed to be the phase shift angle and the impedance of each
transformer winding assigned to the table is treated as a function of phase shift angle. Otherwise,
the impedances of the transformer windings assigned to the table are made sensitive to off-nominal
turns ratio.

The power flow case stores both a nominal and actual impedance for each transformer winding
impedance. The value of transformer impedance entered by the user is taken as the nominal value
of impedance. Each time the complex tap ratio of a transformer is changed, either automatically by
the power flow solution activities or manually by the user, and the transformer winding has been
assigned to an impedance correction table, actual transformer winding impedance is redetermined
if appropriate. First, the scaling factor is established from the appropriate table by linear interpolation; then nominal impedance is multiplied by the scaling factor to determine actual impedance. An
appropriate message is printed any time the actual impedance is modified.
Transformer impedance correction data input from a Power Flow Raw Data File is terminated
with a record specifying a table number of zero.

Impedance
Scaling
Factor, F2
9
Li

Eleven-Point Curve

Turns Ratio, t, InPer Unit, Or

Phase Shift Angle, 0 in Degrees

Figure 3-14. Typical Impedance Correction Factor Curve

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3.2.13 Multi-Terminal dc Line Data
PSSIE allows the representation of up to 12 converter stations on one multi-terminal dc line. Further, the program allows the modelling of multi-terminal networks of up to 20 buses including the ac
convertor buses and the dc network buses.

Rectify

Inverti

Invert2

Each multi-terminal dc transmission line to be represented in PSS/E is introduced through a series
of data records. Each set of multi-terminal dc line data records begins with a record which defines
the number of converters, number of dc buses and dumber of dc links as well as related bus numbers and control mode.
Following this first record there are subsequent records for:
•

each converter

•

each dc bus

•

each dc link

Data Record I

NCONV, NDCBS, NDCLN, MDC, VCONV, VCMOD, VCONVN

where:

NCONV

Multi-terminal dc line number.

Number of ac converter station buses in multi-terminal dc line "I". No default
allowed.

NDCBS

Number of dc buses in multi-terminal dc line "I" (NCONV < NDCBS). No default
allowed.

NDCLN

Number of dc links in multi-terminal dc line "I". No default allowed.

MDC

Control mode
0 - blocked
1

2 -

power
current

MDC = 0 by default.

VCONV

Bus number, or extended bus name enclosed in single quotes, of the ac converter
station bus that controls dc voltage on the positive pole of multi-terminal dc line "I".
Bus VCONV must be a positive pole inverter. No default allowed.

VCMOD

Mode switch dc voltage; entered in kV. When any inverter dc voltage magnitude
falls below this value and the line is in power control mode (i.e., MDC = 1), the line
switches to current control mode with converter current setpoints corresponding to
their desired powers at scheduled dc voltage. VCMOD = 0.0 by default.

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VCONVN

Bus number, or extended bus name enclosed in single quotes, of the ac converter
station bus that controls dc voltage on the negative pole of multi-terminal dc line "I'.
If any negative pole converters are specified (see below), bus VCONVN must be a
negative pole inverter. If the negative pole is not being modeled, VCONVN must
be specified as zero. VCONVN = 0 by default.

Data Record 2
Data record 1 is followed by NCONV converter records of the following format:
IB,N,ANGMX,ANGMN,RC,XC,EBAS,TR,TAP,TPMX,TPMN,TSTP,SETVL,DCPF,MARG,
CNVCOD
where:

Ac converter bus number, or extended bus name enclosed in single quotes. No
default allowed.

Number of bridges in series. No default allowed.

ANGMX

Nominal maximum ALPHA or GAMMA angle; entered in degrees. No default
allowed.

ANGMN

Minimum steady-state ALPHA or GAMMA angle; entered in degrees. No default
allowed.

Commutating resistance per bridge; entered in ohms. No default allowed.

Commutating reactance per bridge; entered in ohms. No default allowed.

EBAS

Primary base ac voltage; entered in kV. No default allowed.

Actual transformer ratio. TR = 1 .0 by default.

TAP

Tap setting. TAP = 1.0 by default.

TPMX

Maximum tap setting. TPMX = 1.5 by default.

TPMN

Minimum tap setting. TPMN = 0.51 by default.

TSTP

Tap step; must be a positive number. TSTP = 0.00625 by default.

SETVL

Converter setpoint. When lB is equal to VCONV or VCONVN, SETVL specifies the

scheduled dc voltage magnitude, entered in kV, across the converter. For other
converter buses, SETVL contains the converter current (amps) or power (MW)
demand; a positive value of SETVL indicates that bus lB is a rectifier, and a negative value indicates an inverter. No default allowed.
DCPF

Converter participation factor. When the order at any rectifier in the multi-terminal
dc line is reduced, either to maximum current or margin, the orders at the remaining
converters on the same pole are modified according to their DCPFs to:
SETVL

+ (DCPF/SUN)*R

where SUM is the sum of the DCPFs at the unconstrained converters on the same
pole as the constrained rectifier, and R is the order reduction at the constrained
rectifier. DCPF = 1. by default.
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MARG

Rectifier margin entered in per unit of desired dc power or current. The converter
order reduced by this fraction, (1 .-MARG)*SETVL, defines the minimum order for
this rectifier. MARG is used only at rectifiers. MARG = 0.0 by default.

CNVCOD

Converter code. A positive value or zero must be entered if the converter is on the

positive pole of multi-terminal dc line 'I'. A negative value must be entered for
negative pole converters. CNVCOD = 1 by default.
Data Record 3
Following are NDCBS records, one for each dc bus, with the following format:
IDC, IB, IA, ZONE,

'NAME',

IDC2, RGRND, OWNER

where:

IDC

Dc bus number (1 to NDCBS). The dc buses are used internally within each multiterminal dc line and must be numbered 1 through NDCBS. No default allowed.

Ac converter bus number, or extended bus name enclosed in single quotes, or
zero. Each converter station bus specified in a converter record must be specified
as lB in exactly one dc bus record. Dc buses that are connected only to other dc
buses by dc links and not to any ac converter buses must have a zero specified for
lB. A dc bus specified as IDC2 on one or more other dc bus records must have a
zero specified for lB on its own dc bus record. lB = 0 by default.

Area number, (1 through the maximum number of areas at the current size level:
see Table 1-1). IA = 1 by default.

ZONE

Zone number, (1 through the maximum number of zones at the current size level:
see Table 1-1). ZONE = 1 by default.

NAME

Alphanumeric identifier assigned to dc bus DC. The name may be up to twelve
characters and must be enclosed in single quotes. NAME may contain any combination of blanks, uppercase letters, numbers, and special characters. NAME is
twelve blanks by default.

IDC2

Second dc bus to which converter lB is connected, or zero if the converter is connected directly to ground. For voltage controlling converters, this is the dc bus with

the lower dc voltage magnitude and SETVL specifies the voltage difference
between buses DC and IDC2. For rectifiers, dc buses should be specified such
that power flows from bus IDC2 to bus DC. For inverters, dc buses should be specified such that power flows from bus IDC to bus IDC2. IDC2 is ignored on those dc
bus records that have lB specified as zero. IDC2 = 0 by default.
RGRND

Resistance to ground at dc bus 'IDC'; entered in ohms. During solutions RGRND

is used only for those dc buses specified as IDC2 on other dc bus records.
RGRND = 0.0 by default.
OWNER

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Owner number, (1 through the maximum number of owners at the current size
level: see Table 1-1). OWNER = 1 by default.

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Data Record 4
Following the above records are NDCLN records, one for each dc link, with the following format:
IDC, JDC, DCCKT, RDC, LDC

where:
Branch "from bus" dc bus number.

JDC

Branch "to bus" dc bus number. JDC is entered as a negative number to designate
it as the metered end for area and zone interchange calculations. Otherwise, bus
"IDC" is assumed to be the metered end.

DCCKT

One-character uppercase alphanumeric branch circuit identifier. It is recommended that single circuit branches be designated as having the circuit identifier
'1'. DCCKT = '1' by default.

RDC

Dc link resistance, entered in ohms. No default allowed.

LDC

Dc link inductance, entered in mH. LDC is not used by the power flow solution
activities but is available to multi-terminal dc line dynamics models. LDC = 0.0 by
defau It.

Multi-terminal dc line data input from a Power Flow Raw Data File is terminated with a record
specifying a dc line number of zero.

A multi-terminal layout is shown in Figure 3-15. There are 4 convertors, 5 dc buses and 4 dc links.

AC Bus 2

DCBus2

DCBus 1

DC Bus 5

DC Bus 3

DC Bus 4

ACBus4

ACBus3
Figure 3-15. Multi-Terminal DC Network

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The following are notes on multi-terminal links:
•

Conventional two-terminal and multi-terminal dc lines are stored separately in PSS/E
working memory. Therefore, there may simultaneously exist, for example, a two-terminal dc line identified as dc line number 1 along with a multi-terminal line numbered 1.

•

Multi-terminal lines should have at least three converter terminals; conventional dc
lines consisting of two terminals should be modeled as two-terminal lines (See
Section 3.2.9).

•

Ac converter buses may be type one, two, or three buses. Generators, loads, fixed and
switched shunt elements, other dc line converters, and FACTS device sending ends
are permitted at converter buses.

•

Each multi-terminal dc line is treated as a subnetwork of dc buses and dc links connecting its ac converter buses. For each multi-terminal dc line, the dc buses must be
numbered 1 through NDCBS.

•

Each ac converter bus must be specified as lB on exactly one dc bus record; there may
be dc buses connected only to other dc buses by dc links but not to any ac converter
bus.

•

Ac converter bus 'tB' may be connected to a dc bus 'bC', which is connected directly
to ground. 'IB' is specified on the dc bus record for dc bus 'IDC'; the IDC2 field is specified as zero.

Alternatively, ac converter bus 'IB' may be connected to two dc buses 'IDC' and
"IDC2', the second of which is connected to ground through a specified resistance. 'IB"
and "IDC2' are specified on the dc bus record for dc bus 'IDC'; on the dc bus record
for bus 'IDC2', the ac converter bus and second dc bus fields (lB and IDC2, respectively) must be specified as zero and the grounding resistance is specified as RGRND.

•

The same dc bus may be specified as the second dc bus for more than one ac converter bus.

•

All dc buses within a multi-terminal dc line must be reachable from any other point
within the subnetwork.

•

The area number assigned to dc buses and the metered end designation of dc links
are used in calculating area interchange and assigning losses as well as in the inter-

change control option of the power flow solution activities. Similarly, the zone
assignment and metered end specification are used in Zonal reporting activities.
•

Further details on dc line modeling in power flow solutions are given in Section 4.3.5.

3.2.14 Multisection Line Grouping
Transmission lines commonly have a series of sections with varying physical structures. The sec-

tion might have different tower configurations, conductor types and bundles or various
combinations of these. The physical differences can result in the sections having different resistance, reactance and charging.

Bus I

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Bus I

Multisectia n

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A transmission line with several distinct sections can be represented as one multisection line group.

Each multisection line grouping to be represented in PSS/E is introduced by reading a multisection
line grouping data record. Each multisection line grouping data record has the following format:

I, J,

ID, DUM1, DUM2,

DUM9

where:
'From

bus" number, or extended bus name enclosed in single quotes.

'To bus" number, or extended bus name enclosed in single quotes. J is entered as
a negative number or with a minus sign before the first character of the extended
bus name to designate it as the metered end; otherwise, bus I is assumed to be the
metered end.

Two-character upper case alphanumeric multisection line grouping identifier. The
first character must be an ampersand ('&'). ID = '&l' by default.

DUM1

Bus numbers, or extended bus names enclosed in single quotes (see
Section 3.2.2.1), of the dummy buses connected by the branches that comprise
this multisection line grouping. No defaults allowed.

The DUM1 values on each record define the branches connecting bus 'I" to bus 'J', and are entered
so as to trace the path from bus "I' to bus "J'. Specifically, for a multisection line grouping consisting
of three line sections (and hence two dummy buses):

C3
I

The path from 'I' to 'J' is defined by the following branches:

From

Circuit

If this multisection line grouping is to be assigned the line identifier '&l', the corresponding multisection line grouping data record is given by:

Multisection line grouping data input from a Power Flow Raw Data File is terminated with a
record specifying a "from bus' number of zero.
The following notes apply to multisection line groups:
•

Up to 10 line sections (and hence 9 dummy buses) may be defined in each multisection
line grouping. A branch may be a line section of at most one multisection line grouping.

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•

Each dummy bus must have exactly two branches connected to it, both of which must
be members of the same multisection line grouping. A multisection line dummy bus
may not be a converter bus of a dc transmission line. A FACTS control device may not
be connected to a multisection line dummy bus.

•

The status of line sections and type codes of dummy buses are set such that the multisection line is treated as a single entity with regards to its service status.

•

When the multisection line reporting option is enabled, several power flow reporting
activities, specifically bus related reports, do not tabulate conditions at multisection line
dummy buses. Accordingly, care must be taken in interpreting power flow output
reports when dummy buses are other than passive nodes (e.g., if load or generation is
present at a dummy bus).

3.2.15 Zone Data
All buses (ac and dc) and loads can be assigned to reside in a zone of the network. To enable this
facility, each zone should be assigned a name and number. Specifically, the zone number is entered
as part of the data records for the buses and loads. The use of zones enables the user to develop

reports and to check results on the basis of zones and, consequently be highly specific when
reporting and interpreting analytical results.

Zone identifiers are specified in zone data records with the following format:

'ZONANE'

where:

Zone number, (1 through the maximum number of zones at the current size level:
see Table 1-1).
ZONAME

Alphanumeric identifier assigned to zone I. The name may contain up to twelve
characters and must be enclosed in single quotes. ZONAME may be any combination of blanks, uppercase letters, numbers, and special characters. ZONAME is
set to twelve blanks by default.

Zone data input from a Power Flow Raw Data File is terminated with a record specifying a
zone number of zero.

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3.2.16 Interarea Transfer Data
Using PSS/E, the user has the capability to identify in which area each bus or load resides (see
Sections 3.2.2 and 3.2.3). Further, the user can schedule active power transfers between pairs of
areas.

Scheduled active power transfers between pairs of areas are specified in interarea transfer data
records each of which has the following format:
ARFROM,

ARTO, TRID, PTRAN

where:
ARFROM

ARTO

'From area' number (1 through the maximum number of areas at the current size
level: see Table 1-1).

'To area' number (1 through the maximum number of areas at the current size
level: see Table 1-1).

TRIO

Single-character (0 through 9 or A through Z) upper case interarea transfer identifier used to distinguish among multiple transfers between areas ARFROM and
ARTO. TRID = '1' by default.

PTRAN

MW comprising this transfer. A positive PTRAN indicates that area ARFROM is
selling to area ARTO. PTRAN = 0.0 by default.

Following the completion of interarea transfer data input, PSS/E alarms any area for which at least
one interarea transfer is present and whose sum of transfers differs from its desired net interchange,
PDES (see Section 3.2.8 for the definition of PDES).

Interarea transfer data input from a Power Flow Raw Oata File is terminated with a record
specifying a "from area" number of zero.

3.2.17 Owner Data
PSS/E allows the user to identify which organization or utility actually owns a facility, a piece of
equipment or a load. Major network elements can have up to four different owners. This facilitates
interpretation of results and reporting of results on the basis of ownership.

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Owner identifiers are specified in owner data records with the following format:

'OWNANE'

where:

Owner number, (1 through the maximum number of owners at the current size
level: see Table 1-1).
OWNAME

Alphanumeric identifier assigned to owner I. The name may contain up to twelve
characters and must be enclosed in single quotes. OWNAME may be any combination of blanks, uppercase letters, numbers, and special characters. OWNAME is
set to twelve blanks by default.

Owner data input from a Power Flow Raw Data File is terminated with a record specifying an
owner number of zero.

3.2.18 FACTS Device Data
There is a multiplicity of Flexible AC Transmission System devices currently available comprising
shunt devices, such as the Static Compensator (STATCOM), series devices such as the Static Syn-

chronous Series Compensator (SSSC), combined devices such as the Unified Power Flow
Controller (UPFC) and the Interline Power Flow Controllers (IPFC), of which the latter are parallel
series devices.

Bus I

Bus J

PSS/E facilitates these devices with one generic set of data records.
Each FACTS device data record has the following format:
N,I,J,MODE,PDES,QDES,VSET,SHMX,TRMX,VTMN,VTMX,VSMX,IMX,LINX,RMPCT,
OWNER, SET1, SET2, VSREF

where:
N

FACTS device number.
Sending end bus number, or extended bus name enclosed in single quotes. No
default allowed.

3-46

Terminal end bus number, or extended bus name enclosed in single quotes; 0 for
a STATCON. J = 0 by default.

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MODE

Control mode:

0 - out-of-service (i.e., series and shunt links open).
1

- series and shunt links operating.

2 - series link bypassed (i.e., like a zero impedance line) and shunt link operating
as a STATCON.
3 - series and shunt links operating with series link at constant series impedance.

4 - series and shunt links operating with series link at constant series voltage.

5 - master device of an IPFC with P and Q setpoints specified; FACTS device
N+1 must be the slave device (i.e., its MODE is 6 or 8) of this IPFC.

6 - slave device of an IPFC with P and Q setpoints specified; FACTS device N-i
must be the master device (i.e., its MODE is 5 or 7) of this IPFC. The Q setpoint is
ignored as the master device dictates the active power exchanged between the two
devices.

7 - master device of an IPFC with constant series voltage setpoints specified;
FACTS device N+1 must be the slave device (i.e., its MODE is 6 or 8) of this IPFC.
8 - slave device of an I PFC with constant series voltage setpoints specified; FACTS

device N-i must be the master device (i.e., its MODE is 5 or 7) of this IPFC. The
complex Vd + iVq setpoint is modified during power flow solutions to reflect the
active power exchange determined by the master device.
If J is specified as 0, MODE must be either 0 or 1. MODE = i by default.
PDES

Desired active power flow arriving at the terminal end bus; entered in MW.
PDES = 0.0 by default.

QDES

Desired reactive power flow arriving at the terminal end bus; entered in MVAR.
QDES = 0.0 by default.

VSET

Voltage setpoint at the sending end bus; entered in pu. VSET = 1.0 by default.

SHMX

Maximum shunt current at the sending end bus; entered in MVA at unity voltage.
SHMX = 9999.0 by default.

TRMX

Maximum bridge active power transfer; entered in MW. TRMX = 9999.0 by default.

VTMN

Minimum voltage at the terminal end bus; entered in pu. VTMN = 0.9 by default.

VTMX

Maximum voltage at the terminal end bus; entered in pu. VTMX = 1 .1 by default.

VSMX

Maximum series voltage; entered in pu. VSMX = 1 .0 by default.

IMX

Maximum series current, or zero for no series current limit; entered in MVA at unity
voltage. IMX = 0.0 by default.

LINX

Reactance of the dummy series element used during model solution; entered in pu.
LINX = 0.05 by default.

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RMPCT

PSSIE-30.2
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Percent of the total Mvar required to hold the voltage at bus I that are to be contributed by the shunt element of this FACTS device; RMPCT must be positive. RMPCT
is needed only if there is more than one local or remote voltage controlling device

(plant, switched shunt, FACTS device shunt element, or VSC dc line converter)
controlling the voltage at bus Ito a setpoint. RMPCT = 100.0 by default.
OWNER

Owner number, (1 through the maximum number of owners at the current size
level: see Table 1-1). OWNER = 1 by default.

SET1,SET2

If MODE is 3, resistance and reactance respectively of the constant impedance,
entered in pu; if MODE is 4, the magnitude (in pu) and angle (in degrees) of the
constant series voltage with respect to the quantity indicated by VSREF; if MODE
is 7 or 8, the real (Vd) and imaginary (Vq) components (in pu) of the constant series
voltage with respect to the quantity indicated by VSREF; for other values of MODE,
SET1 and SET2 are read, but not saved or used during power flow solutions.
SET1 = 0.0 and SET2 = 0.0 by default.

VSREF

Series voltage reference code to indicate the series voltage reference of SET1 and

SET2 when MODE is 4, 7 or 8: 0 for sending end voltage, 1 for series current.
VSREF = 0 by default.
FACTS device data input from a Power Flow Raw Data File is terminated with a record specifying a FACTS device number of zero.
P55/Es FACTS device model contains a shunt element that is connected between the sending end
bus and ground, and a series element connected between the sending and terminal end buses.

A unified power flow controller (UPFC) has both the series and shunt elements active, and allows
for the exchange of active power between the two elements (i.e., TRMX is positive). A static series
synchronous condenser (SSSC) is modeled by setting both the maximum shunt current limit
(SHMX) and the maximum bridge active power transfer limit (TRMX) to zero (i.e., the shunt element
is disabled).
A static synchronous condenser (STATCON) or static compensator (STATCOM) is modeled by a
FACTS device for which the terminal end bus is specified as zero (i.e., the series element is
disabled).
An Interline Power Flow Controller (IPFC) is modeled by using two consecutively numbered series
FACTS devices. The first of this pair must be assigned as the IPFC master device by setting its control mode to 5 or 7, and the second must be assigned as its companion IPFC slave device by setting
its control mode to 6 or 8. In an IPFC, both devices have a series element but no shunt element.
Therefore, both devices typically have SHMX set to zero, and VSET of both devices is ignored.
Conditions at the master device define the active power exchange between the two devices.
Figure 3-16 shows the PSS/E FACTS control device model with its various setpoints and limits.
Each FACTS sending end bus must be a type 1 or 2 bus, and each terminal end bus must be a type

1 bus. Refer to Section 4.3.4 for other topological restrictions and for details on the handling of
FACTS devices during the power flow solution activities.

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—

Bus J

Bus I

VSMX

IMX

PDES

QDES

VTMX

VTM N

Cl)

TRMX

Figure 3-16. Basic FACTS Control Device Model

3.3 Importing Power Flow Data
Importing the Power Flow Raw Data File is facilitated by the FiIe>Open option shown in Figure 317 or more directly by clicking the Open toolbar button on the File toolbar.

Elle Edit

O New
Qpen,..

aower Flow

QPF

CtrI+N
CtrI+O

CtrI+S
Save As..

Compare...
File niormation (SIZE/SHOW/BUSN)...

Figure 3-17. File>Open Option

This option will give access to the Open dialog where the available .raw files will be listed in the
user's directory as shown in Figure 3-18. Clicking the Open button will initiate data import once the
required file has been selected. Prior to data import, the user will be given the option of using the
NAMES or NUMBERS option for importing data records. This selection will override the selection
made (see Section 1.8.9).

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