PA02100001E

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MSB–enhanced substation
primary and load interrupter
switchgear

Reduce the arc flash hazard in
your substation with Eaton’s MSB,
featuring the Arcflash Reduction
Maintenance System
Eaton’s MSB (metal-enclosed switch and breaker
combination) is an integrated assembly using reliable,
cost-effective load interrupter switches in series with
VCP-TR vacuum circuit breakers. MSB combines the reliable
visible disconnect of a load-break switch with the superior
protection capabilities of a fixed-mounted vacuum
circuit breaker.
MSB can be used as the primary protection for a
single-ended substation (eliminating the need for a
secondary main breaker), or it can be used as the
primary main device and integrated into a lineup of
fused MVS switchgear.
Arc flash hazard reduction
Safety is crucial and standards
like NFPA 70E (Standard
for Electrical Safety in the
Workplace) have emerged,
making it unacceptable for
engineers to accept existing or
to design new unit substations
without considering the impact
of arc flash hazards and secondary bus protection. Eaton’s MSB
delivers an elegantly simple
design approach. MSB offers
primary transformer protection
and secondary bus protection in
one 15 kV class primary metalenclosed assembly.

Arc Flash and PPE

These two articles in the Code
resulted in thousands of unit
substations being installed
using a fused load-break
switch as the secondary
bus protection!

For the past 30 to 40 years,
engineers have designed
secondary unit substations
based on application of a 15 kV
metal-enclosed fused load-break
switch, close coupled to a transformer primary, then in turn
connected to low voltage
switchgear at the transformer
secondary.
National Electrical Code (NEC)
requirements for this class
of equipment contained two
statements that resulted in quite
a few unit substations being
installed with very high levels
of available arcing energy
unprotected on the secondary
bus of the transformers.
Those two statements were:
1. Note 2 of NEC Article 450.3
Equipment—Transformers
describes the “six disconnect rule.” This article
states, “Where secondary
overcurrent protection is
required, the secondary
overcurrent device shall
be permitted to consist of
not more than six circuit
breakers or six sets of fuses
grouped in one location.”
2. NEC Article 240.21(C)2
Overcurrent Protection
describes transformer secondary conductors not over
10 ft (3m) long such that the
ampacity of the secondary
conductors is not less than
the combined calculated
loads on the circuits supplied
by the secondary conductors.

The emergence of new electrical safe workplace standards
such as the NFPA 70E–2009 has
challenged users to take another
look at their substations based
on the incident energy or arc
flash hazard should a secondary
bus fault occur. This could happen while doing energized work
such as racking a secondary
feeder circuit breaker on or off
of an energized bus.
NFPA 70E arc flash hazard
calculations conducted at one
industrial site yielded arc flash
energies in excess of 700
calories/centimeter2 at the
secondary bus as shown in
the substation diagram below.
Because personal protective
equipment (PPE) available at
the site was only rated up to
Category 4, 40 calories/
centimeter2, there was no safe
condition in which an operator
could insert or remove a feeder
circuit breaker from an energized
bus in order to perform lockout/
tagout safety procedures.

MSB is the solution to the
arc flash hazard dilemma
Reduce arc flash hazard in your
substation with Eaton’s MSB.
Solving this electrical safety
hazard involved replacement
of the existing metal-enclosed
fused load-break switch with an
Eaton metal-enclosed medium
voltage switch over vacuum
circuit breaker (MSB) assembly.
MSB is perfect for retrofit in
existing substations where arc
flash safety is an issue. And, the
MSB is perfect for application in
new substations.
With MSB, sensors can be
installed on the secondary bus
that are connected into the
primary vacuum circuit breaker.
MSB can effectively provide
primary substation transformer
protection as well as secondary
switchgear bus protection using
one device.

0
0

55.25
(1403.4)

MSB Side View

Two available methods for
reducing incident arcing
energy are:
•

Arcflash Reduction
Maintenance System mode

•

(ZSI) Zone selective interlocking; see diagram on page 3 for
ZSI example
MSB Front View

Vent

Vents
ØA
DANGER
HIGH
VOLTAGE

ØB

1500 kVA
5.75% Z

ØC

NAMEPLATE

VT

CPT

FDR
800A

MAIN
METERING

Potential arc flash hazard for
secondary switchgear bus
without MSB
Bus fault at 480V switchgear
•

10 kA secondary arcing fault

CT

•

At 13.8 kV = 348A primary fault

2000A

•

100E fuse clearing time = 160 seconds

FDR
800A

N

Fault at 480V switchgear bus
FDR
800A

FDR
800A

Typical unit substation with fused switch primary and no secondary main breaker

2

52.25
(1327.1)

The VCP-T main circuit breaker
can be equipped with multiple
user preferred methods for arc
energy reduction, drastically
reducing the arc flash energy on
the secondary bus for any unit
substation.

Vent

100E

105.45
(2678.4)

Barrier

Unit substation dilemma

EATON CORPORATION MSB–enhanced substation primary and load interrupter switchgear

•

NFPA 70E results

•

31.8 kA symmetrical fault current

•

1167-inch arc flash boundary

•

702.4 cal/cm at 18 inches

•

Unapproachable NFPA 70E–2009:
Category 4 is highest category
at 40 cal/cm

Reduced arc flash hazard with MSB
Bus fault at 480V switchgear

•

•

10 kA secondary arcing fault

•

At 13.8 kV = 348A primary fault

•

100E fuse clearing time = 160 seconds

Using MSB with integral trip unit
with ZSI or in Arcflash Reduction
Maintenance System mode
clears fault in three cycles or less
(arcing energy down to Category 2
per NFPA 70E)
From
15 kV Switchgear

To
Substation
1-3/C, #4/0 AWG
15 kV, EPR, MV-105,
133%, Tape Shield
Cable Tray

1-3/C, #4/0 AWG
15 kV, EPR, MV-105,
133%, Tape Shield
Cable Tray

Substation One-Line
Preferred Primary Protection
LV Substation

600A, 15 kV, 40 kA, Asymmetrical Interrupting
3-100:5 CT

Eaton MSB
Fused Load-Breaker
Switch with VCP-TR
Vacuum Breaker

MV
VCB
L,S,I
600AF
800AT

ZSI
50
51

2000/3000 kVA-12,470-480Y/277V
AA/FA (Cast Coil)
Z = 5.77%

0–5A
AM

FU1.0A
86
G

Alarm

59
G

(1) VT
(2.5:1)

FU1.0A

10:10
250 ȍ

3-3150:1 Current Sensors
3-3200:5 CT

Power
Metering

High Resistance Grounding
CPT
480V, 3200A Cu. Bus, 3-Phase, 3-Wire, 60 Hz, Isc. = 100 kA
2A

ZSI

GSCT

To
Transformer Fans

5 kVA
2C

2B

LV
PCB
L,S,I
800AF
800AT
AM

LV
PCB
L,S,I
800AF
800AT

ZSI

GSCT

4-3/C, #500 kcmil
600V, TC, XHHW-2,
with Ground
Cable Tray
100 Feet
LV MCC
DES-XXX

50
51
DT-3000 or
EDR-3000

ST 86
Note: 50/51 Integral Trip Includes Arms

2D

LV
PCB
L,S,I
800AF
800AT

ZSI

GSCT

AM

4-3/C, #500 kcmil
600V, TC, XHHW-2,
with Ground
Cable Tray
100 Feet

AM

LV
PCB
L,S,I
800AF
800AT

ZSI

GSCT

AM

4-3/C, #500 kcmil
600V, TC, XHHW-2,
with Ground
Cable Tray
100 Feet

LV MCC
DES-XXX

LV MCC
DES-XXX

4-3/C, #500 kcmil
600V, TC, XHHW-2,
with Ground
Cable Tray
100 Feet
LV MCC
DES-XXX

Diagram of substation using MSB with ZSI employed between the primary main breaker and the secondary feeder breakers
Product offering
•

Rated maximum voltage:
4.76 to 15 kV

•

Rated voltage withstand (BIL):
4.76 kV Class—60 kV peak;
15 kV Class—95 kV peak

•

•

•

•

Assembly main bus
continuous current: 1200A
Non-fused and fused switch:
refer to type MVS load
interrupter switchgear

Available configurations
•

Main with feeders

•

Maintenance tie breaker
with feeders

•

Main-main with feeders

•

Main-main automatic transfer

•

Maintenance tie breaker
automatic transfer

•

Main service disconnect

•

Switching and protection of
transformers, feeder circuits
and capacitor banks

Fuse types: current limiting
(CLE), expulsion (RBA)
Breaker types: VCP-TR, VCPTRL vacuum breakers, fixed

•

Unique features
•

Combination load-break
switch and medium voltage
vacuum circuit breaker

•

Door-mounted DT-3000 50/51
overcurrent protection with
integral current transformers

•

Capacitor switching
•

Integral 50/51 trip unit in
a VCP-T primary vacuum
breaker with special design
current sensors mounted at
the secondary bus. Special arc
flash reduction maintenance
setting to lower incident
energy while racking
secondary feeder breakers
Capability for ZSI connection
across all Eaton trip units at
both primary and secondary

•

Special design R-C snubber
network to ensure substation
transformer is protected from
switching transients

•

Arcflash Reduction
Maintenance System mode
available to temporarily
reduce the clearing time for
the VCP-T breaker during
downstream maintenance

Standards
•

IEEE C37.20.3

•

IEEE C37.04

•

IEEE C37.06

•

IEEE C37.09

•

CSA C22.2

EATON CORPORATION MSB–enhanced substation primary and load interrupter switchgear

3

Enhanced circuit breaker
protection
With the addition of VCP-TR/
VCP-TRL vacuum circuit
breakers, MSB is able to provide
enhanced system capabilities
as follows:
•

VCP-TRL breakers use a linear
actuator mechanism that is
capable of enduring 100,000
operations

•

High interrupting capacity suitable for use with ground fault
equipment and differential
relay schemes

•

Adjustable overcurrent
protection

•

Three-phase tripping,
eliminating single phasing

•

Eaton’s integrally mounted
self-powered 520MCV,
1150V trip units and FP-5000
protective relay offer
Arcflash Reduction
Maintenance System

Available vacuum breaker ratings
VCP-TR Breaker Ratings for Use with MSB (ANSI C37.04 UL-Recognized Component)
Identification

Rated Values
Insulation Level

Circuit
Breaker
Type 

Rated
Maximum
Voltage (V)

Power
Frequency

Impulse
Withstand

Continuous
Current

Short
Circuit
Breaking
Current 

Short
Circuit
Making
Current

kV rms

kV rms

kV Peak

Amperes

kA rms

kA Peak Operations

50 VCP-TR16

4.76

19

60

600, 1200

16

42

10,000

157, 159

50 VCP-TR20

4.76

19

60

600, 1200

20

52

—

163, 165

150 VCP-TR25

4.76

19

60

600, 1200

25

65

10,000

169, 171

150 VCP-TR16

15

36

95

600, 1200

16

42

10,000

159, 161

50 VCP-TR20

15

19

95

600, 1200

20

52

10,000

165, 167

150 VCP-TR25

15

36

95

600, 1200

25

65

10,000

171, 173

50 VCP-TR20

4.76

19

60

600, 1200

40

104

10,000

334, 334

150 VCP-TR25

15

36

95

600, 1200

40

104

10,000

338, 338

Mechanical
Endurance
C-O

Approx.
Weight
Lbs

 Independent shunt trips are available for use with traditional protective relaying schemes.
 Also two-second short time current rating.

VCP-TLR Breaker Ratings for Use with MSB (ANSI C37.04 and C37.09 UL-Recognized Components)
Identification

Rated Values
Insulation Level

Circuit
Breaker
Type 

Rated
Maximum
Voltage (V)

Power
Frequency

Impulse
Withstand

Continuous
Current

Short
Circuit
Breaking
Current 

Short
Circuit
Making
Current

Mechanical
Endurance
C-O 

Approx.
Weight

kV rms

kV rms

kV Peak

Amperes

kA rms

kA Peak Operations

50 VCP-TR16

4.76

19

60

600, 1200

16

42

100,000

Lbs

153, 155

50 VCP-TR20

4.76

19

60

600, 1200

20

52

—

159, 161

150 VCP-TR25

4.76

19

60

600, 1200

25

65

100,000

166, 168

150 VCP-TR16

15

36

95

600, 1200

16

42

100,000

156, 157

50 VCP-TR20

15

36

95

600, 1200

20

52

100,000

161, 163

150 VCP-TR25

15

36

95

600, 1200

25

65

100,000

168, 170

 Independent shunt trips are available for use with traditional protective relaying schemes.
 Also two-second short time current rating.
 Operating mechanism up to 100,000 operations, vacuum interrupter 30,000.

Optional VCP-TRL Breakers with Capacitors Switching Capabilities
Circuit Breaker
Type

Single
Bank

Back-toBack

Cable
Charging

Optional “C” type versions
available in rating shown
in above rating table

250A
and
1000A

250A
and
630A

25A

Eaton Corporation
Electrical Sector
1111 Superior Ave.
Cleveland, OH 44114
United States
877-ETN-CARE (877-386-2273)
Eaton.com
© 2010 Eaton Corporation
All Rights Reserved
Printed in USA
Publication No. PA02100001E / Z9564
February 2010

PowerChain Management is a registered
trademark of Eaton Corporation.
All other trademarks are property of their
respective owners.



---

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Create Date                     : 2010:02:03 12:24:00-05:00
Modify Date                     : 2010:02:04 14:08:27-05:00
Subject                         : MSB-enhanced substation primary and load interrupter switchgear
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Title                           : PA02100001E
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Description                     : MSB-enhanced substation primary and load interrupter switchgear
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