..

1. 1
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
MV MetalClad Switchgear
Still The Best
MV Solution
Gary H. Fox, PE
GE Energy
Senior Specification Engineer
T 925 969 3608
C 510 219 6868
E gary.fox@ge.com
www.geindustrial.com/design
2120 Diamond Blvd., Suite 100
Concord, CA 94520
General Electric Company
San Francisco IEEE / IAS
Electrical Design and Applications Seminar
April 29,2011

2. 2
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
SAFETY FEATURES
DEAD FRONT CONSTRUCTION
CLOSED DOOR RACKING
REMOTE BREAKER RACKING & CONTROL AVAILABLE
PT & CPT ROLLOUT TRAYS
BREAKERS CANNOT RACK IN/OUT IF CLOSED
CANNOT CLOSE BREAKERS IF NOT FULLY RACKED IN
SPRINGS DISCHARGE WHEN BREAKER IS MOVED
MECHANICALLY INTERLOCKED SHUTTERS
GROUND & TEST DEVICES AVAILABLE
SAFE AUXILIARY SECONDARY FUSES ACCESSIBILITY
EXTERNAL BREAKER POSITION INDICATOR
FULLY ISOLATED 2-HIGH CABLE COMPARTMENTS

3. 3
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
MetalClad Switchgear & Breakers:
ANSI C37.04 - AC Power Circuit Breaker rating Structure
ANSI C37.06 - 1987 & 2000* - Preferred Ratings of Power Circuit Breakers
ANSI C37.09 - Test Procedures for Power Circuit breakers
ANSI C37.54 – Conformance Test Procedures
ANSI C37.010 – Application Guide for Power Circuit Breakers
ANSI C37.11 – Power Circuit Breaker Control Requirements
ANSI C37.20.2 – Standards for Switchgear Assemblies
NEMA SG-4 & 5 - Power Circuit Breakers & Switchgear Assemblies
Optional: UL & CSA Listing
*Why is there two years??
Codes & Standards

4. 4
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
ANSI C37.06-1987

5. 5
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
ANSI C37.06-2000

6. 6
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Voltage - 1.0 kV thru 15 kV Maximum
Nominal Voltage Classes
 4160V, 7200V, 13800V
Short Circuit Current Ratings:
Nominal MVA Classes
 4160-250MVA - 29KA (sym)
 4160-350MVA - 41KA
 4160-450MVA - 63KA*
 7200-500MVA - 33KA
 7200-785MVA - 63KA *
 13800-500MVA - 18KA
 13800-750MVA - 28KA
 13800-1000MVA - 37KA
 13800-1500MVA - 63KA*
Equipment & Breaker Ratings
Maximum KA Ratings (ANSI 2000)
 4760-31.5KA (sym)
 4760-40KA
 4760-50KA
 4760-63KA*
 8250-40KA
 8250-50KA*
 8250-63KA*
 15000-20KA
 15000-25KA
 15000-31.5KA
 15000-40KA
 15000-50KA
 15000-63KA
* Exceed ANSI Preferred Ratings

7. 7
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
•Vacuum interrupters first conceived in the
1920’s, manufacturing of Vacuum Breakers
began in 1961
•Vacuum breakers allowed 2-high drawout
designs beginning in 1976
•5 Cycle (std) & 3 Cycle (optional)
Interrupting Speed Capability
•Reduced & Easier Maintenance Than Other
Interrupting Designs, Such as SF6 & Air
Magnetic
Vacuum Interrupter

8. 8
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
VACUUM BREAKER CONSTRUCTION
CONTINUOUS CURRENT - 1200A thru 4000A
(forced air)
Modular Phase Interrupters - Simple
Replacement
Copper Ground Bar
Manual Trip/Close Button
Operations Counter
Spring Charge Indicator
Rating Interference Plate
Wheels On Frame For Mobility
Contact Wear Indicator
Mechanism
Interrupter Assemblies
Primary
Disconnects
Front
Cover
Secondary
Disconnect

9. 9
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
All MetalClad meets Metal Enclosed, but Metal Enclosed gear
does not meet MetalClad Requirements!
Metal Enclosed Switchgear
(C37.20.3)
Completely enclosed
Primary power circuit switching or
interrupting devices
Buses
Connections
Control and auxiliary devices.
Access provided by doors or
removable covers, or both.
Metalclad Switchgear
(C37.20.2)
Main switching and interrupting device
must be drawout.
Circuit breaker (usual) or a load-break
interrupter switch (unusual).
Extensive barriering
Shutters
All live parts enclosed within grounded
metal barriers
Insulation-covered bus
All compartments separated by metal
barriers with no intentional openings.

10. 10
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
And there’s more to C37.20.2!
Metal barrier in front of or part of switching device to ensure that no live
parts are exposed when the outer cover is opened while in the connected
position.
Mechanical interlocks provided for proper operating sequence
> Prevent movement while closed
> Prevent closing unless disconnects are fully engaged or at safe distance
> Prevent disconnection and access to primary fuses on CPT unless secondary open
> Stored energy mechanisms cannot be discharged unless fully charged
> Complete withdrawal not permitted until closing mechanism is blocked
> Automatic discharge of stored energy mechanism before or in process of removal
from housing
> Provisions for locking to prevent moving into Connected position

11. 11
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
STANDARD Construction & Dimensions
• Typical Indoor
Dimensions:
95” H
36” W
94” D
•36” Width
Sections for Indoor
and Outdoor
CTs GSCT
Cable
Trough
Surge
Suppressors
Main Bus
Breakers
Front
Of
Gear
Standard 2-High Sideview

12. 12
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
SWITCHGEAR CONSTRUCTION BASICS
 Separate Breaker, Bus, & Cable
Compartments, isolated with 11
gauge steel barriers.
 Bolted Steel Frame Construction,
with gusseted corners – very rigid,
stable
 NEMA 1 & 3R Construction
 Outdoor with or without aisle
 Closed Door Breaker Drawout
 11 Gauge Steel Doors, (2) 14 Gauge
Panels Between Sections
 All steel is either Zinc plated, or
painted. No bare metal.
Main Bus Compartment
Cable Compartments
Breaker Compartments

13. 13
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
SWITCHGEAR BUS BASICS
1200, 2000, 3000, 3500 & 4000* AMPS.
(* 4000A breaker section is fan cooled)
80KA Asym. Bracing, 130KA Peak, Std.
6” Copper Bus Bars
Full Tin Plate Standard, Silver Available.
Note Silver is used on all sliding contact
surfaces.
All Phase Bus Fluidized Bed Epoxy Coated
1/4” X 2” Ground Bus Standard
Polyester-Glass Supports Standard,
Porcelain Optional
Vinyl Boots With Nylon Hardware On Joints
Fully Isolated with 11-Gauge Steel
Riser Bus Main Horizontal Bus
Bus Boot

14. 14
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
BREAKER/AUXILIARY COMPARTMENTS
Polyester-Glass Primary Supports (std)
Polyester-Glass or Steel Shutters,
Mechanically Interlocked With Racking
Mechanism in Breaker Compartments
Max of 4 CTs Per Phase, Per Breaker On
Primary Supports
PT/CPT, 4 Trays Per Section
PT/CPT Primary Fuses are Inaccessible unless
Tray Is Disconnected
Open / Close / Test Position Indicator
Secondary Disconnect Block

15. 15
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
CABLE COMPARTMENT CONSTRUCTION
Provision For Cable, Bus Duct,
Potheads or REBs
NEMA Drilling For 2-750 MCM
Per Phase With Space For
Stress Cones
Steel Isolation Trough For 2-
High Breaker Cables
Front to Rear Control Wire
Trough
Mounting For Ground Sensor
CT (GSCT) Arrestors, CPTS/CTS
Surge Suppressors For
Switching Transient
Suppression on Feeders

16. 16
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Enclosures
Indoor
Indoor Drip-proof
Outdoor, No Aisle
Outdoor Protected Aisle
Outdoor Common Aisle
Indoor provided in Equipment Power Center
Site Specific Seismic Withstand Levels: Ss, Sds

17. 17
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Covers
Bolted rear covers with lifting handles
Hinged rear covers
Provisions for locks, rear and/or front
IR Scanning Ports on rear covers

18. 18
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Did YOU Notice that ALL MV breakers
are electrically operated ???????
Ac (120 V, 240 V) vs dc (48 V, 125 V)
Trip and close circuits can be different
PG&E requirements
Microprocessor based relays require control power
(ac not a good choice)
Supplied from ???
CPTs – Line or bus connected
Throwover contactors on multiple mains
Integral branch panels not necessary

19. 19
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Control Wire/ Terminations Options
Uninsulated spade, CT wiring with ring type
Insulated terminals
Ring type for all
Origin/destination sleeves
Short circuit type terminal blocks on CT
secondary

20. 20
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Circuit Breaker
5 cycle std
3 cycle
Capacitor Switching duty
Auxiliary Contacts (MOC)
Position Switch (TOC)
Control voltage

21. 21
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Copper Main Bus
Polyester bus supports
Porcelain supports
Tin plated joints
Silver plated joints

22. 22
SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Auxiliary Devices
Surge Arresters, Class,
Rating or indicate system grounding method
Current Transformers, ratios and accuracy
Potential Transformers
Protective Relays
Indicating Lights: Incandescent, LED
Instrumentation & Power Metering
Network Gateways, Switches
Remote Racking Operator
Breaker Test Cabinet (located external to switchgear)
Ground and Test Device