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1SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
MV MetalClad Switchgear
Still The BestMV Solution
Gary H. Fox, PEGE EnergySenior Specification Engineer
T 925 969 3608C 510 219 6868E [email protected]/design
2120 Diamond Blvd., Suite 100Concord, CA 94520General Electric Company
San Francisco IEEE / IAS Electrical Design and Applications Seminar
April 29,2011
2SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
SAFETY FEATURESDEAD FRONT CONSTRUCTION CLOSED DOOR RACKINGREMOTE BREAKER RACKING & CONTROL AVAILABLEPT & CPT ROLLOUT TRAYSBREAKERS CANNOT RACK IN/OUT IF CLOSEDCANNOT CLOSE BREAKERS IF NOT FULLY RACKED INSPRINGS DISCHARGE WHEN BREAKER IS MOVEDMECHANICALLY INTERLOCKED SHUTTERSGROUND & TEST DEVICES AVAILABLESAFE AUXILIARY SECONDARY FUSES ACCESSIBILITYEXTERNAL BREAKER POSITION INDICATORFULLY ISOLATED 2-HIGH CABLE COMPARTMENTS
3SF 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
6SF 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
7SF 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
8SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
VACUUM BREAKER CONSTRUCTION
CONTINUOUS CURRENT - 1200A thru 4000A (forced air)Modular Phase Interrupters - Simple ReplacementCopper Ground BarManual Trip/Close ButtonOperations CounterSpring Charge IndicatorRating Interference PlateWheels On Frame For MobilityContact Wear Indicator
Mechanism
Interrupter Assemblies
PrimaryDisconnects
FrontCover
SecondaryDisconnect
9SF IAS Electrical Design Seminar
April , 2011
Medium Voltage SwitchgearAll MetalClad meets Metal Enclosed, but Metal Enclosed gear does not meet MetalClad Requirements!
Metal Enclosed Switchgear (C37.20.3)Completely enclosedPrimary power circuit switching or interrupting devicesBusesConnectionsControl 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 barrieringShuttersAll live parts enclosed within grounded metal barriersInsulation-covered busAll compartments separated by metal barriers with no intentional openings.
10SF 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
11SF IAS Electrical Design Seminar
April , 2011
Medium Voltage SwitchgearSTANDARD 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
12SF IAS Electrical Design Seminar
April , 2011
Medium Voltage SwitchgearSWITCHGEAR 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 CompartmentCable Compartments
Breaker Compartments
13SF 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 Coated1/4” X 2” Ground Bus StandardPolyester-Glass Supports Standard,
Porcelain OptionalVinyl Boots With Nylon Hardware On JointsFully Isolated with 11-Gauge Steel
Riser Bus Main Horizontal Bus
Bus Boot
14SF IAS Electrical Design Seminar
April , 2011
Medium Voltage SwitchgearBREAKER/AUXILIARY COMPARTMENTSPolyester-Glass Primary Supports (std)Polyester-Glass or Steel Shutters,
Mechanically Interlocked With Racking Mechanism in Breaker CompartmentsMax of 4 CTs Per Phase, Per Breaker On
Primary SupportsPT/CPT, 4 Trays Per Section PT/CPT Primary Fuses are Inaccessible unless
Tray Is DisconnectedOpen / Close / Test Position IndicatorSecondary Disconnect Block
15SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
CABLE COMPARTMENT CONSTRUCTION
Provision For Cable, Bus Duct, Potheads or REBsNEMA Drilling For 2-750 MCM Per Phase With Space For Stress ConesSteel Isolation Trough For 2-High Breaker CablesFront to Rear Control Wire TroughMounting For Ground Sensor CT (GSCT) Arrestors, CPTS/CTS Surge Suppressors For Switching Transient Suppression on Feeders
16SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Enclosures
IndoorIndoor Drip-proofOutdoor, No AisleOutdoor Protected AisleOutdoor Common AisleIndoor provided in Equipment Power CenterSite Specific Seismic Withstand Levels: Ss, Sds
17SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Covers
Bolted rear covers with lifting handlesHinged rear coversProvisions for locks, rear and/or frontIR Scanning Ports on rear covers
18SF 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 differentPG&E requirementsMicroprocessor based relays require control power
(ac not a good choice)Supplied from ??? CPTs – Line or bus connectedThrowover contactors on multiple mainsIntegral branch panels not necessary
19SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Control Wire/ Terminations Options
Uninsulated spade, CT wiring with ring typeInsulated terminalsRing type for allOrigin/destination sleevesShort circuit type terminal blocks on CT
secondary
20SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Circuit Breaker
5 cycle std3 cycleCapacitor Switching dutyAuxiliary Contacts (MOC)Position Switch (TOC)Control voltage
21SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Copper Main Bus
Polyester bus supportsPorcelain supportsTin plated jointsSilver plated joints
22SF IAS Electrical Design Seminar
April , 2011
Medium Voltage Switchgear
Auxiliary Devices
Surge Arresters, Class, Rating or indicate system grounding method
Current Transformers, ratios and accuracyPotential TransformersProtective RelaysIndicating Lights: Incandescent, LEDInstrumentation & Power MeteringNetwork Gateways, SwitchesRemote Racking OperatorBreaker Test Cabinet (located external to switchgear)Ground and Test Device