Paralleling Substation Breakers within the same Substation

DREMC training mediaRob Edde

Note:  This training to be preceded by LOTO training and Open/Close breaker training

OverviewOverview

• Reasons for parallelingReasons for paralleling• Review of one line diagrams

i f i hi d• Review of switching procedures• Alternate settings• Cold load pickup• Expected breaker loading while paralleledExpected breaker loading while paralleled• Split bus and multiple transformers w/ LTC

Why do we parallel?Why do we parallel?

It is the intent of DREMC to be able to ensureIt is the intent of DREMC to be able to ensure reliable power to customers even during “non normal” conditions Every DREMC ownednormal  conditions.  Every DREMC owned substation has the built in ability to take one breaker out of service on a temporary basisbreaker out of service on a temporary basis without interrupting customer service.

Reasons for paralleling loadReasons for paralleling load

• Maintenance

• RepairRepair

l• Failure

Events leading up to parallelingEvents leading up to paralleling

• Breaker MessagesBreaker Messages1. Spring Charge failure2 Trip Coil failure2. Trip Coil failure3. Relay fail (from bus relay message)4 F il/ l l4. Fail/slow close

• Broken bay switch• Broken insulator• Scheduled maintenance

!Before doing anything!!Before doing anything!

Ensure there are NOEnsure there are NO active hold or cautionactive hold or caution ordersorders.

Remote Enable/Disable( t ti ith 351R 351A & 351S l )(stations with 351R, 351A & 351S relays)

• When remote is enabled SCADA has the ability yto….

– Open breakerClose breaker– Close breaker

– Enable & Disable Ground– Enable & Disable Reclose– Change Settings Group

Wh i di bl d SCADA h h bili• When remote is disabled SCADA has the ability       to….

–Open Breaker–Open Breaker

Locate the proceduresLocate the procedures

All DREMC substations have procedures located C substat o s a e p ocedu es ocatedinside the control house.

Procedures should be located on the desktop

Stay familiarized with General Instructions, Normal Conditions, and any sections pertaining to Breakers.

Locate the one line diagram

Portion of one line needed for breaker parallelingp g

325

Switch designation

Voltage class

Bay number

Source switch

Voltage class

Bay number

Breaker

Voltage  Bay  Load  Voltage l

Bay b

Transfer i hclass number switch class number switch

Normal conditions

355

C. CLEARING A FEEDER BREAKER

( ) 1. Clearing Feeder Breakers 314, 324, 344 and 354.√

Complete switching procedure

NOTE: These instructions will be specific regarding switchboard and breaker devices but generic when discussing the breaker and air switch designations. By referring to the one line diagram the specific breaker and switch numbers should be added to the instructions prior to performing any switching.

( ) a. Remove reclosing function utilizing the “reclose enable” button (LED OFF) on breakers 3__4 and 3__4.1 3√

√

( ) b. Remove ground trip function utilizing the “ground enable” button (LED OFF) on breakers 3__4 and 3__4.

( ) c. Be sure that the combined load of breaker 3__4 and the breaker to be paralleled does not exceed 75 percent of the overcurrenttrip value of the breaker to be paralleled.

( ) d CLOSE transfer switch 3 9 of the breaker which is to be cleared

1 31

1

√√√( ) d. CLOSE transfer switch 3__9 of the breaker which is to be cleared.

( ) e. CLOSE transfer switch 3__9 of the breaker which is to be paralleled.

( ) f. OPEN the cleared breaker 3__4.

( ) g. OPEN source isolation switch 3 3 on the cleared breaker.

31

1√

√√√( ) g __

( ) h. OPEN load isolation switch 3__5 on the cleared breaker.

( ) i. Re-instate reclosing function utilizing the “reclose enable” button (LED ON) on the paralleled

breaker 3__4.

1

3

√√√√( ) j. Re-instate ground trip function utilizing the “ground enable”) button (LED ON) on the paralleled breaker 3__4.

THE CLEARED BREAKER CAN NOW HAVE MAINTENANCE AND TESTINGPERFORMED ON IT.

3√

Switching by __________________________________________Date/Time ___________________________________________

Leonardo Lineman3/5/10 13:25

Wh Di bl R l ?Why Disable Reclose?In case of emergency breaker will notIn case of emergency breaker will not 

reclose

3144

Why Disable Ground?Why Disable Ground?

• Single pole switching can cause imbalance

• Depending on source location along main bus, load can pass backwards though breakersp g

75% Rule

Remember: 75% rule applies for the 

314

324

320 amptrip

320 amptrip

duration of expected load

4 4

85

85

amps

5amp

ss

320 x .75 = 24085 + 85 = 170 Okay to parallel

120 + 135 = 255 Do not parallel

Close 319

355

Close 329

355

Note: At this stage, breakers may di i h b l

Load carried by both breakers

not coordinate with bus relay

Open 314

355

Load carried on 324 only

Isolate 314

355

Clearing an inoperative feeder g pbreaker

• Breaker is open and will not close•Customers on paralleled breaker will•Customers on paralleled breaker will 

be interruptedB d t b kt k if f lt i•Be prepared to backtrack if fault is 

found on faulty breaker circuit

314 open will not close314 open will not close

Customer  interrupted

Verify breaker open

I l t 314Isolate 314

Close 319

Open 324

Customersinterrupted openopen

Close 329

Close 324

Customer powerrestored via closed324

closed

Placing a cleared feeder breaker b k i iback in service

•Insure all switches in proper positionInsure all switches in proper position•Insure breaker to be put in service is 

openopen•Procedure is opposite of removing a 

feeder breaker from ser icefeeder breaker from service

When a feeder is closed and will not open……

• There is no written procedure for thisThere is no written procedure for this condition

• Proceed with the assistance of your supervisor• Proceed with the assistance of your supervisor• Be prepared to use a modified version of CLEARING A FEEDER BREAKERCLEARING A FEEDER BREAKER

• The emergency trip handle will be used to open the faulty breaker

Cold load pickup351S

• Cold load pickup can be used when a circuitCold load pickup can be used when a circuit has been out of service for a prolonged period of time in heavy loading conditionsof time in heavy loading conditions

• To initiate cold load pickup, (breaker must be open) depress the cold load pickup button toopen) depress the cold load pickup button to illuminate the cold load LEDAf h l f h b k ld l d i k• After the close of the breaker, cold load pickup is self extinguishing.

Alternate Settingsd351S and 351A

• Alternate settings are used to increase theAlternate settings are used to increase the load carrying capability of a feeder breaker

• Alternate settings should only be used under• Alternate settings should only be used under supervisor requestC b k b d ll• Care must be taken to not overburden small wire when using alternate settings

• Close attention to end customer voltage must be made when using alternate settings

Split bus and multiple power ftransformer stations

• In stations with multiple power transformersIn stations with multiple power transformers with LTC’s, breakers shall not be paralleled across the split busacross the split bus.

• East Shelbyville substation has a split main bus but not a split transfer bus Special care mustbut not a split transfer bus.  Special care mustbe taken not to parallel breakers across the two transformerstwo transformers.

The EndThe End

Version 1 February 2011DREMC Training CommitteegCommittee MembersChair: Patrick HannahDavid YoungTimmy TerryDeWayne CobaughLee PettesTroy CrowellJeff HockadayTimmy OrrellWally RutlandDoug Simpson