transmission duong pardo & elmore 500kv bf protection

8/12/2019 Transmission Duong Pardo & Elmore 500kV BF Protection

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500kV IPT

Breaker Failure Protection65 th Annual TAMU Protective Relay Conference

April 2 nd , 2012

Vinh Duong, P. E., PMP ABBJorge L. Pardo, P. E. Progress Energy

John Elmore Power Grid Eng.


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Road Map for the Paper

Introduction Who We Are, What We DoExisting System ConfigurationBrief Overview of Breaker Failure Protection

Need for ImprovementNew Application ConceptConclusions, Where We Go Next

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Who We Are, What We Do3

Progress Energy (March 2012)Utility company head quartered in Raleigh, NCListed in NYSE: PGNTwo operating entities: The Carolinas (PEC) and Florida (PEF)Serves 3.1 millions electric customers22,000 MW of regulated electric generating capacity


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PEF System Configuration

4700 miles of transmission lines including 69kV,115kV, 230kV and 500kVOne nuclear generating site of 860 MW in westernFlorida Additional 13,000 MW from coal, combustion, andoil plants throughout the territory

Five 500kV-230kV substation sites

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500kV Transmission Syst. Protection5

Transmission Lines: Three redundant high-speedpilot schemes Communication means including self-healing multiplexor over

fiber optic network, power line carrier and micro-wave Autotransformers and Substation Buses: Dual

redundant protection packages A dedicated breaker failure protection package

(separate from other relay & control functions) Redundant battery systems with dedicated station

DC load centers


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The Art of Line Protection

To detect transmission line faults andinitiate isolation of that fault on the linesegment with minimal impact to the rest

of the transmission system and to thecustomer.

Do it by isolating the minimum faultedsection in the quickest time.

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Typical 500kV Protection System7


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Breaker Failure Protection Scheme

Expand the clearing area for faults due to breakermis-operation (stuck breaker)Time delayed operation initiated by all trippingrelays using breaker as clearing pointTime coordinated to allow primary zone clearing but faster than other backup functions in order toavoid system instability conditions

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Typical BF Protection Logic9

BF Scheme Needs:BFI input from protection relaysFault detector setting

(*Transformer fault detector if necessary)

BF timer setting

OR AND

TIMER62-1

Breaker FailureScheme Output

50FD87T*

BFI


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Typical BF Timing10

Not a problem if the total fault clearing time is 12+cycles

The total fault clearing time shall not be longer thanthe system critical clearing time


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Line Relay Zones11

instantaneousBlocked

Blocked


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Typical Transmission Line12

t1 time zerot2 relay operate time (1/2 to 3 cycles)

t3 carrier start (immediate)t4 remote carrier received (channel time)t5 trip initiated from relayt6 breaker opens (2-4 cycle mechanical operate times)t7 breaker failure trip (20 cy from trip initiate)

t8 - Zone 2 trip (30 cy) & t9 - Zone 3 trip (90cy)

t1 t2 t3 t4 t5 t6 t7 t8 t9

strike detect

startreceive

Trip

Zone 3

Zone 2

BFoperate

breaker

opentimeline

action


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The Need

With addition of 2 nd nuclear site and expansion of500kV network, the recommended critical clearingtime would be:

5.5 cycles for multi-phase fault8.0 cycles for single-phase fault

Need faster reset times for BF schemes to avoidovertrip

Use of IPT (Independent Pole Trip) breakers

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Can the new scheme Meet the Need?

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Considerations

Relay operating time: 2 cyclesFailed breaker operating time: 2 cyclesRelay 50BF reset time: 1 cycle

BF timer safety margin: 2 cyclesLocal and remote contributing breaker operating time: 2 cyclesDTT channel time: 0.5 cyclesTotal BF times = Critical clearing: 9.5 cycles

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Latency16

Just how fast must it be?

< 6 ms

Telecom Delivers the Message

< 6 milliseconds

Relay/Protection Executes the Action

< 10 milliseconds

Total Time to React< 1 Cycle ~ 16 milliseconds


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What system or relays are available?

Line, auto, and bus differential protection relays to be sub-cycle type

Directly tripping breaker(s) and issuing BFIEliminate auxiliary/tripping relays from the circuitReplace PLC, lease line, and micro-wave with dedicate fiberoptic cable or fiber optic based multiplexor

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Breaker Failure Protection Relay18

BF protection relay to be sub-cycle typeDirectly tripping breakers and DTT

Re-sequence the BF logic to discount fault detector

reset time Allow the BF timer to time out first


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BF Timing Improvement19

Relay operating time: 1 cycles

Failed breaker operating time: 2 cycles

Relay 50BF reset time: 1 cycle

BF timer safety margin: 2 cycles

Local and remote contributing

breaker operating time: 2 cycles

DTT channel time: 0.5 cycles

Total BF times = Critical clearing: 7.5 cycles


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Issues with IPT Breakers21

Low SF6 Gas:Slow leakage to critically low => breaker opens and block closeFast leakage to critically low => breaker block operation andlock into its current position => all three poles inoperable

Loss of Spring Charge:Sudden loss of spring charge => breaker block operation andlock into its current position => all three poles inoperable


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The Solution22

Implement dual BF timer scheme with IPT breakerTypical time = 8.0 cycles for single-phase fault

One IPT pole failsShort time = 5.5 cycles for multi-phase fault

Two or three IPT pole failsBF relay armed to bypass the failed breaker and directly trips thelocal and remote contributing breakers


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Summary


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Multi-Phase Fault BF Time24



BF timer safety margin: 0 cyclesLocal and remote contributing





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BF Time with Bypass Logic25



BF timer safety margin: 0 cyclesLocal and remote contributing





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Where Do We Go Next26

Consider its expanded use where criticalclearing time margins are becoming morecritical

Continue to expand our fiber network toprovide communications assisted relayingand BF-DTTLook into peer to peer communication

network among IEDs in the substation to cutdown IED contact operating time and wiring


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Questions?

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transmission duong pardo & elmore 500kv bf protection

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