Effective Application of Breaker Failure Schemes

C L A R I T Y ▪ A S S U R A N C E ▪ R E S U L T S

M I D W E S TR E L I A B I L I TYO R G A NI Z A T I O N

“Maintain and improve the quality of life through a reliable regional bulk power system.”

AuthorRich Quest

2016 MRO Reliability Conference: Protection SystemsMay 25, 2016

Effective Application of Breaker Failure SchemesSecurity and Reliability Considerations

CLARITY ▪ ASSURANCE ▪ RESULTS

2 General Schemes with Over Sized Impact

Bus Differential Schemes• Primary Reliability Impact from Unnecessary Operation

Breaker Failure Schemes• Reliability Impact due to Unnecessary Operation is Similar to that of Bus

Differential Schemes• Reliability Impact due to Failure to Operate can be Especially Severe

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Straight Bus Differential False Operation

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Straight Bus BF False Operation

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Bus Differential False Operation

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115kV Bus 1

115kV Bus 2

DistXfmr

Transmission Lines

Generator

Shunt Capacitor


BF Relay False Operation

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115kV Bus 1

115kV Bus 2

DistXfmr

Transmission Lines

Generator

Shunt Capacitor


Bus Protection System Failure to Operate

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115kV Bus 1

115kV Bus 2

Transmission Lines

Generator

500kVGenerator

35 Miles


BF Relay Failure to Operate

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115kV Bus 1

115kV Bus 2

Transmission Lines

Generator

500kVGenerator

35 Miles


Power Circuit Breakers

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N-1 vs N-X

TPL standards require the study of effects of single contingencies (N-1) on a properly operating power system• Some contingencies include proper response to “stuck” breakers

Protection Systems operate in N-1 conditions• In most cases the condition is really N-1 AND COUNTING!• Ideally Protection Systems will operate, and leave the power system in an

N-1 condition—Reality is not always ideal—Breakers can and do Fail

• Conditions are now N-X, and it is crucial to limit the value of X

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Basic Breaker Failure Scheme

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X50 0 86

62X62Y52

TC2


Basic Breaker Failure Scheme for Shared Breakers

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21P1 21G1 21P2 21P2

62P 62P 62G62G

94-1 62x

Digital Line Relay

94-1 Trips Line Breakers Coil 1

62x Initiate BF Timing on Line Breakers

Trip Line BkrsCoil 2

Initiate BFLine Bkrs

86B 62B

(94-2) (62y)

87BA

87BB

87BC

86B Trip & Lock Out all Bus Breakers

62B Initiate BF on all Bus Breakers

50 0X

OR

AND 86BF

62y62x

62B


Basic Scheme Features

Fault Detecting Relays are used to initiate timing• Initiation occurs when trip commands are sent to the breaker• Control trips do not initiate breaker failure timing

The presence of fault current supervises timing• Successful interruption of current ends timing even if the initiating contacts

are latched, or otherwise sealed in• Timing continues in the event that the breaker operates but fails to interrupt

the fault current

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Determining BF Time Delay

Considerations that tend to shorten Time Delay• Proximity to Generation• High Fault Level

—Stability Issues—Equipment Damage

• Trip Coil Duty (Not really a consideration?)Considerations that tend to lengthen Time Delay• Low Fault Level• Load Loss

Time delay must be short enough to ensure stability and Coordinate with over reaching relay elements

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Determining Breaker Failure Time Delay

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Order 754 Events

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Washington DC Event

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MRO Event

The circuit breakers failed to open for the fault because of a firmware update improperly performed on the line primary and secondary digital distance relays. When the firmware in the relays was updated the IEC61850 file that controls the GOOSE messaging in the relays was not reloaded, resulting in non functional GOOSE messaging. The GOOSE messaging in these relays is used to trip the power circuit breakers and initiate Breaker Failure timing.• Loss of two 115kV lines, one 230kV line, and a 230:115kV transformer.• Testing Issues

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Modification for very low fault current levels

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Improper Logic Misoperation

Prefault Conditions• 50BF/52a OR logic was in fact AND logic• B phase Breaker Operating Rod Broken

B Phase Fault Occurs• Breaker operates opening A & C phases, but not B phase• 52a contact opens ending breaker failure timing• Fault persists until cleared by multiple remote Protection Schemes

—Finally, a bit of good luck

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NERC Responses

NERC issued a Lesson Learned Report (2010)• The NERC Lesson Learned discusses the importance of weighing the

advantages and disadvantages of combining breaker position indication and fault current indication to create a logical AND requirement versus a logical OR requirement to supervise breaker failure protection.

NERC SPCS Report Noted:• Security of the breaker failure protection scheme can be improved by

creating a logical AND requirement with breaker position indication and fault current detection. However, the negative impact on dependability outweighs any improvement in security…

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Unnecessary BF Operations 2013 - 2015

3 Misoperations due to continuously energized fault detectors• 1 as left jumper, 1 miswired polarity, 1 setting• All should have been observable

3 Miswired CT connections to 50BF element4 Improper Settings• 2 improperly set outputs, 2 unidentified setting issues

2 Initiated during non fault conditions1 Operation on overcurrent without fault detection2 SBFU trips on transients (2 Entities)1 Unidentified cause

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50BF Wiring

3 Misoperations whereimproper wiring indicatedcurrent flow through anopen breaker

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52-1

52-2

50 21-R 21-2 67G

50

RcvBlock

95 62x

Trip52-152-2

Ini BF52-152-2

50BF

50BF

50BF

Proper location of 50BF relayImproper location of 50BF


Use Your Digital Recordings

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Initiation time to current interruption• Compare to BF Time Allowance• Compare to Expected Breaker

Operating Time• Look at each phase current

Program Inputs and Outputs• Use Trip Surge Detectors• Program a slow interruption alarm

Studying your breaker performance during faults can prevent future breaker failures


IEEE C37-119

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Questions?

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Documents

Effective Application of Breaker Failure Schemes