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Sub Operations Step 4 > Lockout Relays > Flashcards

Lockout Relays Flashcards

1
Q

Purpose of a LOR

A

Trip all PCB’s necessary in order to isolate a fault

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2
Q

Functions of a LOR

A
  • Initiate the trip of one or more PCB’s.
  • Disable the PCB’s close circuit
  • Initiate alarms
  • Provide indications to SCADA
  • Initiate a trip in remote tripping schemes
  • Trip to other LORs (not preferred)
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3
Q

Applications of LORs

A
  • Bus
  • Lines in breaker and a half and ring bus
  • PCB’s in breaker and a half and ring bus
  • Transformers
  • Reactors
  • Series Capacitors
  • Dead Bus Clearing
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4
Q

Applications of LORs

A
  • Bus
  • Lines in breaker and a half and ring bus
  • PCB’s in breaker and a half and ring bus
  • Transformers
  • Reactors
  • Series Capacitors
  • Dead Bus Clearing
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5
Q

What relays trip to LORs

A
  • Bus: BFR and bus diffs
  • Line: BFR
  • PCB: BFR
  • Transformer: transformer diff, overcurrent relays, sudden pressure relays and tertiary ground detectors
  • Reactor: reactor diffs, overcurrent relays, and sudden pressure
  • Series Caps: GE controllers (PJC)
  • Dead Bus Clearing: dispatcher controll
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6
Q

What are some manufacturers and types of LORs

A

General Electric: HEA/HFA
Westinghouse: WL
Electro Switch: type 24
Bodine Electric: LOR

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7
Q

Hand reset LOR

A
  • Manually reset LOR
  • Used for equipment that we do not want to be re-energized without an Operator first performing a visual inspection, like transformers and reactors, which are expensive and easily damaged by fault current
  • A disadvantage is that there will be a delay in system restoration.
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8
Q

Automatic reset LOR

A
  • used when inspection is not required and fast restoration is a priority
  • resets after a time delay or a reset output from a relay like the SEL-BFR
  • resets with a motor or solenoid
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9
Q

Applications for Automatic reset LORs

A 
Bus
Line
BFRs 
Auto isolation schemes
Dead bus clearing
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10
Q

Procedure to cutout a LOR

A
  • Open all LOR trip knife switches, including spares
  • Open all LOR close interlock knife switches, including spares
  • The LOR operating coil and alarm switches remain cut in
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11
Q

How to restore an LOR

A

After removing or restoring the desired relay from service.

  • Ensure that the LOR is not tripped.
  • Close all close interlock knife switches including spares.
  • Close all trip knife switches including spares
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12
Q

What is the purpose of the close interlock knife switches on an LOR?

A

Allows the removal of a series contact in the Closed Circuit of the PCB, buy something around the series contact, while keeping the closed-circuit intact so the PCB can operate if needed

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13
Q

List the typical relays and relay schemes utilized by BPA that trip an LOR

A
  • Differential relays.
  • BFRs.
  • Sudden pressure and gas detector relays. -Dead bus clearing.
  • Line relaying on Breaker and a half and ring bus
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14
Q

When must an LOR be cut out

A
  • If a relay that trips to the LOR cannot be removed from service via a single point of isolation then the LOR must be cut out prior to removal.
  • LOR relays must be cut out prior to restoring any relay that trips to an LOR
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15
Q

What are some typical switching procedures that require a LOR to be cut out

A
  • Bypassing a breaker associated with a Transformer and the CT contribution is going to be bypassed for the differential scheme, this requires cutting out the differential relay and therefore the LOR will need to be cut.
  • When removing or restoring the sudden pressure relay for sub maintenance to take oil samples.
  • for 500kb PCBs with SEL-BFR, when the PCB will be removed from service for maintenance the SEL-BFR will need to be cut out, which trips to the LOR, therefore the LOR will need to be cut out
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16
Q

What would you do following a LOR operation associated with the Bus

A
  • Check the SER/ORION and logger print out to determine the sequence of events.
  • Check the bus differential relay and PCB bfr relays four targets.
  • Check to see if the bus Lor is reset. -Check for other relay targets.
  • Clear the switchyard of personnel.
  • Inspect the bus for caught of the fault.
  • Isolate any faulted equipment if found.
  • If the bus is okay test energize the bus. -Once bus is test energized restore the bus using available pcbs
17
Q

What would you do following me LOR operation associated with the Transformer or reactor?

A
  • Check the SER/ORION and logger print out to determine the sequence of events. -Check for tripped Bank LOR.
    - Bank hours are hand reset only do not reset before inspecting.
  • Check bank relays for targets to determine what trip the LOR.
  • Determine if it was an internal or an external to the bank.
  • Sudden pressure relays or Bank differential relays are most likely internal.
    • Residual overcurrent trips could be due to an external fault.
  • Inspect the bank.
  • If the fault is internal to the bank isolate the bank for maintenance.
  • If the fault was external to the bank you can bypass and restore the bank to operation
18
Q

What would you do following an Lor operation associated with the capacitor group

A

Most shunt capacitor groups do not have LORs. However if you have one determine what caused the LOR to operate.

  • Check the SER/Orion and logger print out to determine the sequence of events
  • check the SEL-187 or 287 for targets or check for other protection like over currents to have tripped the LOR.
  • Do not reset the LOR before inspecting if handset LOR.
  • Determine if it is a capacitor problem or external like loss of potential voltage differential or something else.
  • Isolate the cap group and repair if needed
19
Q

What would you do following an LOR operation associated with a 500 kV line

A
  • Check the SER/ORION and logger print out for sequence of events.
  • Check line relays for targets.
  • Determine what caused the LOR to operate.
  • Did the PCB relay open and reclose? -Determine the location and type of fault.
  • If the PCB is locked out have TLM patrol the line and clear it for repair.
  • If determined to be a temporary fault test energize the line.
20
Q

What relays trip to line LORs

A

BFRs

21
Q

What relays trip to PCB LORs

A

BFRs

22
Q

What relays trip to transformer LORs

A

Transformer Diff
Overcurrent relays
Sudden pressure relays
Tertiary Ground Detectors

23
Q

What relays trip to Reactor LORs

A

Reactor Diffs
Overcurrent relays
Sudden pressure relays

24
Q

What relays trip to Series Cap LORs

A

GE controllers (PJC)

25
Q

What relays trip to DBC LORs

A

Dispatcher controlled. No voltage verified by an IRC relay

26
Q

What relays trip to a Bus LOR

A

BFRs

Bus Diffs

27
Q

What are the specific functions of the Lor knife switches

A
  • Trip outputs.
  • Close interlocks.
  • Trip negative.
  • Trip positive.
  • Alarm
28
Q

What is a repeat relay

A

Repeat relays provide information to other equipment such as reclosing schemes

29
Q

Why do we leave the trip positive, trip negative, and alarm knife switches closed while cutting out a lockout relay.

A
  • Allows us to easily recognize if a tripping relays contacts have inadvertently closed.
  • Dispatcher May request the alarm switch to be opened during trip checks to avoid nuisance alarms

Sub Operations Step 4 (7 decks)

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