Lockout Relays Flashcards
Purpose of a LOR
Trip all PCB’s necessary in order to isolate a fault
Functions of a LOR
- 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)
Applications of LORs
- 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
Applications of LORs
- 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
What relays trip to LORs
- 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
What are some manufacturers and types of LORs
General Electric: HEA/HFA
Westinghouse: WL
Electro Switch: type 24
Bodine Electric: LOR
Hand reset LOR
- 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.
Automatic reset LOR
- 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
Applications for Automatic reset LORs
Bus Line BFRs Auto isolation schemes Dead bus clearing
Procedure to cutout a LOR
- 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
How to restore an LOR
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
What is the purpose of the close interlock knife switches on an LOR?
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
List the typical relays and relay schemes utilized by BPA that trip an LOR
- Differential relays.
- BFRs.
- Sudden pressure and gas detector relays. -Dead bus clearing.
- Line relaying on Breaker and a half and ring bus
When must an LOR be cut out
- 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
What are some typical switching procedures that require a LOR to be cut out
- 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
What would you do following a LOR operation associated with the Bus
- 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
What would you do following me LOR operation associated with the Transformer or reactor?
- 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
What would you do following an Lor operation associated with the capacitor group
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
What would you do following an LOR operation associated with a 500 kV line
- 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.
What relays trip to line LORs
BFRs
What relays trip to PCB LORs
BFRs
What relays trip to transformer LORs
Transformer Diff
Overcurrent relays
Sudden pressure relays
Tertiary Ground Detectors
What relays trip to Reactor LORs
Reactor Diffs
Overcurrent relays
Sudden pressure relays
What relays trip to Series Cap LORs
GE controllers (PJC)
What relays trip to DBC LORs
Dispatcher controlled. No voltage verified by an IRC relay
What relays trip to a Bus LOR
BFRs
Bus Diffs
What are the specific functions of the Lor knife switches
- Trip outputs.
- Close interlocks.
- Trip negative.
- Trip positive.
- Alarm
What is a repeat relay
Repeat relays provide information to other equipment such as reclosing schemes
Why do we leave the trip positive, trip negative, and alarm knife switches closed while cutting out a lockout relay.
- 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
