What is the function of LOR's?

Initiate trip of one or more PCBs Disable a PCB's close circuits Initiate alarms Provide indications to SCADA Initiate a trip in a remote tripping scheme Trip other lockout relays

What are the brands/models of LOR's?

General Electric-HEA (Hand reset) General Electric- HFA (Auto reset) Westinghouse- WL Electro switch- Type 24 Bodine Electric - LOR

What are LOR's used on?

Buses Banks Line in Breaker schemes (BFX) Dead Bus Clearing Reactors on Buses F+D Schemes GIS loss of gas LBD'S f-relay BFR to M/B LOR Cap banks

What is an LOR?

This is a mechanical relay device that is tripped by other relays and provides multiple functions. It is capable of tripping multiple PCBs as well as transfer trip. It also has close interlock contacts which open to prevent reclosing of PCBs. It may have various auxiliary functions associated with it, such as logic outputs to RAS, or SEL BFR auto isolation schemes.

Explain the application of handset vs motor reset LOR's.

-With transformers and reactors, the protected equipment is expensive and easily damaged by fault currents. In these cases we perform an on-site inspection of the affected equipment and an investigation as to the cause of the trip. Hand reset lockout relays are used so that an inspection must be made. -Automatically reset lockout relays are used where fast restoration is the greatest priority. For example, in the case of a bus lockout relay picked up by a bus differential relay, usually an automatic reset is used because the risk of damage to the bus is small compared to the importance of bus restoration.

Describe the procedure for cutting out a relay associated with an LOR and restoring it to service

1) Shall be removed from service prior to removing or restoring any relay that trips the LOR. 2) Shall be restored to service immediately after removing or restoring the desired relay when there are other relays that trip the LOR. 3) During the time that an LOR is removed from service the LOR operating coil and alarm knife switches shall remain closed. 1) Open all LOR trip knife switches including spares. 2) Open all LOR close interlock knife switches including spares. 3) Leave LOR operating coil and alarm switches closed. 4) Remove desired relay from service. 5) Close all LOR close interlock knife switches including spares. 6) Close all LOR trip knife switches including spares. WS IV.A-7&8

Explain the purpose of the close interlock knife switches on an LOR.

Knife switches are usually installed with each lockout relay. The knife switches allow different functions of the lockout relay to be independently cut out, or the entire relay cut out. The knife switches for the close circuit actually shunt the lockout relay out of the close circuit, preventing the lockout relay from disabling the close circuits so it can still trip and reclose.

What are some schemes that trip an LOR?

Power transformer or shunt reactor LOR Bank differential relay Sudden pressure relay Phase over current relays (primary, secondary, tertiary) Neutral (ground) over current relay PCB breaker failure relay Polarizing over current relay Main Bus differential LOR Main bus differential relay Breaker failure relay Dead bus clearing LOR Enabled by under voltage relay (GE ICR) when main bus is deenergized and SCS is in enabled position 500 kV line LOR 500 kV PCB BFR Line protective relays 500 kV bus LOR 500 kV PCB BFR Breaker & or Ring bus differential relay

Describe situations when a LOR needs C/O.

MVDT When bypassing a bank PCB position and a CT contribution is lost T/E construction Clearing a PCB for PCB removal/replace to C/O BFR, bus diff's, SEL 352 C/O of BFR's for PCB maintenance Relay maintenance Trip checks for relay maintenance Gas in oil samples-sudden pressure trips to LOR

What would you check for an LOR operation on a BUS?

Check SER and Printout to determine the sequence of events. Look for bus differential relay or breaker failure relay targets. Check to see if the Bus LOR is reset (motor resets). Check for other relay targets. Clear the switchyard of personnel. Inspect the bus for cause of fault. Isolate any failed equipment if any are found. Test energize the bus.

What would you check for an LOR operation on a transformer/reactor?

Look at SER and printout to determine what occurred. Check panel for tripped bank LOR. Bank LOR is hand reset only, you must inspect bank before resetting. Check bank relays for targets to determine what tripped the LOR. Determine if it is a bank problem or an external problem, sudden pressure or differential practically ensure bank problem, with a residual overcurrent trip could be due to an external fault. Inspect bank

What would you check for an LOR operation on GIS equipment?

Check SER and Printout to determine the sequence of events. Look for bus differential relay. Check to see if the Bus LOR is reset (motor resets). Check for other relay targets. Check for low gas pressures and inspect the bus. Isolate any failed equipment if any are found. Test energize the bus if no problem was found.

What would you check for an LOR operation on a Cap Group?

Look at SER and printout to determine what occurred. Check SEL 187/287 for targets or was it other protection that tripped the LOR (OC relays)? LOR is hand reset only, must inspect cap group before resetting. Determine if it is a cap problem or an external problem. Is it a loss of potential, voltage differential, or another problem? Isolate the cap group for repair.

What would you check for an LOR operation on a 500kv line?

Check SER and Printout to determine the sequence of events. Determine what caused the LOR (BFX) to operate. Did the PCBs relay and reclose? Gather targets and determine the location/type of fault. If locked out, have line patrolled and determine cause. Clear the line for repair.

Modern Electromechanical Relay Applications APPLICATION 1: Transients in Control Circuits

Problem Electric utilities use shielded control cables to minimize transients in control circuits and P relays are designed and tested to withstand transient voltages. However, an additional consideration is that the rapid response and low energy requirements of P relays has resulted in unwanted DTT (Direct Transfer Trip) actuations when trip signals are wired directly to P relays. In fact, utilities purchasing LJ relays have reported that transients in control scheme wiring have actually resulted in unwanted DTT actuations.

Solution Place high speed LJ relays near P relays and to use high speed LJ relays to serve as a buffer between wired inputs and P relays.

This is illustrated in Figures 2 & 3 for Conshohocken and Wyomissing Substations. In this application, Wyomissing Substation is not equipped with 138 KV fault interrupting devices and DTT is needed to trip the 138 KV circuit breaker at Conshohocken in the event that a transformer failure occurs at Wyomissing.

APPLICATION 2: Remote Lockout Reset

Problem Substations that are equipped with two, three, or more large power transformers, simultaneous actuation of multiple lockout relays is beyond design basis and can result in a significant number of customer interruptions.

Solution When faced with this possibility, some utilities have chosen to install LJ relays with remote reset capability rather than traditional, hand reset, lockout relays for transformer and bus differential relaying schemes. This application allows operators to quickly restore service to customers, using supervisory control, if multiple components trip out simultaneously.

This is illustrated in Figures 4 and 5 for Conshohocken Substation where LJ relays are actuated by Transformer T12, Transformer T14, Bus 1, Bus 2, and Bus 3 differential relays to trip circuit breakers when a fault occurs.

This remote reset feature allows operators to restore a transformer or bus to service when substation video images do not show signs of arcing and damaged insulators, sudden pressure relays have not actuated, and other indicators of component failure are not evident at the remote power control center.

APPLICATION 3: Contact Multiplication

Problem Substations that are equipped with protective relays that have limited trip output contacts, such as electromechanical bus differential relays.

Solution The LJ relays can serve as a contact multiplier. LJ relays are ideal for this application as the rated contact closing time is 4 ms.

This application is illustrated in Figure 6 where a bus differential relay for Bus 2 actuates an LJ relay that trips the two sectionalizing circuit breakers that are connected to Bus 2 (shown in Figure 4).

What is the function of LOR's?What are the brands/models of LOR's?What are LOR's used on?What is an LOR?Explain the application of handset vs motor reset LOR's.Describe the procedure for cutting out a relay associated with an LOR and restoring it to serviceExplain the purpose of the close interlock knife switches on an LOR.What are some schemes that trip an LOR?Describe situations when a LOR needs C/O.What would you check for an LOR operation on a BUS?What would you check for an LOR operation on a transformer/reactor?What would you check for an LOR operation on GIS equipment?What would you check for an LOR operation on a Cap Group?What would you check for an LOR operation on a 500kv line?APPLICATION 2: Remote Lockout ResetAPPLICATION 3: Contact Multiplication