Schweitzer Engineering Laboratories SEL-311L, Instruction Manual, Page: 391 / 734

Date Code 20010625 Setting the Relay 9-53
SEL----311L Instruction Manual
Close Logic Equations (See Figure 6.1)
Circuit breaker status (used in Figure 5.5, also) 52A = IN101
Connect the circuit breaker 52a contact to IN101. See Section 2: Installation for examples of
breaker status connections.
Close conditions (other than automatic reclosing or
CLOSE command) CL = CC
Unlatch close conditions ULCL = TRIP
See Unlatch Close in Section 6: Close and Reclose Logic .
Reclosing Relay Equations (See Reclosing Relay in Section 6 )
Reclose initiate 79RI = M1P + Z1G + T50P + T50G
Initiate a reclose for all instantaneous faults on the protected line section.
Reclose initiate supervision 79RIS = 1
Drive-to-lockout 79DTL = !IN102 + OC
Use a switch connected to IN102 to enable reclosing. Drive the recloser to lockout when IN102
(reclose enable) deasserts. Use open command OC to block reclosing during a manual breaker
trip.
Drive-to-last shot 79DLS = 0
Skip shot 79SKP = 0
Stall open interval timing 79STL = 0
Block reset timing 79BRS = 0
Sequence coordination 79SEQ = 0
Reclose supervision (see Figure 6.2) 79CLS = 1
Reclose supervision is normally used with synchronized closing. Set 79CLS = 1 to allow reclosing
to proceed after the open interval time-out.
Torque Control Equations for Time-Overcurrent Elements
Phase element (see Figure 3.47) 51PTC = M2P
Residual ground element (see Figure 3.48) 51GTC = Z2G
Time overcurrent elements 51PT and 51GT using Zone 2 distance elements for torque control will
operate in the forward direction only.
Torque Control Equations for Tapped Load Time-Overcurrent Elements
Phase inverse time (see Figure 3.23) T51PTC = 87LA + 87LB + 87LC
Ground inverse time (see Figure 3.24) T51GTC = 87LG
Phase instantaneous (see Figure 3.20) T50PTC = 87LA + 87LB + 87LC
Ground instantaneous (see Figure 3.21) T50GTC = 87LG
Use 87L elements for tapped load torque control for increased security during ct saturation and 87
channel asymmetry.