P.3.340
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Protection Application Examples
We would have the following at Relay R:
Pickup: 1/2 • (V
LN
/ [ • CTRR])
= 1/2 • (199.19 kV / [18 • 160])
= 34.6 A
50P1P := 34.6 Level 1 Pickup (OFF, 0.25–100 A, sec)
We would have the following at Relay T:
Pickup: 1/2 • 1/N • (V
LN
/ [Z1T • CTRT])
= 1/2 • (69 / 345) • (199.19 kV / [20 • 2000])
= 0.5 A
50P1P := 0.5 Level 1 Pickup (OFF, 0.25–100 A, sec)
We would have the following at all relays:
67P1D := 0.000 Level 1 Time Delay (0.000–16000 cycles)
Fault levels resulting from close-in external faults are less than the pickup
values we have chosen, so these elements do not need to be directional.
67P1TC := 1 Level 1 Torque Control (SEL
OGIC control equation)
Enable a 50G element at Terminal T to provide sensitive ground fault
protection for the delta winding. This element does not need to coordinate
with other protection, and it does not need to be directional; polarizing the
element is impossible at this terminal in any case. Delay the element by 30
cycles to avoid operation for CT saturation during heavy phase faults.
We would have the following at Relay T:
50G1P := 1 Level 1 Pickup (OFF, 0.25–100 A, sec)
67G1D := 30 Level 1 Time Delay (0.000–16000 cycles)
67G1TC := 1 Level 1 Torque Control (SEL
OGIC control equation)
Selectable Operating Quantity Time-Overcurrent Element
Use inverse-time overcurrent protection to provide backup protection for high-
resistance ground faults. Select zero-sequence line current as the operating
quantity. Set the pickup to 20 percent of the value for a bolted single phase-to
ground fault at the remote terminal. The relays at terminals S and R respond to
the zero-sequence current on the line. At Terminal T, the relay measures the
transformer neutral current through input IAX.
We would have the following at relays S and R:
51O01 := LIGFIM Op. Qty (LI[]FIM, [nn]I[]FIM, LI1FIM, L3I2FIM,
LIGFIM, [nn]IGFIM, LIMAXM)
where nn = B1, B2, and = A, B, C.
We would have the following at Relay T:
51O01 := B2IAFIM Op. Qty (LI[]FIM, [nn]I[]FIM, LI1FIM,
L3I2FIM, LIGFIM, [nn]IGFIM, LIMAXM)
We would have the following at Relay S:
51P01 := 0.8 O/C Pickup (0.25–16 A, sec)
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