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Setting the Relay
Date Code 20010625
SEL-311L Instruction Manual
800
4584.6
1 • 10
3
100
10
1
0.1
0.01
100
1 • 10
3
1 • 10
4
Time
(sec
on
ds)
T51P Overcurrent Protection
Transformer Overcurrent Protection
Primary Amps
Lowest Phase
Differential Current
T51PT
Load Transformer
Primary Overcurrent
Protection
609.8
Max. Load
Transformer
Secondary Fault
Current
T50P
M311L139
Time delay (OFF, 0.00–16000.00 cycles)
T50PD = OFF
No time delay is needed since the tapped load phase instantaneous overcurrent element does not
see faults on the load transformer secondary.
Tapped-Load Residual Ground Time-Overcurrent Element Settings (If ETG = Y)
Pickup (OFF, 0.50–16.00 A secondary)
T51GP = 2.0
Since the transformers are connected delta-wye and T51G is a differential element, T51G only
asserts for faults on the transmission line.
Set the T51GP = 2.0 A to detect a high resistance ground fault on the transmission line.
(V secondary / T51GP) • (CTR / PTR) = (66.4 / 2.0 )• (2000 / 240) = 276.7 Ohms Primary
Curve (U1–U5; C1–C5)
T51GC = U3
Time dial (0.50–15.00 for curves U1–U5; 0.05–1.00 for curves C1–C5)
T51GTD = 1.00
Electromechanical reset delay (Y, N)
T51GRS = Y
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