Schweitzer Engineering Laboratories SEL-321 - Voltage Elements; Time-Step Backup Time Delay Settings

Date Code 20011026 Applications 5-15
SEL-321/321-1 Instruction Manual
E51Q = Y
YY
Y
51QP = 2.2
2.22.2
2.2
51QC = U3
U3U3
U3
51QTD = 2.00
2.002.00
2.00
51QRS = N
NN
N
51QTC = 32QF
32QF32QF
32QF
E50Q = N
NN
N
- Relay Elements and Other Settings Affected
Relay elements 51QT and 51QP depend on the 51QP, 51QTD, 51QC and 51QTC settings.
50Q1, 50Q2, 50Q3, 50Q4, 67Q1, 67Q2, 67Q3, 67Q4, 67Q2T, 67Q3T, and 67Q4T elements.
Voltage Elements
Voltage elements are not required for this application. The voltage elements are disabled by
setting EVOLT = N.
EVOLT = N
NN
N
- Relay Elements and Other Settings Affected
Relay elements 27L, 3P27, 59PB, 59PR, 59N, 59L and 3P59.
Time-Step Backup Time Delay Settings
The relay provides time delayed pickup timers for time-stepped backup protection. Separate
timers are provided for the Zone 2, 3, and 4 phase and ground distance elements. Timers are
provided for all four levels of the residual and negative-sequence overcurrent elements. The
residual and negative-sequence overcurrent time delays are independently set.
For our example, three zones of phase and ground distance elements are selected. In this case,
the Zone 2 and 3 phase and ground distance time delays must be set. Zone 2 elements must
coordinate with downstream Zone 1 elements, plus downstream breaker operating time, plus a
safety margin. A typical Zone 2 phase and ground distance time delay setting is 20 cycles.
The Zone 3 element is reverse-reaching and is not required for backup protection. The Zone 3
element is set for a zero time delay and is not set in the tripping mask.
For the relay at Breaker 3:
Z2PD = 20.00
20.0020.00
20.00
Z3PD = 0.00
0.00 0.00
0.00
Z2GD = 20.00
20.0020.00
20.00
Z3GD = 0.00
0.00 0.00
0.00
- Relay Elements and Other Settings Affected
M2PT, M3PT, Z2GT, and Z3GT elements.