Schweitzer Engineering Laboratories SEL-311C - Negative-Sequence Instantaneous;Definite-Time Overcurrent Elements

3.30
SEL-311C Relay Instruction Manual Date Code 20060320
Distance, Out-of-Step, Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Instantaneous/Definite-Time Overcurrent Elements
Settings Ranges
Accuracy
Pickup and Reset Time Curves
See Figure 3.20 and Figure 3.21.
Negative-Sequence
Instantaneous/
Definite-Time
Overcurrent Elements
Four levels of negative-sequence instantaneous/definite-time overcurrent
elements are available. The different levels are enabled with the E50Q enable
setting, as shown in Figure 3.23.
To understand the operation of Figure 3.23, follow the explanation given for
Figure 3.19, substituting negative-sequence current 3I
2
[3I
2
= I
A
+ a
2
• I
B
+ a •
I
C
(ABC rotation), 3I
2
= I
A
+ a
2
• I
C
+ a • I
B
(ACB rotation), where a = 1 ∠
120° and a
2
= 1 ∠ –120°] for phase currents and substituting like settings and
Relay Word bits.
In Figure 3.23, Levels 1 and 2 67Qn elements have directional controls fixed
forward. Levels 3 and 4 have selectable forward and reverse directional
controls. See Figure 4.14 for more information on this optional directional
control.
Settings Range Description
Pickup Settings 50G1P–50G4P
OFF, 0.25–100.00 A secondary 5 A nominal phase current inputs, IA, IB, IC
OFF, 0.05–20.00 A secondary 1 A nominal phase current inputs, IA, IB, IC
Definite-Time Settings 67G1D–67G4D
0.00–16000.00 cycles, in 0.25-cycle steps
Pickup
±0.05 A secondary and ±3% of setting
(5 A nominal phase current inputs, IA, IB, IC)
±0.01 A secondary and ±3% of setting
(1 A nominal phase current inputs, IA, IB, IC)
Timer
±0.25 cycles and ±0.1% of setting
Transient Overreach
±5% of setting
IMPORTANT: See Appendix F:
Setting Negative-Sequence
Overcurrent Elements for information
on setting negative-sequence
overcurrent elements.