Schweitzer Engineering Laboratories SEL-311C, Instruction Manual

Page: 98 / 748

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 67Q n 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.