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Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Ampere
Continuous
Tap Value
Range
TAP
(Amperes)
0.5
0.6
0.8
1.0
0.5/2.5
1.5
2.0
2.5
2
2.5
3
2/6
3.5
4
5
6
4
5
6
7
4/12
8
10
12
†
Thermal capacities for short times other than one second may be calculated on the basis of time being inversely
proportional to the square of the current.
φ
Degrees current lags voltage at tap value current.
‡
Voltages taken with high impedance type voltmeter
ENERGY REQUIREMENTS
TIME OVERCURRENT UNITS:
One Second
†
Rating
Rating
(Amperes)
2.7
88
3.1
88
3.7
88
4.1
88
5.7
88
6.8
88
7.7
88
8
230
8.8
230
9.7
230
10.4
230
11.2
230
12.5
230
13.7
230
16
460
18.8
460
19.3
460
20.8
460
22.5
460
25
460
28
460
IRD-5, IRC-5, IRP-5
IRD-6, IRC-6, IRP-6
At
Power
3 Times
Tap Value
Tap Value
Factor
φ
Angle
Current
Current
69
3.92
20.6
68
3.96
20.7
67
3.96
21.0
66
4.07
21.4
62
4.19
23.2
60
4.30
24.9
58
4.37
26.2
67
3.88
21.0
66
3.90
21.6
64
3.93
22.1
63
4.09
23.1
62
4.12
23.5
59
4.20
24.8
57
4.38
26.5
65
4.00
22.4
63
4.15
23.7
61
4.32
25.3
59
4.35
26.4
56
4.40
27.8
53
4.60
30.1
47
4.92
35.6
‡
VOLT AMPERES
At
At
10 Times
Tap Value
Current
103
106
114
122
147
168
180
110
118
126
136
144
162
183
126
143
162
183
204
247
288
41-133S
At
20 Times
Tap Value
Current
270
288
325
360
462
548
630
308
342
381
417
448
540
624
376
450
531
611
699
880
1056
15
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