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Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Ampere
Continuous
Tap Value
TAP
Range
(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-8, IRC-8, IRP-8
IRD-9, IRC-9, IRP-9
At
Power
3 Times
Factor
Tap Value
Tap Value
φ
Angle
Current
Current
72
2.38
71
2.38
69
2.40
67
2.42
62
2.51
57
2.65
53
2.74
70
2.38
66
2.40
64
2.42
62
2.48
60
2.53
58
2.64
56
2.75
68
2.38
63
2.46
60
2.54
57
2.62
54
2.73
48
3.00
45
3.46
‡
VOLT AMPERES
At
At
10 Times
Tap Value
Current
21.0
132
21.0
134
21.1
142
21.2
150
22.0
170
23.5
200
24.8
228
21.0
136
21.1
142
21.5
149
22.0
157
22.7
164
24.0
180
25.2
198
21.3
146
21.8
158
22.6
172
23.6
190
24.8
207
27.8
248
31.4
292
41-133S
At
20 Times
Tap Value
Current
350
365
400
440
530
675
800
360
395
430
470
500
580
660
420
480
550
620
700
850
1020
17
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