Technical Manual WIC1
Woodward
DOK-TD-WIC1E, Rev. L
49
6.8 Special features for earth current tests
Functional description:
In the WIC1 the earth current is calculated and cannot be measured. It is established from the geometrical amount
of the three phase current values, more or less a numerical Holmgreen. If, for instant, a single-phase test current is
impressed, the measuring value (tripping value) in the earth current path equals the current in the tested phase. If,
with a phase shift of 120° a three-phase test current is impressed, the measuring value in the earth current path
equals zero.
Requirement on the test system:
The WIC1 is powered by the instrument transformer. In order to guarantee reliable tripping a minimal current of
0.9 x lowest nominal CT current (0.9 x lowest I> setting) has to flow in one of the phases. If the setting of the earth
current IE> is lower than the smallest possible switching point for the phase current, then the switching point for
earth current tripping can only be tested by a three-phase power source. In case the set switching point for earth
current is higher than the smallest possible switching point for overcurrent tripping (Is x I>, then the test can be per-
formed with a single-phase power source.
6.8.1 Switching points for the earth current step
DIP 1-1
OFF ON OFF ON OFF ON OFF ON OFF ON OFF ON OFF ON OFF ON
DIP 1-2
OFF OFF ON
ON OFF OFF ON
ON OFF OFF ON
ON OFF OFF ON
ON
DIP 1-3
OFF OFF OFF OFF ON
ON
ON
ON OFF OFF OFF OFF ON
ON
ON
ON
DIP 1-4
OFF OFF OFF OFF OFF OFF OFF OFF ON
ON
ON
ON
ON
ON
ON
ON
HEX switch
IE>
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
Setting IE>
0.2** 0.3** 0.4** 0.5** 0.6** 0.7** 0.8** 0.9
1
1.2
1.4
1.6
1.8
2.0
2.5 EXIT
Is = Hex „0“
0,064
0,096 0,128 0,160 0,192 0,224 0,256 0,288 0,320 0,384 0,448 0,512 0,576 0,640 0,800
-
Is = Hex „1“
0,072 0,108 0,144 0,180 0,216 0,252 0,288 0,324 0,360 0,432 0,504 0,576 0,648 0,720 0,900
-
Is = Hex „2“
0,080 0,120 0,160 0,200 0,240 0,280 0,320 0,360 0,400 0,480 0,560 0,640 0,720 0,800 1,000
-
Is = Hex „3“
0,088 0,132 0,176 0,220 0,264 0,308 0,352 0,396 0,440 0,528 0,616 0,704 0,792 0,880 1,100
-
Is = Hex „4“
0,096 0,144 0,192 0,240 0,288 0,336 0,384 0,432 0,480 0,576 0,672 0,768 0,864 0,960 1,200
-
Is = Hex „5“
0,104 0,156 0,208 0,260 0,312 0,364 0,416 0,468 0,520 0,624 0,728 0,832 0,936 1,040 1,300
-
Is = Hex „6“
0,112 0,168 0,224 0,280 0,336 0,392 0,448 0,504 0,560 0,672 0,784 0,896 1,008 1,120 1,400
-
Is = Hex „7“
0,120 0,180 0,240 0,300 0,360 0,420 0,480 0,540 0,600 0,720 0,840 0,960 1,080 1,200 1,500
-
Is = Hex „8“
0,128 0,192 0,256 0,320 0,384 0,448 0,512 0,576 0,640 0,768 0,896 1,024 1,152 1,280 1,600
-
Is = Hex „9“
0,136 0,204 0,272 0,340 0,408 0,476 0,544 0,612 0,680 0,816 0,952 1,088 1,224 1,360 1,700
-
Is = Hex „A“
0,144 0,216 0,288 0,360 0,432 0,504 0,576 0,648 0,720 0,864 1,008 1,152 1,296 1,440 1,800
-
Is = Hex „B“
0,160 0,240 0,320 0,400 0,480 0,560 0,640 0,720 0,800 0,960 1,120 1,280 1,440 1,600 2,000
-
Is = Hex „C“
0,176 0,264 0,352 0,440 0,528 0,616 0,704 0,792 0,880 1,056 1,232 1,408 1,584 1,760 2,200
-
Is = Hex „D“
0,192 0,288 0,384 0,480 0,576 0,672 0,768 0,864 0,960 1,152 1,344 1,536 1,728 1,920 2,400
-
Is =
Hex „E“
0,208 0,312 0,416 0,520 0,624 0,728 0,832 0,936 1,040 1,248 1,456 1,664 1,872 2,080 2,600
-
Is = Hex „F“
0,224 0,336 0,448 0,560 0,672 0,784 0,896 1,008 1,120 1,344 1,568 1,792 2,016 2,240 2,800
-
Table 6.5: Test current via the CD winding with the IE> step and the different Is setting values
** When the earth current setting is <0.9 x Is a three-phase test system has to be used for correct testing. With a
single-phase test the trip is only triggered from 0.9 x Is on.
