Woodward
Technical Manual WIC1
44
DOK-TD-WIC1E, Rev. L
6.3 Criteria to be taken into account for protection devices fed by CTs
With this kind of current supply it has to be taken into account that the CT has to feed more power than this is the
case for protection devices with an additional aux. voltage source. Furthermore it has to be noted that
– with refer-
ence to the entire measuring range of the protection devices
– the input impedance of the individual phases is not
linear. The necessary power for testing the WIC1 is shown on the following graphs.
Figure 6.1: Power consumption of one phase over the entire measuring range of the WIC1
Figure 6.2: Power absorbed by one phase over the range 0.1
– 10 lowest operating current
Lowest operating current = lower rated current x 0,9. The operating current is chosen by Is * I>.
WIC1-W1xx:
7.2 A (Is = 8 A)
WIC1-W2xx:
14.4 A (Is = 16 A)
WIC1-W3xx:
28.8 A (Is = 32 A)
WIC1-W4xx:
57.6 A (Is = 64 A)
WIC1-W5xx:
115.2 A Is = 128)
WIC1-W6xx:
230.4 A (Is = 256 A)
Is = lowest rated current
6.4 Special features for the WIC1 test
The WIC1 receives its supply energy out of the measuring circuit. Conditional on the circuit logic the WIC1 changes
its measuring load in a cyclic way and that in a 1 kHz cycle.
This can have an effect on the feeding source.
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
40
50
60
70
80
[VA]
[I/lowest operating current]
Power consumption per phase of the WIC1
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
8
9
10
[VA]
[I/lowest operating current]
Power consumption per phase of the WIC1