8
Fig. 4 illustrates how the operation characteris-
tic of the module are affected by the selector
switches SG1 on the front panel and the external
control signal BACTRL.
Fig. 4. Operation characteristic of the directional neutral overcurrent relay module SPCS 3C4.
Fig. 4a shows the I
0
sin
ϕ
characteristic, Fig. 4b the I
0
cos
ϕ
characteristic.
Switchgroup SG2 is a so called software switch-
group, which is located in the third submenu of
switchgroup SG1. In switchgroup SG2 the mode
of operation of the LED indicators is selected.
The start and operation indicators of the low-set
stage and the high-set stage can be given self
reset mode of operation or manual mode of
operation.
The selection is made by means of a checksum
which is calculated from the table below. Nor-
mally the start indications are self reset and the
operation indications are manualy reset.
Indication
Manual Default
Starting, stage I
ϕ
>, yellow
1
0
Tripping, stage I
ϕ
>, red
2
2
Starting, stage I
ϕ
>>, yellow
4
0
Tripping, stage I
ϕ
>>, red
8
8
Checksum
∑
15
10