VAMP 257
Feeder and motor manager
Technical description
VAMP Ltd
44
VAMP 24h support phone : +358 (0)20 753 3264
VM257.EN002
2.3.12.
Earth fault protection (50N/51N)
The manager has two separate energizing inputs rated 1 A (I
0
>
and I
0
>>) and 5 A (I
02
> and I
02
>>), both of which can be used
simultaneously. The function of the stages I
0
> and I
0
>> is based
on the measured current connected to the input 4 (terminal
X1:7-8). The function of the stages I
02
> and I
02
>> is based on
the measured current connected to the input 5 (terminal X1:9-
10).
The terminal measures the fundamental frequency component
I
0
. Thus, the degree of attenuation of the third harmonic is at
least 60 dB. This contributes to the extremely high accuracy of
the earth fault protection, which is insensitive against
harmonics.
Figure 2.3.12-1. Block diagram of the earth fault stages I
0
>
Figure 2.3.12-2. Block diagram of the earth fault stages I
0
>>, I
02
> and I
02
>>
