homopolar protection

[switchgearD]

Dear Colleagues
I've got switchgear that is combained of one section - 12 cubicles three phease switchgear and second section - 8 cubicles - single phase switchgear. Homopolar protection is required and indication of specific tore in 3-phase cubicle that is linked to single phase cubicle in the second section. Please advice how can it be carried out and if it is not as complicated as it seems
Many thanks

 

[pisimatza]

Hi.
I guess it is low voltage?
Section 1 - 3 phase 12 cubicles, section 2- 1 phase, 8 cubicles?
If section 2 is so big, why don't u have 3 phase section , for 1 phase loads, with rotation of phases?
Anyway, you want unrestricted earth fault protection-UEF(earth fault protection downstream main circuit breaker). So an ACB with trip unit that can "do" UEF will solve this.
But UEF protections usually work at big values of currents (0,4-1)xIn. Not really sensitive.
If you have a tor, please indicate total current, seems to be lower than 6-800 A, and there are some round sensors on market, working together with differential relays. And protection is sensitive(0,03-5 A).