HRGU w/ Ground Fault Enabled on Breakers

[sesa366249]

Hi All,

Have you ever seen a High Resistance Grounded Unit System w/ ground fault enabled on breakers. What I know is with radial ground fault CT's in breakers, you cannot detect that small current (5-10A). You usually need to disable those CTs and have an external CTs with a relay. I need to know why is required sometimes to have GF protection on breakers with HRGU. HRGU is there to reduce the amount of current at the time fault occurs. Could you please describe how HRGU works scientifically with examples? I need to make sure I understand this system theoretical, please help! I also want to know why some want it with ground fault protection, you trip the breaker responsible on the zone where the fault happens? Why you need extra protection while HRGU can do it?

If this question does not belong to this discussion/division, please guide me to where I can have it answered. 

Thanks a lot,

[sesa366249 · Accepted solution]

Common in mining

the reason to trip is personnel protection

a person may be parallel to the v-g fault path

say your nrg is 10 A and ground loop R is 4 ohm

fram v would be 40 v and not extremely dangerous