grounding fault in LV network
grounding fault in LV network
(OP)
Guys,
We usually use HRG for LV networks which limits the grounding resistor current to 5A-25A.
If we take a 3A charging current into account, all ground grid can see in LV network is 25A+3A=28A ?!
This number looks low for designing a ground grid but it is all can flow through ground path right?
We usually use HRG for LV networks which limits the grounding resistor current to 5A-25A.
If we take a 3A charging current into account, all ground grid can see in LV network is 25A+3A=28A ?!
This number looks low for designing a ground grid but it is all can flow through ground path right?






RE: grounding fault in LV network
http://www.postglover.com/download/neutral-groundi...
RE: grounding fault in LV network
RE: grounding fault in LV network
With regards to the low-voltage system, you should also consider the possibility of a second fault occurring on a different phase, which would result in phase-phase fault currents flowing within your facility ground grid conductors. Unlikely you say? Consider that when the first ground fault occurs, it raises the voltage to ground on all of the other equipment connected to the system, which might just be enough to finish off anything that was just hanging in there before.
Note also that the grounding resistor in the local transformer does not need to be sized with consideration to either of the above.
Cheers,
mgtrp
RE: grounding fault in LV network
RE: grounding fault in LV network
RE: grounding fault in LV network
Because of delta/delta transformer, there is no ground current in the secondary.
RE: grounding fault in LV network
The old rule-of-thumb is 1A for every MVA of transformer capacity. [ie In a typical industrial environment, a 2A resistor should be adequate for a LV 2MVA xfmr).
GG
"Wish I didn't know now what I didn't know then." -- Bob Seger