ngr groundEd system vs solidly grounded system

Still Homework not solved?

NGR- neutral Grounded resistor (resistance = The resistor value)

Solidly Earthed - theoritically Zero.

Why do you want the resistance ? there must be a reason for it to exist. What it does? (Hint - limit something) - why do you want to limit it?

Solidly earthed too do exist - in certain applications and both are complimentary - why would you not want to limit the parameter ?

Ponder, sufficient hints.

The plant where i work has solidily grounded distribution transformers-1600KVA rating. I was wondering why they did'nt go for ngr system, would'nt it provide better protection!!!!!

Is it the neutral that is solidly grounded or it is the body ?

The neutral of the distribution transformer of'course

Sufficient and efficient protection systems can be provided for both kinds of grounding. In India normally at the distribution level solidly grounded systems are used and NERs are provided at higher voltage levels and at generation systems.

I think i am gonna have to agree with you on that.

I am not sure that you should have solidly grounded neutral - that's why i wanted to confirm that it is not the body.

1.6MVA is a quite big one, and the earth fault current will be a bit difficult to control.

In India, at low volatge level (433V) you MUST do only Solid Earthing of the system neutral. This is by IE Rules 1956, Rule No. 61 (1) (a). Because, if you opt for impedance earthing, during an earth fault, there will be appreciable voltage present between the faulted body & the neutral, the magnitude of this voltage being determined by the fault current magnitude and the impedance value. This voltage might circulate enough current in a person accidentally coming in contact with the faulted equipment, as to harm his even causing death. Note that, LV systems can be handled by non-technical persons too. In solid earthing, you do not have this problem, as at the instant of an earth fault, the faulted phase goes to neutral potential and the high fault current would invariably cause the Overcurrent or short circuit protection device to opearte in sufficiently quick time before any harm could be done.

k sir, i agree, but then why we solidly grounded in Generator transformer. GT is very high capacity. LV System - Solidly Earthed

MV system - NGR or NGT earhing

HV system - Effectively earthed system( Same as Solidly grouned)

Why we go to Solidly grouned for HV System.

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