1.Whats the use of GNAC(Generator Neutral Accessory
Compartment)

2. why generator or any other system require Neutral
Grounding and not Phase grounding

3. what happens if any one of the phase is grounded.

4. if 15kv is grounded directly what will happen, why it
should not be grounded like that

5. use of of NGTR(Neutral Grounding Transformer and
Resistor) for grounding is helpfull and how

Answer Posted / jax

1. To keep Neutral side CT (Differential CT, NCT, Measuring
CT, Cross current CT, Isolator switch, etc.

2. Phase can be grounded by isolating neutral. But the main
aim of grounding can not be achived. The potential
difference between ground and other two phase (ungrounded
phase) will raise to line voltage.

3. It depends on the type of grounding. For ungrounded
system no faulr current will flow. But the potential
difference between ground and other two phase (ungrounded
phase) will raise to line voltage. For Solidly grounded
system phase to ground fault current will be high. For Low
resitance grounding, phase to ground fault current will be
quiet less. For High resistance grounding, phase to ground
fault current will be very low. (I can explain more about
this).

4. Simple. Phase to fault current will be more.

5. Using NGTR single phase to fault current can be reduced.
Because of this stress on the conductor due to fault
current can be minimized. But the stress on insulator is
increased because of rise in phase to ground potential
during fault.

For any doubt in Electrical you can contact me at
jaxp333@yahoo.co.in

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