MCB with PT

[unnikri57]

Is it advisable to put MCB in the circuit between the PT and RYB indicators in the MV switch gear.In case the MCB trips it will give a false indication that the incomer voltage is not present

 

[bacon4life]

I am not sure what you mean by RYB indicator, but please consider what will happen if there is a short circuit between PT and the RYB indicator or fault inside the RYB indicator. I do not recall ever seeing the secondary of a PT directly connected to an instrument with a fuse or breaker as the first device after the PT.

 

[RRaghunath]

I suppose RYB indicators to be closest to the PT secondary terminals. Thus, the MCB or fuse comes after the indicator always.
This way, in case of a fault, the healthy phase indicators continue to glow.

 

[waross]

Anecdote alert.
A very long time ago, in a sawmill that was very old then;
The supply was ungrounded delta.
The switchgear had three lamps connected line to ground to detect ground faults.
A lamp went out.
An electrician looked for the ground for two days.
Sometime on the third day, he came into the shop, muttering bad words under his breath and threw his tool belt on the bench.
The boss asked;
"Did you find the problem."
Yes, #$^*&^$@$^^. I found it."
"What was wrong?"
"The damm lamp was burned out."
My immediate thought;
"I am so glad that was him and not me." grin