Will open delta voltage comes while flowing negative sequence voltage in the system. Two phases are changed from generator supply like RBY instead of RYB. Is this the reason of getting open delta voltage.?

Balaji,

No, changing the phase sequence does not "cause" negative sequence currents to flow, it just causes your 3 phase motors to run backwards and/or affects any phase order sensitive relaying that you may have. You get open delta voltage because the three line/phase voltages (regardless of their phase sequence) are no longer equal in magnitude and 120 degrees apart; i.e., there is an imbalance somewhere in the system.

Alan

Mr. Alan,

changing the phase sequence also the reason for negative sequence na?

Balaji please help me hear. What do you refer to as open delta voltage.

The open delta voltage will comes only absence of anyone phase of the three. My point is whether that voltage will comes or not while the presence of all three voltages with wrong phase sequence like RBY.

Thus the absence of one phase is the unbalance of the system and the wrong phase sequence also the unbalance of the system. This is because the phase sequence will be disturbed in both condition.

My doubt is the second condition will possible or not?

I think you are misunderstanding something, as open delta is a transformer bank configuration. and if a 3-phase transformer looses a phase it is called single phasing, and you will get circulating voltage readings if the equipment still connected while testing.

So to which are you referring

I am asking for open delta voltage protection in PT. That means the secondary of all three phase PTs are connected in series and makes open delta connection.