Parallel Transformer

On what fault the relay is tripping? Over current or Short Time Delay or Instantaneous or Ground fault?

Why the relay is always tripped for a case of supposition? Reading your post, between fact and theory, I know you are in the middle.

And how was the failed transformer removed from service, automatically or manually? Have you looked at the inrush current and factored that in to your protective scheme?

You can use a protection relay which it has two different protection settings and you can switch by an input.

hello

I think you should change your relay settings if it is flexible enough!

Dear all,

Thanks for all of your quick response. I'm on the way to site, it's a 2 days travelling, and I will provide the detail info ASAP.

I posted the questions earlier, in case someone had already the same experience.

Regards..

Of course, you should better do that. Because if you could imagine that when one of the transformer fails (it burns because of the short-circuit in windings), do you still think the relay should still keep the power continuous?

Dear all,

The relay that tripped was Instantaneous. And the switching between the two transformers is done manually.

Can I just adjust the relay setting?

If you get sick, before the doctors give you some medicines. They will ask you about your sickness.

Same as here, we don't know what failure you experienced from the transformer. How we can decide to adjust or keep the setting?

Its crystal clear that it was caused by instantaneous tripping, or sympathetic tripping. I am calculating the new setting, and I will key them as soon as possible. After that I will try to switch the state to see the result

Ok, I initially thought that the transformer has been failed. Sorry. You are doing the commissioning, aren't you?

What kind of relay you are using? It may cause by inrush current which is described many times in this forum.

As I know, the relay has two protection method, one for inrush current (10 times than the normal current) one for normal operation. Could you clarify with the supplier for this? Consult the switchgear supplier for more details on this.

If not, you can slightly adjust the relay to ride over the surge of state changing. I hope thing would be Ok.

Let us know what you find there.