Transformer inrush 2

[alimt]

We have the 2 units Interbus transformers (IBT) 90MVA, 275/150KV, 2 winding at the substation where the substation is supplied from hydro power plant with a 275KV transmission distance of 200km.
While IBT-1 was energized with voltage at HV side is 265 KV, voltage at LV side is 155KV and load 51 MW at LV side, when we energize IBT-2 by closing HV side CB the diff protection relay IBT-2 trip with Id=0.98Ie and at the same time Uninterruptible power supply (UPS) at Power plant fail.
whether when we energize HV side IBT-2 occur inrush that could cause diff protection trip and UPS at Power plant fail ?

 

[PHovnanian]

The UPS failed? What sort of fault code or failure did it display?

Without more info. this is a puzzle. The UPS failure* sounds like a ground voltage transient resulting from the switching. Some details about the transformer connections, grounding, surge protection, relay types and the connection of the station service (where the UPS is fed from) might help.

*Could be a bad UPS that just crapped out when it had to pick up load during transformer switching. Or not.

 

[Bronzeado]

Dear alimt,

Could you, please, give more detail about differential protection operation, i.e., supply the "oscilograms" from the relays?

Best Regards,

Herivelto S. Bronzeado
Ministério da Integração Nacional - MI
Brasília, Brazil

 

[alimt]

Thanks mr. PHovnanian

UPS feed from the station service transformer (Please find the attached file of single line diagram).

 

[alimt]

Thanks mr. PHovnanian & Bronzeado

UPS feed from the station service transformer (Please find the attached file of single line diagram. Actually the UPS not totally fail the UPS just blink, after we change the source using diesel generator set the UPS become normal.
we had difficulty to copying oscillograms from the relay, we hope that we can copy oscilogram later

 

[RAMConsult]

I believe what you meant was that the "..UPS failed to continuously supply power..." For that you need to look at exactly the type of UPS you have, i.e., whether it is on-line, line-interactive, standby, or some combination of the above. Basically if the AC input is directly connected to the output then you have either line-interactive or standby, in which case there may be a slight delay/sag as the inverter picks up the load. If the AC input has no direct connection to the output but instead is rectified to charge the batteries which then feed an inverter which continuously supplies power directly to the output, then there is no delay since the inverter is always supplying the load regardless of what the AC source is doing. The topology of your particular UPS will determine how it handles the loss of source power.

 

[alimt]

UPS have 3 inputs consist of : 230Vac, 400Vac 3phase & 110Vdc the output of UPS is 230 Vac 50Hz (please see the attach files). The AC inputs are feed from the same station service transformer.