Reverse feeding power transformer 1250kVA 20/0.4kV Dyn11

[LDKGR]

Dear all,

I have a project in which a Genset has to feed a 20kV line. My first option is to use a step down transformer in reverse feeding connection. I am waiting your comments on this solution.

Thanks in advance.

 

[dpc]

The transformer doesn't care what direction the power is going. There are some subtle differences in transformer designed specifically for generator step-up applications, but a standard transformer will work fine.

 

[LDKGR]

Hi dpc,
thank you for your reply. Can you send me a table with these differences ?

 

[Mbrooke]

If I am not mistaken inrush may be greater if reverse fed.

 

[LDKGR]

Mbrooke you are right. Inrush current is greater. Moreover if you have 1-Phase loads currents will be in neutral. This will be a problem if you have Dyn solidly grounded transformer, but I am waiting for further information ...

 

[dpc]

I don't have a table. I'd recommend talking to a transformer manufacturer if you have further concerns.

 

[Marmite]

Worry less about the transformer, and worry more about system grounding and protection for faults on your 20kV line.

Regards
Marmite

 

[LDKGR]

Marmite, do you mean L-G fault? Do you believe that I should use a "special" protection ?

 

[Borti]

I agree with marmite, line to gnd fault on the 20 kv line is probably the biggest concern. I assume that the line would have some kind of effective grounding, and an ungrounded source is introduced by connecting a generator through a transformer with delta primary. Your line protection should trip the transformer or the generator (depending on the configuration) on any line fault and an open corner delta or similar neutral displacement protection could be used as a backup.

 

[LDKGR]

Borti, can you send me more details ?

Thanks