open delta

Dear Friend

In midium voltage networks ( 33KV,66KV etc), Neutal displacement protection is provided. Neutral displacement protection relay is actuated by voltage of Open delta ( Primary is star and Secondary is open delta) winding of 3-ph, P.T.

So i suggest you go through protection hand book of GE Power/ABB or any good text book on Generator protection.

Bhushan

Open delta winding is able to detect the homopolar component in a three phase network. This component in voltage is given by ground faults. A medium voltage network is able to operate with a grounded phase for a while; the other two phases shall suffer overvoltage. If a generator is conected on a medium voltage busbar, an overvoltage may be dangerous for the ground insulation and this is a way to find out if occurs.

Dear all,

I think the PT connection here should be called broken delta, since open delta is defined as:

"A connection similar to a delta-delta connection utilizing three single-phase transformers, but with one singe-phase transformer removed.... " in IEEE 100.

Regards

open delta means two side of winding is opened and resultant voltage across open terminal is approximately zero due resultant vector sum of voltage