Paralleling of Wye-Connected & Delta-Connected Generators

[GRAEE]

Is it possible to operate generators in parallel which are connected in wye & delta? Assuming that all general requirements are met except that of their configurations..

thanks in advance

 

[waross]

Our little plant ran for years with two 600 kW wye machines and three 350 kW delta machines that were paralleled as needed.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[GRAEE]

Are there any disadvantages/advantages when paralleling wye & delta over wye & wye connected generators?

 

[waross]

Our system was ungrounded when only the delta machines were running. Fortunately we never had a problem but we could have had serious problems. We were feeding a delta wye transformer bank so the ungrounded portion of the system was just the loop from the generators to the transformer bank.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[GRAEE]

Waross, thanks for the valuable information.

How do you protect the delta-connected generator from ground faults? Since, it has no zero sequence current.

Regards,

 

[waross]

When the load was very light, such as small hours of the night in cool weather (No A/C units running) there may be only one 350kW delta unit on line, and the generator, control panel and transformers would be an ungrounded system. This was not a frequent occasion. Any time that the load was above about 300kW, a 600 kW wye generator would be online and provide grounding. Ground protection was provided by the generator breakers. This was two old second hand plants cobbled together into one. About the only protection was the generator breakers. This is common with the diesel plants that I have spec'ed, installed and repaired. To put this in perspective, the range of sets that I have been exposed to is from about 14 KVA, single phase to 1500 KVA, three phase.
If your sets are above 1000 KVA you probably want some advice from the fellows who work with the large sets such as ScottyUK.

Bill
--------------------
"Why not the best?"
Jimmy Carter