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delta system

delta system

delta system

(OP)
we have a 240v delta system 3 wire how do you get a neutral
we have it to ground been fine for years a least 18. now we have unbalaced power to ground it is 147  195  94 volts  changed the grounds didnt help penelec don't even no way

RE: delta system

I have some difficulty understanding what you are saying. Do you have an ungrounded 240 V system with delta connection? And now you measure those voltages from the phases to ground?

It doesn't seem to be a problem to me. No severe unbalance - you have to expect anything between almost zero and full line/line voltage in such a system.

Is your question how to ground it? If that is the case then you obviously cannot ground the transformer center point to get a 240/138 V system. But - if your country's code permits - you can ground one of the phases and get a grounded delta with 0, 240, 240 V from line to ground. It is being done in the US and it really doesn't change much. Only that a ground fault in one of the hot phases will trip the corresponding fuse, which could be good.

I think that more and clearer information is needed before anyone can give advice here.

RE: delta system

A delta system has no neutral. There are several ways to get a neutral. If you need three phase, you can install a delta-wye transformer. This will give you a 3-phase 4-wire system as output and you can select whatever secondary voltage you want.

Another option if you need a small amount of 120/240 volt single-phase power may be to have the utility convert the service to a 240 volt "high leg" system where a center tap of one of the three transformers (or transformer windings) is grounded. This effectively adds a 120/240 single phase connection using two of the three 240V phases and the added 'neutral'.

Theoretically you can ground one phase of the existing 3-wire system, converting it to what is called a 'corner grounded' system, but that doesn't give you any other voltages to use.

RE: delta system

I have also used a balance coil to convert a 3-wire dry transformer secondary to 120/240 volts 4-wire delta. This is a single phase version of a zig-zag set that is used to convert a 3-wire delta system into 4-wire wye.

Send me email mc5w at earthlink dot net if you want details as to how to protect a balance coil or zig-zag set against overloads and internal faults. Ordinary circuit breakers or fuses will not work.

Mike Cole

RE: delta system

With ungrounded delta power systems we have added Phaseback to our power system and our phase voltages are now balanced to ground and our overvoltage problems stopped. The link is: http://www.applied-energy.us

I hope this helps
Bill

RE: delta system

By the way, Penelec is in the U.S. and is a part of First Energy. They cover both upstate PA and NY along the PA-NY border. They also cover part of central PA. I am not sure of what their name is in upstate New York, but I do know that their transmission and subtransmission lines do serve loads in upstate New York.

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