transformer connections
- Thread starter jdr
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ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: transformer connections
Yes, but you must bring that neutral to the main disconnect and terminate it there. You do not have to continue it through the distribution system if you don't need it.
Yes, but you must bring that neutral to the main disconnect and terminate it there. You do not have to continue it through the distribution system if you don't need it.
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
Actually, you do not have to take the neutral if you do not ground it or use it as a conductor. You may use the secondary as either an ungrounded delta (3? only with no neutral) or a corner grounded delta (again with the neutral not grounded or brought out).
Actually, you do not have to take the neutral if you do not ground it or use it as a conductor. You may use the secondary as either an ungrounded delta (3? only with no neutral) or a corner grounded delta (again with the neutral not grounded or brought out).
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
That would be your choice since a fault could only be from phase to phase with and ungrounded voltage. A phase to ground will do nothing except establish the first grounding point.
That would be your choice since a fault could only be from phase to phase with and ungrounded voltage. A phase to ground will do nothing except establish the first grounding point.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: transformer connections
It would also depend on whether or not the NEC would permit the system to be ungrounded, as per 250.20
It would also depend on whether or not the NEC would permit the system to be ungrounded, as per 250.20
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
Ryan, if it is a 480 wye, it may be ungrounded if the neutral is not used as a circuit conductor. Also, under those conditions, you can "corner ground" this configuration.
Ryan, if it is a 480 wye, it may be ungrounded if the neutral is not used as a circuit conductor. Also, under those conditions, you can "corner ground" this configuration.
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
Part II of Article 250 covers circuit and system grounding. 250.20(B) tells you what systems from 50 to 1000 volts that are required to be grounded. Any other system that does not meet those requirements in that voltage range is not required to be grounded but are permitted to be grounded.
If you wish to be totally technical, you really have to start with 250.21 which refers you to 250.20(B). And then there is 250.22 that lists circuits that are not to be grounded.
Part II of Article 250 covers circuit and system grounding. 250.20(B) tells you what systems from 50 to 1000 volts that are required to be grounded. Any other system that does not meet those requirements in that voltage range is not required to be grounded but are permitted to be grounded.
If you wish to be totally technical, you really have to start with 250.21 which refers you to 250.20(B). And then there is 250.22 that lists circuits that are not to be grounded.
kturner
Member
- Location
- East Tennessee
Re: transformer connections
Wouldn't 250.24 require that the neutral be brought to the service disconnect even though
it won't be used in the premises wiring ?
Wouldn't 250.24 require that the neutral be brought to the service disconnect even though
it won't be used in the premises wiring ?
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
250.24(B) Grounded Conductor Brought to Service Equipment. Where an ac system operating at less than 1000 volts is grounded at any point . . .
If it is not grounded, it is not required to be used. The same rules are in the NESC so an electric utility may provide an "ungrounded delta" or a "corner grounded delta" from a wye connected bank. the bottom line is that it is up to the electric utility.
250.24(B) Grounded Conductor Brought to Service Equipment. Where an ac system operating at less than 1000 volts is grounded at any point . . .
If it is not grounded, it is not required to be used. The same rules are in the NESC so an electric utility may provide an "ungrounded delta" or a "corner grounded delta" from a wye connected bank. the bottom line is that it is up to the electric utility.
charlie
Senior Member
- Location
- Indianapolis
Re: transformer connections
But to answer your question, normally no. Most electric utilities have sufficient transformers to build their standard configurations and will use full voltage transformers to build a delta configuration. We do not even offer an ungrounded service anymore.Originally posted by charlie:
the bottom line is that it is up to the electric utility.
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