charlie
Senior Member
- Location
- Indianapolis
Re: Primary cut-outs
Don, I didn't catch Bennie's comment about SDS so I didn't address it.
Don, I didn't catch Bennie's comment about SDS so I didn't address it.
Primary cut-outs
- Thread starter ryan_618
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Re: Primary cut-outs
PGE, Idaho Power, So.Cal Edison, Pacific Power and Light, LA Metro-Power all use the MGN distribution system.
An ungrounded delta/delta is sometimes inserted to break the MGN current path.
The delta/delta makes the downstream system separately derived.
PGE, Idaho Power, So.Cal Edison, Pacific Power and Light, LA Metro-Power all use the MGN distribution system.
An ungrounded delta/delta is sometimes inserted to break the MGN current path.
The delta/delta makes the downstream system separately derived.
Ed MacLaren
Senior Member
Re: Primary cut-outs
Both can only flow over paths that return to the transformer that they originated from.
Ed
The only difference between load current and fault current is that the latter has "escaped" from it's intended path, and it's magnitude is determined by the impedance of that fault path.
Both can only flow over paths that return to the transformer that they originated from.
Ed
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Primary cut-outs
[ March 14, 2004, 03:22 AM: Message edited by: hurk27 ]
Now at primary voltages Earth would be a conductor would it not? Even though you have a delta to delta isolation you would still have a Earth ground that would still be common between the two systems. so if the grounding at high voltages is common and you have a SDS system then why can't we have grounding be common at 240 volts and still have an SDS system?
[ March 14, 2004, 03:22 AM: Message edited by: hurk27 ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Primary cut-outs
In other post you have said one of the reasons that you don't accept that a generator is a SDS is because of the EGC connection which is not switched. But here you described a delta to delta as a SDS even though it has a grounding conductor between the both sides of the transformer. and that is earth which at the voltage of this system would be a conductor. But the reason this connection won't matter is because current returns to source as it would on a generator?
In other post you have said one of the reasons that you don't accept that a generator is a SDS is because of the EGC connection which is not switched. But here you described a delta to delta as a SDS even though it has a grounding conductor between the both sides of the transformer. and that is earth which at the voltage of this system would be a conductor. But the reason this connection won't matter is because current returns to source as it would on a generator?
Re: Primary cut-outs
All I can say is to repeat this statement;
All material is electrically connected, the resistance of the connections route the current to the desired location.
Remember all electricity can do is two things, generate magnetic fields and heat.
Electricity is basically dumb, My old three legged dog does three things.
All I can say is to repeat this statement;
All material is electrically connected, the resistance of the connections route the current to the desired location.
Remember all electricity can do is two things, generate magnetic fields and heat.
Electricity is basically dumb, My old three legged dog does three things.
Re: Primary cut-outs
An ungrounded delta to an ungrounded delta, is not electrically connected between windings.
An ungrounded delta, to a grounded wye, is the power source for a premises wiring system without external connections.
A grounded delta to an ungrounded secondary is an isolation transformer.
An ungrounded delta to an ungrounded delta, is not electrically connected between windings.
An ungrounded delta, to a grounded wye, is the power source for a premises wiring system without external connections.
A grounded delta to an ungrounded secondary is an isolation transformer.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Primary cut-outs
Boy I got to quit trying to post at these late hours. I don't know what I was thinking. I think what I was trying to get at is lets say you have a distribution line running down a long road. and you have a delta/Y to a service at a building. Now about a mile father down this road you have the delta to delta SDS. Then a half mile father down you have another delta/Y even though you have the delta/ delta SDS the two Y transformers would still have a common conductor between them. This would be earth. if the voltage is let's say 14.4 KV the fault current on earth could be as high as 576 amps@25 ohms of course with a delta/delta the current would stop there unless there was a winding to winding fault too. but with a SDS generator this would be true also, the fault current would stop at the generator?
[ March 14, 2004, 10:51 PM: Message edited by: hurk27 ]
Boy I got to quit trying to post at these late hours. I don't know what I was thinking. I think what I was trying to get at is lets say you have a distribution line running down a long road. and you have a delta/Y to a service at a building. Now about a mile father down this road you have the delta to delta SDS. Then a half mile father down you have another delta/Y even though you have the delta/ delta SDS the two Y transformers would still have a common conductor between them. This would be earth. if the voltage is let's say 14.4 KV the fault current on earth could be as high as 576 amps@25 ohms of course with a delta/delta the current would stop there unless there was a winding to winding fault too. but with a SDS generator this would be true also, the fault current would stop at the generator?
[ March 14, 2004, 10:51 PM: Message edited by: hurk27 ]
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