impedence grounded
- Thread starter plt
- Start date
- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: impedence grounded
See 250.36. This system cannot be used for line to neutral loads, it is only for line to line loads. A resistor or reactor is placed between the transformer XO and the grounding electrode system. This system can maintion power with a single ground fault as the impedance limits the ground fault current to a low value, often less than 10 amps. The system continues to work after a single ground fault, but if there is a second ground would occur on a different phase you will have a line to line fault.
Don
See 250.36. This system cannot be used for line to neutral loads, it is only for line to line loads. A resistor or reactor is placed between the transformer XO and the grounding electrode system. This system can maintion power with a single ground fault as the impedance limits the ground fault current to a low value, often less than 10 amps. The system continues to work after a single ground fault, but if there is a second ground would occur on a different phase you will have a line to line fault.
Don
Re: impedence grounded
Don gave you the code, I would like to expand a little. A resistance or impedance grounded system is used where 3-phase, 3-wire critical load is much larger than single phase loads requiring a grounded conductor. Single phase loads will require an additional solidly grounded transformer.
This might have you asking why not just use a delta service. The answer would be a impedance or resistance grounded system shorts out the capacitance coupling to ground, and stablizes system voltages with respect to ground. This in turns reduces stress to cable insulation, other electrical components, and extends system life.
Don gave you the code, I would like to expand a little. A resistance or impedance grounded system is used where 3-phase, 3-wire critical load is much larger than single phase loads requiring a grounded conductor. Single phase loads will require an additional solidly grounded transformer.
This might have you asking why not just use a delta service. The answer would be a impedance or resistance grounded system shorts out the capacitance coupling to ground, and stablizes system voltages with respect to ground. This in turns reduces stress to cable insulation, other electrical components, and extends system life.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: impedence grounded
What type of buildings would use the high impedance grounded system? Anything to considers its power to be crucial?
What type of buildings would use the high impedance grounded system? Anything to considers its power to be crucial?
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: impedence grounded
Bussmann's web site has some really nice power point slides on this type of thing. In This presentation it shows what happens (in diagram format) with a ground fault on all sorts of different systems. Its about a 2.5MB download, so if you have a dial-up it might take a few minutes. Worth the wait though, in my opinion.
Bussmann's web site has some really nice power point slides on this type of thing. In This presentation it shows what happens (in diagram format) with a ground fault on all sorts of different systems. Its about a 2.5MB download, so if you have a dial-up it might take a few minutes. Worth the wait though, in my opinion.
- Location
- Illinois
- Occupation
- retired electrician
Re: impedence grounded
Ryan,
This type of system is used mostly in industrial plants and places like utility generation plants, waste water treatment plants and similar occupancies.
Don
Ryan,
This type of system is used mostly in industrial plants and places like utility generation plants, waste water treatment plants and similar occupancies.
Don
Re: impedence grounded
Yes. Anyplace where outages from L-G faults cannot be tolerated. Some more examples would be refinery, extrusion, induction furnace, pharmaceuticals, or any process where a interruption in service would cause re-tooling or excessive loss of production or product.
Re: impedence grounded
Another 2 cents worth is, it limits single phase to ground fault damage. It can either trip the component or allow an orderly shut down to find and repair a single phase to ground problem. The damage from a 5 or 10 amp fault at 10000 volts is much less than 100000 amps at 10000 volts.
Another 2 cents worth is, it limits single phase to ground fault damage. It can either trip the component or allow an orderly shut down to find and repair a single phase to ground problem. The damage from a 5 or 10 amp fault at 10000 volts is much less than 100000 amps at 10000 volts.
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