Running power 4000 feet

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GoldDigger said:
I just extended that by assuming that the insulation for a conductor must be rated equal to or higher than the voltage to ground of that conductor.
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The closest I found was 110.4 which includes the sentence "The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected." That references "nominal voltage" rather than "voltage to ground." So are 300V conductors OK to use on 480Y/277 (the nominal voltage) because the voltage to ground is less than 300V?

As a practical matter, how does the voltage rating of insulation depend on insulation thickness? E.g. if the insulation thickness is doubled, does the voltage rating double? If so, then 300V conductors should be OK to use on 480Y/277.

Cheers, Wayne
 
wwhitney said:
The closest I found was 110.4 which includes the sentence "The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected." That references "nominal voltage" rather than "voltage to ground." So are 300V conductors OK to use on 480Y/277 (the nominal voltage) because the voltage to ground is less than 300V?

As a practical matter, how does the voltage rating of insulation depend on insulation thickness? E.g. if the insulation thickness is doubled, does the voltage rating double? If so, then 300V conductors should be OK to use on 480Y/277.

Cheers, Wayne
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My guess is most inspectors will reject 300 volt conductors used on a 480/277 system.

Possible that they shouldn't, but I think most will.
 
GoldDigger said:
Referring back to post #116....



Funny thing, I am home now!

Try Article 100, Definitions (underlining mine):



I just extended that by assuming that the insulation for a conductor must be rated equal to or higher than the voltage to ground of that conductor. I did not search for that part though.

I often look all over the code for a particular provision and then unexpectedly find it in the definitions. :)
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How hope it means that. In the POCO world its easy: either apply any given item to a wye grounded system, ie 25kv rated insulation can be applied 13.2/23kv Y system or de-rate by 1.73 for an ungrounded system. In fact cable can be purchased with 100%, 133% and 173% insulation:


http://www.okonite.com/engineering/technical_news/Tech_27.pdf


Hence my constant head scratching. The NEC is not clear about this distinction. So I guess my question is: 600 volt cable, what is the L-G rating? IF such cable can survive on a corner grounded delta, then it must be rated 600 L-G allowing an 1,200 volt L-L usage.
 
See 300.3(C)(1) and (2)

IMO they point to no.

If you try to use 600 volt insulation on 1000 volt circuit you will fail regardless of how you try to outsmart the system.
 
iwire said:
See 300.3(C)(1) and (2)

IMO they point to no.

If you try to use 600 volt insulation on 1000 volt circuit you will fail regardless of how you try to outsmart the system.
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Looks like you might be correct, 300.3 applies more to two voltages of different systems in the same raceway where it states "conductors shall have an insulation rating equal to at least the maximum circuit voltage applied", so I guess the intent is insulation must be rated for the line to line rather then line to ground voltage. But, I have a theory. They never say how the system is grounded, and it only technically applies to systems of 2 different voltages.


So this leads me to ask, what is the dielectric rating of 600 volt cable? 600/1.73=347 or 350 volts. If that is so, then how does THHN/THWN-2 survive a 600 volt corner grounded or ungrounded system? The insulation would have to be 600 volt rated L-G rather then L-L.
 
The UK has BASEC (British Approvals Service for Cables) who test and issue cables standards and conformity. <HAR> (HARmonised cable specification) is the umbrella organisation for Europe.

What is the US equivalent?
You should be asking them or the manufacturers about maximum voltage rating. You may get a definitive answer.
 
The US equivalent for electrical equipment and material standards is Underwriters Laboratories (UL), which is not a government entity.
Then either UL or any other Nationally Recognized Testing Laboratory (NRTL) can do the testing. No self certification by manufacturers as with CE is allowed.

UL was initially established and given its de facto authority by an association of fire insurance companies.
 
wwhitney said:
In this thread http://forums.mikeholt.com/showthread.php?t=152611 rbalex states "Per NEMA WC7/ICEA S-95-658, Section 1.3.2 it [the 600V rating] is the rated circuit voltage, phase to phase"

Cheers, Wayne
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Thank you, I will read it now. I still think 600 volts is just a label so that conductor can be used anywhere without second guessing. 600 volt cable is technically rated 600 volts to ground since it would not survive a corner grounded or ungrounded delta.
 
mbrooke said:
For now the plan is single phase. I saw somewhere in the NEC that 600 volts was raised to 1000 volts, what does this apply to in reality?
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My understaqnding of this is because of the PV guys--Where we currently use 600 volts,i.e., 600 volt and under solidly grounded system, would become 1000 volt and under---With No other changes
 
RichB said:
My understaqnding of this is because of the PV guys--Where we currently use 600 volts,i.e., 600 volt and under solidly grounded system, would become 1000 volt and under---With No other changes
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I think the code should take this approach everywhere. It makes the most sense, especially sine most everything today is solidly grounded.
 
mbrooke said:
I think the code should take this approach everywhere. It makes the most sense, especially sine most everything today is solidly grounded.
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There is no need to do that for standard circuits, no one seems to be having a problem with it.

There was a need to do that for PV systems.
 
GoldDigger said:
The US equivalent for electrical equipment and material standards is Underwriters Laboratories (UL), which is not a government entity.
Then either UL or any other Nationally Recognized Testing Laboratory (NRTL) can do the testing. No self certification by manufacturers as with CE is allowed.

UL was initially established and given its de facto authority by an association of fire insurance companies.
Click to expand...


BASEC and <HAR> are government bodies, nothing remotely like CE certification.
 
iwire said:
There is no need to do that for standard circuits, no one seems to be having a problem with it.

There was a need to do that for PV systems.
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Correct, but in this case such need exists. Phase to phase should not be the limiting factor, only phase to ground in the 600 volt and under listing. And it would make sense considering the US used to be a heavy delta user.
 
Tony S said:
The UK has BASEC (British Approvals Service for Cables) who test and issue cables standards and conformity. <HAR> (HARmonised cable specification) is the umbrella organisation for Europe.

What is the US equivalent?
You should be asking them or the manufacturers about maximum voltage rating. You may get a definitive answer.
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Tony, is this what the UK uses for max cable voltage?
 
That only shows single phase cables.

I was going to use 600/1000V 35mm² 4c SWA (cores doubled up) at 900V for this project but economics have stepped in.

3.3KV is far cheaper.
1700/3300V 16mm² 3c SWA instead of 600/1000V 35mm² 4c SWA makes sense to me. The cable is stock for the manufacturer. Installation is easier, 2 tons instead of 5½ tons, one joint instead of four.

I’m even going to raise the load capacity to 25KVA.

It would be a problem if I wasn’t “authorised” for MV work (up to 36KV).
 
I forgot to mention, there will be no switches at 3.3KV.
MV O/C and E/L will operate the LV MCCB via standard relays and C/T’s.

The job is heading towards £8K for 25KVA, the DNO (PoCo) want £16K for 15KVA.
 
Tony S said:
That only shows single phase cables.

I was going to use 600/1000V 35mm² 4c SWA (cores doubled up) at 900V for this project but economics have stepped in.

3.3KV is far cheaper.
1700/3300V 16mm² 3c SWA instead of 600/1000V 35mm² 4c SWA makes sense to me. The cable is stock for the manufacturer. Installation is easier, 2 tons instead of 5½ tons, one joint instead of four.

I’m even going to raise the load capacity to 25KVA.

It would be a problem if I wasn’t “authorised” for MV work (up to 36KV).
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How much does 3.3kv cable cost vs 0.6/1kv cable? Then again the copper saved would offset the thicker insulation.

Tony, I have a request. Can you make a vid terminating that cable? Im curious how its done, and how it would vary compared to the US. Further, I keep forgetting to ask. Those earth rods at the joint, what is the theory behind them? Are they code required?


As for the graph, my apologies, I am not familiar with IEC standards. :ashamed1:
 
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