Cable Testing Specifications

[dasarmin]

I?m working up specifications for the installation and testing of cables for a ?Bid Specifications? document we provide to potential contractors. Below is an excerpt from the ?Termination and Testing? section.
? All circuits of voltage greater than or equal to 480VAC and having a current carrying capacity equal to or greater than 100 Amps or wire size equal to or greater than #4 AWG; shall be resistance tested between the current carrying conductors with a Meggar to 1000V prior to termination and energizing. The conductors must have a phase to phase resistance of greater than or equal to 5meg  and a resistance greater than or equal to 20meg W to ground. Results of resistance tests shall be documented and provided to Customer.

Note, I?ve specified 5meg and 20meg  for conductor to conductor and conductors to ground respectively. Would those numbers be considered acceptable for testing new cable installs?

I may also add procedures to test cables between Controllers (VFDs, Softstarts, etc) and Motors at less than 100 Amps and #4 AWG. But in these cases a Megger wouldn?t be required, only an Ohm Meter to confirm no Phase to Phase or to Ground shorts.

Looking for opinions or recommendations on such procedures or specifications.
Thanks

 

[zog]

Note, I?ve specified 5meg and 20meg  for conductor to conductor and conductors to ground respectively. Would those numbers be considered acceptable for testing new cable installs?

No, should be at least 100M per ANSI and NETA specs. And I would clarifiy that >480V part, once you get into MV cables it is a whole different world, Megger won't cut it anymore. View attachment Table 100.1.doc

 

[zbang]

I'd drop the "current carrying" part from "current carrying conductors" since the groundED conductor of a MWBC isn't always considered current carrying. Also, if you're going to specify voltages, use "voltage to ground" and "voltage to adjacent conductors" or something like that. Maybe "nominal system voltage".

It also seems unnecessarily wordy, but then I like plain-language specs.

 

[brian john]

Is their someone in your firm that is familiar with what is required and the standards that exist in the industry in lieu of SWAGING it. We run into EE's that attempt to do their own spec's all the time and generally they miss the mark.

 

[petersonra]

Is their someone in your firm that is familiar with what is required and the standards that exist in the industry in lieu of SWAGING it. We run into EE's that attempt to do their own spec's all the time and generally they miss the mark.

I am inclined to agree that referencing an existing standard that has proven the test of time is a better choice than trying to do your own thing. I would guess that a majority of people who make up their own things for this type of stuff just don't know that a standard even exists.

Not real surprising in this case, as NETA is not a well known organization, so it is not surprising that standards it publishes aren't real well known.

 

[brian john]

I am inclined to agree that referencing an existing standard that has proven the test of time is a better choice than trying to do your own thing. I would guess that a majority of people who make up their own things for this type of stuff just don't know that a standard even exists.

Not real surprising in this case, as NETA is not a well known organization, so it is not surprising that standards it publishes aren't real well known.

In todays market with the technology that is available by anyone with a PC, I would hope we all try to keep up to date by what is happening in our ever changing profession.

I'd bet 25% of the testing specifications I read are full of either unrealistic test or test that are less that industry standards. Have read some that were cut and paste, one set referenced polishing the switchgear with a Dupont car wax that has not been manufactured since 1952. The on site inspector said every other company could get the wax and we needed to.

Dupont representatives said BS and they reason the wax was no longer made was the newer waxes were a much better product.

 

[John120/240]

polishing the switchgear with a Dupont car wax that has not been manufactured since 1952. The on site inspector said every other company could get the wax and we needed to.

Dupont representatives said BS and they reason the wax was no longer made was the newer waxes were a much better product.

Polishing the switch gear ? Does this refer to polishing the exterior of the gear ? Who cares ?

I don't know are there internal parts that need polish for operation ? I think not but....

 

[zog]

Not real surprising in this case, as NETA is not a well known organization, so it is not surprising that standards it publishes aren't real well known.

True, but NETA derives thier specs directly from ANSI and IEEE, which everyone knows.

 

[brian john]

Polishing the switch gear ? Does this refer to polishing the exterior of the gear ? Who cares ?

I don't know are there internal parts that need polish for operation ? I think not but....

Polishing the exterior of the gear, it was in the specs and the EC that hired us for testing delegated that responsibility to us (and he paid for it), two coats of wax hand buffed, government inspector was suppose to witness the work.

 

[zbang]

About 30 years ago, when discussing contracting rates for different computer work ($35/hr for this, $50/hr for that, etc) , a colleague of mine said, "Heck, for $50 an hour, I'll even rake leaves". My rates for have gone up a bit since then, but if you want to pay for it, I'll polish the switchboard or rake the leaves. And for the right price, I won't sub it out, either .

 

[dasarmin]

Cable Testing

Cable Testing

I agree that using ANSI, NETA or any excepted organization?s specifications are the best way when trying to create procedures. But I don?t always find clear and definitive information to go with; that?s why I like this Forum so much and should probably use it more often. A lot of the procedures I find here have been (winged), the intent is there but not necessarily a paper or specification trail to validate.
Thanks for the information.