Checking amps on 2400 volt motors

[Cold Fusion]

Even at $500 each it would be a bargain compared to paying out death benefits to the worker's next of kin. (cut).

I'd agree with that. I assume you are talking about the qualified person, on company time, getting in a car wreck on the way in - because that is likely the most dangereous part of the job.

(cut0 I am amazed that everytime I think someone can't possibly be so stupid, along comes a bigger stupe.

Yeah, that has always amazed me as well.

I also agree that the boss directing a person unfamiliar with the practices, equipment, and limitations, to do this job, is not very bright.

cf

 

[mxslick]

<snip> ...I assume you are talking about the qualified person, on company time, getting in a car wreck on the way in -......

Actually I was referring to the cost of the death benefits for the UNqualified person who gets fried when trying to get that measurement.

Either way $1500-$3000 for a qualified, properly trained and equipped technician to verify the accuracy of those CT's is not expensive in the grand scheme of things.

 

[Karl H]

Just out of curiosity,I understand WHY it would be dangerous to check
the Voltage of a 12kv system with a 600V meter.What would happen if you
checked the current of a 12kv system with a 600v amprobe.Other than a
false reading.what is the danger of just clamping an amprobe around a 12kv conductor?I'm not talking about insulation failure, just clamping a 600V amprobe around a energized 12kv CKT?Just curious.

 

[Pierre C Belarge]

It seems that most who have replied here have lost track of the OP's question/meaning of his question.


If someone asks about the method/safety of some type of testing or wiring method, it usually indicates the fact that they are not QUALIFIED to perform the operation. That in itself should stop them cold in their tracks. We can all explain "this and that" to him in our posts, but it does not change the fact that he/they are UNQUALIFIED. A QUALIFIED person should perform this task, as one misstep could be a last misstep.

 

[quogueelectric]

It seems that most who have replied here have lost track of the OP's question/meaning of his question.


If someone asks about the method/safety of some type of testing or wiring method, it usually indicates the fact that they are not QUALIFIED to perform the operation. That in itself should stop them cold in their tracks. We can all explain "this and that" to him in our posts, but it does not change the fact that he/they are UNQUALIFIED. A QUALIFIED person should perform this task, as one misstep could be a last misstep.

That in itself is the reason for all the new OSHA training courses that these laws are already in effect yet not enforced yet. Nfpa 70E Qualified person??? I think not. The old norm was a lineman worked tons of hours until he got electrocuted and then another one was hired to replace him as fast as he hit the ground.

 

[76nemo]

I won't repeat Pierre, but he said it to a tee.

The clamp most likely is rated CATIII at 600V's. NO test equipment was EVER designed or intended to surpass it's CAT rating.

 

[zog]

Just out of curiosity,I understand WHY it would be dangerous to check
the Voltage of a 12kv system with a 600V meter.What would happen if you
checked the current of a 12kv system with a 600v amprobe.Other than a
false reading.what is the danger of just clamping an amprobe around a 12kv conductor?I'm not talking about insulation failure, just clamping a 600V amprobe around a energized 12kv CKT?Just curious.

Thre is nothing wrong with it, the meter is not exposed to the voltage. The problem here is interference from the sheild and ground braid and possible flashover if he gets too close to the terminations. Other than that, no problem for a qualified person that knows what they are doing.

 

[nakulak]

Thre is nothing wrong with it, the meter is not exposed to the voltage. The problem here is interference from the sheild and ground braid and possible flashover if he gets too close to the terminations. Other than that, no problem for a qualified person that knows what they are doing.

I am confused.

If an instrument is rated for 600V, even if it is a clamp on instrument, are you saying that it is ok to take that instrument into the approach boundary of a voltage higher than the instrument is rated for to take measurements, as long as the instrument is not taking direct readings on the conductor ? I was under the impression that the reason for the voltage rating of the instrument was as a last resort, in the event that there is an accidental failure of the insulation on the wiring under test. Am I all wet ?

 

[Cold Fusion]

I am confused.

If an instrument is rated for 600V, even if it is a clamp on instrument, are you saying that it is ok to take that instrument into the approach boundary of a voltage higher than the instrument is rated for to take measurements, as long as the instrument is not taking direct readings on the conductor ? I was under the impression that the reason for the voltage rating of the instrument was as a last resort, in the event that there is an accidental failure of the insulation on the wiring under test. Am I all wet ?

Per (2009) NFPA 70E, T130.2.C, for 751V to 15kv (phase to phase):
limited approach boundry = 2.2 feet
restricted approach bondry = 7 inches

Another post has already discussed industry practice of using 600V CTs on MV systems - I won't repeat that.

Arc flash is a separate issue and likely has diferent distances involved. However, the OP was clearly not walking into an arc flash area and puting on a clamp-on.

As for standing next to (with-in the restricted boundary) a clamp-on, at an energized, open, 2400V motor connection box with exposed buses - I wouldn't, but the 600v clamp-on is not part of the reason.

cf

 

[hockeyoligist2]

Sorry to be so long in getting back to this thread. I have been out of work due to medical reasons and didn't know what actually ever came about with the test. After I forwarded the posts from all of you to my coworker, he printed it out and presented them to the boss. The boss "rethunk" and brought in a contractor with the right equipment to do the test.

Thanks to all for the support!

 

[mxslick]

Thanks for the update, hope your medical issues are behind you.

Especially glad to hear your boss did the right thing!!

 

[zog]

Sorry to be so long in getting back to this thread. I have been out of work due to medical reasons and didn't know what actually ever came about with the test. After I forwarded the posts from all of you to my coworker, he printed it out and presented them to the boss. The boss "rethunk" and brought in a contractor with the right equipment to do the test.

Thanks to all for the support!

Good to hear, tell your boss we are proud of him.

 

[donselectric]

good thing.....can you spell OSHA....

 

[weressl]

Actually from a safety aspect that will work fine, you can shut the motor down, hook up your meter, turn the motor on and you will read 0 Amps. A clamp on meter won't work on that cable if it is sheilded, which it probally is.

There is a better way to do it but you will need to provide more info about the system, no meters in this system?

2400V motor leads are seldom shielded. If the termination is properly installed the current can be measured past the shielding termination over the stress-cone. The motor leads shall be fully insulated presenting no different or additional hazard than measuring current on a 480V motor.

An electrician should be fully aware of this.

 

[weressl]

I won't repeat Pierre, but he said it to a tee.

The clamp most likely is rated CATIII at 600V's. NO test equipment was EVER designed or intended to surpass it's CAT rating.

The CAT rating refers to voltage measurements, it is IRREVELANT for current measurements.

 

[weressl]

Per (2009) NFPA 70E, T130.2.C, for 751V to 15kv (phase to phase):
limited approach boundry = 2.2 feet
restricted approach bondry = 7 inches

Another post has already discussed industry practice of using 600V CTs on MV systems - I won't repeat that.

Arc flash is a separate issue and likely has diferent distances involved. However, the OP was clearly not walking into an arc flash area and puting on a clamp-on.

As for standing next to (with-in the restricted boundary) a clamp-on, at an energized, open, 2400V motor connection box with exposed buses - I wouldn't, but the 600v clamp-on is not part of the reason.

cf

Distances refer to uninsulated, exposed energized components. Fully insulated energized components have no distance limitation.