Testing Power factor correction caps

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cornbread

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I have places where we use 4160V PF correction caps. As part of our lock out tag out we check to make sure the cap is discharged by using a high voltage probe that fits our multi-meter. With said our procedure to test the circuit is verify your meter works, test the circuit, verify your meter works. With the lower voltages it easy to find something in the area so we can test. My question to this forum is how to verify, test, verify on high voltage CAP?:?
 
In a similar situation I have used a signal generator but that was with a non contact voltage tester.

Do the caps have a grounding switch or are you grounding them manually? We would usually let them sit for 5 minutes or so before grounding to let them bleed off stored energy.
 
Some have ground switches, but most have a internal bleed off resistors. Typically we wait 5 minutes before we check them. We use the high voltage probe and assume because it reads zero... we are OK.. back to the original question, we should be verifying the meter /probe is good. Not sure how would test the probe meter combination in the field? Looking for any suggestions on how other folks handle caps.
 
I've heard stories of guys being very seriously injured from using high-voltage multimeter probes on distribution equipment.

I can't explain the mechanism behind it because it seems like you'd be fine within the voltage rating, but I bet if you read the specs it says only for use on CAT II systems and very specifically warns against distribution circuit use.

We use a meter made by AB Chance designed for 15kV contact. Unfortunately it's much more expensive than a DMM probe.

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Make sure the meter is rated for the application
make sure the required ppe is worn

open the disconnect
wait 10 sec and measure across the caps
you will read something if the meter is working
read after 5 minutes and make sure it is 0
 
I really never figured out a good way to do this. We were not proceduraly required to perform a hot/cold/hot test on caps. We performed a hot/cold/hot check on the feeder supplying the caps. The feeder was grounded as required for circuits over 600V. The caps were left to sit for at least 5 minutes. The internal resistor should bleed stored energy in that time. At that point the caps were grounded either by integrated switch or manually. The grounds were lifted while testing.

A static discharge stick could be used with proper ppe and only after de-energized and following proper procedure. I am not sure but perhaps an approved version uses a resistor that would bleed the voltage in case an internal resistor failed.

As a possible solution to your direct question you could use an appropriate voltage source. I have never seen this done but you could set up a 5kv megger to verify your voltmeter.

Could you describe your volt meter setup in more detail? Perhaps you could setup a procedure in which you:
1. Set the meter to read resistance.
2. Short the probes and record reading.
3. Set the meter to read volts.
4. Check for presence of voltage on energized circuit.
5. De-energize circuit.
6. Wait 5 minutes.
7. Check for loss of voltage.
8. Set the meter to read resistance.
9. Short probes and record resistance.
10. Compare resistance values to verify probe integrity.

I know this is not the proper method but it would at least let you know the probe has not failed indicating a false 0V reading. Technically the meter should not be altered in any way between checks. This could also be dangerous as it introduces the risk that the meter is left in resistance mode.
 
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cornbread said:
Some have ground switches, but most have a internal bleed off resistors. Typically we wait 5 minutes before we check them. We use the high voltage probe and assume because it reads zero... we are OK.. back to the original question, we should be verifying the meter /probe is good. Not sure how would test the probe meter combination in the field? Looking for any suggestions on how other folks handle caps.
Click to expand...

We had a high voltage tester. It came with a verifying unit. You used it to verify that the tester was working before you used it. And, most importantly, after your tests to ensure that the tester was still working.
I don't know what max voltage it rated for. We didn't do anything above 11kV. From memory, it was about a meter (40 inches) long so I would not have used it for higher voltages anyway.
 
cornbread said:
I have places where we use 4160V PF correction caps. As part of our lock out tag out we check to make sure the cap is discharged by using a high voltage probe that fits our multi-meter. With said our procedure to test the circuit is verify your meter works, test the circuit, verify your meter works. With the lower voltages it easy to find something in the area so we can test. My question to this forum is how to verify, test, verify on high voltage CAP?:?
Click to expand...
Assuming you are using a hot stick?

Anyway, the Test-Verify-Test procedure doesn't mean you must test AT the same voltage level, just that the meter is working. So test it at a lower voltage, then check the cap voltage, then test it against the lower voltage again.

Biddle (Megger) makes a hot stick with a built-in tester by the way, I like those because when you are working on outdoor switchgear, you usually don't have another lower voltage easily available.
http://us.megger.com/phazing-tester/piezo-verifier/voltage-detector-detex
A built-in piezoelectric voltage source provides a test feature to ensure that the detector is operative before use. The self-test is activated by a pushbutton.
Click to expand...
 
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