Thanks Dpc, i will be cautious about x-ray radiation. But i think, it depends on the test voltage exceeding the latter will emit intolerable radiation and also with the distance of the personnel upon testing, the closer he is, the higher the radiation he have.
Dpc, it is a Westinghouse VCP - W.. Do you know the standard hi-pot testing procedure of this unit? I badly need it, since we haven't enough manual on this. So with, the vacuum replacement procedure manual.
Anyone can give me infos about his matter is highly appreciated!!
Im also thankful to the contributors of this thread!
The recommended DC hipot test value is 40kV for the VCP-W. It is a go no go test. Usually you will see less than 5 micro amps leakage but I have tested many with far more leakage and as long as it doesn't trip the test set it is considered OK. There is no x-ray health risk at 40kV with this breaker if you use a modern (manufactured in the last 20 years) hipot. You apply the potential to the top stab of a given pole and ground the other 5 stabs to the frame and the frame to an external ground (such as is available in the cubicle the breaker was removed from). You can run the voltage up to the rated (40kV) in a matter of seconds (watch the microammeter)and I believe they recommend holding it for one minute. A bad bottle (which is rare) usually fails before you get to 40kV and when we are testing them in quantity we seldom wait out the full minute.
PWR, "You apply the potential to the top stab of a given pole and ground the other 5 stabs to the frame and the frame to an external ground (such as is available in the cubicle the breaker was removed from)."
Do you mean there will be a three sets of testing as 1 test per pole? and obviously, does the interrupter contact is open while carrying the test? how i wish you further elaborate the procedure...
rbulsara, im glad you give me a copy of that stuff..
guys, how thankful i am with your contribution to this thread..
Yes, you test one vacuum interrupter or "bottle" at a time. The breaker must be open and the potential is applied across the open contacts inside the bottle. They are separated by a relatively small distance (on the order of 1/2 inch) which will only "hold" against that high a voltage if the vacuum in the bottle is basically intact. You can actually perform the test with only the bottom side of the pole being tested actually grounded. However, it is best to ground the line and load side of the other two poles at the same time because they usually will develop a significant "charge" during the test.
I am simply a tech but all our Vacuum Bottle units have a measurement tool to determine wear on the inaccessible contacts within the bottle. This check is in addition to a HI-Pot, we use 10kv because it is our highest setting and is all we got.
The Manual for your breaker is available online at eatonelectrical.com.
Test procedure is outlined in manual as follows:
With the breaker element open, connect all top primary
studs (bars) together and to the high potential machine
lead. Connect all bottom studs together and ground
them along with the breaker frame. Start the machine at
zero potential, increase to appropriate test voltage and
maintain for one minute.
A successful withstand indicates that all interrupters
have a satisfactory vacuum level. If there is a breakdown,
the defective interrupter or interrupters should be
identified by an individual test and replaced before placing
the breaker in service.
After the high potential is removed, discharge any electrical charge that may be retained. To avoid any ambiguity in the ac high potential test due to leakage or displacement (capacitive) current, the test unit should have
sufficient volt-ampere capacity. It is recommended that
the equipment be capable of delivering 25 milliamperes
for one minute.
Although an ac high potential test is recommended, a dc
test may be performed if only a dc test unit is available.
NETA ATS and MTS both recommends insulation resistance and overvoltage testing in strict accordance with manfacturer's recommendations with contacts open. Advises to take safeguard against X-radiation.
If this for a company or business, I suggest you have them buy the standards. If you let me know your email/fax I may be able to fax a page or two relevant to VCB testing.
