I think they are refering to an AC hipot, vs DC Hipot. Generally to test the breaker you megger it, then to see if the vacuum is in the bottles the bottles are hipoted. They recommend AC though DC can be used. See the manual for voltage levels. The vacuum bottles I have found bad were found with a 5kV megger, it looked ok at 2.5kV, but showed bad at 5kV. Generally the levels they recommend are about 40kVDC across the bottles.
pwrengrds is right but I need to add the caution of X-rays being emmited during this test, the area should be roped pff and signs posted during the test, check the inst book for the safe distance but it is usually 4 ft.
I would say if you dont own a Hipot you have not done this type of testing before and are not qualified to do this test, you may want to consider a qualified testing agency, this test will cost you less than the hipot rental. You also need to do contact resistance (Do you have a DLRO?) and contact erosion inspection. A power factor test should also be done if it is new to establish baseline data.
My experience of vacuum bottle testing in accordance with manufacturers recomendations indicates the following test voltages:-
11kv bottles tested at 20kvrms
33kv bottles tested at 58kv rms
both for 5-seconds
dc testing is no longer recomended but these values were used before the change:-
11kv bottles tested at 30kv
33kv bottles tested at 70kv
High DC voltages (over about 30kV) between 2 electrodes a very short distance apart produce x-rays, unsure exactly why. I noticed in the dental office they use 60kVDC 7mAmps yesterday. GE recommends 10 feet from the bottles. DC can be used to verify that the bottles are good by withstanding the test voltage, but the manuals I have read do not allow DC to fail the bottles, only an AC test can fail the bottle.
If DC will generate X rays when the electrons impinge on one electrode (contact) then AC will probably generate X rays at both contacts.
The X ray tube in early commercial X ray machines was basically a vacuum tube diode with the plate anode mounted at a 45 degree angle to direct the X rays. It was fed with about 100kV AC and acted as a rectifier as well as an X ray generator.
Bill
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"Why not the best?"
Jimmy Carter
*9. Perform power-factor or dissipation-factor tests on each pole with the breaker open and each phase with the breaker closed.
*10. Perform power-factor or dissipation-factor tests on each bushing. Use hot collar procedures if bushings are not equipped with a power factor tap.