Testing medium-voltage (MV) cables with the high-potential (hi-pot) test is typically part of a MV cable testing program. In Part 4, we looked at the advantages and disadvantages of the DC version of this test. What about the AC version?
As the name implies, the AC hi-pot uses an alternating current (AC) source. It’s good for identifying high-impedance and conductive defects in cables. It’s generally a go/no-go test and is commonly used to simulate steady-state AC service conditions and/or repeat the factory over-potential test.
Unlike the DC version, it does not have the space charge drawback. Although it can accelerate cable aging, the rate increase is typically much less than what you get with the DC version.
On the downside, it costs more than the DC version. And it requires a much bigger power source, a factor that can be problematic if you have to lug the power supply up and down stairways. Conducting the test may (at times) require several test technicians, all of whom must (per OSHA and the NEC) be qualified, and that can complicate scheduling.
