Medium-voltage (MV) cables typically must be tested under tight constraints of time, budget, and other resources. These constraints and other factors mean you must choose which tests to perform.
The high-potential (“hi-pot”) test is typically included in an MV cable-testing program. But should you choose the DC or AC version? Let’s look at the DC version, first.
As the name implies, the DC hi-pot uses a DC source. This test would seem to be the one of choice, because it’s simple to perform and gives you a simple pass or fail. Relative to other choices, it’s low-cost because of low training/skill requirements and the required test equipment for it is relatively affordable.
However, when used on service-aged MV cables it can destroy the insulation. Repeated use of this method can accelerate the aging of the cables, for several reasons. Also, leakage current readings can be skewed by such things as moisture and wind.
The AC version of this test costs more, but has advantages (and disadvantages) that we’ll address in Part 5.
