What is the AC Hi-Pot Testing?

Cables and cable accessories can also be field tested with 60 Hz AC voltage, even though this is typically not done because of the requirement for heavy and costly test equipment that may not be available or transportable to a field site. The typical field tests done on cables are DC hi-pot or VLF tests, such as one-tenth of hertz
frequency tests in lieu of AC hi-pot tests. Nevertheless, if AC hi-pot acceptance and maintenance tests are to be done on power cables, then it needs to be kept in mind that this test is not very practical in the field. Also, the AC hi-pot test can only be completed as a go-no-go test. Hence, it may create extensive damage in the case the cable under test fails. On the other hand, the AC hi-pot test has a distinct benefit over other tests that stress the insulation comparably to the normal operating voltage. Also, this test replicates the factory test completed on the new power cable. When completing the AC 60 Hz hi-pot test attention needs to be given to the adequacy of the test equipment for successfully charging the test specimen. The AC test equipment needs to have proper volt-ampere (VA) capacity to provide the needed cable charging current requirements of the tested cable. The VA capacity of the AC hi-pot test equipment can be calculated with the following formula:

𝑉𝐴 = 2𝜋𝑓𝑐𝐸^2 or 𝑘𝑉𝐴 = 2𝜋𝑓𝑐𝐸^2 × 10^−3

where

c is capacitance (μf/mile)
f is the frequency (Hz)
E is the test voltage (kV) of the test set
The test voltage values suggested for acceptance and maintenance tests are 80%
and 60%, respectively, of the final factory test voltage.