The withstanding voltage test is basically performed with an AC voltage.
However, the AC voltage may cause a large current to flow into a capacitor (such as a filter) in a DUT.
Some safety standards permit the DC withstanding voltage test to be conducted in place of the AC withstanding test where appropriate.
Many of such standards specify that the DC test voltage should be equal to the AC peak-to-peak value of the AC test voltage.

Note: Some safety standards require that the DC withstanding voltage test be performed when testing a DUT having a DC circuit.