Most cable manufacturers reccomend against hi-pot DC testing of XLPE cables, and suggest an AC test instead (effectively a no-load energization test). I would reccomend an insulation resistance test prior to energization though, just to pick up possible "gross" faults.
DC hipot testing of XLPE cable is considered possibly detrimental if the cable is has been in service in a moist environment for more than a year or two.
DC field test for medium-voltage cables: why can no one agree?
Mercier, C.D.; Ticker, S.; Industry Applications, IEEE Transactions on, Vol.34, Iss.6, Nov/Dec 1998
Recommendations in HV DC testing of MV cable insulation
Finke, B.H.; Industry Applications Magazine, IEEE, Vol.3, Iss.5, Sep/Oct 1997
Either AC or DC Hipot testing, which are destructive tests when the test voltage is above the rating of the cable, is recommended usually for Acceptance Testing(new cable) only. These type of tests will prove that the cable has no insulation and splice/stress cone problems.
Maintenance Testing on cable in service is a different story.
For years, hipot(DC or AC) was recommended at a test voltage and time significantly less than the Acceptance Test voltage(but still above the cable rating), but frequent sudden cable failure during the test(to a cable, I might add, that usually had no spare and no plan for immediate replacement), leaving the plant down with sdome very unhappy customers, has led quite a few people to recommend other, non-destructive tests, such as Polarization Index, lower-voltage Hipot, Doble Power Factor, Partial Discharge, etc.
It is important to note that AC or DC voltage doesn't matter as much as the test voltage level. AC test voltage recommendations are usually less than DC values for the same cable rating, since rms AC has peak voltages about equal to the DC test voltage levels.
Also, DC tests can be conducted with a small test set, while AC tests for a long cable sometimes may require a test set that must be transported by something close to your typical 18-wheeler.
Very low frequency AC is an alternative that is considered by some to eliminate the long-term detrminetal effects of a DC hi-pot test while using a reasonable sized test test.
Guide for Field Testing and Evaluation of the Insulation of Shielded Power Cable Systems IEEE Std 400-2001 is one overview—discusses merits of DC, power-frequency and VLF overpotential testing of cables.
Paul Gill’s Electrical Power Equipment Maintenance and Testing is another source.
