DC rating of AC wire
DC rating of AC wire
(OP)
If we have a wire rated for AC 600V(RMS), can this wire be used for DC application with the DC voltage not exceeding the peak value of AC voltage (846V)? Is there any reference (beyond common sense) to allow to do such re-rating and to prove that this usage is correct and acceptable?






RE: DC rating of AC wire
I would think anything over the RMS rated value would cause problems.
RE: DC rating of AC wire
RE: DC rating of AC wire
=====================================
(2B)+(2B)' ?
RE: DC rating of AC wire
=====================================
(2B)+(2B)' ?
RE: DC rating of AC wire
RE: DC rating of AC wire
that when the ac field is applied. So, the dielectric strength will depend on voltage time rise. The insulation needs time to
withstand the field stress. The voltage time rise depends on resistance, inductance and capacitance.
Usually cable of 0.6/1 kV 50 Hz complying with IEC 60502-1 can be used for 0.9/1.5 kV dc. See:
h
RE: DC rating of AC wire
I didn't see much to support that in the attachment. I saw max dc rating for the cable was just slightly more than sqrt(2) times the ac rms value which seems to roughly equate the stresses to the instantaneous volage.
I do find this excerpt from IEEE 400-2001 (the most recent rev of that standard!?!... even though a lot has changed since then) which tends to suggest that cables have equivalent breakdown stress to ac as to dc when they are uniform, but the relationships change where there are defects, moisture, terminations, etc.
When they talk about testing wet cables at currently recommended levels resulting in failures, I assume they are talking about hi-pot. I don't have access to IEEE P400.1.
=====================================
(2B)+(2B)' ?
RE: DC rating of AC wire
Further more it is no connection between break-down test and hi-pot test since the first is executed on insulation specimen
and the second test on finished cable.
I agree with electricpete and with jghrist and I don't recommend any hi-pot test on cable already in operation- nor dc neither ac.
Hi-pot test has to be done on new installed cable according to standard requirements. They are authors sustaining the dc test is less destructive due to less corona or partial discharging phenomena.