dc dielectric test for 33kv cable 1

[pmgohpelangi]

Carried out dc dielectric test for a 33KV XLPE cable at 54kvdc recently. The cable has not been energized. However, the client wants to retest the cable. What should be the test voltage? Remain the same at 54kvdc or lower? Any suggestions or is there any standard to follow?

 

[crshears]

Google has numerous links to recommended hipot test voltages for AC cables.

Why does the customer want this test repeated?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[thermionic1]

Carried out dc dielectric test for a 33KV XLPE

You should really be using AC VLF for XLPE cable.

 

[dpc]

If this is new cable, I would follow the cable manufacturer's recommendations. DC hi-pot testing has fallen out of favor, especially for XLPE insulation.

 

[crshears]

DC hi-pot testing has fallen out of favor, especially for XLPE insulation.

Can you expand on that, dpc?

Thanks.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[dpc]

I'm not an expert, but certainly dc hi pot testing not advisable for installed cable over 5 years old - the test can be destructive. I believe this is the IEEE recommendation. VLF ac hi-pot is generally considered safer. New cable is not as big a concern. Again, I would closely follow the manufacturer's recommendations.

 

[Tony Tonon]

I think the OP said it was never energized.
You can check the Acceptance Tests listed on NETA (National Electrical Testing Association.)

 

[7anoter4]

According to IEC60502 /2005
20 Electrical tests after installation
20.2 Insulation test
20.2.1 AC testing
By agreement between the purchaser and the contractor, an a.c. voltage test at power frequency in accordance with item a) or b) below may be used:
a) test for 5 min with the phase-to-phase voltage of the system applied between the conductor and the metallic screen/sheath.
b) test for 24 h with the normal operating voltage of the system.
20.2.2 DC testing
As an alternative to the a.c. test, a d.c. test voltage equal to 4 Uo may be applied for 15 min. [Uo=phase-to-neutral or earth voltage]
NOTE 1 A d.c. test may endanger the insulation system under test. Other test methods are under consideration.
NOTE 2 For installations which have been in use, lower voltages and/or shorter durations may be used. Values should be negotiated, taking into account the age, environment, history of breakdowns and the purpose of carrying out the test.

 

[7anoter4]

IEEE Std 525-2007
IEEE Guide for the Design and Installation of Cable Systems in Substations
8. Power cable (1 kV to 35 kV)
8.11 Acceptance testing (see Annex M)
Shielded and unshielded medium-voltage cables should not be subjected to high-voltage dc tests; insulation resistance tests are recommended (IEEE Std 400™-2001).