Testing voltage for cales 1

[raync]

Can any body tell me what is the D.C testing voltage (megger) for a 1kv xlpe 3core cable, and what codes apply for that?

Thank you

 

[Zogzog]

Read this thread

http://www.eng-tips.com/viewthread.cfm?qid=248906

 

[raync]

Thanks, but IEEE 576 Acceptance Testing io only for 5kv cable and up, and my cable rating is only 1kv, so any other code for Megger voltage testing ?

 

[Zogzog]

NETA says minimum of 1000V

 

[boshnaq84]

if you are testing insulation resistance then I'm pretty sure 1kv DC is enough

ofc then the resistance should read in the M.ohms, not sure about the codes also.

 

[7anoter4]

According to IEEE Std 525-1992:
"IEEE Guide for the Design and Installation of Cable Systems in Substations" ch. 11 Acceptance testing of installed cables
is stated:
a) Low-voltage power, control, and instrumentation cables may be insulation-resistance tested prior to
connecting cables to equipment. These cables may be tested as part of the system checkout.
b) The low-voltage power cable insulation resistance tests should measure the insulation resistance between any
possible combination of conductors in the same cable and between each conductor and station ground, with
all other conductors grounded in the same cable.
c) The test voltage should be a minimum of 500 V dc. The minimum acceptable insulation resistance is:
R in m.ohm = (rated voltage in kV + 1) ´ 1000/length in feet (304.8/length in meters)

 

[Zogzog]

That is a very outdated standard, they removed that kv+1 thumbrule years ago.

 

[7anoter4]

You are right, Zogzog. The "megger test" it is not an accurate test for a cable but only an indication of insulation state
and the resistance measured is compared with a "rule of a thumb" formula as in the above standard.
The new IEEE 525/2007 revised this, I think.
The Red Book- IEEE-std 141 indicates for low voltage cable a 1000-2500 V d.c. megger test as an indication of insulation state and should be compared with an older test one in order to check the insulation degradation, if any.
See ch.12.11.9 Megohmmeter test.
Low voltage cable of 1 kV rated it seems to me meets IEC 60502-1/2004 requirements. Here in
ch.19 "Electrical tests after installation" it is mentioned:
"Tests after installation are made, if required, when the installation of the cable and its accessories has been completed. A d.c. voltage equal to 4 U0 shall be applied for 15 min.
NOTE: Electrical tests on repaired installations are subject to installation requirements. The above test is for new installations only"
Uo=600 V 4*Uo=2400 V .