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Low-voltage Cable Insulation Level Insulation - Follow-up

Low-voltage Cable Insulation Level Insulation - Follow-up

(OP)
Searching for reference about insulation coordination, I consult thread238-232606: Cable Insulation Level Selection from 2008 and though I should comment about what I find.

Background
First, I was questioning myself if a ACWU90 600V cable was suitable for a 600V application (Qu├ębec, Canada) considering that, by common practice, I specify 1000V cable for 600V application

Previous thread
So, I found on Anixter Wire Wisdom that there are Insulation levels for cables 2kV and over, but that there is not for under 2kV cause low-voltage cable insulation would be overated in the point of view of electrical stress. The reference tells that low-voltage cable insulation must sustained 5V per mil (0.001 inch) of thickness. ACWU90 insulation thickness range from 0.045 to 0.060 inch (45 to 60 mils) for 225 to 300 V of electrical stress. So it's suitable for 100% and 133%.

But the thread was about the 173% level!

Application where the 173% level at low-voltage would be required should go for a 1kV insulation. I didn't say "shall". Arguments base on statiscs about LG fault and insulation failure concerning reliability might stand in justifying the 600V rating for 480V application. Would also look upon health & safety matters, too. And the best is to conduct a transient study. However, time & budget might not be available for such thoroughness.

Conclusion specific to my case
Usually, It's not really a concern in my market cause it's the most available cable voltage for copper cables (TECK90 1kV). However, the ACWU90 appears to not be available with 1kV insulation.

About my case, I'm not concern about having a High-resistance grounded system cause I fall under the Mines regulation wich restrict fault duration under 1 sec. Althought it's not all infrastructure on site that fall under the mine electrical code, it's usually applied over the whole site to avoid confusion for maintenance personnel or local authorities.




Danny Garant, ing.jr
Groupe Stavibel Inc.
www.stavibel.qc.ca

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