From the utility transformer secondary, 480Y/277, we pulled 600 kcmil conductors 350 ft, underground in PVC to our main distribution panel. We used the Ideal Megger set at 500V and checked each conductor. A, B, and Neutral readings were 999 Mohms - maxed the resolution of the megger. C read anywhere from 65-115 Mohms.
Tomorrow, I want to hit C phase again at 500V and 1000V. It's my understanding that I want to get simular readings at both voltages. If my 1000V reading is significantly lower than my 500V this would indicate a deteriorating situation and the replacement would be necessary.
However, I find a lot of varying information on what an acceptable reading should be. Some info I have read indicates 0-50 Mohms, replace. Some say anything under 100 Mohms replace. I have yet to check the job specs to see if there are any minimums listed, which I will do tomorrow.
Assuming I get the readings I am after with the step voltage testing and there is nothing in the specs to say otherwise, go or no go? Is my testing methodology sound and is there anything else I should or could do?
Thank you.
Tomorrow, I want to hit C phase again at 500V and 1000V. It's my understanding that I want to get simular readings at both voltages. If my 1000V reading is significantly lower than my 500V this would indicate a deteriorating situation and the replacement would be necessary.
However, I find a lot of varying information on what an acceptable reading should be. Some info I have read indicates 0-50 Mohms, replace. Some say anything under 100 Mohms replace. I have yet to check the job specs to see if there are any minimums listed, which I will do tomorrow.
Assuming I get the readings I am after with the step voltage testing and there is nothing in the specs to say otherwise, go or no go? Is my testing methodology sound and is there anything else I should or could do?
Thank you.