15kV Rated Primary Cable Used at 17.2kV

[saladhawks]

The utility I work for has used 15kV Rated Primary Cable w/ 133% insulation on our 17.2kV System for the last 25+ years. An "all knowing" consultant was recently hired and has said that this is not an acceptable practice.

It is my understanding that the 133% insulation adds the necessary mils to the insulation to bring it even with a "custom" cable that would be made for 17.2 kV. Am I missing something here?

 

[davidbeach]

I wouldn't go there. The intent of the additional insulation is for protection of the cable during slow clearing ground faults on another phase. Are you clearing all faults fast enough that you could be using 100% insulation, or do you really need a 133%, 17.2kV cable? This sounds to me like a case of penny wise and pound foolish; it probably works for newish cables, but as your cable plant ages, watch out, you probably won't get the expected life from those cables.