Every milk carton at the grocery store has an expiration date. The idea is the milk is assumed to be good until that date. That’s not a bad idea, unless you apply the concept to something like medium-voltage cables.
Here’s how the bean counter “thinking” goes:
“The manufacturer says those cables are good for 20 to 30 years, so we can save considerable money by putting them in the insulation resistance testing program when they turn 20 years old.”
That’s logical as far as it goes, but it doesn’t go very far when you consider the manufacturers are giving that figure absent of the many factors that can cause premature cable failure.
If you buy a new car, it should last, what, 20 years? Try driving it with low fluid levels and see if you need to reassess. One high-voltage stress experience on that cable could be compared to driving your car for 1,000 miles with a low oil level.
You must test these types of cables to see what’s going on.
