practical interpretation of insulation readings

[SparkyTris]

in the field, at potentials < 1kV, with "any old megger"

I contend that:

Insulation readings of >= 1Megohm on the megger's 1kV setting, indicates "good to go".

insulation readings between 250k-1M: "keep yer back to it and lets see what happens when energised"

insulation readings below 250K indicate further investigation required.

thoughts?

 

[ericmark]

With a mineral insulated element, I would not worry too much with a low insulation resistance, as long as hard-wired, and no RCD to trip. But with an IT bit of equipment, I would want a high resistance and be testing with 250 volts.

There is no one fits all. What it is and where it is matters.

 

[SparkyTris]

small (so-called inspection class) ROV. testign for insulation on the umbilical connection to a manual umbilical reel via sliprings. 500V DC nominal down the line. protected from lethality by a patent LIM

 

[endecotp]

What is the spec of the cable? What was its insulation resistance when new?

Look for deterioration compared to spec or a previous measurement.