Re.: Question of mega ohms/ kilovolt when testing insulation. A standard or passing result is actually what is needed or required to make the product or equipment safe and reliable. I tend to think 20 meg ohm /kv is good, but that is only relative to the level that is needed. Most likely 2-5 meg would be minimum and nearly anything would be safe with 100-150 meg.
As an example; in a lightning strike that put 20,000 volt surge into a line, you would be very safe with 2.5 Billion ohms which is 125meg ohm/kv. Hope this helps, macgyver.