ASTM F3121 defines that the wet test shall not have a leakage current of more than 1µA per 1kV per foot at 60Hz AC. At a 75kV per foot wet test, the maximum leakage current allowed would be 75µA.  For the dry test, CHANCE suggests no more than 20µA during a dry test.

Links:

http://blog.hubbellpowersystems.com/are-you-properly-testing-your-hot-line-tools