When testing the insulation of conductors on feeders and service, what must be the resistance value for the conductor to be considered acceptable?

For conductors on feeders and service, an acceptable insulation resistance value is considered to be higher than 1 Mega-ohm. This benchmark is established based on industry standards, which dictate that insulation resistance values provide a reliable indication of the integrity of the insulation material. A value above this threshold typically signifies that the insulation is in good condition and able to effectively prevent current leakage, thus safeguarding both equipment and personnel.

Having insulation resistance below 1 Mega-ohm could suggest deterioration or damage that may lead to increased risks such as electrical shorts, safety hazards, or failures in equipment operation. The choice of a value higher than 1 Mega-ohm aligns with many regulatory and safety standards that recommend ensuring sufficient insulation quality to maintain operational safety and efficiency.

Values that fall below this threshold generally indicate a need for further inspection or even replacement of the conductors. Conversely, while there are ranges above 1 Mega-ohm, such as 5 Mega-ohms or other values, the key criterion here is that it must exceed 1 Mega-ohm to be deemed acceptable. Thus, a higher insulation resistance indicates better insulation integrity and a lower likelihood of failure in actual operating conditions.