What is the minimum acceptable megohm value for a metal-oxide surge arrester rated 15kV with an MCOV rating of 12.7kV?

The minimum acceptable megohm value for a metal-oxide surge arrester rated at 15kV with an MCOV (Maximum Continuous Operating Voltage) rating of 12.7kV is determined based on industry standards for insulator performance and reliability.

For surge arresters, especially those rated for higher voltages, it's critical to ensure that they have an adequately high resistance value to prevent unnecessary leakage currents that could lead to overheating or failure. A megohm value of 5,000 Megohms is considered acceptable for equipment operating at this voltage level. This value helps ensure that the surge arrester will effectively block any unexpected surge while maintaining its integrity over time.

Lower megohm values would not provide sufficient insulation, potentially risking the operation of the arrester and connected systems. Therefore, the selection of 5,000 Megohms as the minimum acceptable limit ensures a reliable and safe operation of the surge arrester under its rated conditions.