Insulation resistance

A numerical value that indicates the insulation properties of electrical and electronic equipment. To prevent malfunctions or electric shocks caused by leakage current, the insulation resistance must meet or exceed a specified value. It is determined by measuring the minute current that flows when a DC voltage of 500V or 1000V is applied between specified measurement points within the equipment and the ground, or between two designated points within the equipment, using an insulation resistance tester. According to the technical standards for electrical installations, the value should be at least 0.1 MΩ for systems of 300V or less (150V or less to ground). During wet conditions such as rainy weather, this value tends to decrease. A lower value indicates a higher likelihood of leakage current.