insulation resistance

A numerical value indicating the insulation performance of electrical and electronic equipment. To prevent failures and electric shocks caused by leakage current, the insulation resistance must meet a specified minimum value. It is determined by using an insulation resistance tester to measure the small current that flows when a DC voltage of 500V or 1000V is applied between designated measurement points within the equipment and the ground, or between two specified points within the equipment. According to the technical standards for electrical installations, the required minimum is 0.1MΩ when the voltage is 300V or less (ground voltage of 150V or less). This value tends to decrease in humid conditions such as rainy weather. A lower value increases the risk of leakage current.