POLARIZATION EXPONENT MEASUREMENT FOR INSULATION OF ELECTRICAL EQUIPMENT

摘要

PURPOSE:To enable accurate determination of insulation characteristic automatically by halting measurement when it is detected that the logarithmic increment rate of the insulation resistance becomes constant to estimate the value for 10min and a polarization exponent. CONSTITUTION:When a constant DC voltage is applied to a sample electrical equipment 1 by the operation of a keyboard 19, a leaked current detected with a detector section 4 is converted into a digital signal and started by the detection signal 1min after the application of the voltage, a signal is inputted into an insulation deficiency judging means 21 every minute. The signal is converted into an insulation resistance value Ri with the means 21 based on a specified formula and the results of comparison thereof with the threshold Rs are outputted to display sections 17 and 18 and thereafter, the stoppage of the measurement is transmitted to a control section 16. When RiRs, based on the value Ri and a measuring time signal Ti thereof, a logarithm increment checking means 22 sends a mean signal of the logarithmic increment rate to a polarization exponent estimating means 23 to determine the value for 10min while the value for 1min from the means 21 is used jointly to determine the polarization exponent and the results are sent to a decision means 24, which sends the results of judgment on the propriety of the polarization exponent thus obtained to be sent to display sections 17 and 18.