Generator Insulation Testing by Continuous Time - Function Application of Direct Voltage

Large savings in generator insulation maintenance and replacement costs can be realized through the use of modem nondestructive insulation testing techniques. One such test involves subjecting the insulation system to a high direct voltage (HDV) with measurement of the resulting current as a function of time and voltage. A new concept of HDV testing and the associated test equipment, which will produce more reliable and useful data on the condition of the insulation system is presented. The new system is designed around a high-stability HDV supply which applies the test voltage at a predetermined continuous rate of rise which permits accurate measurement of small increments of specimen current. Emphasis is placed on the proper use of guard circuits and on the high stability of the power supply to eliminate misleading results and permit detection of fault paths nondestructively.