Precautions for insulation resistance test of polypropylene capacitor

For polypropylene capacitor, the purpose of insulation resistance measurement is to preliminarily judge the insulation condition between the two poles of coupling capacitor and the two poles of power capacitor to the shell. The following matters should be paid attention to during the measurement:

(1) Before and after the measurement, the two poles of the capacitor and between the two poles and the ground should be fully discharged, especially for the power capacitor, it should be directly discharged from the two leading out ends, rather than only on the connecting conductor board, because most of the power capacitor poles are connected with the connecting conductor plate, if the fuse of a power capacitor is fused, the discharge on the connection board is not necessarily The electric charge stored on the power capacitor can be discharged completely.

(2) The capacitor should be shaken according to the insulation resistance measurement method of large capacity test object. In the process of shake measurement, the handle of megger should not be stopped before disconnecting the insulated megger, so as to prevent damage to the megger by reverse charging.

(3) It is not allowed to measure the insulation resistance between the two poles of the power capacitor for a long time. Due to the large capacitance and storage charge of power capacitor, it is easy to cause personal and equipment accidents if the operation is not careful for a long time. Some units generally shake the megger slightly for a few turns, generally no more than 5 turns, and then judge the insulation condition by the discharge sound and spark of the two poles discharge of the capacitor. If there is clear discharge sound and obvious discharge spark, the insulation of the two poles of the capacitor is considered to be in good condition. If there is no discharge sound and spark, the insulation inside the capacitor may be aged due to moisture or the lead wire between the two poles and the capacitor is disconnected. When the two ends of the lead wire are connected to each other directly, the two ends of the lead wire should not be discharged by the naked person.