Reactive power static sources in the diagnosis of insulation condition of the induction motor and the power supply cable in terms of local compensation

Reactive power compensation is particularly relevant for the industrial companies, major power consumers of which are asynchronous motors (АM). The most effective reactive power compensation is at placing the capacitor bank (CB) directly at the points of AM connection. The capacity of the CB and the method of controlling the power factor depend on the AM loading conditions. Under operating conditions ensuring AM reliable start-up after a technological pause is an important task. Reliable motor start-up is possible when the insulation resistance of the stator windings is equal to or above 0.5 megohms. The discharge of the capacitor bank at the moment of the AM disconnection from the network, makes it possible to use the power stored in the CB to diagnose insulation condition and suitability of the AM to a safe start. The speed of the CB discharge is the criterion showing that the AM winding insulation resistance is of critical value. The capacitors discharge simulation made it possible to develop a method to protect the AM and the power cable as well as to formulate an algorithm to identify one-, two-, three- and interphase short circuit when operating, and at the time of the AM disconnection from the network and to define the critical value of the insulation resistance according to the capacitor discharge speed