Practical Test of VAR Control Relay

The control relays are used to control equipment in the power system or industrial centers. According to the requirements, specifications and operating conditions of the power system equipment these relays should provide a suitable performance. If these relays malfunction, some specifications of the power system may be out of standard range such as increase or decrease of voltage, frequency and other electrical specifications. To prevent such problems, the relays must be tested before commissioning and also in the periodical maintenance. In this paper, the performance of a var control relay (VCR) has been investigated. VCR controls the reactive power and if it be exceeded from allowed range, adjust the reactive power by connecting or disconnecting capacitor banks and consequently regulates the voltage. In this paper, first some important features of the VCR are explained and then some of these features have been tested, such as thresholds, the priority of signals, bank selection according to the switching counter and the performance of the relay against receiving protective signals. The results show that the relay operates correctly in different conditions.