System for Monitoring the Condition of Metal-Oxide Surge Arresters in Service

The paper presents a low-cost system for monitoring the condition of metal-oxide surge arresters (MOSAs) in service. The developed system integrates two methods currently used for evaluating the condition of surge arresters: registration of transient overvoltages experienced by a MOSA and analysis of leakage current. A surge counter with a built-in primary leakage current sensor (SCLCS) is mounted on a MOSA to register the date, time, and value of charges carried by the discharge currents through a MOSA. The SCLCS powered by a long-life battery stores the recorded data in non-volatile memory. A measurement module connected successively to each SCLCS reads the registered data and performs a leakage current analysis, which involves the determination of the resistive component and the 3rd, 5th, 7th harmonics of the total leakage current. The voltage reference signal received from the secondary side of the potential transformer is wirelessly transferred by a transmitting unit. Six-year experimental testing of the developed prototypes installed at several distribution substations produced satisfactory results. The conducted tests confirmed the efficiency of leakage current analysis not only for detecting deterioration in the MOSA condition but also for differentiating its cause. Data obtained by an SCLCS provides useful information on lightning and switching transient overvoltages arising in a particular network segment, the efficiency of the arrester operation, and the amount of energy absorbed by the MOSA. The paper describes the hardware implementation, operational principles, and main technical specifications of the proposed system. The results of the pilot testing of the system are presented.