Condition Monitoring based on Partial Discharge Diagnostics using UHF Sensors: A Comprehensive State-of-the-Art Review

Power System components are susceptible to insulation failures due to electrical and mechanical stresses, extreme environmental and operating conditions, material aging, chemical degradation and poor maintenance practices. Partial Discharge monitoring is one of the most significant metrics for health assessment of high-voltage power equipment. There are both conventional and non-conventional techniques for detection and measurement of partial discharges, and lately of the latter, the UHF method has been the focal point in non-conventional techniques. In this paper, the advantages of the UHF method are highlighted and a comprehensive review of the various UHF sensors that have been proposed in the literature is presented. The review aims at not only categorizing and describing the sensors, but more importantly examining their suitability for use in industrial applications as PD sensors for diagnosis purposes. Moreover, a thorough comparative analysis of the performance of different UHF sensors is provided using physical size, bandwidth, radiation pattern, design and optimization parameters, PD test setup and the intended application. The relative merits and limitations of each type of sensor are highlighted and a gap analysis is made. The critical area of UHF calibration has also been discussed in order to emphasis the requirement of comparable, repeatable and credible UHF measurements. Finally, considerations regarding future trends and possible topics for exploration are summarised. The review offers a valuable tool for researchers willing to acquire an overview of the state-of-the art on partial discharge monitoring using the UHF method.