Diagnostic Accuracy and Technical Considerations for MV Cable Field Partial Discharge Measurements

Partial discharge (PD) field-testing has been used widely used to reveal ‘dry electrical’ type defects in extruded medium voltage (MV) cable systems, covering varying application contexts, system criticality levels and asset management objectives. In terms of PD measurement systems intended for field MV cable system diagnostics, a wide range of commercial technical offerings exist amongst equipment vendors and service providers, involving different types of voltage sources and different levels of system complexity. This happens in a context of lack of standardization, and often a lack of understanding of the different factors that can influence the accuracy of PD measurements. Such factors can result in the very ‘real’ probability that the use of one MV cable PD measurement strategy / system versus another could lead to diagnostic inaccuracy, and ultimately different MV cable field PD assessment outcomes for the same test situation. This paper thus summarizes and illustrates the importance of testing context, diagnostic accuracy, and key technical considerations upon which MV cable field PD measurements are critically dependent. The objective is to assist non-expert end-users engaged in the specification, procurement, or execution of a MV cable PD field condition assessment programs to understand their requirements, objectively evaluate available options, and ultimately select the most appropriate PD testing strategy for their specific context.