RVM versus PDC Methods for Insulations’ Conductivity and Moisture Content Monitoring

Degradation due to ageing is a major concern for the life span of high voltage insulation. In maintaining the insulation system’s performance, it is crucial to monitor the insulation condition as it contributes to the whole system’s efficiency and safety. Many diagnostic methods have been introduced, and in use for monitoring the condition of insulation. Measurement and analysis in either frequency or time domain. Condition-based monitoring (CBM) is in growing interest lately, compared to time-based monitoring due to the increasing population of aged insulators being utilized in existing power systems. Time-based monitoring has then been integrated with CBM. CBM’s ability to enhance reliability, improve safety and reduce hazard of a system has been recognized by many researchers and utilities. This paper presents the study and comparison of two time domain CBM techniques namely the polarization and depolarization current (PDC) measurement and return voltage measurement (RVM). Findings of previous researches on determining the insulator’s moisture content and conductivity by both methods were reviewed. Moisture content and conductivity affect the dielectric response of the insulation material. Thus, condition of the insulation system can be determined based on these two characteristics.