On-Line and Off-Line Partial Discharge Scouting on MV Networks

The evaluation of the safe and healthy operation of the electrical assets goes through the knowledge of the overall status of their conditions. In particular, the assessment of the insulation system is important, being it the root cause of most failures. Among the various measurements that can be carried out on an electrical asset, the Partial Discharge Analysis (PDA) is one of the most efficient through which the effective deterioration of the insulation systems can be assessed. Nowadays the PDA is becoming an increasingly popular practice even in the MV sector, where its spread has been encouraged not - as for in the HV - by the high cost of a single component (e.g. power transformer, high voltage cable, etc.) but by a huge number of assets and their overall aging. The asset managers through the information given by the PDA can properly operate the electrical assets and perform maintenance based on their status (Condition-Based Maintenance - CBM) instead of using an approach based on maintenance actions performed at a fixed interval of times (Time-Based Maintenance-TBM). In this paper firstly the PDA will be proposed as the basis for the CBM and then a case study about a successfully partial discharge measurement campaign on a 33kV network of an island will be presented. The data is going to be discussed are relevant to both on-line and off-line tests in which a surface/interface PD phenomenon has been detected and subsequently localized through the Time-Domain Reflectometry (TDR).