Partial discharge testing is one of the most important techniques applied in the protection of electrical assets. It is mainly concerned with the monitoring and the measurement of the quality of the insulation materials that have been used in the cable power systems.
If the power cable insulation mechanism has broken down or is in the process of breaking down, it will produce partial electrical discharges which can be detected, monitored and analyzed using specialized partial discharge testing equipment. The partial discharge testing or PD testing is generally mostly applied in the extruded insulation materials on the cables.
Partial discharge testing can be carried out in two main modes. One form of the testing and the monitoring includes measuring all the discharges that are occurring in the cable system. On the other hand, the testing geared at monitoring a particular spot on a power cable. This will be applicable in cases where you need to locate an individual discharge point in the cable system as opposed to measuring all the discharges in the cable system.
Measurement of the PD
This is one of the most significant tests generally carried out on the power cables before they are released into the marketplace. It is done in order to ensure that they are highly reliable. The tests are carried out at power frequency in order to predict the cable’s behavior when it is deployed in the real world high voltage high-frequency applications.
When testing is done at the factory, the manufacturers generally apply a voltage frequency that is slightly higher than the actual voltage frequency that will be used in the ground in order to guarantee the reliability of the power cable insulations. Low frequency partial discharge testing is also carried out in order to detect the imperfections in the power cables.
But factory tests are not sufficient and may not detect 100% of the imperfections in the cable insulations. Besides, as the cable is used in the real-world environment, it will undergo a slow degradation and create new imperfections that will lead to partial discharges and which may grow into something more serious if it goes unchecked.