Partial discharge or “corona effect” usually occurs in small cavities, airspace, bubbles in epoxy resins, or other dielectrics. Partial discharge can take place randomly and unexpectedly, and regular discharge will ultimately lead to components failure, which in turn equates to complete equipment failure.
The key to preventing any possible problem is early detection, when connectors or penetrators are manufactured during the many processes prior to final testing. The design of the various dielectrics and components is also crucial to deliver a partial discharge product.
Partial discharge measurement can be done in a number of ways. However, when constructing high voltage connectors, experience shows that poor termination and jointing is a major cause of failure of cables to connectors. This is due to the fact that in contrast to the cable, the terminations have a more complex structure with several dielectrics and expanding field gradients. Partial discharge radiates electromagnetic pulses and can be detected acoustically usually within a bandwidth of 250 – 5000 Mhz-