Partial discharge is the partial breakdown of the dielectric of a small part in a system of solid and liquid insulation under the influence of high voltage.

Partial discharges result from internal discharges due to the formation of holes in insulation, air bubbles, and voids between the dielectric and the semiconductor. A discharge that creates a path along a gap between two components, or a discharge from the growth of an electric or water tree. When the electric field strength inside the holes or cracks reaches a threshold value, the gaseous form is generated by ionizing the defect, the free electrons generated by the initial collisions continuously, will gradually lead to breakdown or discharge through holes, defects in insulation.

Early detection of partial discharges inside insulating materials of electrical equipment such as transformers, power cables, generators, medium voltage cabinets… before being put into use and operation for the purpose of ensuring safety and reliability in the power system.

For 24kV or 35kV medium voltage cabinets, the measurement and evaluation of partial discharges are carried out according to the guidelines of IEC 60270:2015 and IEC 62271-200:2021.