Calibration constant and associated uncertainty of high frequency current transformers for off-line or on-line partial discharge measurement in high voltage insulated cables

摘要

Partial discharge field measurements in insulated cables are widely performed by means ofhigh frequency current transformers (HFCT) as well for off-line test as for on-line test.Calibration of the measurement is a very important part in the procedure as described instandards and performed in practice. However, it is also known that PD apparent chargemeasurements are poorly comparable. That becomes very often an obstacle for utilities tointegrate PD measurements in asset management and standards. To a large extent, this lack ofcomparability is due to the fact that no uncertainty is associated to measurements. It can beshown that there is an uncertainty associated to the acquisition system characteristics that canbe evaluated. Furthermore, a unique calibration constant can be also defined for the sensor.This can be very useful especially for on-line PD measurements where calibration is difficultto perform.