Test stand for high voltage insulator partial discharge testing with ultra short X-ray pulses

Abstract

Top quality high voltage pre-test of solid insulating material requires long test intervals because the initiation of partial discharge (PD) in voids not only demands a sufficiently high electric field, but also the availability of a start electron. The latter leads to a statistical distribution of the time to PD inception, such that long test intervals are required to rule out the presence of voids. This makes 100% screening economically infeasible. However, if the PD is activated using ionizing radiation, the necessary test interval can be reduced to a minimum, without risking that small voids will be missed. It has already been shown that pulsed X-rays are able to trigger PD in voids and not affect the measured PD magnitude. Based on this method, known as Pulsed X-ray Induced Partial Discharge (PXIPD), a test stand for routine testing of insulators up to 420 kV has been developed and put into commercial operation. A very low measurement noise level permits an automatic analysis of the results. Already more than 20,000 insulators for installation in GIS have been screened using this PXIPD method on an industrial scale. Investigation of insulators with natural defects demonstrates the effectiveness and reliability of this new system. In combination with the short test cycle time and the ability to unambiguously link PD to a specific insulator the system allows for a leaner GIS production.