Abstract :
To ensure the reliability of an accessory it is subjected to a type test. These type tests, either conform national or international standards, comprise a multitude of electrical tests. An important part of this type tests is the heating cycle voltage test in which the thermomechanical behaviour of an electrically stressed accessory is tested. Based on the IEC 60502–4 this heating cycle voltage test takes 20 days after which some final tests have to be undertaken to conclude the electrical type test. Before starting these 20 days also some tests (voltage withstand and partial discharge) are performed as a rough check: is it sensible to start the 20 days test or not. However, during this heating cycle voltage test no additional measurements are to be performed, leaving us “blind”. Normally speaking the thermomechanical and electrical stresses should not influence the behaviour of the accessory, but in case it does it will only appear at the end of the 20 days test (or earlier in case of a breakdown). This is not an imaginary situation because experience has shown that, depending on the type of accessory, on average 20. 50 % of all type tested accessories do not comply with the requirements [1]. In that case, possible crucial information remains undetected during these 20 days. To avoid this and give the manufacturer insight in the behaviour of the accessory, an on-line partial discharge (PD) detection and location system has been developed.
