New ways of disruptive discharge recognition in insulation testing devices

Transformers are cost-intensive components of the electrical power supply. In order to avoid disturbances and to guarantee the operational safety, complex monitoring systems are installed to high voltage power transformers increasingly, which deliver the most important operating parameters on-line. One of these important parameters is the electrical breakdown voltage of the used oil. A fast breakdown recognition and switching off after a breakdown does not only play a role in the assessment of the breakdown voltage on the basis of several measuring sequences in which the result of one sequence depends on the breakdown energy of the sequences before but is also of special importance for the monitoring system. Every breakdown produces decomposition gases like hydrogen (H/sub 2/) and simple molecular hydrocarbon connections. Dielectric test devices which maintain the short-circuit current during a breakdown for a unnecessarily long time lead to an increase concentration of the gases mentioned before. Therefore the test device needs a fast disruptive discharge recognition. The article describes a new way of disruptive discharge recognition for test devices with an optical sensor to minimise the energy which is transposed into a test sample during the breakdown.