Gräf, Thomas , Hochschule für Technik und Wirtschaft Berlin , Germany
The average age of the electrical equipment of the energy distribution in the industrialized countries is actually more than 40 years. The question about upcoming effects and defects arise together with the questions about the remaining performance of this aged equipment. As well as questions of what kind of effects can be detected due to the age of the equipment. Additional ageing will be expected based on increasing energy fluctuation and based on the energy transition linked with harmonic frequencies caused by inverter usage. Over the last 4 years different switchgears of low- and medium voltage with ages up to 50 years with the long lasting influence of the environment and under operational conditions were investigated. Serval tests were performed at the test lab IPH in Berlin. The investigations considered making and breaking current investigations of the aged circuit breakers and the whole switchgear, measurement of the impulse and alternating withstand voltages, thermal testing, partial discharge detection and short time impulse current. The test results show that every investigated equipment was not able to reach the former nominal values. While the equipment was under operation, the multi physical effects lead obviously to different kind of ageing effects. Based on the achieved results, additionally impulses need to be given to the actual standardization to close the gaps within the standards and to give advices to the operators of the equipment, especially for maintenance and service. A lot of results were based on faults caused by the design and miscellaneous maintenance.