Impact of Superimposed Direct 50 Hz Alternating HV Stress on Surge Arresters

摘要

The trend towards to integrate renewable energy sources into the distribution and transmission grid is obvious and increases both on national and international side. There are numerous different kinds of grid interconnections and structures realised as HVDC-, HVAC- or as a hybrid grid structure which contains of both voltage waveforms. High voltage metal-oxide surge arresters (MO arresters) may represents the only technical and economical method to protect such multivariate hybrid grids and the containing electrical power devices by limitation of temporary, slow - and fast rising overvoltages. Thereby, the simultaneously demand of compact MO arresters and a reliable functionality at a continuous operation voltage waveform require MO varistors and/or MO arrester designs to handle the higher power load. This higher load is often caused by non-ideal sinusoidal or direct voltage waveforms with harmonic content. The extremely different continuously operating voltage waveform constitutes as a composite voltage and affect the MO arrester in terms of a higher operating temperature, unexpected and difficult phenomena or may lead to a failure of the non-linear MO resistor or of the complete arrester. Therefore, it is favourable to measure the voltage and current waveforms by different composite voltages (50 Hz U_(AC) + U_(DC)) in the laboratory and to analyse the measurement values to know the acceptable ratio of the voltage as well as current components. Further, the objective of this contribution was on how the leakage current and the voltage distribution change along the MO arrester by a defined composite voltage stress which takes into account the different components of the composite voltages.