Research On Electromagnetic Interference Due To Disconnector Switching Operation In GIS

GIS isolation switch operation to produce arc re burning, the gap between the contact voltage suddenly drop to establish a step voltage. This voltage steep wave propagates in the GIS will generated very fast transient over voltage (VFTO), which is harmful to the internal equipment insulation; external communication to produce transient enclosure voltage (TEV) interference secondary equipment and even endanger the personal safety. With the power system voltage level more and more high and the electromagnetic environment become more complex, The transient process in GIS is more and more prominent to the equipment insulation and the secondary system disturbance coupling problems of power system.To solve the above problems, this paper takes Chenjiaqiao 500kV GIS as an example. Firstly, using the Bergeron method to equivalent each component model and selecting the appropriate parameters, Establishing EMTP simulation circuit model to calculate the VFTO; secondly, equivalent casing parts using an ideal transformer model and establishing the GIS external three transmission line system circuit model to calculate the TEV; Finally, in the case of capacitive voltage transformer (CVT) or current transformer (CT), discussed primary system transient over voltage or transient current for secondary equipment of conducted interference, observe the effect of inhibiting conduction interference.Through the calculation and analysis, it is showed that the VFTO amplitude in GIS is much more than the system voltage. Bus residual charge and the transformer entrance capacitance and isolating switch closing resistors on VFTO has a great influence; In addition to the internal VFTO, the TEV of the bus shell is mainly decided by the grounding condition of the shell. The smaller the grounding inductance, the smaller the amplitude of the TEV is. In general, using high conductivity grounding material and multi point grounding method to reduce TEV; The main measures to suppress the interference of the secondary system is to strengthen the protection effect of the two cable. The two cable multi wire grounding and installation of filter capacitor can restrain the influence of the conductive interference.