Application of the Wave Channels Method to Analyze the Switching Overvoltages in Energizing a High-voltage Cable Line

Abstract

A study of cable line failures shows that a large number of faults occur in the connecting and terminal couplings of 110--500 kV power lines. Overvoltages caused by operational switching in the substation switchgear circuits contribute to the total number of failures. The switching overvoltage amplitude and frequency depend on the parameters of the source, switched circuits, and switching moment. The aim of the study is to identify the network and switched circuit parameters affecting the maximum overvoltage excited by energizing a 400 kV cable line and to determine the degree of their influence. The following factors are considered: switching phase, cable line length, source inductance, and line residual charge. The analysis was carried out by the wave channels method. To achieve this goal, an analysis model was developed in the EMTP-RV software environment, which made it possible to calculate the electromagnetic transients excited by cable line switching. The model has been verified with respect to the surge propagation velocity along a coaxial wave channel. Overvoltage calculations have shown that the switching phase and the line charge availability in the pre-switching operation mode have the most significant effect on the overvoltage value. The obtained study results apply to high-voltage electrical networks containing cable lines. The study results made it possible to quantify the degree to which the considered factors influence the overvoltages excited by switching 400 kV cable lines and to assess possible exceeding of the values permitted by the relevant standards, which will make it possible to have a preventive influence on the number of failures.