Study on current-sharing characteristic of multi-pillar parallel arresters for DC transfer switch

Abstract

Ultra high voltage direct current (UHVDC) system is the key support of power grid, which has an important impact on the development of China’s power grid. Direct current (DC) transfer switch is an indispensable component for UHVDC system, and its research is conducive to the development of the UHV DC transmission system. DC transfer switch is composed of breaking circuit, oscillation circuit and energy absorbing circuit. The energy absorbing circuit of DC transfer switch can absorb lots of energy by using arresters when DC is turn off, it can avoid the failure of DC breaking due to arc reburning. In order to meet the requirement of absorbing a large amount of energy, the arresters in the energy absorbing circuit generally adopts a multi pillars parallel structure. When multiple columns are connected in parallel, the uniform distribution of energy between different arresters columns becomes a very important problem. If the energy distribution difference is large, the arresters will overheat, aging and even explode. Thus, it is necessary to study the current-sharing characteristics. In this paper, the simulation and experiment are carried out in combination with the actual converter station. On the premise of total discharge energy in station, it is concluded that: The greater the deviation of volt–ampere characteristic curve from standard curve, the greater the non-uniformity coefficient and the greater the energy absorbed by single pillar arrester. The maximum energy absorbed by single arrester is 8.77 MJ, the non-standard curve by single pillar arrester should deviate from the standard curve by no more than 4%.