Thyristor-switched arrester for improved protection of power system equipment

Metal oxide varistors (MOVs) are widely used in power systems for overvoltage protection. With the application of power electronics, it is possible to enhance their voltage limiting capability. Capacitor dynamic voltage suppression (CDVS) may be accomplished during switching to reduce inrush transient overvoltages or to remove trapped charges. This is achieved by dynamically changing the arrester characteristics. The CDVS approach involves integrating an MOV block with anti-parallel thyristor pairs. A single CDVS unit may be used to reduce inrush transient overvoltages when energizing. When de-energizing the trapped charge is suppressed by sequentially bypassing several units. EMTP-based simulations are carried out to substantiate the analytical results by modeling an installed capacitor bank at the CU Project, HVDC Dickinson Terminal near Minneapolis, Minnesota. Potential benefits include a relatively fast switching response for reactive power control and life extension of equipment by reducing reactive switching overvoltages.