Multi-spark modeling of very fast transient overvoltages for the purposes of developing HV and UHV gas-insulated switchgear and of conducting insulation co-ordination studies

Abstract

Abstract. Very fast transient overvoltages (VFTO) originate from steep voltage breakdowns in SF 6 gas that are inherent to operation of any switching device of the gas-insulated switchgear (GIS) type. For power stations with voltage ratings exceeding 500 kV, the ratio between equipment rated-and withstand-voltage levels becomes relatively low, which causes the VFTO peak values to reach the component's insulation withstand-voltage levels, thus becoming a design factor for high-and ultra-high voltage GIS. While well-established approach to VFTO analyses involves only single VFTO events (the so-called single-spark approach), there is often the need to analyze the entire VFTO generation process, for which the multi-spark approach to VFTO modeling is to be employed. The multi-spark approach allows one to evaluate the VFTO impact on the GIS disconnector design along with the impact of the VFTO on selection and dimensioning of the VFTO damping solutions. As the multi-spark approach to VFTO modeling is now being increasingly used in UHV GIS developments as well as for the insulation co-ordination studies of power stations, the present paper is motivated by the need to report on the VFTO multi-spark modeling approach and to lay a common ground for development works that are supported extensively with VFTO simulations. The paper presents physical assumptions and modeling concepts that are in use in such modeling works. Development of the multi-spark GIS disconnector model for VFTO simulations is presented, followed by an overview of examples of the model application for the GIS development works and for insulation co-ordination studies.Key words: very fast transient overvoltages (VFTO), gas-insulated switchgear (GIS), disconnector switch (DS), modeling, simulations, transients, switching, mitigation, breakdown voltage (BDV) characteristics. Multi-spark modeling of very fast transient overvoltages for the purposes of developing HV and UHV gas-insulated switchgearand of conducting insulation co-ordination studies To explore the VFTO associated with the operation of the UHV GIS disconnectors, the State Grid Corporation of China (SGCC) has recently established two full-scale test set-ups at the 1100 kV station in Wuhan (China), and conducted measuring campaigns with the total number of disconnector operations of approximately 2000 [8]. Several papers have been published based on this work, addressing different aspects of VFTO measurements and simulations. As an example, in [9] the impact of the disconnectors moving contact speed on the variety of VFTO parameters is analyzed.Also in the previous works conducted by ABB, the VFTO have been investigated to support design work of the 1100 kV disconnector [10,11] and to analyze the impact of the VFTO on selection of the VFTO damping solutions [6]. These works utilized the so-called multi-spark approach [4,12] for modeling the entire process of disconnector operation and to analyze distributions of the VFTO, along with other parameters, such as trapped charge voltage distributions, ...

A low‐cost and high‐performance self‐trigger method for high‐voltage transient measurement

“…The rise times of 4-7 ns and peak levels of 2.4 p.u. of VFTOs may deteriorate the insulation performance of GIS and its connected equipment [16][17][18][19][20]. VFTOs are widebanded, characterised by quasi-DC frequency components, power frequency, and high frequencies of up to over 100 MHz [2,13,[21][22][23].…”

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…Possible applications include biomedical treatments [16] and purification. Some industrial applications include pollution control, testing surge protection devices [17], and the ignition systems in plasma cutting and welding machines, or in electromagnetic pulse (EMP) generation [18,19].…”