Translated Abstract
With the increasing capacity of high-voltage transmission systems, short-circuit current in the grid keeps rising. The high-voltage SF6 circuit breaker (HVCB), which is the key equipment to protect and control the systems, is also facing more and more severe challenge. Breaking performance, the crucial index of high-voltage circuit breaker, is a hot issue for researchers who concentrate on high-voltage electrical apparatus. However, it takes a lot of time and money to carry out correspending experimental research. Therefore, it seems to be a good choice to carry out the optimal design of HVCB with Magneto-hydro-dynamics (MHD) arc simulation method, taking the breakdown characteristic as the evaluation index. This is not only benificial to save the cost of the development of switchgear, but also significant for the safety and stablization of the systems.
Since arc simulation model for HVCB is not systematic and intergral, and there is a lack of intensive study on post-arc thermal and dielectrical breakdown characteristics, it is hard to evaluate the interruption characteritics quantitatively and accurately. In this thesis, 2D MHD arc model is expounded. Post-arc thermal breakdown model and post-arc dielectrical breakdown model is established. Whether the post-arc breakdown occuring or not is closely related to the pre-zero arc burning phase. therefore the simulation methods for the post-arc breakdown properties are put forward by combination of the MHD arc model and the post-arc breakdown model are validated by a series of T100s tests.
Due to the tremendous initial rise rate of transient recovery voltage (RRRV) of Short-line fault (SLF), it is extremely prone to thermal breakdown and is a type of fault that is difficult to break. With the aid of computer simulation analysis, this paper explores the shortcomings of a 252kV/63kA HVCB short-line fault breaking capacity, and studies the hot airflow field, arc voltage, and post-arc breakdown characteristics of the circuit breaker. Combining with simulation analysis, optimization designs are proposed, such as lengthening the throat, increasing the opening speed, increasing the internal diameter of puffer chamber. The calculation results show that all the schemes have an improvement effect on the thermal shutdown, especially when the puffer chamber internal diameter is 1.3 times, the RRRV increases from 1.144kV/μs to 10.067kV/μs, which can meet the short-line fault breaking requirements.
Domestic 50Hz HVCBs are encountering problems of 60Hz short-circuit current interruption. To deal with the issue, the simulation methods are applied to the difficulty analysis of 60Hz short-circuit current interruption in a 252kV puffer-type CB. Arc development, pre-zero temperature distribution in the gap, post-arc thermal and dielectrical breakdownis characteristics under the operating frequencies of 50Hz and 60Hz are analyzed. It is found that the relatively high pre-zero current slop is unfavorable for energy dissipation and results in insufficient temperature recovery at current zero for 60Hz short-circuit current interruption. Based on the calculation results, modification schemes of the arc-quenching chamber are discussed, where the evaluation results show that the critical RRRV of CB is elevated from 1.31kV/μs to 2.30kV/μs under tha same conditions.
Simulation method for the post-arc breakdown properties of high-voltage SF6 circuit breaker based on MHD modeling has been applied to typical working conditions of HVCB. It also provides theoretical methods for the optimization design and the interruption capabilities improvement of switches.
Translated Keyword
[high-voltage SF6 circuit breaker, Magneto-hydro-dynamics, operating frequencies, post-arc breakdown properties, Short-line fault]
Corresponding authors email
