Xiang Zutao

Influence of the Switching Speed of the Disconnector on Very Fast Transient Overvoltage

During the switching of disconnectors in gas-insulated switchgear (GIS), repeated strikes occur in the contact gap and lead to very fast transient overvoltage (VFTO). Severe VFTO may bring damage to transformers and other equipment. The switching speed of the disconnector is one of the important factors which influences VFTO. There are still different opinions on this factor. Very little quantitative study was done before this paper. In this paper, the whole repeated strike process associated with the switching operation of the disconnector was simulated and analyzed. The polarity and the probability characteristics of breakdown voltage were analyzed. The impacts of the switching speed of the disconnector on VFTO were studied by statistical methods. Comparisons were made between simulated and measured results. The simulation result shows that within a certain range of speed, disconnectors with a lower switching speed generate lower trapped charge voltage after opening operation and lower VFTO magnitude during the opening and closing operations.

Study on the SSO damping characteristic and damping control of Mongolia-China HVDC transmission system

The interaction exists between the China-Mongolia High Voltage Direct Current (HVDC) converters and turbine-generators at the coal-electricity base, and negative electrical damping provided by HVDC may cause subsynchronous oscillation(SSO). This paper studies on the SSO damping controller (SSDC) principle, SSDC input signal select, SSDC broadband design and narrowband design approach, etc. The SSO characteristics and damping control ability of the various turbine-generators and power output, etc. are researched.

Study on transients and effect on capacitor voltage transformer caused by disconnector switching of UHV Series Capacitor Banks

During the system commissioning test of Ultra High Voltage (UHV) project with Series Capacitors Banks (SCB), the adjacent capacitor voltage transformer (CVT) was damaged during the switching operation of disconnectors of SCB. In this paper, the transients on adjacent CVT caused by disconnector switching of UHV SCB were studied by simulation. The causes of damage of CVT were analyzed. The effectiveness of suppressing the transients by use of damping resistor of disconnector, series reactor and series resistor were studied by simulation. In UHV AC test base, a test circuit was established. It includes true type UHV SCB platform, UHV CVT and disconnector. Tests were carried out when the circuit was with or without limitation measures. Test results were compared with the simulation results. The simulation and Test results were in agreement.

Analysis and Corresponding Measures on Subsynchronous Resonance of Series Compensated Transmission for Large-scale Coal-fired Power Base in China

This paper investigates the risk assessment of subsynchronous resonance for series compensated UHV transmission of Ximeng coal-fired power base, which exemplifies a common problem in the development of the power grid in China. To avoid the problem of huge computational amount of offline analysis on subsynchronous resonance, a new method of online analysis and forewarning based on time-domain simulation is proposed. In addition, various suppression measures are summarized and discussed, as well as combination of multiple measures.

Study on system operation voltage characteristics of UHV transmission lines with series capacitors

Adopting series capacitors (SC) on 1000kV UHV AC transmission line can further uprate its transmission capacity, and it can also make impact on operation voltage characteristics of UHV system. Especially for heavy-load mode, as the large voltage step-up caused by SC, the issues on system operation voltage control may be more prominent. The layout manner for SC on lines and the relative fixed position between high voltage shunt reactors (SR) and SC can make great difference. Based on the planned Huainan-Wannan-Zhebei-Huxi 1000kV UHV AC double circuits transmission project, this paper researched the steady-state voltage distribution characteristics of Huainan-Wannan lines which are fixed with 40% series capacitors. Two kinds of simulation tools such as PSD-BPA and EMTPE are adopted in this study. The suggestions on the layout manner for SC and the relative layout manner between SR and SC are put forward, which can supply technique basis for the project implementation.