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Different from typical circuit breakers, breakers used to switch AC filters in convertor stations have to operate frequently according to the real-time operation mode and daily load changes. Therefore, the performance of filter breakers decreases very quickly, which leads to frequent accidents. Both preinsertion resistors and controlled switching devices can suppress switching transients. In this paper, a comparative analysis of whether a controlled switching device and preinsertion resistor should be adopted is carried out using PSCAD. The transient is calculated as the combined result of the switching angle and preinsertion resistor value, and the optimal configurations are proposed. After determining the resistor value and whether a controlled switching device should be included, the reference voltage of the arrester should be reevaluated. [ABSTRACT FROM AUTHOR]

On transmission lines where switching surges are not mitigated with closing resistors and/or surge arresters, high-speed reclosing on a line with trapped charge will produce high overvoltages that have been measured above 3 p.u. Careful simulations of these switching events using available electromagnetic transient (EMT) programs consistently produce significantly higher voltages than the measurements. This indicates a phenomenon present on the line that acts to reduce the switching surge magnitudes but is not typically modeled. This paper aims to identify the required simulation practices in reproducing the field measured overvoltages in EMT simulations and investigates the sensitivity of results to modeling approaches and electrical parameters. Field measurements from a switching surge test of a 230-kV line without surge mitigation have been used for model comparisons. Variations in frequency-dependent line modeling, ground resistivity, skin effect, shunt conductance, parallel lines, and source-side detail have been tested in an unsuccessful attempt to decrease the difference between the field measurements and the higher simulation overvoltages. It is demonstrated that even though the pattern of the transient voltage waveforms can be reproduced very well using frequency-dependent line models, the magnitude of the maximum overvoltage is significantly overestimated unless the effect of corona is considered. Two types of corona models are tested, and both demonstrate that corona is the primary factor that allows the simulations to correctly reproduce high peak overvoltage measurements. [ABSTRACT FROM AUTHOR]

Zero-missing is a phenomenon in shunt-compensated cable systems, in which the current through the line breaker does not cross the zero point for several cycles. This paper deals with a thorough investigation on countermeasures of the zero-missing phenomenon in transmission systems and determines the requirements, benefits, and risks of applying each method. The effectiveness of countermeasures is studied on a simulated cable project with different cable lengths in an actual grid model of the Dutch 380 kV transmission system. Results are analyzed based on three criteria related to the IEC standards and the Dutch grid code. In addition, the switching sequence of circuit breakers is specified to maximize the effectiveness of the countermeasures. A statistical switching analysis is performed for the insulation coordination study since the application of some countermeasures increases the probability of high transient switching overvoltages. Moreover, the closing variation threshold of circuit breakers is calculated as a function of the circuit impedance and the shunt compensation degree. [ABSTRACT FROM PUBLISHER]

This paper presents the work carried out by the IEEE Working Grou[ on field-measured overvoltages and their analysis for validating power system component models to be used in switching transients studies. The work uses measurement data obtained from field tests performed by Bonneville Power Administration in June 1995 where switching overvoltages were measured on one of its 230 kV lines. This paper includes a description of the switching tests and the main results derived from field measurements. Details of the switching procedures that were followed to calibrate component models used to match field-recorded waveforms can be found in the Part II paper. [ABSTRACT FROM AUTHOR]

Shunt power capacitors are essential to system operation and reliability as a critical reactive power source to increase system capacity, support voltage magnitude, improve power quality, and reduce reactive current flow. To mitigate capbank switching transients, the synchronous switching with preinsertion resistor technology is developed and used at an extra-high voltage transmission system. In this paper, the coupling relationship between several key factors that contribute to switching transients is studied. Optimization solutions are developed to improve the switching process. Field operations with an updated setting are compared with original setting records to prove the correctness of the study. [ABSTRACT FROM PUBLISHER]

In this paper, the commutation and switching mechanisms between the operating low-voltage (LV) switch and parallel external branches are presented. Experiments for the limitation of electric arc energy during inductive current interruption were performed for three scenarios: 1) for standalone operated switch (base case), 2) for passive method of arc energy limitation (widely applied RC branch connected in parallel to operated switch), and 3) active method of electric arc energy limitation (current commutation into the external semiconductor branch controlled by the microprocessor system). A typical three-phase electromechanical LV switch with double arc quenching chamber was selected as the tested object. The following parameters were investigated: electric arc resistance, electric arc power, electric arc energy, as well as power and energy generated at the external branch connected in parallel to the operating switch. Measurements were performed for current interruption in a single-phase circuit. In addition, observations of a burning electric arc in the quenching arc chamber were registered by an ultraspeed camera (for two cases: base case and hybrid switching). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Understanding mechanisms of switching transient overvoltages in modern electrical power systems is a necessity to ensure a proper design of power plants and switchgear and the required level of reliable and secure system operation. High fidelity plant modelling and accurate transient analysis is a prerequisite for understanding the mechanisms of how overvoltages are created and whether or not the voltage withstand capabilities of system components will be exceeded. This research is focused on switching overvoltages typical for an offshore wind farm power collection grid configuration that comprises vacuum circuit breakers (VCBs), cables and transformers. An in-depth understanding of the prestrike effects in VCBs is a prerequisite for studying switching transient overvoltages. In this paper, the impact of VCB parameters (e.g., stray capacitance and withstand voltage ability)and cable length on the transformer terminal voltage during closing operation was studied. A wind farm power collection system was modelled in ATP-EMTP environment. To validate the results obtained through computer simulation, field measurements from an actual system were used. [ABSTRACT FROM PUBLISHER]