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Author: search.filters.author.Pothisarn, ChaichanSubject: search.filters.subject.Inrush current

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    Simulation analysis of the switching of 230kV substation shunt capacitor banks with a 6% series reactor for limiting transient inrush currents and oscillation overvoltage
    (2018-06-01)
    Patcharoen, Theerasak
    ;
    Ngaopitakkul, Atthapol
    ;
    Pothisarn, Chaichan
    ;
    Leelajindakrairerk, Monthon
    This paper presents the simulation and investigation of switching large shunt capacitor banks in a 230kV Thailand substation system. Simulations are performed using PSCAD/EMTDC to determine the peak of the transient inrush currents, the oscillation overvoltage and the frequency of the inrush current. The inrush current is generated by energizing the 4 × 72 Mvar, 230kV shunt capacitor banks. The purpose is to observe and investigate the behaviour of transient inrush currents and oscillation overvoltages to ensure the safe and successful operation of shunt capacitor banks. The methodology of inrush current transient analysis and transient reduction control was studied. The proposed method for controlling system transients during capacitor energization is through the use of a switching shunt capacitor bank with a series 6% reactor. The simulation cases for transient mitigation are numerically conducted for six different cases: a base case, with a pre-insertion resistor, with a pre-insertion inductor, with a current-limiting reactor, with a series 6% reactor and using synchronous closing control. The effects of parameters such as the sizing of the current-limiting reactor, the capacitor bank rating and the short-circuit impedance of the system are investigated. The simulation results demonstrate that the switching shunt capacitor bank with a series 6% reactor is effective in reducing the high transient inrush currents and oscillation overvoltages.
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    Investigation and reduction of effects of transient signals for switching capacitor into a power system by using an experimental test set
    (2018-01-01)
    Yoomak, Suntiti
    ;
    Pothisarn, Chaichan
    ;
    Jettanasen, Chaiyan
    ;
    Ngaopitakkul, Atthapol
    This paper aims to investigate switching capacitor bank of the 115 kV Nong Chok substation under the Electricity Generating Authority of Thailand (EGAT). The substation comprises of 3 steps capacitor banks with reactive power of 48 Mvar in each step. In case study, the substation is downscaled to be an experimental unit with 415 V and 5 Mvar in each step in laboratory. Inrush currents, the behavior of transient signals, that occurs when capacitors are switched into the system are studied and analyzed. To reduce the effect of switching capacitors, current limiting reactors connected in series with the capacitors are proposed. In addition, a zero-crossing circuit is designed to control switching angle of the capacitors, since it has a significant effect on the inrush currents. The results of experiment are compared with two case studies: switching capacitors without integrated 7% of reactors and switching capacitors with integrated 7%. It can be summarized that the switching capacitor without integrated reactors has inrush currents change based on the switched angles of the capacitors. However, the switching capacitor with integrated reactors gives inrush current values are almost approximate in each angles of switching and they are lower the case of the switching capacitor without integrated reactors. Nevertheless, reactor integration into the system leads to high current values at the steady states.