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Transient Inrush and Fault Current Signal Extraction Using Discrete Wavelet Transform for Detection and Classification in Shunt Capacitor Banks
(2020-03-01)
Patcharoen, Theerasak
;
Ngaopitakkul, Atthapol
An unbalanced current protection relay (60C, 51NC) cannot operate fast enough to avoid catastrophic failure against high system fault currents within capacitor units because a traditional unbalanced current protection relay is not capable of classifying the transient fault current and switching inrush current. This article proposes a new algorithm for the detection and classification of these transient current signals. Simulations are performed using PSCAD/EMTDC programs. The outputs of the current signals are used as inputs for the discrete wavelet transform (DWT) process. The wavelet-based fault and inrush current detection and classification unit receive the captured transient current signals and use DWT to detect and analyze these signals. Actual inrush current signals from an experimental setup and shunt capacitor banks of 115 kV, 22 kV, and 6.6 kV are used to verify the proposed algorithm. The results show that the proposed algorithm provides good performance and accuracy in identifying faults and inrush currents.
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Discrete wavelet transform for improving the accuracy of an unbalance current protection relay due to transient fault and inrush current signals
(2019-05-01)
Patcharoen, Theerasak
;
Ngaopitakkul, Atthapol
An unbalance current protection relay (60C, 51NC) cannot operate fast enough to avoid catastrophic failure against high system fault currents within capacitor units because traditional unbalance current protection relays are not capable of distinguishing and classifying transient fault current and switching inrush current. This paper proposes a new algorithm for the detection and classification of such current signals. The program used for the simulation was PSCAD/EMTDC. The current signals output was used as discrete wavelet transform (DWT) input. The wavelet-based fault and inrush current detection and classification unit received the various captured transient current signals, and used DWT to detect and analyse various cases studies. The actual inrush current signals from both the experimental setup and testing on an actual 115 kV HV shunt capacitor bank were used to verify the proposed algorithm. Results show that the proposed algorithm is effective at accurately identifying fault and inrush currents.
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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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The application of a 6% reactor in high-voltage capacitor bank switching
(2016-01-01)
Chiradeja, Pathomthat
;
Ngaopitakkul, Atthapol
The switching of capacitor banks at high voltage for power-factor improvement and voltage support can generate significant transients. Such switching transients are produced by inrush currents and transient overvoltages in systems to which the capacitor bank is connected. These switching transients can cause damage to insulation and mal-operation of protective relays. This paper presents the simulation and investigation of a switching large-shunt capacitor bank in a 230kV Thailand substation system. A computer simulation using PSCAD/EMTDC was performed to determine the peak of the transient currents, the oscillation overvoltage and the frequency of the inrush current. The transient inrush current is generated by energizing of the 4×72 MVAr, 230 kV shunt capacitor banks. Methods of inrush current transient analysis and reduction were evaluated. Limiting the transients with a 6% reactor in series was simulated. The simulations indicate that the 6% reactor can significantly reduce the magnitude of the transients.

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