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This paper proposes a traveling wave based scheme for wye-connected shunt capacitor bank protection. The proposed method provides high sensitivity and fast response, assisting in mitigating capacitor damage during internal cascading failure. The available protection schemes for capacitor bank use RMS values of voltage and current phasors for trip decision. Threshold selection is required in these methods which needs accurate estimation of equivalent capacitance of the bank. In addition, phasor being estimated from one-cycle running data window, such a method is slow. The proposed traveling wave based method identifies an internal fault in case of opposite polarities of traveling waves seen in the terminal voltage and current signals of the faulted phase. If the mid-point tapping is available in capacitor bank, the faulted half can be identified using the traveling wave of tap voltage. The magnitude of the traveling wave in terminal voltage reveals the number of failed capacitor elements. Such information assists in expediting maintenance. The performance of the proposed method is tested using PSCAD/EMTDC simulation data for various situations, including internal short circuit, external, and identical faults in the shunt capacitor bank. Comparative analysis highlights its higher sensitivity and better accuracy in comparison to available protection methods. [ABSTRACT FROM AUTHOR]

This paper presents protection and fault location of wye-connected shunt capacitor banks used in medium or high voltage applications. The proposed method is sensitive to single element failure obtained by using voltage adaptive instantaneous superimposed current in each phase. The change in equivalent reactance computed using time-domain signals is used to find the number of failed capacitor element and types of fault. The location of the faulted capacitor is identified using sign of the voltage difference of the lower and upper halves of the shunt capacitor bank. The performance of the proposed method is tested for various cases including identical faults, simultaneous faults, system voltage unbalance in both single and double wye-connected shunt capacitor banks. The method is also validated using field data collected from a 400 kV SCB for an internal fault. The proposed technique is compared with available methods and found accurate. [ABSTRACT FROM AUTHOR]

A fast and accurate protection scheme for a dc microgrid enhances the service reliability and improves the power quality. A fault in any section of a dc microgrid results in oscillation in current, where its frequency is a function of fault position. The frequency and associated transient power of the first cycle of the oscillation are used for fault detection and faulted section identification, respectively. Based on the inverse-time transient power, a relay coordination scheme is proposed for the faulted section isolation in a dc ring bus microgrid. The maloperation of a relay due to the communication failure in the unit protection scheme can be averted by applying the proposed method using local data. The performance of the method is tested using data obtained from PSCAD/EMTDC simulations for numerous cases including bidirectional power flow situation, high fault resistance, and different fault types. The proposed algorithm is also validated on a scaled-down hardware setup in the laboratory. [ABSTRACT FROM AUTHOR]