Energy modes-based differential protection for Shunt capacitor banks

摘要

This work introduces a differential protection method for early detection of a fault in a single-capacitor into a capacitor bank configuration. This protection has the aim to discriminate between internal faults from transient conditions such as capacitor bank energisation. The method uses singular value decomposition to process the instantaneous operation and restraint currents. The proposed algorithm is defined by the largest singular value (LSV) named as energy mode. To obtain the LSV, the scheme pre-processes the operation and restraint currents by using a filter and normalization stage. The adverse impact associated with CT saturation or noise is addressed with the numerical integration of LSV. Additionally, the numerical differentiation is calculated to speed up the fault detection time, which is compared against a fault detection threshold (FDT). If the magnitude of the numerical differentiation is higher than the limit, a fault will be declared. Otherwise, a transient or steady-state period will be identified. The method does not depend on the capacitor bank parameters or the network configuration; the FDT is a unique setting; the algorithm is capable to detect at least one faulted capacitor in the capacitor bank; the fault detection time reported is less than one cycle regarding the fundamental frequency.