Patent ID: 8792216

Claim:
A method for protecting against a failure within a multi-phase capacitor bank comprising a plurality of capacitor units each comprising a plurality of capacitor elements connected to each other, wherein capacitor units are connected to each other, the method comprising the steps of: measuring a current of each individual phase of the capacitor bank, calculating a magnitude of an unbalanced current based on the measured currents, measuring a voltage of each individual phase of the capacitor bank, calculating a magnitude of an unbalanced voltage based on the measured voltages, determining an operating point location in a specified operating region based on the calculated magnitudes of the unbalanced current and the unbalanced voltage, and initializing a trip signal based on the location of a defined operating point in the specified operating region, wherein the specified operating region is a part of an operating plane defined by the first quadrant of a two-dimension Cartesian coordinate system having an X axis and a Y axis representing unbalanced voltage and current, the operating plane is divided into a restraining region and the specified operating region by a limit line, in the case that the defined operating point is in the restraining region, no trip signal is initialized; and wherein the capacitor bank has rated current and voltage, the X-axis of the operating plane defined by percent of the magnitude of the rated voltage of the capacitor bank and the Y-axis of the operating plane defined by percent of the magnitude of the rated current, the limit line includes a part of a straight line extending through the origin of the plane with a slope of 1.