Online real-time calculation of short-circuit current based on improved gradient estimation algorithm

One of the key problems to implement the intelligent operation of high voltage circuit breakers, is to obtain the fundamental parameters of short-circuit current quickly, accurately and in real-time, before the breaking signal being sent out. A new algorithm, improved gradient estimation algorithm, is put forward to decrease the calculating time required. Three different sampling jumping-off points are utilized on-line to add new information continuously, and then to correct the estimated parameters of short-circuit current in real-time, so that the influence of the dc component on the estimation result could be decreased. Decay time constant and the original fundamental phase angle are specially selected as research objects to validate the algorithm proposed. Through simulation, the algorithm is able to calculate parameters of the fundamental frequency component current exactly, within 18 microseconds after short-circuit condition occurred, with a 40 dB noisy interference. Hence the algorithm accords with the request of intelligent operation basically.