Algorithms for Digital Distance Protection with Improved Transient Behaviour

The pliasors of voltages and currents can be calculated in real-time by using the Fourier or Kalrnan filtering. From these phasors it is possiblc to calculate the impedance of a protected line. To improve tlie transient behaviour of the algorithms we propose a new mcthod basing on a double filtering of voltage and current. The fiirlher improvement of the transient behaviour can be achieved by wing a variable sampling window. The proposed methods enable a faster prediction of desired parameters of a protected line under transient conditions.