On-line detection of loss of synchronism using locally measurable quantities

Maintaining dynamic security of a power system subjected to large disturbances is of utmost importance. Fast and accurate on-line detection of instability is essential in initiating certain emergency control measures. The techniques reported in the literature involve mainly application of global phasor measurements and heuristic algorithms. In this paper, an accurate technique for the on-line detection of loss of synchronism based on voltage and current measurements in a line is presented. The technique makes use of the concept of potential energy in a line. The conditions for the system instability are derived from energy function analysis. However no assumptions are made regarding the power-angle relationship in a line, nor any data on the system equivalents are necessary in implementing the detection scheme which is simple and requires only local measurements