Adaptive digital distance protection

Since the state-of-the-art for microprocessors now allows for ever increasingly rapid calculation of results, the field of digital distance protection in power systems is now extending itself to include other power system contingency conditions. The authors extend this field of study by describing simulation studies performed in developing a digital distance relay which is capable of adapting itself to onerous power system conditions such as power swings and high-resistance earth faults. It is shown that the relay is capable of reliable and discriminative operation. The work has been computer simulated and attention has been paid to ensure that the simulation closely emulates the operation of prototype hardware under development. This includes a 16 bit microprocessor with the relay analogue measurands being digitised by a 14 bit A/D converter at a 4 kHz sample rate