SOME ASPECTS OF THE DYNAMIC RESPONSE OF DISTANCE PROTECTION.

The paper summarizes the requirements of detailed dynamic response evaluations for distance-to-fault measuring forms of power transmission line protection, and it outlines how these can be met using large-scale dynamic simulation methods. The paper investigates the dynamic response of distance protection in circumstances in which the transient content of primary voltage and current waveforms is pronounced. The case studies considered are those of operation with usually low fault levels; line energization in the presence of pre-switching short-circuit faults; and conditions in which fault current waveforms are offset to the extent of the first current-zero-crossing occurring several cycles of operation following fault onset. For each condition, protection operating delays can be expected in comparison with minimum realizable response times, but the underlying discriminative properties of present forms of distance protection appear to remain unimpaired.