LINE DIFFERENTIAL PROTECTION SYSTEM FOR A POWER TRANSMISSIONLINE

摘要

In a power line current differential protection system, all three phase current values (IA, IB, and IC) are obtained from both the local end and the remote end of a power transmission line (12). The magnitude of the ratio of the remote current values to the local current values are calculated. Also, the angle difference between the local and the remote current values for eac h phase are calculated. Comparison elements (40, 42) then compare the ratio an d angle values against preselected values which establish a restrain region in the current ratio plane. Current values which result in the ratio being with in the region do not result in a tripping signal for the circuit breaker on the power transmission line (12), while current values which result in a ratio outside of the region result in a tripping of the circuit breaker. Similar circuitry is used for negative sequence current quantities, with the negativ e sequence preselected values being set substantially lower to produce a more sensitive response to possible faults in the line.