DIGITALRECHNER-DIFFERENTIALRELAIS.

摘要

In differential function calculation processing (1), a value of differential function f(d) is calculated using differences between a plurality of predetermined number p of differential current data Dd sampled at different sampling times. The differential current data is data obtained from differential current Id or a sum of data Dj (j = 1 to n where n is the number of the respective terminal currents) obtained from respective terminal currents Ipj. In restraint data calculation processing (2), restraint data Dr is calculated using respective terminal current data Dj sampled at the same sampling time. In restraint function calculation processing (3), a value of restraint function f(r) is calculated using differences between a plurality of predetermined number p of restraint data Dr sampled at different sampling times. Then, in comparison processing (4), the value of differential function f(d) is compared with the value of restraint function f(r). If the value of differential function f(d) is smaller than a value, modified by a predetermined relationship, of restraint function f(r), an inhibit output (S2 or f(s)) is generated in the comparison processing (4). Differential relay processing (5) inhibits a trip operation of a circuit breaker by the inhibit output (S2 or f(s)) from the comparison processing (4). The differential relay processing (5) is so controlled as to execute the trip operation when the inhibit output (S2 or f(s)) is not present.