The distance relay for automatically sectionalizing electrical net works

This paper describes a new relay for automatically sectionalizing transmission lines, similar to existing relays in many respects, but equipped with “brains” so that it can determine the location of the trouble and govern its operation accordingly. For dead short circuit its time of operation is proportional to the distance from the short circuit so that when it is used the circuit breaker nearest to the trouble always trips out first. When applied to any system it is adjusted to fit the particular length of line which it controls and no change in this setting need ever be made due to operating conditions on the remainder of the system. Its discrimination is obtained by a time limit which varies directly as the voltage and inversely as the current existing during the trouble. It has the incidental advantage that since the circuit breaker nearest to the trouble is opened first, the final breaker to open is the one having the longer section of line in series with it to limit the current and therefore decrease the duty required of the circuit breaker.