foerfarande och apparat foer at maeta och anvisa avstaondet till i intraeffad kortslutning eller liknande linjefel pao, i vaexelstroemskraftlinje

摘要

This method and apparatus is primarily intended for use in combination with a distance relay adapted to actuate a line switch or breaker (B) when sensing a line fault on the line, the short time interval available within the tripping time of the line breaker before disconnecting the line being utilized for performing measurements to locate the occured fault. These measurements are performed by means of an impedance relay (XR, R) disposed to receive two measuring signals (E, dI/dt) derived from sensed line voltage and current, respectively, and to respond to these signals when their mutual proportion corresponds to a line impedance which is less than a limiting impedance of the relay. During the time interval available for measurements this limiting impedance is reset by time controlled switching means (K) to a different value for each half cycle or other suitable given time period subsequent to the detected short circuit. Each such different reset limiting impedance value corresponds to a predetermined portion of the line length, and the sequence of limiting impedances is set in accordance with a predetermined switching programme (Fig. 1), which may be optimised to obtain maximum information as to the line fault location during the time span available before the power line is disconnected. During said switching programme a detector unit (A1-A4, B1-B4, a, b, c, d) registers consequently whether the respective set limiting impedances allow or do not allow the impedance relay (XR, R) to respond to the received measuring signals. Based on the information thus obtained by the detector, the location of the line fault is displayed on a distance indicator.