Short-circuit direction indicators

摘要

The invention relates to short-circuit direction indicators for high-voltage lines fed from two ends in three-phase systems. In such devices, it is usual to use a capacitive sensor for the voltage and an inductive sensor for the current and to transfer the sinusoidal quantities via Zener diodes in trapezoidal form. It is the object of the invention to improve known devices by simple means in such a manner that they still reliably indicate even with a collapse of the voltage in the short-circuit case. This is achieved by the fact that the star or delta voltage triggers a synchronous oscillator (2) which continues to run with the correct phase in the short-circuit case and is used as phase frequency, that the signals (U20, U21) of the sensors (1, 3) are supplied to a drive logic (4) and that the drive logic (4) output is connected to a phase measuring unit (6) consisting of logic gates, the output of which feeds direction indicating elements (LED1, LED2). <IMAGE>