Method for the surveillance of conductor currents, and arrangement for carrying out said method

Abstract

Abstract 1. A method of monitoring conductor currents on a difference current with the following features : 1 the pre-magnetization of a magnetic core (12) is changed by the difference current ; 1.1 the magnetic core (12) has an at least approximately rectangular magnetization loop with a specific coercive field strenght (Hc ) ; 1.2 the magnetic core (12) is magnetically coupled to a write winding (8) and a read winding (9) ; characterised by the following features : 2 test pulses (P1 and P3 ) separated in time are fed to the write winding (8) with re-magnetization pulses (P2 and P4 ), superimposed upon said test pulses, producing field strenghts (HP1 , HU2 , HP3 and HU4 ) in the magnetic core ; 2.1 in terms of value the field strengths (HP1 and HP3 ) produced by the test pulses (P1 and P3 ) correspond to the difference between the coercive field strength (Hc ) and the amount of the field strength (H delta N ) produced by the maximum permissible fault current ; 2.2 in terms of value the field strengths (HU2 and HU4 ) produced by the superimposition of test pulses (P1 and P3 ) and re-magnetization pulses (P2 and P4 ) are at least twice as great as the coercive field strength (Hc ) ; 2.3 a test pulse (P1 or P3 ) and the re-magnetization pulse (P2 or P4 ) superimposed upon the latter, respectively produce field strengths with the same sign in the magnetic core (12), where in each new sequence of test and re-magnetization pulses the sign is changed ; 3 the field strength (H DELTA N ) produced by the maximum permissible difference current is smaller than the coercive field strength (Hc ) in terms of value ; 4 the sum of one of the field strengths (HP1 , HU2 , HP3 and HU4 ) and the field strength produced by the difference current induces a read signal (U9 ) in the read winding (9) ; 5 a monitoring signal (U38 ) is derived if the read signal (U9 ) falls below a predetermined limiting value (US ) in terms of value during at least one of the re-magnetization pulses (P2 and P4 ).

Inventors

• 👤 Fritz Dipl.-Ing. Breimesser

Bibliographic Details