GB1162811A - Improvements in or relating to Apparatus for Locating and Identifying Conductors or Faults in Conductors - Google Patents

Abstract

1,162,811. Locating cables or cable faults. A. J. BAGGOTT. Aug. 25, 1966 [May 25, 1965], No. 22254/65. Heading G1U. Apparatus for locating or identifying a conductor or a fault in a conductor consists of a transmitter circuit for generating and transmitting pulses along the conductor under the control of a switch device whose operation is synchronized in relation to the phase of an A. C. supply, the pulses being grouped in a code distinguishable from noise &c. and detecting arrangements to detect the pulses in the conductor, to enable the conductor or a fault therein to be identified or located. A cable under test 11, 12 is supplied with A.C. at its input 10. This A.C. also supplies a scaler and squaring circuit 15 and phase control 16, the output from which fires a thyristor 19 to connect a capacitor 17 across the cable lines at times predetermined relative to the supply frequency. The capacitor charging current distorts the A. C. waveform, so that a pulse is effectively applied to the cable. By appropriate connection of the scaler and phasing circuits, a coded set of pulses may be so applied to the cable, (see Division H3). The arrangement of capacitor and thyristor may be varied in accordance with the system and type of fault under test. A series arrangement of capacitor, thyristor and diode, with resistors in parallel with these components, is used to provide sharply peaked pulses for locating a healthy cable (Fig. 8). To determine the position of a short circuit in the cable, the capacitor is connected directly across the supply, and can be switched by the thyristor to discharge into the cable (Fig. 9). For an open circuit cable, the charged capacitor is discharged into a resistor connected across the cable, by switching the thyristor Fig. 10 (not shown). The detecting arrangement for sensing the coded pulses in the cable incorporates a search coil, filter and transistor amplifier. The output from this arrangement may be fed to headphones or a visual indicator.