Patent GB-705398-A (GB)
Title: Improvements in or relating to electric signalling arrangements for protective or other purposes
Inventor: HAMILTON FREDERICK LESLIE
IPC: H04B3/11
Filed: 1951-04-09
Abstract: 705,398. Protective cut-out arrangements. REYROLLE & CO., Ltd., A. March 27, 1952 [April 9, 1951], No. 8191/51. Class 38(5) A two-way signalling circuit, particularly a pilot circuit for a protective arrangement in which the currents at the ends of a protected section are compared, comprises a single pair of pilot wires D, D<SP>1</SP>, a source of A.C. A, A<SP>1</SP> and a rectifier B, Bl at each end in series with the pilot circuit, the rectifiers permitting unidirectional current to circulate in the pilot circuit, and a shunt circuit at each end having a rectifier C, C<SP>1</SP>; opposed to the adjacent series rectifier B, B<SP>1</SP> so that current from the remote and not the adjacent source can flow through a shunt circuit. If the currents at each end are in phase with one another, then current will flow during one half cycle from the source A through the rectifier B, the pilot wires and the remote shunt circuit C<SP>1</SP>, E<SP>1</SP> and energize the " receiver " E<SP>1</SP>. This current does not flow through rectifier B<SP>1</SP> and source A<SP>1</SP> as it is opposed by the source A<SP>1</SP>. During the other half cycle the " receiver " E is similarly energized from the source A<SP>1</SP>. If the currents at each end are in phase opposition, current flows during one half cycle from both sources round the pilot circuit but not through either shunt. circuit as the resultant voltage across each shunt, circuit is in the reverse direction for conduction through the rectifier C, C<SP>1</SP>. On the other half cycle, the rectifiers B, B<SP>1</SP> prevent the flow of current in the pilot circuit so that the receivers E, El remain de-energized. In Fig. 2, this pilot circuit is used to protect a feeder H<SP>1</SP> ... H<SP>3</SP> . and is supplied by summation transformers G. F, G<SP>1</SP>, F<SP>1</SP>. Connected in each shunt circuit is the biasing winding M, M<SP>1</SP> of a relay having an operating winding L, L<SP>1</SP> energized by a tertiary N, N<SP>1</SP> of the adjacent summation transformer. To provide a continuous secondary load for the transformers, a rectifier P, P<SP>1</SP> and a resistance O, O<SP>1</SP> are connected across a portion of the secondary winding F, F<SP>1</SP> of each summation transformer to provide a load circuit in which current flows during the half cycles in which the transformer is not supplying the pilot circuit. Non-linear resistors Q, Q<SP>1</SP> limit the voltage applied to the pilot circuit.. Under through fault conditions, the current in the secondary windings F, F<SP>1</SP> are in phase and the biasing windings M, M<SP>1</SP> are energized as described above to restrain the relays from operaton. In the event of an internal fault, the current in F, Fl are substantially in phase opposition, the windings M, M<SP>1</SP> are not energized and the relay windings L, Ll operate the relay to trip circuit breakers K, K<SP>1</SP>. In a modification, Fig. 3 (not shown), each winding M, M<SP>1</SP> is arranged as the D.C. biasing winding of a transductor, each transductor having an operating winding connected across the secondary winding F, F<SP>1</SP> and a secondary winding supplying a sensitive D.C. relay through a full-wave rectifier. Each transductor may have a short circuited smoothing winding and each smoothing winding may have a rectifier in circuit with it to make the output of the transductor dependent on the phase relationship between the operating and biasing currents.