GB216924A - Improvements in or relating to electric protective systems - Google Patents

Abstract

216,924. Electrical Improvements, Ltd., and Grant, L. C. March 2, 1923. Protective arrangements.-In a system for the protection of feeders in the event of faults or other disturbances, in which pilot wires are dispensed with by utilizing high frequency oscillations. two oscillatory circuits are provided, one of which is adapted to be controlled by disturbances or variations from normal conditions in the main protected circuit whilst the other is responsive to the oscillations generated by the first circuit and supplies current to operate a circuit-breaker to disconnect the faulty feeder. In the arrangement shown in Fig. 2, in which a disturbance in the protected circuit operates circuit-breakers at a distance, two oscillatory circuits are employed one responsive to the disturbance and adapted to convey energy by wired wireless means to a receiving circuit. The transmitting circuit comprises a thermionic valve B a tuning coil C and condenser C' for the anode circuit, a tuning coil D and condenser D<1> for the grid circuit and the necessary sources of current for example the transformer E, E', E<2> of which the primary E is supplied with alternating current from the circuit to be protected. the portion E<2> of the secondary supplying the filament and the portion E<1> supplying the high tension to the anode through a rectifier E<3>. The receiving circuit comprises a receiving valve L and an amplifying valve N, the usual high and low tension batteries and the transformer P, P<1>, connected up as shown. Line coupling devices consisting of dead-ended conductors H, S lying alongside the main conductors are connected to the oscillatory circuits which are connected to earth, as shown at G and R. A disturbance on the main A actuates a relay located, for example, in the circuit F and generates oscillations which in the receiving circuit cause the operation of the relay Q to isolate the system. In the balanced system shown in Fig. 1, two oscillatory circuits each similar to the transmitting circuit of Fig. 2 but containing the tripping relays K in the earth connection G are arranged one at each end of a feeder each adapted to generate high frequency oscillations and to receive the oscillations generated by the other. Means are provided consisting of an auxiliary circuit containing a current transformer in the feeder and connected at F or F<1> to F<3> for controlling the oscillations generated by each of the circuits in accordance with variations from normal conditions in the protected conductor so that each circuit reacts on the other in the manner of a balanced system. Telephone wires may be used for the wired connection between the oscillatory circuits.