Patent GB-450543-A (GB)
Title: Improvements in or relating to apparatus for measuring electrical quantities
IPC: G01R13/00
Filed: 1935-01-18
Abstract: 450,543. Current and pressure meters ; detecting and locating faults. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, LEESON, B. H., Waverley, Tynemouth, LEYBURN, H., 212, Wingrove Road, Newcastle-on-Tyne, and MILLS, A. W., 43, Cedar Crescent, Low Fell, Co. Durham. Jan. 18, 1935, No. 1696. [Class 37] Apparatus for measuring electrical quantities, including transient quantities such as the voltage and current during a surge in a transmission system, comprises a meter, of the kind in which the torque exerted on the moving member depends on the value of the energizing current, and means for supplying an impulse of predetermined duration to the meter so as to impart to the moving member a momentum proportional to the quantity to be measured, a measurement of this momentum being made before the moving member comes to rest. The measuring instrument is preferably of the moving coil or moving iron repulsion type and has a spindle B, Fig. 1, carrying a pointer B<1> which travels over a scale B<2> a damping device, in the form of vane G<1> attached to the spindle and moving in an air dashpot G<1>, being provided to render the scale B<2> approximately uniform. No control spring is provided, the spring B<3> being only just sufficient to return the pointer to zero when the meter is de-energized, so that when an impulse is passed through the meter, the pointer swings freely across the scale until a clamping device is operated which clamps the pointer in its deflected position. The clamping means comprises a spring-held, pivoted frame D, carrying wires D<2>, D<3> which are brought into engagement with a ring on the spindle B by the operation of an electromagnet F. When the device is used for measuring voltage and current flowing under fault conditions, two meters I, V, Fig. 2, are employed, one for measuring an impulse which is proportional to the fault current and the other an impulse proportional to the fault voltage in the single phase A.C. circuit H, H<1>. The meters are operated by a single relay comprising a shaft J<1> which is driven by a clockwork motor or other constant speed mechanism, on the release of a stop J<2> by the energization of an electromagnet K when the fault current in the power circuit H, H<1> exceeds a predetermined value, and the rotation of the shaft J<1> continues until a second stop J<3> engages a fixed stop J<4>. The shaft Jl carries three contact discs M, N, O ; the disc M serves to short-circuit the meter I until the brushes M<1>, M<2> engage insulating strips M3 when an impulse is passed through the meter I, and at the same time an impulse is passed through the meter V by the brushes N<1>, N<2> which engage conducting strips N<3> on the disc N and connect the meter V in circuit. As the brushes pass off the strips M3, N<3>, the circuits of the meters are broken, but their pointers continue to move until conducting strips 0<3> on the disc 0 engage brushes O<1>, 02 when the coils F<1> F<2> operating the clamping devices for the meter pointers are energized and the pointers are thus clamped after a predetermined time. When the fault current and voltage are measured simultaneously, the approximate position of the fault can be calculated. If only one quantity is to be measured, a simpler form of relay may be used which is provided with an operating coil energized by the supply and controlled by a damping device so as to have a constant and predetermined time of operation. Three sets of contacts may then be provided to take the place of the strips M<3>, N<3>, 03 on the discs M, N, 0, or a second relay may control the third set of contacts which operate the clamping electromagnet of the meter. When a number of current meters is provided on a network, the section in which a fault occurs and the fault current and voltages may be indicated by providing a self-setting device for the clamping mechanism of each pointer which operates under a time-lag relay control to re-set the clamping mechanism of those meters appropriate to those sections in which the occurrence of the fault has not caused the isolation of the section by operation of the circuit breaker. The device may be used on D.C. or A.C. systems and also for measuring normal currents and voltages. These meters may be connected in circuit either directly, or through a transformer or shunt, and the range of current faults which can be measured can be increased by using two or more meters connected in series.