GB1360455A - Remote control systems - Google Patents

Abstract

1360455 Signalling over power lines BROWN BOVERI & CIE AG 8 Oct 1971 [10 Oct 1970] 46998/71 Heading H4R In an arrangement for remote control signalling over a multiphase power distribution system, in which the signals are introduced into the system at spaced points by working simultaneously transmitters synchronized and supplied with control pulses from a common point, each transmitter includes a pulse oscillator, normally synchronized by synchronization signals from the common point, and driving a counting ring which functions as a grid control set for a multiphase inverter, and monitoring circuitry in each transmitter responds to loss of synchronization signals to prevent resynchronization upon restoration of these signals until the end of the next control pulse, and is adapted to inhibit the synchronizing signals during periods in which distortion of those signals is detected. The Figure shows a single transmitter coupled to a common source 2 of synchronizing frequency and a common source 10 of information pulses. The synchronizing frequency is converted to square wave at 4 and normally passes through a gate 13 is differentiated at 7 and passes through a gate 14, synchronizing an oscillator 6 producing three pulses per differentiation pulse. For each information pulse from source 10 a bi-stable 11 is set allowing the pulses from oscillator 6 to cycle a ring counter 8 through its active states enabling the grids of valves in the multi-phase inverter 1 causing a multi-phase pulse to be transmitted to the power system. The trailing edge of the information pulse triggers a monostable 21 which resets the bi-stable 11 resetting counter 8 and closing gate 12. Each pulse from the squarer 4 are also delayed at 19 for part of the duration of a pulse and triggers a monostable 20 producing pulses of standard form which are inverted and applied to AND gate 14. The pulses of the inverted waveform normally enable gate 14 in time to pass the next differentiated pulse, but if distortion causes two successive positive pulses from 4 to be closely spaced in time the gate 14 does not open in time to pass the second differentiated pulse. The standard pulse output of monostable 20 is also applied without inversion to an integrator 16 adapted to set a bi-stable 17 if no pulses are received over a period. Setting of the bi-stable blocks an AND gate 13 blocking the synchronizing signal supply to the oscillator which continues without synchronization. Bi-stable 17 is only reset opening gate 13 at the end of an information pulse by monostable 21 via a delay 22. Thus when the synchronizing signals reappear synchronization can only occur between information pulses and all transmitters remain in phase.