Improved arrangement for locating lightning strokes in the vicinity of overhead lines

摘要

936,216. Measuring transient voltages; time intervals; testing for faults. ASSOCIATED ELECTRIC INDUSTRIES Ltd. July 6, 1962 [July 6, 1961], No. 24494/61. Class 37. Apparatus determining location of a lightning stroke in the vicinity of an overhead line relatively to two stations thereon comprises means transmitting reference signals along the line at known regular time intervals and receivers responsive to arrival of such signals at the two stations and to transients in the line due to a lightning stroke; there being provided means to measure at each station the time relationship between the arrivals of the transient and reference signals. In Fig. 1, timing receivers 1, 2 are connected to the ends of a line 3 of length 2 and generator 4 emits timed reference signals into the line at receiver 1. A lightning stroke occurring at point A distant x from receiver 1 and at time tA generates transients travelling to receivers 1, 2 where they arrive at time displacements t 1 and t 2 (measured by the receivers) from the immediately preceding reference signals (Fig. 2) whose time difference at receivers 1, 2 is L -where V is the propagation velocity in the V line and the timing devices are reset on receipt of each subsequent reference pulse. It is shown V that x = -[T- (t 2 - t 1 )] where T is the time 2 interval between reference pulses. The receivers are sensitive only to the specific pulse generator signals, e.g. short oscillation trains of fixed frequency or pulse groups of characteristic duration or spacing, and the resetting circuits are provided with an auto following time gate, for protection against interference from spurious signals. The time interval between successive reference pulses is fixed in excess of twice the transit time of the line to prevent response to reflected pulses. The timing receiver 2 may be synchronized with 1 by a continuous central signal transmitted over the line from a common standard or the reference and standard signals may be provided by a continuous oscillation sawtooth frequency modulated at a period in excess of the transit time; the instantaneous frequencies at the respective ends of the line coincident with the lightning transients providing a measure of their arrival times. The reference signal may be transmitted by separate line or radio link, and the timing receivers may operate with a threshold excluding unwanted transients. Means may be provided for recording transient arrival times together with clock time, e.g. whenever a circuitbreaker trips in response to a lightning stroke ; the recordings being thereafter analysed to determine the location of each stroke of the recorded series.