GB1101845A - Improvements in sparkover control circuit for lightning arrester shunt gap unit - Google Patents

Abstract

1,101,845. Surge diverters. GENERAL ELECTRIC CO. 18 March, 1966 [22 March, 1965], No. 11981/66. Heading H2H. In a lightning arrester for very high voltage systems of the type in which additional valve resistance material (4) is shunted by a spark gap unit 5 responsive primarily to lightning surges, Fig. 1 (not shown), the unit 5 comprises main gaps G<SP>1</SP> ... G 5 which have substantially the same individual spark-over voltage and are sequentially fired at an applied voltage across terminals 6, 7 whose value may lie between the individual spark-over voltage and the sum of all the spark-over voltages. The firing voltage in the range up to twice that of an individual gap is determined by the value of resistor R 2 , higher spark-over levels being achieved by adding a resistor in series with auxiliary gap S 3 (above the junction with R 5 ) and another in series with the gap S 4 . The auxiliary gaps S 1 . . . S 4 act as pre-ionizers for the respective gaps G 1 - - - G 4 and control the sequential spark-over of these gaps, each gap S 1 . . . S 4 having an individual spark-over voltage about half that of the gaps G 1 . . . G 4 . A coil 8 provides magnetic blow-out for the arcs in the gaps G 1 . . . G 4 which may be of the horn gap type. Capacitor C 1 ensures that the spark-over voltage of the unit 5 is substantially independent of the wave shape of the applied voltage, and capacitor C 2 short-circuits the coil 8 until after the gaps G 1 - - . G 4 have fired. A typical operation is described in which gaps G 1 . . . G 5 are sequentially sparked over in that order. In a modification, Fig. 3 (not shown), the gaps S 2 , S 3 , S 4 are replaced by corona-type pre-ionizers shunted by resistors which, with members R 1 8, form a voltage divider network after the gap S 1 has sparked over. Compensation for applied voltage waveshape is provided by two capacitors respectively connected across the gaps G 3 , G 4 , these capacitors also contributing to the sequential operation of the unit.