Abstract: In an over-voltage protection device which includes a plurality of stacks of series-connected, substantially identical surge arrester sections, each comprising an insulated casing containing a voltage-dependent resistor with a spark gap assembly, which sections are mutually electrically connected at their upper and lower ends, there is provided a triggering circuit in parallel with the arrester stacks which includes a plurality of series-connected control spark gaps corresponding to the number of arrester sections in each arrester stack and a triggering resistor connected in series with the control spark gaps. Cross-connections containing triggering impedances extend from a connection point between two control spark gaps to the corresponding connection point between two arrester sections of each of the parallel stacks. Control impedances are connected in parallel with the spark gap. The triggering impedances are constituted by resistors.

Abstract: Series capacitor blanks are inserted in high-voltage alternating current network systems in order to improve the stability of the system. Such capacitor banks are provided with a shunt-circuit for short-circuiting the capacitors if the voltage across them increases above a predetermined value at which the capacitors may be damaged or destroyed. When, in the event of a disturbance in the network, said shunt-circuit has short-circuited the capacitors, the stabilizing ability of the capacitors is gone. In order to avoid this, the capacitor bank is provided with a further shunt circuit including non-linear resistors, said resistors having a very high resistance as long as the voltage across the capacitor bank is lower than a predetermined value. Said value is higher than the noraml operating voltage of the capacitors but lower than the voltage at which the first shunt circuit short-circuits the capacitor bank.