Overvoltage protection for series capacitor equipment

An overvoltage protection device for series capacitor equipment, comprising:

• a main spark gap with a first and a second main electrode for connection in parallel with a series capacitor, and adapted to be ignited at a predetermined level of the voltage across the series capacitor, comprising:
• a series connection connected parallel to the main spark gap and including a first voltage-dependent impedance element with a predetermined knee voltage in which, when said predetermined knee voltage is exceeded, the impedance of the element drops, and a firing voltage-generating member which is adapted, upon an increase of the current through the first voltage-dependent impedance element to deliver a voltage for activating the spark gap of the overvoltage protective device;
• a first auxiliary spark gap arranged adjacent to the main spark gap for ignition thereof, with a first electrode connected to the first main electrode of the main spark gap and a second electrode connected to the second main electrode of the main spark gap;
• a second auxiliary spark gap arranged adjacent to the first auxiliary spark gap for ignition thereof, with a first main electrode connected to the first main electrode of the main spark gap and with a second main electrode connected to said firing voltage-generating member adapted to be supplied with said voltage for ignition of said second auxiliary spark gap;
• wherein said second auxiliary spark gap is so designed that, upon ignition of this spark gap, the arc in the gap is driven by current forces in a direction towards said first auxiliary spark gap for ignition thereof;
• wherein said first auxiliary spark gap is so designed that upon ignition of this first spark gap, the arc in the gap is driven by current forces in a direction towards the main spark gap for ignition thereof;
• and
• wherein said second electrode of said first auxiliary spark gap is connected to said second main electrode of said main spark gap through a first resistor for discharge of said capacitor through said first auxiliary spark gap and said first resistor before ignition of the main spark gap.