Patent ID: 7817395

Claim:
Overvoltage protection element for discharging transient overvoltages, comprising: at least two electrodes, at least one ignition element of insulating material located between an active surface of the electrodes, and an air breakdown spark gap which acts between the electrodes when the air breakdown spark gap is ignited by an arc being formed between the two electrodes, wherein the at least one ignition element is made and arranged such that, between the at least two electrodes there is an area of weakened insulation which forms an ignition area, wherein, when there is a voltage applied to the at least one ignition element, a creeping discharge on a surface of the at least one ignition element occurs leading to a conductive connection between the two electrodes at a location bordering the at least one ignition element before an arc is formed between the two electrodes, the conductive connection having a low current carrying capacity, so that the conductive connection burns out when it is loaded with a discharge current, due to the low current carrying capacity of the conductive connection, wherein the burn out of the conductive connection causes ionization of the ignition area, so that ignition of the air breakdown spark gap between the two electrodes suddenly occurs, wherein the ignition element is made and arranged such that, when there is an arc between the electrodes, carbonization of the surface of the ignition element occurs, and wherein the at least one ignition element is made of an insulating material with a relatively low comparative tracking index (CTI) value, wherein said surface of the ignition element has a conductive coating with low current carrying capacity thereon, and wherein the coating comprises one of a chemical, thermal and electrothermal carbonization.