Surge Arresters Cable and direct transformer connections within a GIS system are not susceptible to lightning strikes. Because GIS conductors are housed inside a grounded metal enclosure, the only pathway for lightning impulse voltages to enter and cause damage is through the connection of the GIS to the remainder of the electrical system. Therefore, protection at the SF6-to-air bushing connections and at transformers are the main area of concern. The zinc oxide type of surge arrester element is well-suited for immersion in an SF6 environment. These are supported by an insulating cylinder inside the GISenclosure section.
Air Insulated Surge Arresters vs Gas InsulatedAir-insulated surge arresters in parallel with the SF6-to-air bushings usually provide adequate protection of the GIS from lightning impulse voltages at a much lower cost than SF6-insulated arresters.
With the AIS - there is a significant decrease in withstand voltage for switching surges compared to lightning impulse because the longer time span of the switching surge allows time for the discharge to completely bridge the long insulating distances in air.
With the GIS - the short insulation distances can be bridged in the short timespan of a lightning impulse; so the longer time span of a switching surge does not significantly decrease the breakdown voltage. Insulation coordination studies usually show there is no need for surge arresters in a GIS; however, many users specify surge arresters at transformers and cable connections as the most conservative approach.
Surge Arresters Tester adopts a microcomputer for sampling, control, and other advanced technology, and can measure zinc oxide arrester under power frequency voltage full current, third harmonic, resistive current, resistive current peak, capacitive current, active power, and so on. And display voltage, current waveform, and printout. The use of a large screen LCD display, and menu prompts operation so that the man-machine exchange function is stronger. At the same time provide the on-site wiring display. The instrument has the characteristics of simple wiring, high measuring accuracy, and strong reliability.