Effect of External Air Gap Length on Electric Arc Behavior in Multi Chamber Arresters under Different Lightning Polarities

Lightning poses significant risks and many problems for devices in power networks. Continuous advancements in protective technologies are crucial for enhancing the resilience of power systems against the natural phenomena. One of the protective devices that is used in the power network is multi chamber arrester (MCA). In this arrester, the External Air Gap (EAG) between the energized conductor and terminal electrode of MCA has important role in initial breakdown under lightning impulse overvoltage. Also, the polarity of lightning significantly influences the performance of this arrester. On the other hand, the design of EAG can satisfy reliability of MCAs in protecting the electrical systems against lightning. According to the standard, the EAG length can be considered as 70±10 mm. In this paper, the effect of this length on the arc behavior is evaluated under different lightning polarities. Then three important arc parameters such as electric field, velocity and conductive heat flux were analyzed. According to the results, for a smaller EAG, the arc velocity in EAG and discharge chamber of MCA are higher than other states under both polarities at initial times. Therefore, the arc is discharged in a shorter time and the arrester operation is better than other states.