Spark Prevention Unit (SPU) is designed for surge arresters that are installed in wildfire risk areas. It monitors the current and the thermal load of the surge arrester. In case of a thermal overload, it interrupts the current flow and disconnects the surge arrester thus preventing any arcing, sparking or ejection of hot particles that may have the potential to start a wildfire. When operated, SPU gives an indication that is easily visible from the ground level.
Medium-voltage surge arresters equipped with SPU from Hitachi Energy are approved for vegetation clearance exemption according to CalFire (California Regulation). They are also considered spark-free according to class A of Australian Standard AS 1307.2.