Surge separating inductors with impedance 2÷15μH ensure energetic coordination of particular stages of overvoltage protection cascade in few cases.
They are inserted in conduct in case that the distance between 1st and 2nd stage or between 2nd and 3rd stage is smaller than 10m.
Short distance or missing surge separating inductor creates a certain possibility of damage of some arrester in overvoltage protection cascade by progressing lightning current impulse. It is important to pay a special attention to the coordination between 1st and 2nd stage of surge protection cascade in all cases where the 1st stage is fitted by spark-gap based lightning arresters.
The most economical way is to secure that the 1st protection cascade is placed in other switchboard than the 2nd stage (with the min. distance of 10m between them). If this min. distance is impossible to fulfil either from the constructive or structural reasons, it is recommended to use separating inductors of 15μH.back