Reading up on 17th, the guidebook I have (ECA Guide to the wiring regulations 17th Edition, which I have fouind quite good by the way) notes that "Most modern individual pieces of equipment on a circuit creates some amount of earth leakage current and these currents add in the cirtuit's protective earth conductor'.
The go on to suggest that the circuit should therefor be designed so that the circuit runs with a standing leakage of < 25% of the rated operating current (i.e. 7.5mA I think).
2 questions are then, firstly why does the equpt do this? A result of induction/ eddy currents of some kind (perhaps switching in/out inductive loads?)
And secondly, how would you calculate/ allow for this (or would it just be based on experience)?
The go on to suggest that the circuit should therefor be designed so that the circuit runs with a standing leakage of < 25% of the rated operating current (i.e. 7.5mA I think).
2 questions are then, firstly why does the equpt do this? A result of induction/ eddy currents of some kind (perhaps switching in/out inductive loads?)
And secondly, how would you calculate/ allow for this (or would it just be based on experience)?