I'd be grateful for people's views on the wisdom of including an inductive filter (for fast transient suppression) in the protective earth conductor of a device. Since safety in the event of a fault to earth relies. in most installations. upon automatic disconnection of supply, which in turn relies upon low-impedance earth-fault loop, does the inclusion of an inductance in this loop not then compromise this safety feature by potentially increasing disconnection time in the event of such a fault? (the shock hazard being a function of duration as well as magnitude) Furthermore, that part of earth-loop impedance attributable to the device, rather than the installation, is tested by DC earth bond resistance measurement. How valid a measure is this with an inductance present, since the earth-fault will not be DC but at mains frequency and typically generated as a transient step-type function when the fault occurs (to which the inductance will present a much higher impedance). Thanks Ged Dean ________________________________
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