High earth leakage current equipment

Section 607 - Earthing of high earth leakage current equipment... 

Electrical leakage currents, cathodic corrosion protection In electrically conductive equipment stray or leakage currents can flow as reverse currents to electric generators (in particular in the area of electric trains and major welding equipment), if, for example, conductors like rails, pipes and cable liners laid on or in the earth reduce the resistance of the reverse path, due to earth contact in faulty electrical equipment, due to induction (e.g. in the vicinity of electrical equipment with high currents or high frequencies), due to lightning. Potential equalization, respectively additional electrical override required... 

CAUTION. High leakage current Earth connection essential before connecting supply, (for stationary equipment)... 

In the case of portable equipment, testing is often carried out using a proprietary portable appliance tester (PAT). One useful test is the measurement of e insulation resistance to confirm that it is sufficiently high to prevent undue current leakage. Additionally, for class I equipment (that must be earthed) it is important to verify that the connection to earth is sound, i.e. its electrical resistance is low, and that the conductor is capable of carrying the sort of high current that may occur under fault conditions. Both the HSE and the lEE have produced guidance on electrical equipment maintenance. ... 

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