GES is an earthing system created by interconnecting local earthing systems to minimise dangerous touch voltages. GES permits the division of the earth fault current in a way that reduces the earth potential rise at the local earthing system. Such system could be said to form a quasi-equipotential surface. Exposed and extraneous conductive parts are bonded together with a sufficiently dense interconnection (following the rules of main and supplementary bonding) that the rise in potential “together” ensuring NIL/MINIMUM potential difference between each item under fault conditions. No true earth reference exists and therefore safety voltages are limited.
The existence of a GES is determined by sample measurements and calculation. Typical applications of GES are
Substation surrounded by buildings with foundation earth electrode and earthing system inter connected by low voltage protective earth conductors;Substation feeding densely built up areas;Substation feeding suburban area with many distributed earth electrodes interconnected by low voltage protective earth conductors;Substation with given number of nearby substations;Substations connected via cables with earth electrode effect;Substation feeding extended industrial area;Substations that are part of system with multi earthed high voltage neural conductors.For installations where high-voltage equipment is not located in closed electrical operating areas, e.g. in an industrial environment, GES prevent touch voltages resulting from HV faults in a LV system.
