neutral solidly earthing
solidly earthed system are characterised by high level of fault current.
high value earth faults can be cleared quickly they can also lead to damage that is dificult to repair
solidly earthed system provide the best control of transient and temporary overvoltage that can arise btween earth and the electrical system..
insulation that is applied between phases and earth can be rated based on the phase to earth voltage.
lower rated insulation can reduce the cost of electrical system and equipment.
isolated system have one big advantage they continue operating in the presence of a single earth fault there is because thee is no rturn path available for the flow of earth fault current hence protective devices will not operate.
isolated system also have big disadvantage transient temporary and permanent overvoltage can easly occure on such system, stressing insulation.
insulation that is applied between phase and earth must be rated based on the phase and phase voltage, and often for even higher voltages.
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