Different methods of UPS neutral and protective earthing and their impact on human safety and system disturbances

The author describes different earthing methods of AC uninterruptible power supply (UPS) systems in accordance with the TN-S system considering both neutral and protective earthing and also their impact on human safety and undisturbed operation of the current consuming equipment. Some advantages of an independent neutral earthing are described and the use of isolating transformers is recommended in many cases. The protective earthing method may be a single-point earthing or a multipoint earthing. Some arguments for the latter are highlighted and also a modified multipoint earthing method is introduced