Problems at the utility supply/consumer interface

The interface between the electric utility companies´ distribution network and low-voltage installations in large buildings in Hong Kong is defined by both policy and ordinance. The logic of requiring LV systems to satisfy both TN-S and TT earthing is questionable. Arguably it is not possible to achieve separation of transformer earthing and consumer earthing, so a TT classification is overly simplistic. Adherence to, or confusion resulting from, these earthing regulations can compromise operating reliability and electrical safety. It is doubtful that all the requirements of Section 11 of the Electricity (Wiring) Regulations are fulfilled