be installed if any upgrade work is done. The incoming protective earth/neutral conductor is connected to a neutral bar (located on the customer's side of the electricity meter's neutral connection) which is then connected via the customer's MEN link to the earth bar – beyond this point, the protective earth and neutral conductors are separate. High-voltage systems In high-voltage networks (above 1 kV), which are far less accessible to the general public, the focus of earthing system design is less on safety and more on reliability of supply, reliability of protection, and impact on the equipment in presence of a short circuit. Only the magnitude of phase-to-ground short circuits, which are the most common, is significantly affected with the choice of earthing system, as the current path is mostly closed through the earth. Three-phase HV/MV power transformers, located in distribution substations, are the most common source of supply for distribution networks, and type of grounding of their neutral determines the earthing system. There are five types of neutral earthing: Solid-earthed neutral Unearthed neutral Resistance-earthed neutral Low-resistance earthing High-resistance earthing Reactance-earthed neutral Using earthing transformers (such as the Zigzag transformer) Solid-earthed neutral In solid or directly earthed neutral, transformer's star point is directly connected to the ground. In this solution, a low-impedance path is provided for the ground fault current to close and, as result, their magnitudes are comparable with three-phase fault currents. Since the neutral remains at the potential close to the ground, voltages in unaffected phases remain at levels similar to the pre-fault ones; for that reason, this system is regularly used in high-voltage transmission networks, where insulation costs are high. Resistance-earthed neutral To limit short circuit earth fault an additional neutral earthing resistor (NER) is added between the neutral of transformer's star point and earth. Low-resistance earthing With low resistance fault current limit is relatively high. In India it is restricted for 50 A for open cast mines according to Central Electricity Authority Regulations, CEAR, 2010, rule 100. High-resistance earthing High resistance grounding system grounds the neutral through a resistance which limits the ground fault current to a value equal to or slightly greater than the capacitive charging current of that system Unearthed neutral In unearthed, isolated or floating neutral system, as in the IT system, there is no direct connection of the star point (or any other point in the network) and the ground. As a result,