The system typically starts at the power distribution cabinet or room, then passes through a secondary distribution box (also known as a sub-panel) and finally reaches the switch box (the third level), which connects directly to the electrical equipment. In a TN-C system (Figure 2), the neutral and protective functions must be integrated into a single conductor (PEN) throughout the entire system. This is because TN-C requires an exemption from the Electricity Safety, Quality and Continuity Regulations, and an IT system is not permitted for a low voltage public supply in the UK because the source is not directly earthed. Therefore TN-C and IT systems are both very uncommon i RTHING. TN-C-S earthing system (or TN-C-S system): a distribution system in which one live part of a power source is earthed, exposed-conductive-parts of an electrical installation are connected to the earthed live part of the power source in a head part of the electrical installation (from the power. The IEC 60364 standard defines three main types of Earthing Systems: TT, IT, and TN. As IEC leads the global standards in electrical, electronic, and related technologies, the IEC 60364 standard serves as the highest authority for LV Electrical Installations worldwide. Consequently, many national. For ASEA Power Systems, grounding takes on particular importance when working with the three main earthing systems: IT, TT, and TN-S.
