Understanding LV Earthing Systems: TT, TN, and IT Explained Earthing systems are crucial for electrical safety, protecting people and equipment from faults and shocks. In low-voltage (LV) installations, the IEC 60364 standard defines three main earthing systems: TT, TN, and IT , each with distinct characteristics and applications. This blog post explains these systems, their subtypes, and key safety considerations, referencing the attached technical screenshots for clarity. 1. Classification of LV Earthing Systems Earthing systems are identified by a two-letter code : First Letter: Neutral Connection T (Terra) – Neutral is directly earthed at the transformer. I (Isolated) – Neutral is not earthed or connected via high impedance (≥1000 Ω). Second Letter: Equipment Earthing T – Frames are locally earthed , independent of the neutral. N – Frames are connected to the neutral , which is earthed at the transformer. 2. Typ...