Interposing CT (ICT) in Transformer: Working Principle & Ratio Calculation Explained

Interposing CT (ICT) in Transformer Differential Protection | Calculation & Working Explained In this video, we explain the role, working, and calculation of an Interposing Current Transformer (ICT) used in transformer differential protection schemes with electromagnetic relays. An ICT is used to compensate for CT secondary current mismatches, correct phase displacement, and prevent unwanted relay operation during normal operating conditions. ⚡ Topics Covered in This Video: 🔹 Purpose of Interposing CT (ICT) Ratio correction between HV and LV CT secondary currents Vector phase correction for star-delta power transformers Zero-sequence current filtering to prevent unwanted tripping 🔹 Interposing CT Ratio Calculation 07:11 – 08:13: Calculation of transformer full-load current using the three-phase power formula 08:14 – 10:08: Calculation of HV and LV main CT secondary currents 10:33 – 13:48: Calculation of the required ICT ratio to balance the currents supplied to the differential relay 🔹 CT and ICT Connections 13:48 – 14:50: Main CT star connections and ICT delta secondary connections for electromagnetic differential relays 🔹 Working Principle How an ICT balances the currents on both sides of a transformer How phase compensation and zero-sequence filtering improve differential protection stability 📌 Why Is This Important? Correct ICT ratio selection and connection are essential for achieving current balance under normal operating conditions and ensuring reliable operation of transformer differential protection during internal faults. Electrical Engineering Students Electrical Engineers and Maintenance Professionals Power System Protection Engineers Candidates preparing for Electrical Engineering Interviews and PSU Exams 📺 Watch more electrical engineering tutorials on Electrical Express for practical explanations of transformer protection, CTs, relays, and substation equipment. 👍 Like, Share, and Subscribe to Electrical Express for more technical videos! #InterposingCT #ICTCalculation #TransformerDifferentialProtection #DifferentialRelay #CurrentTransformer #TransformerProtection #ElectricalEngineering #PowerSystemProtection #ElectricalExpress #ElectricalInterview