Earth leakage current give rise to temperature and progressive failure of insulation which leads to operating flashover. It is essential to detect earth leakage current well before they cross threshold limits and isolate the circuit. SYCON – 771X Earth leakage Relay continuously detects the leakage current with the help of CBCT (Core Balance Current Transformer.) The CBCT is mounted externally. The overall load current whose leakage current is to be detected, current carrying cables it maybe 3 phase supply or 1 phase supply are passed through the CBCT. CBCT detects the level of current and trips the device at set current & time.