Modern numerical transformer protection relays have powerful logic to prevent unwanted tripping on phase differential during CT saturation for external faults. To demonstrate these protection features, we will simulate the low-side fault. Differential current protection, much like a ground-fault interrupter (GFI), measures incoming and exiting current from all three phases, stopping the circuit in case of any imbalance, no matter how long it persists. One of the fundamental laws of electric circuits is Kirchhoff's Current Law, which. Abstract—Validating proper current transformer (CT) and voltage transformer (VT) wiring, terminations, and grounding is fundamental to successful performance of the protection system. Occasionally, errors in CT and VT connections can occur, such as missing or broken neutral wires, multiple or. Medium voltage switchgear is used for switching medium voltage loads through associated control, measuring, protective and regulating equipment. This operation also involves considerable manual intervention which therefore necessitates the fulfilment of safety requirements laid down in. These auxiliary switches are designated as follows: 5. The Current flow in each phase of the CT is monitored by the CT supervision relay.