Protection principle and power system of zero sequence current transformer

The zero sequence current transformer cooperates with the relay protection device or the signal when the power system generates the zero-sequence ground current during operation, and can operate the device component during operation to effectively realize protection and monitoring.

Zero-sequence current transformer When the electric shock or leakage fault occurs in the circuit, the secondary side of the transformer outputs zero-sequence current, so that the equipment on the connected secondary line protects (cuts off the power, alarms, etc.).

Protection principle of zero sequence current transformer

Zero sequence current transformer can be applied to each phase of a current transformer (CT) on a three-phase line, or a three-phase line can be passed through a zero-sequence CT, or a zero-sequence CT can be installed on the neutral line N. These CTs are used to detect the current vector sum of the three phases. When the three-phase load connected to the line is completely balanced (no ground fault, and the leakage current of the line and electrical equipment is not considered), Io=0, when connected on the line. If the three-phase load is unbalanced, then Io=IN, the zero-sequence current at this time is the unbalanced current IN; when a phase fault occurs in a phase, a single-phase ground fault current Id is inevitable, and the zero-sequence current detected at this time is generated. IO=IN+Id, which is the vector sum of the three-phase unbalanced current and the single-phase ground current.www.ctsensorducer.com