Electrical isolation and operation of zero sequence current transformer

- Jun 01, 2019-

In the process of operation, the zero sequence current transformer is mainly based on the principle of electromagnetic induction, which effectively converts the primary side current into the secondary side small current to measure the instrument. In operation, the current transformer is closed iron. Core and winding composition. It has a small number of turns on the primary side winding, which is in the line of the current that needs to be measured.

The zero sequence current transformer often has all the currents flowing through the line. When the operation is performed, the number of turns of the secondary side winding is relatively large, and is connected in series in the measuring instrument and the protection circuit. The current transformer is connected in series and in the protection circuit. The impedance of the current transformer is small and the operating state of the current transformer is close to a short circuit. When the current mutual inductance works, its secondary side circuit is always closed, so the measuring instrument converts the primary side large current into the secondary side small current to measure, and the secondary side cannot open the circuit.

Zero sequence current transformer have large currents in power generation, substation, transmission, distribution, and power lines, ranging from a few amps to tens of thousands of amps. In order to facilitate measurement, protection and control, it is necessary to convert to a relatively uniform current. In addition, the voltage on the line is generally high. Direct measurement is very dangerous. The current transformer acts as a current transformer and electrical isolation.

In the process of installation, the  zero sequence current transformer must ground the cable head through the zero-sequence CT, so as to ensure that the fault current and the non-fault phase capacitor current pass through the grounding point, which can prevent the protection device from malfunctioning when the fault occurs outside the zone. It can also ensure reliable operation of the device when the fault occurs.www.ctsensorducer.com