Zero sequence current transformer works with the using
Zero sequence current protection of the basic principle is based on Kirchhoff's current law: any node in the circuit into the complex current algebra and zero. In line with the electrical equipment under normal conditions, the phase current vector and is equal to zero, zero sequence current transformer secondary winding output no signal, the actuator does not operate. When a ground fault occurs when the phase current vector and is not zero, fault current zero-sequence current transformer to the toroidal magnetic flux generated in the zero sequence current transformer secondary side voltage sensing device to perform the action, driving trip unit, switch power supply network, to achieve the purpose of ground fault protection. Effect: When the circuit in electric shock or leakage failure to protect the movement, cut off the power.
current transformer for use:
The three-phase line can be installed in a current transformer, or wires with worn once to three-phase zero sequence current transformer, the neutral line N can also be installed on a zero-sequence current transformer, use it to detect three-phase current vector and.
In the three-phase four-wire circuit, three-phase current phasor and zero, that Ia + Ib + IC = 0
If the three-phase four-wire access in a current transformer, then the induced current is zero. When the circuit of electric shock or leakage failure, circuit leakage current flowing through there, then the three-phase current through the transformer and the amount ranging from zero phase, the phase volume and the : Ia + Ib + Ic = I (leakage current)
So there is a transformer secondary coil induced voltage, this voltage is applied to the detection part of the electronic amplifier, with the current protected area unit compared to the value pre-actions, such as greater than the operating current, the relay even if sensitive, role in the implementation of components out of gate.
Then here is called the zero-sequence transformer current transformer, three-phase current phasor and not equal to zero, the resulting current is zero sequence current. Produce zero sequence current of the two conditions:
1, both the vertical fault, failure or horizontal, or normal and abnormal asymmetry, as long as the generation of zero-sequence voltage;
2, there is zero sequence current path.
These two conditions are indispensable. Because of the lack of the first, it is no source; the lack of a second, is that we often discuss "whether there must be current with voltage problems.
Zero-sequence equation: 3U0 = UA + UB + UC, 3I0 = IA + IB + IC