What is the working principle of the residual current circuit breakers?
1. When the leakage of electrical equipment occurs, there are two anomalies:
(1) the balance of the three-phase current is destroyed, there is zero sequence current;
(2) normal non-charged metal shell to ground voltage (normal, the metal shell and the earth are zero potential).
2. The role of zero sequence current transformer residual current protection device through the current transformer to detect abnormal signals, through the intermediate mechanism conversion transfer, so that the actuator action, through the switch device to disconnect the power. The structure of the current transformer is similar to that of a transformer and consists of two coils wound around the same core. When a coil has a residual current, the secondary coil will sense the current.
3. The residual current circuit breakers installed in the line, a coil and the grid connected to the line, the secondary coil and leakage protector in the release of the connection. When the electrical equipment is running normally, the current in the line is balanced, the sum of the current vectors in the transformer is zero (the current is the direction vector, such as the direction of the outflow is "+" and the return direction is "-" Transformers in the current from the same size, the opposite direction, positive and negative offset each other). Since there is no residual current in the primary coil, the secondary coil is not induced, and the switching device of the residual current circuit breakers is in the closed state. When the equipment shell leakage and someone touched, then the fault point in the shunt, the leakage current through the human body, the earth, working ground, return to the transformer neutral point (not the current transformer), resulting in the transformer into the flow The current is unbalanced (the sum of the current vectors is not zero), and the residual current is generated in the primary coil. Therefore, it will sense the secondary coil, when the current value to the residual current circuit breakers to limit the operating current value, the automatic switch trip, cut off the power.