design of a residual current circuit breaker ic with anti-interference technique

        The causes of residual current protection principle for three phase four wire wire together through the zero sequence current transformer CT, can also be installed on the neutral line N a zero sequence current transformer CT, the use of these CT to detect three-phase current vector, and the residual current, as shown IN figure 1, according to the principle of the circuit, the leakage happens when circuit equipment or ground fault and three-phase load balance IN full, one side of instantaneous current vector and zero, namely the Ia + Ib + Ic + IN = 0, IN current transformer magnetic flux vector and is equal to zero, at this point, the induced current IN the secondary coil IL = 0.When the protected circuit is IN insulation failure, load side have to drain the load current, the zero vector and zero sequence current transformer, which Ia + Ib + Ic + indicates IN 0, IN current transformer magnetic flux vector and also is not equal to zero, at this point, the zero sequence current transformer secondary winding occurs IN the induced current, namely the residual current IL indicates zero.