Common Mode Interference Analysis of Supervisory Control System with the Plugin Unit Structure

This paper discussed some protecting problems of commom mode interference existed in the supervisory control systems with the plugin unit structure, which is widely used. This paper analyzed the fact in detail that the voltage of the common mode interference conducted to the box along with the signal line and coupled in the adjacent plugboard. This paper also developed coupling equivalent circuits between plugboards for the simplified modes. Then some effective methods of interference protection were proposed, and the advantages and the disadvantages of the following two cases, a steel plate is installed between the plugboards and no steel plate is used, were discussed.