Study of EMI (Electromagnetic Interference) Endurance of Two Polling-Type Local Area Networks Used in Real-Time Automation Applications in a Simulated Electrical Environment

摘要

Three modelling ideas: disturbance generator, applying risk, and availability area to be used in the planning, testing and use of real-time automation applications installed in EMI-environments (electromagnetic interference), for the evaluation of EMI-endurance of a local area network (LAN) used on the process data bus level are presented. The effect of electrical disturbances is taken into consideration by the disturbance generator. It takes into consideration parameters affecting the EMI-endurance of a LAN: the physical installation, and parameters of the data communications, and of the electrical transient disturbances. Generation of messages, disturbances, and the network were simulated and tested. The time stationary probability distributions of the performance and unreliability are evaluated as a function of the disturbance voltage. By using the time stationary probability distributions of EMI-levels measured from field conditions, and the probability distributions, the risks and availability areas of a LAN-based system can be evaluated in different EMI-conditions.