Safety model of safety-related fieldbus transmission systems

The paper deals with the use of modelling within development of safety Fieldbus transmission system. The basic principles and standards used in the process of safety evaluation in closed transmission systems are summarised in the paper. Dangerous states of the system are mainly caused by systematic failures within a specification of the system, electromagnetic disturbance and random failures of the HW effects. In the paper the effects of electromagnetic intreferences and random failures of HW can be described by the use of Markov´s chain.