SAFETY OF PARALLEL REDUNDANT SWITCHGEAR--A SYSTEM COMPARISON

To avoid hazards due to the failure of components in protective systems, identical systems arranged in parallel can be operated so that any inequality in system output signals will cause the overall system to be shut down on the fail-safe principle. This eliminates all hazards except in the case of the same class of failures of all systems during the interval between the detection of the failure and the resulting shutdown. The influence of this shutdown, delay, an important safety parameter, is investigated for the first time with the aid of Markoff chains. It is in this way possible to judge system variants from the aspects of safety and reliability.