Distributed Control ... Relevance & Ramification for Utility and Process Applications

Abstract

Distributed digital control systems have appeared structurally desirable for many years. The concepts of hierarchial control and distributed risk were advanced as necessary structural considerations in the control of large scale systems almost coincidentally with the advent of modern electronic instrumentation and digital process control computers. The logarithmic growth patterns of semiconductor technology over the last two decades and the availability of microprocessors and other manifestations of large scale integrated circuitry have finally converted the distributed digital control system from a structurally desirable nicety to an economic inevitability. This paper examines the relevance of distributed digital control systems in the rigorous industrial environment of energy, utility, and process control applications. Design considerations leading to minimization of total installed system costs while retaining the necessary system flexibility to allow user reconfiguration to meet changing process or product needs are delineated. The twin problems of reliability and maintainability are examined in the context of allowable structural degradation concepts which must be inherent in the design of any distributed system.