TABLE OF CONTENTS Complex and dispersed power systems necessitate large manpower resources for control, maintenance and management functions. Such resources may be reduced or employed more efficiently with the help of computer systems. This chapter describes the basic interfaces, software and hardware necessary for transmission and distribution power system supervisory control and data acquisition (SCADA). Programmable logic controllers (PLCs) and substation bay controllers may be used for local automatic control functions. These controllers are described together with a practical interlocking application example. This chapter also introduces traditional power line carrier communication and signalling methods. Communication via fibre optic links is mentioned separately in Chapter 12. This chapter goes on to describe a centralized power transmission network control system and covers the very important subject of software management. Such management is essential if software development is to be achieved within quality, time and budget constraints.
Programmable logic controllers (PLCs) were initially developed for discrete control applications in machine and materials handling production engineering environments. The on-going development of PLCs for the control and monitoring of industrial systems has increased their capabilities from simple hard wired logic elements (NAND, NOR gates) to advanced functions using software-controlled microprocessors for piping and instrumentation diagram (P&ID) algorithms, floating point arithmetic, network communication and multiple processor configurations for parallel processing. Modern PLCs are capable of handling power system local control automation requirements. IEC 61131 is rapidly becoming the internationally recognized standard for configuring PLCs. PLCs evolved to become bay...
