Digital signal processing (DSP) and protection

Abstract

The development of digital computers in the 1960s led to investigations to establish the possibility of using them to implement some or all of the protection functions in a power system. In essence, developments in technology have gradually permitted the migration of the well established fundamental protection algorithms described in previous chapters to new hardware and software environments. The volume and speed of processing that can be implemented in modern hardware is increasing all the time. While the fundamental principles remain the same, as already mentioned, new ways of extracting relaying information from transducer signals are now possible. The first comprehensive survey of the application of computers to protection was published in 1969 [1]. Within three years, the application of these principles to distance protection was described in two publications [2, 3]. The first developments of digital relaying algorithms and therefore the beginning of numerical relays were described in [4, 5]. As regards hardware, developments were very rapid with basic discrete digital circuits being replaced by general purpose microprocessors and in the early 1990s by special Digital Signal Processors (DSPs). Further information to trace the development of microprocessor based protection may be found in [6, 7]. These developments continue to keep pace with very rapid technological change. The purpose of this chapter is to present the fundamentals of microprocessor based environments which involve a tight connection between hardware and software.