Chapter 17 - Pattern-recognition methods for decision-making in protection of transmission lines

Abstract

Pattern-recognition methods will enable detection, prediction, classification of fault, and decision-making, which are important functioning integrated into the implementation of the protection schemes to develop a smarter transmission system. Electromechanical, electronic, digital, numerical, and today smart relays represent a trend in the field of power system protection and in a special case, protection schemes of transmission lines. In the procedure of pattern recognition, interesting features or useful information can be extracted from power system signals. The discovered features, as an input feature vector, can be applied to decision-making or process of supervision in the protection schemes. The decision-making model contains a representation of the nonlinearity of the mapping between the input vector and output target. Therefore the pattern-recognition method is considered as one of the most important frontiers in complex and nonlinear problems, say power system protections. The proposed chapter will provide a framework for different functions of future technology of smart distance relays. Fault detection, fault classification or phase selection, high-impedance fault detection, symmetrical fault detection during power swing, and power swing detection are the functions developed through pattern-recognition methods. Since the performance of some schemes of the conventional distance relays has some shortcomings, the pattern-recognition methods have the potential to improve the performance of the schemes. They can execute their functionality with cooperation with other routines of the conventional relays. Moreover, the pattern-recognition methods need not exact information on the parameters of power systems to make the final decision, while these methods can work under missing data or noisy conditions. They can also have the capability to adopt against changing the power system topology such as compensated or double-circuit transmission lines. In addition to overcoming some shortcomings of conventional schemes, researchers are interested to propose approaches toward more simplified but more reliable protection schemes. All protection schemes will be examined and evaluated by feasibility, security, dependability, reliability, and speed criteria. To improve the criteria, protection schemes can be addressed by some new approaches such as pattern recognition. This chapter discusses the details of protection schemes based on pattern recognition and also suggests a new trend of setting-less smart protection schemes. Extensions of this idea and giving a new perspective to apply pattern recognition to a future generation of protection relays are the purpose of this chapter.