City Research Online

Abstract

Protective relays serve to detect and respond to intolerable power system conditions at high speed and with minimum impact on utility loads. Abnormalities such as short circuits must be detected and removed from the power system rapidly, while tolerable abnormalities, such as switching surges, must not cause undesired circuit disconnection. With the rapid development of microprocessor technology and the consequent decline of costs, it is now able to use a high speed and possible application of specific microcomputer for a very complicate protection function. With this target in mind, a new adaptive algorithm based on finite-transform solution of the differential equation with adaptive variable window is proposed. An improved fault detection technique which is suitable for use under high resistance earth fault is also developed. Optimum performance of both operating time and reach accuracy has been obtained. The algorithm, using fast processing techniques, involves reasonable on-line calculation so that a very high sampling frequency can be employed. This thesis will discuss the ideal operating region of distance relay under different conditions. Its relationship with the system configuration and condition is thoroughly reviewed. A method is then developed to deduce the ideal operating region of distance relays under different load conditions in the line without the need for real time computation and thus can overcome the restrictions caused by the need of communication channels. The effect caused by changes in power system configurations will also be discussed. Finally this thesis propose a method to incorporate artificial intelligence technique into the digital distance relay. The relationship between the loading conditions of the line and the corresponding ideal operating region is used to train the digital distance relay by applying the neural network technique and discriminate internal and external faults under different load conditions. The end result is an intelligent digital distance relay which can identify even high resistance earth faults within its designated operating region. This relay is fully adaptive to changes in the power system and its performance will not be degraded within a wide operating range.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Engineering > Electrical & Electronic Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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