Fundamentals of High Voltage Circuit Breakers, Switching Stresses and Failure Modes

HV circuit breakers

The thesis contributions can be mainly divided into three phases: high voltage circuit breakers failure modes and effects analysis, probabilistic models and maintenance optimization. The extra phase is the investigation of stresses of HV circuit breakers from the simulation and the statistical method.

The organization of this thesis can be described as followed:

Fundamentals of HV circuit-breakers composed of functions and components of HV circuit-breakers, types of HV circuit-breakers and switching transients are represented in Chapter 2.

Chapter 3 represents the switching stresses of HV circuit-breakers. In this chapter, the stresses of HV circuit-breakers regarding different types of applications are investigated by simulation method. The other stresses regarding the number of faults and their severity are investigated by using statistical method.

The fundamentals of probability and reliability are first introduced in chapter 5. Then developed models, a treeing model and a cascading reliability model are introduced. With these models, the reliability and probability of HV circuit-breakers subject to failures can be determined.

The application of Markov process used to investigate steady-state probabilities is introduced in chapter 6. The parallel Markov model for HV circuit-breakers is developed to examine the state probabilities. Different types of HV circuit-breakers with different driving mechanisms are taken into consideration.

Chapter 7 is the last part of this thesis representing cost structure analysis and maintenance optimization. A decision matrix approach is implemented in order to figure out the importance of parameters relating to costs of HV circuit-breakers. Apart from cost structure analysis method, maintenance optimization by using different methods is introduced in this chapter.

Finally, the conclusion is made in chapter 8 to summarize the results of this thesis and to propose the direction of the future development.

Research Objectives

The maintenance programs of HV circuit-breakers have been long performed by using the manufacture guidelines and experiences of operators. They have hardly been proved that they are really effective in terms of performance and costs. With emerge of deregulation electricity markets, maintenance costs considered as the large part of operation costs of utilities should be reduced in order to keep competitiveness of utilities.

The objectives of this work are mainly comprised of those mentioned aspects. The failure database collected from utilities is deeply investigated to establish the probabilistic models.

These models can represent the probability of failures and how the failures are developed during the lifetime of HV circuit-breakers.