1. Chapter :1:

ByYoshio Yoshioka, Kunio Hirasawa, Yukio Kurosawa, Masanori Tsukushi, Youichi Ohshita

This chapter provides the basic principles and theory of circuit-breaker techniques. Circuit breakers, which have the function of opening and closing a circuit, are indispensable for protecting other transmission devices in a power system. When a short-circuit fault occurs, they quickly eliminate the fault to secure system stability. Performance requirements for circuit breakers also include high-speed interruption, ensuring power system stability, high-speed closing, and suppression of switching surge, particularly for ultrahigh-voltage systems. In power circuit breakers, the intensity of the current that flows through the conductors and the voltage level that must be sustained by the insulating material are very high, and at present the only practical approach may be the use of arc plasma. Present commercial circuit breakers resort to plasma temperature control as the basis for their function. The chapter also provides basic information on characteristics of power circuit breaker arc space, arc extinction—the conversion from plasma to insulating space—and information on insulating space characteristics.

Chapter:2 : Analysis and Design

ByKoji Ibuki, Toshiaki Yoshizumi, Shuichi Sakuma, Takao Yamauchi
In normal operating conditions, a circuit breaker is in the closed position, and some current is usually flowing through the closed contacts. The circuit breaker opens its contacts when a tripping signal is sent to it. The puffer-type arrangement is most widely used in practical circuit breakers, and the gas usually flows in parallel to the arc axis in such an arrangement. The small diameter of the arc space and the relatively quiet transfer of energy along the radius justify application of the one-dimensional model for the calculation of energy balance in the high-current period. The physical arc model has always been used for improving understanding of the general characteristics of electric arcs. There are examples of successful application of the physical arc model to feasibility studies of circuit breakers in special circuitry. Evaluation of circuit-breaker performance is important for both completed circuit breakers and prototype circuit breakers.
Chapter 3:
Recent Developments in Circuit Breakers

ByHiroshi Kuwahara, Takao Yamauchi, Yoshio Yoshioka, Yukio Kurosawa, Kunio Hirasawa, Satoru Yanabu, Eiji Kaneko
Sulfur hexafluoride (SF6) circuit breakers, especially puffer-type breakers, are becoming the main equipment in switchgear for distribution voltage through the ultrahigh voltage class. A review of trends with some background history will be an aid toward a better understanding of the technology. Puffer-type SF6 gas circuit breakers are predominantly used in gas-insulated switchgear, and their interrupting capacity has recently been increased. SF6 circuit breakers have extended the field of application since that time supported by various improvements and developments. In most practical applications, SF6 circuit breakers are used, and SF6 gas is commonly used for interruption and insulation. The history of oil circuit breakers can be traced back to the experience of putting an air switch into mineral insulation oil in 1900 to cope with an increase in voltage and current. The interruption principle of air-blast circuit breakers can be classified into two major groups—the axial blast arrangement and the cross-blast arrangement.
Chapter 4: Tests and Diagnostics

ByEiichi Haginomori, Hisatoshi Ikeda, Susumu Nishiwaki

Developing a circuit breaker with the ability to cover a set of ratings entails an extremely large expense, and therefore standard circuit breakers covering standard ratings are selected and applied in most systems. Standard ratings generally cover the majority of system requirements, and thus, in the trade, standard rating values can generally be specified. Circuit breakers must safely break the rated short-circuit breaking currents under specified conditions. As both ac and dc components of breaking currents have time-varying characteristics, rated values are specified with respect to the instant of contact separation of the circuit breaker by both the International Electro technical Commission and American National Standard Institute. Operating sequences for short-circuit current-breaking tests take the easier test procedures into account and are therefore slightly different from the rated operating sequences. To prevent operating accidents and accelerate the application of remedies after an accident, the introduction of equipment-monitoring and diagnostic systems is becoming increasingly common.

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