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Over the last 50 years, high-voltage circuit breakers have become more reliable, more efficient, and more compact because the interrupting capability per break has been increased dramatically. These developments have not only produced major savings, but they have also had a massive impact on the layout of substations with respect to space requirements. New types of SF6 interrupting chambers, which implement innovative interrupting principles, have been developed during the last three decades with the objective of reducing the operating energy of the circuit breaker. This has led to reduced stress and wear of the mechanical components and consequently to an increased reliability of circuit breakers. Service experience shows that the expectations of the designers, with respect to reliability and day-to-day operation, have been fulfilled.

An extensive revision of the IEEE C37.011 "Application Guide for TRV for AC High-Voltage circuit Breakers" has been in process for the last four years. The main aim was to introduce the two- and the four- parameter description of the transient recovery voltage (TRV) as used in IEC Switchgear standards that have been introduced in the revisions of Standards C37.04 and C37.06. These two standards are being concurrently revised, but IEEE C37.011 provides the necessary explanations on TRV characteristic in advance. Non-specialist engineer users of the guide will better understand these standards

New types of SF/sub 6/ interrupting chambers, which implement innovative interrupting principles, have been developed during the past years, based on the objectives of reducing the operating energy of the circuit breakers and consequently increasing their reliability. This paper describes the rear-exhaust-type "self blast" double-volume thermal chamber, which was designed with the help of new chamber development software programs, of the physical imaging model of the arc. Simulations and confirmation by laboratories tests the interruption of short-circuit currents and, especially, the testing of short-circuit currents that have a nonpassage by zero on such a new chamber for applications to generator circuit breakers are shown and evaluated.

A hybrid circuit breaker consists of a series-connected vacuum- and SF6 interrupter. The vacuum interrupter has the function to withstand very steep-rising transient recovery voltages, whereas the SF6 interrupter is stressed with the peak of it. Full scale tests are described of a 145-kV prototype, which is subjected to short-line faults based on 63 kA. During these tests, current through the breaker and voltages across both interrupters were monitored with a high-resolution measurement system. It is shown that the principal idea works correctly. From measured results, it is demonstrated that the interaction between the two arcs of completely different physical nature has a positive effect on the interruption: Immediately before current zero, the SF6 arc assists the vacuum arc to interrupt, whereas after current zero, the vacuum arc assists the SF6 arc in the recovery against the recovery voltage. From the analysis of the measurements, it becomes clear that high values of post arc current (up to 30 A) have (at least initially) a positive effect on the breaker performance. Detailed modeling of the interaction of arc-arc and arc-circuit is described, showing a good agreement with the measured results. The model is used to predict the voltage distribution across both interrupters when other (capacitive) voltage grading is applied in the design than present during the tests.

This paper describes the efforts by the IEC and the IEEE Switchgear Committee to harmonize the transient recovery voltage (TRV) of circuit breakers from 1 kV to less than 100 kV. Progresses are advancing fairly fast due to previous studies performed by CIGRE on these TRV and a new goodwill toward harmonization demonstrated by all the people involved around the world.

The self-blast technique of interruption for SF/sub 6/ High-Voltage circuit breakers has been developed and improved during the last fifteen years. This technique has proved to be very effective and has been widely applied to High-Voltage circuit breakers up to 800 kV. The paper shows the application of this technique to the development of SF/sub 6/ Generator circuit breakers with low energy spring-operated mechanisms. A particular characteristic of Generator circuit breakers is their necessary capability to interrupt short-circuit currents with delayed current zeros. As shown in this paper, this performance, required by ANSI/IEEE Standard C37.013, can be demonstrated by breaking tests and calculations. The IEEE Switchgear Committee is currently revising the standard for Generator circuit breakers in order to extend the scope to applications of less than 100 MVA rated power. The paper presents calculations that have been made to calculate TRVs (Transient Recovery Voltages) for system fed faults in the case of small Generator circuit breakers connected to the step-up transformer by cables.

We have transmitted 1.5 Tbit/s over a deployed line of 4000 km of NZDSF using only C-band EDFAs with 25 GHz spacing and NRZ modulation format. The average performance obtained correspond to a 4.8 dB margin for a system designed with Enhanced 7% redundancy FEC scheme based on concatenated Reed-Solomon code. This experiment demonstrates for the first time the industrial feasibility of a 1.5 Tbit/s regional network transmission which is compatible with 0.4 (bit/s)/Hz. The use of NRZ format has two advantages. The first one is a low cost and compact terminal equipment due to less modulation stages compared to RZ or CRZ. The second one is a better compatibility with high channel density allowing simpler and lower cost repeaters for a given capacity. Furthermore, the demonstration of the excellent robustness of NRZ format over NZDSF allow direct field deployment or upgrades.

For a long time, SF/sub 6/ puffer circuit-breakers have been considered the most efficient and reliable type of interrupting switchgear. This technique was introduced by GEC ALSTHOM T&D (then DELLE ALSTHOM) at the end of the 1950s for medium voltage applications, and then extended in the 1960s to high-voltage circuit breakers. Since then, and until the end of the 1980s, it has been the dominant technique in the high voltage range. In the 1980s, GEC ALSTHOM T&D began to study a new generation of SF/sub 6/ circuit breakers which can be operated by low-energy mechanisms and which were characterized by the use of arc energy for interruption. Here, the author examines the development of tools used in the design of circuit breakers, and describe the recent evolution of high-voltage circuit breakers.

Recent years have seen an increasing development of small generations of electric power. These generators of relatively low power, equal to or less than 100 MVA, are protected in an economic way by generator circuit breakers that are located between the generator and the step-up transformer. In 1997 the IEEE Switchgear Committee has issued a new edition of its standard C37-013 for generator circuit breakers, which covers mainly the applications with power transformers rated 100 MVA and above [1]. A revision of this standard is currently prepared by the IEEE Switchgear Committee in order to broaden its scope to all generator circuit breakers. The purpose of this paper is to contribute to the definition of TRV requirements for system-source faults in the case of small generator circuit breakers connected to the step-up transformer by cables.