Recent Developments in Circuit Breakers

Recent Developments in Circuit Breakers:

DC Circuit Breaker : Light duty DC Circuit Breaker have been in use since long. However, with the latest developments in HVDC transmission there would naturally be the necessity of the HVDC circuit breaker. The two major problems of HVDC circuit breaking are: The amount of energy to be dissipated during the short interval of breaking is very high as compared to the conventional a.c. circuit breakers. The natural zero current does not occur as in the case of a.c. circuit breakers. Resistance switching and efficient cooling by forcing the liquid or air blast are used to dissipate the high amount of energy, whereas artificial …


Recent Developments in Circuit Breaker Tester : Generating capacity the world over has been increasing at phenomenal rates. Compared to the increase in generated power the breaking capacities of Circuit Breaker Tester show an even faster rise. Figure (16.1) shows, for instance, the increase in breaking capacities of circuit breakers, which indicates a growth rate of 10% per annum. This development is essentially determined by two factors first, the growth in generating capacity and, secondly, the increasing trend towards interconnection of systems. The high energy density in the large cities today also forces the power supply undertakings to supply HV direct into the …


SF6 Circuit Breaker : One of the recent developments in the field of high voltage switchgear is the SF6 circuit breaker. In this a gas called sulphur hexafluoride is used as the medium of insulation and arc interruption. Basic Features of SF6 Breaker: SF6 is about 5 times heavier than air. It is chemically very stable, odour­less, inert, noninflammable and nontoxic. The gas has a high dielectric strength and outstanding arc-quenching characteristics. In SF6 the arc voltage remains low until immediately before current zero so that the arc energy does not attain a high value. Moreover the arc time constant for SF6 is also very …


Vacuum Circuit Breaker : Although the advantages of interrupting the arc in a vacuum were recognized as early as the nineteenth century, this did not find wide application till a few years ago. This was because the knowledge of problems in material science, vacuum technology and plasma physics was not sufficiently advanced to provide solution to the many technological problems encountered in the design and construction of a reliable Vacuum Circuit Breaker. High vacuum has two outstanding properties: (1) the highest insulating strength known, and (2) when an a, c. circuit is opened by the separation of contacts in a vacuum, interruption occurs …