Protection against lightning surges of electrical and industrial installations

Lightning strokes generate high interference voltages in industrial installations and high-voltage substations. The characteristics of the transients, the amplitudes of the voltages and their number vary considerably from one network to another. A sound understanding of the phenomena involved and of the implications of certain industry practices are necessary to ensure the safe and reliable operation of the installed electrotechnical equipment. In this paper a look is taken especially at effects of lightning strokes on power distribution system, design of distribution class surge arresters for lightning protection and main design criteria for insulation coordination from the viewpoint of lightning protection

Common criteria for right selection of the medium voltage circuit breakers

In the mid 1960s, two new breaker technologies, one using SF6 gas and the other Vacuum as its arc quenching medium, were introduced to the switchgear market. Experience in developing SF6 and Vacuum circuits-breakers was supported by increasingly close cooperation between the research centers. Today it can be said that they all replaced the older types of circuit breakers (Bulk - oil, minimum - oil and pneumatic technologies). However, there is not always agreement on which criteria should be used when choosing one of these two dominant technologies. Therefore, both circuit breaker technologies have been discussed taking into consideration those points of Arc-interrupting characteristics, basic construction of the switching devices ( magnetic actuator, rapid switching, synchronous circuit-breaker, integration with sensors and electronics), technical performance (electrical and mechanical endurance, reliability of dielectric media, switching overvoltages, environmental impact), specific switching applications (overhead lines and underground cables, transformers, motors, capacitor banks, arc furnaces, shunt reactors)