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Siemens has developed the world's first circuit breaker capable of operating at 1.2 million volts. Ultra-high voltages increase the capacity of power cables, thereby making it possible to transport large amounts of electricity with a relatively small number of overhead lines. Circuit breakers are used in transformer substations to connect or disconnect individual power lines. The new circuit breaker is destined for a test installation in Bina, India. The Indian government is turning to UHV technology in order to supply its metropolitan areas with electricity generated in the country's mountainous regions. The 1.2-megavolt test transmission line is capable of carrying 8,000 megawatts of power. It therefore has more than twice the capacity of the 800-kilovolt lines currently in use.
Alternating voltages of over one million volts and direct voltages of over 800 kilovolts are both classified as ultra-high voltages. In either case, the ultra-high voltage technology offers decisive advantages when transmitting power over long distances. Transmission at such high voltages reduces power losses and is therefore more efficient. The major challenge in UHV power engineering is to provide sufficient insulation to prevent voltage flashovers.
The new circuit breaker from Siemens Energy has been designed for a 1.2-megavolt AC transmission line. The active component is half a meter in diameter and is installed in a sealed cylindrical metal housing. The gap between the circuit breaker and the earthed metal housing is a mere 45 centimeters. Given an extremely high potential gradient of 1.2 megavolts, the danger of the power arcing over this very short distance is high. To prevent this, the permanently sealed metal housing is filled with an insulating gas. The shape of the components is also crucial, since any corners and edges would lead to high field strengths, thus increasing the likelihood of flashovers. The new circuit breaker is based on proven components for an 800-kilovolt model. The shape of these components was conceived on the basis of calculations designed to optimize their dielectric strength.
Built at the Siemens plant in Aurangabad, India, the new circuit breaker is now undergoing tests with the network operator Power Grid Corporation of India Limited. At the conclusion of several years of trials, India is planning a nationwide expansion of its power grid based on UHV technology.
Reference Number: IN 2012.02.1e