Power technology giant ABB has announced a breakthrough innovation that will allow the development of high-voltage direct-current (HVDC) networks. Its new circuit breaker is said to be an important step towards achieving marine DC transmission networks for offshore wind stations and long-distance transmission to shore.
DC cables have lower transmission losses and can carry larger volumes of electricity than the standard alternating current (AC) cables. When the HVDC breaker technology is ready for commercial use, it should become possible to combine these advantages with the greater transmission security of cable networks. If one line suffers an outage, another can take over all or part of the transmission.
ABB says it is already working on the construction of multi-terminal systems and calls the DC breaker innovation "a major step in the evolution of HVDC grids". The company has also set up an HVDC grid simulation center developing solutions for future DC "overlay" grid operations.
Until now, only HVDC point-to-point connections have been possible - that is single DC lines that transmit electricity from one place where the power is generated to a distant point where it is consumed. The challenge has been to design a DC breaker capable of operating without high losses to allow the move to flexible DC networks.
ABB says its hybrid mechanical and power electronics breaker fits the bill, and compares its capability with stopping dead a heavy truck travelling at top speed on the motorway within 5 milliseconds, or 20-30 times faster then the blink of an eye.
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