Beijing, China, October 20th, 2016 – A group of 20 leading HVDC experts gathered in GEIRI’s Power System Power Electronics Laboratory on August 20th to witness the type test of the 200kV DC circuit breaker designed for Zhoushan multi-terminal system. With a boom from the heavy current interruption test, the DC breaker successfully interrupted a short circuit current up to 15.6KA, which has set a new world record in terms of the breaking capability.
The fact that VSC-HVDC systems cannot realise rapid clearance of the DC faults has hampered the development of VSC-based overhead line transmission system, multi-terminal HVDC system and DC grid. That’s why GEIRI has devoted itself to the development of DC breaker over the past 4 years.
With years of intensive research on both topology and equipment, a 200kV prototype came out in early 2015. An advanced concept was adopted by combining mechanical switching based on ultrahigh-speed disconnect switch and power electronics switching based on high-power IGBT full-bridge cascade assembly, which not only avoids the high losses associated with a solid-sate breaker, but also overcomes the limit of switching speed of a mechanical breaker. As the first of its kind in the world, this 200kV DC circuit breaker can interrupt 15kA fault current within 3 milliseconds, 100 times faster than the blink of a human eye.
In terms of testing methodology, GEIRI has deeply studied the equivalent test mechanism and proposed detailed methods for heavy-current operation test, high-voltage withstand test, short-circuit interruption test and closing test. In terms of testing capacity, a set of full working condition testing facilities was built, which allows assessment of the overall performance of dc breaker in real operation.After the type test, the DC breaker will be delivered to project site one week later, which has brought the project one step closer to the target commissioning date at the end of the year.