Netherlands — With the continuous increases in the size of wind farms and the capacity of wind turbines, the operating voltage of wind farm power systems is also being increased to keep power transmission losses as low as possible.

KEMA Labs (the CESI Testing, Inspection and Certification Division) demonstrated the testing of two types of new switchgear for offshore: HVDC circuit breakers and HVDC gas-insulated switchgear (GIS). The demonstrations were conducted within the framework of the European PROMOTioN project on offshore transmission grids, which was completed in 2020. The challenge for KEMA Labs was to validate components of future HVDC grids.

Three HVDC circuit breaker technologies, rated 80 to 350 kV, were tested in the high-power laboratory, while one long-duration high-voltage withstand test of an HVDC GIS (320 kV) was performed in a high-voltage laboratory. The results of the system studies have provided an improved understanding of the impact of transients on switchgear within a faulted grid.

The three different technologies of circuit breakers were supplied by industrial partners Mitsubishi Electric (Japan), who provided an active current injection HVDC circuit breaker based on high-voltage vacuum circuit breakers, Hitachi ABB Power Grids (Sweden, Switzerland) who provided a hybrid HVDC circuit breaker based on semiconductors as well as a HVDC GIS, and SciBreak (Sweden) who contributed a new type of converter-assisted vacuum arc-based dc circuit breaker.

By operating AC short-circuit generators in low frequency, for the first time ever, it was possible for the tests to cover the complete interrupting cycle of a fault current up to 20 kA in a meshed HVDC grid. For the largest circuit breakers, six short-circuit generators were needed. Unlike earlier tests, this time all breaking functionalities could now be tested in a single "shot" as in service.

The test results should help make the ever-expanding wind energy systems become more efficient and reliable for the final consumer.

Source: CESI