In order to study the influences of the vacuum circuit breakers’ operation on the characteristics of high frequency transient overvoltage in the high-voltage side of generator terminal transformer in the offshore wind farm

a simplified experimental platform for the medium voltage cable electrical collector test system is established. The reignition model of vacuum circuit breaker

the high-frequency model of transformer and the frequency dependent model of metal Zinc Oxide arrester are established according to the experimental results. Based on the self-defined high-frequency model

the medium voltage collection system of offshore wind farm is set up using the PSCAD/EMTDC simulation software. The influences of normal switching-off and fault tripping of the circuit breakers on the amplitude and steepness of the transient overvoltage and the total number of reignitions are studied. An overvoltage protection device is proposed

which adds a choke coil in series and a small capacitor in parallel at the joint of the tower bottom vacuum circuit breaker and the 80 m cable. Simulative results show that the overvoltage and the total number of reignitions caused by the fault tripping of vacuum circuit breakers located at the bottom of a tower are the most serious

and the maximum overvoltage amplitude is 2.95 p.u.

the maximum steepness is 268.67 kV/μs and the total number of reignitions is up to 161. The amplitude and steepness of the transient overvoltage and the total number of reignitions are significantly suppressed with the installation of the overvoltage protection device.