To ensure the safety of the DC submarine cable with relatively low insulation level under multiple lightning strikes

a transition station model of the ±500 kV integrated offshore-onshore flexible DC transmission system for the Yangjiang Sanshan Island offshore wind power project is established in PSCAD/EMTDC. The overvoltage distributions of key equipment and submarine cables in the station are simulated

and the effects of multiple lightning current waveforms and the number of return strokes on equipment overvoltage in the station are analyzed. Furthermore

the suppression effects of installing reactors on lightning overvoltage are investigated

and the station’s withstand capabilities against multiple lightning strikes are compared under different arrester configuration schemes. The results indicate that higher lightning current amplitudes and shorter front time lead to higher overvoltages on equipment near the overhead transmission line

whereas longer tail time results in larger overvoltages at the submarine cable connection point. When the lightning current is limited to 30 kA

no additional protective measures are required. However

under 40 kA lightning strokes

the reverse-polarity overvoltage at the submarine cable terminal reaches 631 kV with an insufficient insulation margin. Installing a 4 mH reactor can suppress the cable terminal overvoltage to 384 kV

increasing the insulation margin to 33%. Additionally

adding arresters at both the station inlet and the overhead transmission line side of the reactor can further reduce equipment overvoltages and ensure that the electrical stress of all arresters remains within safe limits. These findings provide a coordinated transition station-transmission line lightning protection design methodology for large-scale offshore wind power projects using integrated offshore-onshore DC transmission.