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On June 12, 2026, Sieyuan Electric's HV AC Resonant Test System successfully applied in 500 kV submarine cable AC withstand voltage test for Hainan Cross-Sea Interconnection project. This project is one of China's largest extra-high-voltage, long-distance cross-sea transmission projects, and the test involved the largest test capacity of its kind in China. To Sieyuan's knowledge, this test represents the highest AC resonant test capacity applied in a grid engineering project worldwide as of June 2026
Technical Specifications and System Capabilities
Sieyuan Electric's HV AC Resonant Test System is engineered to solve the most critical challenges in extra-high-voltage cable testing:
Limited on-site power supply capacity
High losses and excessive temperature rise in test reactors
Insufficient reliability of variable-frequency power sources
The system currently provides AC withstand voltage testing capability for 500 kV cross-linked polyethylene (XLPE) cables up to 100 km in length — supporting safe, economical, and reliable high-voltage testing of long-distance submarine and land cables for power grid and offshore wind projects.
Industry Position and Global Presence
Sieyuan Electric is a leading manufacturer of HV AC Resonant Test Systems, with more than 2,000 systems delivered to customers worldwide. The product portfolio spans the full voltage range from 10 kV to 1,000 kV, serving power utilities, renewable energy projects, and industrial clients across numerous countries and regions.
Enabling the Offshore Energy Transition
As the global offshore wind industry moves toward deeper waters, higher voltages, and larger capacities, demand for high-power, high-reliability test equipment continues to grow. Sieyuan's HV AC Resonant Test System is built to meet these needs. In recent years, the system has successfully completed on-site handover testing of 500 kV, 90 km offshore wind power cables — establishing Sieyuan as a key technology partner for global marine energy development and cross-border grid infrastructure projects.
