Design Considerations for HVDC Ground Electrode System

摘要

The phenomenal growth of Indian Power transmission system, which includes both HVAC & HVDC system, has resulted in formation of one of the largest synchronous Grid in the world. Seven long distance bulk power HVDC transmission links of 22.5 GW capacity, four back-to-back interconnections between regions ofSGW capacity are in operation. A unique combination of +/-800 kV classical HVDC link and +/-320 kV VSC based HVDC link is under execution. India is also linked to neighboring country, Bangladesh, through 400 kVD/c link with HVDC back-to-back station (2x500 MW) in Bangladesh. The HVDC interconnection between New Madurai (India) and New Haberana (Sri Lanka) is under discussion.Many factors are involved in the design and operation of HVDC earthing systems, which determines the influence of the DC grounding current on the nearby andfar away environment. Either Dedicated Metallic Return (DMR) conductors or HVDC electrode are being commonly usedfor HVDC system. HVDC electrodes are in general less costly and have lower losses than DMR conductors. An appropriate grounding system is required to provide a safe and reliable operation of the HVDC system. Selection of site and design ofGround Electrode stations are very important for planning consideration for HVDC system's rating and its overload capability.In the paper, important design considerations including the safety & environmental impact / interference issues, material & layout of HVDC land electrode system have been discussed in brief.