Opertional and Commissioning Challenges and mitigation measures while integrating new HVDC Bipole with existing +/- 800kV HVDC Bipole with DMR system

Integration challenges require a highly coordinated approach encompassing precise protection settings, clearly defined operational sequences, and robust inter-bipole communication protocols.

Such coordination is vital to maintaining system reliability and safety across all modes of operation, including normal, monopolar, and faulted conditions. Neutral surge arresters are critical components for protecting neutral equipment from transient over voltages caused by switching surges, line faults, or pole restarts. This paper outlines key design considerations for neutral surge arresters in the context of integrating a new HVDC bipole with an existing HVDC DMR bipole. It also addresses operational challenges encountered during commissioning, particularly when employing the split

DMR method to minimize outages on the existing bipole.

Neutral Busbar Grounding Switches (NBGS) play a pivotal role in controlling the return current path, especially during monopolar or earth return operations. Their coordination with the DMR conductor is essential to ensure safe and reliable diversion of return currents under all operating conditions. Furthermore, the design and interconnection of a common earthing system between the existing and new bipoles must be meticulously engineered to prevent circulating currents. This paper discusses various protection strategies involving NBGS during the integration of a new HVDC bipole, emphasizing practical challenges and solutions. Commutation failures occurring when inverter valves fail to transfer current properly between valve groups due to insufficient AC voltage,

AC system disturbances, or abnormal DC current conditions is another critical issue in parallel inverter operation. Effective coordination of commutation failure protection settings between parallel inverters involves carefully tuned sensitivity levels and graded time delays to ensure selective tripping and system stability. This paper explores the technical challenges and practical solutions related to commutation failure coordination encountered during the integration of a new

HVDC bipole with an existing ±800 kV DMR-based HVDC system.

In this paper we discussed the operational and commissioning challenges of integration of new

±800kV ,3000MW HVDC Bipole of Champa Kurukshetra Link – 2 with existing ±800kV, 3000MW HVDC Bipole Champa Kurukshetra Link – 1 combined to enhance the capacity to 6000MW.The paper also highlights the minimum control and protection signal inputs required during the integration process, along with the physical arrangement and coordination of DC yards necessary to ensure reliable and secure system operation.