Operational insights from the ±320 kV VSC HVDC Cable System: Metallic Pipeline crossing challenges and Thermal Performance Assessment

Pugalur and Thrissur and is designed to carry a rated power of 1000 MW per pole at a rated voltage of ±320 kV DC.

There is a metallic pipeline carrying petroleum products crossing the HVDC cable system at five locations along the cable route. The metallic pipeline is cathodically protected against corrosion, along with a monitoring system for critical corrosion parameters, such as the pipeline-to-soil potential (PSP). Pipe line to soil potential is the electrical potential difference between a buried metallic pipe line and the surrounding soil, used to assess corrosion risk and the effectiveness of cathodic protection. The paper outlines the construction methodology adopted at the utility crossings to meet the safety and maintenance requirements of both the

HVDC cable and the petroleum products pipeline. It also presents pre-charging measurements from the existing corrosion monitoring system, along with the factors to be considered when designing corrosion-mitigation measures specific to the HVDC cable crossing. The paper also describes post-charging measurements of the pipeline's corrosion monitoring parameters.

During transient conditions, i.e., when a fault occurs in the HVDC line or cable, stray currents follow the path of the metallic pipeline to ground through holes in the coating system and exit through another point where the corrosion protection is compromised. Furthermore, the ground potential rise during fault conditions also disrupts the corrosion protection system. Simulation results are analysed for various fault conditions to determine the worst-case discharge currents and ground potential rise. The paper also analyses actual faults that occurred on the HVDC line and checks for variations in PSP recorded by the corrosion monitoring system. Finally, the paper compares the VSC and LCC in the context of interference in a metallic pipeline.