Improved OLT Protection Strategy for Embedded HVDC System

The application of embedded high voltage direct current (HVDC) technology provides innovative ideas for improving the power transmission capacity in limited transmission corridors and enhancing the flexibility and controllability of power grids. It adopts a special symmetrical monopole topology structure, which makes the conventional protection principles no longer fully applicable. This paper analyses the adaptability of traditional open line test (OLT) protection principles in embedded HVDC systems and finds that there are performance deficiencies such as refusal-action of protection and long action time. Based on fault characteristics, an improved overcurrent criterion and a new voltage imbalance criterion of OLT protection are proposed, and a new OLT protection strategy is formed to deal with DC grounding faults. The simulation results show that the proposed protection strategy can correctly act on DC grounding faults on each pole and greatly shorten the protection action time, comprehensively improving the reliability and speed of OLT protection, and effectively ensuring the safety of embedded HVDC systems.