Real-Time Simulation Environment for High-Impedance Faults: Application in OPAL-RT

High-impedance faults (HIFs) in medium-voltage distribution networks represent an ongoing challenge for protection systems, accounting for 5% to 10% of ground faults and posing risks to both electrical infrastructure integrity and public safety. Despite more than four decades of research, HIF detection remains problematic, particularly in modern networks integrating inverter-based resources (IBR), where fault current variability can be mistaken for normal fluctuations or other system events. Conventional overcurrent relays have demonstrated less than 20% effectiveness in detecting these faults. This paper addresses the modelling of HIFs in real-time simulators, explicitly using the OPAL-RT platform, and proposes an optimised model that incorporates the random nature of resistances and DC sources associated with HIFs. A comparative analysis between real-time simulation and offline simulation in Simulink is presented, demonstrating the consistency and accuracy of the implemented model. The results confirm that the optimised model not only accurately replicates theoretical behaviours but also meets real-time execution requirements, thereby contributing to the improvement of protection schemes and fault detection studies in modern distribution systems.