Field Cases Analysis of Protection Schemes Applied To Transmission Lines Connecting Inverter-Based Resources To The Grid
The increasing penetration of renewable energy sources, such as wind farms and photovoltaic (PV) solar plants, introduces new challenges to the protection of transmission lines connecting these resources to the bulk power system. These challenges arise due to the distinct fault contribution characteristics of renewable sources compared to traditional synchronous generators, leading to issues with speed, security, and reliability.
Due to the unconventional nature of renewable sources, the safety of phasor-based protection applications relies on security-based setting strategies, which often result in lower sensitivity and slower response times. On the other hand, time-domain-based protection, which includes traveling waves and incremental quantities, operates based on the variations in currents and voltages generated by faults, making it more immune to the type of source present in the system.
EDF Renewables Brazil has built and operates several wind farms and PV plants in Brazil. Drawing from field experience, EDF Renewables Brazil has standardized a protection system that combines both phasor-based and transient-based protection for the transmission lines connecting their renewable plants to the grid. This innovative approach offers significant advantages in terms of speed, security, and reliability. Additionally, the traveling waves generated by faults are used for fault location with an accuracy of one tower span.
This paper presents and discusses the protection scheme that EDF Renewables Brazil defined as standard for their extra-high voltage transmission lines. The paper includes the analysis of field events involving the standardized protection system, which has been in operation for over two years on EDF’s 500 kV transmission lines. The performance of the applied protection functions is evaluated for real faults, including both external and internal faults on the protected transmission lines. The benefits of the combined protection system are demonstrated through the analysis of field event reports.
The results of the field event analysis indicate that the adoption of time-domain-based protection functions significantly enhances the safety and reliability of power system operations, especially in scenarios with high penetration of renewable sources. The implementation of these technologies represents an important step towards the modernization of transmission networks and the efficient integration of renewable energy sources.