In the dynamic world of energy transmission, the quest for efficient and reliable power delivery has led researchers to explore innovative solutions. A groundbreaking study led by Weixuan He from the School of Mechanical Electronic and Information Engineering at China University of Mining and Technology (Beijing) has introduced a novel pilot protection scheme for submarine cables in flexible low-frequency transmission systems. This research, published in ‘Zhongguo dianli’ (China Electric Power), addresses a critical challenge in modern power systems: the accurate detection of faults in submarine cables.
Traditional current differential protection methods, which rely on the characteristics of synchronous power supplies, often fall short when applied to flexible low-frequency transmission systems. These systems, which are increasingly used in offshore wind power transmission, employ power electronic converters on both ends of the AC submarine line. The fault current characteristics in these systems are governed by the converter control strategy, leading to a higher risk of incorrect operation by traditional protection schemes.
He’s research delves into the operational performance of traditional current differential protection, identifying the root causes of its declining effectiveness in these advanced systems. “The fault current characteristics in flexible low-frequency transmission systems are fundamentally different from those in traditional systems,” He explains. “This difference necessitates a new approach to fault detection and protection.”
The proposed pilot protection scheme leverages the cross entropy algorithm, a statistical method used to measure the difference between two probability distributions. By sampling the current on one side of the submarine cable and applying virtual negative capacitance compensation and negative number processing, the scheme calculates the cross entropy between the sampled current and the current on the other side. This innovative approach allows for the accurate differentiation between external and internal faults, ensuring reliable protection.
The hardware in-loop test results are promising. The scheme demonstrated correct operation under various fault conditions, including high transition resistance and measurement errors in current transformers (TA). This robustness is a significant advancement, as it ensures the reliability of power transmission even in challenging conditions.
The commercial implications of this research are vast. As the energy sector continues to embrace offshore wind power and other renewable sources, the need for reliable and efficient power transmission becomes paramount. He’s pilot protection scheme offers a solution that can enhance the stability and reliability of flexible low-frequency transmission systems, reducing the risk of power outages and ensuring continuous energy supply.
This research not only addresses immediate challenges but also paves the way for future developments in the field. As Weixuan He notes, “The cross entropy algorithm provides a flexible and adaptable framework that can be further refined and applied to other areas of power system protection.” This adaptability could lead to more sophisticated protection schemes, enhancing the overall resilience of the energy grid.
The study, published in ‘Zhongguo dianli’ (China Electric Power), represents a significant step forward in the evolution of power transmission technology. As the energy sector continues to evolve, innovations like He’s pilot protection scheme will play a crucial role in shaping a more reliable and efficient future.
