基于大小量程的特高压换流站接地极不平衡保护方案研究

Research on unbalance protection scheme of ultra high voltage converter station earthed electrode system based on small and large range

针对目前特高压换流站接地极系统采用的电流横差保护存在着无法保护线路全长以及无法判别故障类型的缺陷,本文在分析了接地极不平衡保护动作原理的基础上,结合纵联差动保护全线速动的特性以及光纤通信容量大、传输距离远的优点,提出了一种基于光纤纵联差动的不平衡保护改进方案。改进的保护方案选用基于大小量程特性的差动继电器,大量程用于保护、小量程用于监视,提高了不平衡保护的灵敏性和可靠性,保证了直流系统的安全稳定运行。

Aiming to current transverse difference protection for grounding electrode system of ultra high voltage(UHV)converter station exists the shortage of cannot protect the whole range of the line and cannot identify the type of fault,this paper analyzes the operation principle of grounding pole unbalance protection,and provides an improved scheme of optical fiber longitudinal differential unbalance protection.Which combines the characteristics of full-line fast-moving of longitudinal differential protection and the advantages of large capacity and long transmission distance of optical fiber communication.The improved protection scheme uses differential relays based on large and small range characteristics,the large-scale is used for protection and small-range for monitoring.It improves the sensitivity and reliability of unbalance protection and ensures the safe and stable operation of the DC system.