基于自定义电流突变量的高压直流输电线路纵联保护原理

Fast Pilot Protection for HVDC Transmission Line Based on Custom Current Mutation

直流线路保护是直流输电技术发展的关键问题,其主要技术难点在于快速可靠地识别线路故障。电流差动保护受分布电容电流影响明显,需要延时、动作速度慢;而现有的其他纵联保护在对边界元件的依赖程度、过渡电阻耐受能力和抗干扰能力上仍有提高空间。针对上述问题,分析了高压直流输电线路电流突变量的故障暂态特征,并定义了一个新的电流突变量概念,利用自定义电流突变量的极性特征识别区内外故障;在此基础上,提出了一种基于自定义电流突变量的高压直流输电线路纵联保护方案。最后,通过PSCAD/EMTDC仿真模型对所提保护方案进行了仿真验证。仿真验证表明,所提保护无需延时即可正确识别区内外故障,还带有故障选极的效果,且不依赖于边界元件,过渡电阻耐受能力高、抗干扰能力强,具有较高的灵敏性和可靠性。

DC line protection is a key issue in the development of DC transmission line technology,and its main technical difficulty lies in quickly and reliably identifying line faults.Current differential protection is obviously affected by distributed capacitor current,which needs delay and slow action.However,other existing longitudinal protections still have room for improvement in dependence on boundary elements,fault resistance tolerance and anti-interference ability.In order to solve the above problems,the fault transient characteristics of current abrupt change of HVDC transmission lines is analyzed,and a new concept of current abrupt change is defined,which can effectively identify internal faults and external fault by using the polarity characteristics of custom current mutation.On this basis,a fast pilot protection method for HVDC transmission lines based on custom current mutation is proposed.Finally,the proposed protection method is verified by PSCAD/EMTDC simulation model.The proposed protection scheme has the advantages of no delay,fast action speed,no dependence on boundary elements,high tolerance of fault resistance and strong anti-interference ability,and has high sensitivity and reliability.