基于近似熵变化量判据的混合直流输电系统纵联保护方案

A pilot protection scheme for a hybrid HVDC transmission system based on an approximate entropy change criterion

高压直流输电线路行波保护对信号采样频率要求高,保护性能受过渡电阻及噪声干扰影响较大,需配合纵联保护识别故障位置。而现有纵联差动保护易受分布电容影响,传输数据量较大,动作速度有待提升。为了解决上述问题,提出一种基于近似熵变化量判据的混合直流线路纵联保护方案。近似熵需要的计算数据量较小,且兼具高灵敏性、高可靠性优势。故障发生后,近似熵变化量呈现明显的峰值特征,基于1模电压电流近似熵变化量构建的保护判据能快速准确地识别高阻接地故障,同时能减小噪声干扰和分布电容的影响。基于乌东德±800 kV混合直流输电系统仿真模型对所提保护方案进行验证。结果表明,所提保护方案仅需5 kHz采样频率,无需严格的时间同步,且在经800Ω过渡电阻接地及10 dB信噪比场景下能够正确、快速地动作。

Traveling wave protection for an HVDC transmission system has a high requirement on sampling frequency and performance is affected by fault resistance and noise interference.Therefore,it is necessary to combine traveling wave protection with pilot protection to identify the fault location.However,the pilot differential protection is susceptible to the influence of distributed capacitance,the amount of data transmitted by the protection device is large,and the action speed needs to be improved.To solve these problems,a pilot protection scheme for the hybrid HVDC transmission system based on an approximate entropy change criterion is proposed.Approximate entropy requires less data to calculate and has the advantages of high sensitivity and reliability.After a fault occurs,obvious peak characteristics emerge in the approximate entropy change.The protection criterion constructed based on the approximate entropy change of 1-mode voltage can recognize the high-resistance ground fault quickly and accurately,and at the same time reduces the influence of noise interference and distributed capacitance.The proposed protection scheme is verified based on a simulation model of the Wudongde±800 kV hybrid DC transmission system.The results show that the proposed protection scheme requires only a 5 kHz sampling frequency without strict time synchronization.The proposed protection scheme acts correctly and quickly with an 800Ωgrounding resistance fault and under 10 dB signal-to-noise ratio interference.