Addressing the unreliability and inaccuracy of current offline fault location methods for overhead distribution networks,this study proposes an offline fault location method based on satellite timing.To locate the fault,an AC voltage signal of fixed frequency and phase is injected at the fault line's origin after power isolation.Subsequently,the fault line is manually surveyed with a portable signal receiver.Synchronous sampling,enabled by satellite timing,allows for the determination of the zero-sequence impedance angle at each monitoring point without voltage data.The precise fault location is deduced by analyzing the variance in zero-sequence impedance angles across multiple monitoring points.Moreover,the study examines how the injected signal's frequency,the fault point's transient resistance,and clock synchronization discrepancies affect the accuracy of fault localization.Simulations validate the approach's precision in identifying fault locations.
Wideband oscillation emergency control is one of the"bottom line"measures to ensure the safe operation of wind power systems.It is difficult to establish an accurate mathematical model to assess this risk,due to the complex and variable nature of wind power systems.To address this issue,a new emergency control strategy has been proposed that is based on data analysis.Firstly,a wideband phasor monitoring algorithm has been developed to detect and assess wideband oscillation.Secondly,the largest Lyapunov exponent(LLE)is used to measure the dynamic evolution trend of wideband oscillation and identify its source.The oscillation source is identified by analyzing the negative resistance characteristic of the wind turbine.Based on the identification results,an online risk assessment method for wideband oscillation has been proposed and applied to the emergency control strategy.The effectiveness and reliability of the proposed method have been verified using a real-time digital simulator(RTDS)hardware-in-the-loop platform.
With the increasing complexity of power systems in recent years,transformer operation safety has become a key issue that affects the stable operation of the power system.Currently,calculation methods of short-circuit current through transformers are mostly based on the power grid topology and transformer equivalent impedance.These methods have low flexibility and real-time performance and do not consider the actual operation mode of the system,making it difficult to meet the requirements of real-time operation of power systems.In this paper,a transformer short-circuit current calculation method considering flow conditions is proposed based on a graph convolutional neural network.By introducing the features of transformer bus and regional topology,a transformer short-circuit current calculation model is trained.This method introduces attention mechanisms to make the model more sensitive to dynamic power flow conditions under different operating conditions.Verified by an actual power grid example in a region,the calculated short-circuit current using this method has a small error compared to the reference value,and the distribution of calculation errors is concentrated,which can basically meet the requirements of short-circuit current calculation in practical operation.
英国是世界上新能源发电接入率最高的国家之一，新型电力系统的特点在英国已经较为明显。英国总调在频率管理方面的成果和经验对中国新型电力系统建设有很高的借鉴价值。首先研究分析了英国总调在新型电力系统建设中，在频率管理方面遇到的风险及其产生机理。然后研究分析了英国总调应对风险的方案和实践经验。最后，研究分析了英国总调在频率管理方面的方案和实践经验对中国新型电力系统建设中频率管理的启示。参照英国的频率管理体系和辅助服务市场建设路径，中国应当重点关注频率管理体系的完善、系统惯量需求的研究和频率支撑技术的研发及应用。此外，应提前布局相关标准，避免分布式电源大面积脱网的风险。
随着台风、暴雪等极端恶劣环境的不断常态化，单相接地故障（如单相断线、单相击穿等）频繁发生，严重危害了电网安全。单相断线故障是引发森林火灾的常见故障之一，导线断线坠落至地面附近，在极短间隙内对地放电引燃地表附着的易燃物，最终引发森林火灾，对社会经济和自然环境危害严重。针对森林火灾风险下的配电线路单相断线对地放电发展过程研究建立短间隙放电模型，可以获得断口对地放电过程中的电场分布、电子平均能量分布、电子密度分布，以及不同断口外形对放电过程的影响机理。研究结果表明，随着断口半径从0.5 mm降至0.3 mm，流注头部的电场强度从80 kV/cm升高到110 kV/cm，电子平均能量从10 eV升高到11 eV，流注贯穿间隙时电子密度的最大值由1.5×1020 m-3升高到2.7×1020 m-3。断口半径越小、曲率越大，导致流注头部的电场强度和电子平均能量升高，流注头部电子密度和放电电流增加，更容易导致流注贯穿间隙。而断口不规则时由于具有更大半径，间隙击穿需要更长时间，因此放电电流峰值由9 A升高至15 A。如果考虑松针等含油量较高的地表附着物影响，该放电电流极易点燃地表附着物并形成电弧、引发火灾。该研究结果对于极端天气下的配电线路安全防护、预防森林火灾具有重要意义。
