In response to the problem that the increase in grounding resistance and decrease in current dissipation capacity after corrosion of grounding grid materials can lead to grid faults, this article conducts experimental research on the electrochemical and corrosion resistance of three grounding materials, namely galvanized steel, copper, and conductive polyolefin coated metal, through on-site buried experiments and laboratory indoor simulation. The research results indicate that under long-term corrosive environments, the grounding resistance of conductive polyolefin coated metal grounding materials remains almost unchanged; In the absence of current, conductive polyolefin materials can hardly measure corrosion loss in corrosive environments, while the corrosion rate of galvanized steel is 3-4 times that of copper; Under the same current, the corrosion rate of conductive polyolefin materials in corrosive environments is only 1/30 of that of galvanized steel and 1/20 of that of copper; Conductive polyolefin do not produce corrosion products during the corrosion process, which will not lead to a decrease in the grounding performance of the grounding material. This research result can provide certain reference significance for the material selection of ground grids.

For analyze the impact of feeder imbalance on the transient characteristics of single-1 phase high-impedance grounding faults, an equivalent circuit for single-phase grounding faults is 2 established, which includes multiple feeder imbalance voltage sources. The magnitude and phase of 3 an unbalanced voltage source in a single feeder are solely related to the inherent ground imbalance of 4 that feeder. Meanwhile, the significance of transient fault current characteristics depends on the size 5 of the transition resistance. We propose a state-space-based fault transition resistance identification 6 method and employ linear regression to determine the single-phase ground fault resistance. From 7 the moment the fault occurs, the resistance will gradually decrease from a larger value. The initial 8 resistance, which has a significant effect on the fault transient characteristics, is often large, potentially 9 causing no notable difference between the amplitude of the feeder transient current and the inherent 10 current after the fault. The inherent imbalance of the feeder can severely impact the accuracy of using 11 transient characteristics for line selection.

In response to forest fires caused by single-phase grounding of distribution lines, this paper establishes a mathematical model of single-phase grounding overhead line tree arc in distribution networks based on the theory of magnetic fluid dynamics. The effects of arc length and residual current size on arc characteristics are studied. The simulation results show that under stable arc ignition, the gap distance increases from 4cm to 20cm at the peak of arc voltage, resulting in a decrease in the center temperature of the arc column from 8600K to 7000K, And the peak value of stable arc voltage increases with the increase of arc length and arc radius; The zero crossing arc resistance of the arc current reaches its maximum value, and the arc resistance increases with the increase of arc length and radius. Under the same spacing, the larger the compensation current, the higher the arc temperature, the less likely it is to extinguish the arc, and the lower the arc resistance; When the residual current is 10A, the wind speed reaches 9m/s, and the arc extinguishing time is before the first zero crossing point of the current. The research results can further provide theoretical reference for automatic tuning of suppression coils, residual current setting, and arc extinguishing characteristics.

The switching operation of disconnector in Gas Insulated Substation (GIS) will generate Very Fast Transient Overvoltage(VFTO), forming a transient space electromagnetic field, it causes electromagnetic interference to the electronic transformer connected with GIS and threatens its operation. This paper first studied the electromagnetic field interference of the very fast transient phenomena on the electronic transformer, and analyzed the coupling path of the electromagnetic field radiated by the electronic transformer. Then based on the transmission line theory, a three-dimensional electromagnetic simulation model of GIS connected electronic transformer with VFTO wave as excitation source is established, calculated and analyzed. The calculation results show that the internal radiated electromagnetic field is the most serious in the vertical position between the electronic transformer acquisition unit and the GIS conductive pole. The metal shell of the acquisition unit can act as an electromagnetic radiation shielding box and has a certain electromagnetic protection ability.

针对高土壤电阻率地区变电站接地阻抗难以达标以及雷电冲击导致的变电站二次系统受到暂态干扰等问题,以某220 kV典型变电站为例,现场测试了土壤分层数据、接地网接地阻抗和暂态地电位差分布状况,对其接地网工频和冲击特性多个维度开展了安全评估分析.通过进一步搭建接地网仿真模型,开展仿真计算,得出了初步降阻改造方案.研究结果表明,针对高土壤电阻率地区变电站接地网要通过多个维度去评估其地网安全性,不能盲目追求降低接地阻抗这一单一指标,要通过综合降阻措施使其满足安全设计要求.

Grounding facilities, including high-voltage DC grounding electrodes and auxiliary anodes in impressed current cathodic protection systems, inject current into the ground. This study developed an experimental platform to determine the safe limit of current density for such facilities through an analysis of fish behavior on the platform. Zebrafish (Brachydanio rerio) were selected for the experiment and placed in a tank; two rod electrodes were used to inject direct current into the water. A wireless camera was focused on the water tank to video record possible changes in fish behavior. The output voltage of the DC power source was varied, and the trajectories of the fish under various direct current fields were recorded. A tracking program was developed to analyze the trajectories and quantify the behavior of the fish. A new method combining the trajectories of fish samples with the results of current density calculations for analysis was proposed. Results demonstrated that the zebrafish could sense current in the water and turn when exposed to certain current densities. The intensity of the current at the turning points was statistically analyzed, and the threshold of current density at which the fish could no longer tolerate the current and turned was 0.4231 A/m2.

为掌握直流接地极在海洋环境下的腐蚀特性,进行了典型直流接地极材料在模拟海水和自然海水、海水浸泡沙、海水浸泡焦炭环境下的自然腐蚀和电解腐蚀试验.结果表明:接地极在海水浸泡焦炭中的自然腐蚀最严重,在海水中次之,在海水浸泡沙中最小.在通流时,除高硅铬铁外接地极在海水和海水浸泡沙中的电解腐蚀速率相近,在海水浸泡焦炭中的电解腐蚀速率明显减小;且随着含海水量的增加,焦炭对接地极电解腐蚀的减缓作用逐渐减弱.对不同接地极材料,焦炭的保护系数不同.典型接地极材料中,海洋环境下耐蚀性能最强的是MMO、钛镀铂,其次是石墨、高硅铬铁,再次是不锈钢、镀锌钢、铜.

With the challenge of space size in urban densely populated areas and the increase in power demand, three-phase coaxial high temperature superconducting (HTS) cable has an attractive prospect in its compact structure and low loss. In order to minimize the proximity-effect among conductors of the same phase when the layers per phase increase, a new structure of cable composed of many three-phase groups is proposed, which decomposes the superconducting layers into many magnetically independent three-phase groups. Each three-phase group contains three-phase conductors composed of one or two layers per phase. The ac losses between the proposed and conventional HTS cables are compared by means of an analytical solution. The result shows that the new architecture greatly reduces the ac loss, and the efficiency of reducing loss is enhanced with the increase of layers. Therefore, the proposed cable is expected to replace the copper cables in some mid- or low-voltage levels and high-current conditions.

Among the distribution network faults, single-phase grounding faults have the greatest probability. The faults are often accompanied by arcs in the grounding point soil. This type of fault current has a small amplitude and seldom can obtain field record data. A soil arc grounding fault is tested on a realistic-distribution-network-experimental-platform (RDNEP), and it is concluded that the soil-arc-grounding-fault (SAGF) has three main characteristics: hysteresis, nonlinearity, and asymmetry. By comparing with the characteristics of common arc models, it is pointed out that common arc models cannot accurately fit the characteristics of SAGF. This paper proposes and establishes a double exponential function arc model. Through the comparison of simulation waveforms with experimental data, it is verified that the numerical simulation method proposed in this paper can simulate the development process of SAGF more accurately. Furthermore, the equivalence of RDNEP is verified on the real distribution network system (RDNS). On this basis, analyzed the arc characteristic changes of different SAGF development cycles. Finally, by studying the applicability of the proposed model in simulating ground faults in grass and gravel roads, it is verified that the model proposed in this paper has a strong generalization capability. The research has laid a theoretical foundation for a detection algorithm that is based on the characteristics of SAGF.

对杆塔接地装置的接地电阻测量方法进行了研究,在此基础上,针对所选变电站地网和输电线路上的接地装置进行了电阻检测,制定了工频接地阻抗和冲击接地阻抗测试方案,并进行了现场测试.试验结果表明:输电线路杆塔接地体的冲击接地电阻均大于工频接地电阻,输出电路杆塔接地体的冲击系数整体上随冲击电流幅值的增加而略微减小.

为了更深入掌握雷电冲击下大型变电站接地网的暂态特性,指导变电站的防雷接地设计,建立了大型变电站雷电冲击暂态特性的仿真模型.在此基础上,使用矩量法(MOM)在不同土壤电阻率、不同地网边长、不同网孔大小以及不同雷电流波头时间等情况下分别进行了接地网的雷电冲击暂态特性的仿真计算.结果 表明:土壤电阻率越大,接地网的冲击接地特性越呈现出阻性;地网面积越大,接地网的冲击接地特性越呈现出感性;网孔大小对接地电阻的影响不明显,当网孔边长从50 m下降到10 m时,接地网的工频接地电阻与冲击接地电阻分别下降了22.95％和5.63％;随着雷电流波头时间的增加,接地网的冲击接地电阻与冲击系数近似线性下降.

为研究输电线路绝缘子低零值红外检测方式,分析绝缘子串的电压分布及发热功率,利用耐压设备对含有劣化绝缘子进行红外分析,获取了低零值绝缘子红外热像图谱特征.现场检测结果表明,红外热像技术可通过遥测绝缘子串温度特征来判断绝缘子绝缘性能,并总结出该方法实际应用的优势和缺陷,提出应用该技术的策略建议,为研究绝缘子带电检测低零值提供参考.

为解决小电流接地系统单相接地故障特征不明显的问题,借助小波理论提出了基于DS证据理论的融合判据。首先确定小波基及小波分解尺度,并构造小波能量矩阵以确定故障特征频带。进而,在此特征频带下提取出三种故障特征:小波能量比、小波重构系数方差及暂态功率方向,并分析对比了三种特征的灵敏性。考虑到各个故障选线特征的检测灵敏性不同,为了提高选线准确率,进一步提出了基于DS证据理论的选线融合判据。最后,对现场实录波形进行分析。分析结果表明,该融合判据能够有机融合三种选线特征,提升选线正确率,具有较好的工程应用价值。

中性点非有效接地系统单相弧光高阻接地故障检测的难点在于如何实现灵敏启动.现有的检测方法以零序电压的幅值越限作为启动判据,但是由于对越限门槛值的整定直接影响着检测的灵敏性和可靠性,在实际运行中往往难以同时兼顾.针对该问题,基于现场实测故障录波数据,采用数值统计、傅里叶变换、图形对比等方法从时域、频域角度分析了单相弧光高阻故障的暂态电压特征.搭建了弧光高阻接地故障暂态模型,仿真验证了所提取的暂态电压特征的正确性,为后续故障选线装置应对单相弧光高阻故障的灵敏启动判据开发提供了基础.

为适应电网发展对接地网安全性能的要求,如何能够对接地网的特性参数进行准确的评估并将其延伸到设计环节,成为各单位普遍关注的问题.以典型的500 kV高土壤电阻率变电站接地网设计为例,对比了地网特性参数公式计算、仿真计算、现场实测等方法的准确性,分析目前接地网设计方法存在的不足及其产生原因,分析结果表明:对接地网土壤电阻率测试深度不够以及没考虑变电站各出现线路提供的故障电流对分流系数的影响是接地网设计精度不够的主要因素.在变电站接地工程设计阶段,对土壤电阻率的测试深度至少要达到变电站地网对角线的三分之二,并通过调度部分提供的系统最大运行方式下单相接地短路电流水平对接地网分流系数进行计算,能够显著提高接地网特性参数设计精度.

0 引言 由于进入电网物资的质量关系到电网安全运行,如何有效开展电网物资质量检查工作,切实保证入网产品的质量和电网的运行安全,成为了应积极探索的重要问题[1].传统的电网物资质量管理,主要以到货验收、现场交接试验等方式为主,涉及的物资范围有限,开展的检测项目少,检测周期长[2].对杆塔角钢、设备外壳等材料组成成分的检测能直接反映出设备质量状况,对提高供电可靠性具有重要的实用价值.研究物资抽检现场的柔性服务,对缩短电气设备机械调试周期,提高检测效率,实现设备普检,为电气设备性能评估、合理使用提供基本信息和科学依据,对弥补现有电气设备诊断方法的不足具有重要意义[3-4].

土壤中的碳钢接地材料在电流的作用下会发生腐蚀,从而改变地网的状态,影响主设备的安全运行。为了研究超高压组合电器（hybrid gas insulated substation,HGIS）外壳接地线电流的分布特性,分析其对接地体的腐蚀影响,文中建立了管母线外壳接地线电流分布数学模型,通过对接地线电流的大量实测和统计分析,验证了模型的有效性和正确性。最后,结合试验研究了不同电流密度对碳钢材料的腐蚀作用,提出了电流密度与腐蚀速率关系函数。研究表明:外壳接地线电流大小呈振荡波形分布,并无统一的分布规律。每串单相首末端接地线上电流大小与本相负荷电流的大小呈正相关关系,其它位置接地线上电流大小与该间隔负荷电流的大小关系不明显。负荷电流与该间隔外壳地线电流具有一比例系数k,该值大部分在1030,再根据负荷电流大小可估算出碳钢接地网腐蚀速率的范围。电流密度越大,腐蚀越强烈,随着电流密度的增大,腐蚀速率趋于饱和。

Alternating Current (AC) withstand voltage test is indispensable in hand-over test procedures for switch apparatus,which must be done under the condition of power outages.To explore the way for the AC withstand voltage test without any power outage,the method using synchronized frequency and phase for AC withstand voltage was proposed,and a test device was designed based on the corresponding principle.The results demonstrated that this method is applicable to the substation without any power outage.The designed test device has passed the testing and assessment under different abnormal working conditions in the laboratory and then applied successfully for onsite testing such that its effectiveness is verified.

结合辽宁电网LW6-220型SF6断路器运行情况,对常见故障进行了分析,指出主要故障原因是由于该型断路器绝缘拉杆松动,导致断路器触头开距缩小、静触指缩短、动触指闭合圆扩张不能和静触指可靠接触、绝缘拉杆在开合过程中因强度不够产生松脱等现象,针对上述问题提出了加装导向装置、取消信号缸的改进措施,改造后运行结果证明该方法可靠.