The metallic grounding equipotential strip (MGES) in the cable tunnel and the grounding resistance of the power source in the simulation model are critical factors affecting the accuracy of zero-sequence impedance parameter calculations for cable lines. However, existing literature has rarely addressed this issue. Focusing on 500 kV cable lines, this study analyzes the impact of the MGES on the zero-sequence impedance parameters. Simulations were conducted to calculate the zero-sequence impedance parameters with and without the bonding strip, as well as the effects of the location and magnitude of grounding resistances on these parameters. Furthermore, considering various hybrid configurations of cables and overhead lines, a comparative analysis was performed between the simulated and field-measured zero-sequence impedance parameters.The research results indicate that when the MGES is present, the zero-sequence impedance of the cable is significantly lower than that without it, with the maximum difference reaching up to 4 to 5 times. When the test power source shares a common grounding grid with the sending end of the cable, the measured zero-sequence resistance of the cable line is approximately 1/5 to 1/10 of the simulated value, while the discrepancy in zero-sequence reactance remains relatively minor.

To master the influence range and influencing factors of DC grounding electrodes on DC bias in AC power grids, a DC resistance network model covering substation grounding grids, transformers, and transmission lines is established. The distribution of transformer bias current at different distances was calculated, and influence of factors such as grounding current, line length, line orientation, and soil resistivity on the influence range and safety distance of DC bias are analyzed. The results show that the physical configuration of grounding electrodes exerts minimal effect on far-field surface potential distribution, allowing simplified representation as concentrated current sources. The larger the grounding current, the closer the line orientation is to the radial direction, and the higher the deep soil resistivity, the greater the influence range and safety distance. The longer the line, the greater the increase in line resistance compared to the increase in potential, resulting in a decrease in the influence range. Taking the actual power grid around the shared grounding electrode Maibu as an example, the distribution and expansion trend of substations where bias current exceeding the standard limit and influence range under different operating modes were evaluated. The research findings serve as a reference for the site selection of grounding electrode and substations, as well as the assessment of DC bias risk.

To master the true impulse characteristics of tower earthing devices in high-resistance areas and improve the technical and economic efficiency of tower grounding device design, lightning impulse high current tests were conducted on several real tower grounding devices under high-resistance geological conditions of Xizang high-altitude test base, and the impact characteristics were analyzed in relation to factors such as the angle, length, and quantity of rays.. Futhermore, a simulation calculation model for the impact characteristics was established, and the optimization selection method for the structure of grounding devices was analyzed. The results indicate that the impact grounding impedance is the smallest when the ray is at the 135 degrees angle in the structure of a square frame with four rays. As the length of the ray increases, the impact grounding impedance decreases, but there is an effective length. After exceeding the effective length, continuing to increase the length will result in a small reduction in impedance. When the overall length of the earthing body remains constant, redesigning the grounding device to have more rays when the ray length exceeds the maximum length can further reduce impedance. The impedance reduction effect of branch rays set at the beginning of the main ray is better than that at the middle and end.

In order to improve the technical and economic efficiency of grounding bodies for transmission lines and guide the selection of lightning impulse impedance reduction methods for horizontal grounding conductors, true type tests of impact characteristics were conducted on the horizontal grounding bodies and their additional conductors under larger sizes and higher currents. The influence of the length, cross-section, and material of the grounding body on the impulse characteristics was analyzed, and the differences of the impedance reduction effects of the additional conductor arrangement, quantity, and type were compared. The results show that among typical grounding materials, the material of the horizontal grounding body has little effect on the impact characteristics, and the cross-sectional size has a slight effect on the impact characteristics. Increasing the length has a more obvious effect on the impact impedance reduction of the horizontal grounding body, but there is an effective length. Additional conductors can be added on the horizontal ray to further reduce the grounding impedance. When only one additional conductor is arranged, it is advisable to place it at the injection point. When two additional conductors are arranged, in addition to the injection point, the other location should be close to the middle or the latter half of the ray. The more the number of additional conductors is arranged, the more the impedance reduction effect is, but there is a saturation effect. Under high lightning impulse currents, additional conductors on the horizontal ray can directly replace the grounding module with the horizontal conductor, thereby improving the economic efficiency of impedance reduction measures.

Coastal grounding electrodes are currently an important means to alleviate land grounding electrode land constraints. In order to better invert the terrestrial geodesic resistivity in the coastal region, this paper proposes a complete set of inversion technology schemes. First, this paper proposes a layered land model for the coastal region, and a composite geodetic model is modeled by the fold junction of the land model and the ocean. Based on this, an adaptive subdivision boundary element method is proposed for solving the composite soil grounding calculation problem, and the accuracy and advantages of the method are demonstrated by examples. Finally, the paper uses the differential evolutionary algorithm to invert the exploration data of the four-point method in the coastal area, and obtains the parameters of the terrestrial layered geodetic model that meet the engineering requirements. The comparison with the grounding software CDEGS illustrates the effectiveness of the method. This paper carries out the research on the modeling and inversion methods of composite layered soil model, combining advanced numerical calculation methods and artificial intelligence algorithms to provide the support of computational tools for coastal resistivity inversion.

为提高输电线路杆塔接地装置设计的科学性和针对性,在分析反击跳闸率和接地电阻的影响因素的基础上,提出了基于输电线路反击跳闸率控制目标和蒙特卡洛法择优筛选的杆塔接地电阻控制值的差异化设计方法.即充分考虑影响反击跳闸率的各因素,根据杆塔结构参数、绝缘子串参数、沿线土壤电阻率、地形、雷电参数等进行反击跳闸率计算和区段划分,对各区段反击跳闸率进行加权平均获得线路总体反击跳闸率,再将其与反击跳闸率控制目标进行比对,并通过蒙特卡洛法实现在多种区段划分和接地电阻控制值中的择优选择,作为杆塔接地电阻的优化设计控制值.给出了蒙特卡洛法计算步骤和典型实例,计算结果满足预设要求.

In order to master the grounding performance of the cable tunnel reinforced concrete and optimize the grounding design of underground cables, taking a 110kV cable tunnel as an object, a cable total grounding grid model composed of cable tunnel reinforced concrete and grounding grids of substations at both ends is established, and the grounding resistance, current and potential distribution of cable grounding wires, contact potential difference and step potential difference in the cable tunnel and on the ground surface along the tunnel and the substations at both ends are calculated and analyzed. The results show that the grounding resistance of the cable tunnel reinforced concrete and the total grounding grid is about 0.1Ω, which meets the relevant grounding resistance requirements of cable grounding. In case of short circuit fault, the current mainly enters the ground from the grounding wires at both ends, which may account for more than 90%. The potential rise of the grounding strip is U-shaped. The maximum contact potential difference and step potential difference appear on the surface of substations at both ends, and the maximum potential difference can meet the requirements of personal safety.

Soil ionisation has an important influence on impulse characteristics of grounding conductor. This paper introduced improvements to an existing soil ionisation model considering the influence of electric field on the change of soil resistivity, while soil resistivity is not directly dependent on soil electric field. The validity of improved soil ionisation model was verified by surge response of vertical conductor in uniform soil and horizontally stratified soil. Furthermore, the impulse experiment was carried out on horizontal conductor in soil with finite volumes. Based on experimental configuration, the corresponding calculation model was built, and calculated results were in good agreement with experimental results.

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.

为了掌握加装均流电阻对直流接地极运行性能的影响，为均流电阻装置的应用及运维提供参考，以水平圆环接地极为对象，分析了接地极加装均流电阻后的电气性能和温升性能变化，以及均流电阻阻值偏移对接地极电流分布和跨步电压的影响。结果表明：加装均流电阻可以使电流在各环段上的分配更均衡，相应的各极环附近最大跨步电压和温升更均衡，从而减小接地极的最大跨步电压和最大温升。均流电阻阻值偏移量越大，极环电流和最大跨步电压的变化量越大；当各极环均流电阻阻值的偏移量不均衡时，极环电流和最大跨步电压的变化量会进一步增加。若要将最大跨步电压的变化控制在10%内，均流电阻阻值的偏移量不宜超过5%。

在高压直流接地极工程中,加装均流电阻是改善地表电位分布,降低极址跨步电压的一种有效手段.然而,由于土壤电阻率分布的复杂性和各向差异性,采用理想的水平分层模型计算配置直流接地极的均流电阻往往存在较大的误差.针对此问题,文中提出了 一种基于接地极特性参数实测值的均流电阻配置方法.该方法通过实际测量接地极极环各段的分流比例、接地电阻、互阻、自跨步电压系数、互跨步电压系数等参数,以此作为输入条件,将各段的跨步电压相等作为控制目标,计算获得均流电阻的配置方案.最后通过一个缩比接地极模型,对均流电阻配置方法及过程进行了模拟试验.试验表明,加装均流电阻后,场区的最大跨步电压降低了 31％,效果显著,验证了均流电阻对降低跨步电压的有效性.

In order to master the safety of the GIL shell grounding system of the 1000kV AC UHV GIL tunnel project and support the design and construction of the project, a shell grounding system model consisting of the main grounding grid of connection stations on both sides, the tower grounding grid of overhead ground wires on both sides and the tunnel grounding grid is established. The GIL current and potential distribution under normal operation and short-circuit fault are calculated, and the influence and setting of grounding poles and three-phase connection poles are analyzed. The results show that: under normal operation, the current of connection poles and grounding poles along the GIL presents a U-shaped distribution. In case of short-circuit fault, besides the two ends, the current of the connection poles and grounding poles near the fault point also presents a peak, which can reach hundreds of amperes; and the distribution of potential and potential difference along the GIL also presents a similar U-shaped feature. The spacing of grounding poles can be set within 300m, which can ensure that the potential difference is within the safety limit. The copper bar of 50mm×5mm can be selected for both the grounding pole and the intermediate connecting pole, and the conductor with larger cross section is needed for the connection pole at both ends due to the long-term passing current close to the rated value.

通过溶液加速腐蚀试验和电偶加速腐蚀试验对比,研究了我国目前使用较多的几种新型接地材料的耐蚀性,并对比分析了酸碱性环境中各种材料的溶液加速腐蚀速率和电偶加速腐蚀速率.结果表明:在酸性环境中,不锈钢、高硅铬铁和碳纳米改性材料具备良好的耐蚀性,其中高硅铬铁的电偶腐蚀速率最小;在碱性环境中,不锈钢、高硅铬铁和石墨烯复合材料具备良好的耐蚀性,其中石墨烯复合材料的电偶腐蚀速率最小;在中性环境中,不锈钢和高硅铬铁都具备良好的耐蚀性,不锈钢的耐电偶腐蚀性能更好.

In HVDC transmission projects, sea electrode has a broad application prospect because of the good conductivity and heat dissipation of seawater. Temperature rise is one of the limiting conditions for grounding electrode. After analyzing the distribution of the current field, the calculation model is simplified to an infinite length cylindrical grounding electrode, and the flow field model of circular cylinder is simplified to a planar one. With the help of MATLAB, typical value of temperature rise of sea electrode is calculated, and the influencing factors such as current density, seawater resistivity, seawater velocity and seawater thermal characteristic parameters are analyzed. It is found that the temperature rise of sea electrode is about 0.00005 °C. The low resistivity is the key factor leads to a smaller temperature rise.

Compared with metallic grounding material, flexible graphite grounding material is widely applied in grounding field of power system, due to its resistance of corrosion and high impulse current. Novel phosphorus contained Schiff-base is synthesized by 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide and furfuryl amine, salicylaldehyde, and is incorporating with CE to prepare a carbon foam by property of the resin blend under nitrogen atmosphere. The curing behavior and pyrolysis mechanism of the resin are investigated by DMA, TGA, FTIR and Raman spectrum. The results indicated that incorporating of PSF leads to incomplete combustion during the pyrolysis processing and results in more residues formed. As the consequence, the carbon foam exhibits good electrical conductivity, due to the formed residues consist of graphite structure.

为了研究异性导电媒质对直流接地极跨步电压分布的影响,通过CDEGS建立水平双圆环直流接地极模型,计算极址外部附近以及极址区域内存在异性导电媒质时的跨步电压分布.结果表明:当接地极极址外部附近存在一块高(低)电阻率的异性媒质时,将会使外环靠近异性媒质区域的溢流密度及跨步电压下降(升高);当极址内部的表层局部区域存在一块高(低)电阻率的异性媒质时,将会使位于异性导电媒质的环段的溢流密度下降(升高),但跨步电压却反而增加(降低);当极址内部的下层局部区域存在一块高(低)电阻率的异性媒质时,将会使位于异性导电媒质的环段的溢流密度和跨步电压同时降低(升高).研究成果可为直流输电工程中接地极设计及选址提供参考.

研究了土壤含水量、电流密度以及长时间电流作用对电阻率的影响.通过试验研究可知,土壤含水量越高电阻率越低,同时直流下电阻率最大值对应的电流密度也越高;土壤电阻率随电流密度呈现先增大后减小的趋势,河沙随电流密度增大而增大;在有限元仿真软件中,基于试验结果建模计算得到了直流电流下土壤电阻率与电流密度的函数,验证了电阻率非线性特性模型应用于接地参数计算中的可行性.

接地极的温升问题可能会影响接地极的安全稳定运行,接地极在土壤中散流,在电流场的作用下产生焦耳热并进行热传导.实际上,土壤的参数会随着温度改变,导致电流场变化,进而影响热传导过程,即电流场与温度场之间相互影响.通过试验获取土壤的电阻率温度特性、导热系数和容积热容量数据并建立电流场和温度场的全耦合模型.将2种仿真计算结果与试验得到的温升、电压数据进行对比,结果发现:不考虑土壤电阻率温度特性时前期的结果与试验结果较为符合,后期的温升速率继续降低则与试验中后期温度迅速增加的现象相矛盾;仿真中考虑土壤电阻率温度特性时温升和电极电压仿真结果趋势均与试验结果趋势符合较好,且此时有助于削弱端部效应,所以应该将土壤电阻率温度特性引入接地极的发热分析.

为研究土壤特性对特高压直流接地极跨步电压分布的影响,采用CDEGS软件建立了双圆环直流接地极仿真模型,对比分析了不同土壤特性下双圆环直流接地极上方跨步电压分布规律.计算结果表明:在均匀土壤中,双圆环直流接地极上方跨步电压随着土壤电阻率的增大而升高;在水平双层土壤中,表层土壤电阻率的变化对双圆环直流接地极上方跨步电压分布影响较为显著,当表层土壤超过一定厚度后,表层土壤厚度的变化对双圆环直流接地极上方跨步电压影响较小.