配电网小电阻接地方式主要存在供电可靠性低、发生高阻接地故障时选线失灵的问题.本研究将建立小电阻接地模型进行理论分析,并针对目前小电阻接地系统所出现的缺陷,提出一种经动态电阻接地方式.该方式根据三相电压、中性点电压以及各馈线零序电流之间的关系将不同单相接地故障进行分类处理.特别是在解决高阻故障时,通过动态电阻接地方式增加各馈线零序电流进解决小电阻存在的高阻选线缺陷.为验证该接地方式的有效性,在漯河真型试验场进行了现场试验.试验表明动态电阻接地方式在保留小电阻接地方式优点的同时,有效的解决了小电阻接地方式供电可靠性低以及高阻选线失灵的问题.

主动干预型熄弧装置具有良好的电压熄弧效果,但诸多文献进行原理分析时未考虑线路阻抗参数,需要进一步分析其处理电弧接地故障的性能.考虑故障线路阻抗参数,建立单相电弧接地故障时变电站内故障相进行金属性接地的等值电路,采用叠加原理疏导出故障点电流、变电站内接地点电流表达式,分析发现,故障点电流不仅与过渡电阻有关,还受到负载电流和线路阻抗的影响.理论分析了主动干预型熄弧装置熄弧性能和其存在的问题,发现在配电网重负载情况下且过渡电阻远大于线路阻抗时,采用主动干预型熄弧装置会增大故障点电流,促进电弧的燃烧.针对主动干预型熄弧装置存在人身、设备安全和熄弧障碍问题提出相应的解决措施.最后通过PSCAD/EMTD验证了本研究分析的结果.

从原理上分析了消弧线圈并电阻接地方式,并采用MATLAB软件进行仿真,得到消弧线圈并小电阻接地方式仅能处理过渡电阻为125Ω的接地故障;消弧线圈并中电阻接地方式在对称电网中的接地电阻识别能力可达2000Ω,但在电网极不对称的情况下最多能识别800Ω的接地电阻.在此基础上,提出了基于阻性分量提取法的动态接地方式,它通过突变量启动法触发选线装置,运用阻性分量提取法判定故障线路,在高阻接地故障下仍能准确选线.漯河10 kV真型试验场进行的试验表明,动态接地方式能可靠处理3500Ω的高阻接地故障,这为提高消弧线圈接地方式下选线准确率提供了指导意义.

近年来,配电网规模不断扩大,随之增长的是因高压触电所引起的人身伤亡事故,每年因触电造成的人员重伤及死亡的数字非常惊人.对配电网中性点经小电阻接地方式的零序保护进行了理论和Matlab仿真软件计算分析,表明小电阻接地系统无法处理人身触电问题.针对该问题,提出一种中性点智能电阻接地方法.该方法根据中性点电压对故障进行分区,将故障分为高阻、中阻及低阻接地故障.对于人身触电高阻接地故障能快速切除故障线路,保证人身安全.在漯河10 kV真型试验场对该方法进行了试验验证.结果表明:配电网中性点智能电阻接地方法具有5000Ω高阻接地故障的识别和处理能力,可以保证人身安全.

If the arbitrariness of the asymmetrical voltage direction is ignored, it is impossible to accurately describe the trajectory of neutral point displacement voltage varying with the transition resistance when a single-phase grounding fault occurs in the distribution network. Considering the conductance of ground leakage and the direction of asymmetrical voltage, an accurate model of single-phase grounding fault is established. In the incomplete compensation state, the trajectory of neutral point displacement voltage varing with transition resistance is a circular arc; in the full compensation state, the trajectory of neutral point displacement voltage varied with transition resistance is a straight-line segment. According to the analysis: the amplitude of fault phase voltage decreases after grounding, the fault phase voltage after grounding is ahead of the phase voltage before fault in the under-compensated state, the fault phase voltage after grounding lags behind the phase voltage before fault in the over-compensated state, the voltage of the fault phase before and after grounding remains unchanged in the fully compensated state. By comparing the relative change of amplitude and phase of three-phase voltage before and after fault, the grounding fault phase can be identified. Finally, the analysis are verified by MATLAB/Simulink simulations.

通过深度分析中性点经小电阻接地方式所存在的问题,提出了一种配电网中性点经智能电阻接地方式.与小电阻接地方式相比,智能电阻采用分区法,根据中性点电压大小将故障类型分为高阻、中阻以及低阻3个区域.在低阻故障时,能够快速选线跳闸;在中阻故障时,经过延时判断,避免对瞬时性故障的误判;在高阻故障时,启动中、低电阻动态切换,进行准确选线.综合理论分析和仿真计算可得:智能电阻接地方式不仅拥有小电阻接地方式的优点,还能够解决小电阻接地方式中部分供电可靠性低、单相低阻接地时故障点电流过大及单相断线(高阻)接地时零序保护"失灵"等死区问题.该方式对保障电力系统正常运行和人身安全等具有重要意义.

配电网经小电阻接地方式存在高阻死区,对人身安全、供电可靠性、电网安全皆有一定影响.为了解决小电阻接地方式存在的问题,提出了一种基于单相接地故障分区的配电网智能电阻接地方法.该方法根据电网中性点位移电压及故障线路电流变化将故障分区,在高阻故障区采用双增量启动,快速选线切除故障;在中、低阻故障区采用不同的延时处理,使瞬时性故障恢复,提高配电网的供电可靠性和人身及电网的安全性.开发的装置经试验证明,其具有5 000 Ω的高阻识别处理能力,能使达65 A电流幅值的瞬时性故障恢复,并能准确判断及切除永久性故障.相比小电阻接地方式,智能电阻接地能够有效提高人身安全、电网安全和供电可靠性.

为了解决配电网中性点接地方式具有的人身安全、接地选线及供电可靠性问题,开发了基于故障相智能接地处理方式的配电网多功能安全接地处理装置,该装置采用了铁磁谐振动态预警判断技术、分区式故障相选相技术、故障性质的智能判断与处理技术和自适应接地选线技术解决了配电网铁磁谐振动态预警、判断与处理,解决了过渡电阻接地时的精准选相,解决了故障性质的智能判断与处理,能使瞬时性故障快速恢复,使永久性故障选线精确率提高到百分百,能处理0-2000 A的故障电流.装置经在电网的试验及运行效果证明:装置解决了中性点经消弧线圈接地方式的安全瓶颈、容量瓶颈和选线难题,解决了中性点经小电阻接地方式的供电可靠性问题和经高阻接地时的安全问题,为目前在中性点接地领域上的理想换代产品.

通过对配电网中性点经消弧线圈接地方式,以及小电阻接地方式的特点分析及存在的问题进行了更加深入地研究,并开发研制出了配电网中性点动态接地成套装置.该装置具备消弧线圈接地与小电阻接地方式二者的优点,又能够灵活地解决两者存在的缺点.其功能在于配电网发生单相接地故障时,依据故障特征量和参数,就可以对故障的性质进行智能判断.满足在瞬时性接地故障时,故障点的绝缘水平能够快速恢复,提高了电网供电可靠性;同时在永久性单相接地故障时,能够快速且准确地选出,并切除故障线路,确保了设备和人身安全.经大量实验及运行结果证明:从消弧线圈接地方式分析,配电网中性点动态接地装置解决了接地选线和人身安全得难题;而从小电阻接地方式角度分析,解决了供电可靠性和高阻接地时零序保护"失灵"的问题,因此该装置是当前配电网中性点接地的理想产品.

快速接地开关兼具电压、电流双重消弧效果,但传统分析未考虑线路压降对故障点电流的影响,需进一步分析其消弧性能。考虑故障线路动态参数,建立应用快速接地开关的配电网单相接地故障模型,采用对称分量法推导出故障点电流计算公式。计算结果显示故障点电流受故障线路负载电流、序阻抗、相间电容、故障距离以及过渡电阻等多重因素影响。分析快速接地开关等效熄弧电路模型,表明快速接地开关可有效抑制间歇性弧光接地过电压,但在故障线路动态参数造成故障线路压降较大的稳定低阻燃弧过程中,快速接地开关可能增大故障点电流,不利于电弧熄灭。结合快速接地开关的优缺点分别对单独应用快速接地开关消弧及其与消弧线圈配合消弧提出建议。最后通过MATLAB仿真验证了文中的分析结果。

本文针对在应用最大位移电压法时,测量谐振接地系统的电容电流与实际值存在较大误差,发现该方法存在不足,提出了新的改进方法.通过对原始的谐振测量法原理的分析,阐述了该方法在实际应用中的问题.通过实际分析,本文改进了最大位移电压法测量电容电流表达式,并将该表达式集成到电容电流测试装置中,现场试验结果表明改进后的电容电流测量方法具有更高的精度.

An effective device to reduce the earth resistance of grounding systems for power transmission towers on rocky mountain tops with high soil resistivity and constrained area is proposed in this paper. In these scenarios, conventional methods such as using horizontal electrodes to reduce ground resistance require more space and fine‐grained soil for backfill. These methods are not applicable to scenarios where the ground consists of rock or crushed stone. To tackle such limitations, we propose an effective approach with less space and soil requirements. Based on the steady electric current field theory and the electrostatic field, the proposed approach designs a central grounding system by a special steel reinforcement cage. The layout of the cage is strictly based on theoretical calculations. The resistance of the central grounding system can be obtained by calculation and measurement. Results show that this scheme can reduce ground resistance effectively in comparison with the traditional method of imbedding horizontal radial electrodes in high‐resistivity soil on mountain tops where space is limited and excavation conditions are poor. The proposed method has also been validated in practical applications. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

There are strong randomness and fuzziness between the symptom and the mechanism of power transformer failures,and due to the one-sideness in the consideration and imperfection of knowledge base it is often hard to meet practical requirement of power transformer fault diagnosis by the single diagnosis method.For this reason,based on respective diagnosis results by IEC-60599 three-ratio method,fuzzy diagnosis method,ant colony optimization(ACO) and grey system theory(GST) algorithm an optimal combined model is constructed to diagnose power transformer fault.Practical fault diagnosis examples show that the proposed fault diagnosis idea can remedy such insufficiencies of not all-inclusive information and one-sideness of diagnosis in single diagnosis method.The proposed diagnosis method possesses better robustness and higher fault diagnosis accuracy can be achieved by it.

A specific lightning strike fault happened on a 110 kV double circuit transmission line in the Shaoguan area is analyzed,it is concluded that the main reason caused back flashover happened on 110 kV line is the low lightning withstand level,and the lightning and tripping out occurred in the same time usually caused by small difference between the lightning withstand level of double circuit line.Based on the theoretical analysis and combined the actual situation,some measures are proposed to improve the lightning withstand level and increase the difference between the lightning withstand level of double circuit line,such as reduce the grounding resistance of the tower,adopt a balanced high insulation and erection of coupling line.In addition,a new lateral rod with griding ball is used to avoid the lightning shielding failure,there is better disperse effect after lightening current crossed the griding ball.Theoretical analysis shows that these measures can receive a better lightning protection effect.

The shunt coefficient of overhead ground line is the basic data for defining the target value of substation grounding resistance for substation inside short circuit fault.The circuit model of overhead ground line shunting for substation inside short circuit fault is analyzed and a method of shunt coefficient calculation based on the loop current method is proposed for single overhead grounding line.It is extended to the shunt coefficient calculation for all overhead lines.Its correctness is verified by the comparison with the measured site data.

The cause of lightning interference on substation room are analyzed and studied,and the deficiency that locality there exists in transformer substation room lightning protection is pointed out combining with current situation surveying in Shaoguan city: the local machine room power source lightning protection and signal lightning protection have not added mostly;meanwhile,the equipotential bonding mode is improper,the grounding copper cable being excessively long is also a important cause of the microcomputer system failure.And then based on the field investigation,corresponding modification measures are proposed: installation of lightning protection and signal lightning protection,S-type equipotential connection on the room' s computer system,reducing the potential difference,etc.And grounding method is simulated by using the ATP software,and the effectiveness of using S-type grounding method is verified.

The main reason of lightning harm of distribution transformer in mountain area is analyzed.The measures to improve lightning protection of distribution transformer in mountain area are presented.

The current problems of substation grounding have become increasingly prominent, commonly used resistance reducing measures limited by various factors,and other issues,the use of natural grounding body in reducing substation grounding resistance is discussed,and combined with a Fujian 110 kV substation reconstruction case,the rationality and superiority of natural grounding device are analyzed.It is believed that in the grounding project,full use of natural grounding body can not only reduce grounding resistance,but also save time and materials,stable grounding resistance,extend using time,increase security and so on;the geographical conditions around substation should be fully taken into account during grounding device design,and natural grounding body should be reasonably used to reduce the grounding resistance.

The lighting accidents of distribution transformer in qinzhou of Guangxi occur seriously so that it is required to reform the lighting protection.Based on the field investigation and experiments of measuring the earth resistance,it is proposed by relevant theory that the distribution transformers suffering lighting strike is due to the defective lighting protection,including unequipped low voltage arresters,problematic earth device and earth resistance beyond standard value.Based on the analysis,some measures are proposed such as installing low voltage arresters,connecting the coilout at low voltage side with cable and overhead line,reforming earth device and reducing the ground resistance.

This paper put forward a way that use a kind of adjustable gap lightning protection device to minimize bad effects of the flashover and explosion of insulator and the breakage of insulated conductor caused by lightning in the 10~35 kV distribution network overhead lines,and analyzed the operation principle of the protection device and its characteristics.A mass of lightning impulse test and volt-second characteristics has performed with this device,and the results showed that the adjustable gap lightning protection device can effectively avoid flashover damages to the insulator(s) when lightning stroke the overhead lines and reduce the probability of the breakage of insulated conductor caused by lightning stroke effectively.