220kV双回路电缆金属护套感应电流计算及敷设方式对其影响分析

选取市区内实际运行的2回220 kV电缆,测量了双回线路在不同敷设形式、不同运行方式下的外护套感应电流。推导了双回路电缆任意敷设方式下的电缆外护套感应电流计算方程,并编写了相应程序,计算结果与实际测量数据基本一致。结果表明,2回线路的互相感应是造成直角敷设方式下外护套接地环流过高的原因,即使一回线路停电,该敷设方式下仍会感应出较高接地环流。基于此,提出了在直角敷设方式下降低外护套接地环流的解决方案。     

电力电缆接地系统缺陷引起环流异常的分析

高压电力电缆金属护套接地系统一旦出现缺陷,将导致电缆金属护层环流异常,长时间运行将损坏电缆绝缘,造成绝缘击穿故障,会严重影响电力电缆的安全稳定运行。以一起高压电缆接地环流异常为例,根据接地系统模型分析护套环流数值,发现A相接地同轴电缆线芯、屏蔽接反是缺陷产生的原因,并分别在带电状态和断电状态下进行了验证。基于此,提出当电缆金属护层环流超过负荷电流80%时,应重点考虑异常情况是否由接地系统接线错误导致,同时,对高压单芯电缆接地系统的接线和验收环节提出改进措施,供工程实践参考。     

电缆金属护层环流的计算分析

<正>目前,交联聚乙烯绝缘电缆已广泛应用于电网中,对于高压线路,一般采用单芯交联聚乙烯绝缘电缆。当电缆长度较长时,金属护层中会产生较高的感应电压,电缆金属护层一般采用交叉互联接地的方式,将交叉互联段两端的感应电压控制在规定值以内。在正常运行情况下,电缆金属护套上会产生环流。当金属护套环流过大时,会使     

基于ATP的高压电缆金属护套多点接地故障仿真

高压电缆金属护套多点接地故障将导致护套环流值显著增大,从而加速电缆绝缘的老化,缩短电缆的使用寿命和输送能力,威胁电力系统的安全稳定运行。笔者对电缆护套环流进行了理论分析,建立电缆的Bergeron模型,利用电磁暂态程序对电缆护套多点接地时故障进行仿真,通过对接地线电流的分析,找出影响环流值大小的因素,以及环流与多点接地故障的相关性规律,为高压电缆护套绝缘的在线监测和故障诊断的判定提供参考。     

单芯XLPE电缆金属护套绝缘在线监测研究

分析了电缆金属护套接地模型,提出了环流法在线监测XLPE电缆金属护套绝缘性能。试验结果表明,环流值与金属护套绝缘性能差异密切相关,因而提出了“环流绝对值”与“环流相对变化量”的判据。开发的在线监测系统能很好地监测电缆金属护套绝缘性能,提高了电缆运行可靠性。     

多回路电缆金属护套环流计算软件的开发与应用

目前城市电网中35kV以上电压等级的电缆线路越来越多,35 kV以上电压等级线路往往使用单芯电缆。单芯电力电缆线芯通过交变电流时,金属护套上会产生感应电势。为了防止感应电压过大对人体造成伤害,需要将金属护套两端牢固接地。当电缆金属护套两端接地时金属护套中会有环流通过,护套环流过大时会严重影响电缆的安全运行。通过MATLAB及LabVIEW软件编程方法实现了计算一至四回路任意排列电缆线路的护套环流,利用环流计算软件提出抑制环流措施和电缆优化敷设方式,为未来电缆敷设提供科学指导意见。     

基于柔性电流钳开发电缆外护套绝缘状态监测的装置设计

护层循环电流和绝缘电阻作为高压电缆安全运行的重要指标,其测量方式尤为重要。本文研究分析了国内外绝缘外护套监测方法及其存在的问题,设计了利用柔性电流钳采样,接地环流法测量的监测装置。阐述了采用柔性电流钳开发电缆外护套绝缘状态监测测量装置的构造和功能,搭建了高压电缆外护套绝缘状态在线监测的模型,并验证了测量结果与理论计算的一致性。     

采用柔性电流钳开发电缆外护套绝缘状态监测的测量装置应用研究

护层循环电流和绝缘电阻作为高压电缆安全运行的重要指标,测量方式尤其重要。分析了国内外绝缘外护套监测方法及其存在的问题,设计了利用柔性电流钳采样,接地环流法测量的监测装置,介绍了采用柔性电流钳开发电缆外护套绝缘状态监测测量装置的构造和功能,实验室搭建了高压电缆外护套绝缘状态在线监测的模型,并验证了测量结果与理论计算的一致性。     

单芯电力电缆金属护套环流计算及分析*

单芯电力电缆金属护套接地环流将降低电缆的额定载流量、缩短电缆的运行寿命,因此针对金属护套两端接地和交叉互联接地的单芯电力电缆,建立了金属护套接地环流的等值电路和计算模型,并推导了相应模型参数的计算式,在此基础上分析、计算了交叉互联接地方式不同工况下的金属护套接地环流值.计算结果表明,三相电缆系统结构和负荷电流的不对称度越大,则金属护套接地环流越大.     

混合排列方式在交叉互联电缆中的应用

城市电网改造引起电缆线路割接,造成原有交叉互联接地方式被打破,这将导致金属护套中产生环流。从分析金属护套环流产生原理入手,找出影响金属护套感应电压的主要因素,通过相量图分析交叉互联电缆金属护套感应电压相量,提出混合排列方式在某些场合可以降低金属护套环流。同时,通过EMTP仿真验证了结论的正确性,并明确了混合排列方式的应用范围。     

Tackling sheath problems: Latest research developments in solving operational sheath problems in underground power transmission cables

In a power transmission cable system, the uniformly configuration of the cables between sections is sometimes difficult to achieve because of the geometrical limitation. This will cause the increase of sheath circulating current which results in the increase of sheath loss and the decrease of permissible current of the power transmission system. While the cable is on operation, because of cable aging and other unexpected reasons, sheath fault always occurs which leads to the further damage of the insulation layer and the life of the cable. These two problems were particularly addressed in this paper. Over last few years, two research groups in South Korea and the United Kingston have worked together extensively to solve these problems and made some great achievements. For tackling the problem of the increase of sheath circulating current, one special device was designed to measure this kind of current; an effective measure was proposed to reduce the current and the new measure was well protected from any further threats like cable fault and lightning. Regarding the problem with sheath fault, one data acquisition system was designed to monitor the sheath fault on field; a new fault phenomenon was discovered for the cable buried in sand; based on the new discovery, the fault was characterised, modelled and simulated; furthermore advanced signal processing techniques were introduced to extract the fault signals from the sheath, detect and locate the fault. These new solutions have either been successfully applied in practical operation of the power cable system or used in further research to propose more advanced solutions. The paper reviewed the latest developments of these new solutions.     

高压电力电缆绝缘在线监测新方法及其实验研究

目前的高压电力电缆绝缘在线监测方法存在无法将主绝缘和外护层绝缘故障进行区分的问题。分析了国内外现有高压电力电缆绝缘在线监测方法存在的问题,提出了利用电缆护套感应电压和护套接地环流进行在线监测,可以区分电缆主绝缘和外护层绝缘故障的在线检测原理,介绍了在实验室搭建的高压电力电缆绝缘在线监测模拟实验装置,经验证实测值与理论计算值一致。     

双回路电缆护套环流计算及影响因素分析

为分析电缆线路中的环流,推导了双回路敷设电缆护套环流的计算方程,并自行编制运算程序实现了计算机求解。结合某电力设计院两回路电缆的实际敷设及运行参数,计算了直线排列交叉互联情况下电缆护套中的环流,并对影响金属护套中环流值大小的相关因素作了简单分析,减小环流值的方法有增大接地电阻、使电缆紧密排列、保证电缆交叉互联段长度相等等。同时,提供了对应单回路敷设情况下的计算结果进行比较,结果表明计算护套环流时双回路不能以单回路情况简化。相关推导过程及程序设计思想可推广应用于双回路电缆的其它敷设形式或更高回路数的电缆线路。     

高压电缆接头除潮工艺探讨

文章分析了110～220kV输电电缆线路中,因中间绝缘接头进潮引起单芯电缆金属护套环流过大的原因及危害,介绍了接头除潮工艺流程及应用,论证了接头除潮工艺解决因进潮引起高压单芯电缆金属护套接地环流问题的可行性.     

Comparative analysisof grounding systems formed by MV cable lines with either uninsulated or insulated metal sheath(s)

It is well known that medium-voltage (MV) paper-insulated cables essentially reduce the potentials appearing during a ground fault in substations located in urban surroundings. This is explained by the fact that these cables usually (normally) have an uncoated metallic sheath. Due to this, MV cable lines leaving a high-voltage/middle-voltage (HV/MV) substation act as long external grounding electrodes and spontaneously form one very large and complex grounding system around this substation. Cables with an insulated metallic sheath however, are progressively being more applied in contemporary power distribution practice. Consequently, the following quite logical question arises: how will a cable with such constructive characteristic influence the general conditions for solving the grounding problem of distribution substations, especially of those working in high-voltage (HV) networks with directly grounded neutral(s)? The analysis performed in this paper shows that, when applied these cables spontaneously form a grounding system which also exhibits excellent grounding performances.     

高压单芯电缆单相接地故障护套过电压特性仿真分析

高压单芯电力电缆在敷设过程中,为了限制感应电压、增加单段电缆长度、减少中间接头数量,金属护套层往往采用交叉互联接地.若电力电缆发生单相接地故障,在交叉互联点会感应出较高的过电压,影响电缆使用寿命.对此利用电磁暂态软件EMTP,研究了在单相接地故障情况下高压单芯电缆金属护套过电压特性,分析了电缆整体排列方式、接地电阻、负荷性质、交叉互联各小段电缆长度以及混合排列方式对金属护套过电压的影响程度.研究结果表明:电缆整体排列方式、交叉互联各小段电缆长度和混合排列方式对金属护套过电压的影响较大;接地电阻和负荷性质对感应过电压的影响较小.     

单芯电缆计及护套环流时载流量的计算

计算了单芯电缆护套两端互联接地计及环流损耗时的载流量 ,得到了计及护套环流损耗时计算电缆载流量较为简单的方法     

高压电缆缓冲层的设计与工艺研究

高压与超高压交联电缆金属护套与电缆缆芯之间的缓冲层是电缆的重要组成部分,对电缆的机械、热性能具有重要的影响。为研究缓冲层对电缆性能的影响,分析了不同的阻水带的热阻特性与工艺特点,对国产两种同型号不同厂家的电缆进行了对比温升试验,最后讨论和分析了现在国内外高压交联电缆缓冲层的结构与工艺特点。研究表明,具有不同结构与材料的缓冲层,对电缆本体的热阻有显著影响,也对电缆载流量有着很大的影响。在此基础上,对国产电缆的缓冲层设计与工艺提出了一些建议。     

Charging Current Data for Guesswork-Free Design of High-Resistance Grounded Systems

The design of high-resistance grounded power systems requires the sizing of the grounding resistor to provide a current flow equal to or greater than three times the system charging current (Ico) of each phase. In industrial power systems the insulated power cables are a major source of system charging current which flows into line-to-ground faults. Data are presented which will allow cable charging currents to be quickly and precisely determined after the cable size, voltage, footage, insulation type, and thickness have been determined. Charging current data for transformers, motors, generators, and capacitors are also included.     

有限元法计算交联电缆涡流损耗

电力电缆的导体交流损耗和金属屏蔽层涡流损耗是影响电缆群温度场分布和电缆载流量确定的重要因素。为确定电缆运行中的损耗,在考虑趋肤效应和邻近效应的基础上,利用有限元法对电缆群不同排列方式和接地方式下的导体交流损耗和金属屏蔽层涡流损耗进行了计算。计算结果表明,导体交流损耗随回路数增多、电缆间距减小而增大,金属屏蔽层损耗随回路数增多而增大,与电缆间距的关系与接地方式有关,单端接地时,金属屏蔽层损耗随间距增大而减小,双端接地时,金属屏蔽层损耗随间距增大而增大。