厂用6KV系统的电压不平衡现象分析

在发电厂的高压厂用6KV系统配电装置运行中,经常会发生高压厂用母线电压不平衡的异常现象,导致高压厂用母线电压不平衡的原因主要有母线接地、高低压保险熔断及发生电压谐振等等,就发电厂的高压厂用6KV系统配电装置中的电压不平衡现象进行分析判别,对造成母线电压不平衡的原因进行分析总结.     

河口油区6kVPT高压保险频繁熔断问题分析

在6kV35kV中性点不接地系统中,用于保护电磁式电压互感器的熔断器经常由于系统单相接地故障引发熔丝熔断,严重时甚至烧毁电压互感器．本文主要概述电压互感器熔断器熔断的常见原因,然后就渤五变电站6kV母线电压互感器出现高压熔断器频繁熔断这一现象进行原因分析,最后根据研究结果,提出相应的抑制措施。     

35kV母线电压互感器熔断器频繁熔断的原因分析及处理方法

针对变电站35kV母线电压互感器高压熔断器频繁熔断现象,通过故障统计并结合电压互感器的等值电路进行详细分析,得出了在电力系统发生相对地电容改变、单相接地故障或负荷大幅波动的过渡过程中,电压互感器铁芯深度饱和激发铁磁谐振,从而导致TV高压熔断器熔断的结论;同时提出了在电压互感器二次剩余绕组并联阻尼器来抑制铁磁谐振、对长线路进行分段换位来抑制零序不平衡电容电流产生等防止电压互感器熔断器熔断的措施。     

110kV电压互感器二次侧空气开关跳闸的原因分析与探讨

某变电站在进行110kV母线倒闸操作过程中,出现110kV电压互感器二次侧空气开关不明原因跳闸。从空气开关跳闸的原因分析入手,找出110kV电压互感器二次侧空气开关跳闸的原因和解决方法,供变电运行的同行在发生类似问题时参考。     

刍议小电流接地系统电压不平衡

在变电站运行中,为保证供电可靠性,35kV电网采用中性点不接地系统,对于中性点不接地系统,变电运行人员经常会遇到一些电压不平衡的情况。如果对这方面异常认识不足,往往会因为电压不平衡而误认为接地情况者,找不到问题之所在,做了很多无用功,另一方面也可能因为未能及时找到接地点,而引起事故扩大。     

35KV干式电压互感器试验探讨

大庆油田35kV电网系统分布面广,在整个油田电网中具有非常重要的地位。为了监视每相对地的绝缘情况以及用于测量、计量、保护等,母线上一般装设有电压互感器（PT）,以便为上一级变压器的后备保护、35kV线路保护及测量、计量提供电压量,因此电压互感器是电力系统中供测量和保护用的重要设备。保证电压互感器的平稳运行在电网的管理工作中显得特别重要。     

一起母线电压互感器高压熔断器故障原因分析及措施

本文分析了某110kV变电站35kV母线电压互感器高压侧熔断器熔断的各种原因，提出减少其非正常熔断次数的措施。     

阻燃导热型硅橡胶绝缘材料在电力系统中的应用

0引言 目前,变电站设备中高压部分大多是裸露的,因为小动物引起设备短路的情况屡见不鲜,特别是10kV、35kV电压等级的母排、开关柜、电抗器等,     

微机式母线保护装置的设计

本文主要论述了适用于35kV及以上电压等级的母线保护系统,包括单母线、双母线、单母线分段、双母线单分段分段及一个半断路器等多种接线型式的母线保护原理和设计思路,并简单阐述了当前电力系统母线保护的主要特征。     

某电厂220kV站Ⅰ、Ⅱ母PT二次电压长期并列运行原因分析与解决办法

在220kV双母线接线的变电站中,为了提高电压切换回路的可靠性,本文根据某电厂220kV变电站电压并列柜上的一起装置异常现象,充分分析电压切换回路的原理和实现,并从安全的角度对相关回路进行了改进,消除了电压回路存在的隐患.     

基于电压串联加法的1000kV国家工频电压计量标准

国家高电压计量站使用了特殊设计的准确度达0.01级的1000kV串联式标准电压互感器成功地进行了1000kV工频电压加法试验,比值差和相位差测量不确定度均小于等于2×10^-5和0.06′。所得量值与800kV电容式工频电压比例标准装置测量结果比对,比值差的最大偏差为2.7×10^-5,相位差的最大偏差为0.11′,均没有超出双方的90%置信概率区间。     

Analytical closed-form investigation of pwm inverter induction motor drive performance under dc bus voltage pulsation

The voltage unbalance conditions at the input rectifier stage of the AC?DC?AC rectifier-inverter fed induction motor drive is analysed. This unbalance can cause significant voltage harmonic of twice the line frequency 2f1 in the DC bus. This voltage ripple can have a degrading effect on the induction-machine performance characteristics. The authors present an analytical closed-form mathematical model and analysis of the impact of DC bus ripple voltage of the three-phase voltage source inverter with the space-vector PWM on the induction machine phase voltages, currents and torque pulsations. The analytical expressions for the voltage and current space vectors as a function of the DC bus voltage pulsation are derived. Using superposition, the separate parts of the motor currents can be determined. From the current space vectors, the torque behaviour is estimated, again as a function of DC link voltage pulsation. Next, it is shown that the DC link voltage ripple components may cause large torque pulsation. The proposed analytical method is based on the mixed p?z approach, enabling presentation of the results in lucid and closed form. To verify the effectiveness of the proposed analytical model, experimental results based on laboratory setup were obtained.     

一种线性保护输入的恒压LED驱动电源设计

采用对母线电压进行反馈调节的恒压控制方式,设计研究了一种新型高压(260AC)线性保护输入LED驱动电路.利用LD7591GS芯片控制的脉冲宽度调制(PWM)电路和外围光耦电压反馈电路以及LNK564芯片控制的线性隔离变换电路,通过对驱动电路拓扑结构进行研究设计,并对变压器参数进行优化,实现了电压反馈的线性保护输入LED驱动电源设计.实验结果表明,采用外围电压反馈方式电路和线性隔离保护电路调整的LED驱动电源电路具有较好的安全稳定特性和低纹波PWM输出波形,并具有高转化效率,良好的抗电磁干扰性能和稳定的恒压功能.     

基于改进型两次平衡对检法的感应分压器自校准方法

介绍了参考电势变压器和指零仪变压器设计原理,分析了屏蔽间泄漏对测量结果的影响;对常规两次平衡参考电势对检法进行了改进,使零平衡和段平衡测量过程中,参考电势和测差电路均可实现等电位保护;对自校准方法进行了推导,校准结果仅与段平衡和零平衡时锁相放大器测量的电压差值相关,与参考电势变压器、指零仪变压器、辅助变压器等的误差无关,屏蔽间泄漏的影响也得到消除。对1kV感应分压器进行了校准实验,并对校准结果进行了测量不确定度分析,其相对扩展不确定度的评估结果为5.4×10^-8(k=2)。     

一种基于三端口网络的互感器电压串联加法

1954年Zin E和Forger K成功研究出互感器串并联电压加法线路;1988年国家高电压计量站成功研究出互感器双边串联电压加法线路,2006年使用串联型电压互感器进行双边电压加法,2008年试验电压达到1 000/■kV,电压比不确定度不大于4×10^-5(P=95%)。要进一步减小电压比的不确定度,需要最大限度地消除串联型电压互感器的屏蔽误差以及邻近干扰误差。除了设计电磁屏蔽更完善的串联型电压互感器外,还可以使用三端口网络理论实施电压加法,通过三端口网络的响应叠加性,使得在加法过程中的屏蔽误差和邻近干扰误差很大程度上得到补偿。2013年使用广东电网电力科学研究院的500 kV工频电压比例自校系统装置进行了验证试验。与1988年数据相比,110/■kV电压下的屏蔽误差从18×10^-6减小到1.5×10^-6,与2006年数据相比,500/■kV电压比例不确定度从15×10^-6减小到7×10^-6(P=95%)。     

A highly accurate, hand-held clamp-on current transformer

The design, operation, and performance of a 1000:5 A highly accurate, hand-held, clamp-on-type current transformer are presented. This precision current transformer uses a sensitive magnetic circuit to detect transformer ampere-turn unbalance between the primary and secondary circuits. The unbalance represents an error in the ratio and phase angle of the transformer. The largest of the errors is due to the core magnetization current and magnetic reluctance caused by the cutting of the core material. After sensing the errors, electronic feedback through a magnetic circuit is used to provide an error-correcting current. This reduces the overall errors dramatically. These types of devices are referred to as “active” current transformers because of the use of electronic amplifier and feedback circuits. The device described has a novel feature of an openable, split core. This “clamp-on” capability enables use of the transformer on a bus or cable without the complications or need to open the current-carrying circuit to be measured. Commonly used “clamp-on”-type current transformers generally have uncertainties from about 1 to 5% at full-scale rated current. This paper describes a commercialization of active current transformers having a ratio uncertainty of less than ±0.05% over a current range from full-scale rated to 1% of full-scale. Additionally, this product has a small phase angle which is an important consideration when measuring electric power, energy, and power factor. It is intended to be used by electric utilities, standards laboratories, testing laboratories, and in applications where high measurement accuracy and the split-core, clamp-on feature are attractive considerations     

Electrical breakdown voltage of transformer oil with gas bubbles

Electrical breakdown strength of liquid-gas micro bubble mixtures of transformer oil with sulfur hexafluoride and air for the case of quasi homogeneous gas inclusions distribution and 10% volumetric gas content was experimentally investigated. DC voltage up to 140 kV was applied to a 8 mm gap between hemispherical electrodes. It is shown that transformer oil bubbled with air leads to threshold breakdown voltage decrease by 34% and 19% when bubbled with sulfur hexafluoride. The stabilization effect of sulfur hexafluoride micro bubbles on the value of threshold breakdown voltage is observed.     

Design and performance of a Tesla transformer type relativistic electron beam generator

A relativistic electron beam generator driven by an air core Tesla transformer is described. The Tesla transformer circuit analysis is outlined and computational results are presented for the case when the coaxial water line has finite resistance. The transformer has a coupling coefficient of 0·56 and a step-up ratio of 25. The Tesla transformer can provide 800 kV at the peak of the second half cycle of the secondary output voltage and has been tested up to 600 kV. A 100–200 keV, 15–20 kA electron beam having 150 ns pulse width has been obtained. The beam generator described is being used for the beam injection into a toroidal devicebeta.     

Implementation of a low-power electronic tap-changer in transformers

The criteria for optimal configuration of transformer windings as well as power electronics switches are proposed for the design and implementation of a low-power electronics tap-changer. The aims of this optimisation include minimisation of: 1) number of switches and their voltages and currents, 2) number of taps in the transformer, 3) deviation of the amplitude of voltage compared with the reference voltage in the regulation bus and finally increasing number of voltage steps. The hardware for designing and manufacturing a prototype electronic tap-changer is described. The test results for this prototype are presented which shows the advantages of the proposed tap-changer over a mechanical tap-changer.