35kV电子式电流互感器的研究

基于小铁心电流传感器LPCT和空心线圈原理的35 kV电子式电流互感器具有测量精度高、动态范围宽等优点,与传统的电磁式电流互感器相比有着明显的优势。文中分析了35 kV电子式电流互感器的测量用LPCT传感器和保护用PCB空心线圈电流传感器的工作原理及影响电子式电流互感器测量准确度的主要因素;采用有限元法对电子式电流互感器的电场进行仿真计算,优化了互感器的电场结构。在理论分析基础上,研制了一台35 kV电子式电流互感器,给出了准确度测试。测试结果表明,设计的35 kV电子式电流互感器符合GB/T 20840.8—2007要求,满足电力系统测量准确度0.2级和保护准确度5P要求。     

中压电子式电流互感器Rogowski线圈的研究与设计

在分析电子式电流互感器工作原理、技术特点的基础上,设计了作为电子式电流互感器传感头的Rogowski线圈并制作了样机,对线圈的骨架材料、截面、抗干扰和温度效应进行了分析.再对圆形截面骨架和矩形截面骨架及其Rogowski线圈进行了试验比较,并得出最优结论.其与调理单元配套组成电子式电流互感器,通过一个线圈同时完成测量和保护功能,并通过了型式试验.     

基于低功率线圈的高压无源电子式电流互感器研制

针对当前电子式电流互感器工程应用中存在的问题,研制了一种基于低功率线圈的高压无源电子式电流互感器,并完成电子式电流互感器用低功率测量线圈、低功率保护线圈及远端模块等各部分设计与制造,弥补了传统罗氏线圈作为保护电流传感器所存在的固有缺陷。同时,针对电子式电流互感器制造过程中各个环节存在的主要问题,介绍了设计思路和解决方案,并建立试验条件,对研制的1台110 k V样机进行了室温条件下的准确度进行了测试,试验验证了低功率线圈作为电子式电流互感器保护电流传感器的可行性。     

断路器中的光供电式空心电流互感器的设计及应用

1引言在电力系统中,互感器、断路器这两种装置一般是由不同的厂家设计和制造,传统的铁心电流互感器体积大而笨重,从结构、绝缘方面而言,两者也无法组合在一起。电子式电流互感器的出现将有可能结束这一局面。如果将体积小、精度高的电子式电流互感器与断路器合二为一,将大大地减小设备的总尺寸,且成本有所降低。根据IEC标准,从测量原理分类,电子式电流互感器包含了光学电流互感器、空心电流互感器(又称为Rogowski线圈)及低功率型电流互感器3种。早在20世纪80年代初,国外就有学者从事基于空心线圈的电子式电流互感器在中压开关中的运用研究,但由于相关技术的限制,空心线圈一般用来做保护通道的测量或者是大电流(额定电流为数百安培以上)的计量通道的测量。随着技术的发展,特别是基于PCB空心线圈新结构的出现,使得测量准确度大大提高,在数十安培的额定电流系统中运用同一个空心线圈作为传感头实现计量和保护的双重功能已经成为可能。笔者介绍的应用于35kV断路器μ0NhRaμ0N2hRaM=2πlnRi;L=2πlnRi=N.M图2空心线圈原理图IEC60044—《8ElectronicCurrentTransformer》标准,对额定电流20...     

空心线圈模拟积分器时间常数定量分析

采用空心线圈的保护用电子式电流互感器,积分器时间常数是影响其稳态与暂态准确度的关键因素。从模拟积分器传递函数入手,分析影响互感器采集系统准确度的多种因素,获取采用空心线圈的保护用电子式电流互感器积分器积分时间常数的定量选取方法,并通过试验验证了该方法的合理性。     

应用电子式电流互感器的变压器差动保护研究

电磁式电流互感器在电力系统故障情况下可能发生饱和，常导致继电保护装置误动或拒动。利用电子式电流互感器无饱和的特点，在动模试验环境下，研究了应用电子式电流互感器的变压器差动保护性能，指出电子式电流互感器采用空心线圈，没有饱和现象，可正确反映故障情况下各次谐波含量，提高变压器保护区外故障时动作的安全性、区内故障时动作的可靠性以及基于谐波制动原理的差动保护动作速度。结合实际应用中的问题，指出GPS硬件时钟同步法是解决数据同步采样问题的优选方案，并对应用电子式互感器的差动保护新原理的研究进行了简要探讨。     

应用电子式电流互感器的变压器差动保护研究

电磁式电流互感器在电力系统故障情况下可能发生饱和，常导致继电保护装置误动或拒动。利用电子式电流互感器无饱和的特点，在动模试验环境下，研究了应用电子式电流互感器的变压器差动保护性能，指出电子式电流互感器采用空心线圈，没有饱和现象，可正确反映故障情况下各次谐波含量，提高变压器保护区外故障时动作的安全性、区内故障时动作的可靠性以及基于谐波制动原理的差动保护动作速度。结合实际应用中的问题，指出GPS硬件时钟同步法是解决数据同步采样问题的优选方案，并对应用电子式互感器的差动保护新原理的研究进行了简要探讨。     

PCB空心线圈电流传感器的暂态特性

在电流测量中,PCB空心线圈具有很好的测量准确度和参数一致性。在模拟积分器中,T形积分器具有很好的低频噪声抑制能力。为此,提出了一种基于PCB空心线圈和T形积分器的电子式电流传感器,建立了该传感器的传递函数模型和短路电流全偏移时的暂态特性模型。重点分析了其对电力系统暂态电流的测量性能,对影响暂态特性的参数进行了数学分析,这为传感器的动态性能优化设计提供了一种分析方法。对传感器样机进行了动模试验,和分流器的输出信号相比,两者波形吻合较好,峰值瞬时误差在±1%左右。该试验结果表明,PCB空心线圈电流传感器具备准确反应电力系统故障电流暂态过程的能力,满足电力系统对电流测量和保护的需求。     

基于RTDS的空心线圈电流互感器建模技术研究

描述空心线圈电子式电流互感器的数学模型,主要描述对象是传感头单元、模拟信号处理单元中的积分放大环节和相位补偿环节。基于电力系统实时数字仿真装置RTDS,在自定义建模功能模块CBuilder中依据各个主要描述对象的数学模型建立了空心线圈电流互感器自定义元件模型。通过搭建实物测试场景和仿真试验系统,分别对互感器产品以及自定义模型进行稳态和暂态等传变特性检测试验,从而验证空心线圈电流互感器自定义元件模型的正确性和实用性。     

地电位供电型电子式电流互感器的设计

针对目前普遍使用的激光供电型电子式电流互感器存在的问题,研究了一种地电位供电型电子式电流互感器,该互感器采用传统倒立式SF₆的绝缘结构,其主要特点是传感单元位于地电位侧,取消了光供电系统,采用空心线圈作为计量、保护的传感单元,将调制的电信号引到低压侧进行解调得到被测电流。文章对温度这一影响空心线圈性能的关键因素进行了仿真计算。研制的地电位供电型电子式电流互感器在国网电力科学研究院进行了型式试验,试验结果表明,研制的电子式电流互感器准确度达到了0.2S级要求。     

Protection and commissioning of multifunction digital transformer relays at medium voltage industrial facilities

The application of multifunction digital relays to protect medium voltage power transformers has become a common industrial practice. Industrial transformers, unlike utility transformers, frequently use neutral grounding resistors to limit ground current during faults to the 200-400-A level on medium voltage systems. This paper will discuss why these types of transformers require sensitive ground differential protection. The paper will also discuss the basics of transformer protection including phasing standards, through-fault withstand capability, differential/fusing/overcurrent protection, slope, current transformer (CT) requirements, and harmonic restraint, and communicating these properly to new digital relays. The rationale for providing transformer overexcitation protection on all major transformers within mill facilities is also addressed. Advancements in digital technology have allowed relay manufacturers to include more and more relay functions within a single hardware platform as well as address increasingly more transformer winding configurations. This has resulted in digital transformer relays requiring an Einstein to set and an Edison to commission. Since there are few Einsteins or Edisons among us, the next generation of transformer relays needs to concentrate on this complexity issue in addition to technical improvements. This paper addresses these issues that the author believes are the major shortcomings of existing digital transformer protective relays.     

The effect of DC offset on current-operated relays

When a fault occurs on a power system, one or more phases will experience DC offset. This DC component, which will decay dependent on the L/R time constant of the system, can produce saturation in the current transformers, as well as the input current transformers of the protective relays sensing the fault. In addition, when the fault current is interrupted, the resulting DC tail can maintain the current above the relay's pickup setting for a time dependent on the current transformer secondary circuit L/R time constant. This paper discusses this phenomenon and how it can affect the operation of two types of current-operated relays     

Applying CTs with digital ground relays

Industrial power distribution system substation transformers and generator step-up transformers in power stations often use resistance-grounded wye secondary windings for medium-voltage power distribution. The purpose of this is to limit damage due to ground-fault currents, while providing sufficient fault current for the operation of ground-fault relaying. The relaying used to protect against ground faults in the system may not provide sufficient protection of the transformer winding against internal faults because the backup ground overcurrent relay in the transformer neutral-to-ground connection must be set to coordinate with downstream relays. In order to protect the winding itself, special relays are utilized. Ground differential protection can be provided by digital overcurrent relays in conjunction with auxiliary ratio matching transformers. Ground differential protection can also be provided in multifunction digital relays. Transformer protection relays may include this feature with one of the schemes used with component relays. If a feeder-protection relay is used on the secondary, in some cases, this may have a ground-directional feature that can be utilized for ground-differential protection     

The phasor combination differential protection for Le-Blanctransformers

The main electrical protection of Le-Blanc connection transformers that supply the single-phase power to the electric railway in Taiwan is the overcurrent protection. This paper presents a more complete protective scheme, the differential protection, for Le-Blanc by phasor combination method. The calculation procedure and the good mismatch results of a practical design example using the parameters of a Le-Blanc transformer of Taiwan Railway Bureau (Tairail) are described in this paper. In addition, using the normal current transformers and electromagnetic type transformer differential relays to completely construct the protective scheme is another merit of this algorithm     

Differential Protection for Special Industrial Transformers

Power transformer differential protection has been used for decades on standard three-phase power transformers. However, special industrial transformers, such as 24-pulse converter transformers, could not typically be protected easily with the standard power transformer differential relays. The main reason is the nonstandard phase angle shift of 24-pulse converter transformers. Such 24-pulse converter transformers are often used in industrial and railway applications. This paper will show that it is possible to provide differential protection for such special transformers by using standard numerical transformer differential protection relays and external interposing current transformers (CTs). However, the external interposing CTs can be designed in a standardized way. This approach will significantly simplify the application of differential protection for special industrial transformers.     

Rogowski线圈的动模实验研究

介绍了基于Rogowsk i线圈传感的电子式电流互感器在与电磁式电流互感器并联运行时的实验结果,并以变压器差动保护为例对两种传感器的保护特性进行了比较分析研究。实验结果表明:在保证传感器绕制工艺和合理选择信号处理电路结构参数的情况下,与电磁式电流互感器相比,基于Rogowsk i线圈原理的电子式电流互感器能准确反映一次侧暂态电流的变化情况,具有无饱和、测量准确、响应速度快的特点,完全满足电力系统的保护和控制对电流信号采样的要求。     

电子式电流互感器应用现状及发展趋势

电流互感器在电力系统的交流电测量、继电保护、电力设备检修控制等相关领域均具有十分重要的地位。目前电磁式电流互感器逐渐暴露绝缘差、抗干扰能力弱等多种缺点,而电子式电流互感器凭借自身绝缘性好、体积小、可数字化等特点有望成为未来电气领域检测电流的主要设备。本文以电子式电流互感器的研究发展现状切入,通过空心线圈电流互感器(即Rogowski线圈式电流互感器)、低功率电流互感器(LPCT)、光学电流互感器展开进行系统论述,重点分析各自的组成结构及工作原理,并对其优缺点进行总结,提出改进之处。在此基础上指出电子式电流互感器在设备供能、环境适应、传感方式等方面所面临的挑战,并从传感机制和传感材料对其未来的发展趋势做出展望。     

基于数据融合的组合结构电子式电流互感器设计

目前电子式电流互感器(electroniccurrenttransformer,ECT)大多数采用单传感器开环结构,对每个环节的精度和可靠性的要求都很高,严重限制了ECT整体性能的提高,影响其实用化。介绍了铁心线圈式低功率电流互感器(lowpowercurrenttransformer,LPCT)和印刷电路板(printedcircuitboard,PCB)空芯线圈电流互感器及其数字积分器,在此基础上设计了一种基于PCB空芯线圈和LPCT的组合结构ECT,该结构具有并联和前馈的特点,结合了这2种互感器的优点。采用数据融合算法来实现高精度测量和提高系统可靠性,并提出了辨别LPCT饱和的新方法。实验和仿真结果表明,该ECT可覆盖较大的电流测量范围,达到IEC60044-8标准中关于测量(幅值误差)、保护(复合误差)和暂态响应(峰值)的准确度要求,能够作为多用途ECT使用。     

A semiconductor H-bridge connection to avoid saturation in current transformers for differential protection

Current transformer saturation can be the cause of misoperation or false tripping in power transformer differential relays during connection transients. To avoid this scenario, the authors propose a solution based on a current transformer flux controller system (CT-FCS). The CT-FCS consists of a controlled semiconductor H-bridge connected to the primary winding of current transformers, allowing the inversion of the currents polarity. Unipolar pulses with high content of DC current are converted into bipolar pulses that reduce or cancel the amount of DC component in current transformer cores. By canceling the DC component, a saturation-free operation can be obtained. The use of this method will allow the selection of current transformers with lower saturation factors and will reduce the size of such devices.     

智能变电站电子式互感器故障分析及建议

电子式互感器是智能电网、数字化变电站的重要设备,其制造、运行及故障检修经验仍然不足。某变电站数字化改造3年后,部分电子式电压互感器二次电压值不稳定,电子式电流互感器二次电流值出现明显偏差。介绍了电子式互感器系统原理、设备结构,分析了设备异常、故障原因,进行了解体研究及实验验证。发现设备参数影响红外测温结果,电压互感器取能线圈短路可造成电压下降,电流互感器并联电阻开路可造成电流激增。最后对电子式互感器的设计制造、质量控制及运行维护提出了几点建议。