Distance protection of EHV long transmission lines considering compensation degree of shunt reactor

This study investigated the feasibility of distance protection in extra-high voltage(EHV) networks. In long-distance transmission lines, the distributed parameter characteristic of the EHV network is obvious. When a fault occurs far away from the measurement site, the measured impedance might not be directly proportional to the fault distance, and the protection domain of distance protection will be decreased. The detailed theory inferred and proven in this paper reveals that this phenomenon is widespread in EHV transmission lines. The results indicate that the protection domain error is greatly reduced by the application of the shunt reactor. Overall, simulation results show that the proposed method is effective for impedance relay, considering different characteristics, different lengths of lines, and compensation degrees.

Bayesian belief-based model for reliability improvement of the digital reactor protection system

The digital reactor protection system(RPS)is one of the most important digital instrumentation and control(I&C)systems utilized in nuclear power plants(NPPs).It ensures a safe reactor trip when the safety-related parameters violate the operational limits and conditions of the reactor.Achieving high reliability and availability of digital RPS is essential to maintaining a high degree of reactor safety and cost savings.The main objective of this study is to develop a general methodology for improving the reliability of the RPS in NPP,based on a Bayesian Belief Network(BBN)model.The structure of BBN models is based on the incorporation of failure probability and downtime of the RPS I&C components.Various architectures with dual-state nodes for the I&C components were developed for reliability-sensitive analysis and availability optimization of the RPS and to demonstrate the effect of I&C components on the failure of the entire system.A reliability framework clarified as a reliability block diagram transformed into a BBN representation was constructed for each architecture to identify which one will fit the required reliability.The results showed that the highest availability obtained using the proposed method was 0.9999998.There are 120 experiments using two common component importance measures that are applied to define the impact of I&C modules,which revealed that some modules are more risky than others and have a larger effect on the failure of the digital RPS.

Reactor protection system testing for the solid fuel thorium molten salt reactor

Safety system testing is one of the most rigorous and time-consuming requirements in the verification and validation process for reactor protection systems(RPSs).This paper presents the development of a test system for the fully digital and field-programmable gate array-based RPS of the solid fuel(SF) thorium-breeding molten salt pebble bed fluoride salt-cooled reactor(TMSR),denoted as the TMSR-SF1 project,developed by the Chinese Academy of Sciences.The test system is applied to the RPS to ensure that it fully meets its designed functions and system specifications.We first introduce the testing principles and methods.Then,the hardware component designs and the software program development of the test system are discussed.Finally,the test process and test results are discussed and summarized.

Lead-Bismuth and Lead as Coolants for Fast Reactors

Fast reactors used lead-bismuth eutectic (LBE) and lead as coolants possess very high level of inherent self-protection and passive safety against severe accident. So, population radiophobia can be overcome. That type of reactors can be simultaneously more safely and more cheaply. As all other coolants, LBE and lead coolant (LC) possess the certain virtues and shortcomings. The presented report includes the comparative analysis of characteristic properties of those coolants, their impact on reactor safety, reliability and operating characteristics. The conclusion is made about promising usage of FRs with these coolants in future NP after the experience in operating of the prototypes of such reactors has been obtained.

基于限流电抗器电压的直流配电网单端量保护

直流配电网故障特性复杂,故障电流上升速度快且峰值大,快速、灵敏的故障识别与线路保护是保障直流配电网安全运行的关键技术之一。为此,针对增设限流电抗器的直流配电网,提出一种利用限流电抗器电压实现高灵敏故障识别的直流配电网单端量保护方案。首先,通过分析含限流电抗器的直流配电网故障特性,明确区内、区外故障时限流电抗器电压的特征差异。其次,研究限流电抗器对故障特性及直流保护的影响机制,提出虚拟补偿策略以增强故障识别的灵敏性。在此基础上,根据线路电压变化率设计保护启动判据,提出基于虚拟补偿的故障识别判据和故障选极判据,并给出完整的保护方案流程。最后,基于PSCAD/EMTDC仿真平台进行大量的仿真测试,结果表明所提保护方案能够实现对直流故障的快速准确判断,无需通信支持,且对过渡电阻、噪声及负荷波动具有较强的耐受能力。

基于限流电抗器电压的柔性直流配电线路单端量保护新方法

柔性直流配电技术的理论研究已经步入成熟阶段,其线路保护方法的不完备成为制约该技术发展的重要因素,尤其是以快速动作为优势的单端量保护,耐高阻能力弱、所需采样率高等问题仍待解决。为解决上述问题,文中通过分析单极对称接线系统发生金属性双极短路故障和经过渡电阻故障时限流电抗器电压特征,利用限流电抗器电压及其负变化率积聚和构造保护判据,据此提出了一种基于限流电抗器电压的柔性直流配电线路单端量保护新方法。仿真结果表明,该方法能在0.5 ms内可靠识别区内故障,且耐受过渡电阻(20Ω)和噪声影响,所需采样率要求低,具有工程实用意义。

基于电流的静止无功补偿装置电容器过电压保护

针对串联电抗器的静止无功补偿装置中电容器两端未安装电压互感器导致不能精准实现电容器过电压保护的问题,提出了一种基于电流的并联电容器谐波过电压保护方法。首先,采集电容器两端的电流,利用傅里叶算法计算各次谐波电流;其次,推导电容器基波、谐波电流与电压的关系,依据所推导公式计算电容器两端各次谐波电压;最后,通过仿真软件对文中推导公式进行验证,并阐述了继电保护装置实现电容器谐波过电压保护的方法。结果证明该方法理论推导与实际仿真结果相符,提高了电容器过电压保护可靠性。

直流换流站高通HP3型交流滤波器电抗器匝间故障监测及保护

直流换流站高通HP3型交流滤波器组中电抗器匝间短路故障事故多发,由于缺乏对此故障的快速监测及保护,导致其匝间短路持续存在3~9 min之久并起火燃烧。匝间短路后电抗器的等值电感会不断减小,由此引起了滤波器电路参数变化并进而引发了滤波器配置的热过负荷保护启动告警,长久故障也引发了次生的电抗器底部支撑绝缘子闪络接地致使滤波器差动保护动作出口跳闸。文中分析了3起典型故障案例,结合C型高通HP3型滤波器电路设计理念及运行特点,解释了有关保护启动及动作的原因。基于匝间短路会导致HP3电路中电阻器上的工频电压、电流会随着匝间短路的不断发展而剧烈增大的特性,提出了一种基于工频电压差动原理的故障监测及保护方法。

磁控型可控并联电抗器控制绕组过电压保护研究

磁控型可控并联电抗器是一种新型的动态无功补偿设备,因其无功容量连续可调且控制方式简单可靠,在高压交流输电领域的应用发展迅速,已经在国内外220kV、400kV、500kV和750kV多个电压等级的交流电网上取得了工程应用。本文作者对其典型结构和工作原理进行分析,对其电磁暂态建模,重点针对其控制绕组故障过电压及其产生的危害进行了研究并开展了仿真测试;提出了控制绕组第一级旁通对过电压保护回路和第二级氧化锌压敏电阻过电压保护回路设计方案,并通过仿真试验进行了验证。试验结果表明,本文作者提出的过电压保护方法能够有效保护磁控型可控并联电抗器控制绕组侧励磁设备的运行安全。

一起阀控保护动作事件分析

通过对青海某750 kV变电站750 kV甲乙Ⅱ线阀控保护装置动作跳开断路器事件的分析,找出750kV甲乙Ⅱ线阀控保护装置动作原因,研究解决阀控保护误动作的方法。通过优化阀控保护装置SV采样数据解析机制,最终解决此问题,并对日后安全稳定运行提出相应建议。

面向电容电流补偿的风电交流线路继电保护分析

为了进一步减弱线路电容电流显著问题,提出了一种面向电容电流补偿的风电交流线路继电保护方案,对风电送出线路新型电容电流调控过程进行分析,并对电抗器接地零序差动保护展开研究。研究结果表明:优化处理会造成差流的明显上升,具备比传统算法更高的灵敏度。能够有效提升电抗器零序差动保护制动效果,制动性增强了数十倍,电抗器零序差动保护灵敏度更高。

堆外核测量系统输出高压纹波测试准确性研究

为解决堆外核测量系统输出高压纹波测试过程极易受到外部环境干扰,导致测试数据波动大、不稳定的问题,基于当前高压纹波测试现状,对高压纹波测试准确性进行研究。从数据仿真、结构设计、信号线缆优化、安全防护与验证、测试流程标准化等五个方面入手,通过总结其他行业高压纹波测试方法和结合堆外核测系统产生高压的频率特点,提出一种基于堆外核测量系统输出高压纹波测试准确性设计方法。利用数据仿真技术计算出符合堆外核测量系统高压纹波测试的隔直滤波电容容值,优化整个高压纹波测试外部环境以减少外部电磁干扰。通过验证测试环境的安全性、可靠性以及制定相关测试标准,确保堆外核测量系统输出高压纹波测试的准确性。该研究能够有效提升堆外核测量系统中输出高压纹波测试的准确性,解决了现存问题。

霞浦核电一回路主泵旁通流量函数优化

反应堆一回路冷却剂流量是重要保护参数。霞浦核电钠冷快堆机组一回路冷却剂流量通过主泵旁通流量计测得流量计算得出。本文介绍了一回路主泵旁通流量试验和数据收集过程,采取通道交叉比较方式对数据进行对比,对旁通流量计二次仪表进行调校,采集符合偏差要求的数据拟合出旁通流量-总流量函数关系,并对拟合函数的偏差、触发报警和停堆的裕量进行计算。优化后的函数满足偏差要求,不会导致报警和停堆误触发。

核电厂反应堆保护系统动态功能测试方法设计与实现

为解决传统的反应堆保护系统功能测试中未测试信号滤波控制环节的问题,设计了反应堆保护系统的动态功能测试方法。在逻辑功能块源头注入动态信号并监视功能块的动态输出,同时在仿真软件中对逻辑功能块建模并施加相同的动态信号,确认实测结果与仿真结果的一致性。实施上述测试方案,发现测试结果与建模仿真结果的符合度较好,可以应用于反应堆保护系统的功能验证。

一起死区故障导致35 kV母差保护动作案例分析

介绍了在AVC切除电抗器过程中,发生的一起35 kV母差保护动作事件,导致35 kVⅡ段母线上所有开关全部跳闸。根据现场采集情况,分析了开关跳闸原因,同时对预控措施做了阐述。

反应堆压力容器组装现场大直径环焊缝射线检验

介绍反应堆容器筒体环焊缝现场射线检测时机、射线源放置、透照厚度测定、透照前布置、屏蔽防护等工艺的选择方法,通过保护罩等专用工装在保证射线透照效果的同时确保施工人员安全,高效率完成焊缝射线检验,保证施工进度。

The protective performance of a molten salt frozen wall in the process of fluoride volatility of uranium

The fluoride volatility method (FVM) is a technique tailored to separate uranium from fuel salt of molten salt reactors. A key challenge in R&D of the FVM is corrosion due to the presence of molten salt and corrosive gases at high temperature. In this work, a frozen-wall technique was proposed to produce a physical barrier between construction materials and corrosive reactants. The protective performance of the frozen wall against molten salt was assessed using FLiNaK molten salt with introduced fluorine gas, which was regarded as a simulation of the FVM process. SS304, SS316L, Inconel 600 and graphite were chosen as the test samples. The extent of corrosion was characterized by an analysis of weight loss and scanning electron microscope studies. All four test samples suffered severe corrosion in the molten salt phase with the corrosion resistance as: Inconel 600>SS316L>graphite>SS304. The presence of the frozen wall could protect materials against corrosion by molten salt and corrosive gases, and compared with materials exposed to molten salt, the corrosion rates of materials protected by the frozen wall were decreased by at least one order of magnitude.

Corrosion of candidate materials for supercritical water-cooled reactor

Supercritical water reactor(SCWR) was proposed as a GenerationⅣconcept for building large capacity nuclear power plants.Comparing with the present GenerationⅡandⅢlight water reactors,SCWR possesses great advantages of 10%higher efficiency,simpler system design,better sustainability,and so on. However,the selection of materials for fuel cladding and reactor internals of SCWR is facing a great challenge. Corrosion in supercritical steam is of the first important issue to be solved to meet the stringent requirement of the reactor internal components.Corrosion screening tests were conducted on candidate materials for nuclear fuel cladding and reactor internals of supercritical water reactor(SCWR) in static and re-circulating autoclave at the temperatures of 550,600 and 650℃,pressure of about 25 MPa,deaerated or saturated dissolved hydrogen(STP). Nickel base alloy type Hastelloy C276,austenitic stainless steels type 304NG,AL-6XN,HR3C.NF709 and SAVE 25,ferritic/martensitic(F/M) steel type P92,P122 and 410,and oxide dispersion strengthened steel MA 956,are tested.This paper presents corrosion rate,and focuses on the formation and breakdown of corrosion oxide film,and proposes the future trend for the development of SCWR internal structure materials.

海上风电交流送出线路继电保护优化设计

针对海上风电运行环境恶劣、平台面积资源有限以及电缆线路电容电流显著等问题,提出一种适用于海上风电送出线路的高压线路保护与电抗器保护一体化设计的新方案。首先,将输电线路和电抗器视为一个电气设备,设计了集成优化整体方案,避免了传统的电抗器支路电流的迭代计算。然后,对比研究了传统差动和行波差动对电缆线路电容电流的补偿效果,提出了线路保护优化处理技术。通过引入更为适合的线路零序电流作为电抗器零序差动的制动电流,提出了电抗器保护功能优化策略。最后,仿真实验验证了所提的优化处理技术能够提高海缆线路差动保护和电抗器零序差动保护的灵敏性和可靠性。

基于微分域电流过零点偏移特征的电抗器匝间保护新方法

以中性点不带小电抗的高压并联电抗器为研究对象,在分析电抗器空投励磁涌流特征的基础上,指出了并联电抗器不带中性点小电抗时涌流会更加严重,是引起匝间保护误动的主要原因。分析了并联电抗器空投饱和的机理,指出了电抗器绕组磁通饱和后微分域相电流过零点前后采样峰值间距会发生偏移,在此基础上提出一种基于微分域电流过零点偏移特征的电抗器匝间保护新方法。利用工频特征下相电流过零点前后峰值间距与微分域相电流过零点前后采样峰值间距的偏移程度,结合相电流线性区内各时刻电感的均方根值与额定电感之间的特征关系来识别电抗器空投饱和与匝间故障,若识别为电抗器空投饱和则闭锁匝间保护,若识别为匝间故障则经短延时开放匝间保护。仿真结果验证了所提方法的正确性和有效性。