New protection method for HVDC lines including cables

For the third project of the Hokkaido-Honshu HVDC Link in Japan, called the HVDC Link III project (rated at 250 kVDC-1200 A-300 MW), we developed an HVDC transmission line protection method based on a new working principle that allows high-speed and highly sensitive detection of faults, enhancing reliability in the supply of electric power. In general, increasing the sensitivity of relays will lead to an increased likelihood of undesired operation whereas lowering the sensitivity will impair the responsiveness of the relays. Our proposed method meets these apparently incompatible requirements very well. Basically classified as a differential scheme, the HVDC transmission line protection method compensates for a charging and discharging current that flows through the line-to-ground capacitance at times of voltage variations caused by a line fault or by the operation of DC power systems. The developed protection method is also characterized in that it uses current changes induced by voltage variations to restrain the operation of a relay. This configuration has made the proposed method far superior in responsiveness and sensitivity to the conventional protection method. A simulation using an EMTP (Electro-Magnetic Transients Program) was conducted on this method. Developed relay equipment embodying the new protection method was subjected to various verification tests, where this equipment was connected to a power system simulator, before being delivered to the HVDC Link III facility     

异地多端电力系统实时闭环仿真测试系统

介绍一种由位于异地的多个仿真子系统构成的电力系统实时仿真测试系统,该系统采用电磁暂态建模方法,通过基于全球定位系统（GPS）的同步计算技术,实现了精确的异地同步仿真计算。介绍了仿真系统的硬件、软件和实时仿真的计算过程,仿真系统在实时仿真测试过程中通过通信交换异地保护动作信息,修正仿真网络拓扑,实现严格的闭环仿真测试。该系统适用于对变电站的成套线路主保护等装置进行实时闭环测试。     

数模混合实时仿真系统及其在特高压交直流电网研究中的应用

介绍了国家电网仿真中心数模混合式实时仿真系统的结构、仿真试验流程及其在特高压交直流混合电网仿真研究中的应用。该系统包括相应的数字模型、物理模拟装置及接口设备,其中高压直流输电模拟系统模型包含与实际直流输电系统特性相近的仿真装置,且具有与实际直流工程相同的控制保护装置。文章阐述了对原系统的等值化简、确定系统模拟比、建立仿真试验系统模型等多个环节的处理过程及相关原则。以金沙江一期及锦屏送出特高压直流工程实时仿真研究项目为例,给出了数模混合实时仿真系统的试验结果并与离线计算结果进行了比较分析,2者基本一致。仿真系统试验结果可为特高压交直流混合电网的规划提供技术参考。     

宁东—山东±660kV直流输电示范工程二次系统实时仿真试验及关键问题对策

宁东—山东±660 kV直流输电示范工程是我国第1条660 kV电压等级的直流输电工程。该工程的成套设计由我国自主独立完成,是直流工程国产化的典范。为对其直流控制保护设备的整体功能及性能进行检验,并进一步校核成套设计成果的正确性,专门开展了二次系统实时仿真试验工作。对试验的整体情况进行了介绍,重点对试验中发现的关键技术问题及其解决策略、验证结果进行了阐述。二次系统实时仿真试验为宁东工程的现场调试工作和顺利投产奠定了坚实的基础。     

含多回物理直流仿真装置的大电网数模混合仿真建模及研究

为了对特高压交直流复杂电网进行仿真研究,采用基于输电线贝瑞隆模型的功率连接接口技术,连接全数字实时仿真装置HYPERSIM和高压物理直流仿真装置,建立了相应的数模混合仿真系统平台。仿真试验基于2015水平年特高压规划电网,以华东直流多落点地区为研究对象,搭建了包含16回直流输电系统的模型,其中2回为物理直流仿真装置的大规模数模混合仿真试验模型。试验结果表明,华东直流多落点地区发生的交流系统短路故障,会引起多回落点华东直流发生换相失败,但不会发生连续的换相失败并进而闭锁,系统能够保持稳定。仿真结果表明物理直流仿真装置对数字侧故障响应正确,验证了数模混合仿真研究的有效性。     

Distance relay application testing using a digital simulator

This paper reports on power transmission distance relay application testing using simulated transient waveforms. Power system modeling and test procedures using modern digital simulators are presented. An extensive study of five commercial relays, comparing their application for a 345 kV transmission line, is carried out by performing thousands of one-terminal and synchronized two-terminal transient tests. The digital simulation approach has proved to be an efficient technique. This paper presents a methodology for evaluating distance relay transient performance based on extensive laboratory testing. Important issues regarding application testing are also addressed and investigated in this paper     

Effects of VSC based HVDC system on distance protection of transmission lines

The priority to reactive power contribution from the Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) connection to support the grid during faults as suggested by the modern Network Code (NC) for HVDC affects the distance protection of transmission lines. Moreover, suppressing the negative sequence current during an unbalanced condition also interferes with the proper operation of the distance relays. This is because the current contribution from the converter is limited in magnitude and modified in the waveform in order to protect the power electronic devices during the fault in comparison to the synchronous generator fault current characteristics. This paper discusses the cause as well as the severity of the problems faced by the distance protection of transmission lines connected to the VSC based HVDC system by analyzing the apparent impedance analytically and in the simulation. The response of the relay to balanced and unbalanced faults lying on transmission lines is investigated. It is shown that the VSC limited reactive support and suppressed negative sequence current affect fault detection, forcing the relay to malfunction. The results of this paper can be used as a reference for understanding the effects of VSC-HVDC system on the operation of the distance protection during faults.     

继电保护测试用小型化实时数字仿真器研究

详细介绍了基于ＤＳＰ和ＰＣ机研制而成的专用于继电保护全面 电力系统实时数字仿真器,介绍了这类仿真器的性能要求,描述了该仿真器的软、硬件的实现。介绍了该仿真器的功能如各故障条件下电力系统实时仿真谐波发生器、故障波形回放、振荡模拟以及各种继电器测试。该仿真器体积小,操作方便,可广泛适用于继电保护生产厂家、实验室、电厂、变电站等场所测试种类继电保护装置。     

基于面向对象技术的微机保护仿真

结合电力系统仿真技术的新发展,论述了在变电站仿真器中实现微机保护仿真的必要性,并提出了基于面向对象技术的微机保护仿真的解决方案。具体实现微机保护仿真过程中采用了模块化的编程思想,把微机保护中共有的选相模块、功率方向模块、距离测量模块和重合闸模块都分离出来做成基本保护模块,其它的保护模块可以直接调用这些基本保护模块,从而提高了微机保护仿真效率,具体分析了在多线程编环境中,应该注意的问题和解决方法。     

利用混合实时仿真器测试HVDC控制与保护

介绍使用实时数字仿真器ＲＴＤＳ对ＨＶＤＣ控制和保护系统进行测试。为获得高精度的阀触发脉冲和高频下的仿真性能,采用了先进的混合ＨＶＤＣ实时仿真器。其中,ＨＶＤＣ换流器采用传统的物理模拟装置,直流系统和并联的复杂交流系统均采用实时纯数字仿真,由ＲＴＤＳ仿真器实现。该混合实时仿真器被选择用于中国天－广ＨＶＤＣ工程。基于ＨＶＤＣ控制和保护系统的测试,文中给出了新的混合实时仿真器的结构实现方法和性能校验结果     

Modeling of the Hydro-Quebec-New England HVDC system and digitalcontrols with EMTP

The commissioning of the Quebec-New England multiterminal DC transmission system underscores the increasing need to develop numerical models for simulation purposes. The modern microprocessor-based HVDC (high-voltage direct-current) converter controls used in this scheme make the modeling a real challenge since the Electromagnetic Transient Program (EMTP), usually employed for simulation purposes, and Transient Analysis of Control Systems (TACS) were designed to simulate analog, not digital controls. Details on the modeling of digital controls with a modified EMTP version are given. Some comparisons with HVDC (high-voltage direct current) simulator results which show good agreement between the two power system analysis tools are presented. A case that is validated with field test results is also included     

Design and evaluation of a circulating current differential relaytest system

This paper describes how an EMTP-based simulator can be used in conjunction with a relay test set to type-test a protection relay operating within a circulating current differential protection scheme. The combination of a simulator and a test-set is designed to replace a high power synthetic test plant that has been used for more than 30 years for type and approval testing of differential protection relays. The paper includes results that describe the operating performance of the new test system, on both internal and external faults, and these are compared with experimental results obtained from an identical set of tests on the synthetic test plant     

Discover relay design and application problems usingpseudo-transient tests

The authors describe how pseudo-transient tests using commercially available instruments have revealed several relay design problems and application limitations. The test method is briefly described, and the results of several series of tests are discussed as examples of its application. The method is not suitable for fully assessing the performance of relays. Its limitations are discussed. In series compensated transmission lines, or in EHV cable circuits (with high shunt capacitance), where power system signals have a large proportion of nonfundamental frequency components, pseudo-transient tests may be of limited use. Even in such cases, depending on the design of the relay input filters, pseudo-transient tests may provide useful benchmark test results for future routine maintenance tests     

A new PMU based power swing detector to prevent mal-operation of distance relay

In conventional transmission line protection, a distance relay is used to provide the primary as well as remote backup protection. The voltage and current phasors measurement needed by the distance relay for determining the impedance may be affected by the power disturbances such as power swing. Consequently, this power swing may cause mal-operation of Zone three distance relays which in turn may affect on the reliability of the whole protective scheme. To mitigate these effects and hence improve the relay reliability, this work proposes a new real-time power swing detector using phasor measurement units for blinding the distance relay only during this transient disturbance. However, this developed detector will not block relay when the power swing accompanied with faults. To validate the present work, the performance of developed enhanced distance relay is tested by signals generated by Simulink/MATLAB simulator under different conditions. The test results show that this proposed scheme provides good discrimination between the transient currents and the fault current which in turn it may contribute in enhancing the reliability of Distance relay.     

Real-time digital simulator with digital/analog conversioninterface for testing power instruments

The need for real-time simulation stems from the fact that in many practical situations it is desirable to analyze the dynamic behavior of a large power system with advanced equipment that has complex and high-speed performance. Analog simulators are effective, however they impose serious limitations on the size of the system that is being modeled. The authors have studied and developed a real-time digital simulator using a hypercube computer, and realized real-time performance available for the analysis of large power systems. As the second step of the study, they developed a digital/analog conversion interface for testing actual power instruments. The interface exchanges the variables of fundamental frequency domain in the real-time digital simulator, and the variables of exact time domain in the analog equipment connected to the simulator. In this paper, the authors describe the detail of the digital/analog conversion interface of the real-time digital simulator for testing advanced power instruments. Its conversion algorithm, system configuration of the simulator with the interface, and experimental results are also presented     

IEC 61850数字化保护动模测试系统设计与实现

IEC 61850标准的应用给变电站自动化系统带来了重大变革。在此类变电站中,保护装置可以直接从电子式互感器处获取所需的电流、电压数字量信息,并向智能开关控制器发送数字化跳闸命令。这种数字化保护与传统的微机型保护在硬件结构和信号处理方面都存在差异,传统的保护测试方法将不再适用。文章分析了基于IEC 61850的数字化保护装置的测试要求,提出通过对传统的物理模拟系统进行升级改造,建立符合要求的测试系统。根据这一思路,该新型测试系统在山东大学电力系统动态模拟实验室的基础上开发而成。初步试验结果表明,测试平台能够提供所需要的二次接口特征和测试环境,可以对不同种类的IEC 61850保护装置进行动模测试。     

新一代微机继电保护测试仪及其基本性能

为微机型继电保护装置和安全自动装置测试的需要，以M2000为例，详细介绍了基于DSP、大功率开关放大器和PC机研制而成的新一代微机型继电保护测试仪，介绍了它的基本性能，描述了该仿真器软、硬件的实现，以及仿真器的功能，如电力系统实时仿真、谐波发生器、故障波形成回放、系统振荡模拟、各种类型的继电器测试。该测试仪体积小、重量轻、操作方便，可广泛适用于继电保护生产厂家、实验室、电厂、变电站等场所测试各类继电保护装置。     

Extensive evaluation of high performance protection relays for theHydro-Quebec series compensated network

This paper reports on an extensive study to compare the performance of 8 preselected high performance power line protection systems on the Hydro-Quebec series compensated network. The paper first presents an evaluation of the commissioning aspects and manufacturing quality of the tested relays. It then describes the simulated network, the relay testing procedure, and the laboratory test results obtained on a modern real time power system simulator. Published results of relay performance on series compensated lines are scarce and this paper provides valuable information for utility protection engineers. A total of 115,000 network disturbances were simulated and recorded on 20 different 735 kV lines; fractional test results for 84,030 cases are presented in the paper. The approach using real time power system simulation proved to be an efficient technique for evaluating protection relay performance. The laboratory test results demonstrated that the two best protection principles to be applied on the Hydro-Quebec series compensated network are those based on current differential and segregated phase comparison. The analysis does not take into account telecommunication requirements or other external constraints     

高压直流无接地极运行实现方法

接地极为直流输电系统大地回线运行方式提供电流回路,随着直流输电通道的密集增加,由接地极入地电流引起的油气管网腐蚀、变压器偏磁等问题逐渐增多,严重时将影响电网正常运行方式。文中提出了使用站内接地网代替接地极,直流系统以无接地极方式运行的方案,主要通过直流的控制和保护逻辑来实现。以南方电网±800kV普侨特高压直流工程的实际应用为例,分析了高压直流无接地极运行方案的关键技术难点,设计了通过控制保护核心逻辑修改来实现无接地极运行的方法,并利用实时数字仿真(RTDS)系统对方案进行了仿真验证。改进后的控制保护逻辑已在实际工程实施,效果良好。     

三广直流工程融冰运行方式仿真试验

三广直流工程的直流线路必须考虑合适的防冰对策。文章借助于实时数字仿真器与直流控制保护仿真系统模拟了三广直流工程的各种运行方式,提出了采用一极功率正送、另一极功率反送的融冰运行方式。该融冰运行方式不需要改动主接线方式,也无需修改直流控制保护系统的软硬件系统。仿真结果表明,该运行方式可在与交流系统交换有功功率较小的情况下达到融冰的效果,符合冬季调度方式的要求。