Protection system representation in the Electromagnetic TransientsProgram

This paper concerns the addition of the few critical elements of a protection system to the Electromagnetic Transients Program (EMTP), which is one of the most widely used programs for the simulation of transients in power systems. It contains models for almost every major power system component. A protection system consists of instrument transformers, relays, and circuit breakers. Models for current transformers (CTs) and capacitor voltage transformers (CVTs) are developed, validated, and incorporated in the EPRI/DCG EMTP Version 2.0. The user can define the values of the CT and CVT parameters. Total FORTRAN capability has been added to the EMTP; new subroutines and an inbuilt structure to allow the linking of user-defined FORTRAN subroutines with the main EMTP are explained. This capability is necessary to simulate computer relay algorithms. These new features in the EMTP together constitute the critical elements of a protection system. Thus, it is now possible to simulate the dynamic interactions between a power system and a protection system     

级联形态梯度变换及其在继电保护中的应用

介绍了现在应用已较成熟的灰值腐蚀和灰值膨胀运算,由此引出多分辨形态学梯度变换(MMG)的定义;进而在其基础上提出了一种新型的级联多分辨形态梯度变换(SMMG)的概念,SMMG具有很强的奇异信号检测和波形识别能力,作为一种特征提取工具,SMMG能感受并增强信号波形上的微小变化、反映突变的大小.和其它形态学算子一样,它具有SMMG具有表达直观、滤波器设计简单、数据窗短、计算速度快以及变换结果易于识别、对硬件没有过高的要求等优点,因此在继电保护的信号处理中具有良好的应用潜力和实用价值,在现有的微机保护装置中可以直接采用.文中最后给出了其在电力系统继电保护中应用的2个实例,EMTP仿真研究表明:文中提出的相继速动判据具有更高的灵敏度;所提出的基于SMMG的微机线路保护的选相元件能在8ms内正确地识别几乎所有故障情况的故障相别.由SMMG构成的保护元件灵敏度很高,在电力系统高速及超高速保护方面有良好的应用前景及较大的实用价值.     

平行双回线路故障分量电流平衡保护研究

传统的平行双回线路电流平衡保护存在灵敏度低、受过渡电阻影响大等缺点,难以满足高压平行双回线路的要求。该文给出了基于故障分量的电流平衡保护启动判据和选线判据。利用叠加原理和六序故障分量法分析了过渡电阻对选线判据的影响,给出了各种故障情况下两回线故障相故障分量电流幅值之比的表达式。给出了相继动作区故障时的电流平衡保护方案。理论分析和EMTP仿真表明,基于故障分量的选线判据几乎不受过渡电阻和负荷电流的影响,灵敏度得到了提高,可直接应用于目前微机保护装置。     

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。     

电力变压器新型微机保护原理的研究

为了防止二次谐波制动原理的变压器差动保护在内部故障伴随较高二次谐波时延时动作 或拒动，本文提出了一个新原理的微机变压器保护。它在不改变传统变压器差动保护测量电 路形式的基础上，用单片机软件编程加以实现，大量的仿真实验已证明其具有较好的动作特 性。     

配电线路无通道保护研究

针对35 kV及以下中低压配电网中三段式电流保护动作速度慢、快速保护范围有限的缺点,提出了利用单端故障分量的快速保护新原理和构成方案。该保护利用线路对端断路器动作后所造成的本端故障分量的变化来识别保护区内外故障,克服了传统电流保护延时较长的缺点。EMTP仿真结果证明了所提保护的正确性及有效性。     

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     

面向继电保护的全过程系统振荡仿真

提出了一种更加符合电力系统机电暂态过程的全过程系统振荡模式的设计思想。通过对振荡中系统频率的正确理解，提出了利用多项式拟合系统频率变化速度的新思想。系统振荡中的各种关键参数均可设定，可为振荡中各种继电保护装置和安全自动装置的动作行为评估提供足够的典型数据。最后，通过EMTP仿真验证了模型的有效性。     

静止励磁系统故障的数字仿真

励磁系统是发电系统的重要组成部分,应针对其可能的故障形式装设必要的保护.文章首先利用电磁暂态程序(EMTP)建立了静止励磁系统的仿真模型,并在此基础上研究了励磁变压器低压侧单相接地和整流主回路异常时保护测量回路的波形特征.仿真结果表明,当出现上述故障时,转子接地保护测量的取样电压及失磁保护测量的励磁电压都会出现大量的非特征谐波,这一特点可用来改进发变组保护的动作特性.     

A new blocking principle with phase and earth fault detectionduring fast power swings for distance protection

Any sudden change in the configuration or the loading of an electrical network causes power swings between the load concentrations of that network. In order to prevent the distance protection from tripping during such conditions, a power swing blocking device is often utilized. Conventional power swing blocking devices cannot cope with very fast power swings of up to 5 Hz/sec. This paper presents a new power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone. This is demonstrated for extremely fast swings (greater than 5 Hz/sec) and even for two phase operation (during single pole tripping). This new principle is in a form which can be implemented on an existing digital distance protection relay. Results are presented based on extensive simulation studies carried out on a typical 400 kV system, using the Electromagnetic Transient Program (EMTP) software     

Algorithms for locating faults on series compensated lines usingneural network and deterministic methods

This paper investigates a scheme to improve the reach measurement of distance relays and fault locators for series compensated power lines. A deterministic method and a feedforward neural network method have been implemented for online calculation of the voltage across a nonlinear capacitor installation. These techniques are compared and incorporated into a new relaying scheme which is independent of the series capacitor installation, operation of the capacitor protection, and the surrounding power system elements. The proposed scheme is simple and accurate and requires only local voltage and current at the bus. Detailed testing using EMTP has been done to show the benefits of the new adaptive scheme. The results demonstrate the suitability of the techniques for real world applications     

含静止无功补偿器的电力系统混合仿真新算法研究

传统的机电暂态仿真对HVDC和其它FACTS电力电子装置采用准稳态模型,因而不能仿真它们的瞬变电压、电流特性.而电磁暂态仿真程序(例如EMTP)受计算规模的限制,一般要对研究对象的外部电力系统进行等值化简,因此不能反映系统机电暂态过程对电磁暂态过程的影响.本文介绍的混合仿真算法为弥补上述两种方法的不足,对电力网络采用准稳态模型,而对待研究的电力电子装置(例如SVC)使用电磁暂态模型,两种仿真的结合使用了本文发展的考虑系统频率偏移影响的接口技术.本文介绍的混合仿真算法为研究HVDC和FACTS等电力电子装置及其控制系统的动态性能提供了一种有力的工具.     

A new neural networks approach to on-line fault section estimationusing information of protective relays and circuit breakers

This paper proposes a new neural network diagnostic system for online power system fault section estimation using information of relays and circuit breakers. This system has a similar profile of an expert system, but can be constructed much more easily from elemental samples. These samples associate fault section with its primary, local and/or remote protective relays and breakers. The diagnostic system can be applicable to the power system control center for single or multiple fault sections estimation, even in the cases of failure operation of relays and breakers, or error-existent data transmission. The proposed approach has been practically verified by testing on a model power system. The test results, although preliminary, suggest this system can be implemented by various electric utilities with relatively low customization effort     

DYNA-TEST simulator for relay testing. I. Design characteristics

The authors describe a new digital dynamic testing (DYNA-TEST) simulator developed for protection relay applications. This simulator is capable of producing voltage and current transients that correspond to actual fault events in the power systems. Fault transients are generated either by simulating power system faults using an electromagnetic transient program or by replaying records of fault signals captured in substations by digital fault recorders. These signals are used to test protection relays. Such an approach to relay testing represents a major improvement over steady-state testing     

Using TACS functions within EMTP to teach protective relayingfundamentals

The purpose of this discussion is to provide an educational tool for investigating relaying concepts by modeling digital relays using TACS functions within EMTP in a closed-loop manner. Various elements of digital protection systems are identified and organized to generate an systematic approach to modeling the actual hardware of relay systems. Discussion is limited to conventional relaying systems that monitor the vitality of the 60 fit voltages and/or currents. TACS functions for transport delay and pulse generators are used to model dynamics associated with analog to digital conversion and sampling systems. DSP algorithms convert a sequence of sampled data into a sequence of values for magnitude and phase components. A simple example of a time overcurrent relay is developed to demonstrate the techniques to implement relay control in EMTP with TACS and illustrates the kinds of phenomena that can be studied using these techniques     

非线性元件算法研究

本文介绍一种电力系统电磁暂态仿真非线性元件算法.目前在电力系统电磁暂态领域应用最广泛的是EMTP(电磁暂态程序)和EMTDC(直流电磁暂态程序)技术,但是此技术还存在一定的局限性.本文在此技术的基础上提出了一种新的算法,并对非线性元件二极管进行算例证明.新算法为所有非线性元件提供了一种真非线性元件算法,解决了补偿法求解过程中遇到的假非线性元件精度低和拓扑约束的问题,即可求解任意拓扑结构的非线性网络.     

Protection, metering, monitoring, and control of medium-voltage power systems

Traditional practices for industrial and commercial medium-voltage power systems to provide protection, metering, monitoring, control, power quality analysis, disturbance recording, and automation have changed. The new multifunction numerical protection relays using the processing power of the present generation of microprocessors have very high functionality. Many functions can be integrated into one device, allowing new power system problem-solving capabilities while permitting significant cost savings as compared with discrete protective relays, instruments, meters, recorders, and transducers of the past. This paper describes the vast capabilities and recent enhancements of these devices, which will be called intelligent electronic devices in this paper. Included are anecdotes obtained from an installation on a large industrial power system.     

Time coordination method for power system protection byevolutionary algorithm

A typical industrial power network may consist of hundreds of pieces of equipment and even more protection relays to protect the system are required. Each protection relay in the power network needs to be coordinated with the relays protecting the adjacent equipment. The overall protection coordination is, thus, very complicated. A new concept of protection coordination by time is introduced in this paper to formulate all the system relays and system equipment operation into a set of optimization equations and constraints. Its purpose is to search for an optimal protection setting to minimize the system disturbance time as well as the time of interruption of the power supply. An evolutionary algorithm is applied as a constraint satisfaction optimization tool to search for the optimal relay setting. This method can find the best protection relay coordination, which cannot be achieved by traditional methods. This is the most significant achievement of the paper     

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     

Synchronized solution of power electronics system equations usingflexible MODELS component connected to the EMTP

The oscillations from the trapezoidal rule of integration following discontinuity and the one-time-step error from separate EMTP and TACS (or MODELS) simulations are the numerical stability and accuracy problems found in the transient study of power electronics systems using EMTP. This paper presents the technique of the synchronized solution of power electronics system equations. The proposed technique implements efficient and numerically stable approaches to model the switching circuit and control system as a MODELS component. This MODELS component is connected directly to the EMTP to avoid the one-time-step delay. Therefore, the numerical oscillations and one-time-step error in standard EMTP simulation can be eliminated