Educational use of EMTP MODELS for the study of a distance relayingalgorithm for protecting transmission lines

This paper presents the implementation of a distance relaying algorithm using EMTP MODELS, in which we have simplified the procedures of system modeling and distance relaying system by using a single structure of MODELS. The technique presented is based on integrating the modeling of the power system and the protective system in one program module. The purpose of this paper is to provide systematic relaying concepts by modeling a digital relaying system using MODELS functions within EMTP in a closed-loop manner, principally to facilitate and enhance an understanding of the basic concepts of distance relaying of final year undergraduate students/postgraduate students/young engineers who are new to the subject of power system protective relaying. Various elements of digital distance relaying are organized to generate a systematic approach to modeling the actual hardware of digital relaying systems. Case studies relating to the most commonly encountered single phase-to-ground fault and phase-to-phase fault are presented and various fault distances and fault inception angles are considered     

Transient modeling of electromechanical relays

An electromechanical, plunger type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the Type 50 devices and incorporating them into a power system transient analysis. This paper is the second part of a summary report by Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration. (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for plunger type 50 instantaneous overcurrent relays that compare with actual tests performed on the devices on a power system simulator     

Transient modeling of electromechanical relays. Part I: armaturetype overcurrent relay

An electromechanical, armature type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the armature type 50 devices and incorporating them into a power system transient analysis. This paper is the first part of a summary report by the Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for armature type 50 instantaneous overcurrent relays that compares with actual tests performed on the devices on a power system simulator (PSS)     

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     

Modeling and simulation of the power transformer faults and relatedprotective relay behavior

The modeling of power transformer faults and its application to performance evaluation of a commercial digital power transformer relay are the objectives of this study. A new method to build an EMTP/ATP power transformer model is proposed in this paper. Detailed modeling of the transformer relay is also discussed. The transient waveforms generated by ATP under different operating conditions are utilized to evaluate the performance of the transformer relay. The computer simulation results presented in this paper are consistent with the laboratory test results obtained using an analog power system model     

Transients computation for relay testing in real-time

This paper discusses characteristics of a new digital simulator for protection relay testing. The most demanding design requirement is computation of fault transients under the condition of real-time change of power system configuration due to relay operation. This problem is solved using EMTP computational techniques enhanced with novel numerical solutions for dynamic power system configuration change and nonlinear element modeling. An advanced computer architecture is utilized to achieve further optimization of the execution time for the transients computation code. The main advantage of this design is the use of conventional single processor computer architecture in combination with advanced digital signal processors (DSPs). This makes this simulator an off-the-shelf product with all the benefits of commercially available computers priced at a relatively low cost     

Digital protection of transmission lines using block pulse functions

An application of block pulse functions for digital protection of transmission lines is presented. A digital relay algorithm is developed to extract fundamental frequency components. These components are then used to calculate the impedance as seen from the relay location of a transmission line. The method is offline tested using realistic relaying signals of a 230 kV three-phase transmission line, and the results are compared with those of an algorithm based on Haar functions. The proposed algorithm is computationally simple and flexible to use with any sampling frequency.     

Combined fuzzy-logic wavelet-based fault classification technique for power system relaying

This paper presents a new approach to real-time fault classification in power transmission systems using fuzzy-logic-based multicriteria approach. Only the three line currents are utilized to detect fault types such as LG, LL, and LLG, and then to define the faulty line. An online wavelet-based preprocessor stage is used with data window of ten samples (based on 4.5-kHz sampling rate and 50-Hz power frequency). The multicriteria algorithm is developed based on fuzzy sets for the decision-making part of the scheme. Computer simulation has been conducted using EMTP programs. Results are shown and they indicate that this approach can be used as an effective tool for high-speed digital relaying, as the correct detection is achieved in less than half a cycle and that computational burden is much simpler than the recently postulated fault classification techniques.     

Fuzzy logic-based relaying for large power transformer protection

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. The frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. Then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.     

A novel adaptive PMU-based transmission-line relay-design and EMTP simulation results

This paper proposes a novel adaptive relaying scheme based on phasor-measurement units (PMUs) for transmission lines. The proposed adaptive relaying scheme can provide an extremely accurate discrimination between in-zone and out-of-zone faults. Two novel and composite fault discrimination indices in terms of Clarke components of synchronized voltage and current phasors at two ends of a line are derived. A line parameter estimation algorithm is developed and built in the newly designed relay to solve the uncertainty problem of line parameters. The proposed relaying scheme is independent of fault types, fault locations, fault path resistance, fault inception angles, and the variations of source impedance. The tripping decision time of the designed relay is very fast and almost held well within 6 ms for most fault events. All of the EMTP simulation results show that the proposed adaptive relaying scheme provides a high level of dependability and security.     

New digital control and protection equipment using multiprocessor architecture of distributed functions for power system

Control and protection of equipment in power systems generally require a high-information processing capability to cope with today's power system requirements. Then, new digital control and protection equipment have been developed using high-speed and high-precision processors. Essential requirements for the new control and protection equipment are a multiprocessor architecture of distributed functions to retain sufficient computing power (fast and high-precision operations), and flexible and expandable hardware with high reliability. In multiprocessor architecture, it is important to determine how the distributed processors share the functions. By analysis and synthesis of relaying and control processings, we divided them into six processing circuits. This paper proposes a multiprocessor architecture of distributed functions, using 32-bit floating-point and 16-bit microprocessors depending on the computational requirements. In addition a digital filter for fast sampled data is described along with performance of a digital relay.     

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     

Novel microprocessor based negative phase sequence relay and meter

Microprocessor application in relaying and condition monitoring technology is becoming increasingly popular. In this paper, a novel microprocessor based negative phase sequence (NPS) current detector for motor condition monitoring and relaying for motor/generator protection is developed. The proposed meter eliminates the need of a negative phase sequence filter and does not require complicated digital signal processing techniques. Instead it uses a phase sensitive rectifier. A prototype based on Intel's 8085 A microprocessor was built and tested. Complete circuitry, main and interrupt software flowcharts are provided. Results show the proposed NPS relay and meter can provide a high degree of accuracy and satisfactory results.     

Digital protective relaying algorithms and systems — An overview

This paper gives an overview of the digital algorithms and systems for protective relaying. First, digital relaying algorithms are discussed. Classification and categorization of the proposed algorithms are given. The major classes are: transmission line protection, transformer protection, bus protection, and generator protection. The categories correspond to the different schemes used for the signal processing. The discussion of algorithms is concluded by giving some basic results related to the comparison and selection of the algorithms. A particular methodology is proposed if one is to investigate and compare digital algorithms using more elaborate quantitative techniques. The second major topic discussed is related to the digital implementations of the protective relays. Major philosophies used in designing digital relaying systems are outlined. These philosophies include the following design approaches: a centralized relaying system using a minicomputer; a decentralized relaying system where each protection function is implemented using a separate microprocessor; an integrated relaying system where a number of dedicated microprocessors are connected together in a protection system; an integrated substation control and protection system. Finally, expected trends in the areas of algorithm developments and system implementations are indicated.     

方向高频保护负序功率方向元件的非全相运行性能分析

着重分析了负序方向元件在超高压线路中非全相运行时的工作情况，比较了各种电容电流补偿方法对负序方向高频保护元件的影响。EMTP仿真结果表明，线路两侧断线又发生故障时，基于故障分量的负序方向元件可以正确动作。     

A new distance relaying algorithm based on complex differential equation for symmetrical components

This paper presents a new digital impedance measuring technique for transmission lines that combines symmetrical components and the complex differential equation of an equivalent fault loop circuit. The phase voltages and currents at the relaying point are transformed into symmetrical components using Fourier filters of short window length. Depending on fault type, an appropriate fault loop circuit is formed, signals of which are the appropriate symmetrical components, while a parameter of which is the positive sequence impedance being a geometrical measure of the distance from the relaying point to a fault. The impedance, however, is measured very fast by on-line solving the complex differential equation originated for this fault loop circuit. Consequently, this approach combines frequency domain estimation of symmetrical components (accurate filtration) and time domain measurement of positive sequence impedance (high speed response).

The presented method suits well the protection of parallel lines against high-resistance faults occurring very close to the far end of a line. A new method is proposed for detecting high-resistance faults and deciding which line out of two parallel lines actually suffers a fault.

The included EMTP test results demonstrate the efficiency of the proposed relaying algorithm.     

Pilot relaying performance analysis: IEEE committee report

An analysis is conducted of the performance of pilot relay schemes under fault conditions. While it is recognized that this type of investigation can take many directions, the use of relay targets being one such avenue of inquiry, this study concentrates on performance evaluations through the application of fault recorders and sequence-of-event recorders. The specific analog and digital quantities to be monitored to provide for a correct analysis are shown. The many system and equipment phenomena and limitations, external to the pilot relaying terminal, that could affect pilot relaying performance are described. Seven basic pilot relay schemes are discussed, and, for each pilot relay scheme discussed, typical oscillograms are shown for internal and external faults to assist in the proper fault analysis of such pilot systems. Minor variations to the basic scheme are not specifically discussed, but the monitoring and performance analysis of other schemes can be handled using the principles covered     

Development of distributed relaying processor with digitalfiltering of fast sampled data

In order to cope with advanced relaying techniques, a multimicroprocessor-based digital relay was developed. The main features are distributed processing among five processors, 32-b floating-point operations, digital filtering of fast sampled data, and a personal computer based testing tool. Performance tests of this digital relay showed the following characteristics: (1) the error of any relaying element (distance, overcurrent and undervoltage) was less than 1%; (2) operating time was less than 20 ms when the processing interval was 1.67 ms; and (3) a single relaying processor had a computational capacity of six-phase (ground, short×4 steps×3 phases) distance relays based on differential equations, accompanying elements, and a self-diagnosis function in every processing interval     

Interactive relay controlled power system modeling

Four fundamental algorithms that make it possible to simulate numerous types of protective relay systems are identified. The characteristics of these fundamental modules necessary for building an embedded relay model within an EMTP (electromagnetic transient program) are discussed. A directional time overcurrent relay model is used to provide a detailed demonstration of relay model development and to illustrate the utilization of the fundamental modules. The results of using this relay model in a modeled power system reveal the power of this concept to enhance power systems education, applications engineering, and relay design procedures     

暂态仿真在检验保护动作行为中的应用

在对引进美国ＤＯＢＬＥ公司生产的Ｆ２２５０型微机式继电保护测试仪吸收、消化和开发的基础上,成功地实现了将电磁暂态程序（ＥＭＴＰ）模拟系统故障计算出的暂态数字仿真结果和微机故障录波器所记录的数字量故障波形,通过Ｆ２２５０测试仪回放成为模拟波形对保护装置的动作行为进行了分析,为在现场检验保护装置的动作行为提供了一种手段。