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IEEE Region 10 Conference (TENCON)

作者： Sekhar, G. Chandra GMR Inst Technol EEE Dept Rajam Andhra Prades India

ISBN: (纸本)9781509011346

The conversion of existing three phase double circuit transmission line into Six phase transmission line will bridge the gap between power generation and power demand. As the Six Phase system can be considered as two mutually coupled Three Phase Systems, hence the protection scheme applicable for Three Phase Transmission Line will work for Six Phase Transmission system without any change. In this paper the author has developed a complete Logic Based backup protection scheme for six phase transmission system by using negative sequence currents with Simulink platform of MATLAB. As the number of fault combinations in six Phase Transmission are 120, both the main protection and backup protection are complicate. The backup protection must be developed with utmost priority to protect the whole power system. The Proposed protection scheme is simulated for a Three Phase IEEE 9 Bus system and Six Phase Transmission line of Allegheny Power System, USA. This Scheme works for Three Phase System and also for Six Phase System because the Relaying operation is developed on Single Phase operation. The simulation results are presented that the logical relay gives the trip signal of logic 1 for fault and logic 0 for healthy conditions. The main advantage of the scheme is that no hardware is required except the interface for both input and output to Simulink Model.

关键词： Six phase Transmission Three phase transmission Protection negative sequence currents back up protection

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Coordinated strategy between positive- and negative-sequence currents of wind farms for transient stability enhancement of synchronous generators under asymmetrical grid faults

Coordinated strategy between positive- and negative-sequence...

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International Conference on Renewable Power Generation (RPG 2015)

作者： Longfei Wang Wei He Jiabing Hu Ningbo Wang State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China Wind Power Technology Center of Gansu Electric Power Corporation Lanzhou 730050 China

ISBN: (纸本)9781510821415

As the penetration of wind power is growing, it is demanded that wind farms should contribute to maintaining power system stability, for particularly under various grid fault conditions. Highly-penetrated wind farms are able to influence synchronous generators' (SGs') behaviour for transient stability enhancing by injecting the designed positive- and negative-sequence currents, especially when the electric distance between wind farms and SGs is short. In this paper, SG's transient stability during asymmetrical grid faults is the centre of interest. The relationships between SG's rotor swing function and wind turbines injecting currents are analysed based on the mathematical models of unbalanced power system. Coordinated requirements for positive- and negative-currents injection of wind turbines, for the purposes of to enhance transient stability, are proposed during asymmetrical faults. Time domain simulation validates the result.

关键词： Asymmetrical Grid Faults negative sequence currents Positive sequence currents Transient Stability Wind Farms

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Two novel current-based methods for locating earth faults in unearthed ring operating MV networks

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ELECTRIC POWER SYSTEMS RESEARCH 2022年第0期213卷

作者： Zerihun, Tesfaye Amare Treider, Thomas Taxt, Henning Nordevall, Lars B. Haugan, Thomas S. SINTEF Energy Res Trondheim Norway Norwegian Univ Sci & Technol NTNU Trondheim Norway Elvia AS Oslo Norway

Automated fault location plays a key role in improving the reliability of modern power grids-it helps to reduce the power outage time and the number of affected customers. Earth faults in isolated systems are among the fault types that are difficult to detect and locate with a reasonable accuracy, and there has therefore not been a well-established method for detecting and locating such faults in isolated systems. This paper presents two novel current-based methods for locating earth faults in unearthed closed-ring MV networks. The methods are based on the utilisation of sequence components of standard current and voltage measurement at a primary substation and they do not require new devices or measurements in the field. Both methods are tested with a simulation of a network based on data provided by a Norwegian network operator and their prediction performances were investigated considering different scenarios on fault resistance, load asymmetry and measurement errors. Both methods performed well and showed good accuracy. The simulation results are promising and strengthens the prospect of further testing of the methods in real networks and adoption of the methods for a real-world implementation.

关键词： Earth fault location Closed-ring MV network Distribution network Impedance method negative sequence currents Zero sequence currents

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Application of Equivalent negative sequence Current Calculations in Transmission Planning Studies

Application of Equivalent Negative Sequence Current Calculat...

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IEEE SoutheastCon Conference

作者： Walker, Jake E. Ramos, Reynaldo Southern Co Serv Transmiss Planning Stabil & Special Studies Birmingham AL 35243 USA

ISBN: (纸本)9781665476119

This paper discusses incorporation of equivalent negative sequence current (I-2eq) calculations into transmission planning harmonic power flow studies. It includes an assessment of how the focus on I-2eq, instead of fundamental frequency imbalance (I-2), does not necessarily align with generator current imbalance protection schemes. This topic is covered by summarizing the methods of calculating I-2eq described in IEEE Standards C50.12 and C50.13 along with the approach developed by the Electric Power Research Institute. The latter method provides a conservative projection of negative sequence currents during geomagnetic disturbance events, including harmonic effects. Combining these calculations with actual generation field measurement data show that clarification of IEEE Standards C50.12 and C50.13 is needed. The practices of transmission planning and generator protection organizations could be affected by the increasing number of harmonic sources connecting to the bulk electric grid since protection schemes generally do not include harmonic contributions. Therefore, both organizations should be aware of the difference in I-2 and I-2eq when considering the potential increase of harmonic distortion due to grid modernization. Careful consideration needs to be taken to ensure these standards are properly applied.

关键词： generator current imbalance harmonic currents negative sequence currents transmission planning studies

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Synchronous Generator Vulnerability Assessment Against Solar and HEMP MHD-E3 GIC 52

Synchronous Generator Vulnerability Assessment Against Solar...

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52nd North American Power Symposium (NAPS)

作者： Nazir, Moazzam Enslin, Johan H. Clemson Univ Zucker Grad Educ Ctr N Charleston SC 29405 USA

ISBN: (纸本)9781728181929

The solar storm or a high-altitude nuclear detonation leads to geomagnetic disturbance (GMD) that causes the flow of geomagnetically induced current (GIC) in the power systems. The GIC leads to half-cycle saturation of generator step-up (GSU) transformers that causes negative-sequence currents to flow in the generator's stator windings. This in turn leads to excessive rotor vibration, heating and generation fluctuations, thus threatening the grid reliability and resiliency. This paper performs the vulnerability assessment of the most-widely utilized power generation resource i.e. synchronous generators against GIC by performing a detailed harmonic analysis and depicting the resultant mechanical, electrical and thermal repercussions. The simulation is performed in PSCAD/EMTDC for a 13.8kV/120MVA grid-tied synchronous hydro-generator impacted by a GMD. The simulation results highlight the significant threat facing the highly prevalent generation facilities that are largely unprotected against the adverse effects caused by the GMD on power systems.

关键词： Geomagnetically Induced Current Harmonics HEMP MHD-E3 GIC negative sequence currents Synchronous generator

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A negative sequence Current Phasor Compensation Technique for the Accurate Detection of Stator Shorted Turn Faults in Induction Motors

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ENERGIES 2022年第9期15卷 3100页

作者： Bakhri, Syaiful Ertugrul, Nesimi Natl Res & Innovat Agcy Republ Indonesia Res Ctr Nucl Fuel Cycle & Radioact Waste Technol Puspiptek ComplexBldg 20 Tangerang Selatan 15314 Banten Indonesia

Stator faults are the most critical faults in induction motors as they develop quickly hence requiring fast online diagnostic methods. A number of online condition monitoring techniques are proposed in the literature to respond to such faults, including the signature analysis of the stator current, vibration monitoring, flux leakage monitoring, negative sequence components of voltage and current and sequence components monitoring based on the identification of asymmetrical behavior in a machine. negative sequence components of voltage and current and sequence components monitoring are commonly considered for the identification of asymmetrical behavior of induction motors. negative sequence current analysis is a sensitive technique for the detection of shorted turns as it directly measures the asymmetry produced by the fault. However, the technique is sensitive to other asymmetrical faults and disturbances, which can also produce negative sequence currents. These disturbances include sensor errors, inherent asymmetry and voltage unbalance. This paper provides a comprehensive investigation of the disturbances using a motor model along with experimental measurements under varying load conditions. Then, a new phasor compensation technique is explained to eliminate such disturbances effectively. This technique enables the accurate detection of even relatively small shorted turn faults, even at an early stage. The technique is tested experimentally, and a set of practical results are given to validate the methods developed.

关键词： condition monitoring induction machines negative sequence currents shorted turn faults phasor compensation

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YN/VD connected balance transformer-based hybrid power quality compensator for harmonic suppression and reactive power compensation of electrical railway power systems

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2019年第0期113卷 481-491页

作者： Cui, Guiping Luo, Longfu Li, Yong Liang, Chonggan Hu, Sijia Xie, Bin Xu, Jiazhu Zhang, Zhiwen Liu, Yuxing Wang, Tao Hunan Univ Coll Elect & Informat Engn Changsha 410082 Hunan Peoples R China Guangdong Power Grid Co Ltd Elect Power Res Inst Guangzhou 510080 Guangdong Peoples R China Hunan Sci & Technol Univ Coll Informat & Elect Engn Xiangtan 411201 Peoples R China Power China Zhongnan Engn Corp Changsha 410014 Hunan Peoples R China

In this study, YN/VD connected balance transformer-based hybrid power quality compensator (HPQC) is proposed for harmonic suppression and reactive power compensation in electrified railways. The HPQC is composed of a balance transformer in YN/VD connection, a controllable three-phase voltage source inverter (VSI), as well as fully-tuned passive power filters (PPFs). It is able to integrate the active compensation device with the main transformer, without using auxiliary step-down transformer. This circuit configuration enables one to adopt VSI with low power rating, so that merits such as easy for system integration and low operation losses can be achieved. In this paper, the equivalent circuit model and the corresponding mathematical model of the HPQC in the harmonic domain are established to reveal its mechanism on harmonic suppression. And then, the working principle and control strategy of such a new topology are elaborated in detail. Finally, simulation and experimental results are provided to verify the feasibility and effectiveness of the above-mentioned structure and control strategy.

关键词： Electrical railway YN/VD connected balance transformer negative sequence currents Harmonics suppression Harmonics resonant

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Rotordynamic Analysis of the AM600 Turbine-Generator Shaftline

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ENERGIES 2018年第12期11卷 3411-3411页

作者： Mudau, Tshimangadzo Field, Robert Murray KEPCO Int Nucl Grad Sch Dept Nucl Power Plant Engn 45014 Haemaji Ro Ulsan 689882 South Korea

The AM600 represents the conceptual design and layout of a Nuclear Power Plant Turbine Island intended to address challenges associated with emerging markets interested in nuclear power. When coupled with a medium sized nuclear reactor plant, the AM600 is designed with a unit capacity that aligns with constraints where grid interconnections and load flows are limiting. Through design simplification, the baseline turbine-generator shaftline employs a single low-pressure turbine cylinder, a design which to date has not been offered commercially at this capacity. Though the use of a stiffer' design, this configuration is intended to withstand, with a margin, the damage potential of torsional excitation from the grid-machine interface, specifically due to transient disturbances and negative sequence currents. To demonstrate the robust nature of the design, torsional rotordynamic analysis is performed for the prototype shaftline using three dimensional finite element modelling with ANSYS((R)) software. The intent is to demonstrate large separation of the shaftline natural frequencies from the dominant frequencies for excitation. The analysis examined both welded drum and monoblock type Low Pressure Turbine rotors for single cylinder and double cylinder configurations. For each, the first seven (7) torsional natural frequencies (ranging from zero-190 Hz) were extracted and evaluated against the frequency exclusion range (i.e., avoidance of 1x and 2x grid frequency). Results indicate that the prototype design of AM600 shaftline has adequate separation from the dominant excitation frequencies. For verification of the ANSYS((R)) modelling of the shaftline, a simplified lumped mass calculation of the natural frequencies was performed with results matching the finite element analysis values.

关键词： AM600 ANSYS((R)) grid frequency natural frequency negative sequence currents torsional vibration turbine-generator

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New M-robust algorithm for the calculation of the negative sequence current of a synchronous generator

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ELECTRIC POWER SYSTEMS RESEARCH 2015年 121卷 145-151页

作者： Dukic, Goran Zindovic, Miljana Univ Belgrade Fac Elect Engn Belgrade Serbia Saturn Elect Belgrade Serbia

A novel algorithm for the calculation of the negative sequence current of a synchronous generator is presented in this paper. The algorithm is based on the M-robust methodology of signal processing for the estimation of the rotor endangerment of a synchronous generator during unbalanced conditions. This paper, in light of state-of-the-art methods, presents a novel M-robust algorithm and its application in a system of synchronous generator protection. Under real operating conditions, in which a generator may be in the asymmetrical regime, it is possible that a rotor negative sequence current persists longer than it is allowed to. This current may lead to serious permanent damage to the rotor of the synchronous generator and catastrophic consequences for the synchronous generator, which is the most important component in the process of power generation. As a result, it is important to have algorithms and devices that can prevent operation in dangerous regimes to avoid both serious damage and high financial losses for power-generation utilities. Notably, regarding the unallowable rotor negative sequence current, unbalanced conditions caused by open-circuit faults are more critical than those caused by short-circuit faults because the negative sequence current is lower in the first case, and therefore, detection is more difficult, making it impossible to realise another efficient backup rotor protection function for these types of faults. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Synchronous generator Protection negative sequence currents Impulse noise Outliers M-robust algorithm

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Analysis of static VAr compensators installed in different positions in electric railways

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IET ELECTRICAL SYSTEMS IN TRANSPORTATION 2015年第3期5卷 129-134页

作者： Wang, Hui Liu, Ying Yan, Kun Fu, Yongsheng Zhang, Chenghui Minist Educ Key Lab Power Syst Intelligent Dispatch & Control Jinan 250061 Shandong Peoples R China Shandong Univ Sch Elect Engn Jinan 250061 Shandong Peoples R China State Grid Jibei Elect Power Co Ltd Langfang Power Supply Co Langfang 065000 Hebei Peoples R China State Grid Smart Grid Res Inst EPRI Sci Technol C Beijing 100192 Peoples R China Shandong Univ Sch Control Sci & Engn Jinan 250061 Shandong Peoples R China

With the power quality problems of electric railways becoming more and more serious, static VAr compensators (SVCs) have been widely used for power quality management. SVCs can be installed in the low-voltage side of traction substations, the high-voltage side of traction substations or the electric railway power supply side of substations. Different installation positions result in different compensation effects. In this study, characteristics of harmonic and negative sequence currents in the low-voltage and high-voltage sides of traction substations are analysed theoretically. Four schemes with SVCs in different installation positions are proposed. Then based on the measured datum and waveforms, simulation of each scheme is implemented, respectively, using PSCAD/EMTDC software. By comparing the compensation effects of the four schemes, the best SVC installation scheme in the low-voltage side of the traction substation is recommended for the measured traction substation. With SVC, the electric railway will have a less negative effect on the power grid. This study can also be applied to other SVC applications with non-linear loads, such as arc furnaces, rolling mills or electrochemical devices.

关键词： static VAr compensators power supply quality substations railway electrification power grids power system harmonics traction power supplies static VAr compensator analysis SVCs power quality management traction substations low-voltage side high-voltage side electric railway power supply compensation effects negative sequence currents harmonic characteristics PSCAD-EMTDC software power grid nonlinear loads arc furnaces rolling mills electrochemical devices

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