共查询到20条相似文献,搜索用时 31 毫秒
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Elmer Sorrentino 《Electric Power Systems Research》2012,82(1):95-97
Two assessment modes for critical clearing times were analyzed in a power system taken as example: (a) with simultaneous tripping at both line ends; (b) with instantaneous tripping at one line end (zone-1 of distance relays), for computing the critical clearing times for the other end (zone-2 of distance relays). Both results are different, and an analysis of these results is included. The results of computing critical clearing times for zone-2 of distance relays when the other end operates in zone-1 have some advantages for the analysis of practical situations. 相似文献
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Many common protective relays used in protection of power equipment are sensitive to phase sequence rotation of the utility supply. A method of analyzing the relay response to the respective phase rotation and other possible variables is described. It is demonstrated that phase rotation usually does not affect zero-sequence polarized relays. The technique is an exercise in voltage and current phasors, maximum torque lines of polarized relays, and the possible effect of system power factor. The following relays are discussed: directional power relay (IEEE Protective Device No.32) as used to protect prime movers on induction and synchronous generators from being motored by the generator due to loss of mechanical power; directional VAr relay (IEEE Protective Device No.55) as used to protect synchronous motors and synchronous generators from receiving VArs from the external power system due to loss of field excitation; directional current phase relay (IEEE Protective Device No.67) as used to detect reverse current flow into a power system from another source due to a system phase fault; and directional current ground relay (IEEE Protective Device No.67N) as used to detect reverse ground current flow into a power system from another source due to a system ground fault 相似文献
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Tadao Aizawa 《Electrical Engineering in Japan》2010,171(4):19-27
In a low‐voltage distribution line in a three‐phase four‐wire system, the neutral conductor current is increased by a current consisting mainly of the third harmonic, which has no phase rotation if the balance of the load has been removed, when harmonic generation equipment is included in the load. The increase of this neutral conductor current increases the waveform distortion of the receiving end voltage, and various kinds of waveform interference occur. To reduce the neutral conductor current, insertion of an active filter for the third harmonic wave near the load has been proposed, and a protective effect against waveform interference has also been reported. In this paper, a method for drastically reducing the neutral conductor current by using LC resonance, which is simpler than an active filter, is proposed. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(4): 19–27, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20897 相似文献
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With an increase in the number of electronic devices, such as personal computers, connected to power distribution lines in commercial buildings, problems associated with their use, such as voltage distortion on utility outlets and excessive neutral current on the distribution lines, become more and more serious. This paper shows control methods and compensation characteristics of series active filters connected to the neutral conductor. The distinctive functions of the proposed active filter are the mitigation of third harmonic voltage and the reduction of neutral current in three‐phase four‐wire distribution systems. The required kVA rating of the proposed active filter is less than 10% of that of the harmonic producing leads. A control method of the DC capacitor voltage on the active filter circuit is also described. It was experimentally demonstrated that one of these two functions of the active filter (to mitigate harmonics or to reduce the neutral current) can be realized selectively and that the DC capacitor voltage of the active filter can be regulated to a desired value. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 53–63, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20227 相似文献
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Huang Wentao Tai Nengling Fan Chunju Liu Dawei 《IEEJ Transactions on Electrical and Electronic Engineering》2016,11(Z1):S57-S67
One of the major issues associated with active distribution networks (ADNs) is to devise an appropriate protection scheme that works successfully in different operation modes. This paper describes the design of an inverse‐time low‐impedance (ITLI) protection scheme with the aid of the advanced measurement technologies in ADNs. The scheme detects faults and calculates tripping time by using the magnitude ratio of the maximum load impedance to the measured impedance. ITLI protection is immune to varying fault current caused by the flexible operation modes and able to automatically adjust fault‐tripping time according to the fault severity. With the existing communication infrastructures, an event‐triggered adaptive setting scheme updates the settings of ITLI relays in real time. The setting method not only enhances the detecting capability but also provides higher reliability and sensitivity before, during, and after events in ADNs, such as tap position adjustment, DGs fluctuation, and network structure change. Besides, an acceleration method based on the definite‐time grading technique is presented to reduce the impact of infeeds and fault resistance. The effectiveness of the proposed protection scheme is demonstrated in a 12.47‐kV active distribution network established by PSCAD/EMTDC. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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A. J. Urdaneta L. G. P rez J. F. G mez B. Feijoo M. Gonz lez 《International Journal of Electrical Power & Energy Systems》2001,23(8):819-825
A linear programming interior point algorithm is proposed for the solution of the problem of coordinating directional overcurrent relays in interconnected power systems considering definite time backup relaying. The proposed algorithm is a variation of the primal–dual approach that uses multiple correctors of centrality. Pre-solution problem filtering simplification techniques are used prior to the application of the linear programming algorithm. Results are presented for the application of the methodology on a realistic test case, a 115–69 kV power system with 108 buses, 86 lines, 61 transformers, and 97 directional overcurrent relays. Optimal solutions are found in an automatic fashion, using the algorithm for the settings of the ground relays as well as for the phase relays. The application of the pre-solution problem simplification techniques is highly recommended, resulting in a significant reduction of the size and complexity of the linear programming problem to be solved. The interior point approach reaches a feasible point in the close vicinity of the final optimal result in only one or two iterations. This fact represents an advantage for on-line applications. The proposed methodology and in particular the use of the presolve problem simplification techniques is shown as a new valuable tool for the setting of directional overcurrent relays in interconnected power systems. 相似文献
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西门子7SJ系列微机保护继电器小电流接地系统单相接地故障保护原理的分析 总被引:1,自引:0,他引:1
西门子系列微机保护继电器处理小电流接地系统单相接地故障的功能模块包括零序电压检测、零序电流检测、接地选相、接地方向判定及CT误差角补偿等.作者对以上各部分进行了详细介绍,并着重分析了其利用零序功率分量方向进行接地方向判定的原理方法. 相似文献
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对中性点不接地系统,中性点经电阻接地系统和中性点经消弧线圈接地系统这三种10kV系统中性点接地方式进行了讨论,客观地分析了它们的优缺点和适合场合。提出一种新型的接地方式-可控消弧线圈加接地故障选线跳闸装置,它具有消弧线圈接地的优点,又克服了传统消弧线圈不能连续调节、响应慢的缺点,应用前景广阔。 相似文献
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The reliability of an industrial power system can be increased by proper selection and application of protective relays. This is especially true for the medium-voltage distribution system. An effective protective relay application scheme is presented that uses devices widely used in present pulp and paper mill power distribution systems. The effective use of summation overcurrent and directional overcurrent relays for multisource generator buses makes it possible for the power system protective engineer to achieve good selective operation between source buses for both phase and ground fault current conditions. This greatly enhances the reliability of the power distribution system 相似文献
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分析了TN系统接地故障保护存在的问题,指出了解决对策,阐述了低压断路器接地脱扣器动作电流整定值及动作时间的设计与选择。 相似文献
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Harmonics bred from loads are mainly odd order because the current waveforms have half‐wave symmetry. Since the even harmonics are negligibly small, they generally are not measured in electric power systems. However, even harmonics were measured at a 500/275/154 kV substation in Hokuriku Electric Power Company after a transmission line fault was corrected. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as the automatic supervisory signal. This paper describes mechanisms of generation of the even harmonics by comparing the measured waveforms with the ATP‐EMTP simulation results. Analysis of these results has clearly shown that there are three different mechanisms of generation of even harmonics. The first mechanism is the appearance of a magnetizing current in transformers due to flux deviation by the DC component of the fault current. The second mechanism is harmonic conversion of a synchronous machine which generates even harmonics when the DC component or the even harmonic current flow into the machine. The third mechanism is an increase of harmonic impedance due to an isolated power system, thus producing the harmonic voltages. The design of the input filter of protective digital relays should take into account even harmonics generation in an isolated power system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 56–63, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20592 相似文献
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通过分析低压配电网中中性点人为接地、故障接地的电气特征,揭示了低压配电网中普遍存在同异同接地现象,造成了大量的电能浪费。指出采用拆除中性点接地、有效不间断监控和及时排除接地故障等措施,使电网与地绝缘,可防止电能流失。 相似文献
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斜桥变电所铁磁谐振过电压的仿真研究 总被引:1,自引:0,他引:1
为提高嘉兴电力局配电网面对铁磁谐振过电压的安全性,以斜桥变电所10kV配电网为模型,利用EMTP程序仿真分析了在TV高压侧中性点接非线性电阻、串单相TV(4TV方式)及TV开口三角绕组接阻尼电阻或分频消谐装置等多种消谐措施。结果表明非线性电阻能保持相电压稳定及抑制涌流,正温度系数热敏电阻和3次谐波滤波器可较好解决零序电压的偏高;4TV方式一次侧电流和零序电流过大等问题。还分析了分频消谐装置在实际运行中不能很好消谐的原因。仿真分析结果对提高配电网的供电安全可靠性具有很好的实用价值。 相似文献