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Implementing distance line protection schemes among IEC61850-enabled substations
, Article Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference ; April , 2014 , Page(s): 1 - 5 ; ISSN: 21608555 ; ISBN: 9781479936557 ; Darabi, Z ; Vakilian, M
Abstract
As digital technology has developed, relays have evolved from simple electro-mechanical devices into robust microprocessor-embedded intelligent electronic devices (IEDs). Distance protection, one of the most important and sophisticated forms of substation protection, quickly and selectively detects and clears phase faults in sub-transmission and transmission lines. The installation of a substation automation system (SAS) involves implementing control, monitoring, and protection logic by programming the IEDs and providing an appropriate communication network. IEC61850 has gradually satisfied the need for a standard communication protocol so that IEDs from different manufacturers can...
An extended Markov model to determine the reliability of protective system
, Article 2006 IEEE Power India Conference, New Delhi, 10 April 2006 through 12 April 2006 ; Volume 2005 , 2005 , Pages 428-432 ; 0780395255 (ISBN); 9780780395251 (ISBN) ; Fotuhi, M ; Sanaye Pasand, M ; Sharif University of Technology
2005
Abstract
In this paper a reliability model for power transformer protection is proposed. The model is an extension of a previously proposed Markov model for transmission line protection. Optimum routine test and self checking intervals of the power transformer protection system are determined using the extended Markov model. © 2006 IEEE
Extending protection selectivity in low voltage DC microgrids using compensation gain and artificial line inductance
, Article Electric Power Systems Research ; Volume 188 , 2020 ; Vahidi, B ; Razani, R ; Nafisi, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Vulnerability of power electronic converters in DC microgrids in case of fault occurrence in DC cables necessitates using a fast fault detection and isolation scheme. In this paper, a modified, fast and selective protection scheme has been presented, which provides the required tripping of low voltage DC (LVDC) microgrids. This protection scheme has been developed based on the natural characteristics of the fault current, in which the first and second derivatives of the fault current have been employed to define thresholds for discriminating between faulted and non-faulted situations. To enhance fault detection capability of the protection scheme, definition of thresholds have been improved...
Development a Numerical Algorithm for Differential Relay for Transformer Protection
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
The goal of this master thesis is to develop a new accurate numerical algorithm for digital differential relay to protect a power transformer. This work employs specially developed software to simplify its input signal processing task which helps to quickly and accurately detect and clear the transformer internal faults. The available commercial transformer digital differential relays lack the required sensitivity to detect turn to turn faults when a few numbers of turns (less than 10% of the winding) are involved. This work presents a new equivalent circuit for transformer when a turn to turn fault occurs on either winding. This equivalent circuit helped to develop an accurate algorithm for...
LiClO4 · 3H2O promoted highly regioselective ring-opening of epoxides with thiols under neutral conditions [electronic resource]
, Article Catalysis Communications ; 2006, Volume 7, Issue 4, Pages 224–227 ; Saidi, M. R ; Sharif University of Technology
Abstract
A simple, rapid, atom economy and highly efficient procedure has been developed for thiolysis of epoxides by aromatic and aliphatic thiols under solvent-free conditions. A high regioselectivity in favor of nucleophilic attack at the benzylic carbon atom of aromatic epoxides, such as styrene oxide, is observed. However, aliphatic unsymmetrical alkenyl oxides undergo selective nucleophilic attack at the sterically less hindered carbon atom. A variety of β-hydroxy sulfides were obtained in short reaction time and excellent yields with nearly complete regioselectivity
Accurate unbalanced fault location method for multi-ended multi-tapped structures
, Article International Review of Electrical Engineering ; Volume 8, Issue 2 , 2013 , Pages 839-848 ; 18276660 (ISSN) ; Moaddabi, N ; Gharehpetian, G. B ; Mohammadalizadeh Shabestary, M ; Sharif University of Technology
2013
Abstract
The accurate fault location is an important criterion for protection system. Accurate and fast fault location decreases the outage time, consumers dissatisfaction and operation cost. Different methods have been proposed to determine the fault location. The impedance-based methods are usually used to protect power systems. The accuracy of these methods depends on system parameters and the structure of power systems. Also, these methods require an iterative process, the phase alignment and a high volume of data. Another algorithm has been newly presented based on negative sequence parameters, which is not iterative and the amount of data communicated between relays is small. Besides, this...
Transformer practical turn-to-turn fault detection performance using negative sequence and space vector-based methods
, Article 13th International Conference on Protection and Automation of Power System, IPAPS 2019, 8 January 2019 through 9 January 2019 ; 2019 , Pages 1-6 ; 9781728115054 (ISBN) ; Vakilian, M ; Hajipour, E ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Transformer turn-to-turn fault (TTF) is one of the most difficult failures to detect. The negative sequence percentage differential current (NSPD) and extended park vectors approach (EPVA) are the two most promising methods for detection of the TTF inception. In this paper, in order to evaluate the performance of these methods, various experimental tests are carried out to detect the TTF initiation on the winding of the transformer under different operating conditions such as: No-load operation, when an external fault or an open conductor fault is also occurred. The results show that the setting of the proper thresholds plays the main role in the reliable and secure performance of NSPD and...
Quantitative assessment of protection system reliability incorporating human errors
, Article Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability ; Volume 222, Issue 2 , 2008 , Pages 255-263 ; 1748006X (ISSN) ; Fotuhi Firuzabad, M ; Sharif University of Technology
2008
Abstract
The protection system plays a vital role in maintaining a high degree of service reliability in present-day power systems. Considerable work has been done to examine different aspects of protection systems and their associated reliability. All of the reliability predictive methods are based solely on equipment failures, neglecting the human component of the protection system. In this paper, a modified Markov model is presented that incorporates human errors in reliability evaluation of protective devices. Two main types of relay failure (failure to operate and inadvertent operation) are taken into account in the proposed model. The model also considers routine test inspections, the...
Silica sulfuric acid as a reusable catalyst for efficient and simple silylation of hydroxyl groups using hexamethyldisilazane (HMDS)
, Article Phosphorus, Sulfur and Silicon and the Related Elements ; Volume 182, Issue 7 , 2007 , Pages 1645-1651 ; 10426507 (ISSN) ; Eftekhari-Sis, B ; Hashemi, M. M ; Sharif University of Technology
2007
Abstract
At room temperature, alcohols and phenols are efficiently protected with hexamethyldisilazane (HMDS) in the presence of silica sulfuric acid in good to excellent yields. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency. Copyright © Taylor and Francis Group, LLC
A mild and chemoselective dithioacetalization of aldehydes in the presence of anhydrous copper (II) sulfate
, Article Phosphorus, Sulfur and Silicon and the Related Elements ; Volume 181, Issue 6 , 2006 , Pages 1445-1450 ; 10426507 (ISSN) ; Rezanejade Bardajee , G ; Arefi Oskui , A ; Sharif University of Technology
2006
Abstract
Various aldehydes have been protected with different thiols as dithioacetals with excellent yields using anhydrous copper sulfate as a mild and chemoselective catalyst. The reaction is carried out in a solvent and/or under solvent-free conditions. The transthioacetalization of oxyacetals into dithioacetals was also achieved in an excellent yield. Copyright © Taylor & Francis Group, LLC
Idiosyncratic return volatility and the role of firm fundamentals: A cross-country analysis
, Article Global Finance Journal ; Volume 50 , 2021 ; 10440283 (ISSN) ; Hoseinzade, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
We investigate the relation between fundamental idiosyncratic volatility and stock returns idiosyncratic volatility using data from 56 countries. We find a strong positive relation between fundamental idiosyncratic volatility and idiosyncratic volatility of returns. This association, however, seems to be entirely concentrated in the developed economies, and we find no effect in the emerging markets. Specifically, fundamental idiosyncratic volatility does not lead to more idiosyncratic return volatility in countries with poor legal institutions and weak shareholder protection laws. © 2021 Elsevier Inc
Rapid and selective acetalization of aldehydes using anhydrous copper sulfate supported on silica gel (CuSO4/SiO2) under microwave irradiation in solvent-free conditions
, Article Letters in Organic Chemistry ; Volume 2, Issue 2 , 2005 , Pages 151-155 ; 15701786 (ISSN) ; Oskoui, A. A ; Boinee, H. Z ; Sharif University of Technology
2005
Abstract
CuSO4/SiO2 is found to be an efficient and selective medium for the acetalization of aldehydes in the presence of ketones in solvent-free conditions under microwave irradiation. © 2005 Bentham Science Publishers Ltd
Analysis and control of temporary overvoltages for automated restoration planning
, Article IEEE Transactions on Power Delivery ; Volume 17, Issue 4 , 2002 , Pages 1121-1127 ; 08858977 (ISSN) ; Ranjbar, A. M ; Feuillet, R ; Sharif University of Technology
2002
Abstract
The paper presents a new approach that assists power system restoration planning with regards to control of temporary overvoltages (TOVs) due to transformer energization. The frequency-domain analysis in combination with analytical calculations is applied to find an optimum resonance condition. The analytical equations are based on sensitivity analysis for single frequencies and are extended to total sensitivity calculation. After an introduction of the phenomenon of overvoltages during power system restoration and harmonic resonance overvoltages, basic principles of their control are explained. Also, an algorithm is introduced for the results evaluation of harmonic resonance studies where...
Analysis and control of temporary overvoltages for automated restoration planning
, Article IEEE Power Engineering Review ; Volume 22, Issue 6 , 2002 , Pages 64- ; 02721724 (ISSN) ; Ranjbar, A. M ; Feuillet, R ; Sharif University of Technology
2002
Abstract
The paper presents a new approach that assists power system restoration planning with regard to control of temporary over-voltages (TOV) due to transformer energization. The frequency domain analysis in combination with analytical calculations is applied to find an optimum resonance condition. The analytical equations are based on sensitivity analysis for single frequencies and are extended to total sensitivity calculation. After an introduction to the phenomenon of overvoltages during power system restoration and harmonic resonance overvoltages, basic principles of their control are explained. An algorithm is introduced for the results evaluation of harmonic resonance studies where it is...
Protective smart textiles for sportswear
, Article Protective Textiles from Natural Resources ; 2022 , Pages 317-345 ; 9780323904773 (ISBN); 9780323904780 (ISBN) ; Shirazi, M ; Moaref, R ; Jamalpour, S ; Tamsilian, Y ; Kiasat, A ; Sharif University of Technology
Elsevier
2022
Abstract
With the development of modern sports, the design and production of sportswear play an essential role, especially in many modern difficult and dangerous sports. Selection of fibre fabrics is the most important factor because this influences the performance and efficiency, while ensuring protection and physical comfort. In recent years, the demand for smart materials and textiles has been increasing all around the world. Many investigations have been carried out into developing smart textiles that support the better performance of athletes. A smart textile is an intelligent system that is able to sense environmental conditions and electrical, thermal, mechanical, chemical, and magnetic...
Catodic Protection Design & Installation of Rebars in Reinforced Concrete by MMO Anodes
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor) ; Ghorbani, Mohammad (Supervisor)
Abstract
The cathodic protection system was employed for protection of the reinforced concrete of the foundations using the mixed metal oxide anodes embedded in concrete for current distribution. . In this system, after required measurements for zone design calculation of the surfaces current density, IR drop and the circuit’s resistance has been measured. After specifying the appropriate locations for the reference Electrodes (Ag/AgCl) in order for cathodic protection monitoring these three electrodes are installed in three protection zones. After design and supply of all the materials, the installation was started. The protection criterion of steel in concrete was studied and all the measured...
A robust zero-watermarking scheme using Canny edge detector
, Article International Journal of Electronic Security and Digital Forensics ; Volume 5, Issue 1 , 2013 , Pages 25-44 ; 1751911X (ISSN) ; Jamzad, M ; Sharif University of Technology
2013
Abstract
By expansion of digital multimedia and networking technology, the problem of ownership protection has become increasingly important. Digital watermarking is an efficient way for copyright protection of digital images. Traditional watermarking techniques degrade the quality of host image by embedding a watermark logo. Facing this problem, a new watermarking approach called zero-watermarking has been proposed. In zero-watermarking methods, the watermark does not require to be embedded into the protected image but it uses both the watermark and the protected image to generate a verification map which is registered to a trusted authority for further protection. In this paper we propose a robust...
Optimizing the operation of current differential protection by power differential relay for three phase transformer
, Article 2006 IEEE GCC Conference, GCC 2006, Manama, 20 March 2006 through 22 March 2006 ; 2006 ; 9780780395909 (ISBN) ; Esmi Jahromi, M ; Ranjbar, A. M ; Sharif University of Technology
2006
Abstract
To avoid the needless trip by magnetizing inrush current, the second harmonic component is commonly used for blocking differential relay in power transformers. However, the main problems of the current comparison method are in the very high inrush currents and relatively small fault currents regarding winding short circuits. Also The second harmonic component in fault current is increased in long lines which may blocks the relay operation. This paper describes a method to discriminate internal fault from inrush current and faults with a high second harmonic component by the sum of active power flowing into the transformer from each terminal. The average power is almost negligible for...
Backup Protection by Wide Area Measurement System
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
The traditional backup protection system of transmission lines are self-contained and only use from local measurements and generally, don’t use from wide area measurements. Hence, it can misoperate when the power system is extremely under stress conditions. So, the zone 3 of distance relays have been recognized as one of important participating causes of cascading phenomena that lead to major power system blackouts. In modern societies, power systems have become one of most important critical infrastructures, accordingly, blackouts can have catastrophic effects. Therefore, the novel backup protection schemes are required to improve security and dependability of protection system.
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An extended component-based reliability model for protective systems to determine routine test schedule
, Article Turkish Journal of Electrical Engineering and Computer Sciences ; Volume 19, Issue 2 , March , 2011 , Pages 303-315 ; 13000632 (ISSN) ; Firuzabad, M. F ; Ozdemir, A ; Sharif University of Technology
2011
Abstract
This paper presents a novel approach for evaluating the reliability of protective systems taking into account its components reliability. In this paper, a previously proposed extended model is used for a directional over- current scheme. In the extended model, the impacts of individual protective components are taken into account. An optimum routine test schedule is determined for each protective component as a separate unit. A comparison is made to show that the proposed approach has excellence over conventional routine test inspections. Impacts of factors such as circuit breaker inadvertent opening, required time for performing routine test inspections, human mistakes and self-checking and...