scholarly journals Investigating Phase Over-Current (OC) Protection in Medium-Voltage networks

2019 ◽  
Vol 4 (6) ◽  
pp. 41-49 ◽  
Author(s):  
Aniagboso John Onah
Keyword(s):  
Power System ◽  
Electric Power ◽  
Electric Power System ◽  
Normal Operation ◽  
Electrical Network ◽  
Power Circuit ◽  
Medium Voltage ◽  
Protection Scheme ◽  
Overcurrent Protection ◽  
Overcurrent Relays

Overcurrent protection is protection against excessive currents or current beyond the acceptable current rating of equipment. It generally operates instantly. Short circuit is a type of overcurrent. Magnetic circuit breakers, fuses and overcurrent relays are commonly used to provide overcurrent protection. There is always a need to protect expensive power equipment. Protective relaying is a very important part of any electric power system that comes into play during trouble, fault or abnormal condition. The purpose is to isolate unhealthy part of electrical power system while the rest continue their normal operation. The entire electric power system from source to load centers is exposed and subject to natural hazards. The effects of these hazards are capable of interrupting normal operations of the system. Since these hazards cannot be prevented, precautions are taken to minimize or eliminate their effect on the system. The relay is a basic component of any protection scheme. The information (or signals) received from the power system actuates the relay, when necessary, to perform one or more switching actions. The signals are proportional to the magnitudes and phase angles of power system voltages and currents. When the relay receives these signals, it decides to close (or open) one or more sets of normally open (or closed) contacts, and consequently, the trip coil of a circuit breaker will be energized to open the power circuit. This paper investigates over-current relay protection scheme applied to medium-voltage electrical network. Methods of current and time grading have been applied in the coordination of the overcurrent relays in a radial network. Different time/current characteristics of relays such as the normal inverse (NI), very inverse (VI), and extreme inverse (EI) have been examined in order to obtain optimum discrimination.

scholarly journals Study on Impedance Characteristics of Aircraft Cables

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Weilin Li ◽  
Wenjie Liu ◽  
Xiaobin Zhang ◽  
Zhaohui Gao ◽  
Meng Xie ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Power System ◽  
Electric Power ◽  
Electrical Equipment ◽  
Electric Power System ◽  
Normal Operation ◽  
Variable Frequency ◽  
Forming Mechanism ◽  
Changing Trends ◽  
Impedance Characteristics

Voltage decrease and power loss in distribution lines of aircraft electric power system are harmful to the normal operation of electrical equipment and may even threaten the safety of aircraft. This study investigates how the gap distance (the distance between aircraft cables and aircraft skin) and voltage frequency (variable frequency power supply will be adopted for next generation aircraft) will affect the impedance of aircraft cables. To be more precise, the forming mechanism of cable resistance and inductance is illustrated in detail and their changing trends with frequency and gap distance are analyzed with the help of electromagnetic theoretical analysis. An aircraft cable simulation model is built with Maxwell 2D and the simulation results are consistent with the conclusions drawn from the theoretical analysis. The changing trends of the four core parameters of interest are analyzed: resistance, inductance, reactance, and impedance. The research results can be used as reference for the applications in Variable Speed Variable Frequency (VSVF) aircraft electric power system.

scholarly journals Influence of Oil-Filled Transformers Overload Capacity on the Throughput Capacity of the Electrical Network

2018 ◽  
Vol 61 (4) ◽  
pp. 310-320
Author(s):  
V. A. Anishchenko ◽  
I. V. Gorokhovik
Keyword(s):  
Service Life ◽  
Power System ◽  
Electric Power ◽  
Power Supply ◽  
Electric Power System ◽  
Throughput Capacity ◽  
Electrical Network ◽  
Economic Losses ◽  
Insulation Material ◽  
Overload Capacity

During the operation of the electric power system, there is often a need to overload its individual elements (generators, power transformers, overhead and cable power lines, switching electric devices) for a period lasting from several dozens of minutes to a day. The overloads can be caused by intentional disconnection of parallel elements of the system because of scheduled preventive repairs, post-accident disconnections, as well as an unexpected increase in electricity consumption due to the impact of various factors. The overload capacity of the system elements makes it possible to increase operational reliability of power supply to consumers without additional expenditures while maintaining, in most cases, the almost normal service life of electrical equipment. Oil-filled transformers have the greatest potential overload capacity power, which makes it possible to consider them as a significant source of increasing the capacity of the transmission and distribution networks of the electric power system. Excessive over-current of power oil-filled transformers significantly reduces reliability and reduces their normal service life. This is due to the accelerated process of wear of the insulation material of the transfer windings as a result of overheating of the transformer oil, that causes structural changes and, as a consequence, to mechanical damage to the insulation of the windings; the latter can cause an electrical puncture. On the other hand, underestimation of the permissible overload of transformers might result in economic losses due to under-produced products when the functioning of the part of the transformers connected in parallel are ceased for scheduled preventive maintenance or as a result of forced emergency shutdowns. Therefore, there is a need to assess the potential of reasonable increase in the throughput capacity of the electrical network and, accordingly, the reliability of the power supply system, taking into account the requirements for the permissible loads of transformers when the electrical network and various operating modes are being designed.

Research and Construction of Information Security Simulation Test Bed for Electric Power System

2013 ◽  
Vol 427-429 ◽  
pp. 2826-2829
Author(s):  
Hao Li Luan ◽  
An Gang Zheng ◽  
Zhen Liu Zhou ◽  
Zheng Yang
Keyword(s):  
Information Security ◽  
Power System ◽  
Electric Power ◽  
Information Technologies ◽  
Electric Power System ◽  
Normal Operation ◽  
Test Bed ◽  
Security Testing ◽  
Layer System ◽  
Common Information

Electric power system relies heavily on common information technologies and platforms, so all common information security issues have been experienced in the electric power information system. Because of attacks destructivity and uncontrollability, it is inappropriate to conduct security analysis in a real Power system directly. Therefore, the paper uses simulation and emulation technology to build a information security test bed for power system at a lower cost and no affect the normal operation and the premise of the aimed system. Simulation contents in the test bed are arranged in four different layers including firmware layer, system layer, network layer and application layer. The test bed also provides a network attack and defense combat system. The test bed can be used for Power system information and network system security testing, engineering validation and evaluation.

Information Model of ARC Protection System Based on IEC 61850

2011 ◽  
Vol 383-390 ◽  
pp. 2540-2544
Author(s):  
Dong Jiang Li ◽  
Yi Zhang
Keyword(s):  
Power System ◽  
Electric Power ◽  
Electric Power System ◽  
International Standards ◽  
Protection System ◽  
Protection Device ◽  
Iec 61850 ◽  
Medium Voltage ◽  
Relationship Of ◽  
The Relationship

This paper analyzes operation problems of medium voltage switchgear cabinet in the electric power system. According to the international standards of IEC 61850, model the new arc protection device on the bus and analysize the relationship of abstract communication serivce inferface (ACSI) mapping to manufacturing message specification (MMS). Finally, MMS PDU formation and decoding are described specifically based on ASN.1 encoding rules.

scholarly journals Reliability Assessment of Electric Power System with Distributed Generation Facilities

2020 ◽  
Author(s):  
B. Papkov ◽  
V. Osokin
Keyword(s):  
Power Systems ◽  
Power System ◽  
Electric Power ◽  
Distributed Generation ◽  
Renewable Energy Sources ◽  
Electric Power System ◽  
Operating Conditions ◽  
Electrical Network ◽  
Traditional Concept ◽  
Reliability Indices

Modern power supply systems that have distributed generation and are connected to the electric power system, renewable energy sources, and storage devices, require changes in the assessment of their reliability indices. The complexity of the energy, technological, and organizational structures of power systems with distributed generation does not allow the traditional concept of "failure" to be used to assess their reliability. Many technological solutions used in the distributed generation projects can become sources of vulnerabilities in the infrastructure of an intelligent electrical network. The study shows that power systems with distributed generation are the structures with overlapping service areas, which determines their specific features represented by an integral characteristic - efficiency. It characterizes the extent to which the use of distributed generation facilities in various operating conditions is feasible. The paper proposes an approach to quantifying the efficiency of such systems. The presented examples demonstrate the calculation of relatively simple power systems with the distributed generation that perform several tasks simultaneously.

scholarly journals Problems of Electric Power System Management taking into account Sources Distributed Generation

2020 ◽  
Vol 220 ◽  
pp. 01034
Author(s):  
Muhayo Toshkhodzhaeva ◽  
Elena Gracheva ◽  
Okhunbobo Rahimov ◽  
Shakhboz Dadabaev
Keyword(s):  
Power System ◽  
Electric Power ◽  
Distributed Generation ◽  
Power Supply ◽  
Electric Power System ◽  
Point Of View ◽  
Operating Conditions ◽  
Electrical Network ◽  
System Management ◽  
Existing Problems

This article provides a brief overview of the existing problems of managing the electric power system, taking into account the sources of distributed generation. The features of centralized and decentralized power supply systems are considered from the point of view of changing operating conditions, in particular, eliminating the consequences of technological violations. The main goals of the electric power system management have been determined, regardless of the number of sources and the category of consumers in terms of power supply reliability, as well as in emergency and post-emergency modes. The basic principles and sequence of power system management are presented. An algorithm for the efficiency of operation and dispatch control of the power system is considered, methods for ensuring the selective operation of relay protection and automation devices in the presence of several generating capacities are presented. A fragment of an electrical network with four energy sources is shown and the main measures to ensure its normal functioning are proposed.

Analysis on Special Protection Scheme of Korea Electric Power System by Fully Utilizing STATCOM in a Generation Side

2017 ◽  
Vol 32 (3) ◽  
pp. 1882-1890 ◽  
Author(s):  
Dong-Hee Choi ◽  
Soo Hyoung Lee ◽  
Yong Cheol Kang ◽  
Jung-Wook Park
Keyword(s):  
Power System ◽  
Electric Power ◽  
Electric Power System ◽  
Protection Scheme ◽  
Special Protection

scholarly journals DETERMINATION OF “WEAK” BY POWER TRANSFORMERS RELIABILITY OF POWER SYSTEMS ACCORDING TO THE RESULTS OF FAILURE RISK ASSESSMENT UNDER EXTERNAL SHORT CIRCUITS

2021 ◽  
Author(s):  
Eugeniy I. Bardik ◽  
Mykola P. Bolotniy ◽  
Yaroslav S. Koval
Keyword(s):  
Mathematical Model ◽  
Risk Assessment ◽  
Power System ◽  
Electric Power ◽  
Power Transformer ◽  
Short Circuit ◽  
Electric Power System ◽  
Power Transformers ◽  
Electrical Network ◽  
Failure Risk

Background. The increase of technological violation intensity and its consequences severity is caused mainly by objectively existing aging and service life depletion of electrical equipment. The power industry liberalization exacerbates the reliable operation problem of the power system and requires identification of power system operation accompanied by the maximum emergency risk with possible cascade accidents development. Therefore, the model development task for assessment of the equipment failure risk based on the diagnostic results of technical condition in particular under short circuit in the external network is relevant today. Objective. The aim of the work is to develop a fuzzy mathematical model for probability assessment of power transformer failure in the presence of a windings defect, short circuit in external network and emergency risk assessment under power transformers out of service. Methods. The fuzzy set theory and fuzzy logic were used for developing a mathematical model of risk assessment of power trans- former failure. The problems of determining the “weak” in terms of power transformers reliability of power systems based on the results of failure risk assessment due to external short circuits were solved by methods of fuzzy logic and probabilistic-statistical simulation of electric power system modes. Results. The necessity of complex simulation of electric power system modes is substantiated for probability assessment of power transformer failure under electrical network disturbances. The simulation of technical condition of power transformer windings was carried out. The short circuit influence on operability level of power transformers of electric power system was investigated. The quantitative indicators of operational risk of electric power system were determined under power transformers out of service. Conclusions. The linguistic mathematical model for estimating the failure probability of power transformer windings in the presence of defect and short circuit in electrical network has been developed to determine the quantitative indicators of emergency risk in power system.

scholarly journals The Effect of Distributed Generator Injection with Different Numbers of Units on Power Quality in the Electric Power System

2021 ◽  
Vol 1 (2) ◽  
pp. 71
Author(s):  
Robi Kurniawan ◽  
Ardiansyah Nasution ◽  
Arnawan Hasibuan ◽  
Muzamir Isa ◽  
Muskan Gard ◽  
...  
Keyword(s):  
Power System ◽  
Electric Power ◽  
Distributed Generation ◽  
Reactive Power ◽  
Voltage Drop ◽  
Load Flow ◽  
Electric Power System ◽  
Total Loss ◽  
Electrical Network ◽  
Power Losses

Distributed Generation (DG) is a small capacity generator located in the electricity distribution system and is usually placed on buses that are connected directly to the load. Placement of distributed generation is one of the technical efforts to reduce voltage drop and power losses in the system. In addition, load flow analysis is a study to plan and determine the amount of power in an electric power system. The results of power losses after adding distributed generation were the best in the fifth experiment on bus 149, where the system experienced a total loss of active power (P) previously of 720,822 kW, to 682,939 kW and total loss of reactive power (Q) previously of 530.02 kVar, to 405.835 kVar. From the results of the calculation of the power flow using ETAP software (Electrical Transient Analyzer Program). So, it can be concluded that the electrical network system can be said to be good. The results obtained are the more DG (wind turbine generator) that is input into the bus it will reduce the voltage drop that occurs. After simulating the overall voltage drop, it still meets the standards according to the results of the Text Report on ETAP.

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