A model for calculating the temperature of aluminium particles ejected from overhead low-voltage lines owing to a short-circuit

2009 ◽  
Vol 18 (6) ◽  
pp. 722 ◽  
Author(s):  
E. G. Psarros ◽  
A. D. Polykrati ◽  
C. G. Karagiannopoulos ◽  
P. D. Bourkas
Keyword(s):  
Mathematical Model ◽  
Molten Metal ◽  
High Voltage ◽  
Temperature Rise ◽  
Low Voltage ◽  
Short Circuit ◽  
Weather Conditions ◽  
Metal Particles ◽  
Overhead Lines ◽  
Protection Systems

Wildfires, which are uncontrolled fires spreading readily over vast areas, are usually the result of human negligence, arson or lightning. There are cases of fires close to electrical distribution lines for which the network has been blamed. In the present paper, the risk of a wildfire breaking out owing to the temperature of molten metal particles that are possibly created on bare conductors of low-voltage networks in short-circuit faults (unless they are interrupted by the protection systems) is examined. Thus, a mathematical model is proposed for the estimated temperature rise of those molten metal particles ejected from bare conductors of low-voltage overhead lines. Moreover, this model can be applied to medium- or high-voltage networks. The model takes into account the weather conditions and particles’ height above the ground. Further, an arithmetic example for an incandescent particle ejected from aluminium conductors of a low-voltage network is given. According to this example, there is no risk of dead leaves or wood catching fire owing to this particle.

scholarly journals Analysis of the Torsional Stability of Split Phases

2019 ◽  
Vol 62 (6) ◽  
pp. 503-513
Author(s):  
I. I. Sergey ◽  
Y. G. Panamarenka ◽  
Y. V. Potachits ◽  
N. A. Yudina
Keyword(s):  
High Voltage ◽  
Climatic Factors ◽  
Short Circuit ◽  
Low Frequency ◽  
Power Lines ◽  
Structural Elements ◽  
Stability Calculation ◽  
Overhead Lines ◽  
Torsional Stability ◽  
Overhead Power Lines

The specificity of overhead power lines is associated with the fact that the length of conductors between the supporting structures can reach tens of thousands of meters. Wires and their components are exposed to climatic factors, viz. wind, rain, ice, snow. As compared to other structural elements, conductors are of the highest flexibility and lowest rigidity, and, therefore, they are the most sensitive elements to these effects. Since the early fifties of the XX century, the increase in energy consumption has caused the construction of high and ultra-high voltage overhead lines with split phases. For these types of conductors, new forms of oscillations have been noticed in the areas between the struts, the essence of which is torqueing the split phase. As a result, there is a violation of the torsional stability of the phase: collision of wires in the middle of sub-span and friction of wires of stranded conductor against each other, which leads to damaging conductors and, as a consequence, to disruption of power supply to consumers. Almost any overhead lines may be subjected to oscillations of wires in the span under the influence of wind. One of the types of such mechanical oscillations is galloping, i. e. low-frequency oscillations of wires with an amplitude reaching the value of the boom of wire sagging, and, taking into account the possibility of elongation of the wire, even exceeding it. Fluctuations in the galloping can cause significant mechanical forces and last long enough to lead to the destruction of structural elements of power lines, viz. wires, insulators, fittings and even pillars. Due to the large amplitude of oscillations, conductors of neighboring phases can approach each other at an unacceptable distance, resulting in a short circuit. The boundary value problem of the torsional stability calculation of the split phase with a given multiplicity of splitting has been set and solved. The critical lengths of the sub-spans at which the stable violation of torsional stability is most likely have been determined. A computer program has been developed, which can be used in the design of high-voltage lines with split phase.

INDIRECT TEST CIRCUIT FOR TESTING HIGH VOLTAGE FUSES IN OVERLOAD CONDITIONS

2016 ◽  
Vol 63 (0) ◽  
pp. 83-87
Author(s):  
Janusz KURASZKIEWICZ ◽  
Janusz BANDEL ◽  
Artur HEJDUK ◽  
Krzysztof KRASUSKI ◽  
Andrzej DZIERŻYŃSKI ◽  
...  
Keyword(s):  
High Voltage ◽  
Switching Time ◽  
Low Voltage ◽  
Short Circuit ◽  
Test Method ◽  
Indirect Test ◽  
Test Circuit ◽  
The Moment ◽  
Indirect Tests ◽  
A Current

During direct tests of high voltage fuses in overload conditions, the tested fuse has to carry the rated overload current at the rated voltage for a long enough time to interrupt the overcurrent. These types of tests cannot be done in short circuit laboratories. A short circuit generator cannot be excited for the length of time needed to complete the test. Therefore the indirect test method is often applied. It uses separate current and voltage circuits in sequence: first the fuse is supplied from a low voltage current circuit to conduct a current of the recommended intensity and, at the moment of the current interruption, the fuse is disconnected from the low voltage circuit and switched to a high voltage circuit. To ensure the equivalence of the direct and indirect tests the switching time from the current to the voltage circuit should be as short as possible. This paper describes a fast operating switch for use in such tests.

Scheme of Protection and Monitor Underground High-Voltage Power Supply System Based on PROFINET

2014 ◽  
Vol 668-669 ◽  
pp. 741-744
Author(s):  
Hai Bo Liu ◽  
Yu Mei Wang
Keyword(s):  
High Voltage ◽  
Power Supply ◽  
Short Circuit ◽  
Monitoring Network ◽  
High Voltage Power Supply ◽  
Interface Circuit ◽  
Power Monitoring ◽  
Monitor Function ◽  
Protection Systems ◽  
High Voltage Power Lines

Short circuit protection of high-voltage power lines in coal mine cannot realize selectivity with existing protection systems. To solve this problem, a scheme of protection and monitor underground based on PROFINET was proposed. The system is mainly composed of PROFINET network, monitor, controller, and integrated protector with PROFINET IO interface circuit. The system achieves protection and power monitoring network integration, completes the selectivity of short circuit protection, and can determine fault position quickly. Thus the troubleshooting time is cut and reliability of power supply network is improved. The simulation results show that the POROFINET real-time meets the requirement of protection and the system can realize short-circuit protection and power monitor function.

scholarly journals ANALYSIS THE REASONS OF 110 kV TRANSFORMERS BREAK DOWN AND THE METHODS OF ITS DIAGNOSTICS

2018 ◽  
Vol 13 (2) ◽  
pp. 124-127
Author(s):  
Леонид Рыбаков ◽  
Leonid Rybakov ◽  
Валерий Белов ◽  
Valeriy Belov ◽  
Надежда Макарова ◽  
...  
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Short Circuit ◽  
Statistical Processing ◽  
Power Transformers ◽  
Electrical Strength ◽  
Diagnostic Tools ◽  
New Methods ◽  
Burn Out ◽  
Internal Short Circuit

The article deals with the diagnostics of power transformers by different methods. Particular attention is paid to modern methods and diagnostic tools that maximally allow to determine the state of the transformer. Based on the statistical processing of the results of the research, the authors indicate that the most common failures are: damage to the windings of transformers with the possibility of regulation under load, without disconnecting power and leaving consumers without power supply (RPN) for any period of operation. The greatest number of damages for transformers with on-load tap-changers with a service life of 10-30 years, for high-voltage bushings after 10 years of operation. The most severe damage to the transformer is an internal short circuit (short circuit). These types of overvoltage cause damage to the windings in 80% of the total number of damage, high-voltage bushings - 89%, RPN - 25% and other elements - 36%. It is indicated that a serious consequence occurs when such defects develop, as: the reduction of the electrical strength of the oil channel of high-voltage hermetic bushings due to deposition of sediment on the inner surface of porcelain and on the surface of internal insulation; reduction of the electrical strength of paper-oil insulation of high-voltage leaky inlets due to moisture and pollution; humidification, contamination and wear (aging) of the insulation of the windings; burn-out of the coil insulation and windings of the windings because of the long non-operation of the through-current fault on the low-voltage side of the transformer; errors in installation, repair and operation. In the conclusions it is recommended to supply the manufacturers of power transformers with means for diagnosing the main elements of power transformers, which should be built-in. Particular mention was made of the need to focus in the future on improving existing and creating new methods for monitoring equipment of power transformers.

scholarly journals A DC-side fault-tolerant bidirectional AC/DC converter for power system in integration of low-voltage DC distribution systems

2021 ◽  
Author(s):  
Nikoo Kouchakipour
Keyword(s):  
Mathematical Model ◽  
Power System ◽  
Power Distribution ◽  
Distribution Systems ◽  
Low Voltage ◽  
Short Circuit ◽  
Power Converter ◽  
Software Environment ◽  
Medium Voltage ◽  
Dc Distribution

With the rising potential for the employment of low- and medium-voltage direct-current (dc) electric power distribution systems, most notably for a more efficient integration of plug-in electric vehicles and such other distributed energy resources as photovoltaic (PV) panels, there is a need for robust ac/dc electronic power converters that can interface such dc distribution systems with the legacy alternating current (ac) power system. Thus, this thesis proposes a new single-stage low-voltage three-phase ac-dc power converter that is simple structurally, en- ables a bidirectional power exchanges between the ac and dc distribution systems, and can handle short-circuit faults at its dc as well as ac sides. The proposed converter consists of three legs, corresponding to the three phases of the host ac grid, each of which hosting two full-bridge submodule (FBSM), in an architecture that can be regarded as a special case of the so-called modular multi-level converter (MMC). Thus, at the dc port each FBSM is connected in parallel with a corresponding capacitor, while the ac voltage of each phase is synthesized by the coordinated sinusoidal pulse-width modulation (SPWM) of the two corresponding FBSMs. This architecture allows the generation of low-distortion ac voltage while it also provides the converter with the very important dc fault current blocking capability since, upon the detection of a short circuit across the converter dc port, the switches of the FBSMs are turned off and disallow the flow of any dc current. The thesis also presents a mathematical model for the converter, for analysis and control design purposes. Thus, the control for the regulation of the overall dc-side voltage, as well as those for the regulation of the dc voltages of the FBSMs are devised based on the aforementioned mathematical model and presented with details. It is further shown that the voltage conversion ratio of the proposed converter is the same as that offered by a conventional voltage-sourced converter (VSC), whereas the VSC is vulnerable to dc- side shorts. The proposed converter can be extended to medium-voltage levels by multi- plying the number of FBSMs in each leg. The effectiveness of the proposed converter and its controls is demonstrated through time-domain simulation studies conducted on a topological model of the converter in PSCAD/EMTDC software environment.

Demonstrative HEAF (High Energy Arcing Fault) Fire Tests of High and Low Voltage Switchgears of Nuclear Power Plants

2018 ◽  
Author(s):  
Koji Shirai ◽  
Tsukasa Miyagi ◽  
Mikimasa Iwata ◽  
Koji Tasaka ◽  
Junghoon Ji
Keyword(s):  
High Voltage ◽  
Nuclear Power ◽  
Power Plants ◽  
Distribution Systems ◽  
Low Voltage ◽  
Arc Discharge ◽  
Short Circuit ◽  
High Energy ◽  
Fire Event ◽  
Three Phase

High Energy Arcing Faults (HEAF) have the potential to cause extensive damage to the failed electrical components and distribution systems along with adjacent equipment and cables within the zone of influence (ZOI). Furthermore, the significant energy released during HEAF event can act as an ignition source to other components within the area of the HEAF. In Japan, during the Great East Japan Earthquake occurred in 2011, the seismic induced HEAF fire event, which induced the whole damage of the multiple high voltage switchgears, was observed in Onagawa Nuclear Power Plant (NPP). In response, in August 2017, the NRA (Nuclear Regular Authority) in Japan amended the safety requirement for the power supply to consider the influence of the successive fire due to the HEAF event (hereinafter HEAF fire event). Therefore, it is urgently necessary to establish the design criteria to prevent the HEAF fire event, and enhance the experiment data of the HEAF fire event. In order to estimate the total arc energy during the HEAF event and obtain the threshold value to prevent the HEAF fire for the existed non-arc proof electrical cabinets, several series of three-phase internal arc tests with high (6.9kV class) and low (480V class) voltage electrical cabinets were executed. We executed internal arc tests with full scale high/low voltage metal-enclosed switchgear components (non-arc proof type, copper bus conductor), and evaluated arc energy, the mechanical damage of the cabinet and the surrounding equipment due to the impulsive pressure and the possibility of successive fire occurrence. In case of high voltage switchgear, when the arcing energy exceeded 25.3MJ, successive fire was identified. Especially, in the case where the arc flash was discharged in the circuit breaker room, a 2-second arcing duration in a three-phase short-circuit current with 18.9kA (measured arcing energy over 40MJ) caused successive fire which required extinguishment. On the other hand, in case of low voltage power center, when the arcing energy exceeded 19MJ, successive fire was identified. According to these demonstrative tests, this paper presents the evaluation method to estimate total arc discharge energy during the HEAF event for high and low voltage electrical cabinets.

scholarly journals Determination of Electromagnetic Influence of 25 kV AC Electric Traction Network on 10 kV High-Voltage Overhead Line

2021 ◽  
Vol 2096 (1) ◽  
pp. 012078
Author(s):  
O V Zalesova
Keyword(s):  
High Voltage ◽  
Short Circuit ◽  
Electrical Equipment ◽  
Point Of View ◽  
Overhead Line ◽  
Induced Voltage ◽  
Operating Personnel ◽  
Overhead Lines ◽  
Traction Network ◽  
Electrified Railways

Abstract Electrified railways include a system of cable and overhead lines. An analysis of the operation of alternating current (AC) electrified railways sections shows that the value of the induced voltage caused by the operation of the traction network can significantly exceed the permissible level on adjacent disconnected high-voltage overhead lines. As a consequence, this leads to serious injuries to operating personnel, including deaths, failure of electrical equipment. From this point of view, 1x25 kV 50 Hz AC railway system networks are considered the most dangerous. The electromagnetic influence of the traction network of a double-track section of an AC railway on an adjacent 10 kV high-voltage overhead line for power supply of automatic block signalling is investigated in the offered paper. Emergency cases of traction network operation are considered: short-circuit situation and forced state. The calculations of short-circuit currents in the influencing inter-substation zone, as well as estimation of the induced voltage on the wires of the 10 kV disconnected high-voltage overhead line for various schemes of grounding, have been performed. The investigations were carried out on models built using the ATP-EMTP program.

scholarly journals A DC-side fault-tolerant bidirectional AC/DC converter for power system in integration of low-voltage DC distribution systems

2021 ◽  
Author(s):  
Nikoo Kouchakipour
Keyword(s):  
Mathematical Model ◽  
Power System ◽  
Power Distribution ◽  
Distribution Systems ◽  
Low Voltage ◽  
Short Circuit ◽  
Power Converter ◽  
Software Environment ◽  
Medium Voltage ◽  
Dc Distribution

With the rising potential for the employment of low- and medium-voltage direct-current (dc) electric power distribution systems, most notably for a more efficient integration of plug-in electric vehicles and such other distributed energy resources as photovoltaic (PV) panels, there is a need for robust ac/dc electronic power converters that can interface such dc distribution systems with the legacy alternating current (ac) power system. Thus, this thesis proposes a new single-stage low-voltage three-phase ac-dc power converter that is simple structurally, en- ables a bidirectional power exchanges between the ac and dc distribution systems, and can handle short-circuit faults at its dc as well as ac sides. The proposed converter consists of three legs, corresponding to the three phases of the host ac grid, each of which hosting two full-bridge submodule (FBSM), in an architecture that can be regarded as a special case of the so-called modular multi-level converter (MMC). Thus, at the dc port each FBSM is connected in parallel with a corresponding capacitor, while the ac voltage of each phase is synthesized by the coordinated sinusoidal pulse-width modulation (SPWM) of the two corresponding FBSMs. This architecture allows the generation of low-distortion ac voltage while it also provides the converter with the very important dc fault current blocking capability since, upon the detection of a short circuit across the converter dc port, the switches of the FBSMs are turned off and disallow the flow of any dc current. The thesis also presents a mathematical model for the converter, for analysis and control design purposes. Thus, the control for the regulation of the overall dc-side voltage, as well as those for the regulation of the dc voltages of the FBSMs are devised based on the aforementioned mathematical model and presented with details. It is further shown that the voltage conversion ratio of the proposed converter is the same as that offered by a conventional voltage-sourced converter (VSC), whereas the VSC is vulnerable to dc- side shorts. The proposed converter can be extended to medium-voltage levels by multi- plying the number of FBSMs in each leg. The effectiveness of the proposed converter and its controls is demonstrated through time-domain simulation studies conducted on a topological model of the converter in PSCAD/EMTDC software environment.

Protection Systems and Earthing Schemes for Microgrids: Main Aspects and Fault Analysis

2018 ◽  
Vol 19 (4) ◽  
Author(s):  
Filipe Bandeiras ◽  
Mário Gomes ◽  
Paulo Coelho ◽  
José Fernandes ◽  
Carlos Moreira
Keyword(s):  
Distribution Systems ◽  
Fault Location ◽  
Low Voltage ◽  
Short Circuit ◽  
Fault Analysis ◽  
Equivalent Impedance ◽  
Protection Systems ◽  
Protection Devices ◽  
Internal Faults ◽  
Short Circuit Analysis

AbstractThe content of this paper aims to assist in the development and implementation of microgrids by addressing the challenges and possible solutions for their protection systems. Therefore, an overview of some protection methods available in the literature that can be implemented to ensure a safe and reliable microgrid operation is presented, including the most common protection devices and earthing schemes that can be adopted in low voltage distribution systems. In addition, this paper also presents a brief fault analysis of internal faults at three different locations in an industrial microgrid with centralized and decentralized deployment of energy sources, as well as a short-circuit analysis of symmetric and asymmetric faults at these faulty locations. An approximate method based on the calculation of the equivalent impedance seen from the fault location is used to determine the fault currents. This study is made to observe how microgrids with different configurations perform in the event of internal faults.It is demonstrated in this work that setting a specific protection strategy to allow the microgrid to operate effectively during both operation modes can be problematic and expensive in most situations. With this in mind, additional effort is necessary to engineer and implement new protection approaches that can overcome the limitations of protection systems in future microgrids.

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