INDIRECT TEST CIRCUIT FOR TESTING HIGH VOLTAGE FUSES IN OVERLOAD CONDITIONS

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.

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The Analysis on Influence of Test Error of Voltage Transformer Primary Test Circuit Causes on GIS and the Improvement of Test Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.2689 ◽

2013 ◽

Vol 734-737 ◽

pp. 2689-2693

Author(s):

Zhi Long Zhang ◽

Hong Su

Keyword(s):

High Voltage ◽

Low Voltage ◽

Coastal Region ◽

Calculation Model ◽

Test Method ◽

Voltage Transformer ◽

Long Distance ◽

Test Error ◽

Test Circuit ◽

Primary Test

Recently, the Gas Insulated Station (GIS), small floor area ,convenient maintenance and good security ,is applied more and more extensively, but it becomes difficult to calibrate the error of measuring voltage transformer in main circuit on GIS with the application. According to the regulations, high voltage must be imposed on high voltage incoming line bushing in the high voltage test to voltage transformer. However, primary test circuit is long because of the long distance between the high voltage incoming line bushing and the tested voltage transformer, which makes the loop impedance large, so the measuring veracity is affected. In this paper, the Finite Element Method (FEM) is used to determine calculation model of each element on GIS station combined with 110kV station called rocket base in new coastal region, then Electromagnetic Transient Program (EMTP) is used to design the calculation model of the GIS station. The influence of test error of voltage transformer the primary test circuit causes is analyzed in theory. The experiment that the voltage imposed on low voltage side is used to measure the error of high voltage side is made to verify accuracy of the method in this paper.

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Thyristor Arc Eliminator for Protection of Low Voltage Electrical Equipment

Energies ◽

10.3390/en12142749 ◽

2019 ◽

Vol 12 (14) ◽

pp. 2749 ◽

Cited By ~ 1

Author(s):

Karol Nowak ◽

Jerzy Janiszewski ◽

Grzegorz Dombek

Keyword(s):

Lower Cost ◽

Low Voltage ◽

Short Circuit ◽

Electrical Equipment ◽

Power Network ◽

System Operation ◽

Test Circuit ◽

Wide Range ◽

Short Circuit Currents ◽

Electrical Apparatus

The paper presents the layout of two opposing thyristors working as an Arc Eliminator (AE). The presented solution makes it possible to protect an electrical apparatus against the effects of an arcing fault. An Arc Eliminator is assumed to be a device cooperating with the protected apparatus. Thyristors were used because of their speed of operation and a relatively lower cost compared to other semiconductors with the same current-carrying capacity. The proposed solution, as one of the few currently available, makes it possible to eliminate the fault arc—both at short-circuit currents and current values to which overcurrent protections do not react. A test circuit was designed and made to study the effectiveness of the thyristor arc eliminator. A series of tests was carried out with variable impedance in the arc branch, including the influence of circuit inductance on arc time. It was found that the thyristor arc eliminator effectively protects devices powered from a low voltage power network against the effects of a fault or arc fault. The correctness of system operation for a wide range of impedance changes in the circuit feeding the arc location was demonstrated.

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

Vestnik of Kazan state agrarin university ◽

10.12737/article_5b350932963a26.64641811 ◽

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.

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

International Journal of Wildland Fire ◽

10.1071/wf08128 ◽

2009 ◽

Vol 18 (6) ◽

pp. 722 ◽

Cited By ~ 6

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.

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

Volume 2: Plant Systems, Structures, Components, and Materials; Risk Assessments and Management ◽

10.1115/icone26-82177 ◽

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.

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Generate Various Parameters Of Trv Envelope Synthetic Test Circuit

Turkish Journal of Computer and Mathematics Education (TURCOMAT) ◽

10.17762/turcomat.v12i2.1345 ◽

2021 ◽

Vol 12 (2) ◽

pp. 1348-1356

Author(s):

Jagadeesh Peddapudi, Et. al.

Keyword(s):

High Voltage ◽

Short Circuit ◽

Circuit Breaker ◽

Circuit Breakers ◽

Force System ◽

Transient Recovery Voltage ◽

Test Circuit ◽

Synthetic Test ◽

Recovery Voltage ◽

The Impact

The most basic transient a circuit breaker needs to suffer during its activity is the transient recovery voltage (TRV), started by the electric force system as a characteristic response on flow interference. To test high voltage CBs, direct testing utilizing the force system or short out alternators are not practical. The testing of high voltage Circuit Breakers (CBs) of bigger limit requires huge limit of testing station. An equal infusion of short out current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is examined. Transient recovery voltage is made by a capacitor bank and is applied to CB. An optical set off spark gap has been utilized to interrupt short circuit and to introduce of transient recovery voltage that is applied across the contacts of circuit breaker. Transient recovery voltage examination can never be done totally, as the advancement of circuit breaker development and organization configuration goes on. The most widely recognized way to deal with TRV examination is concerning the supposed planned TRV, in which a suspicion of dismissing association between circuit breaker itself and the innate system recovery voltage is being made. Notwithstanding, it actually is by all accounts qualified to examine what circuit breaker means for transient recovery voltage. An ideal grouping to open/close of reinforcement test article and helper circuit breakers inside suitable chance to infuse of recovery voltage. The impact of reactance of inductive flaw current limiter just as distance to blame in short line issue condition on pace of ascent of recovery voltage. A 4-boundaries TRV synthetic test circuit dependent on equal current infusion technique is planned and mimicked for testing 145kV rating circuit-breakers according to new TRV prerequisites given in IEC 62271-100.

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Study on Seismic Performance of UHV Transformer Based on Soil-structure Interaction

Journal of Physics Conference Series ◽

10.1088/1742-6596/2148/1/012020 ◽

2022 ◽

Vol 2148 (1) ◽

pp. 012020

Author(s):

Yaodong Xue ◽

Yongfeng Cheng ◽

Zhicheng Lu ◽

Zhubing Zhu ◽

Haibo Wang ◽

...

Keyword(s):

Seismic Response ◽

Seismic Performance ◽

High Voltage ◽

Shaking Table Test ◽

Low Voltage ◽

Great Influence ◽

Test Method ◽

Shaking Table ◽

Peak Acceleration ◽

Measuring Point

Abstract At present, the seismic performance of UHV transformers is mostly studied without considering the interaction between soil and superstructure. In practical engineering, the transformer is installed on the foundation slab buried in the soil. Under the action of earthquake, the interaction between the soil and the structure changes the earthquake response of the upper electrical structure. In order to study the influence of the interaction between soil and structure on the seismic performance of the transformer, the shaking table test method of simulated earthquake is used, and the shaking table test of UHV transformer with scale ratio of 1:4 is carried out in class I field conditions. The dynamic characteristics of the equipment and the seismic response of the bushing under different test conditions are obtained respectively. The test results show that when the peak acceleration is 1.2g, the acceleration response at each measuring point on the box is 1.63-1.92 times that when the peak acceleration is 0.4g. With the increase of seismic peak acceleration, the acceleration and strain increase of high voltage bushing are greater than that of medium and low voltage bushing, which has a great influence on the seismic response of high voltage bushing. The research conclusion can provide reference for substation engineering design.

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The Possibilities to Reduce Arc Flash Exposure with Arc Fault Eliminators

Energies ◽

10.3390/en14071927 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1927

Author(s):

Karol Nowak ◽

Jerzy Janiszewski ◽

Grzegorz Dombek

Keyword(s):

Electrode Material ◽

Low Voltage ◽

Short Circuit ◽

Electric Arc ◽

Risk Category ◽

Sudden Increase ◽

Technical Personnel ◽

Test Circuit ◽

Arc Flash ◽

Flash Exposure

This paper presents a method to limit the arc energy and hence the hazard risk category value according to IEEE 1584 by using a system of two oppositely connected multi-sectional thyristor branches. A test circuit for testing the effectiveness of a thyristor arc eliminator was designed and constructed. Arc ignition inside electrical switchgear can be a source of danger for technical personnel. The arc energy calculated according to the algorithms in IEEE 1584 can be significantly reduced by using multi-sectional arc eliminator MSAE. For the actual measuring object, the calculation of the hazardous arc flash zone and the hazard category was carried out for the system not equipped with an arc eliminator, and then the same was performed in a system with an arc eliminator. In parallel, the pressure inside the closed polyvinyl chloride (PVC) electrical box enclosure was measured and then compared with the calculated pressures that could occur during an arc fault. It was found that a Multi-Sectional Arc Eliminator (MSAE) effectively protects devices supplied from low voltage networks against the effects of short circuit or arc fault, such as the sudden increase of gas pressure inside the switchboard, which may cause it to break, significantly reduce the loss of electrode material, limit the spread of hot electrode material outside the switchgear, and also significantly reduces the energy of the electric arc.

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