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 Ac loss modelling and measurement of superconducting transformers with coated-conductor Roebel-cable in low-voltage winding

2021 ◽  
Author(s):  
E Pardo ◽  
M Staines ◽  
Zhenan Jiang ◽  
N Glasson
Keyword(s):  
High Temperature ◽  
High Voltage ◽  
High Temperature Superconductor ◽  
Low Voltage ◽  
Ac Loss ◽  
Power Transformers ◽  
Coated Conductor ◽  
Real Power ◽  
Transformer Design ◽  
Loss Modelling

Power transformers using a high temperature superconductor (HTS) ReBCO coated conductor and liquid nitrogen dielectric have many potential advantages over conventional transformers. The ac loss in the windings complicates the cryogenics and reduces the efficiency, and hence it needs to be predicted in its design, usually by numerical calculations. This article presents detailed modelling of superconducting transformers with Roebel cable in the low-voltage (LV) winding and a high-voltage (HV) winding with more than 1000 turns. First, we model a 1 MVA 11 kV/415 V 3-phase transformer. The Roebel cable solenoid forming the LV winding is also analyzed as a stand-alone coil. Agreement between calculations and experiments of the 1 MVA transformer supports the model validity for a larger tentative 40 MVA 110 kV/11 kV 3-phase transformer design. We found that the ac loss in each winding is much lower when it is inserted in the transformer than as a stand-alone coil. The ac loss in the 1 and 40 MVA transformers is dominated by the LV and HV windings, respectively. Finally, the ratio of total loss over rated power of the 40 MVA transformer is reduced below 40% of that of the 1 MVA transformer. In conclusion, the modelling tool in this work can reliably predict the ac loss in real power applications. This is the Accepted Manuscript version of an article accepted for publication in 'Superconductor Science and Technology'. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/0953-2048/28/11/114008.

scholarly journals ANALYSIS OF CONSTRUCTION PRINCIPLES AND FUNCTIONALITY OF HIGH-VOLTAGE POWER TRANSFORMER CONDITION MONITORING SYSTEMS

2020 ◽  
pp. 61-70
Author(s):  
O. Ye. Pirotti ◽  
O. I. Balenko ◽  
V. O. Brechko ◽  
M. Yu. Huzin ◽  
Ju. G. Gontar
Keyword(s):  
High Voltage ◽  
Power Transformer ◽  
Short Circuit ◽  
Power Transformers ◽  
Electrical Network ◽  
Characteristic Functions ◽  
Economic Losses ◽  
Monitoring Systems ◽  
Measuring Instruments ◽  
Continuous Control

The article presents the results of analysis of construction principles and functionality of systems used to monitor the condition of high-voltage power transformers. The main functions of modern monitoring systems used to diagnose the condition of electrical network equipment both in Ukraine and abroad were analysed. Based on the analysis it was found that the most characteristic functions of monitoring systems are the detection of rapidly developing defects and continuous control of parameters necessary to predict and assess the state of equipment. It is shown that efficiency of monitoring systems will be determined by both accuracy of measuring instruments and adequacy of prediction and diagnostic models used in the process of measurement results processing. Requirements to the equipment which observance allows providing effective and economically reasonable use of monitoring systems are considered. The typical architecture of modern monitoring systems is analysed, the basic elements of such systems are considered. Basic levels of information flow processing within the systems for monitoring the condition of power transformers have been considered. A detailed description and justification for using diagnostic parameters for monitoring the main components of power transformers such as dissolved gases analysis, partial discharges, current, voltage and power of transformers, oil temperature in different transformer locations, switching and atmospheric overvoltages, short-circuit currents, deformation of windings and others are presented. The output parameters returned by monitoring systems are given. The introduction of modern systems and technical means of monitoring the condition of high-voltage power transformers will reduce the risks of emergencies and, consequently, reduce the economic losses associated with the replacement of damaged transformers and under-release of electrical energy.

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.

scholarly journals Internal short circuit mitigation of high-voltage lithium-ion batteries with functional current collectors

RSC Advances ◽  
2017 ◽  
Vol 7 (72) ◽  
pp. 45662-45667 ◽  
Author(s):  
Meng Wang ◽  
Yang Shi ◽  
Daniel J. Noelle ◽  
Anh V. Le ◽  
Hyojung Yoon ◽  
...  
Keyword(s):  
Lithium Ion Batteries ◽  
High Voltage ◽  
Short Circuit ◽  
Lithium Ion ◽  
Current Collector ◽  
Current Collectors ◽  
Internal Short Circuit

A functional current collector was developed to mitigate the internal short circuit in high-voltage lithium-ion batteries.

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.

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.

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