Application of the Superposition Method for Fault Location in Medium Voltage Networks

Medium-voltage networks are characterized by a long length and high degree of wear. Isolation of a failed network section requires significant time expenditures, a circumstance that makes accurate and fast determination of the fault location a topical problem. In view of specific features of emergency modes in medium voltage networks, the development of precise algorithms for fault location in the case of single and double ground faults involves certain difficulties. The arbitrary configuration of electrical networks, specific neutral grounding conditions, and lack of the possibility to perform multilateral measurements of emergency parameters complicate the development of universal fault location algorithms. In addition, technical solutions are as a rule limited by the need of using one-sided measurements of emergency mode parameters. The considered algorithms for calculating the distance to the fault location involve the use of emergency and normal electric network mode parameters. The proposed algorithms are based on using the superposition method and do not depend on the electrical network topology; they make it possible to decrease the influence of the current distribution pattern in lines with branches, as well as the influence of the load operating conditions on the accuracy of calculating the distance to fault location. The application of the proposed algorithms is justified by the results of simulation and makes it possible to calculate the distance to the fault location in networks with insulated neutral with high accuracy.

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Research of the possibility of application of the superposition method for implementation of algorithms for determining damage locations in networks with isolated neutral

E3S Web of Conferences ◽

10.1051/e3sconf/202021601033 ◽

2020 ◽

Vol 216 ◽

pp. 01033

Author(s):

A.L. Kulikov ◽

V.Ju Osokin ◽

D.I. Bezdushniy ◽

A.A. Loskutov

Keyword(s):

Simulation Modeling ◽

Fault Location ◽

Single Phase ◽

Superposition Method ◽

Electrical Networks ◽

Medium Voltage ◽

Arbitrary Configuration ◽

Isolated Neutral ◽

Technical Solutions ◽

Emergency Mode

It is difficult to develop precise algorithms for determining fault locations for single-phase and double earth faults due to the features of emergency modes in medium voltage networks of 6-35 kV. The arbitrary configuration of electrical networks complicates the development of universal fault locations algorithms and, as a rule, technical solutions are limited by the need to use one-way measurements of emergency mode parameters. The article discusses new topology independent fault location algorithms that involve the use of the superposition method. The application of the proposed algorithms is justified by the results of simulation modeling and will allow implementation of calculating the distance to the fault in networks with isolated neutral with high accuracy.

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Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current

Energies ◽

10.3390/en14051330 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1330

Author(s):

Dumitru Toader ◽

Marian Greconici ◽

Daniela Vesa ◽

Maria Vintan ◽

Claudiu Solea

Keyword(s):

Fault Location ◽

Single Phase ◽

Analytical Calculation ◽

Electrical Network ◽

Fault Current ◽

Electrical Networks ◽

Medium Voltage ◽

Ground Fault ◽

Fault Currents ◽

Petersen Coil

Settings of protection are essential to ensure the sensitivity and selectivity needed to detect defects. Making the correct settings requires the calculation of the fault currents with as little error as possible. Fault currents are influenced by the parameters of the electrical networks, including the state of the insulation and the Petersen coil, which changes during their operation electrical networks. This paper analyzes how the insulation parameters of medium voltage power lines, the parameters of the Petersen coil used to treat the neutral of the medium voltage electrical network and the value of the resistance at the fault location influence the fault current in the case of a single-phase fault. The large number of single-phase faults that occur in medium voltage electrical networks justifies this analysis. The symmetrical components method was used to calculate the fault current. The results obtained by calculation were verified experimentally by causing a single-phase-to-ground fault in a real medium voltage network. The paper presents the situations in which the analytical calculation of the single-phase-to-ground fault current can lead to inadmissibly large errors, even over 50%, but also the situations in which the errors fall below 3%.

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Predicting the influence of the non-sinusoidal network mode on power transformers

E3S Web of Conferences ◽

10.1051/e3sconf/201911404005 ◽

2019 ◽

Vol 114 ◽

pp. 04005

Author(s):

Ngo Van Cuong ◽

Lidiia I. Kovernikova

Keyword(s):

Service Life ◽

Electric Power ◽

Power Quality ◽

Electrical Equipment ◽

Operating Conditions ◽

Transformer Oil ◽

Power Transformers ◽

Electrical Network ◽

Electrical Networks ◽

Current Harmonics

The parameters of electrical network modes often do not meet the requirements of Russian GOST 32144-2013 and the guidelines of Vietnam. In the actual operating conditions while there is the non-sinusoidal mode in electrical networks voltage and current harmonics are present. Harmonics result in overheating and damage of power transformers since they cause additional active power losses. Additional losses lead to the additional heat release, accelerating the process of insulating paper, transformer oil and magnetic structure deterioration consequently shortening the service life of a power transformer. In this regard there arises a need to develop certain scientific methods that would help demonstrate that low power quality, for instance could lead to a decrease in the electrical equipment service life. Currently we see a development of automated systems for continuous monitoring of power quality indices and mode parameters of electrical networks. These systems could be supplemented by characteristics calculating programs that give out a warning upon detection of the adverse influence of voltage and current harmonics on various electrical equipment of both electric power providers and electric power consumers. A software program presented in the article may be used to predict the influence of voltage and current harmonics on power transformers.

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Nonlinear load modeling for analysis of non-sinusoidal conditions in electrical networks based on measurements of harmonic parameters

Energy Systems Research ◽

10.38028/esr.2021.03.0001 ◽

2021 ◽

pp. 5-20

Author(s):

L. Kovernikova ◽

V.C. Luong

Keyword(s):

Electrical Equipment ◽

Distribution Functions ◽

Operating Conditions ◽

Electrical Network ◽

Electrical Networks ◽

Nonlinear Loads ◽

Nonlinear Load ◽

Current Harmonics ◽

Load Models ◽

Nonlinear Devices

Non-sinusoidal conditions in electrical networks need to be calculated for their control and development of technical measures to maintain harmonic parameters according to the requirements of regulatory documents. These calculations are impossible without electrical network and nonlinear load models that adequately reflect them in computational programs. Nonlinear load models have been developed for a long time. Some studies present general modeling principles and models of various nonlinear devices. Others consider some nonlinear devices as equivalent nonlinear loads connected to low and medium voltage networks. A whole host of high-power nonlinear electrical equipment is connected to high voltage networks. Modeling nonlinear loads connected to these networks is a problem. Research of measured parameters of harmonic conditions in electrical networks has shown that they are random values. The probabilistic nature is determined by the network configuration, a range of network components, the number of nonlinear loads, wave and frequency properties of the network, harmonic source phase currents, voltage at terminals of nonlinear electrical equipment, changes in operating conditions and load power, and many other factors. Nonlinear loads can only be modeled based on the measurements of parameters of harmonic conditions due to their unpredictability. The paper presents an overview of existing methods for modeling nonlinear loads, a methodological approach to modeling nonlinear loads based on measured parameters, an algorithm for modeling harmonics of active and reactive currents, a computational program algorithm designed to identify distribution functions of measured current harmonics, and modeling results for current harmonics of railway transformers supplying power to electric locomotives.

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DEVELOPMENT OF A MATHEMATICAL MODEL OF TRANSITIONAL PROCESSES IN THE ELECTRICAL NETWORK IN PHASE COORDINATES

Bulletin of the National Technical University "KhPI". Series: Energy: Reliability and Energy Efficiency ◽

10.20998/2224-0349.2020.01.08 ◽

2020 ◽

pp. 56-60

Author(s):

S. M. Lebedka ◽

M. V. Petrovskyi ◽

I. M. Diahovchenko

Keyword(s):

Mathematical Model ◽

Discrete Models ◽

Transient Processes ◽

Electrical Network ◽

System Of Equations ◽

Electrical Networks ◽

Electromagnetic Transient ◽

Phase Coordinates ◽

Arbitrary Configuration ◽

Three Phase

Distribution electrical networks of great length are characterized by a high order of the system of equations of electromagnetic transients. To improve the efficiency of modelling such networks, it is necessary to develop formalized procedures that provide automation of both the solution and the formation of systems of equations using modern computer technology. To simplify the development of mathematical models, transformations are used to move from a real three-phase network to other coordinate systems, but this is achieved at the expense of additional restrictions. To solve the problems of choosing and increasing the efficiency of means for limiting currents and overvoltages during transient processes in electrical networks, it is necessary to have a model reflecting a number of features, both of the networks themselves, and of the transient processes occurring in them. This is implemented in a model based on the representation of network elements not by single-phase equivalents, but by equations in phase coordinates. These equations contain the parameters of the network elements (active resistances, own and mutual inductances and capacitances) and the parameters of its mode (currents, voltages, phase powers), corresponding to the real physical parameters of electrical systems. A mathematical model of electromagnetic transient processes in an electrical network in phase coordinates has been developed. Calculation of the transient process when using the implicit method and representing the three-phase elements at the integration step by discrete models makes it possible to reduce the solution of a system of differential equations to multiple formation and solution of a system of equations. The diakoptic method for studying complex systems was developed, which was used to develop a mathematical model of electromagnetic transient processes in a three-phase electrical network. The proposed form of representation of discrete models of three-phase multipoles allows one to formalize both the solution procedure and the procedure for drawing up equations of transient processes for three-phase circuits of electrical networks of arbitrary configuration. Prospects for further research are computational experiments to study electromagnetic transient processes during ground faults in electrical networks of arbitrary configuration with various neutral modes and means of limiting currents and overvoltages.

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Analysis of the influence of non-sinusoidal and unbalanced network modes on induction motors

E3S Web of Conferences ◽

10.1051/e3sconf/202128901002 ◽

2021 ◽

Vol 289 ◽

pp. 01002

Author(s):

Ngo Van Cuong ◽

Lidiia I. Kovernikova

Keyword(s):

Power Systems ◽

Power Quality ◽

Induction Motors ◽

Electrical Power ◽

Electrical Energy ◽

Operating Conditions ◽

Premature Aging ◽

Electrical Network ◽

Electrical Networks ◽

Electrical Power Systems

The parameters of electrical network modes do not correspond the requirements GOST 32144-2013 of Russian and the National technical regulation of Vietnam. In real operating conditions in electrical networks in non-sinusoidal and unbalanced modes there are harmonic components of voltages and currents as well as voltages and currents of negative sequence. They cause additional losses of active power, which leads to additional heating and causes premature aging of the insulation, and as the result, the reduction in the service life of induction motors. Currently, we see that the process of formation of intelligent electrical power systems is underway. Systems for continuous monitoring of power quality indices and parameters of electrical systems modes are being developed. These systems can be supplemented with programs for calculating characteristics that issue the warning when the unfavorable influence of the parameters of non-sinusoidal and unbalanced modes is detected on various electrical equipment of both electrical power systems and consumers of electrical energy. The paper provides an overview of the characteristics used to analyze, assess and predict the influence of poor power quality associated with non-sinusoidal and unbalanced of currents and voltages on induction motors. A computer program was developed to calculate these characteristics. The program was used to study the influence of non-sinusoidal and unbalanced modes on the induction motors of the coal sorting plant of the Vietnamese company “Cua Ong-Vinacomin”.

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Analysis of Internal Overvoltages in Transformer Windings during Transients in Electrical Networks

Energies ◽

10.3390/en13102644 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2644 ◽

Cited By ~ 2

Author(s):

Jakub Furgał ◽

Maciej Kuniewski ◽

Piotr Pająk

Keyword(s):

Power Systems ◽

Electromagnetic Waves ◽

Power Transformer ◽

Electrical Power ◽

Operating Conditions ◽

Electromagnetic Transients ◽

Electrical Network ◽

Electrical Networks ◽

Insulation Systems ◽

The Impact

Due to the increasing requirements for the reliability of electrical power supply and associated apparatus, it is necessary to provide a detailed analysis of the overvoltage risk of power transformer insulation systems and equipment connected to their terminals. Exposure of transformer windings to overvoltages is the result of the propagation condition of electromagnetic waves in electrical networks and transformer windings. An analysis of transformer winding responses to transients in power systems is of particular importance, especially when protection against surges by typical overvoltage protection systems is applied. The analysis of internal overvoltages in transformers during a typical transient related to switching operations and selected failures is of great importance, particularly to assess the overvoltage exposure of insulation systems in operating conditions. The random nature of overvoltage phenomena in electrical networks implies the usage of computer simulations for the analysis of overvoltage exposures of electrical devices in operation. This article presents the analysis of the impact of transient phenomena in a model of a medium-voltage electrical network during switching operations and ground faults on overvoltages in the internal insulation systems of transformer windings. The basis of the analysis is simulations of overvoltages in the windings, made in the Electromagnetic Transients Program/Alternative Transients Program (EMTP/ATP) using a model with lumped parameters of transformer windings. The analysis covers the impact of the cable line length and the ground fault resistance value on internal overvoltage distributions.

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