scholarly journals STUDY OF THE NATURE OF OVERVOLTAGES IN THE ELECTRICAL NETWORK ARISING FROM VOLTAGE TRANSFORMERS

2021 ◽  
pp. 28-36
Author(s):  
Oleksii Hanus ◽  
Kostiantyn Starkov
Keyword(s):  
Transient Process ◽  
Distribution System ◽  
Forced Oscillations ◽  
Electrical Network ◽  
Secondary Circuit ◽  
Electric Networks ◽  
Voltage Transformer ◽  
Secondary Resistance ◽  
Non Linear ◽  
Secondary Winding

A non-linear dynamic mathematical model of voltage transformer has been considered and overvoltages arising on the elements of voltage transformer equivalent circuit during transient processes have been investigated. The influence of voltage transformer secondary circuit capacitance on overvoltage multiplicity in the primary circuits and the duration of transients has been determined. The advantages of approximation of nonlinearity of voltage transformers by hyperbolic sine are used. Mathematical expressions determining the nature of changes in the forced and free components of the transient process in an electrical network with a voltage transformer have been obtained. It is shown that with the increase of the electric network capacitance the duration of the transition process damping increases and the frequency of the forced oscillations and the level of overvoltage decrease. It is proved that even small, in comparison with the primary nominal sinusoidal voltage, aperiodic components of the voltage transient process can lead to significant overvoltages during voltage transformer outages. It has been substantiated that both the secondary resistance and the switching torque influence the overvoltage multiplicity arising in the primary winding of voltage transformers. It is shown that the closed secondary winding worsens the disconnection process of non-linear inductance of voltage transformers. The values to which overvoltages increase in this case are determined. According to the results of calculations it is determined that with open secondary winding of voltage transformers the duration of transient process significantly increases. It has been found that the decrease of frequency of forced oscillations, which occurs in this case, is accompanied by an increase of currents in the primary winding of the voltage transformer, which is dangerous in terms of thermal stability of the winding insulation. It is shown, that closing the secondary winding of voltage transformers leads to significant reduction of transient damping time. It is suggested that this algorithm can be used to provide a rapid breakdown (suppression) of ferroresonant processes. The effectiveness of such a measure of stopping of ferroresonance processes as short-term shunting of secondary winding of voltage transformers has been investigated. The correlation of parameters of electric networks (capacity of busbar sections, nonlinearity of characteristics of voltage transformers, disconnection torque, etc.) at which ferroresonance process may occur and consideration of which may allow, in terms of prevention of ferroresonance processes, to identify substations (electric networks) that require more detailed research has been determined. The results of analytical studies were tested in the electric networks of JSC "Kharkivoblenergo" and used in the electricity distribution system for the selection of specific voltage transformers for certain configurations of electrical networks.

scholarly journals Loss Analysis Due to Influence of Harmonics in a Distribution System

2021 ◽  
Vol 19 ◽  
pp. 402-406
Author(s):  
R.M. Soares ◽  
◽  
M. E. Oliveira ◽  
M. A. A. Freitas ◽  
G.P. Viajante ◽  
...  
Keyword(s):  
Distribution System ◽  
Test System ◽  
Electrical Network ◽  
Joule Effect ◽  
Loss Analysis ◽  
Non Linear ◽  
Network Simulations ◽  
Harmonic Components ◽  
Load Shape ◽  
Made In

The electrical system is subject to rules to guarantee a standard, where several factors can reduce its quality. This can lead to undesirable consequences, such as increased electrical losses in the distribution. As the technology advances and the constant presence of non-linear loads, the electrical network is subject to harmonic distortions that increase the effective value of the current, resulting in inconvenient effects, such as increased losses. In another words, a bigger fraction of the energy is lost by Joule effect and a smaller fraction came to the final consumers. In Brazil, the regulatory agency, in its recommendations, does not consider the effect of harmonic components, obtaining lower results for losses. So, to analyze the influence of these distortions on the operation of a distribution network, simulations were done with the test system LVTestCaseNorthAmerican, with 390 buses. Three distinct climatic cases were analysed, each with a load shape generated from fuzzy logic, all considering the presence of non-linear loads. The simulations were made in OpenDSS, and the losses demonstrated for the three situations. Finally, the importance of considering these distortions in the calculation of losses is discussed.

scholarly journals Optical Voltage Transformer Based on FBG-PZT for Power Quality Measurement

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2699
Author(s):  
Marceli N. Gonçalves ◽  
Marcelo M. Werneck
Keyword(s):  
Power System ◽  
Power Quality ◽  
Distribution System ◽  
Electrical Power ◽  
Quality Measurement ◽  
Pockels Effect ◽  
Electrical Power System ◽  
Voltage Transformer ◽  
Technical Literature ◽  
Distribution Lines

Optical Current Transformers (OCTs) and Optical Voltage Transformers (OVTs) are an alternative to the conventional transformers for protection and metering purposes with a much smaller footprint and weight. Their advantages were widely discussed in scientific and technical literature and commercial applications based on the well-known Faraday and Pockels effect. However, the literature is still scarce in studies evaluating the use of optical transformers for power quality purposes, an important issue of power system designed to analyze the various phenomena that cause power quality disturbances. In this paper, we constructed a temperature-independent prototype of an optical voltage transformer based on fiber Bragg grating (FBG) and piezoelectric ceramics (PZT), adequate to be used in field surveys at 13.8 kV distribution lines. The OVT was tested under several disturbances defined in IEEE standards that can occur in the electrical power system, especially short-duration voltage variations such as SAG, SWELL, and INTERRUPTION. The results demonstrated that the proposed OVT presents a dynamic response capable of satisfactorily measuring such disturbances and that it can be used as a power quality monitor for a 13.8 kV distribution system. Test on the proposed system concluded that it was capable to reproduce up to the 41st harmonic without significative distortion and impulsive surges up to 2.5 kHz. As an advantage, when compared with conventional systems to monitor power quality, the prototype can be remote-monitored, and therefore, be installed at strategic locations on distribution lines to be monitored kilometers away, without the need to be electrically powered.

scholarly journals Distribution system power quality compensation using a HSeAPF based on SRF and SMC features

2021 ◽  
Author(s):  
Akram Qashou ◽  
Sufian Yousef ◽  
Abdallah A. Smadi ◽  
Amani A. AlOmari
Keyword(s):  
Power Distribution ◽  
Distribution System ◽  
Reactive Power ◽  
Sliding Mode ◽  
Distribution Network ◽  
Harmonic Distortion ◽  
Phase Locked Loop ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Non Linear

AbstractThe purpose of this paper is to describe the design of a Hybrid Series Active Power Filter (HSeAPF) system to improve the quality of power on three-phase power distribution grids. The system controls are comprise of Pulse Width Modulation (PWM) based on the Synchronous Reference Frame (SRF) theory, and supported by Phase Locked Loop (PLL) for generating the switching pulses to control a Voltage Source Converter (VSC). The DC link voltage is controlled by Non-Linear Sliding Mode Control (SMC) for faster response and to ensure that it is maintained at a constant value. When this voltage is compared with Proportional Integral (PI), then the improvements made can be shown. The function of HSeAPF control is to eliminate voltage fluctuations, voltage swell/sag, and prevent voltage/current harmonics are produced by both non-linear loads and small inverters connected to the distribution network. A digital Phase Locked Loop that generates frequencies and an oscillating phase-locked output signal controls the voltage. The results from the simulation indicate that the HSeAPF can effectively suppress the dynamic and harmonic reactive power compensation system. Also, the distribution network has a low Total Harmonic Distortion (< 5%), demonstrating that the designed system is efficient, which is an essential requirement when it comes to the IEEE-519 and IEC 61,000–3-6 standards.

Harmonic Elimination Using STATCOM for SEIG Fed Induction Motor Load

2017 ◽  
Vol 8 (3) ◽  
pp. 1026
Author(s):  
Satyanarayana Gorantla ◽  
Goli Ravi Kumar
Keyword(s):  
Induction Motor ◽  
Distribution System ◽  
Load Current ◽  
Synchronous Reference Frame ◽  
Harmonic Elimination ◽  
Non Linear ◽  
Source Current ◽  
Motor Load ◽  
Non Linear Load ◽  
Induction Motor Load

Non-linear loads connected to distribution system induce harmonics in to source components and the presence of harmonics in source components affects the performance of other sensitive loads connected at the same point. Induction motor load for drive system should be operated with variable frequency and variable voltage for its speed control. To vary the voltage and frequency, induction motor is fed from an inverter. This total drive set-up constitutes non-linear load type and will be the source of harmonics. This paper depicts the suppression of harmonics with STATCOM in distribution system when induction motor load is fed from SEIG (singly excited inductin generator). STATCOM is controlled with simple synchronous reference frame theory and the results are shown for source current, load current. THD in source current and load current was also shown for the said system. System for single-phase and three-phase induction motor drive was developed and results are shown using MATLAB/SIMULINK software.

Free and Forced Oscillations of Magnetic Liquids Under Low-Gravity Conditions

2019 ◽  
Vol 87 (2) ◽  
Author(s):  
Álvaro Romero-Calvo ◽  
Gabriel Cano Gómez ◽  
Elena Castro-Hernández ◽  
Filippo Maggi
Keyword(s):  
Magnetic Fields ◽  
Forced Oscillations ◽  
Applied Mechanics ◽  
Low Gravity ◽  
Linear Dynamics ◽  
Spacecraft Design ◽  
Magnetic Liquids ◽  
Non Linear ◽  
Sloshing Damping

Abstract The sloshing of liquids in microgravity is a relevant problem of applied mechanics with important implications for spacecraft design. A magnetic settling force may be used to avoid the highly non-linear dynamics that characterize these systems. However, this approach is still largely unexplored. This paper presents a quasi-analytical low-gravity sloshing model for magnetic liquids under the action of external inhomogeneous magnetic fields. The problems of free and forced oscillations are solved for axisymmetric geometries and loads by employing a linearized formulation. The model may be of particular interest for the development of magnetic sloshing damping devices in space, whose behavior can be easily predicted and quantified with standard mechanical analogies.

scholarly journals A Novel Approach to Model a Gas Network

2019 ◽  
Vol 9 (6) ◽  
pp. 1047 ◽  
Author(s):  
Ali Ekhtiari ◽  
Ioannis Dassios ◽  
Muyang Liu ◽  
Eoin Syron
Keyword(s):  
Linear System ◽  
End Users ◽  
Load Flow ◽  
Electrical Network ◽  
Flow Equations ◽  
Gas Network ◽  
Wide Range ◽  
Non Linear ◽  
Novel Method ◽  
Non Linear System

The continuous uninterrupted supply of Natural Gas (NG) is crucial to today’s economy, with issues in key infrastructure, e.g., Baumgarten hub in Austria in 2017, highlighting the importance of the NG infrastructure for the supply of primary energy. The balancing of gas supply from a wide range of sources with various end users can be challenging due to the unique and different behaviours of the end users, which in some cases span across a continent. Further complicating the management of the NG network is its role in supporting the electrical network. The fast response times of NG power plants and the potential to store energy in the network play a key role in adding flexibility across other energy systems. Traditionally, modelling the NG network relies on nonlinear pipe flow equations that incorporate the demand (load), flow rate, and physical network parameters including topography and NG properties. It is crucial that the simulations produce accurate results quickly. This paper seeks to provide a novel method to solve gas flow equations through a network under steady-state conditions. Firstly, the model is reformulated into non-linear matrix equations, then the equations separated into their linear and nonlinear components, and thirdly, the non-linear system is solved approximately by providing a linear system with similar solutions to the non-linear one. The non-linear equations of the NG transport system include the main variables and characteristics of a gas network, focusing on pressure drop in the gas network. Two simplified models, both of the Irish gas network (1. A gas network with 13 nodes, 2. A gas network with 109 nodes) are used as a case study for comparison of the solutions. Results are generated by using the novel method, and they are compared to the outputs of two numerical methods, the Newton–Raphson solution using MATLAB and SAINT, a commercial software that is used for the simulation of the gas network and electrical grids.

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