scholarly journals Mathematical Explanations of a Paradox Observed in a HVAC (High Voltage Alternating Current) Untransposed Overhead Line

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 734
Author(s):  
Adrian Pană ◽  
Alexandru Băloi ◽  
Florin Molnar-Matei
Keyword(s):  
High Voltage ◽  
Real Line ◽  
Power Flow ◽  
Alternating Current ◽  
Operating Conditions ◽  
Overhead Line ◽  
The Real ◽  
Overhead Lines ◽  
Mathematical Explanations ◽  
Load Conditions

The constructive asymmetry of the untransposed overhead lines of a high voltage alternating current is the cause of a great number of difficulties in their operation and modeling. In order to model the operating regimes of such lines, the symmetrical component method, based on constructive symmetry and thus the symmetry of the equivalent phase parameters, is inappropriate, which is why many research papers have been dedicated to either setting up improved modeling methods or to returning to phase coordinate modeling. This paper intends to justify a paradox found on some untransposed overhead lines of a high voltage alternating current during the no-load operating conditions by performing phase coordinate modeling. In such a situation, the transmission or distribution operators measured significant negative values for the active powers on one or two phases at the beginning of the lines. Considering the case of a real untransposed overhead line operating under no-load conditions, the paper starts from presenting the recorded electrical values. Then, the paper moves on to outlining the Carson’s simplified computing relations for calculating the series and shunt primitive equivalent parameters and Kron’s transformation relationships for calculating the phase equivalent parameters. After applying them to the real line, the calculation of the power flow for the no-load operating conditions, which is applied to an equivalent scheme of the line consisting of nine identical octopoles, is performed. Both the untransposed line and its transposed variant are studied here. The values of the electrical amounts obtained by the calculation for the untransposed line are basically similar to those obtained by measuring on the real line, which gives a mathematical confirmation of the so-called paradox. Its occurrence represents the effect of the asymmetry of the equivalent phase capacities, which causes a redistribution of the active powers between the phases of the network to which the overhead line operating in no-load conditions is connected.

scholarly journals An algorithm to calculate feasible operating conditions of electrical network, given overhead conductor temperature and sag constraints

2018 ◽  
Vol 58 ◽  
pp. 02015
Author(s):  
Yekaterina Popova ◽  
Oleg Voitov ◽  
Lyudmila Semenova
Keyword(s):  
Steady State ◽  
Environmental Factors ◽  
Air Temperature ◽  
Heat Balance ◽  
Operating Conditions ◽  
Electrical Network ◽  
Overhead Line ◽  
Algorithm Performance ◽  
Overhead Lines ◽  
Conductor Temperature

The paper presents an algorithm to calculate feasible steady-state conditions of an electrical network. A distinctive feature of the calculation is the consideration of constraints on the temperature of bare conductor and the clearance of a controlled span of overhead line. This consideration is based on forming and solving an equation of conductor heat balance to calculate the conductor temperature depending on the current flowing through the conductor and environmental factors, including the actual values of air pressure and air temperature. The paper presents the results of numerical calculations performed for individual overhead lines and for a test 16-node scheme of electrical network. The results illustrate the algorithm performance and the importance of considering the above constraints.

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 The influence of ground wires on the resistance and reactance of high voltage overhead power lines

2021 ◽  
Vol 11 (2) ◽  
pp. 85-90
Author(s):  
Nikola Krstić ◽  
Dragan Tasić ◽  
Dardan Klimenta
Keyword(s):  
High Voltage ◽  
Power Flow ◽  
Operating Conditions ◽  
Protection System ◽  
Power Lines ◽  
Symmetric System ◽  
Power Flow Calculation ◽  
Flow Calculation ◽  
Longitudinal Impedance ◽  
Overhead Power Lines

In this paper, the influence of ground wires on the resistance and reactance (longitudinal impedance) of high voltage overhead power lines (OPLs) is considered and the method for its calculation is described in detail. This is important considering the power flow calculation and the design of the protection system of OPLs, especially those which use distance relays. In addition to symmetric, asymmetric operating conditions of OPLs are also studied, for the analysis of which symmetric components are used. Specifically, this meant the calculation of longitudinal impedances of OPL for positive, negative and zero sequences in each considered case. Special attention is paid to the symmetric system with zero sequences, because the influence of ground wires on the change of longitudinal impedance of OPLs is the greatest in that case. The cases of OPLs with one (110 kV OPL) and two (400 kV OPL) ground wires are considered, using the values o f their parameters that can be found in real systems. Values of longitudinal impedances, obtained with and without ground wires influence or the influence of some of their parameters, are compared, based on which appropriate conclusion is made.

The properties of Bessel-type fractional derivatives and integrals

2016 ◽  
pp. 3973-3982
Author(s):  
V. R. Lakshmi Gorty
Keyword(s):  
Fractional Order ◽  
Real Line ◽  
Computer Algebra System ◽  
Fractional Derivatives ◽  
Graphical Representation ◽  
Fractional Integrals ◽  
The Real ◽  
Fractional Derivatives And Integrals ◽  
Half Axis ◽  
Derivatives Of

The fractional integrals of Bessel-type Fractional Integrals from left-sided and right-sided integrals of fractional order is established on finite and infinite interval of the real-line, half axis and real axis. The Bessel-type fractional derivatives are also established. The properties of Fractional derivatives and integrals are studied. The fractional derivatives of Bessel-type of fractional order on finite of the real-line are studied by graphical representation. Results are direct output of the computer algebra system coded from MATLAB R2011b.

The choice of optimum cross section for overhead line by economic intervals' method

2011 ◽  
Vol 28 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Svetlana Guseva ◽  
Lubov Petrichenko
Keyword(s):  
Cross Section ◽  
Current Density ◽  
Uncertain Information ◽  
Overhead Line ◽  
Market Conditions ◽  
Overhead Lines ◽  
Mathcad Software

The choice of optimum cross section for overhead line by economic intervals' methodIn this paper an approach to choosing the optimum cross section for overhead line in conditions of incomplete and uncertain information is considered. The two methods of such choice are presented: method of economic current density and economic intervals' method. The correction of the economic intervals method is offered under market conditions of costs. As example 20 kV and 110 kV overhead lines with aluminum, copper and ferroaluminum wires are selected. Universal nomograms with different standard cross section are calculated and constructed. The graphics using Mathcad software are offered.

Power Test System Development and Dynamic Performance State Estimation Based on Hub Motor Vehicle

2020 ◽  
Vol 13 (2) ◽  
pp. 126-140
Author(s):  
Jing Gan ◽  
Xiaobin Fan ◽  
Zeng Song ◽  
Mingyue Zhang ◽  
Bin Zhao
Keyword(s):  
Real Time ◽  
Dynamic Performance ◽  
Test System ◽  
Operating Conditions ◽  
Motor Vehicles ◽  
Maximum Speed ◽  
Performance Parameters ◽  
Power Performance ◽  
Power Test ◽  
The Real

Background: The power performance of an electric vehicle is the basic parameter. Traditional test equipment, such as the expensive chassis dynamometer, not only increases the cost of testing but also makes it impossible to measure all the performance parameters of an electric vehicle. Objective: A set of convenient, efficient and sensitive power measurement system for electric vehicles is developed to obtain the real-time power changes of hub-motor vehicles under various operating conditions, and the dynamic performance parameters of hub-motor vehicles are obtained through the system. Methods: Firstly, a set of on-board power test system is developed by using virtual instrument (Lab- VIEW). This test system can obtain the power changes of hub-motor vehicles under various operating conditions in real-time and save data in real-time. Then, the driving resistance of hub-motor vehicles is analyzed, and the power performance of hub-motor vehicles is studied in depth. The power testing system is proposed to test the input power of both ends of the driving motor, and the chassis dynamometer is combined to test so that the output efficiency of the driving motor can be easily obtained without disassembly. Finally, this method is used to carry out the road test and obtain the vehicle dynamic performance parameters. Results: The real-time current, voltage and power, maximum power, acceleration time and maximum speed of the vehicle can be obtained accurately by using the power test system in the real road experiment. Conclusion: The maximum power required by the two motors reaches about 9KW, and it takes about 20 seconds to reach the maximum speed. The total power required to maintain the maximum speed is about 7.8kw, and the maximum speed is 62km/h. In this article, various patents have been discussed.

AN OSCILLATION FUNCTION ON THE REAL LINE

2000 ◽  
Vol 26 (1) ◽  
pp. 237
Author(s):  
Duszyński
Keyword(s):  
Real Line ◽  
The Real
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