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AC overhead lines through their constructive asymmetry causes significant unbalance of currents and asymmetry of voltages on the three phases of the network. These unbalances of the operating conditions are even higher as the lines has greater lengths and the transported powers are higher and is therefore primarily characteristic for the transmission lines. The article presents the results of numerical...
Voltage dips are one of the most important power quality problems. The major disadvantage in studying this phenomenon is the difficulty to obtain the necessary data. This disadvantage is to the fact that the phenomenon is random and monitoring must be carried out for long periods of time. In these conditions the paper proposes a three-phase voltage dips software generator, by means of which voltage...
The paper offers an answer to the question: a high voltage overhead line, operating in no load conditions, “generates” active power (energy)? In order to justify the answer, a case study on an untransposed 110 kV single circuit overhead line was used, for which the no load operating condition has been studied using phase amounts. For this goal, applying the modified Carson's equations and the Kron's...
Voltage dips are the most common voltage disturbance in electrical networks operation. A single phase dip is characterized by several amounts such as amplitude, phase shift, start point on wave and end point on wave. Given that electricity grids are three-phase grids and voltage dips can affect one, two or all three phases, researchers have proposed over time many methods of classifying them, which...
The increasing need to limit the harmonic pollution of electricity transmission networks, require the use of the harmonic impedance, as a primary tool of analysis. Using the general relations for calculating the harmonic impedance seen along an AC power line deducted under its modeling through a chain of two symmetric passive quadripols built with linear equivalent parameters, uniformly distributed,...
This paper presents general relations for calculation of harmonic impedance seen along an AC transmission overhead line. This is modeled by a chain of two symmetrical passive quadripoles corresponding to the segments that are on either side of the section of interest. Chain matrices of the two quadripoles are written by considering uniformly distributed line parameters and on their base, the expressions...
The paper presents a fuzzy approach for harmonic voltage level based on the linguistic prescription of power quality standard. Harmonic currents are mainly generated by industrial and residential loads with non-linear characteristics. Industrial loads which are a source of significant levels of harmonic distortion include power converters, variable speed drives, induction furnaces, arc furnaces. Some...
The paper presents a study comprising laboratory measurements for the evaluation of the harmonic amplification due to capacitor bank switching. The mathematical model of the amplification factors of the current flowing on the circuit elements is presented. Theoretical aspects, regarding the total harmonic distortion (THD) of the capacitor current computed using the amplification factor, are originally...
Capacitive shunt compensation of a three phase power distribution network is usually done to improve the voltage level in the network buses and / or to reduce the active power losses. Most often this compensation could be made also for network load balancing, which will also have a positive effect on voltage quality. For this, a shunt unbalance capacitive compensation is necessary. The compensation...
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