Parameters Of Overhead Transmission Lines Research Articles

Assessment of reliability of an overhead transmission line with a split back-up phase

Transmission of electrical energy is the most important component of an electric power system. Optimization, modernization of the electric power transport system, increasing the capacity, as well as variability of connection arrangements, while maintaining the required level of reliability and safety, is regarded today as an urgent task for the energy industry as a whole. The article is devoted to the problem of determining the efficiency of the circuit design solution for a double-circuit three-phase power transmission line with an additional mode of operation — «with a split back-up phase» and determining its main reliability indicators. A circuit design solution for a double-circuit power transmission line with expansion of operating modes is presented in detail. The functional redundancy of the transmission line in accordance with the circuit design solution is based on switching of a conventional double-circuit power transmission line in the emergency mode to the single-circuit split-phase mode, which is the second working circuit. The ways of increasing the natural power of a double-circuit power transmission line are considered. The results of calculation of the capacity of a line with a split back-up phase and a comparison of the main parameters of overhead transmission lines with an additional mode of operation — with a split back-up phase — and power lines in conventional modes of operation, are presented. The results of calculations of reliability indicators are presented, such as the probable relative number of hours of interruption of power supply and the undersupply of electrical energy. A comparison of options have shown that the probable relative under-supply of the electric power of a double-circuit overhead transmission line with an additional operating mode — with a split back-up phase, is lower by approximately 13% than that of a conventional double-circuit power line, which will positively affect the maneuverability and reliability of the entire system.

Evaluation of Length, Dependent Earth Return Transmission-Line Parameters for Overhead Conductors in the Quasistatic Range

In this paper, a novel application of the matrix pencil method (MPM) is used to evaluate the length-dependent earth return parameters of overhead transmission lines in the quasistatic frequency range. The MPM is used to approximate the reflection coefficient by a series of complex exponentials, which allows the length-dependent transmission-line parameters to be evaluated in closed form. This methodology improves the accuracy of the length-dependent formulation when compared with the single image approximation used in previous publications, and can be applied to both parallel and angled overhead conductor configurations. Where large differences in results exist between the two methods, numerical integration confirms the accuracy of the MPM method. The proposed method can accurately evaluate the earth return parameters for conductors of arbitrary length and separations. This enables the proposed method to be applied to transmission-line configurations of all lengths, even in instances where the application of the per-unit method is not valid. This makes the length-dependent methodology ideal for generating transmission-line models from routing coordinates.

Analysis of Overhead Transmission Line Parameters with Uncertainty

Analysis of Overhead Transmission Line Parameters with Uncertainty

Algorithms and field experiences for estimating transmission line parameters based on fault record data

The impedance parameters of overhead transmission lines are fundamental input data for various power system studies. The data are traditionally calculated based on the structure information of a line. This study proposes a method for estimating the parameters using fault records captured by digital relays. The fault records are the unsynchronised voltage and current waveforms recorded at both ends of a line. One of the main contributions of this work is the use of the wave propagation speed equation to simplify the problem and to improve the estimation accuracy. As a result, both the positive and zero sequence parameters can be estimated using simple algorithms in a decoupled solution process. Simulation results show that the proposed approach has good accuracy. Finally, the method was applied to estimate the impedance data of several actual transmission lines based on the fault record data provided by a utility company.

Influence of frequency characteristics of soil parameters on ground-return transmission line parameters

Electromagnetic transient processes are strongly related to the parameters of transmission lines. With the ground return parameters considered, the frequency dependent parameters of transmission lines are highly dependent on the soil parameters, which include resistivity and dielectric permittivity. In this paper, with the measurement results of frequency variation of soil parameters, the influence of the frequency dependent soil parameters on the frequency dependent characteristics of the transmission line parameters were studied using the complex return plane method. According to the calculation results, the frequency characteristics of soil parameters have obvious influences on the parameters of overhead transmission lines. The influences of the humidity, temperature and particle size of the soil on the ground-return parameters were also evaluated.

Behavior of Overhead Transmission Line Parameters on the Presence of Ground Wires

Initially this paper shows the ground wire reduction process for generic multiphase transmission lines and after, the ground wire reduction process for a specific 440-kV three-phase overhead transmission line. Following this, the influence of the ground wire reduction process considering two situations is shown: first, considering frequency independence and second, when these parameters are considered as frequency dependent. This paper presents analytical results for generic multiphase transmission lines. For a specific 440-kV three-phase overhead transmission line, analytical and graphic results are shown considering real data for every frequency between 10 Hz and 1 MHz.

Mathematical verification of Dubanton's simplified calculation of overhead transmission line parameters and its physical interpretation

For the calculation of overhead transmission line impedances with earth return Dubanton has given explicit formulae based on the assumption, that the earth return current is concentrated in a plane being in a fictitious complex depth. In this paper the authors give the mathematical basis started from Carson's formulae and the physical interpretation of this heuristic method.