Ultra-high-voltage AC Transmission Line Research Articles

Analysis of Electromagnetic Environment in 1200 kV Single Circuit UHVAC Transmission Line by using FACE Software and Semi-empirical Formulae

In order to ensure efficient, bulk-power transmission over a long distance, need of increasing transmission-level voltage is being thought for the past many years. As a result, Ultra High Voltage AC (UHVAC) Transmission has appeared as a feasible solution. Many countries like Italy, Japan, USA, USSR, Brazil, China, India are developing technology for UHVAC transmission systems. Operating at 1000 kV (and above voltage level) demands careful design of transmission structure, switchgear, and equipment design. This paper presents a review of several studies carried out to analyze the electro-magnetic environment in UHVAC lines. The electromagnetic environment (Field, Audible Noise, Corona Loss, Radio Interference) of 1200 kV, Wardha-Aurangabad single-circuit transmission line, India is also evaluated using FACE (Field and Corona Effect) software. The results of the study of static AC field and magnetic field of the line are found to be within prescribed limits suggested by International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines.

Controlled Shunt Reactor for UHVAC System Reactive Power Control

Background: In this paper, a novel technique for reactive power management of the Ultra High Voltage (UHV) lines having voltage level of 1200 kV line and above is suggested. The UHV power grid has to frequently face the problems associated with the power- frequency and switching over-voltages. Methods: The technique involves the use of three-phase UHV Transformers as a Controlled Shunt Reactor (CSR) in combination with the use of a fixed reactor. The performance of the UHV AC transmission line is studied using PSCAD software and working of CSR is evaluated. Results: Standard parameters of the proposed Wardha-Aurangabad 1200 kV transmission line in India are considered for simulation model. The use of CSR has been found to be effective in mitigating system problems. Conclusion: The system can be used for maintaining voltage profile, resulting in enhancement of the reliability of the UHV transmission system.

Calculation of Power Frequency Electric Field Around Ultra-High Voltage AC Transmission Lines

Under the increasingly stringent situation of environmental protection management, it is necessary to research the distribution law of power frequency electric field around Ultra-High Voltage (UHV) AC transmission lines to provide technical basis for the design of transmission lines and the environmental impact assessment. Firstly the basic principle of equivalent charge method and its mathematical model are introduced in this paper. Then it is researched how to use equivalent charge method to analyze the electric field near the transmission lines. Based on the three-phase double-circuit overhead transmission line model, the influences of several factors on the power frequency electric field have been analyzed. These factors include the conductor-to-ground height, the phase sequence arrangement, the number of split conductors and the split spacing. Finally the frequency electric field of parallel UHV AC transmission lines is discussed. The results can provide reference for engineering design of UHV AC transmission lines.

Discharge voltage prediction of UHV AC transmission line–tower air gaps by a machine learning model

Full-scale discharge tests of transmission line–tower air gaps are costly and time-consuming, and they cannot exhaustively simulate all the gap configurations in practical engineering. In this paper, a machine learning model established by support vector machine is introduced to predict the switching impulse discharge voltages of the ultra-high-voltage (UHV) AC transmission line–tower air gaps. The three-dimensional finite element models of a UHV cup-type tower and a UHV compact transmission line were established for electric field calculation, and some features were extracted from the hypothetic discharge channel and the shortest path between the bundled conductor and the tower. These features under a given voltage were normalised and input to the SVM model, while the output is two binary values, respectively, representing gap withstanding or breakdown. Trained by experimental data of one type of the UHV transmission line–tower gaps, the SVM model is able to predict the discharge voltages of another gap type. The mean absolute percentage errors of the two engineering gap types, under different gap distances, are 8.31 and 4.86%, respectively, which are acceptable for engineering applications. The results provide a possible way to obtain the discharge voltages of complicated engineering gaps by mathematical calculations.

Audible Noise Performance of Conductor Bundles Based on Cage Test Results and Comparison with Long Term Data

A reasonable acoustic power formula is vital to precisely evaluate the audible noise (AN) level of ultra-high-voltage (UHV) AC power lines. This study derived a formula by taking several AN measurements under heavy rain conditions, using multiple conductor bundles in a UHV corona cage, and then subjecting these measured values to least squares fitting. The validity of the proposed formula was subsequently verified with statistical data obtained from two long-term stations at Henan and Hubei Province, which are located under the Jindongnan-Nanyang-Jingmen UHV AC transmission lines operating at 1000 kV. The deviation between the prediction and the long-term (L50) value was 0.76 dB for the Henan station and 0.17 dB for the Hubei station. It shows that the acoustic power formula derived in this paper is more accurate than the widely used Bonneville Power Administration formula, in which the corresponding deviations are much larger (3.07 and 2.53 dB).

Radio interference excitation function of conductor bundles based on cage test results and comparison with long‐term data

A reasonable excitation function is vital to make a precise evaluation about the radio interference (RI) level of ultra-high-voltage (UHV) AC power lines. To obtain this function, a large number of RI measurements in heavy rain condition were done using different conductor bundles in a corona cage. Then, the excitation function in heavy rain condition was obtained by least-square fitting these measured values. After that, the validity of this function was verified with the statistical data measured from the Hubei long-term station, which is located under the operating 1000 kV Jindongnan–Nanyang–Jingmen UHV AC transmission lines. It turns out that the deviation between the prediction and the long-term average value is 1.1 dB in heavy rain condition, and 1.3 dB in fair weather condition. In addition, the long-term data measured in Hubei Station show that the conversion laws of RI at different weather conditions in International Special Committee on Radio Interference (CISPR)18 are also applicable to 1000 kV UHV transmission lines.

Research on Helicopter Live-Line Work by Platform Method on 1000 kV UHV AC Transmission Lines

This paper focuses on the security condition of line worker during the implementation of helicopter live-line work by platform method on 1000 kV ultrahigh voltage (UHV) transmission lines. First, a model of helicopter live-line work is presented, and the electric field distribution of line worker when performing live-line work on 1000 kV UHV transmission lines is analyzed. Then, the capacitances between helicopter live-line work platform, transmission lines, and ground are obtained by energy method, and an equivalent circuit model is presented to analyze the current characteristic of bonding procedure. At the end of this paper, an experiment of helicopter live-line work is performed, the electric field distributions of line worker and the discharge current are measured and compared with simulation results, which will be used to judge the security condition of line worker and the feasibility of helicopter live-line work by platform method on 1000 kV UHV transmission lines.

Simplification Study of FE Model for 1000kV AC Transmission Line Insulator String Voltage and Grading Ring Surface Electric Field Distribution Calculation

The finite element model of the 1000kV Ultra High Voltage (UHV) AC transmission line porcelain insulator string voltage distribution and grading ring surface electric field distribution calculation has the characteristics of large size, complicated structure and various mediums. To insure the accuracy, related influencing factors should be considered to simplify the model reasonably for improving computational efficiency. A whole model and a simplified 3D finite element model of UHV AC transmission line porcelain insulator string were built. The influencing factors including tower, phase conductors, hardware fittings, yoke plate and phase interaction were considered in the analysis. And finally, the rationality of the simplified model was validated. The results comparison show that building a simplified model of three-phase bundled conductors within a certain length, simplifying the tower reasonably, omitting the hardware fittings and yoke plate and containing only single-phase insulator string model is feasible. The simplified model could replace the whole model to analyze the voltage distribution along the porcelain insulator string and the electric field distribution on the grading ring surface, and it can reduce the calculation scale, improve optimization efficiency of insulators string and grading ring parameters. DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.3833

Cotrolling Characteristic Analysis of Magnetically Controlled Shunt Reactor Based on Field-Circuit Coupled

In order to restrict over-voltage and compensate line charging power, there is a need to install high compensation shunt reactors in ultra-high voltage AC transmission lines. Due to the saturation characteristic of core limb during the working progress in the magnetically controlled shunt reactor (MCSR), the current higher harmonics exist in the high voltage winding. Based on finite element, the method which analyzes the controlling characteristic of high voltage winding with 500kV MCSR demonstration project in the Jiangling converter station is presented in this paper. The magnitude and frequency of harmonic current in the high voltage winding current is derived by this method. Through the comparison with the measured results of 500kV MCSR, the validity of method is proved.

Failure Risk of UHV AC Transmission Line Considering the Statistical Characteristics of Switching Overvoltage Waveshape

The sizes of ultra-high-voltage (UHV) towers and substations are related to the air clearances which are usually determined by switching overvoltage. Based on electromagnetic transient simulation of the first 1000-kV UHV ac transmission line in China, this paper extracted the effective wave information in accordance with the concept of the active part of the waveshape from calculated main types of switching overvoltage. Moreover, based on test results of switching impulse flashover voltages, a practical and accurate method to calculate the risk of failure was presented, which considered the variable characteristics of the insulation strength of the transmission line under different switching overvoltage waveshapes. Evaluation of the results focused on the comparison between two new methods and the traditional simplified method considering the effect of the front time.

Flashover Performance of Pre-contaminated and Ice-covered Composite Insulators to be Used in 1000 kV UHV AC Transmission Lines

A method is introduced for testing insulators under icing conditions. The method is based on and developed from those described in the standard of IEC60-1, IEC 60507 and IEEE Task Force on Insulator Icing Test Methods, which give instructions to test insulators under pollution. Then, the paper explores the effects of various factors, including ice thickness, pollution severity on the surface of insulators before ice accretion, atmospheric pressure, and shed profiles, on the flashover performance of short samples of two different types of silicone rubber (SIR) composite long rod insulators intended for ultra high voltage (UHV) ac transmission lines. The experiments were carried out in the multi-function artificial climate chamber in the High Voltage and Insulation Technological Laboratory of Chongqing University, China. The experimental results reveal the regularity of the effects of ice thickness, pollution severity and atmospheric pressure on the average flashover voltage of two types of composite insulators. Those can provide reference for the outdoor insulation design for UHV ac transmission lines.