Extra High Voltage Power Transmission Research Articles

Design and Analysis of 400KV Extra High Voltage Power Transmission Lines in Lebanon

This paper aims to design and analyze an overhead AC extra high voltage transmission line in Lebanon, using ACSR conductors, to meet the growing demand for the future. The optimal design will consider various factors to achieve the best system efficiency and performance, while complying with regulations and safety standards, including EHV voltage level, conductor size, number of conductors per phase, cable sag, and other factors, as well as estimating and describing environmental impacts such as conductor surface potential gradient, corona loss, radio interference, and audible and random noise.

Method for Determining the Resonant Frequencies of Extra High Voltage Power Transmission Line

Method for Determining the Resonant Frequencies of Extra High Voltage Power Transmission Line

Control of a Hybrid Shunt FACTS Compensator for Voltage Collapse Prevention in Interconnected EHV Power Transmission Systems

This article presents the converter topology for a hybrid shunt compensator (HSC) and its control suitable for an extra-high-voltage (EHV) power transmission system that helps to prevent voltage instability/collapse in multimachine interconnected power systems. Similar compensators combining a static VAR compensator (SVC) and a static synchronous compensator (STATCOM) have been proposed in the literature for power factor correction and active filtering, which are issues mostly related to the distribution system. However, for application in EHV transmission and voltage stability, the existing hybrid structures may not be suitable. This article particularly focuses on the prevention of voltage collapse that takes place in large EHV power transmission systems due to the mismatch of system-wide reactive power generation and consumption. The HSC proposed here is formed by the series combination of a STATCOM having a voltage rating of just 0.15 p.u. and an SVC having a voltage rating of 0.85 p.u. A suitable control strategy is formulated for the HSC that results in a modified operating ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V\text{--}I$</tex-math></inline-formula> ) characteristic enabling the compensator to behave like a STATCOM (with a STATCOM of considerably low voltage rating) and inject constant current even when the voltage at the point of common coupling falls as low as 0.7 p.u.

Fifth Harmonic Spectral Voltage Components in EHV Power Transmission Systems

Fifth harmonic voltages and currents have been measured in some extra high voltage (EHV) power transmission systems. This paper contains a discussion and explanation of this phenomenon. The emphasis is on the impact of overexcitation of power transformers in EHV systems. Examples of measurements taken in 500 kV substations are illustrated and representative data collected are shown.

ОЦІНЮВАННЯ ВПЛИВУ НЕСИМЕТРІЇ ЛІНІЇ ЕЛЕКТРОПЕРЕДАВАННЯ НАДВИСОКОЇ НАПРУГИ НА ВИЗНАЧЕННЯ ПАРАМЕТРІВ КОМПЕНСАЦІЙНОГО РЕАКТОРА

The article shows the urgency of the problem of studying resonant processes in extra high voltage power lines. The research of processes in extra high voltage power transmission lines is carried out to develop and implement measures to prevent overvoltages. Resonant overvoltages arising because of open phase modes of operation of the extra high voltage transmission line are considered. The paper shows the influence of the levels of longitudinal asymmetry on the calculation of the resistances of compensating reactors to reduce the values of overvoltages in the pause of single-phase automatic reclose. The degree of influence of the wire transposition scheme on the choice of the resistance of the compensation reactor and on the values of resonant overvoltages in the cycle of single-phase automatic reclose is considered. Estimation of asymmetry coefficients for different transposition schemes is performed. To select the resistance of the compensation reactor, the data of the existing high-voltage transmission lines of 750 kV were taken. Recommendations for the implementation of measures to prevent and limit resonant overvoltages are given. The current theoretical and practical problems of operation of the extra high voltage power line are considered and the ways of further research are shown. References 14, figures 5, tables 2.

Resonance Analysis of a Transmission Power System and Possible Consequences of its Undergrounding

Presently there is a great interest in underground cable transmission lines in extra high and high voltage level networks. The undergrounding of the transmission system can lead to the decrease of the resonance frequencies resulting in high overvoltages and possible power system component damages. It is therefore necessary to analyze possible resonance problems in the mixed power transmission system. In this work a frequency dependent model for transmission systems is implemented and the frequency scan results are presented. In order to gain a better understanding of the nature and extent of the resonance, a resonance mode analysis is also executed. The proposed procedure is tested on two examples: a ten-node power system and the Swiss extra high voltage (EHV) power transmission system. Power systems comprising solely overhead lines and different variations of mixed power system are examined.

Decreasing the influence of arc feed currents and transient recovery voltages in single-phase conditions in EHV lines

One of the most efficient ways to solve the problem of reactive power compensation connected with restriction of unacceptable levels of voltage on extrahigh voltage (EHV) power-transmission lines is installation of additional shunting reactors (SR) in the EHV networks. Moreover, installation of shunting reactors leads to the occurrence of resonance overvoltages under single-phase operation conditions of power transmission (for example within the one-phase automatic reclosing time), as well as to the occurrence of deenergized current phase of the arc feed in the arc channel, which prevents fast deionization of another channel and increasing transient recovery voltage. In this paper, measures for decreasing the influence of arc feed currents and transient recovery voltages in single-phase conditions of EHV lines are considered.

Fuzzy Recognition Method and Simulation Analysis on Second Harmonic Excitation Inrush Current of Transformer

With the rapid development of electric power industry in our country, the extra-high voltage power transmission system is widely applied so that the power transformer plays a more and more important role. This not only requires the transformer to quickly protect the circuit system but requires the transformer to be sensitive and reliable. Generally speaking, the method of differential protection is used to deal with some troubles when it breaks down such as the faster actuation time and wrong operation in magnetizing inrush current according to the second harmonic principle and waveform symmetry principle. On the basis of using second harmonic principle, we try to introduce the fuzzy recognition technology and provide a new criterion for the interlock of second harmonic by constructing the function subordination. Finally the simulation analysis is made through MATLAB, whose effect is better.

A new method for non-unit protection of power transmission lines based on fault resistance and fault angle reduction

In the paper, a new non-unit transient protection method suitable for single-phase faults of EHV power transmission lines was proposed based on the analysis of the propagation characteristics induced by fault transient current, the transition resistance and the fault angle on corresponding energy values of high-frequency transient current in extra high voltage (EHV) network. In the procedure, the transient current energy values from both sides of the bus were primarily normalized on the basis of transition resistance and fault angle, and then the characteristic value with functions of direction judge and value comparison was obtained by calculating their difference. By utilizing the characteristic value, the methodology came into being, by which the impacts of both transition resistance and fault angle were eliminated. The overall design has a high reliability level and owns twice the scope of the conventional protection. Simulations were performed and analyzed upon a three-phase 500kV power system by utilizing ATP/EMTP, with various kinds of typical faults being taken into account. Plenty of results verify the feasibility of the algorithm for ultra-high speed protection of EHV power transmission lines.

Estimation of Battery State of Charge With $H_{\infty}$ Observer: Applied to a Robot for Inspecting Power Transmission Lines

Battery state-of-charge (SOC) estimation is essential for a mobile robot, such as inspection of power transmission lines. It is often estimated using a Kalman filter (KF) under the assumption that the statistical properties of the system and measurement errors are known. Otherwise, the SOC estimation error may be large or even divergent. In this paper, without the requirement of the known statistical properties, a SOC estimation method is proposed using an H∞ observer, which can still guarantee the SOC estimation accuracy in the worst statistical error case. Under the conditions of different currents and temperatures, the effectiveness of the proposed method is verified in the laboratory and field environments. With the comparison of the proposed method and the KF-based one, the experimental results show that the proposed method can still provide accurate SOC estimation when there exist inexact or unknown statistical properties of the errors. The proposed method has been applied successfully to the robot for inspecting the running 500-kV extra high voltage power transmission lines.

A Novel Transient Directional Unit Based on Adaptive Median Filtering

A new transient directional unit for extra high voltage(EHV) power transmission lines is proposed, which identifies fault direction by means of comparing the time-domain transient energy of the forward traveling-wave with that of the backward one in the very short period of time after fault occurs. The unit algorithm is designed with the technology of adaptive median filtering, which is first employed to process the forward and backward traveling-waves, and then calculates the time-domain transient energy ratio of the forward traveling-wave to the back one, by which the fault direction is discriminated. Numerous ATP-EMTP simulation tests show that this proposed directional unit not only operates reliably, sensitively and ultra-high-speed, but also endure the influences of various factors, including different fault types, fault locations, transition resistances or fault inception angles. It will be worthy of application greatly.

Cardiac electrophysiology: Theoretical considerations of a potential target for weak electromagnetic field effects

With the widespread introduction of extra high voltage power transmission lines in the 1960s, and subsequent to early reports from Soviet Union scientists about health risks for transformer station personnel, public concern regarding the effects of electromagnetic fields (EMFs) on biological function has given rise to a large number of investigations and legislation to limit domestic and occupational exposure to EMFs. The underlying rationale for concern is related to the fact that living cells are electrically active, which makes them potentially vulnerable to electromagnetic interference. In the heart, electrical activity is crucial in coordinating the contraction of millions of cardiac cells, and disturbances in cardiac electrical activity, also known as arrhythmias, are often life threatening. Electrical fields induced in the heart by weak external EMFs (such as those encountered in a domestic setting) are understood to be at least 2 orders of magnitude smaller (< 1%) than those that occur naturally as an intrinsic consequence of cardiac activity. Using quantitative models of cardiac cellular electrophysiology, the effect of weak (1%) manipulation of key current mechanisms that give rise to the electrical activity of the heart is therefore assessed.

00/01361 Analysis of overvoltages in overhead ground wires of extra high voltage (EHV) power transmission line under single-phase-to-ground faults

00/01361 Analysis of overvoltages in overhead ground wires of extra high voltage (EHV) power transmission line under single-phase-to-ground faults

Analysis of overvoltages in overhead ground wires of extra high voltage (EHV) power transmission line under single-phase-to-ground faults

Abstract Overhead ground wires (GW) of extra high voltage (EHV) power transmission lines, apart from lightning-induced overvoltage protection are frequently used for carrier-current communication. In this case the ground wires are suspended on insulators, the dielectric strength of which should be sufficient for the line operational conditions. The insulation level is defined from the condition of the single-line-to-ground (SLG) fault, thus insulator protecting spark gaps should not be flashed-over during such conditions — in order to maintain continuity of the communication channel along the line. Overvoltages during such faults depend on many parameters such as fault place, fault angle, pre-fault load etc. Therefore, designers should investigate the problem for determination of the worst-case scenario. In this paper, dependence of the overvoltages on 750 kV power transmission line ground wires upon the SLG fault place and pre-fault load of the line in transient and steady states is investigated. The analysis was performed by using dynamic arc model incorporated into the EMTP program. The provided simulations show that adequately introduced primary and secondary arc models are decisive factors for an accurate simulation of the electromagnetic phenomena in the EHV transmission lines during an arc crossing-over (here the primary arc plays an important role) and during so called dead-time, when the secondary arc takes place. This paper gives some recommendations for the insulator strings coordination in the 750 kV earth wires on the basis of computer simulation results.

Electrostatic performance of EHV overhead lines with asymmetrical bundles

This study deals with the computation of the electric potential and field in the vicinity of overhead extra high voltage (EHV) power transmission lines with asymmetrical bundles. The values of the electric field at the surface of the bundles as well as at the ground wires and the ground surface will also be obtained. The computer model is based on finding the potential coefficients and then solving a set of complex equations, whose number depends on the number of subconductors per phase, number of 3-phase circuits involved and the number of existing ground wires. The method is applied to a 6-bundle, 750 KV, single circuit line with flat configuration and two ground wires, resulting in a total of 20 complex equations to be solved, in order to get the charge on each of the subconductors and ground wires. The electrostatic potential and the electric field at any point can then be readily found. A comparison of the subconductor field of both symmetrical and asymmetrical bundles is made. It will be shown that the use of asymmetrical bundles will result in a reduction of the surface gradients at the bottom subconductors. At the same time, however, the field at the surface of the other subconductors will increase. This indicates that the suggested application of these asymmetrical lines for reducing the audible noise due to the line corona activity should be investigated more critically. No general statement is possible on this issue, since the numerical values of the subconductor fields will largely depend on the particular geometrical data of the line under consideration.

Developments of the laser current transformer for extra-high voltage power transmission lines

Developments of the laser current transformer for extra-high voltage power transmission lines

8C1 - The laser current transformer for EHV power transmission lines

A current measuring device applicable to an extra-high voltage power transmission line higher than 500 kV is proposed with preliminary experimental results. It obtains the instantaneous magnetic field ajacent to a transmission wire by measuring the angle of Faraday rotation of a laser beam in a flint glass rod. The laser beam is transmitted and analyzed at a ground potential site, and in the energized part this device has neither insulated conductors nor active elements. An experimental laser current transformer yielded a sensitivity of 66 mV per 100 A and good linearity. Various sources of error and modifications are discussed.

Progress in Extra-High-Voltage Power Transmission

In Part I of this paper a review is presented of the present status of extrahigh-voltage (EHV) power transmission (275 kv and higher) in this country and abroad. A forecast is made of the future requirements and developments of EHV transmission in the United States for the next 20 years, to 1977. It is concluded that: 1. there will be continued and rapid expansion of EHV systems at the highest voltage presently used, 345 kv; 2. that a higher voltage of the order of 460 kv will be introduced probably about 1962 in this country, and 3. a still higher voltage of the order of 650 kv may possibly be introduced about 1975. In Part II the problems are reviewed which must be solved by the utilities and manufacturers in this country in order to transmit power at these higher voltages reliably and economically. Areas of technical work are identified and the problems of EHIV technology are classified accordingly. The means which are available for the solution of these problems are then reviewed: analytical work, laboratory investigations, experimental lines, prototype EHV systems, and, of course, tests on the actual systems. It is concluded that all these means are necessary to obtain a proved solution. There is no doubt that the American electrical industry will continue to meet successfully the challenges presented by the ever-increasing requirements for electric power at a reasonable cost.