High Voltage Overhead Transmission Lines Research Articles

Study on Construction Technology Standardization of Primary Guide Rope Laying by Multi-rotor Aircraft in Stringing Construction of Transmission Line

According to the practical situation of stringing construction for Ultra High Voltage (UHV) overhead transmission line, construction technology standardization of primary guide rope laying by multi-rotor aircraft is studied. This paper mainly focuses on the construction preparation, test flight and technology of laying primary guide rope. The summary of the construction technology standardization of primary guide rope laying by multi-rotor aircraft in stringing construction are useful in further guiding practical construction of transmission line.

Остаточные напряжения как возможная причина повреждения оборудования и риска для персонала при отключении воздушных линий электропередачи. Часть 1

To prevent substation equipment damage and to ensure safety of substation personnel under high voltage and extremely high voltage (EHV) overhead transmission line (TL) outage on the example of 500 kV TL outage voltages between switchable phase switch contacts are calculated. It is shown that under operating in the idle mode EHV TL outage, after arc clearing between switch contact connected to the phase at TL beginning and earth aperiodic voltage with the highest value exceeding the peak value of nominal phase voltage is created.The switch contact connected to the mains voltage, relative to the ground remains periodic nominal phase voltage. The resulting voltage between open contacts of the switch becomes aperiodic shifted periodic voltage with highest value exceeding the double peak value of nominal phase voltage that can cause breakdown of the switch. If there is a break switch phase, it will light the arc and switch under arc will go idle mode operating current, the voltage will recover to idle mode value, the current will stop, the arc goes out, aperiodic voltage will appear, etc. Such a process in a closed cycle can last a long time. Thus, output voltages high values can cause breakdown along the switches surface, damage to switches and health risk factor for the staff performing the bypass substation.

Magnetic and capacitive couplings influence on power losses in double circuit high voltage overhead transmission line

PurposeThe paper aims to discuss problems of power and energy losses in a double-circuit overhead transmission line. It was observed from energy meters’ readings, that in such a line, active power losses can be measured as “negative”. The “negative” active power losses appear when the active power injected to the circuit is lower than the active power received at the circuit end. The purpose of this paper is to explain this phenomenon.Design/methodology/approachTheoretical considerations based on mathematical model of the transmission line of π-type confirming that effect are presented. Power losses related to series impedance of the line and to shunt admittance are calculated. The theoretical considerations are confirmed by measurements done on the real transmission line.FindingsThe calculations allow to indicate components of the active power losses, i.e. related to electromagnetic coupling among wires of a given circuit, related to electromagnetic coupling between circuits and related to shunt capacitance asymmetry. The authors indicate the influence of the line/wires geometry on the active power losses in a double-circuit overhead transmission line.Originality/valueExplanation of the effect of “negative” active power losses’ measurement in a double-circuit overhead transmission line is provided in this paper.

Estimating Sag and Wind-Induced Motion of Overhead Power Lines With Current and Magnetic-Flux Density Measurements

Overhead high-voltage transmission lines (HVTLs) extend over diverse geographic regions under uneven weather conditions, where sag and wind-induced conductor motion poses serious issues for uninterrupted power distribution by HVTLs. Sag reduces the ground clearance of the line, whereas conductor motion may result in phase to phase short circuit, and damage to support structure. A real-time estimate of these factors is deemed important to develop requisite prevention measures. In this paper, we present a novel method to cater for sag and motion estimation in real-world scenarios. Our method can detect a change in sag and conductor motion, whether it is symmetrical or unsymmetrical to one or more conductors. We require uniaxial magnetic-field (MF) sensors mounted at support tower, equal to conductors, and synchronized with current-transformer (CT) data at substation. The sensors provide noncontact MF measurements, which are time stamped and transmitted to the substation. The data are then simultaneously processed along with electric current readings from the CT. For processing, we developed a unified algorithm that first distinguishes variation in sag from motion in conductor. Then, it estimates the corresponding sag or motion in any of the conductors. The method is verified first by numerical simulations, and then with a scaled setup in laboratory. Different test cases were identified by the algorithm. Error remains $\leq 1$ % for unsymmetrical sag estimation. In addition, trajectory of a conductor in motion is retrieved. Where the root mean square error between actual and retrieved conductor amplitude was only 0.0833 for the observation window of 200 ms.

Estimation of Current and Sag in Overhead Power Transmission Lines With Optimized Magnetic Field Sensor Array Placement

Power distribution mechanism in smart grid necessitates the development of an easy-to-install and contactless sensing system to monitor the operational state of overhead high-voltage transmission lines. Here, we propose a robust phase current and sag estimation method at support structures. Novelty in our work is the use of dual-axis magnetic field (MF) sensors equal to the number of phase conductors. This is realized by installing an array of sensors optimally placed in the same vertical plane as of conductors on the tower. The optimal position of sensor array was found while minimizing the condition number of governing linear system close to unity. For any circuit configuration, our method processes the sensed MF vector projections through a linear system, which is based on the Biot–Savart law. It considers the practical factors, such as sag, span length, and sensor-to-conductor distance. An algorithm is then designed to estimate the electric current and sag by iterative comparison between the measured and calculated MF. The method is first tested by numerical simulations for a typical one-circuit configuration, which involves three scenarios of symmetrical and unsymmetrical sag in conductors. The algorithm converges to a maximum error of $\le 1$ % within 300 iterations. We then experimentally verify our scheme on a scaled laboratory setup. Retrieved current and sag values were verified with the readings from ammeter and vernier caliper, respectively. The results prove the viability of our approach within $\le 2.6$ % deviation for current and $\le 1$ % for sag in all conductors.

Is the effect of high voltage transmission lines undervalued?

PurposeThe purpose of this paper is to determine whether the discount placed on high voltage overhead transmission lines is underestimated.Design/methodology/approachA quantitative analysis was undertaken, using a high voltage overhead transmission line (HVOTL) case study, to determine the effect on property values prior and post removal of the HVOTL structure. Sales data and demographics are compared to determine the change in neighbourhood characteristics.FindingsThe results show that while the HVOTL is in place, the impact on value is confined to those properties in close proximity. This is in contradiction to the findings, where on removal of the HVOTL, the property values of the whole neighbourhood improve significantly.Research limitations/implicationsThe implication of this research is that property valuers (appraisers) need to change the way they take into account the presence of HVOTLs when valuing property, with more emphasis, being placed on the neighbourhood rather than just the properties in close proximity. While the HVOTL was in place, only properties in close proximity were negatively affected, but on removal of the HVOTL the whole neighbourhood increased in value.Originality/valueResults expand on current knowledge by demonstrating the difference between the discount rate that the valuers apply to the presence of the HVOTL, as compared to the positive impact to the whole neighbourhood on removal of the HVOTL.

Оценка влияния различных факторов на значения сопротивлений и проводимостей высоковольтной воздушной линии электропередачи

Оценка влияния различных факторов на значения сопротивлений и проводимостей высоковольтной воздушной линии электропередачи

Instantaneous protection scheme for backup protection of high-voltage transmission lines

The protection scheme focused on in this study is a typical protection system used in high-voltage systems such as 132 kV, 275 kV, and 500 kV. The research will analyze the existing protection scheme for transmission lines that the power utility has implemented and will propose a new protection scheme to improve the performance of the existing scheme. The existing protection scheme currently implemented by the power utility for backup protection operation has a longer fault-clearing time and no restoration time, and it does not utilize support relays. This study will focus on a backup protection operation on high-voltage overhead transmission lines, which take up communication when the main protection has failed to communicate, the relay has failed due to loss of DC supply, or the relay function itself has been blocked. Moreover, all the support relays will be utilized in order to improve the protection system. The improvement will consider three elements, which are the fault-clearing time, fast restoration time, and relay utilization. Each improvement to the protection system will have its own philosophy and concrete rationale, which have advantages or disadvantages for the transmission line. The effect of the improvement scheme will also consider the outcomes in other schemes to ensure that time coordination does not overlap. Every possibility of a fault will be analyzed in order to have a clear understanding of the effects of the three elements. CAPE software will be used as a tool for simulation and to analyze its compatibility with real applications. CAPE software is able to model a real-life transmission line and is also able to simulate faults in the tested area. The results of the simulation show that the backup protection operation improved fault-clearing time and restoration time. It also increased the network's system stability, particularly during the occurrence of maximum fault currents.

Optimum design of steel lattice transmission line towers using simulated annealing and PLS-TOWER

This paper presents a new optimization tool for automated design of steel lattice transmission line towers in real-world engineering practice. This tool has been developed by integrating the simulated annealing (SA) optimization algorithm into the commercial PLS-TOWER software to optimize steel lattice towers for minimum weight according to ASCE 10-97 design specification using both size and layout design variables. In this context, a novel two-phase SA algorithm is specifically developed and compared with a typical SA formulation in three weight minimization problems of real-world steel lattice towers for high voltage overhead transmission lines between 110 and 400kV. The optimized designs and the CPU time required by the two SA variants are reported for each test problem and then compared with the currently available structural configurations resulting from a conventional design process in order to quantify material saving achieved through optimization.

A New Method of the Load Compensation Use during Creation of Post Blackout Start-up Path in Power System

Process of power system restoration, especially after blackout, is very complicated logistically and technically. In order to restore thermal power plant in power system, as a source of power hydro power plant is commonly used. The distance between these power plants may be relatively high – even over 500 km. High voltage overhead transmission lines to connect the power plants during the creation of post blackout start-up path are switched on under no load condition. Relatively high value of natural reactive power of these lines makes that value of voltage at the end of the switched line may reach an unacceptable high level, in spite of application of typical algorithm of automatic voltage regulator of synchronous generator. In the paper a new method of effective use of load compensation during creation of post blackout start-up path is proposed. Theoretical assumptions and simulation results of an investigation are presented. An experiment performed in the Polish Power System is also described. This experiment proved that the method proposed by the authors is advisable. The method may be utilized by power system operators for power system restoration process in emergency conditions. DOI: http://dx.doi.org/10.5755/j01.eie.22.4.15907

Modelling homeowners’ reactions to the placement of high voltage overhead transmission lines

ABSTRACTWhat are people’s reactions to news that high voltage overhead transmission lines (HVOTLs) are to be built near their homes? Will they pursue actions which might impact the project or, instead, do nothing and see what happens as due process is followed by its planners? Much could depend on whether the installation is merely in their vicinity or will excise part of their freeholding through land acquisition. This article resolves these issues by applying a staged model of infrastructure development in Queensland, Australia, via a telephone survey of 600 homeowners. Results indicate the statistical significance of certain independent variables relating to interviewees, and of intervening variables represented by their risk perceptions and prevailing attitude to electricity infrastructure. Threatened resumption of property produces distinctly different outcomes from those applying to more distant locations of power lines. Findings should prove relevant to planning authorities contemplating network expansion.

The Reusable Load Cell with Protection Applied for Online Monitoring of Overhead Transmission Lines Based on Fiber Bragg Grating.

Heavy ice coating of high–voltage overhead transmission lines may lead to conductor breakage and tower collapse causing the unexpected interrupt of power supply. The optical load cell applied in ice monitoring systems is immune to electromagnetic interference and has no need of a power supply on site. Therefore, it has become a hot research topic in China and other countries. In this paper, to solve the problem of eccentric load in measurement, we adopt the shearing structure with additional grooves to improve the strain distribution and acquire good repeatability. Then, the fiber Bragg grating (FBG) with a permanent weldable package are mounted onto the front/rear groove of the elastic element by spot welding, the direction deviation of FBGs is 90° from each other to achieve temperature compensation without an extra FBG. After that, protection parts are designed to guarantee high sensitivity for a light load condition and industrial safety under a heavy load up to 65 kN. The results of tension experiments indicate that the sensitivity and resolution of the load cell is 0.1285 pm/N and 7.782 N in the conventional measuring range (0–10 kN). Heavy load tension experiments prove that the protection structure works and the sensitivity and resolution are not changed after several high load (65 kN) cycles. In addition, the experiment shows that the resolution of the sensor is 87.79 N in the large load range, allowing the parameter to be used in heavy icing monitoring.

Conductor Surface Conditions Effects on Audible Noise Spectrum Characteristics of Positive Corona Discharge

Conductor surface conditions of high voltage overhead transmission lines have a large influence on corona characteristics. Both audible noise and corona current is highly depended on the corona discharge characteristics. However, relatively few investigations have previously been made on conductor surface conditions effects on audible noise spectrum characteristics. In the present work, the artificial pollution experiments were carried out to simulate the various surface conditions. At the same time, the audible noise spectra and the corona current of the polluted conductor are recorded. From the analysis of the experiment results, it was found that the audible noise spectra level (>1 kHz) and corona current increased obviously as the relative permittivity grew and the amount of pollution increased. Furthermore, from the results of the long-term statistical measurement about A-weighted equivalent continuous sound level (LAeq) of the polluted conductor, the close correlation between the surface potential gradient and the audible noise spectra were obtained.

Political efficacy and familiarity as predictors of attitudes towards electric transmission lines in the United States

Public opposition to the construction (i.e., siting) of new high voltage overhead transmission lines is not a new or isolated phenomenon. Past research has posited a variety of reasons, applied general theories, and has provided empirical evidence to explain public opposition. The existing literature, while clarifying many elements of the issue, does not yet fully explain the complexities underlying this public opposition phenomenon. The current study demonstrated how two overlooked factors, people’s sense of political efficacy and their familiarity (i.e., prior exposure) with transmission lines, explained attitudes of support and opposition to siting new power lines.

Effect of Magnetic Field From Mobile Phone on Brain

Human exposure to electromagnetic field (EMF) comes from many different sources and occurs in various situations in everyday life. Man-made static fields are mainly found in occupational settings, such as close to magnetic resonance imaging (MRI) scanners, although DC high-voltage overhead transmission lines are being constructed, which are expected to expose larger parts of the population to static electric and magnetic fields.Today, for power regulation most modern electrical equipment uses electronics instead of transformers. Examples include the switched power supplies to laptops, drilling tools, chargers of mobile phones and similar devices. As a consequence, the frequency content of the daily magnetic field exposure has changed mainly by adding odd harmonics (150 Hz, 250 Hz, 750 Hz, etc.). In particular, the third harmonic (150 Hz) has become another dominating frequency in our environment.In particular for brain tissues, the mobile phone used at the ear remains the main source of exposure. However, since the first generation of mobile telephony, the technology aimed at reducing the emitted power of mobile handsets. In particular, for Global System for Mobile communication (GSM) already the introduction of dynamic power control reduced the average output power to about 50% of its rated value during calls, whereas the use of discontinuous transmission during voice calls gave a further 30% reduction in average emitted power. Adaptive power control became faster and more effective in the third-generation (3G) of mobile telephony systems leading to a further reduction (by about two orders of magnitude) in the specific absorption Specific energy Absorption Rate (SAR) compared to GSM phones. In addition, hands-free kits reduce the energy absorbed by the head drastically. Digital Enhanced Cordless Telecommunications (DECT) phones are another source of everyday exposure.

Determinants of homeowners' attitudes to the installation of high-voltage overhead transmission lines

This article deals comprehensively with factors which influence attitudes to the placement of high-voltage overhead transmission lines (HVOTLs). It employs an analytical schema which links the initial stimulus of the power lines' proposal in an area to Background and Socio-economic independent variables and a set of mediating variables. From a survey of 600 residents in three different domiciliary settings in Queensland, Australia, results indicate an absence of positive attitudes and, at best, neutral ones to HVOTL placement. By multinomial logistic regression, the study probes the grounds behind negativity and extreme negativity, uncovering direct links between these attitudes and certain of the variables included in the analytical schema.

基于面电荷密度法的高压输电线路电场计算

为了研究高压输电线路周围的电场分布，本文提出了基于面电荷密度的计算方法。该方法将每个子导线的表面进行剖分，以各个节点的面电荷密度作为变量，并利用线性插值来表示弧段的电荷密度，然后根据电磁场理论建立线形方程组来求解各个节点的面电荷密度。最后，本文用500 kV紧凑型输电线路的算例来说明该方法的优点。 In order to study the electric field around high voltage overhead transmission line, surface charges method is given in this paper. The surface of every splitting conductor is divided into many arc segments; surface charges density of every node acts as the variable and linear interpolation is used to express the charges density of every arc segment. Then, linear equations have been set up according to the electromagnetic theory, and the surface charge density of every splitting conductor can be calculated. An example of 500 kV compact transmission line is presented to illustrate the advantage and the precision of the new given method.

The landscape benefits of the burial of high voltage power lines: A study in rural areas of Italy

High voltage overhead transmission lines are a type of infrastructure with a major impact on landscape quality. As studies have shown, it is sufficient that a pylon occupies even a modest fraction of a view to cause a marked decline in the aesthetic quality of the landscape. Few studies have tried to make a monetary quantification of the landscape damage caused by high voltage transmission power lines. Those few focused attention on urban areas. In this study, by means of a discrete choice experiment, the willingness to pay of the Italian population to eliminate the landscape impact of high voltage overhead transmission lines has been estimated for the entire national territory with reference to four different landscape contexts (protected mountain and hill areas, protected plain and coastal areas, other non-protected hill and mountain areas, non-protected plain areas). The results obtained have demonstrated that the willingness to pay per kilometre of power line eliminated is higher in the mountain and hill natural parks than in the other areas considered. Using a simulation with a two costs hypothesis, the research shows that the social benefit from burying high voltage power lines would exceed the costs only in limited areas of the country.

Harmonic analysis of dynamic thermal problems in high voltage overhead transmission lines and buried cables

In this contribution a dynamic thermal analysis of an overhead transmission line and a buried power cable is presented. The temperature is calculated as a function of time using a realistic power input obtained from field data measurements. For both the temperature and the power a harmonic analysis is performed. The phase shift between the Fourier components corresponding to a one day period turns out to be a good indication of the temperature delay time with respect to the power peaks. In order to validate and assess the proposed method a lab experiment has been conducted.

New Methodology of Fault Identifier for the Double Circuit Line on the same Tower

High voltage overhead transmission line is an important part of the power system to ensure the safe operation of the entire power system, which is of great significance. Power line fault not only has adverse effects to the social economy, and it may also affect the stability of the power system. Transmission line faults including permanent fault and transient fault are identified quickly and accurately, which has important practical engineering significance. This paper presents a method which can be used to identify the permanent fault and transient fault of double-circuit transmission line on the same tower, fault transient voltages and currents extracted from both ends of transmission lines are as a signal source which is decomposed into a series of harmonics in order to establish a criterion function, and then the transient and permanent fault can be identified based on the changes of criterion function value.