Line Tower Research Articles

Structural Dynamic Response Monitoring of Power Transmission Tower

In order to study the dynamic response of power transmission lines under mechanical fault, the structural dynamic response monitoring indexes based on the requirement of field measurement were determined according to the structural characteristics of steel towers. The monitoring program was put forward in terms of the monitoring principle and basis of the sensors. The vibration characteristic, dynamic alignment and stress/strain are chosen to be the monitoring indexes. Considering the synchronization function of GPS system, the three monitoring indexes of the large span high voltage tower can be simultaneously monitored by using vibration sensor, GPS and strain sensor. The monitoring scheme can provide the theoretical base for the establishment of early warning system and the collection of dynamic response of steel tower during line break or tower collapse.

Galloping of Transmission Tower-Line System and Anti-Galloping Research

A nonlinear finite element model of transmission tower-line coupling system including transmissions, towers and insulators is established based on ANSYS in this paper. The restarting technology is proposed to solve the vertical, horizontal and torsional galloping of the transmission conductors. Under the condition of different wind velocity, galloping of tower line system is performed to get amplitude of the transmissions and internal forces of the transmission towers. Based on the typical case, the galloping control measures of using interphase spacers and multi-point weighting are performed. Various layouts projects of the galloping control measures are carried out and the effective ones are attained.

Simulation of Galloping and Wind-induced Vibration Control

A nonlinear finite element model of transmission tower-line coupling system including transmission tower-cable-insulator is established based on ANSYS. The restarting technology is proposed to solve the vertical, horizontal and torsional galloping of the transmission conductors and the wind-induced vibration of the transmission towers. A program is developed to simulate the wind velocity; the galloping of the transmission tower line coupling system is performed to get the amplitude of the transmissions and the internal forces of the transmission towers. The calculations are performed under the condition that four fixed schemes of lead viscoelastic dampers (LVDs) to control the transmission towers wind-induced vibration, and the schemes of the damper have been optimized.

Experimental Research of the Overvoltage in the Insulated Neutral Network

Experimental Research of the Overvoltage in the Insulated Neutral Network The isolated neutral network isolation resistance is often affected by the lightning discharge surge to the line cables or towers. Several overvoltage waves are maid at the moment of the lightning discharge surge. It is dangerous for the devices because at the very short time period the isolation of the device is affected by the surge impact twice or even more. The analysis of the experimentally registered lightning discharge induced overvoltage transients effect from the lightning influence to the power line till the power line disconnection were analyzed in this work. Estimation of the overvoltage characteristics to the isolation resistance was made.

Measurements and Simulations on ELF-EMF Magnetic Field Exposures from Multiple Electric Transmission Lines

There is an attempt to correlate the public health risk with strong magnetic fields from high voltage multiple transmission lines. The statement is based on the public perception that multiple sources of two and three tower lines can generate more radiated fields as compared to single tower. This paper evaluates the fact and figures on realistic situation cases about radiated field exposures based on measurements and simulation models of two and three transmission lines. The case study sites which consist of several towers of 132kV and 275kV lines were located in Melaka district, Malaysia. Measurement procedures of magnetic fields were conducted based on the IEEE/ANSI 644 standard while the dose exposure reference value was based on the public exposures of the ICNIRP limits. The results obtained from this analysis are then compared with the ICNIRP standard for assessing the significance of dose exposure between actual conditions in TNB systems with optimum simulated models of phase arrangements. Recommendations on the threshold value limits at both ROW for the new and existing transmission lines were also proposed in conjunction with development of TNB ELF-EMF policy guidelines.

Experimental Study on Lightning Surge Response of 500-kV Transmission Tower With Overhead Lines

This paper presents the measurement of the lightning surge response of a 500-kV transmission tower with overhead lines including ground wires and phase wires. A number of experimental studies on the lightning surge response of transmission towers have been carried out using freestanding structures such as scale models or actual transmission towers. However, these experiments have ignored the effects of transient electromagnetic coupling among the injection current, the overhead lines, and the tower. This paper reports a new method of measurement considering the arrangement of an actual tower and overhead lines. It is clearly shown that the measured voltage waveform across insulator strings at each crossarm depends on the direction of the injection current. Moreover, the measured current value flowing into the ground wires varies with the direction of the injection current. These results predict that the surge response of a transmission tower depends on the direction of the return stroke current. This is important for the modeling of towers with overhead lines and the estimation of the lightning performance of transmission systems under a lightning stroke.

Wind-induced transmission tower foundation loads: A field study-design code comparison

This paper presents a comparison between the wind-induced foundation loads measured on a type L6 transmission line tower during a field study in the UK and those computed using the UK Code of Practice for lattice tower and transmission line design (BS8100). In this work, the Code provisions have been generalised to give the wind-induced strain in each of the tower legs immediately above the foundation as a function of wind direction and wind speed at the top of the tower. The complete data set from the field monitoring has been decomposed to provide a similar formulation for comparison purposes. The analysis shows excellent agreement between the Code calculations and the measured results, within the overall accuracy of the field data. This indicates that, at least for the tower type examined here, the existing design Code provides a reliable transformation of the local wind speed at the top of the tower into tension and compression loads on the foundations.

Simplified models and experimental verification for coupled transmission tower–line system to seismic excitations

The simplified computational models of high-voltage transmission tower–line system under out-of-plane and in-plane vibrations are presented due to seismic excitations in this paper. The equations of motion are derived and the computer program is compiled to obtain the earthquake responses of the coupled system. To verify the rationality of the proposed approaches, the shaking-table experiments of the coupled system of transmission lines and their supporting towers are carried out and the results indicate that the errors of theoretical and testing results of systemic seismic responses are within the acceptable arrange in engineering area. Based on these studies, a simplified analysis method is proposed to make the seismic response calculation of coupled tower–conductor system faster and more effective.

The Askervein Hill Project: Mean wind variations at fixed heights above ground

This is one of a series of papers on the Askervein Hill Project. It presents results on the variations in mean wind speed at fixed heights (δz) above the ground from linear arrays of anemometer posts and towers. Most of the data are for δz = 10 m but some are for δz = 3 m. Selected and directionally grouped data from the 55 ‘Mean Flow’ runs are presented together with mean flow data from Askervein '83 ‘Turbulence’ runs. Comparisons are made between the data and guideline estimates of fractional speed-up ratio at hilltop locations and between the data and MS3DJH/3 model predictions along the tower lines. There is good agreement in most cases.

Galloping Control Permits Tower Head Compaction and Line Upgrading

Galloping Control Permits Tower Head Compaction and Line Upgrading

Galloping Control Permits Tower Head Compaction and Line Upgrading

Galloping of overhead lines due to ice and wind often results in damage and power interruptions. Control devices are being evaluated in field trials in many utilities world-wide and data based on performance have accumulated to the point where control is verified for some devices. This paper describes approaches to modifying existing transmission tower head design methods to incorporate the benefits of these controls. This allows use of longer spans and shorter towers, reducing the cost of new lines. It also provides opportunities to upgrade existing lines by retrofitting the control devices. The data from galloping observations with no controls, combined with records of actual outage rates, permit better quantification of reliability associated with line exposure and clearance between phases. Where existing practice is shown to be conservative, savings are possible in future lines through smaller clearances, even with no controls. Incorporation of controls will then offer even further savings. The field data indicate that bundle conductors are much more likely to gallop at maximum amplitude than single conductors. Consequently, there is a need to rationalize the galloping ellipse sizes so that there is a similar level of reliability on the two types of lines. An example is included where a line is built to present clearance standards but future higher security operation can be assured through add-on galloping controls.

A METHOD OF RESPONSE ANALYSIS OF TOWERS AND TRANSMISSION LINES SYSTEMS SUBJECTED TO EARTHQUAKES

This paper presents a method of response analysis of ultra-high-voltage towers subjected to earthquakes, taking into consideration the interaction between the towers and the transmission lines.Seismic responses of them are solved by the method of modal analysis using individual natural vibration characteristics of each tower and transmission line. This method has the advantages as follows: 1) The degrees of freedom remarkably decrease, as compared with those in the method applying the F. E. M. to the towers and the transmission lines. 2) This method can be applied, without difficulty, to the case where seismic waves differ at each foundation of tower and to the case where suspension towers are included. 3) The results obtained by this method are more accurate than those obtained by the method regarding the transmission lines as springs connecting the towers.

Background and Methodology for Analyzing Step and Touch Potentials Near Transmission Structures, Part I: Background A report prepared by the Working Group on Transmission Line Structure Grounding, Towers, Poles and Conductors Subcommittee

Background and Methodology for Analyzing Step and Touch Potentials Near Transmission Structures, Part I: Background A report prepared by the Working Group on Transmission Line Structure Grounding, Towers, Poles and Conductors Subcommittee

Background and Methodology for Analyzing Step and Touch Potentials Near Transmission Structures, Part II: Engineering Evaluation A report prepared by the Working Group on Transmission Line Structure Grounding, Towers, Poles and Conductors Subcommittee

Background and Methodology for Analyzing Step and Touch Potentials Near Transmission Structures, Part II: Engineering Evaluation A report prepared by the Working Group on Transmission Line Structure Grounding, Towers, Poles and Conductors Subcommittee

An Investigation of the Application of Taylor's Hypothesis to Atmospheric Boundary Layer Turbulence

Abstract The application of Taylor's hypothesis to atmospheric boundary layer turbulence at heights of 15, 30 and 58 m has been investigated by correlation analysis and phase-spectral analysis of data taken from lines of meteorological towers when the mean wind direction was essentially along the tower line. The time lag of maximum cross correlation between parallel components measured at different alongwind locations indicates that the eddy structure travels slightly faster than the mean value of the longitudinal wind at the same height. The autocorrelation functions in space and in time for the longitudinal and vertical components show good agreement, as predicted by Talyor's hypothesis, for space lags up to 252 m. The agreement for the lateral component is inferior for lags ≥32 m. According to Lin, Taylor's hypothesis holds in boundary layer shear flow for those wavenumbers κ such that κŪ≫dŪ/dz. Phase spectral analysis of parallel wind component data at different alongwind locations shows Taylor's hypo...

Evaluation of Surge Suppression Resistors in High-Voltage Circuit Breakers

The switching surge insulation level of steel tower and wood pole transmission lines operating at system voltage levels of 115 through 500 kV are compared with the switching surge magnitudes that can occur on these systems. High-side and low-side switching with and without surge suppression resistors is considered. The results indicate that at 345 kV and above surge suppression resistors should be used, while below 345 kV these resistors cannot, in general, be justified.

Electrical Design of a 345-kV Double-Circuit Transmission Line Including the Influence of Contamination

The Detroit Edison Company, in planning their 345-kV system, felt it advisable to undertake a critical examination of the electrical design of 345-kV steel tower circuits. The investigation of performance of double-circuit steel tower line design for 12, 15, 17, and 20 insulation units is reported. Special emphasis is placed on line reliability as influenced by contaminated insulators.

All-aluminum transmission tower line

IN 1960, a double-circuit 220-kv all-aluminum tower line, 2.8 miles in length, was erected as a part of the Philadelphia Electric Company's transmission program for the new Eddystone generating station.

All-Aluminum Transmission Tower Line

IN 1960, a double-circuit 220-kv all-aluminum tower line, 2.8 miles in length, was erected as a part of the Philadelphia Electric Company's transmission program for the new Eddystone generating station.

Light steel tower line designs

THE NEW LIGHT STEEL tower line designs recently adopted by the Bonneville Power Administration (BPA) brought estimated savings in excess of 12,500 tons of steel and $4,000,000 during the first two years of practical application. These designs resulted from engineering studies begun during World War II to save critical steel, and continued during postwar years in order to combat the sharp rises which have taken place in transmission-line construction costs.