Conductor Sag Research Articles

Electrical design parameters of all-dielectric-self-supporting fiber optic cable

A lumped circuit model for calculating voltages and currents on all-dielectric self-supporting (ADSS) fiber optic cable near high voltage transmission lines has been developed. The model has been used to show that contamination levels, tower attachment points, relative ADSS and conductor sag and electrical phasing of the conductors are important parameters and must be considered in calculations, especially when determining the possibility of dry band arcs which could lead to cable damage.

Effects of conductor sag on spatial distribution of power line magnetic field

Traditional extremely low frequency (ELF) magnetic field computation techniques assume that the current carrying power line conductors are straight horizontal wires. This assumption results in a model whose magnetic fields are distorted from those produced in reality. An exact solution and an approximation are proposed for modeling magnetic fields produced by the sagged conductors of power lines, by taking advantage of the fact that the equation of the catenary exactly describes the line sag. The proposed approaches differ in the required computational burden and in the precision of the results. A field mapping measurement example illustrates the applicability and the need for this analysis. The relative importance of the catenary effect is discussed.

Vibrational spectra and phase transitions of silver-transition metal chalcogenides of argyrodite family

Infrared transmission spectra of the ionic conductors Ag 7TaS 6, Ag 7NbS 6 and Ag 7 − x TaSe 6 − x I x (0 ≦ x ≦ 1), which belong to the “argyrodite family” phase, have been studied in the temperature range between 300 and 80 K. As for Ag 7TaS 6, Ag 7NbS 6 and Ag 7 − x TaSe 6 − x I x ( x = 0.2, 0.3 and 0.4), the observed M-X ( M = Ta, Nb; X = S, ( Se, I)) stretching peaks have shown the shifts or the splittings, which suggest the phase transitions, with decreasing temperatures. The results obtained have been interpreted as compared with those of Raman spectroscopic studies and powder X-ray diffraction studies.

Crystal Structure and Conductivity of the New Superionic Conductors Ag 4Zr 3S 8 and Ag 3.8Sn 3S 8

The new superionic conductors Ag 4Zr 3S 8 and Ag 3.8Sn 3S 8 crystallize both in cubic space groups with lattice parameters a = 10.9427(3) Å ( P4 332, Z = 4, and ρ = 4.87 g cm -3) and a = 10.8013(4) Å ( P4 132, Z = 4, and ρ = 5.39 g cm -3), respectively. These compounds have similar sulfur packing consisting of sulfur octahedra sharing common edges. In both cases the M cations, either Zr or Sn, are located inside the sulfur octahedra (12 d sites). The main crystallographic difference between the two structures is the silver packing. In Ag 4Zr 3S 8 the silver ions are located in three different tetrahedral sites, two of them being partially occupied. For Ag 3.8Sn 3S 8 the silver ions are exclusively situated in statistically occupied octahedral sites (12 d and 4 b sites) giving a rock-salt-type lattice. From the properties point of view, they are both mixed conductors exhibiting a relatively high ionic conductivity. The ionic σ Ag+ and total conductivities were measured from room temperature to 205°C.

Theoretical model for temperature gradients within bare overhead conductors

A thermal model is described which can be used to calculate the temperature distribution within an energized, stranded overhead conductor. It has been shown that for typical conductor constructions energized to current levels which produce conductor temperatures less than 100 degrees C and for reasonable weather conditions, the maximum temperature difference that exists in stranded conductors is less than 10 degrees C. If conditions reach such a state that birdcaging in the conductor occurs, then temperature differences within the conductor greater than 10 degrees C can result. However, birdcaging will only occur in conductors for which the supporting strands have a coefficient of thermal expansion is greater than that of the conducting strands (ACSR, for example) and only at elevated temperatures, usually well above 100 degrees C. Finally, the results show that ampacity models based on the assumption of an isothermal conductor will provide accurate predictions of a conductor temperature that are between the center and surface temperatures. A few general conclusions are drawn about the influence of temperature gradients on conductor sags. >

Prediction of overhead transmission line ampacity by stochastic and deterministic models

A probabilistic method for the prediction of overhead transmission line ampacity as a function of time of day, based on previous line loading and weather history, is described. Real-time calculation of transmission line ampacity has until now only been possible when the prevailing weather conditions were known. However, at the dispatching station, the availability of overhead line ampacity as a function of the time of day is often desired several hours in advance. The stochastic/deterministic algorithm that has been developed for this purpose is used to predict ampacity for a 230 kV line. It was also used to predict the loss of conductor tensile strength, increase of conductor sag due to creep, and infringement of conductor to ground clearance as a function of temperature and time. >

New silver superionic conductors Ag 7XY 5Z (X = Si, Ge, Sn; Y = S, Se; Z = Cl, Br, I)-synthesis and electrical studies

New phases of the argyrodite family with formula Ag 7XY 5Z have been synthesized. They have a cubic (F 4 3m) structure. Electrical studies reveal a purely ionic conductivity. Conductivity versus temperature curves show two domains in which the Arrhenius law holds: the high temperature domain ( T>−30°C) is characterized by a low activation energy ( E σ≅0.12 eV) whereas the low temperature domain ( T<−60°C) presents a higher activation energy ( E σ≅0.25 eV). The transition from one domain to the other takes place progressively, indicating that the modification process does not affect the crystal lattice. This change can be explained by ordering of the Ag + ions in two preferential low-temperature sites.

Raman and far IR studies on Ag 2CdI 4 and Cu 2CdI 4 superionic compounds

Raman spectral studies, far infrared reflection and transmission spectra for the superionic conductors Ag 2CdI 4, Cu 2CdI 4 at 300 K are reported. From these studies the TO and LO modes are assigned and optical conductivity in the region 30 cm -1-150 cm -1 are calculated. The behaviour of conductivity in this frequency region is explained on the basis of jump diffusion model.

Experimental Verification of a Real-Time Program for the Determination of Temperature and SAG of Overhead Lines

An outdoor test facility was used to experimentally verify real-time overhead conductor ampacity and sag programs. The facility consists of a 213m span of 26/7 336 kcmil ACSR conductor completely instrumented ented with 13 thermocouples as well as a sag and tension device. A weather station mounted near mid-span monitors all pertinent weather conditions. The measured conductor tempetatures fluctuated significantly antly along the length of the test span. Spanwise variations in the measured instantaneous temperatures were frequently in excess of 100C for a wide variety of conductor currents and weather conditions. The conductor temperatures predicted by the real-time ampacity program ram were within°C100C of the average measured conductor temperatures for all tests. Measured conductor sags were within 5 percent of values predicted by a real-time sag program. The results of the experimental project show that accurate predictions of real-time conductor temperatures and sags can be achieved by knowing the conductor current, wind speed, wind direction and the ambient air temperature. Therefore, computer programs are capable of predicting conductor temperatures and sags with a minimum amount of weather data provided by a simple and inexpensive weather station. Instrumentation ation placed on the conductor is not necessary for execution of the ampacity and sag programs.

Some Studies on Carrier Propagation in Overhead Transmission Lines

The effectiveness of a carrier channel on a power line under various power frequency load conditions is studied. The effect of increase of load current results in an increase of conductor temperature, line length and sag. Therefore, the resistivity of the ACSR conductor material increases and the effective height of the conductor above the earth level decreases. A mathematical model of series-impedance and shunt-admittance which takes into account the above effects is used to evaluate the carrier signal attenuation on a line. Further, for the case of a bundle conductor line, the effect of subconductor deflections on the carrier attenuation has been studied. The effects of earth resistivity and earth wires on the actual carrier attenuation have also been studied.

Sag and tension calculations for mountainous terrain

While normal sag and tension calculations based on the ‘equivalent-span’ concept are satisfactory, when applied to transmission lines located in a reasonably undulating terrain, the answers obtained by this method are inaccurate for mountainous terrain. An alternative method of calculation, which is based on the analysis of the change of state equation for each span of a section in turn, is given. It is shown that when using this new approach the full effect of both the suspension and tension insulators can be included together with the influence of the running-out blocks on the sag of the conductor.The paper also shows how this concept can be adapted to the function of line design and gives several examples of critical areas where existing methods may give unacceptable results.When stringing conductors in mountainous terrain, it is not always practical to measure the conductor sag using conventional techniques and the paper gives three additional means which may be used, and discusses the advantages and disadvantages of each.

Silver ionic and electronic conductivity in Ag 9GaS 6, Ag 9AlS 6, AgGaS 2, AgAlS 2, and AgAl 5S 8

Silver ionic and electronic conductivity in phases in the Ag 2SM 2S 3, M = Al, Ga, systems have been investigated using dc methods with ionically reversible electrodes and ac methods. Measurements on the mixed conductors Ag 9GaS 6 and the new phase Ag 9AlS 6, both with high silver ionic conductivity, the chalcopyrites AgGaS 2 and AgAlS 2, both with predominate silver ionic conductivity, and the mixed conducting spinel, AgAl 5S 8, are reported. In addition, a schematic version of the Ag 2SAl 2S 3 phase diagram is presented.

A New Thermal Rating Approach: The Real Time Thermal Rating System for Strategic Overhead Conductor Transmission Lines Part III Steady State Thermal Rating Program Continued-Solar Radiation Considerations

For the first time, equations and computer programs are developed to show how the solar radiation received by an overhead transmission line is dependent on the conductor sag or slope. In the past, the overhead line has been assumed to lie in a horizontal plane with respect to the earth for the entire span length. Mathematical relationships for determining the sun's position in terms of solar azimuth and solar altitude, as a function of latitude, declination and hour angle are formulated and a polar plot is constructed to show the apparent path of the sun during the day for each month. Two different methods are presented to determine the angle of incidence between the sun's ray and the normal to any sloped cylindrical surface oriented at any azimuth angle. Plots are provided to indicate the variation in the angle of incidence and the direct component of solar radiation absorbed as a function of solar time for four general transmission line azimuths and five slopes at one latitude and declination. In addition, plots are drawn for the total solar radiation received by a conductor on a typical clear day as a function of both the span length and any sag or slope for both minimum and maximum diffuse radiation conditions for four general transmission line azimuths at one latitude and declination. It is shown that the conductor slope can have as much of an effect on the total radiation as does the solar adsorption constant.

Monte Carlo Determination of the Frequrncy of Lightning Strokes and Shielding Failures on Transmission Lines

The probabilistic approach of the Monte Carlo method has been applied to the electro-geometric model used for the analysis of frequency of lightning strokes and shielding failures on overhead lines. This approach has enabled theoretical studies to be made of how these parameters are influenced by conductor sag, variations in terrain, and the presence of trees surrounding the line route.

Electronic Computer Program Permits Optimized Spotting of Electric Transmission Towers

A recently developed computer program will position both angle-and tangent-type towers on any given terrain. The towers are so positioned that the optimum cost per foot of line may be obtained, consistent with predetermined tower heights and types. Basically, the program's tower spotting procedure consists of a mathematical simulation of the established manual method of moving a transparent parabolic-shaped template, representing the conductor sag, along a profile representative of existing terrain features. This program is written in Fortran for use on an International Business Machines Corporation 704-32K digital computer.

Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors

Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors

Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors

The main objects of the investigation described in this paper may be summarized thus:- (i) To determine the effects of temperature and tension upon the sharing of the tensile load between the steel and aluminium components of a steel-cored aluminium (s.c.a.) conductor. (ii) To ascertain whether variations in the load distribution seriously affect the normal sag and safety of the conductor. (iii) To propose measures for ensuring that the normal sag remains unaffected after the stringing of the conductor. Tensions in the steel and aluminium at various points along typical s.c.a. conductors were measured by a magnetic method; a single length of steel-cored copper (s.c.c.) conductor was also included in the tests. The effects of load-distribution changes were also estimated by noting the corresponding variation in the elastic modulus Ec of the conductor. Adhesion between the steel and aluminium was also examined. The results indicated that the final load distribution is determined by the rate of creep in the aluminium wires, and is independent of the stringing temperature. Although more data concerning creep are required, the tests suggested that it will be some years before creep has any marked effect. It was found that the inelastic stretch of a conductor can cause large increases in sag which far outweigh those that might result from creep. Most of the inelastic stretch was removed when the conductor was tensioned up to the maximum design load, and pre-stressing of the conductors before final stringing is therefore strongly recommended. The steel core appears to carry slightly more than its share of the total load, but since its safety and that of the conductor are not threatened thereby, no change in the B.S. Specification governing the strength of s.c.a. conductors is advocated.

The author's reply to the discussion on “Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors”

The author's reply to the discussion on “Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors”

Discussion on “Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors” before the Transmission Section, 11th April, 1945

Discussion on “Distribution of tensile load in relation to temperature and sag of steel-cored aluminium conductors” before the Transmission Section, 11th April, 1945

The influence of towers and conductor sag on transmission-line shielding

The influence of towers and conductor sag on transmission-line shielding