Steel Poles Research Articles

Structural failure analysis of 345 kV transmission line

An ice storm in Central Iowa on March 7, 1990, caused the domino failure of 69 H frame steel pole structures that were part of a 345 kV transmission line covering a distance of approximately 30.6 km (19 miles). This paper briefly documents the damage, and presents the nonlinear structural analyses performed on a portion of the above transmission line using the ETADS software, which is a structural finite element submodule of TL Workstation software. The analysis included a characterization of the likely storm loads and their application to the transmission systems. The methodology used in trying to simulate the sequence of events leading to the failure is also presented. >

Undulator scheme providing wide range magnetic field tuning

Various undulator schemes were investigated with the goal to find a scheme providing operative wide range K-strength variation without magnet gap changing. Computer simulations and experimental mock-ups were used. The best results were obtained with a novel scheme based on EM coils producing a strong longitudinal magnetic field and a periodical structure of steel poles supplied by additional permanent magnet arrays [A.A. Varfolomeev et al., Nucl. Instr. and Meth. A 318 (1992) 809]. This scheme is more compact, ensures less problems with cooling and gives the highest magnetic field strength for small λ w values.

Rock socketed drilled shaft and directly embedded pole tests

A major purpose of overhead transmission line design is to achieve a minimum cost for a given level of reliability and safety. The greatest uncertainty in this process is in foundation design. The Electric Power Research Institute (EPRI) has sponsored, since 1977, a comprehensive program of activities in foundation design. A recent activity involves performing well documented load tests of foundations partially or totally socketed in rock. As part of this activity four full-scale foundations were tested. All four foundations, two reinforced concrete drilled shafts and two directly embedded steel poles, were subject to high moment loads and modest shear and compression forces-loads which are characteristic of single pole transmission line structures. The load tests performed, data collected during the field exploration and laboratory testing, and predictions using the available analytical models are presented. Comparison of test results and model predictions indicates a need to refine presently available design methods. >

Standard curves for economic application of wood poles and light duty steel poles using a personal computer

A simplified algorithm is presented which models the simultaneous wind and weight span capability for wood and light duty steel poles. The model is based on the mathematical derivation of the significant parameters which influence pole capacity and insulator swing angle considerations and was developed using a personal computer. The advantage is a user friendly, minimum input algorithm, which eliminates the need to run the more complicated design and analysis program normally used for this type of application. A CAD system is used to plot a family of curves from the numeric results in the form of application charts. Charts are obtained which show wind span versus weight span for all pole sizes (classes) and pole heights, including line angle applications. Typical applications are presented. >

Acute effects of ELF electromagnetic fields: a field study of linesmen working with 400 kV power lines.

The aim of the study was to investigate the possible acute effects of exposure to electric and magnetic fields. Twenty six experienced linesmen, aged 25 to 52, were studied during two working days while performing a simulated routine inspection of insulators on steel poles of a 400 kV power line. During one of the working days the inspection was performed on a power line in operation and on the other day the same procedure was performed on an identical power line, which was not in operation. The two days were found to be comparable with regard to the physical workload which, on the basis of heart rate measurements, was estimated to be high. Exposure to the electric and magnetic fields was measured using a device designed for on-worker sampling on each linesman. The mean exposure for the working day was estimated to be 2.8 kV/m (SD = 0.35) and 23.3 microT (SD = 4.2). The possible effects of exposure were studied using a battery of four automated performance tests, EEG, a mood scale, and a questionnaire to assess subjective symptoms. All workers were examined immediately before and after each workday. Furthermore, blood samples were collected for each subject on three different occasions during each workday. The battery of behavioural tests comprised a test of simple reaction time, a vigilance test, a test of short term memory (digit span), and a perceptual test (symbol digit). The four EEG recordings for each worker were judged blindly and sorted with regard to amount and stability of alpha activity. The blood samples were used for an analysis of possible changes during the workday with regard to the following hormones: thyroid stimulated hormone, luteinising hormone, follicle stimulating hormone, prolactin, cortisol, testosterone, and neopterin. Detailed analyses of the results using both parametric and nonparametric tests showed no statistically significant difference between the two conditions which could be attributed to exposure to electric and magnetic fields.

Analysis and design of single-pole transmission structures

The unguyed single-pole transmission structure is widely used to support transmission lines of up to 345 kV capacity. Most such structures are wood poles, although prestressed concrete poles and tubular steel poles are sometimes used in high decay or high load situations. A number of features combine to make this type of structure an interesting structural analysis and design problem. Whether naturally grown or manufactured, the pole structure is almost always nonprismatic. Wind, ice and snow loads acting alone or in combination are variable and occasionally severe in nature. Poles are slender and the combination of transverse wind load with vertical dead and ice loads often leads to behavior which is geometrically highly nonlinear. The continuous exposure to weather, fungi, accidents, etc. results in structures with capacities that often deteriorate very significantly with time in service. The material properties (strength, stiffness), especially of wood, are highly variable, as are the soil conditions. The configurations of conductors, davit and cross arms, and attachments that are in use vary widely. This large variety of structural shapes plus the necessity of changing the configurations of in situ structures to meet new conductor and clearance requirements prevents the use of only a few designs. Thus rapid ways to assess existing structures and to design new structures are required. Since there are more than 130,000,000 poles currently in use in single-pole and H-frame transmission structures and several million new poles are put into service each year, the design effort related to poles is large. As part of an eight-year effort to develop reliability-based design methods for transmission structures, a correct procedure for analyzing and designing single-pole transmission structures was established. Implemented in program POLEDA (POLE Design and Analysis), this procedure enables unguyed planar single-pole structures of virtually any material and configuration to be rapidly analyzed or designed. The analysis is based on the Newmark numerical technique which, it is shown, in the limit provides an exact solution to the differential equation for large deflections of transversely loaded beams. The four design options provided in POLEDA use the load and resistance factor design (LRFD) format. This permits the user to use current, deterministic, design procedures or to use load and resistance factors based on reliability studies. The program provides the necessary high-quality analysis capability which forms an integral part of reliability-based design. It is being widely adopted by the electric utility industry.

Seasonal and diel variation in the standing crop of fishes and macroinvertebrates from a Gulf of Mexico surf zone

To determine the relative importance of surf zones as habitats for fishes and macroinvertebrates, compared to other inshore marine environments, seasonal and diel abundance patterns were studied for one year. Both study sites were located on the south shore of Horn Island, a barrier in the northern Gulf of Mexico. At each site a 300 m 2 area was sampled, using a 50-m seine set around steel poles. Capture efficiency of the seine, determined from escapement tests, averaged 82%. While 59 species were captured during the study, only six species, Harengula jaguana, Anchoa hepsetus, A. mitchilli, Callinectes sapidus, A. lyolepis and Menticirrhus littoralis, comprised 90% of the total catch by number. Summer macrofaunal standing crop (mean = 9·8 gm −2, wet weight) was significantly greater than other seasons. The lowest values for both density and standing crop were those obtained in the winter. Both standing crop and average weight of the fishes increased significantly in night samples; a similar pattern did not occur for blue carbs. This primarily reflects the movement of larger, but generally rarer, fish species into the shallow surf zone after dark. Principal components analysis indicated that the standing crop of fishes was lowest during periods of reduced water volume and wave activity. However, seasonal factors appear, overall, to be more important in influencing fish abundance. Compared to a wide range of inshore marine habitats, surf zones appear intermediate in standing crop. Thus, at least during the summer, such habitats are important contributors to inshore standing crops of fishes.

Development and Installation of BPA's New Generation Transmission Conductors

The Bonneville Power Administration (BPA) has developed a family of new generation conductors which promises to reduce transmission line life-cycle costs. These trapezoidal wire conductors reduce air void area by 80 percent over conventional round rod conductors, allowing a denser packing of conducting material and greater efficiency through increased conductance and/or reduced tower loads. The trapezoidal wire family is made up of nine conductors ranging in size from 1.0 to 1.8 inches; six are all aluminum and three are aluminum with steel reinforcement. The new conductors are expected to satisfy all of BPA's typical conductor requirements for new construction, rebuild, and reconductoring projects, where the economics of resistive losses dominate the design. This paper introduces the new conductor family and assesses its uses and limitations. It discusses design details; mechanical, stress-strain, creep, and self-damping characteristics; and conductor sizing, procurement, handling and sagging, savings, and lattice steel and wood pole applications. It also describes the first use of the trapezoidal wire conductor family on the BPA Boundry Integration/Reinforcement Project.

Longitudinal Dynamic Loading of a Steel Pole Transmission Line

Model test results have demonstrated that it is possible to simulate a number of dynamic loading conditions on a scale model of an actual transmission line system, taking into account a large number of variables, and producing results having direct interpretation at full scale. The method appears to be particularly useful in identifying any potential "trouble areas" in an existing design such as the use of horizontal struts on light angle structures, and/or adequacy of fatigue strength under galloping conditions. A sample of the principal findings of this investigation are: 1) A method for rapidly calculating the flexibility (stiffness) of steel pole transmission structures has been developed. The method relies on computer print-out data supplied by pole manufactures at the time of bid evaluation. 2) Results of broken static wire tests show that structure flexibility reduces both the dynamic load and the residual load below the load calculated for a rigid structure. 3) The maximum loads occur for broken static wire on the most flexible structure, and for ice unload of static wire on the most stiff structure. The latter result is subject to the further restraint of a horizontal strut at a light angle. 4) Unexpectedly high loads were found on the stiffer structure with long insulators (including the horizontal strut) for galloping conductor and galloping static wire tests.

Longitudinal Dynamic Loading of a Steel Pole Transmission Line

Model test results have demonstrated that it is possible to simulate a number of dynamic loading conditions on a scale model of an actual transmission line system, taking into account a large number of variables, and producing results having direct interpretation at full scale. The method appears to be particularly useful in identifying any potential ``trouble areas'' in an existing design such as the use of horizontal struts on light angle structures, and/or adequacy of fatigue strength under galloping conditions. A sample of the principal findings of this investigation are as follows: 1) A method for rapidly calculating the flexibility (stiffness) of steel pole transmission structures has been developed. The method relies on computer print-out data supplied by pole manufacturers at the time of bid evaluation. 2) Results of broken static wire tests show that structure flexibility reduces both the dynamic load and the residual load below the load calculated for a rigid structure. 3) The maximum loads occur for broken static wire on the most flexible structure, and for ice unload of static wire on the stiffest structure. The latter result is subject to the further restraint of a horizontal strut at a light angle. 4) Unexpectedly high loads were found on the stiffer structure with long insulators (including the horizontal strut) for galloping conductor and galloping static wire tests.

Development and Installation of BPA's New Generation Transmission Conductors

The Bonneville Power Administration (BPA) has developed a family of new generation conductors which promises to reduce transmission line life-cycle costs. These trapezoidal wire conductors reduce air void area by 80 percent over conventional round rod conductors, allowing a denser packing of conducting material and greater efficiency through increased conductance and/or reduced tower loads. The trapezoidal wire family is made up of nine conductors ranging in size from 1.0 to 1.8 inches; six are all aluminum and three are aluminum with steel reinforcement. The new conductors are expected to satisfy all of BPA's typical conductor requirements for new construction, rebuild, and reconductoring projects, where the economics of resistive losses dominate the design. This paper introduces the new conductor family and assesses its uses and limitations. It discusses design details; mechanical, stress-strain, creep, and self-damping characteristics; and conductor sizing, procurement, handling and sagging, savings, and lattice steel and wood pole applications. It also describes the first use of the trapezoidal wire conductor family on the BPA Boundry Integration/Reinforcement Project.

Behavior of Anchored Foundations Subject to Shear and Moment Loads

The behaviour of a rock anchor cluster under shear and moment loads was investigated by full-scale field tests. These tests showed a complex failure mechanism in rock which varied with the combination of loading. Using simplifying assumptions a theory is proposed to predict the ultimate resistance of the anchor group against rock failure. A simplified procedure is outlined for designing the rock anchored footings for steel pole type transmission structures.

High‐strength/high‐modulus fibers of p‐phenylene oxadiazole/n‐methyl hydrazide copolymers—a new class of high‐performance organic materials

Abstractp‐Phenylene oxadiazole/N‐methyl hydrazide copolymers were prepared by polymerization of terephthalic acid, dimethyl terephthalate, and hydrazine sulfate in fuming sulfuric acid, and coagulation of the polymer was obtained in aqueous sulfuric acid. Fibers spun from these copolymers have unusually high strength and modulus, making these materials attractive for the reinforcement of articles such as tires. Yarn tenacities of 16–21 gpd and moduli of 350–450 gpd were obtained. Yarn of these copolymers showed no significant degradation under conditions to which a tire cord material is subjected in tire building and end use. In their performance in vehicle tires, tire cords were found to be competitive with other reinforcing agents such as fiber glass, steel, and commercial poly(p‐phenyleneterephthalamide).

Effects of an Electric Hexapole Lens in Mass Spectrometer

An electrostatic hexapole lens is used for the study to correct the image curvature resulting from second order aberration in a mass spectrometer. The mass spectrometer used is a Hitachi RMU-6D double focusing type especially attached a photographic detector. The hexapole lens is located between the electrostatic analyzer and the magnet at the distance 134 mm from the magnet. This lens consists of six stainless steel poles which are 6 mm in diameter, 40 mm long, and the distance from the symmetry axis to the nearest point of the electrodes is 7 mm. When the potentials of ±4.5 V are applied to the poles alternatively, the image curvature can be corrected without any additional effects of in-troduced abrerrations.

Effect of Conductor Imbalance on Flexible Transmission Structures

Methods of determining longitudinal tensions to be supported by flexible transmission structures, such as tubular steel poles, A frames, H frames, and similar two-dimensional structures, as a result of phase severance, or similar imbalance in one span of a series, are outlined. Tension reduction caused by insulator displacement plus the consequent structure deflection is determined.

Aluminum, Aluminized Steel And Galvanized Steel In Severe Coastal Environments

Abstract Aluminum, aluminized steel and galvanized steel pole line hardware were exposed in a severe marine environment near Kahuku Point, Oahu, Hawaii for three years. Variables included aluminizing process and type of base steel. Evaluation of samples after three years' exposure indicates: (1) the superior performance of all-aluminum hardware. (2) the improved corrosion resistance of aluminized steel to that of galvanized steel, and (3) the relationship between the thickness of aluminum coatings and the service life of aluminized steel hardware. Thicker aluminum coatings result in longer life. 2.2.2, 4.2.5, 6.4.2, 5.3.4

Tower Footing Corrosion

The measurement of the tower-to-soil potentials provides a means by which the condition of the galvanizing on underground portions of towers can be predicted with fair accuracy. The electropotential measurement technique has the advantage over the chemical and visual methods of being so rapid that many towers can be checked in the time it takes to examine one by either of the other methods. The potential measurement gives the over-all condition of the underground portion of the towers instead of the condition at the relatively small areas that it is practical to expose for visual observations or chemical test. The tower potentials at switching station ends of The Detroit Edison Company's transmission lines are much lower than those that are considerable distances from the stations. Potentials are also low for those towers situated near steel poles set in concrete and grounded individually. The low potential at the station ends is due in part to the fact that the grounding medium for the stations is massiv...

Distributing Electricity to Country Districts

DURING the last ten years, the distribution of electricity by means of overhead lines has made rapid progress; but there are still nearly 80 per cent of the occupied rural areas of England where electric supply is not available. There is a vast amount of development work to be done in these areas. Already the capital sunk for distributing power is considerably in excess of that used for generating power. The annual expense in distribution is at the present time three times greater than that for generation. The progress already made shows that there is plenty of scope for technical improvements which would increase the factor of safetv and lower the cost of supply. The rural schemes already installed prove that an overhead distribution at 11,000 volts (11 kv.) is economical when the loads are small. When heavier loads are anticipated, 33 kv. is generally adopted. In a paper by R. Dean read to the Institution of Electrical Engineers on May 15, the available data relating to rural design have been collected and the many numerical tables given will enable engineers to obviate many tedious calculations. Official regulations and a number of practical details in design are also given. For rural supply, it has been found that wood poles are the best. Both concrete and steel poles are about 12 per cent more expensive. The admissible factor of safety for wood poles has now been reduced to 3-5. At the time of constructing the 132 kv. grid, steel-cored aluminium was the most popular conductor to use, but the author's tables show that copper-cored steel or steel-cored copper provide rather cheaper lines. The requisite experience has not yet been obtained of the effects of electrochemical action on these lines after a number of years exposure to the weather. There are many subsidiary advantages in favour of steel-cored aluminium for high-voltage lines.

New Broadcasting Station at Budapest

THE authorities responsible for the broadcasting service in Hungary have always kept abreast of the latest developments in wireless technique; indeed, Budapest claims the distinction of being the first town in the world to inaugurate a system of broadcasting over wires so early as 1893. Budapest will again come into prominence in the near future on the opening of its new broadcasting station, with a transmitter power of 120 kw., and an aerial mast which is claimed to be the highest in the world. A brief description of this station and a photograph of the new mast is given in World Radio of November 10. The mast is of trellis-work steel construction, supported by two porcelain insulators on a solid block of concrete about twenty feet square. The shape of the mast is that of two elongated square pyramids, set base to base, and standing on one of the points, the whole structure being guyed at the centre point where the cross-section is a maximum. The height of the mast is 932 ft., but a telescopic steel pole at the top extends this to nearly 1,022 ft. or 310 metres. This height surpasses that of the Eiffel Tower by some 40 ft. and makes the mast the highest structure in Europe. The new transmitter, which is of British design built in the contractor's factory at Budapest, is situated in a building about half a mile away from the aerial, the radio-frequency power to which will be supplied through a suitable transmission line. The station is designed to supply an unmodulated carrier-wave power of 120 kw. into the aerial, and it will take over the wave-length of 550 metres used by the present transmitter. The latter, which has a power of 18-5 kw., will be retained for use on another wave-length to supply an alternative programme of less general interest than that provided by the main transmitter. The new station has already started testing at midnight, and it is likely that Radio -Budapest, which employs three women and two men announcers, will be one of Europe's best-received signals this winter.