Buried Cables Research Articles

Inductive interference caused to telecommunication cables by nearby AC electric traction lines. Measurements and FEM calculations

The paper investigates the inductive interference caused by AC electric traction lines to nearby buried telecommunication cables. Measurements according to the directives of the International Telecommunication Union (ITU) and calculations using the finite element method (FEM) are presented for a real system. This system consists of an AC electric traction line of the Greek Railways Organization and a buried cable of the Greek Telecommunications Organization. Finally, an analysis concerning the most important operational parameters in determining electric traction line influence is presented. Such parameters are the separation distance between the electric traction line and the buried telecommunication cable, the earth resistivity as well as the number and the material of the mitigation wires.

Effects of soil warming during spring on photosynthetic recovery in boreal Norway spruce stands

AbstractThe effect of soil thawing and soil temperature on postwinter recovery of photosynthetic capacity was studied, during late spring and early summer, in Norway spruce stands in northern Sweden. Soil temperature was manipulated by means of buried heating cables. The warming treatment was applied to stands with low (natural) and high (fertilized) availability of nutrients. Soil thawing, expressed as water availability, was followed by means of sapflow in stems, and shoot water potentials. The recovery of photosynthetic capacity was assessed by measuring the rate of light‐saturated photosynthesis (Amax), and maximum photochemical efficiency of photosystem II in detached shoots, and chlorophyll a fluorescence. Accumulation of starch reserves in the needles was followed as an independent indicator of photosynthetic performance in situ. Snowmelt and soil thawing occurred more than one month earlier in heated than in unheated plots. This was expressed both as sapflow and as differences in shoot water potential between treatments. During May, the rates of Amax were significantly higher on heated than on control plots. The effect of soil warming on Amax was, however, not reflected in chlorophyll fluorescence or needle starch content. The time course of the recovery of photosynthetic capacity was mainly controlled by mean air temperature and by the frequency of severe night frosts, and to a lesser extent by earlier soil thawing and higher soil temperatures.

Resource Sharing: Wireless Telecommunications Site Lease Rates

“Resource sharing” refers to projects that use public right-of-way for telecommunications facilities and that result in some form of compensation to the public agency. The facilities most often installed are transmitter antennas supported on aboveground structures (wireless facilities) or buried fiber-optic cable. Research indicates that fewer than 10 state departments of transportation (DOTs) are leasing or licensing wireless sites to telecommunication companies, but many more states desire data concerning the revenue that they might receive from such installations. The current range of fees that state DOTs receive from the telecommunications companies for the wireless sites, and the fees that the DOTs receive from other companies (colocators) that place their facilities on a structure owned by a first locator, are described. The typical site locations, the group (DOT versus company) that identifies lease sites, typical support structures for the antennas, the manner in which the revenue may be used in the various states, and legal difficulties associated with wireless resource sharing are also described.

Time evolution of polarization mode dispersion in optical fibers

The fluctuation of polarization mode dispersion (PMD) due to environmental change is an important issue for fiber-optic communication systems. We measure the time evolution of PMD for installed aerial and buried cables and for a spooled fiber in a temperature controlled chamber. The results show that PMD fluctuates much more rapidly for aerial cables than for buried cables. The magnitude of PMD is different for the three fibers and our results also show that the magnitude of PMD fluctuation depends on the magnitude of the PMD.

The detection of cylindrical objects of low acoustic contrast buried in the seabed

It is anticipated that the next generation of submarine fiber-optic telecommunications cables will be invisible to present-day detection systems. In cooperation with Cable and Wireless (Marine) Ltd., research has been conducted into the remote detection of buried objects of low acoustic contrast, with particular emphasis given to the detection of buried cables. Specifically, this has concerned the design of a detection system that can reliably discriminate a small diameter (cm scale), cylindrical target buried to a depth of up to 1 m below the seabed from a range of 1 m above. A purpose-built, laboratory-scale, automated sensing system comprising a bistatic arrangement of adjustable, focused transducers is described. This apparatus has been used successfully in the high-resolution imaging of a range of buried objects, proving an acoustic detection system to be a feasible solution. Recent experimental investigations have focused on two areas: Waveform optimization techniques, to maximize seabed penetration and target interaction, and matched filtering and clutter reduction techniques, to optimize the detection system to the acoustic signature of a particular buried object. Results are presented.

Advances in ported coaxial cable technology

Ported coaxial sensors for outdoor intrusion detection have been commercially available since the late 1970's. Also known as cable and guided radar sensors, the technology uses buried leaky coaxial cables to establish a terrain-following covert detection zone. By operating in the Very High Frequency (VHF) band, these sensors operate under all-weather conditions and have superior detection and false/nuisance alarm performance compared to other technologies. In addition, the technology has been independently evaluated as having the lowest available vulnerabilities to defeat. In 1995, Senstar Corporation announced, in a precursor to this paper, the development of a new generation of ported coaxial sensors. This new generation featured the availability of a novel leaky design that combines both transmit and receive elements in a single jacketed for ease of installation. A new concept for the sensor was also presented, that results in significant performance improvements, and offers a highly modular system architecture for ease of application. This paper reports on the next step in realizing this new generation of ported coaxial sensors, called Perimitrax. Included is an overview of the system architecture which has resulted from the detailed engineering design and a discussion of the major system design decisions that were made. A detailed description of each of the system building blocks is provided as is a number of examples of typical system configurations.

Thermal performance of underground power cables with constant and cyclic currents in presence of moisture migration in the surrounding soil

A numerical methodology for thermal analysis of buried power cables in presence of heat and moisture migration in the surrounding soil is presented. The governing equations are solved via a finite volume methodology and both cable and soil are incorporated in the problem formulation. The developed program is versatile and user-friendly, and was implemented in a personal computer. Results are presented for constant and cyclic loads, stressing the importance of moisture migration in power cable design.

Interference of nonlinear ferromagnetic pipeline on magnetic field produced by power lines

The investigation of the magnetic field produced by power lines has drawn a lot of attention from researchers. Since sharing space by buried power lines and pipelines has become commonplace, it is of interest to investigate the influence of the pipeline. In this paper, we study the change of the magnetic field produced by buried cables, due to an additional steel pipe nearby. A Fourier series technique is used to calculate the magnetic field. An iterative procedure is employed to handle the nonlinear characteristics of the steel pipe and to determine the varying permeability in it. The calculated results of the magnetic field are compared with those produced by buried cables without the additional pipe. The comparison shows that the steel pipe close to buried cables may significantly alter the magnetic field.

Responses of Trace Gas Fluxes and N Availability to Experimentally Elevated Soil Temperatures

We are conducting a field study to determine the long—term response of belowground processes to elevated soil temperatures in a mixed deciduous forest. We established 18 experimental plots and randomly assigned them to one of three treatments in six blocks. The treatments are: (1) heated plots in which the soil temperature is raised 5°C above ambient using buried heating cables; (2) disturbance control plots (cables but no heat); and (3) undisturbed control plots (no cables and no heat). In each plot we measured indexes of N availability, the concentration of N in soil solutions leaching below the rooting zone, and trace gas emissions (CO2, N2O, and CH4). In this paper we present results from the first 6 mo of this study. The daily average efflux of CO2 increased exponentially with increasing soil temperature and decreased linearly with increasing soil moisture. A linear regression of temperature and the natural logarithm of CO2 flux explained 92% of the variability. A linear regression of soil moisture and CO2 flux could explain only 44% of the variability. The relationship between soil temperature and CO2 flux is in good agreement with the Arrhenius equation. For these CO2 flux data, the activation energy was 63 kJ/mol and the Q10 was 2.5. The daily average uptake of CH4 increased linearly with increasing soil temperatures and decreased linearly with increasing soil moisture. Linear regression could explain 46% of the variability in the relationship between temperature and CH4 uptake and 49% of the variability in the relationship between soil moisture and CH4 uptake. We predicted the annual CO2 flux from our study site in 1991 using two empirical relationships: the relationship between air temperature and soil temperature, and the relationship between soil temperature and CO2 flux. We estimate that the annual CO2—C flux in 1991 was 712 g/m2 from unheated soil and 1250 g/m2 from heated soil. By elevating the soil temperature 5°C above ambient, we estimate that an additional carbon flux of 538 g°m—2°yr—1 was released from the soil as CO2.

Lightning-originated tangential electric field across air-soil interfaces

The electric field tangential to the ground plane generated by an upward-going lightning current is carefully estimated. The analytical essence of this technique leads to closed forms including the short-range case. Hence, using some basic coupling procedures, the near-field interferences on buried equipment have been treated. The investigation is ultimately addressed to insulation design and protection measures, and some unexpected, severe effects, induced in particular in buried cables, are predicted.

Thermal analysis of power cables in multi-layered soil. I. Theoretical model

The heat dissipation and temperature distribution in multilayered soil surrounding a buried cable are calculated using the finite difference method and the energy conservation principle. The numerical technique proposed is very suitable for modeling any real cable installation configuration in multilayered soil. The development of the model and the effect of the parameters that influence the conversion and the stability of the numerical solution of the heat dissipation from the underground cable system are studied. >

Soil warming and trace gas fluxes: experimental design and preliminary flux results

We conducted several experiments to determine a procedure for uniformly warming soil 5° C above ambient using a buried heating cable. These experiments produced a successful design that could: 1) maintain a temperature difference of 5° C over a wide range of environmental conditions; 2) reduce inter-cable temperture variability to ca. 1.5° C; 3) maintain a temperature difference of 5° C near the edges of the plot; and 4) respond rapidly to changes in the environment. In addition, this design required electrical power only 42% of the time. Preliminary measurements indicate that heating increased CO2 emission by a factor of ca. 1.6 and decreased the C concentration in the O soil horizon by as much as 36%. In addition, warming the soil accelerated the emergence and early growth of the wild lily of the valley (Maianthemum canadense Desf.). The relationship between CO2 flux and soil temperature derived from our soil warming experiment was consistent with data from other hardwood forests around the world. Since the other hardwood forests were warmed naturally, it appears that for soil respiration, warming the soil with buried heating cables differs little from natural, aboveground warming. By warming soil beyond the range of natural variability, a multi-site, long-term soil warming experiment may be valuable in helping us understand how ecosystems will respond to global warming.

Transient ratings of buried power cables. I. Historical perspective and mathematical model

The authors report the results of a recently completed major project on power cable transient calculations. It used a fundamental analytical method using a lumped parameter model for computation of transient ratings of buried power cables. An account is given for past work in the field of thermal transients in buried cables. A full description of the mathematical model is given. A summary of the state-of-the-art is provided. Developments relevant to the analysis of groups of unequally loaded and/or dissimilar cables and cables located in ductbanks or thermal backfills are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Nuclear Electromagnetic Interaction and Coupling Analysis in Buried Cables

A model is presented for numerically calculating the transient currents and voltages Induced in the buried cables by an impinging Nuclear Electromagnetic Pulse (NEMP). The conventional transmission...

Location of partial discharges in shielded cables in the presence of high noise

Updated information on a partial discharge location system intended to pinpoint the location of defects and/or faults on a shielded buried underground cable is presented. The system is based on the principle of reflectometry. Its salient characteristics include the following two features: (a) an ability to pinpoint the location of a partial discharge source not only along the cable length, but also along the surface of the trench where it is buried; and (b) the ability to operate in a high noise environment. Recent field and laboratory data obtained on noise and techniques for its mitigation are discussed in some detail. These techniques include analog/digital notch filters for the elimination of AM broadcast noise and an adaptive digital filtering scheme which incorporates the transfer function of the cable for added accuracy. >

Health and Safety Training for Underground Storage Tank Removal

Abstract The 1984 Hazardous and Solid Waste Amendments have launched a national effort to remove underground storage tanks (USTs) and to upgrade existing sites. The objective of this research was to determine the extent of the hazards in UST removal and to develop a 40-hour training course for employees involved in UST removal. Reports from the Occupational Safety and Health Administration (OSHA) database of fatalities and injuries caused by explosions, confined space entry, electrocution, and cave-ins during UST removal operations and similar activities underscore the hazardous nature of UST removal. Leak detection, prevention, tank cleaning, and closure may fall under the scope of 29 CFR 1910.120, Hazardous Waste Operations and Emergency Response, and thus be subject to employee training requirements. Topics typically covered in 40-hour hazardous waste training are not sufficient for UST removal employees, who require additional emphasis on cave-ins, tank pressure testing, tank entry, toxicity of petroleum products, flammable liquids, tank purging and inerting, drilling rigs, compressed air lines, overhead electrical lines, and buried utility cables. A 40-hour training course for UST removal supervisors was developed, using as a foundation a 16-hour U.S. Environmental Protection Agency training course for state UST inspectors and materials adapted for use in UST training. Respirator training, basic training in handling hazardous wastes, field exercises, and first aid/CPR training comprised the additional hours required to meet the 40-hour training requirement of 29 CFR 1910.120. OSHA has published proposed rules amending 29 CFR 1910.120(e), Training, and adding 29 CFR 1910.121, Accreditation of Training Programs for Hazardous Waste Operations. These proposed rules require that workers receive training in an accredited program and describe the accreditation procedures. The specific course content required in 1910.120(e) contains many topics of direct concern to UST operations; however, the requirement that topics such as laboratory waste pack and drum handling procedures must be included reduces the time available in a 40-hour format to cover UST-related topics. The author recommends 1) that specialized training which recognizes the specific hazards of UST removal should be made available for UST removal workers and 2) that this training should be eligible for accreditation under 29 CFR 1910.121.

Physical interpretation of inductive interference of power systems on communications circuits

A tutorial on the physical process by which power lines induce interference in neighbouring buried communications cables is presented. The discussion is based on the interpretation of existing models and a plausibility argument for the current distribution in the earth below a transmission line. This leads to a simple model for inductive coupling, which can be used to predict the inductive influence of lines without recourse to numerical evaluation. A new measure of the inductive influence of transmission lines is proposed, which is based on a large separation approximation to the mutual impedance and includes the effect of conductor height, earth resistivity and current sequence.

Burns from buried electric cables

Twenty-six patients who sustained significant burn injuries as a result of striking underground electric cables are reviewed. This study sets out to highlight why such injuries occur and to recommend preventive measures to those digging in the London area. There were three deaths in this series.

Simulation of SREMP Coupling to Buried Cables

Experimental results that simulate SREMP coupling to buried cables are presented for bare wires, branched wires, and coaxial wires. Comparisons with two theoretical approaches are presented for bare wires, and excellent agreement is obtained with test results.

Meeting the Fiber Optic Challenge with Vibratory Cable Plows

To date, much of the installed direct buried fiber optic cable has been placed by large crawler-mounted plows. However, in many areas, such as along highway rights-of-way and other routes with numerous road crossings, smaller-sized rubber-tired machines would be advantageous. Four-wheel drive vibratory cable plows have been utilized extensively by the telecommunications industry when installing copper cable, but there has been a general concern about vibration potentially damaging fiber optic cable. In order to overcome these fears, a test program was conducted in cooperation with a major cable manufacturer. Tests showed that tension required to feed fiber optic cable through a vibrated fixed-feed tube blade was much less than for isolated and static feed tubes. Operations stretching the limits of good installation practices, such as cable bend ratios as small as 4.5:1 and vibrating in place for 30 seconds, did not damage loose tube fiber optic cable under low tension. For better industry acceptance, special plow blade feed tubes and cable guides were designed, patterned after published recommendations. These were evaluated in a field trial and have since seen application in numerous successful installations of fiber optic cable.