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This paper introduces an innovative concept for the use of multispectral stereo pair of satellite images to identify dangerous trees and plants along overhead transmission rights of way. Multispectral satellite images of the right of way are scanned automatically and the color (wavelength) of each pixel is analyzed. This scanning identifies healthy vegetation which may contain trees that endanger the fine. Using multispectral stereo images, the height of each pixel is determined and the distance from the conductor is calculated. When this distance is less than the danger zone surrounding the conductors, the identified object or tree is assumed to endanger the fine. Case studies using satellite images in the vicinity of Scottsdale, AZ and San Diego, CA demonstrate the feasibility of the proposed method. Details are given for prototype software development for satellite image scanning to determine tree interference with overhead transmission lines. Index Terms--Overhead conductors, power transmission, satellite images, transmission engineering, tree trimming.

Increasingly dense residential housing developments have spurred new concerns about electromagnetic fields. The magnetic fields generated by the underground distribution system in such a residential subdivision are assessed in this study. In particular, the magnetic flux densities above the underground cables, around the padmount transformers and junction boxes, and at the service entrance panels are measured. The largest magnetic fields of 95 mG and 148 mG are recorded on the surfaces of the transformer enclosures and junction boxes, respectively, at around 30 % to 40% of full load. The magnetic fields reduce to less than 3 mG at a distance of ~1 m from the distribution system infrastructure. Software is developed to estimate the peak magnetic field generated at full load conditions by the underground cables composed of twisted conductors. Index Terms--Electromagnetic fields, magnetic fields, power cables, underground power distribution lines.

The introduction of computer-equipped classrooms into engineering education has brought with it a host of opportunities and issues. Herein, some of the challenges and successes for creating an environment for active learning within computer-based classrooms are described. The particular teaching approach developed for undergraduate electrical engineering courses is presented. Longitudinal assessment data regarding in-class utilization of computers in the context of achieving program and course learning outcomes are shared. Index Terms--Collaborative learning, computer utilization, educational technology, engineering education.

An environmental chamber has been constructed at Arizona State University to establish a long-term aging test of all-dielectric self-supporting (ADSS) fiber-optic cable. A polymer-jacketed ADSS (track resistant) cable is subjected to UV radiation, salt fog, clean rain, and mechanical tension in the aging chamber. Installed by the Bonneville Power Administration (BPA), a similar track resistant ADSS has been in operation for about eight years, near the Pacific Ocean at Bandon, OR. Accumulated pollution on this ADSS has been measured by BPA on approximately a semiannual basis. In this paper, the aging chamber operation is outlined briefly and two methods of measuring the accumulating pollution level on the ADSS cables in the aging chamber are described. The accumulated pollution levels of both ADSS cables in the chamber and in Bandon, OR, are compared. It is noted that general chamber performance compares favorably to the field data as well as suggesting an approximate chamber-aging rate, about 18:1. Index Terms--Aging, all-dielectric self supporting (ADSS), correlation, field, fiber-optic cable, measurements, pollution, transmission line.

Insulation is identified as one of the most important constructional rudiments of a transformer, and any weakness of insulation would lead to a transformer failure. To check the insulation integrity, a sensitive technique like the standard impulse test is used. Testing of winding insulation is performed by comparing the voltage and current waveforms of reduced and full test voltages, previously. Transfer function has been exercised via applying fast Fourier transform to analyze the transformer state in the frequency domain. In order to enhance the fault detection sensitivity in transformer impulse test, this paper proposes a new method using short time Fourier transform in the transfer function analysis, derived from experimental works on 25 kVA and 26 MVA transformers. It is concluded that the fault detection sensitivity is improved significantly by using STFT analysis, including minor faults. Index Terms--Faults, signature analysis, time-frequency representation, transformer.

Insulating links are used to protect crane workers from accidentally contacting a transmission line. This paper presents the results of laboratory tests that determined the leakage current produced by sudden energization of polluted and wet insulating links. Two different manufacturers' links were tested at heavy and light pollution. The results show that the short duration transient or the root mean square (rms) leakage current is the measure of the ability of the links to provide protection. The leakage current can endanger the life of a crane worker before flashover occurs. The dependence of leakage current on test voltage under heavy and light pollution conditions was determined. Obtained leakage current data was compared with IEC 479-1 standard, that provides health effect data. The link protects the crane worker, if the line voltage is less than the maximum voltage determined from the correlated test results. The results were used to assess the efficiency of worker protection. Index Terms--Crane, electrocution, flashover, fatal accident, fog chamber, insulator, leakage current, power line, pollution, wetting.

All Dielectric Self Supporting (ADSS) fiber-optic cable jackets aer subject to dry band arcing associated with wet, conductive pollution, quantified electrically by ohms per meter, in conjunction with the location of the ADSS in relation to conductor placement on high-voltage transmission structures. In order to determine the suitability of a particular ADSS jacket material to resist dry band arc damage in various levels of pollution as well as for incipient voltage levels, an electrical test, employing equivalency to the dry band environment, has been proposed. A set of desirable hypothetical results are briefly discussed. The tests results described herein, for common polyethylene jacketed ADSS, support the nature of the hypothetical data. It is noted that this is not 'pass-fail' but a test that stablishes performance criteria. It has been submitted to the fiber optics standards working group. Index Terms--ADSS, aging, dry-band arcing, failure, fiber-optic cable, transmission line.

Deregulation of telecommunication networks and utility companies has led to a worldwide increase in the use of fiber optic cables on long-span overhead power transmission lines. The cable jacket is subject to the deterioration caused by dry-band arcing, which is believed to be the major cause of failure of cable in service. This paper establishes an arc model based on the physical mechanism and experimental observation, and performs simulation of the transient of dry-band arcing on ADSS fiber optic cable. The basic theories concerning the dynamics of arc, arc extension along the electrolytic surface and its speed, and dry-band arcing on ADSS cable are reviewed. The differential equation systems composed of the dynamic equation of the arc and its interaction with the circuit components are proposed with state variable method. And the equations are solved numerically with Runge-Kutta method. The proposed differential equations can be used to simulate dry-band arcing on experimental setup in laboratory and predict the dynamic behavior of dry-band arcing on ADSS cable in transmission network. Hence the damage caused to cable can be evaluated. Experiments are performed to verify the simulation results. Index Terms--ADSS, arc model, arc simulation, dry-band arcing, fiber-optic cables, flashover.

All dielectric self supporting (ADSS) fiber optic cables are suffering from damage caused by dry-band arcing. This paper investigates the formation of the dry band, which is crucial to the arcing. The formation of the dry band is the result of evaporation of water deposit some point on the cable surface. When the dry band is formed the current is interrupted. Then high voltage is applied to the small gap separated by the dry band, and may cause arcing. This paper discusses the drying process of the wet layer on the surface of the cable in detail. The differential equation of the drying rate is formulated and numerical simulation is performed. With this equation, the time-to-arcing and variation of the layer resistance can be estimated. For verification of the results, the time-to-arcing and layer resistance are measured in the laboratory. The numerical results provide guidance for design of an automatic dry-band arcing aging test system. The onset of arcing is investigated based on the results. Index Terms--ADSS, fiber optic cable, dry-band, arcing, drying rate, layer resistance.

A series of simulated arcing experiments are conducted in a laboratory setting to investigate the characteristics of dry band arcs on ADSS fiber optic cables. The measurement of resistance, power, and energy of dry band arcs is described. The impact of voltage and current on arc resistance is presented. The power and energy of dry band arcing is measured under different short-circuit current and open-circuit voltage. An Equation which relates arc power to open-circuit voltage and short-circuit current is proposed. Experiments show that arc power has a threshold to cause the damage of cable jackets. The study of arc power and energy can be used to predict a potential damage of ADSS cables. Index Terms--Aging, dry-band arcing, failure, fiber-optic cable, transmission line.

Utilities frequently install All-Dielectric Self-Supporting (ADSS) fiber-optic cables on transmission lines. The cable jackets suffer damage due to dry-band arcing caused by high electric fields and pollution on the cable. A test method to determine cable resistance to dry-hand arcing is being considered for standardization by the IEEE. A new nozzle arrangement for the test is proposed in this paper. Using this nozzle the repeatability of the test is significantly improved over previous arrangements. Each test cycle consists of three stages: wetting, drying, and arcing. The three stages are examined in detail. Development of the dry-band arc on the cable jacket during the arcing period is presented. It is shown that the length of the are increases exponentially with time and reaches a stable length. The stable length is shown to be a function of the applied voltage. Index Terms--Arc discharges, optical fiber cables.

This paper presents a novel interactive teaching method utilizing computers to improve engineering education. The course material is divided into units covering major topics. First, the hardware related to the topic is presented using Power-Point slides and industry-furnished videos. This is followed by a presentation of the theory. Then the students, who use computers, jointly derive the equations and their practical applications. In a computer-equipped classroom, the instructor outlines each step of the analysis, and then the students proceed to develop the equation(s) using their computers. After a few minutes, the instructor confirms the equation and the students make corrections. The knowledge expected from the students is summarized at the end of each unit in the form of questions. Instead of a final exam, each student has to pass a test at the end of each unit. The unit exam has a calculation and an essay part. The teaching effectiveness is assessed with questions that the students answer before and after the completion of the unit of study. The method has been partially tested with promising results. Index Terms--Cooperative learning, electric power education, interactive learning, technology-enhanced classroom.

The paper describes the use of general-purpose mathematical software 'GPMS' as a major advancement in simplifying simulation procedures for junior level engineering studies. GPMS handles general and specific mathematical formulas and is packed with a vast array of codes to perform many scientific and engineering functions in an interactive mode. In order for the student to interact positively, the numerical examples in the textbook must be converted into an interactive media to support the theory and provide a deeper understanding of the physical phenomena. By this method, the students enhance their problem-solving abilities with minimal programming skills. By using examples, the paper presents an approach to computer-aided problem solving methods for junior level courses. The methods described in the paper have proven to be of value to students studying electric machines and power engineering at Arizona State University. Index Terms--Computer aided education tools, computer application, electric circuit, energy conversions, MathCad, teaching.

Generator tripping is one of the most effective approaches to enhance the transient stability of a power system. In this paper, an online prediction method of transient stability and an offline analysis method of generator tripping are studied respectively. First, a polynomial curve fitting technique is employed to improve the online prediction accuracy of system stability. Then, a shell program is developed to automatically generate and update look-up tables for generator tripping. Based on these, a hybrid method is proposed. It uses the look-up tables to determine generator tripping requirements and before sending out generator tripping signals, instability is confirmed by online prediction of system stability. Simulation results show that this hybrid method can avoid unnecessary generation shedding. Index Terms--Curve fitting, generator tripping, offline look-up table, online stability prediction.

The measurement and analysis of leakage current (LC) for condition-based monitoring of, and as a means of predicting flashover of polluted insulators has attracted a lot of research in recent years. Results presented in the technical literature show that surface arcing of contaminated insulators causes significant variations in the magnitude and shape of the insulator's leakage current and several techniques have been proposed for analysis. This paper submits the results of applying linear stochastic and statistical (probabilistic) analysis as a signature analysis tool for flashover prediction. A new twist is presented based on statistical analysis of the leakage current envelope (rather than just instantaneous peak values), in particular, level crossings, mean exceedances over high thresholds, and extreme value analysis of the envelope. The analysis was performed offline using digitized samples of leakage current obtained from a data-acquisition (DAQ) system, which continuously scans the leakage current during flashover tests in a laboratory fog chamber. Index Terms--Envelope, extreme value, insulators, leakage current, pollution, signature analysis.

Deterioration of ADSS (All Dielectric Self-Supporting) fiber optic cable jacket material has been reported near the tips of armor rod assemblies installed of high voltage transmission lines. Field observations and laboratory tests revealed that corona can exist on the tips of the armor rod. Electric field analysis reported herein reveals that the tip surface gradients are high enough to produce corona. Field conditions have been duplicated in a high voltage test chamber and jacket damage has been observed near generated corona. The deterioration mechanism is identified and jacket life expectancy is estimated. Different mitigation techniques are suggested. Keywords: fiber-optic cables, high electric field, corona, discharge, failure

This paper presents the performance evaluation of an active power filter that uses a five-step current source inverter. The use of a multi-step inverter implies lower frequency switching, thereby allowing the introduction of higher power switching devices. The control filter uses a frequency domain approach in which line current harmonics are extracted using an FFT routine. A compensating current related to the harmonic components of the load current is generated. This compensating current is injected at the point of common coupling to cancel the load current distortion. The algorithm used to generate the compensating function is presented and the system's ability to reduce current harmonics with lower frequency switching is demonstrated through simulations and a low power prototype. Keywords: Active power filters, power conditioners, harmonic compensation.

This paper investigates the feasibility of magnetic fields reduction by optimization of phase relationships in a multi-circuit underground cable system, carrying unbalanced loads. A novel algorithm was developed for fast calculation of the multi-circuit cable system generated magnetic field. The unbalanced load was modeled by random selection of phase current values. A computer code was written to calculate the statistical distribution of the magnetic field above the cables on the ground level. The program calculates the maximum magnetic field for different phase relationships and selects the optimum phase relationship. Several multi-circuit cable systems used by utilities have been analyzed. The results show that the optimization of phase relationships effectively reduces the magnetic field for cable systems with both single and multi-point grounded sheaths in spite of the load unbalance.

This paper examines the economic impact of inaccurate load forecasts. Monte Carlo simulations were used to study the effect of different load forecasting accuracy. Investigations into the effect of improving the daily peak load forecasts, effect of different seasons of the year and effect of utilization factors are presented.

The reduction of magnetic fields is a topic of concern to the electric utility industry and the electromagnetic compatibility community. One technique to reduce the magnetic fields is to use metal plates and enclosures for shielding. In addition, knowledge of the loading effect of a conducting structure in close proximity to power cables is needed for estimating power loss. Until now there has not been a simple and efficient method to calculate the low frequency magnetic shielding of, nor power loss caused by, two-dimensional shields. This paper presents a method for the rapid numerical estimation of the magnetic shielding efficiency and power loss of nonferrous metal structures. The method was validated analytically and experimentally.

This letter presents a novel method to include the uncertainties of the weather-related input variables in neural network-based electric load forecasting models. The new method consists of traditionally trained neural networks and a set of equations to calculate the mean value and confidence intervals of the forecasted load. This method was tested for daily peak load forecasts for one year by using modified data from a large power system. The tests indicate that in addition to the confidence interval, the new method provides a more accurate mean forecast than a multilayer perceptron networks alone.

Contact between cranes and transmission lines is the most frequent cause of accidents, which may lead to electrocution of an operator or rigger. This accident can be prevented by inserting an insulating link in the crane's cable. This paper analyzes currents during accidents and proposes a modified test method for contaminated insulating links. A new and better insulating link is also introduced. Flashover probability of contaminated insulator links is measured. The test results are evaluated with a new probabilistic method which leads to better assessment of link efficiency. The paper concludes that the risk of link failure cannot be determined without the new flashover probability measurement. Key Words: Composite insulators, crane, pollution flashover, electrical accident, risk analysis.

Flashover mechanisms of silicone rubber used for outdoor insulation is presented and experimentally proven. A hydrophobic surface of silicone rubber wets and accumulates contaminants differently compared to conventional porcelain and glass insulators. This suggests that the flashover mechanism of silicone rubber insulators is different than porcelain and glass. This paper (Part II) experimentally investigates ohmic heating, electrical field caused interaction between water droplets, generation of conductive regions and filaments, field intensification caused spot discharges and the ultimate flashover of silicone rubber along wetted filaments. These studies have resulted in a new flashover mechanism which provides a better understanding of silicone rubber outdoor insulators and their excellent contamination performance. These results will be used for the development of a better laboratory test procedure to evaluate composite insulators' performance in contaminated conditions. Key Words: Silicone rubber insulator, spot discharges, flashover

Experimental results show that the contamination performance of silicone rubber composite insulators is better than porcelain insulators. This is attributed to the hydrophobicity of the silicone rubber. This suggests that the flashover mechanism of these insulators is different. This paper experimentally investigates contamination build-up, diffusion of low molecular weight (LMW) polymer chains, surface wetting, electrical field caused interaction between droplets, generation of conductive regions and filaments, field intensification caused spot discharge and the ultimate flashover of silicone rubber along wetted filaments. The studies resulted in a new flashover mechanism, which provides a better understanding of the superior performance of silicone rubber outdoor insulators. The results will be useful for development of improved laboratory test procedures and to evaluate composite insulators' performance in contaminated conditions. The paper is divided into two parts: Part I describes the overview of flashover mechanism and the diffusion of LMW polymer chains and wetting of the silicone rubber surface in detail. Key Words: Flashover, Silicone Rubber Insulator, Wetting.

The paper describes a novel test arrangement to characterize the temperature dependence of partial discharge (PD) inception voltage in capacitors. The test arrangement consist of a temperature chamber, HV supply and PD detection circuit. The corona free operation voltage is 0 to 3.6 kV, temperature range is -50 to 200 [degrees] C. Different type of capacitors PD inception voltage were measured at different temperatures. It was found that most commercial capacitor PD was lower than the rated voltage and increased by the temperature. In contrast, the higher quality chip type ceramic capacitor PD was above the rated voltage and decreased with the temperature. The paper concludes that the prediction of capacitor performance requires the measurement of PD at different temperatures.

The current ANSI/IEEE standard specifies two possible methods for magnetic meter calibration: a single square loop or a round Helmholtz coil. However it (a) does not specify the size of the coil and (b) does not provide a comparison of the field uniformities between the two suggested systems. In this paper, the z-directed magnetic field equations for four calibration system designs, the single round loop, the round Helmholtz coil, the single square loop, and the square Helmholtz coil are derived and presented. For the square systems, this paper presents the derivations for the first time in the open literature. Also, this paper is the first to present a comparison of the field uniformities of the four systems.

The results of an experimental study of the 60 Hz ac corona inception voltage at reduced pressures for a cylindrical conductor and a parallel ground plane are presented. Several spacings and bare and insulated conductors of several diameters are considered. Empirical expressions from which a reasonably accurate prediction of the corona inception voltage (CIV) may be made have been inferred from experimental data.

This paper presents a new method for the continuous regulation of series compensation. The two proposed control circuits consist of capacitor banks inserted in a transmission line and are controlled by bi-directional GTO switches. The level of compensation is controlled by varying the on and off time of the GTO switch. To avoid current surge, the switch is turned on before the capacitor voltage is zero. The feasibility of this method was verified by transient analysis and through measurements on a small scale model. The advantage of the proposed circuit is the fast and continuous regulation of series compensation. The circuit can be built with available components and can be used, for example, for impedance control, and oscillation reduction.

This paper presents a new method for the continuous regulation of reactive power generated by a capacitor bank. The two proposed control circuits consist of capacitor banks controlled by bi-directional switches which are built with anti-parallel connected thyristor and GTO valves, or with two GTO valves. The current of the capacitor is regulated by turning off the GTO switch before zero current crossing. By turning off the current, charge is trapped in the capacitor, resulting in a constant capacitor voltage. To avoid the current surge, the switch is turned on when the supply and capacitor voltage are equal. The current regulation is achieved by switching off the current for a part of each cycle. The feasibility al the method has been verified by extensive transient analysis. The advantage of the proposed system is the fast and continuous regulation of reactive power without inductance. The system can be built with commercially available components and used for voltage support, power factor correction, etc.

This letter presents a new method to perform transient stability analysis of a system using reconfigurable analog VLSI. A novel concept for reconfiguring system parameters has been developed and tested using a one generator infinite bus system. Index Terms--Generator model, real-time, reconfigurable analog VLSI, transient stability analysis.

Byline: George G. Karady, Gerald Thomas Heydt The objective of this research is to investigate innovative power distribution components based on micro-electromechanical systems technologies integrated with advanced optimisation methods to improve the performance of electric power distribution systems. A novel medium voltage circuit breaker using two switching string assemblies has been developed. The building block is a switching unit, which includes micro-switch shunted by a diode and a resistance. Several switching units are connected in series to form the switching string and several strings are connected in parallel to form the switching string assembly. A magnetic coil activates the switches. The circuit breaker contains two switching string assemblies connected in series. One of them interrupts the current in the positive the other in the negative cycle. The opening of the mechanical switches transfers the current to the diodes, without any arcing. The diodes interrupt the current at zero crossing. The project objective includes an educational component: to bring innovative topics in power distribution engineering to practising engineers (e.g., continuing education) as well as engineering students. The design appears to be a logical step in innovative power circuit breaker design that allows better control of circuit interruption than conventional breakers.