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Power Delivery, IEEE Transactions on

Issue 2 • Date Apr 1990

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Displaying Results 1 - 25 of 92
  • New MV cable design for wet environments in underground distribution systems

    Publication Year: 1990 , Page(s): 787 - 793
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    The development of new wet design MV power cables, up to 35 kV, using EPDM compound as insulation and longitudinal water tightness is discussed. The combination of the cable design and the type of insulation compound makes it possible to reduce the insulation thickness in such a way as to have an electrical stress at the conductor of 4 kV/mm, which is significantly greater than that used in MV distribution cables. The reliability of this design, the cable, and EPDM's formulation was demonstrated in a wet location, without metallic water barriers. The mini-installation of model cables in servicelike conditions to estimate the ageing rate is presented and discussed View full abstract»

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  • Aging of distribution composite insulators under environmental and electrical stresses

    Publication Year: 1990 , Page(s): 1074 - 1077
    Cited by:  Papers (13)
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    Seven types of commercially available distribution composite insulators with sheds made of EPR (ethylene-propylene rubber) or epoxy resin were subjected to various functional aging tests recommended by the IEC or the IEEE. The influence of ultraviolet (UV) radiation on the aging of the shed materials was also evaluated. The usefulness of the various aging and diagnostic tests is discussed, and a modification of the recommended test procedures is proposed in order to improve the evaluation of the long-term performances of these insulators. The aging test methods and the acceptance criteria proposed by the IEC and the IEEE are not sufficient to discriminate between the seven insulator types tested. Extending the aging test duration to 2500 h and using the IEC water immersion test as a diagnostic tool brought out differences in the performances of the insulators. No significant synergism was found to exist between the UV radiation and the stresses caused by the salt fog test or the tracking wheel test when they are applied sequentially View full abstract»

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  • Polymer insulator profiles evaluated in a fog chamber

    Publication Year: 1990 , Page(s): 1078 - 1085
    Cited by:  Papers (18)
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    The authors present the results of fog chamber experiments done to examine the tracking and erosion performance of polymer insulator profiles. The effect of weathershed material, construction, orientation, and AC and DC voltage are examined. Correlation between cylindrical rod specimens of materials and insulator profiles is shown. The protected leakage path provided by the weathershed is found to play a major role in the tracking and erosion performances of polymer insulators. The resistance to tracking and erosion of insulator profiles with DC is shown to be reduced in comparison to AC. Cylindrical rods of material yielded the same ranking of material performance as insulator profiles but in a shorter time View full abstract»

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  • Life cycle economics of wood pole utility structures

    Publication Year: 1990 , Page(s): 1040 - 1046
    Cited by:  Papers (4)
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    The economics of life-cycle management of wood pole utility structures is discussed. Recently developed technology which enables innovative management techniques for wood poles is discussed. Results of full-scale tests of in-service wood poles which provide important information on rates of pole degradation are reviewed. These data enable realistic cost assessments for frequency of pole replacement and/or repair. Methods for calculating life-cycle costs are presented View full abstract»

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  • Unique aspects of distribution system harmonics due to high impedance ground faults

    Publication Year: 1990 , Page(s): 1086 - 1094
    Cited by:  Papers (31)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    The effects of the many sources of harmonics which occur on distribution systems are discussed and contrasted with the single source of harmonics from a high-impedance ground fault. Field data are presented which show the complexity of modeling the ambient harmonics and the simplicity of the change in the phasor value of the third harmonic which occurs due to a high-impedance ground fault. This phasor change is shown to be unique and predictable and hence suitable for use in detecting these faults. It is shown that variations in ambient harmonics may be greater than the change due to a high-impedance ground fault and must be considered in the fault detection system. Calculations of fault current harmonics are simpler than those for the ambient harmonics View full abstract»

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  • Resettable economical fault current interrupter for taps of a padmounted switchgear package

    Publication Year: 1990 , Page(s): 961 - 965
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    A resettable overcurrent protective device has been developed for padmounted switchgear packages. A low-Curie-temperature alloy and permanent magnet latch provide a simple, direct sensing and tripping means. Electromagnetic trip action at high fault currents causes two-cycle interruption to be attainable with the vacuum bottle and spring actuated mechanism. Linkage can be incorporated to provide three-phase tripping with single-phase fault detection View full abstract»

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  • Reduced neutral XLPE cable design

    Publication Year: 1990 , Page(s): 794 - 798
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    The authors describe the theoretical, laboratory, and economic analyses undertaken by B.C. Hydro to determine the optimum metallic concentric neutral design for its single-conductor 750 and 500 kcmil aluminum XLPE (cross-linked polyethylene) 15 kV and 25 kV insulated concentric-neutral-type feeder cables. The results suggest that reducing the cross-section area of this concentric neutral from the currently recognized industry standard of 20% of the central conductor to 7% results in an overall present-worth system cost saving of approximately $3 per conductor meter or approximately 22% of the cable first cost. The neutral configuration ultimately chosen to replace the previous standard 37#14 AWG wires was two 1-in×5 mil tinned copper tapes overlapped by 25%. Line voltage fault tests were run in the high-power laboratory on samples with various neutral configurations to confirm that they would successfully pass the worst-case fault duty of 10 kA for 20 cycles (i.e. .33 s) with no reclosing View full abstract»

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  • Coordination of MOV type lightning arresters and current limiting fuses

    Publication Year: 1990 , Page(s): 966 - 971
    Cited by:  Papers (2)
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    Questions of the coordination of current limiting (CL) fuses and MOV-type lightning arresters are examined. Results are presented from a brief test program done to verify the conclusions reached, based on a review of current standards and typical systems. It is concluded that current selection practices should allow use of arresters in front of CL fuses without undue risk. The probability of damage is very low as long as devices which reflect current standards are used. It is noted that the conclusions reached 20 years ago by the working group on arrester and fuse coordination apply equally well to current MOV-style arresters and the earlier gapped arresters. This is especially true when CL fuses with elements designed to control peak arc voltage are used. Other fuses, such as the 12 A and smaller sizes listed in the standards, which do not control peak arc voltages may cause different results View full abstract»

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  • Effect on de-greasing solvents on conductive separable connector shields and semiconductive cable shields

    Publication Year: 1990 , Page(s): 781 - 786
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A study was conducted to determine the effects of commercial degreasing solvents on the conductivity of an EPDM separable connector shield and two types of cable insulation based in EPR (ethylene-propylene rubber) and XLPE (cross-linked polyethylene), respectively. Solvents tested included a chlorinated solvent based on 1,1,1-trichloroethane and several so-called citrus solvents consisting of natural terpene, limonene, or blends of limonene with other hydrocarbons. All the solvents significantly degraded the conductivity of the EPR and EPDM materials but had little effect on the XLPE cable shield. The solvents differed, however, in the extent of their effects, the rate of recovery of conductivity after removal of the solvent, and the degree to which the original conductivity of the material was restored. The consequences of these results in terms of appropriate field use of these types of solvents by utility personnel are discussed View full abstract»

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  • Probabilistic economic evaluation of substation seismic upgrade

    Publication Year: 1990 , Page(s): 930 - 935
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    The authors present a methodology for deciding whether or not to implement seismic design modifications at Southern California Edison's (SCEs) substation facilities. The method considers the potential for substation capability loss resulting from earthquake damage, cost of seismic modification made today, the cost of damage restoration after that modification is made, the cost of doing nothing now, and the site-specific earthquake probability. On the basis of these findings, recommendations for seismic modifications of substation facilities could be made. A `crossover year' is developed which shows a net savings period and net cost period depending upon whether the seismic event takes place prior to or after the crossover year View full abstract»

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  • Field performance of a digital transient surge recorder

    Publication Year: 1990 , Page(s): 899 - 904
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Characterizing the waveshape of voltage and current transients on distribution systems caused by lightning events has been of considerable interest. A solid-state recording device for this purpose was developed in 1984 with high-sample-rate capabilities and the ability to operate for extended periods unattended. One-hundred of these recorders were fabricated and installed on electric utility distribution systems beginning in 1985. Triggered lightning tests were performed in 1987 and 1988 to further characterize the performance of the recorder and transducers. The design and operation of the recorders are discussed. The recorder has proven accurate, reliable, and effective in capturing high-frequency phenomena on utility distribution networks View full abstract»

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  • Touch voltages on underground distribution systems during fault conditions

    Publication Year: 1990 , Page(s): 1026 - 1033
    Cited by:  Papers (1)
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    Underground distribution lines are usually installed in duct banks with manholes placed at regular intervals for easy installation of the line hardware and ready access for maintenance purposes. During work in these manholes, tough voltages may occur on the line under repair as a result of a fault on another line. Tests were performed on a 25 kV grounded-wye system to measure the level of such voltage and to validate a computer model. The maximum touch voltage measured was 220 V. Over 6000 system configurations were examined in a computer study which showed that the touch voltage appearing at the work site can reach as much as 1500 V in some cases, although operating experience shows that the probability of such high voltages is very slight View full abstract»

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  • The effect of switching surges on 34.5 kV system design and equipment

    Publication Year: 1990 , Page(s): 1106 - 1112
    Cited by:  Papers (7)
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    High failure rates of equipment resulting in severe operational problems caused the Colorado Springs Dept. of Utilities to investigate switching surge phenomena on their 34.5 kV distribution system. Digital simulations were performed to quantify the magnitude of overvoltages created by such operations as cable switching, capacitor bank switching, and switch restrike in an effort to identify the causes of padmount switchgear failures on the underground portions of the system. Results of the study indicated that certain system design changes could be made which would greatly alleviate the severity of the switching surge environment found on the system. The application of arresters was investigated in an effort to further reduce the impact of these transients. Results of field tests and digital simulations confirmed the need for increased BIL levels in switchgear being purchased for this system voltage View full abstract»

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  • Applications software for modeling distribution automation operations on the Athens Utilities Board

    Publication Year: 1990 , Page(s): 1019 - 1025
    Cited by:  Papers (2)
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    The authors discuss the development of applications software called the System Reconfiguration Analysis Program (SYSRAP) for modeling distribution automation operations on the Athens Utilities Board (AUB). The first phase of development involved the testing of algorithms that combine a radial power flow analysis, short-circuit analysis, and database structuring of input and calculated values in a database management program. In the second phase, the algorithms were written in a Pascal program and feeder data were dynamically allocated to system memory to speed computation and access times. During the last phase of development, the program was linked with the real-time data monitored by the distribution automation system at AUB so that SYSRAP could model the real-time behavior of the distribution system as closely as possible. The authors discuss the database techniques that SYSRAP uses to speed up database access and computation time and the data requirements for modeling the real-time operation of an electric distribution system View full abstract»

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  • Flashover vulnerability of transmission and distribution lines to high-altitude electromagnetic pulse (HEMP)

    Publication Year: 1990 , Page(s): 1164 - 1169
    Cited by:  Papers (2)
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    The vulnerability of transmission and distribution lines to flashover from the electromagnetic pulse generated by a nuclear detonation 400 km above the Earth is estimated. The analysis consists of determining the cumulative probability of induced voltage on three-phase lines, including shield and neutral conductors, for four operating voltages and then comparing these stresses to estimates of line insulation strength. The 12 kV line is shown to be vulnerable to HEMP-induced flashover. The 69 kV line is marginally vulnerable to HEMP-induced flashover, but only the minimum-insulation designs in current use are susceptible, and the probability of flashover for those designs is minimal. The 500 and 230 kV lines are invulnerable to HEMP-induced flashover for all HEMP field levels considered View full abstract»

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  • Streaming electrification study of transformer insulation system using a paper tube model

    Publication Year: 1990 , Page(s): 972 - 983
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    A simple flow model was designed to simulate oil flow in the insulation ducts of power transformers. It consisted of an annular paper tube, relaxation tanks, pump, and flow controls. Laminar and turbulent flow modes were studied in the temperature range from 27 to 70°C. Current development was monitored as a function of temperature and flow velocity. The temperature dependence was approximately of the Arrhenius type; no current peak was observed as reported for transformers in the temperature range studied. The current increased linearly with flow velocity at low flow rates and increased as the square of velocity at high flow rates with a gradual transition in the intermediate range of flow. The voltage development was characterized by a sharp rise initially as the flow was turned on, leveling off to a maximum after several minutes. Partial discharge patterns were observed in the volt-time plot, increasing in frequency and temperature at elevated temperatures and flow velocities. A strict application of the test results to transformers is not possible due to unknown parameters View full abstract»

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  • Real-time thermal model for an oil-immersed, forced-air cooled transformer

    Publication Year: 1990 , Page(s): 991 - 999
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (828 KB)  

    A thermal model for predicting the real-time temperatures of an oil-immersed, forced-air cooled transformer is presented. The model consists of a set of three differential equations that are formulated into a computer program. Equations that can be solved for the average real-time temperatures of the core and coil assembly, oil, and tank are developed. Expressions for the convection heat transfer coefficients at all internal oil-solid interfaces, equations for calculation of the incident solar radiation, and correlations for the convective cooling rate from the external tank and cooling tubes are discussed in detail. The thermal model can predict the real-time transformer temperatures for any variation in electrical loading and for any type of ambient thermal environment. Since this model is more detailed than the ANSI/NEMA equations, the results can be expected to predict the transformer temperatures more accurately. The model yielded conservative estimates of the component temperatures when compared with temperatures measured on a distribution transformer. While this test does not verify the accuracy of the model for all types of transformers under all types of loading conditions, it does give initial credibility to the accuracy of the equations and their applicability to transformer heating View full abstract»

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  • Transient overvoltages on a three terminal DC transmission system due to monopolar ground faults

    Publication Year: 1990 , Page(s): 1047 - 1053
    Cited by:  Papers (1)
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    Transient overvoltages were investigated using the Electromagnetic Transients Program (EMTP) for a three-terminal DC transmission system. Pole-to-ground faults on a DC line were studied to investigate overvoltages on the healthy pole and also on the electrode lines. The effect of providing a metallic neutral conductor in one section of the three-terminal system was also studied, as was the sensitivity of the results to DC filter configuration and to neutral bus capacitance. It was found that the peak overvoltages for the DC line, especially near the converter stations, are sensitive to the DC filter configuration. The overvoltages near the converter stations were also found to be affected by the neutral bus capacitance View full abstract»

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  • Adaptive ground fault protection schemes for turbogenerator based on third harmonic voltages

    Publication Year: 1990 , Page(s): 595 - 603
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    Equivalent circuits based on the actual connection of coil-groups of generators are used to study the characteristics of various generator stator ground fault protection schemes presented in the literature. The evaluation and the comparison of the characteristics of those schemes are given by means of protection coverage-critical resistance curves. Although these schemes are successful in practice, they suffer the disadvantage of low sensitivity, which is strongly related to generator operating conditions. To overcome this disadvantage, two adaptive stator ground fault protection schemes based on digital techniques are developed. Compared to conventional third-harmonic voltage schemes, they can automatically track the change of generator operating conditions before a ground fault occurs. Test results from a digital simulation show that they can keep high sensitivity during all operating conditions View full abstract»

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  • Determining temporary overvoltage levels for application of metal oxide surge arresters on multigrounded distribution systems

    Publication Year: 1990 , Page(s): 936 - 946
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1012 KB)  

    Different analytical methods that may be used to calculate values of temporary overvoltage on multigrounded distribution systems as a result of single line-to-ground faults are evaluated in terms of their general accuracy; their ability to account for changes of earth resistivity, ground electrode resistances, and grounding frequency; and the overall impact of such changes on the calculated overvoltage level. Recommendations are provided for the use of these methods under different sets of system conditions. It has been concluded that the commonly used method based on symmetrical components is inadequate for anything but the simplest calculation for a system with near-ideal grounding parameters. For systems where poor grounding conditions are known to prevail, the best method of analysis is to neglect the ground effects altogether. The best overall results are provided by a sophisticated, matrix-algebra-based method which analyzes the ladder network cells of the multigrounded distribution neutral individually View full abstract»

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  • New developments in the field of high voltage and extra-high voltage cables: point of view of a manufacturer

    Publication Year: 1990 , Page(s): 854 - 858
    Cited by:  Papers (1)
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    The author reviews developments in France concerning high-voltage (HV) and extra-high-voltage (EHV) power cables with synthetic insulation and their accessories up to the 500 kV range. A maximum operating field strength approaching 16 kV/mm (405 V/mil) has been adopted for low-density polyethylene (LDPE) insulated cables. The ongoing studies should make it possible to bring the maximum operating field strength for cross-linked polyethylene (XLPE) insulation from 7 to 10 kV/mm (180 to 255 V/mil) and allow cables to be manufactured more economically with this material View full abstract»

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  • Puncture breakdown characteristics of protected rubber insulating gloves

    Publication Year: 1990 , Page(s): 538 - 547
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The results of puncture breakdown tests on rubber gloves are presented. A positive polarity switching surge voltage (275/2500 μs) or a 60 H alternating voltage was applied to the glove to cause breakdown. The effect of mechanical pressure on glove breakdown behavior and the influence of using a leather protector were investigated. It was found that protected gloves are more likely to break down at a position other than where the needle electrode has been placed. In both AC and switching surge breakdown tests, the standard deviation in breakdown voltage for protected samples was greater than that of the nonprotected samples by 25%. Under AC conditions, with mechanical stress applied, a bare glove will break down at a voltage which is approximately 22% below the nonstressed condition. A protected glove which is mechanically stressed will break down at a value 12.75% below the nonstressed condition. It is suggested that the results obtained will help to determine the operating limits and reliability of the glove insulation View full abstract»

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  • A neural network approach to the detection of incipient faults on power distribution feeders

    Publication Year: 1990 , Page(s): 905 - 914
    Cited by:  Papers (97)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    A neural network strategy for the detection of high-impedance faults on electric power distribution feeders is described. This approach consists of collecting samples of substation current during normal and abnormal feeder operation and using these samples to teach a neural network the rules for fault detection. The learning capability utilized in a neural network approach makes it possible to adapt partially trained fault detectors to individual feeders. The data preprocessing required to set up the training cases and the implementation of the neural network itself are described in detail. the potential of the neural network approach is demonstrated by applying the detection scheme to high-impedance faults simulated on a model distribution system View full abstract»

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  • Comparative evaluation by laboratory aging of 15 and 35 kV extruded dielectric cables

    Publication Year: 1990 , Page(s): 816 - 824
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    It is pointed out that utility engineers encounter a significant problem in discerning the accuracy of claims of superior cable quality and in identifying cables which will provide reliable performance over their anticipated life. The authors, in two independent investigations of 15 and 35 kV cables, have compared the performance of a number of cables made with different compounds by different manufacturers. It is shown that judging cables by their unaged voltage breakdown characteristics alone can be very misleading; that, in the long run, dry-cured cables aged in moist environments rapidly lose their original dielectric strength advantage; that certain ethylene-propylene rubber formulations degrade as fast as cross-linked polyethylene; that the best overall results during aging are obtained with tree-resistant polyethylene insulated cables; and that from a voltage-breakdown point of view water-tree length is more influential than the number of water trees View full abstract»

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  • Application of compact static VAR compensators to distribution systems

    Publication Year: 1990 , Page(s): 1113 - 1120
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    The application of SVCs (static volt-ampere reactive compensators) to distribution systems to solve voltage fluctuation problems is discussed. Fast and repetitive voltage fluctuations can exist on an electric utility's distribution system. These voltage fluctuations, which are usually caused by motor-starting or other pulsating or irregular loads such as welders, can be objectionable and can pose problems to the utility. Conventional equipment such as voltage regulators or breaker-switched capacitors are not effective in controlling fast and repetitive voltage fluctuations. Static volt-ampere reactive compensators provide an excellent solution to control voltage fluctuation problems. It is more common to apply SVCs to transmission systems and very large industrial loads because of size and cost constraints. A class of compact SVCs which offers ratings as low as 1 Mvar capacitive and small physical size is described. With the advent of compact SVCs, distribution engineers have another viable option available to solve many of the voltage fluctuation problems in their systems. Information and field experience concerning the compact SVC installed on the Kansas Gas and Electric distribution system are provided View full abstract»

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Aims & Scope

Installation and operation of apparatus, equipment, structures, materials and systems for the safe, reliable and economic generation, transmission, distribution, conversion, measurement and control of electric energy.

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Meet Our Editors

Editor-in-Chief
Wilsun Xu
Ph.D., P.Eng.
Dept. Electrical and Computer Eng.
University of Alberta
(9107 - 116 Street)
Edmonton, Alberta T6G 2V4 Canada
wxu@ualberta.ca
Phone:780-492-5965
Fax:780-492-1811