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Power Delivery, IEEE Transactions on

Issue 2 • Date April 1989

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Displaying Results 1 - 25 of 78
  • Computer aided design of synthetic test circuits for high voltage circuit-breakers

    Page(s): 1049 - 1055
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    The authors describe experience acquired in designing test circuits for high-voltage circuits breakers. Circuit synthesis is achieved numerically, using an iterative method which involves the Laplace transform. Different test circuits are considered that are needed to obtain responses specified by ANSI and IEC standards. The specific interactive software has been created to permit automatic synthesis and optimum construction of these circuits is briefly described.<> View full abstract»

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  • Discussion, with reply, of "Test results of personal protective grounding on distribution line wood pole construction" by J.T. Bonner, B. Erga, W.W. Gibbs, and V.M. Gregorius

    Page(s): 1127 - 1128
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    Several comments and criticisms are made concerning the above-named work (ibid., vol.4, no.1, Jan. 1989). In particular, the original authors' claim that the personal protective grounds (single-point ground) method is superior to the working ground and bracket ground methods used for worker protection was questioned.<> View full abstract»

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  • Harmonic domain analysis of field variables related to eddy current and hysteresis losses in saturated laminations

    Page(s): 1111 - 1116
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    The authors give a detailed analysis of the space and time distribution of the field variables B, H, and E inside saturating laminations, using a harmonic domain modeling method. A simple way has been devised for the representation of hysteresis. It was found that hysteresis affects to a small degree the variation of H and B but has no noticeable influence on E and thus, as expected, does not interact with the corresponding eddy current losses. It is shown that saturation distorts the linear space distribution of the eddy currents but that the assumption of linear distribution still leads to a very simple method for eddy current loss calculation which is remarkably accurate at 60 Hz View full abstract»

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  • Line parameters and transients of a non-parallel conductors systems

    Page(s): 1117 - 1126
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    The authors derive impedance and admittance formulas for a system of nonparallel conductors together with an approximate method of evaluating impedance and admittance using an existing parallel-conductor formula. Transients on the nonparallel-conductor system are calculated using the impedance and admittance. It is found that the conventional analysis method for investigating electrostatic and magnetic induction in the steady state cannot be applied to transient analysis. To analyze a transient, the nonparallel conductors need to be divided into a plural number along the line to take into account the oblique effect which causes an increase of the sending end-voltage until a reflection comes back from the remote end. It is shown that the transient induced voltage and current are much greater than those in the steady state View full abstract»

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  • The application of real-time monitoring and rating to HPOF pipe cable systems

    Page(s): 850 - 856
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    The Boston Edison Company has installed real-time monitoring and rating equipment on two independent pairs of 115 kV HPOF (high-pressure oil-filled) pipe-type cables. The real-time systems are remotely located at cable terminal locations so that critical data inputs can be hard-wired to the computing processor. Real-time information is made available via analog SCADA (supervisory control and data acquisition) connections and also by IBM PCs equipped with modems, which can call the remote systems to view real-time conditions or unload historical data. A PC software package complements the real-time system and gives planners, system operators, and cable engineers the ability to simulate cable system operation in an offline environment. In general, the identification of effective earth parameters in real-time is shown to result in increased emergency and normal ratings by replacing the conservative assumptions that must be made at the design stage with accurate real-time data. Lightly loaded circuits have exhibited large increases in short-time emergency ratings, as they normally operate at relatively low temperatures View full abstract»

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  • Network reconfiguration in distribution systems for loss reduction and load balancing

    Page(s): 1401 - 1407
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    A general formulation of the feeder reconfiguration problem for loss reduction and load balancing is given, and a novel solution method is presented. The solution uses a search over different radial configurations created by considering switchings of the branch exchange type. To guide the search, two different power flow approximation methods with varying degrees of accuracy have been developed and tested. The methods are used to calculate the new power flow in the system after a branch exchange and they make use of the power flow equations developed for radial distribution systems. Both accuracy analysis and the test results show that estimation methods can be used in searches to reconfigure a given system even if the system is not well compensated and reconfiguring involves load transfer between different substations. For load balancing, a load balance index is defined and it is shown that the search and power flow estimation methods developed for power loss reduction can also be used for load balancing since the two problems are similar View full abstract»

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  • Maximum power transfer limited by voltage stability in series and shunt compensated schemes for AC transmission systems

    Page(s): 1246 - 1252
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    A method of determining the maximum power transfer limit of AC transmission systems from the point of view of voltage stability is described. Five different schemes using series and shunt compensation are studied, and numerical results for maximum power transfer, critical angular separation, and critical voltage are given. Effects of load power factor, line loss, line length, and the degree of series and shunt compensation are considered. Among other findings it is shown that the maximum power transfer increases as the degree of series compensation is increased. The maximum power transfer limit decreases with increases in the value of line-loss factor and line length. The critical angular separation and the critical load-end voltage decrease as the load power factor is changed from leading to lagging View full abstract»

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  • Post-arc current in high voltage SF6 circuit-breakers when breaking at up to 63 kA

    Page(s): 1056 - 1062
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    Post-arc current measurements were made on a high-voltage SF6 circuit breaker. A pyrotechnic device was used to protect the measurement shunt. The tests, performed at high current values between 40 and 63 kA, gave post-arc current levels of 0.5 to 2 A. Interpretation of the experimental results by the generalized Mayr model led to the determination of a set of parameters characteristic of the apparatus tested, thereby making it possible to find the test results and, in particular, to forecast cases of thermal failure View full abstract»

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  • Performance evaluation of 15 kV polymeric insulators for dead-end type applications on distribution systems

    Page(s): 1223 - 1231
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    Results are reported of a research program to investigate the performance of polymeric insulators for 15 kV dead-end applications on distribution systems. The test program involved both new insulators from five different manufacturers and naturally aged insulators removed from service on the distribution system of Pennsylvania Power & Light. The test series to evaluate the new insulators included preconditioning treatments, salt fog and tracking wheel accelerated aging tests, electrical tests, and material and physical tests. The tests for the naturally aged insulators were mainly limited to the electrical tests and the material and physical tests. It is found that some of the polymeric insulators installed on the distribution system have limited remaining service life. The performance of the naturally aged insulators in the test program indicates that the electrical characteristics of the early production insulator has degraded from published data. These results substantiate concerns about insulator performance based on external appearance. The new insulators show marked improvement over the first generation of insulators provided sufficient filters are added to alleviate erosion and tracking problems. Based on the preconditioning and accelerated aging test results, a 30-year field life does not appear unreasonable View full abstract»

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  • A practical mathematical model of corona for calculation of transients on transmission lines

    Page(s): 1145 - 1152
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    A practical mathematical model of the corona effect on overhead power line transients is developed based on the concept of time delay in corona formation. Results computed by this model agree well with experimental q-v (charge-voltage) characteristics for both fast and slow impulse voltages under both polarities. It is shown that the introduction of the time-delay concept leads to better results and a better understanding of many important characteristics of q -v curves, especially for fast transient voltages. The model is applicable to transmission lines with either known or unknown q-V characteristics because all the model parameters can be determined beforehand according to the conditions of the line View full abstract»

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  • Computer models for complex plant based on terminal measurements

    Page(s): 1393 - 1400
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    A method for obtaining models of a complex plant and systems for use in transient voltage studies is described. The method is based on determining the terminal impedance/frequency characteristics of the plant or system under study over a wide frequency range. This characteristic is obtained from measurements performed at sampled frequencies with a programmable impedance meter and a microcomputer. The use of the method for performing a high-speed switching transient calculation for a cable/motor system is illustrated and the results are compared with experimental records View full abstract»

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  • Comparison between measurement and calculation of line switching with inductive and complex source-modelling requirements

    Page(s): 1432 - 1440
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    Different models for calculating overvoltages occurring during the energizing of unloaded lines are examined. The models are discussed in relation to both a network with an inductive source and a network with a complex source. Calculations are carried out with the Electro Magnetic Transients Program (EMTP). The calculation results obtained with these models are compared with measurements. Finally, modeling requirements and directives necessary for obtaining reliable results are presented View full abstract»

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  • Telephone interference criteria for HVDC transmission lines

    Page(s): 1408 - 1421
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    The coupling between a transmission line and telephone cables is calculated on a general basis. Based on field measurements of the current harmonic spectrum from a modern 12-pulse HVDC (high-voltage direct current) converter, the ratio between disturbance current and resulting noise level in a telephone system is established. Disturbance current limitation criteria are identified based on tolerable noise level and assumptions regarding typical worst-case coupling conditions in a suburban area between a transmission line and a telephone system. It is concluded that disturbance current criteria as currently specified for some HVDC lines are substantially more stringent than corresponding criteria for both distribution lines and HVAC (high-voltage alternating current) lines View full abstract»

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  • Effects of voltage impulses on extruded dielectric cable life

    Page(s): 829 - 841
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    Laboratory tests were performed to investigate the effects of lightning and thumping impulses on the performance of various 15 kV cable designs. The cable designs were aged in the laboratory using an accelerated water treeing test. Some samples were subjected to lightning impulses, some were subjected to thumping impulses, and some were aged without impulses applied. The impulse effects were evaluated using time to failure data, AC breakdown data, and impulse breakdown data. The results show that lightning or thumping impulses do not affect cable AC or impulse breakdown strength. There is also no visual difference between wafers taken from impulsed and control samples. However, there is a strong indication that lightning impulses can reduce cable life. Almost all the aging failures occurred while the cables were warm. No failures occurred during the impulse application. It is also shown that increased cable wall thickness extends cable life for the tree-resistant high-molecular-weight insulation material tested, but not for the crosslinked polyethylene insulation material tested View full abstract»

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  • Addendum I to bibliography of gas-insulated substations

    Page(s): 1003 - 1020
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    A 343 item addendum is provided to the bibliography that was published in 1982 (see ibid., vol.PAS-101, no.11, (1982)). It is divided into three main sections, dielectric characteristics, substation equipment, and general points. A list of authors is also included View full abstract»

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  • Instrumentation system used to determine the effects of steep front short duration impulses on electric power system insulation

    Page(s): 938 - 941
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    The author describes instrumentation which is capable of recording steep-front short-duration or EMP (electromagnetic pulse) transients. The instrumentation includes a digitizer that samples the voltage (digitizes) at 742 ps per sample and has a 10 K work (sample) memory depth. A second digitizer is capable of nanoseconds per sample, and 32 K words of memory. The instrumentation system used in a specific project is described. It proved to be efficient and reliable in recording and storing data and providing hard copy for this steep-front impulse investigation. There were no major failures of instrumentation equipment or software. The instrumentation arrangement, shielding and performance experiences described are applicable to high-voltage high-frequency transients View full abstract»

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  • Partial discharge measurement on three-core belted power cables

    Page(s): 927 - 931
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    It is shown that the partial discharge (PD) characteristics of three-core belted-type cables determined using single-phase testing techniques may differ greatly from the actual discharge performance of the cable when subjected to three-phase voltage conditions in service. To achieve meaningful results concerning the voltage ratio and the life expectancy of the cable, careful considerations must be given to the way of energizing the cable and PD response characteristics of single-phase test configurations. An example of erroneous single-phase testing techniques is a circuit which gave an error of up to 88% lower discharge level as compared with three-phase detection. A novel technique was developed in which single-phase voltage was applied to one core, the other two cores were earthed, and the sheath was left floating. The PD detection used a coupling capacitor connected to the energized phase View full abstract»

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  • Development of water pipe cooling system for power cables in tunnels

    Page(s): 863 - 872
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    A full-size test line was constructed to study the water pipe cooling system for a bulk-power transmission line installed in a tunnel. Based on the test data and their analysis, a technique for designing the system has been established. The results have indicated an effective layout of the cooling pipes in the tunnel, and have validated the accuracy of the computer models to determine thermal characteristics of the tunnel system. An efficient control method to operate the cooling system according to the load changes of the cables was developed. The chosen layout is shown to be more effective than the dispersed layout because it accelerates the air convection and makes the air temperature more uniform. Furthermore, the thermal convection resistance between the tunnel wall and the air is reduced. It was also verified that the air temperature distribution along the vertical shaft could be predicted by thermal convection analysis. This cooling system is scheduled to be applied to a 154 kV power cable line in 1990 View full abstract»

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  • A hybrid expert system for faulted section identification, fault type classification and selection of fault location algorithms

    Page(s): 978 - 985
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    The authors present an expert system developed in Turbo PROLOG to identify faulted sections and interpret protective apparatus operation in large interconnected power systems. This expert system is capable of identifying bus faults, line fault sections, and fault sections in the common area of a specific bus and line. Also, the expert system identifies relays or breaker malfunctions. The expert system is expanded to include real-time measurements of current and voltage phasors to classify the type of fault that the faulted section has experienced. When the faulted section is a transmission line, the expert system then selects an appropriate fault location algorithm to compute the fault location in miles. The importance of using a combination of numeric and database algorithms is emphasized View full abstract»

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  • Studies on modeling corona attenuation of dynamic overvoltages

    Page(s): 1441 - 1449
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    An experimental and theoretical study is presented on the corona characteristics of conductor bundles under dynamic overvoltages. Measurements have been made in the outdoor test cages of Institut de Recherche d'Hydro-Quebec on two bundles, under conditions of fair weather and heavy rain, for steady 60 Hz voltages as well as dynamic overvoltages. Based on the data on corona currents and losses obtained, a nonlinear resistance model of corona is proposed for attenuation studies. The Suliciu model for corona, originally developed for unipolar impulses, has been adapted for dynamic overvoltages. Both these corona models are used to study the influence of corona on the dynamic overvoltages developed during line energization and load shedding of a single-phase line. Among other findings, it is shown that the corona phenomenon stabilizes after the first half-cycle of the dynamic overvoltage. The corona losses of conductor bundles under fair weather conditions increase rapidly with the conductor surface voltage gradient; they approach losses under heavy rain at higher gradients View full abstract»

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  • Transient analysis of heat dissipation due to a HVDC ground electrode

    Page(s): 916 - 920
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    The temperature of the soil surrounding a high-voltage direct-current (HVDC) ground electrode was computed at various points in time using finite difference methods. The temperature response for various ground electrodes was computed using these same techniques. The results were then compared with results obtained experimentally in a laboratory. It is suggested that peak temperature calculations may be desirable for periodic short-term operation of a HVDC ground electrode. Since the surrounding soil temperatures may not have reached a steady state, a transient analysis may be necessary View full abstract»

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  • Adaptation of the control equipment to permit 3-terminal operation of the HVDC link between Sardinia, Corsica and mainland Italy

    Page(s): 1269 - 1274
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    After more than 20 years of service as a conventional two-terminal HVDC link, the Sardinia-mainland Italy HVDC link (200 MW, 200 kV) is now operating as a three-terminal system. The original control equipment has been modified to allow the introduction of a tapping station on the line for three-terminal operation. The adaptations to the control equipment, including means to ensure that the converters are operated within their capabilities, are explained. It is concluded that the successful addition of a tapping station to the existing Sardinia-mainland Italy HVDC link demonstrates the ease with which an HVDC link with frequency control can be adapted to provide for a third terminal, even though it utilizes a different generation of technology. It also demonstrates the practicality of allowing two separate converter stations (Sardinia and Corsica) to modulate their power flow according to the demands of local frequency, within the limitations imposed by plant ratings and system load dispatching View full abstract»

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  • A comparison of HVAC and HVDC contamination performance of station post insulators

    Page(s): 1486 - 1491
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    Results of HVAC and HVDC (high-voltage alternating current and direct current) artificial contamination tests on station post insulators are reported. The tests were conducted using the clean fog method at various severity levels. The contamination behavior of station post insulators with semiconductive glaze was also evaluated and compared with the performance of post insulators with conventional glaze. For the latter type of insulator, different shed shapes were tested to study the effects of geometry on performance. The findings included the following: the critical flashover voltage (CFO) of the posts with conventional glaze, for a given minimum shed spacing, tends to increase as the specific leakage distance increases for both HVDC and HVAC tests. The ratio of the AC CFO (RMS) to the DC CFO also linearly increases as the specific leakage distance increases. The CFO per unit leakage distance decreases more rapidly with specific leakage distance for HVDC than for HVAC. Semiconductive glaze post insulators offer significantly improved contamination performance for both HVDC and HVAC View full abstract»

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  • Polymeric cable terminators under accelerated aging in a fog chamber

    Page(s): 842 - 849
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    The authors present the results of fog chamber tests performed to compare the contamination performance of 25 kV class outdoor polymeric cable terminators. The experiments were conducted in high-conductivity (⩾1200 μs/cm) fog. The effects of weathershed material and design, method of stress relief, and experimental conditions on the contamination performance are discussed. It is shown that the weathershed material and design have a greater influence on the contamination performance than the method of stress relief. The results indicate that the method of stress relief does not improve contamination performance under normal operating stress. For terminators using good track-resistant materials, satisfactory performance can be obtained even with a 50% reduction in the leakage distance provided View full abstract»

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  • Study on reduction in electric field, charged voltage, ion current and ion density under HVDC transmission lines by parallel shield wires

    Page(s): 1351 - 1359
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    Several models of shield wire were tested with the Shiobara HVDC (high-voltage direct current) test line. The models contain typical standard wires that are generally used to reduce field effects at ground level, neutral conductors placed at lower parts of the DC line, and an earth corona model to intentionally cancel positive or negative ions by generating ions having opposite polarity to ions flowing into the wire. The authors describe experimental results on the effects of these shield wires and a method to predict shielding effects. It is concluded that shielding using the earth corona is quite an effective method; it is even applicable to the reduction of ion density, which has normally been considered difficult 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