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Reverberation chambers are attractive electromagnetic compatibility test facilities, both economically and technically. Careful design and analysis of these facilities are important, if the results obtained are to be treated with a high level of confidence. Numerical modeling is an important part of the process of reverberation chamber design and analysis. Hence, it is important that the modeling techniques to be used are appropriately validated. Much of the published work to date takes either a statistical or a deterministic view of validation. This paper provides validation evidence for a low-resolution transmission line matrix (TLM) model of a reverberation chamber in a manner approximating the way in which the chamber is used, i.e., validating based on the effects of a simple device under test. A variety of statistical and heuristic approaches have been used to quantify the level of agreement, intending to set the likely lower bound for the quality of comparisons between simulations and measurements. While not drawing any 'universal' conclusions about the veracity of the TLM technique, the paper concludes that a relatively simple model of a reverberation chamber provides a useful analysis of the chamber with close comparisons between modeled and measured data. Index Terms--Mode-stirred chamber, reverberation chamber, test facilities, transmission line matrix (TLM), validation.

This paper presents a new method for computing internal voltages and currents along transmission lines. The approach is an extension to the existing method of characteristics (MoC)-based line models and computes the voltage at internal points as a superposition of forward and backward waves. These waves are obtained by convolution between the reflected wave and the propagation function from the line end to the considered position. This voltage profile component (VPC) permits computing the voltage at arbitrary points along the line while avoiding the error accumulation that can result when cascading line models. The VPC can be utilized with any MoC-based approach and has been used in this paper together with the universal line model in order to obtain a model of very high accuracy. The VPC approach is demonstrated to give more accurate results than a cascade of regular line models in the case of fast front transients. Index Terms--Electromagnetic transients, insulation coordination, simulation, transmission line.

Various transmission line fault location algorithms have been proposed in the past depending on the measurements available. These algorithms perform well when the measurements utilized are accurate; they may yield erroneous results when the measurements contain considerable errors. In some cases, there are redundant measurements available for fault location purposes, and it may be possible to design an optimal estimator for the fault location based on nonlinear estimation theories. This paper aims at proposing a possible method for deriving an optimal estimate of the fault location that is capable of detecting and identifying the bad measurement data, minimizing the impacts of the measurement errors and thus significantly improving the fault location accuracy. The solution is based on the distributed parameter line model and thus fully considers the effects of shut capacitances of the line. Since field data are not available, case studies based on simulated data are presented for demonstrating the effectiveness of the new method. Index Terms--Bad measurement detection and identification, distributed parameter line model, fault location, nonlinear estimation theory, optimal estimator.

This paper addresses the analysis of field data gathered at the Mont B61air icing test site in Quebec. Load cell evaluations of actual icing loads on an existing 315-kV line are correlated to hourly measurements of ambient temperature, wind speed, precipitation rate, and number of signals of the Ice Rate Meter (IRM), in order to establish a numerical model for precipitation icing accretion on overhead line conductors. The correlation analysis is limited to precipitation ice events, or those mixed with relatively short periods of in-cloud icing. Emission of IRM signals is used as a criterion to distinguish the accumulation phase of an ice event, from persistence and shedding, characterized by no emission of IRM signals. The results from the analysis show that the icing rate corresponding to wet growth is much larger than that in dry conditions. What is more surprising, it was also found that the icing rate during periods when winds blow parallel to the line axis is significantly greater than that with perpendicular winds. The linear fit to the set of multivariate data is usually applicable. However, in some relatively rare cases of wet growth in heavy precipitations without IRM signals, the linear model may be inadequate and quadratic polynomials must be used. The results from the application of the numerical model are in excellent agreement with the field observations. This empirical model can be very useful for evaluation of icing loads on energized transmission lines, when there are not available measurements by load cells or other direct methods. Index Terms--Overhead transmission lines, precipitation icing, statistical analysis.

The increase in electric stress due to a surface protrusion at the interface between a semiconductive shield and a polymer insulation layer in power cables can lead to localized electron injection into the polymer insulation and result in undesired material degradation. This paper reports the analyses of electric stress enhancement of surface protrusions in several commonly encountered medium- and high-voltage power cable configurations. First, a brief review of the electric stress enhancement theories is presented. Then evaluations using these theories for various power cable configurations are made, and it is shown that theories considering a hyperboloida| protrusion will exhibit more realistic stress enhancement results than the cases based on a spheroidal protrusion. Further examination reveals that, besides the sharpness of a protrusion, thickness of the insulation medium also plays a governing role in the stress enhancement at the interfaces between different dielectric media. Contrary to the conventional wisdom, it is a surprise to observe that a thicker insulation can actually cause higher stress enhancement at a protrusion tip, under a given applied voltage. Because of this, a flatter surface protrusion at a higher voltage setting, which usually has thicker insulation, can result in earlier degradation than a sharper protrusion at a lower voltage, even though sharper extrusions are expected to have higher stress enhancement. As a result, thicker insulation may not always be advantageous in the power cable design for higher voltage applications. Index Terms--Electric stress enhancement, hyperboloidal protrusion, spheroidal protrusion, power cable design, polymer insulation, semiconductive shield, interface protrusions, electric degradation of polymers, treeing.

The quite good foundation for maglev option selection for Beijing-shanghai line based on the successful construction and operation of the Shanghai demonstration line and the very important significance of selection of the maglev option for Beijing-Shanghai line are presented.

Abstract--Test structures intended for performance verification of transmission line pulse (TLP) systems have been designed and tested. They consist of simple resistors in either copper or silicide clad polysilicon. The copper structures proved unsuitable due to excess heating and melting of any reasonable geometry. The silicide clad polysilicon proved more successful. A simple model of resistive heating accounts for observed nonlinearity in the structures under high current stress. The availability of a verification structure on wafer ensures the proper performance of the full measurement system, including contact to the wafer and the pad structure, ensuring valid TLP measurements. Index Terms--Electrostatic discharge, pulse measurements.

This paper investigates the charge versus voltage (q-v) curves of surge corona on transmission lines. Two measurement methods of the q-v curves are proposed, and field test results are shown to validate the methods. Since the new methods do not require a charge-measuring conductor, such as a corona cage, the q-v curves are measured in the real electric-field distribution. One of the methods obtains the amount of charges q by numerically integrating the digitally stored waveform of injected current, assuming that the line is short in length and open ended. Thus, it is suitable for measurement using an experimental setup. The other calculates q from voltage and current waveforms based on the traveling-wave theory, assuming that the line is long enough to expect no reflected waves, and it is applicable to existing 'real' transmission lines. Measured q-v curves are compared with simulated ones, and their physical properties are discussed in the paper. Index Terms--Charge measurement, corona, power transmission lines, space charge, surges.

Nonuniform line (NL) is the designation of a transmission line segment where the conductors are not parallel or where the sag is significant. In addition, transformers and also parts of metallic towers can be viewed as NLs. In this paper, the propagation characteristics of NLs are examined. They appear as generalizations of concepts from uniform transmission lines (ULs). It was found that an n-conductor NL has n pairs of modes and the forward and backward waves of a mode have the same propagation constants. However, the modeshapes defined by the voltages and currents of a given mode are different. For illustration, the variation with frequency of these propagation characteristics has been presented for the wide-span river crossing of an overhead transmission line. Index Terms--Frequency domain, nonuniform lines, overhead lines, propagation analysis.

In order to clarify the lightning performance of a distribution line, test distribution lines and a test tower were constructed at the Mikuni Testing Center of Hokuriku Electric Power Company in 1999. Using these facilities, we observed transient voltages and current distributions due to direct strokes of natural lightning. Based on this data, we have clarified the following points: 1) Calculated voltages and currents using the EMTP agree with the experimental results fairly well. 2) For lightning currents of long durations, however, the reduction of voltages across arresters by energy absorption should be taken into consideration. Index Terms--Direct stroke, distribution line, EMTP, natural lightning, surge arrester.

Real and reactive power flow in an ac transmission line are independently controlled by connecting, to a transmission line, a series-compensating voltage, which is variable in magnitude and at variable angle with respect to the transmission line voltage as well as the prevailing line current. The traditional technology of transformer and tap changer is used to implement this novel technique. An additional voltage regulation capability can also be implemented. The speed of tap changer operation determines the response time of this power flow controller, which is quite adequate in most utility applications. The response time can be improved if suitable solid-state switches are available to replace the mechanical taps. Index Terms--Converters, FACTS, load flow control, phase shifters, power electronics, power transformers, power transmission, power transmission control, unified power flow controller (UPFC).

This paper proposes a novel adaptive relaying scheme based on phasor-measurement units (PMUs) for transmission lines. The proposed adaptive relaying scheme can provide an extremely accurate discrimination between in-zone and out-of-zone faults. Two novel and composite fault discrimination indices in terms of Clarke components of synchronized voltage and current phasors at two ends of a line are derived. A line parameter estimation algorithm is developed and built in the newly designed relay to solve the uncertainty problem of line parameters. The proposed relaying scheme is independent of fault types, fault locations, fault path resistance, fault inception angles, and the variations of source impedance. The tripping decision time of the designed relay is very fast and almost held well within 6 ms for most fault events. All of the EMTP simulation results show that the proposed adaptive relaying scheme provides a high level of dependability and security. Index Terms--Adaptive relaying, global positioning system (GPS), line relaying, phasor-measurement unit (PMU).

This paper presents a novel approach to fault detection, faulted phase selection, and direction estimation based on artificial neural networks (ANNs). The suggested approach uses the finite impulse response artificial neural network (FIRANN) with the same structure and parameters in each relaying location. Our main objective in this work is to find a fast relay design with a detection time not dependent on fault conditions (i.e., current transformer saturation, dynamic arcing faults, short-circuit level, and system topology) and that uses only unfiltered voltage and current samples at 2 kHz. The suggested relay, which we have named FIRANN-DSDST, is composed of a FIRANN together with post-processing elements. The FIRANN is trained globally using training patterns from more than one relaying position in order to be as general as possible. The FIRANN is trained using an improved training algorithm, which depends on a new synaptic weights updating method, which we have named the mixed updating technique. The proposed relay is trained using training patterns created by simulating a real 400-kV network from the Spanish transmission network (R.E.E.). Finally, the proposed relay is tested using simulated and real fault data. The results encourage the use of this technology in a protective relaying field. Index Terms--Arcing faults, artificial neural networks, protective relaying, transmission-line protection.

This paper describes a novel fault-detection technique of high-impedance faults (HIFs) in high-voltage transmission lines using the wavelet transform. Recently, the wavelet transform (WT) has been successfully applied in many fields. The technique is based on using the absolute sum value of coefficients in multiresolution signal decomposition (MSD) based on the discrete wavelet transform (DWT). A fault indicator and fault criteria are then used to detect the HIF in the transmission line. In order to discriminate between HIF and nonfault transient phenomena, such as capacitor and line switching and arc furnace loads, the concept of duration time (i.e., the transient time period), is presented. On the basis of extensive investigations, optimal mother wavelets for the detection of HIF are chosen. It is shown that the technique developed is robust to fault type, fault inception angle, fault resistance, and fault location. The paper demonstrates a new concept and methodology in HIF in transmission lines. The performance of the proposed technique is tested under a variety of fault conditions on a typical 154-kV Korean transmission-line system. Index Terms--Fault detection, high-impedance arcing fault, transmission lines, wavelet transform.

Catastrophic equipment failures continue to occur today due to ferroresonance even though this phenomenon has been extensively studied over the past 90 years. This paper is concerned with comparing analytical nonlinear dynamics methods with a two-dimensional (2-D) brute-force bifurcation diagram for displaying safety margins in a 2-D parameter space. A simplified single-phase model is used to represent the case of ferroresonance between a transformer and circuit breaker grading capacitor. Comparisons are made between the analytical method and EMTP simulations of an actual ferroresonant event. Index Terms--Approximation methods, capacitors, ferroresonance, nonlinear circuits, power system modeling, power system transients, power transformers.

High and steep lightning surge voltages sometimes cause electrical punctures of suspension insulators. Microscopic analysis clarifies electrical breakdown mechanism of ceramic material. V-t characteristics of the insulators are closely examined. Chance of the puncture depends on the dimensions of the insulators, steepness of the impulse voltages and the number of impulse occurrences. Empirical equations relating to these parameters has been established based on laboratory test results. Calculation shows no risk of puncture on the quality insulators for the impulse voltages of 2500kV/[[micro]seconds] steepness which is required by the standards.

Underground transmission cables are a vital part of any power transmission system which means that the selection of a particular cable must be based upon many considerations ranging from the cost of losses to environmental concerns. The focus of this paper is on the design, selection, and testing of transmission cables within specific geographic regions. Design considerations on a regional basis includes temperature constraints, voltage and voltage stress limits, capacity and ampacity, backfill requirements, cooling and bonding. The material presented in this paper covers land based transmission cables only. Submarine cables, URD or UD cables are not included.

Two accelerated aging test procedures are proposed for use on solid dielectric extruded distribution cables under wet conditions. One test method is a fixed time duration test in which the degree of cable specimen aging is assessed in terms of breakdown tests, while the other test method is a time to breakdown test in which the cable specimens are voltage stressed until failure ensues.

A new fault location system based on the travelling wave principle and capable of locating faults on power lines to within [+ or -] one tower span (300m) has been successfully developed and applied to B.C. Hydro's extensive 500 kV network. Unlike earlier schemes which are based on impedance measurements, its accuracy is not affected by load conditions, high grounding resistance and most notably series capacitor banks. This system measures the time of arrival of a fault-generated travelling wave at the line terminals using the precise timing signals from the Global Positioning System (GPS). Operating experience with the fault locator on lightning related faults indicated highly accurate results were obtained for the majority of the cases. In a few of the lightning-caused disturbances, the system gave anomalous measurements. This paper describes the operation of the system, summarizes the operating experience and explains the observed anomalous measurements. Keywords - ELECTRIC LINES: Electric Fault Location, MEASUREMENTS: Global Positioning Systems (GPS), LIGHTNING, LIGHTNING PROTECTION, ELECTRIC LINES: Lightning Performance.

This paper introduces a new approach to fault analysis using synchronized sampling. A digital fault recorder with Global Positioning System (GPS) satellite receiver is the source of data for this approach. Fault analysis functions, such as fault detection, classification and location are implemented for a transmission line using synchronized samples from two ends of a line. This technique can be extremely fast, selective and accurate, providing fault analysis performance that can not easily be matched by other known techniques. Keywords: Fault Analysis, Fault Detection, Fault Classification, Fault Location, Synchronized Sampling

This paper describes the dielectric and accelerated aging tests on a 800-kV ac PPLP-insulated low-loss SCFF cable prototype. The test program was developped to validate the PPLP technology for future Hydro-Quebec 765 kV St-Lawrence under-river crossings. The paper reports on the cable and accessories characteristics, the test line construction, the test program, and the main results obtained. The successfully completed program has shown the overall very good performance of the cable and its accessories.

Data are provided from laboratory evaluations performed on ten 15kV and five 35kV ethylene-propylene copolymer rubber (EPR) feeder cables, made by one manufacturer and ranging in service age from 2 to 22 years. The evaluations consisted of visual examination of cable components, including the presence of water trees in the insulation and physical and electrical tests to establish changes which may have occurred in service. The data are used to establish an in-service rate of degradation for cables, up to 13 years in service, made with one type of EPR formulation. Based on an extrapolation of the breakdown voltage test results, it is expected that this type of cable will have a service life in excess of 30 years.

This paper describes the installation, testing, and results of a long term, full scale laboratory evaluation of a 230kV XLPE insulated cable system. System components included two innovative, pre-molded splices, a 128 meter (420 foot) cable run, and two silicone oil filled, porcelain cable terminations. Load cycle aging was performed on the cable system over a four year period. After successfully completing the outdoor aging program, the system was exposed to a final impulse breakdown test. Results demonstrated the importance of considering thermo-mechanical bending in aluminum conductor, XLPE insulated designs. The influence on cable ampacity of solar heating at riser transitions was also demonstrated. Keywords: termination, splice, cable, transmission, solar heating, ampacity, thermo-mechanical bending.

Polarimetric radar backscattering measurements of a variety of powerline cables are presented. The objective of the first part of the investigation was to study the effect of braiding of the cables on the backscattering at skew incidence. The measurements were performed for four different actual size powerline samples at C-, X-, and Ka-band over a wide range of incidence angles. The data were collected over a 500 MHz bandwidth at C- and X- band with a 1.25 MHz increment and a 1 GHz bandwidth at Ka-band with a 2.5 MHz increment. Also the effect of nonuniform illumination and measurement in the near field of the cables were studied. Experimental data shows a significant radar backscatter for VV-polarization (Sigma(sub Nu Nu)) at angles away from normal incidence. This backscatter is proportional to the number and diameter of the strands on the surface of the cables. There is also noticeable backscatter for the HH and VH components of the scattering matrices. Their magnitudes, relative to that of the VV component, are proportional to the pitch angle of the helix. Since detection of these cables is an important safety issue for low-flying airplanes a detection algorithm using polarimetric synthetic aperture radar (SAR) images was developed using the knowledge gleaned from the measurements. The detection algorithm was tested on a simulated image and worked well, detecting a power line whose backscatter power was 6 dB below the average background power.

In the study of wind-induced motion of conductors of overhead power transmission lines, an indoor test span measuring 30 m or more is normally used. The span is generally excited into motion by an electrodynamic-type exciter connected at a span end. This connection increases the stiffness of the span at the point of connection, which will affect the dynamic characteristics of the test span. A more exact simulation of the indoor test-conductor motion is essential. Simulation of test-conductor motion using the principle of electrodynamic forces between parallel, long conductors is proposed. Indoor test-span motion by this method is equivalent to steady crosswinds excitation in the field as distinguished from galloping conductors resulting from a combination of wind direction, velocity, moisture, and temperature. Consequently, the results of vibration experiments also will be more exact. The principle employed in the new excitation system, the methods of excitation in indoor spans using the principle, and the advantages of the new excitation system as compared to the presently employed system are discussed in this paper.

As a part of an EPRI-sponsored development on advanced power modulation control system for HVDC lines, dynamic system monitors (DSM) were installed at the dc terminals of the Square Butte system. The monitors were used to validate the computer models used for the controller design and will be used to validate the performance of the controllers after installation. The paper describes the use of Prony analysis and Fourier techniques to analyze system disturbances and to validate the computer models. As described in the paper, excellent results have been achieved at least for parts of the system for some well defined disturbances.

An open phase conductor detector system is described consisting of one or more transmitters and a receiver which communicate through the distribution line neutral conductor. The transmitter(s) detects the open phase conductor by monitoring the phase conductor voltage using redundant inputs. When an open phase conductor is detected, the transmitter injects a signal to the distribution line neutral conductor by means of a coupling current transformer (CT). The signal is frequency and duration coded. The receiver decodes the signal and generates a trip signal which may activate a breaker, a ground switch, or a recloser causing isolation of the distribution line with the open (downed) phase conductor. The system is presently implemented for single distribution lines, A prototype open conductor detector system has been constructed and field tested on a Georgia Power Company distribution system.

The paper reports on field tests conducted by American Electric Power (AEP) on a 12.47 kV distribution line. The results cover capacitor switching and load dropping tests. The highest overvoltage recorded of 2.43 p.u. was during capacitor switching with arresters disconnected. At the line end, a maximum of 2.16 p.u. was measured during the line reenergization with the capacitor bank disconnected. The results give both overvoltage and overcurrent transient waveshape, magnitude and dominant frequency. Spectrum analysis of selected test shots provided the information on the extent of transient nonlinearity. Also, information is given on the field test instrumentation setup.

Conventional fault location methods using one-terminal ac voltage and current are not applicable to multi-terminal systems. This paper describes a new fault location algorithm for multi-terminal two Parallel transmission lines. This method uses the magnitude of the differential currents at each terminal and also uses an algorithm based on a 3-terminal fault location algorithm and an equivalent conversion from an n-terminal to a 3-terminal system. For a multi-fault occurring at the same place and same time on both lines as well as a single-fault this new algorithm is reasonably accurate. EMTP simulation results are shown.

A new technique is proposed for locating partial discharges (PD) in synthetically insulated high voltage cables. The novel method digitally separates the two PD pulses before they are filtered by predictor filters. An experiment on a 20 kV cable under real stress conditions was carried out to test the efficiency of the new technique for fault location and noise suppressiom. It demonstrated the influence of the pulse magnitude and distance in PD detection under noisy conditions.

In this paper, a new power-line conditioning system is proposed. This system is constructed by a flying-capacitor multilevel voltage-source converter (VSC) and two reactors. The phaseshift sinusoidal pulsewidth modulation switching scheme is applied to control the switching devices of this converter. Due to this multilevel VSC and the switching scheme applied to this converter, the system is applicable to distribution systems or industrial applications. The reactive power compensation, harmonic suppression, and load-balancing functions of the power-line conditioner are analyzed. A novel and effective startup procedure is proposed to start up the system. System simulation is carried out to verify the theoretical analysis results. Index Terms--Flying-capacitor multilevel voltage-source converter, phase-shift sinusoidal pulsewidth modulation, power-line conditioner.