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Showing papers in "IEEE Transactions on Power Delivery in 2003"


Journal ArticleDOI
Jen-Hao Teng1
TL;DR: In this paper, a direct approach for unbalanced three-phase distribution load flow solutions is proposed, where two developed matrices, the bus-injection to branch-current matrix and the branchcurrent to busvoltage matrix, and a simple matrix multiplication are used to obtain load flow solution.
Abstract: A direct approach for unbalanced three-phase distribution load flow solutions is proposed in this paper. The special topological characteristics of distribution networks have been fully utilized to make the direct solution possible. Two developed matrices-the bus-injection to branch-current matrix and the branch-current to bus-voltage matrix-and a simple matrix multiplication are used to obtain load flow solutions. Due to the distinctive solution techniques of the proposed method, the time-consuming LU decomposition and forward/backward substitution of the Jacobian matrix or Y admittance matrix required in the traditional load flow methods are no longer necessary. Therefore, the proposed method is robust and time-efficient. Test results demonstrate the validity of the proposed method. The proposed method shows great potential to be used in distribution automation applications.

880 citations


Journal ArticleDOI
TL;DR: In this article, a distribution static compensator (DSTATCOM) is used to compensate for the distortions in source current and voltage at the point of common coupling, where the DSTATCOM is connected with a filter capacitor that allows the high frequency component of the current to pass.
Abstract: The paper discusses load compensation using a distribution static compensator (DSTATCOM). It is assumed that the DSTATCOM is associated with a load that is remote from the supply. It is shown that the operation of a DSTATCOM assuming that it is connected to a stiff source in such situations will result in distortions in source current and voltage at the point of common coupling. To avoid this, the DSTATCOM is connected in parallel with a filter capacitor that allows the high frequency component of the current to pass. However, this generates control issues in tracking, as standard controls such as a hysteresis control are not suitable in these circumstances. This paper proposes a new switching control scheme and demonstrates its suitability for this problem. It also proposes a scheme in which the fundamental sequence components of a three-phase signal can be computed from its samples. The overall performance of the proposed scheme is verified using digital computer simulation studies.

175 citations


Journal ArticleDOI
TL;DR: In this paper, an extended harmonic domain (EHD) method is presented for transient and steady-state analysis of electric networks containing nonlinearities and switching plants components, which is a natural approach for conducting dynamic and steady state studies of the evolution of harmonics in power circuits.
Abstract: A novel methodology is presented in this paper for conducting transient and steady-state analysis of electric networks containing nonlinearities and switching plants components. The method is termed the extended harmonic domain (EHD) method as may be seen as an extension of the harmonic domain (HD) method used in steady-state analysis. It is shown in the paper that EHD is a natural approach for conducting dynamic and steady-state studies of the evolution of harmonics in power circuits containing nonlinear components and flexible AC transmission systems (FACTS) devices. It is also shown in the paper that EHD provides a suitable basis for extending the well-known steady-state power quality indices to the transient range. To illustrate the use of the theory, a three-phase linear circuit and a three-phase PWM-STATCOM are modeled using EHD. The results are compared against those provided by industry standard tools as PSCAD/EMTDC and Matlab.

140 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach, which consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve.
Abstract: Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. The frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. Then, traditional approaches will likely be maloperated in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy-based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from Salford EMTP simulation package and showed a fast and accurate trip operation.

134 citations


Journal ArticleDOI
TL;DR: Test methods for evaluating flashover voltage of ceramic and nonceramic insulators under ice, snow, and cold-fog conditions are recommended in this paper, which describes the procedure to be followed at various stages of an evaluation test including preparation of the test object, insulator precontamination, ice and snow deposits as well as voltage applications and flash-over voltage evaluation.
Abstract: Test methods for evaluating flashover voltage of ceramic and nonceramic insulators under ice, snow, and cold-fog conditions are recommended. The paper describes the procedure to be followed at various stages of an evaluation test including preparation of the test object, insulator precontamination, ice, snow, and cold-fog deposits as well as voltage applications and flashover voltage evaluation. Some relevant parameters for ice accretion, flashover voltage evaluation, artificial pollution, and power source requirements are taken from IEC 60129, IEC 60507, and IEEE Std.-4-1995 on standard techniques for high-voltage testing.

134 citations


Journal ArticleDOI
TL;DR: In this article, an adaptive filter for synchronous detection and extraction of harmonics is presented, which can be used as integral part of the control system of a power electronic apparatus (e.g., STATCOM, APF and UPFC) to generate the desired control signals.
Abstract: This paper provides an adaptive filter for synchronous detection and extraction of harmonics. The filter can be used as integral part of the control system of a power electronic apparatus (e.g., STATCOM, APF, and UPFC) to generate the desired control signals. Stability and convergence analyses of the adaptive filter are presented based on the dynamical systems theory. Performance of the filter is verified as a means for reference signal generation in a shunt active power filter.

127 citations


Journal ArticleDOI
TL;DR: The paper shows that the advanced DC voltage controller (ADCVC), which is a higher hierarchical controller, can meet the targeted voltage margin.
Abstract: Security requires that a system continues to function even when any one subsystem fails. A multiterminal HVDC system consists of N voltage-source converters (VSCs) exchanging power through a DC network. When any one converter is lost, before the surviving (N-1) converters have time to re-establish a new power balance, the excess DC power can produce voltage spikes which are destructive to the power electronic switches. The paper shows that the advanced DC voltage controller (ADCVC), which is a higher hierarchical controller, can meet the targeted voltage margin.

122 citations


Journal ArticleDOI
TL;DR: In this paper, an original thermal model of transformers with ONAN cooling was developed, which takes into account the influence of nonlinear thermal characteristics in transient thermal processes; instead of exponential functions and time constants, the numerical solution of differential equations is used.
Abstract: In the authors' previous work (1997), an original thermal model of transformers with ONAN cooling was developed. The model takes into account the influence of nonlinear thermal characteristics in transient thermal processes; instead of exponential functions and time constants, the numerical solution of differential equations is used. The model delivers one characteristic temperature in copper (solid insulation) and one characteristic temperature in oil. In this paper, the analysis stresses the definition of the hot-spot temperature of the solid insulation by using easily measurable quantities. Then, the parameters of the model can be precisely determined from inexpensive measurements in a short-circuit heating experiment and the model can deliver the hot-spot temperature. The experimental base of this research are the measurements on a 630-kVA, 3 /spl times/ 10 kV/3 /spl times/ 6 kV ONAN transformer equipped with 112 temperature sensors (102 inside the central positioned 10-kV winding).

119 citations


Journal ArticleDOI
TL;DR: In this paper, a new adaptive fault protection scheme for transmission lines using synchronized phasor measurements is presented, which includes fault detection, direction discrimination, classification and location, and fault location indices are derived by using two-terminal synchronized measurements incorporated with distributed line model and modal transformation theory.
Abstract: This paper presents a new adaptive fault protection scheme for transmission lines using synchronized phasor measurements. The work includes fault detection, direction discrimination, classification and location. Both fault detection and fault location indices are derived by using two-terminal synchronized measurements incorporated with distributed line model and modal transformation theory. The fault detection index is composed of two complex phasors and the angle difference between the two phasors determines whether the fault is intemal or external to the protected zone. The fault types can be classified by the modal fault detection index. The proposed scheme also combines on-line parameter estimation to assure protection scheme performance and to achieve adaptive protection. Extensive simulation studies show that the proposed scheme provides a fast relay response and high accuracy in fault location under various system and fault conditions. The proposed method responds very well with regard to dependability, security and sensitivity (high-resistance fault coverage).

116 citations


Journal ArticleDOI
TL;DR: A new approach of digital relays for transmission line protection is presented, consisting of a preprocessing module based on discrete wavelet transforms in combination with an artificial neural network for detecting and classifying fault events.
Abstract: A new approach of digital relays for transmission line protection is presented. The proposed technique consists of a preprocessing module based on discrete wavelet transforms (DWTs) in combination with an artificial neural network (ANN) for detecting and classifying fault events. The DWT acts as an extractor of distinctive features in the input signals at the relay location. This information is then fed into an ANN for classifying fault conditions. A DWT with quasioptimal performance for the preprocessing stage is also presented.

112 citations


Journal ArticleDOI
TL;DR: In this paper, the authors review the common practice and analytical models for the representation of aggregate linear load in harmonic propagation and distortion studies and recommend a comprehensive modeling approach that accounts for all major components of the modern load including electronic load and background distortion.
Abstract: This paper reviews the common practice and analytical models for the representation of aggregate linear load in harmonic propagation and distortion studies. Simulation results in this paper demonstrate the high sensitivity of harmonic propagation and distortion to the model type used to represent the load. Comparison of the several load models in the literature shows a significant difference on the system impedance around the dominant resonance. The paper recommends a comprehensive modeling approach that accounts for all major components of the modern load including electronic load and background distortion.

Journal ArticleDOI
TL;DR: In this paper, an alternative approach for the analysis of dissolved gas data, which can produce more convincing interpretation and fault diagnosis, has been compared and validated using conventional interpretation schemes and real fault-cases, thereby proven to be capable of enhancing the condition monitoring of power transformers.
Abstract: Incipient faults in power transformers can degrade the oil and cellulose insulation, leading to the formation of dissolved gases. Even though established approaches that relate these dissolved gas information to the condition of power transformers are already developed, it is discussed in this paper that they still contain some limitations. In view of that, this paper introduces an alternative approach for the analysis of dissolved gas data, which can produce more convincing interpretation and fault diagnosis. The proposed approach, which is based on the data mining methodology and the self-organizing map, has been compared and validated using conventional interpretation schemes and real fault-cases, thereby proven to be capable of enhancing the condition monitoring of power transformers.

Journal ArticleDOI
TL;DR: This paper is a review of the different single and three-phase harmonic load flow formulations of the bibliography and presents the data, unknowns, and equations of these formulations in balanced network consideration.
Abstract: This paper is a review of the different single and three-phase harmonic load flow formulations of the bibliography. It presents the data, unknowns, and equations of these formulations in balanced network consideration. The influence of the main harmonic load flow hypothesis (harmonic interaction and fundamental power consumption consideration) in the final load flow results is studied in an example.

Journal ArticleDOI
TL;DR: A review of the time-domain polarization measurement techniques for the condition assessment of aged transformer insulation is presented in this article, where the polarization process is first described with appropriate dielectric response theories and then commonly used polarization methods are described with special emphasis on the most widely used return voltage (RV) measurement.
Abstract: This paper presents a review of the time-domain polarization measurement techniques for the condition assessment of aged transformer insulation. The polarization process is first described with appropriate dielectric response theories and then commonly used polarization methods are described with special emphasis on the most widely used "return voltage" (RV) measurement. Most recent emphasis has been directed to techniques of determining moisture content of insulation indirectly by measuring RV parameters. The major difficulty still lies with the accurate interpretation of return voltage results. This paper investigates different thoughts regarding the interpretation of RV results for different moisture and ageing conditions. Other time domain polarization measurement techniques and their results are also presented in this paper.

Journal ArticleDOI
TL;DR: The test results confirm that the proposed ENNs are much more diagnostically accurate and require less learning time than the existing approaches.
Abstract: This paper proposes evolving neural nets (ENNs) for fault diagnosis of power transformers. Based on the proposed evolutionary algorithm, the ENNs automatically tune the network parameters (connection weights and bias terms) of the neural nets to achieve the best model. The ENNs can identify complicated relationships among dissolved gas contents in transformer oil and corresponding fault types, using the global search capabilities of the evolutionary algorithm and the highly nonlinear mapping nature of the neural nets. The proposed ENNs have been tested on the Taipower Company diagnostic records and compared with the fuzzy diagnosis system, artificial neural networks, and the conventional method. The test results confirm that the proposed ENNs are much more diagnostically accurate and require less learning time than the existing approaches.

Journal ArticleDOI
TL;DR: In this article, a power quality (PQ) study performed on a PV generator in order to estimate the effects that inverter-interfaced PV dispersed generation might have upon the quality of electric power is presented.
Abstract: The use of environmentally clean photovoltaic (PV) dispersed generation will become more widespread in the future due to anticipated cost reductions in PV technology. This paper summarizes the results of a power quality (PQ) study performed on a PV generator in order to estimate the effects that inverter-interfaced PV dispersed generation might have upon the quality of electric power. Different interpretations of the harmonic distortion limits set in the IEEE 519-1992 standard are performed together with a comparison with the BC Hydro's harmonic current limits. This paper also includes a statistical analysis of all measurements recorded with the help of two PQ monitors, an evaluation of the results from a connection/disconnection test, and harmonic simulation results.

Journal ArticleDOI
TL;DR: In this paper, a voltage soured converter-based back-to-back installation at Eagle Pass substation in the State of Texas has been investigated and the root cause of the failures has been identified.
Abstract: Voltage sourced converter-based transmission controllers, which use gate turn off switching components, introduce a new type of high voltage stress on insulation systems and materials. Fast switching components like IGBTs may generate or cause high-frequency voltages, which are superimposed upon the power frequency (50/60 Hz) voltage. Insulation within the station may thereby be continuously exposed to a new type of voltage stress, for which it has not been designed or tested. The high-frequency voltages may, under special circumstances, cause insulation damages at magnitude levels, which are well below the dielectric voltage withstand at power frequency. Compact insulation systems with resistive/refractive grading of the electrical field are particularly critical. Several compact type cable terminations rated 24 kV with resistive/refractive stressgrading have failed in the voltage soured converter-based back-to-back installation at Eagle Pass substation in the State of Texas. Through field measurements, laboratory tests, and simulations, the root cause of the failures has been identified. The compact cable terminations have been replaced by another type of termination, which is not sensitive to high-frequency voltages. The voltage sourced converter-based back-to-back installation in Eagle Pass is a joint ABB, EPRI, and AEP field demonstration project, which has been commissioned.

Journal ArticleDOI
TL;DR: In this article, the influence of different factors on the impulse characteristics of grounding devices was analyzed and the effects of different parameters on impulse grounding resistance and impulse coefficients of different transmission tower grounding devices were discussed.
Abstract: Reducing grounding resistance of a transmission tower grounding device is an important method to improve performance of transmission lines against lightning. Principles of impulse characteristics of grounding devices were discussed. Impulse experiments using grounding device models were systematically performed to analyze the influence of different factors on the impulse characteristics of grounding devices. During the experiments, soil resistivity was changed in the range of 100 to 5103 /spl Omega//spl middot/m. Effects of different parameters on impulse grounding resistance and impulse coefficients of different transmission tower grounding devices were discussed. Formulae to calculate impulse coefficients and power frequency grounding resistance of different grounding devices were obtained.

Journal ArticleDOI
TL;DR: In this paper, potential problem areas in using RMS values in power quality assessment are identified and discussed, as well as potential solution areas for using root mean square mathematical operations for power quality analysis.
Abstract: The root mean square mathematical operation is widely used in power engineering. The process has a frequency response characteristic and an associated time constant which is important especially for short term signals. Potential problem areas in using RMS values in power quality assessment are identified and discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors attempted to work out a method of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy.
Abstract: The degradation of electrical insulation in transformers is more often due to thermal stress. In this paper, the authors attempted to work out a method of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy. A theoretical model has been developed based on the boundary value problem of heat conduction in transformer winding using finite integral transform techniques. The model requires, in addition to electrical parameters of the transformer, information on the actual design data. The authors believe that this model predicts HST with precision and also indicates a possibility of online data acquisition.

Journal ArticleDOI
TL;DR: In this paper, a new solid-state on-load tap-changer topology was proposed for an 800-kVA, 20-kV/400-V distribution transformer.
Abstract: High controllability advantages of power electronic switches lead to their application in the tap-changer of distribution transformers. Using such switches leads to quick operation of the tap-changer and, thus, improved performance. Moreover, their application reduces maintenance and repair costs of tap-changers. This paper introduces a new solid-state onload tap-changer topology that has many steps with fewer power electronic switches compared with those reported in the literature. This tap-changer is designed for an 800-kVA, 20-kV/400-V distribution transformer, and the results are discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an independent and bidirectional active and reactive power flow control in the transmission line as a voltage-sourced converter (VSC)-based unified power flow controller (UPFC) does.
Abstract: The independent control of active and reactive power flow in a transmission line is necessary for the transfer of bulk power along a desired path in the most economical way. A "Sen" transformer (ST) uses transformer and tap changers that are traditionally used to build a voltage-regulating transformer (VRT) and a phase angle regulator (PAR). The ST regulates the voltage at a point in the transmission line as a VRT does. Additionally, the ST provides an independent and bidirectional active and reactive power (P and Q) flow control in the transmission line as a voltage-sourced converter (VSC)-based unified power flow controller (UPFC) does. Although both the ST and the PAR use a comparable number of components, the ST provides an area of controllability in the P-Q plane similar to a UPFC, while the PAR provides a linear P-Q characteristic. The technology of transformer and tap changer is proven to be reliable and cost-effective when compared with the emerging technology of VSC. The new ST is adequate to provide independent control of active and reactive power flow in most utility applications.

Journal ArticleDOI
TL;DR: In this article, a fair comparison between direct sequence code division multiple access (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) systems for broadband downstream power-line communications (PLCs) is provided.
Abstract: This paper provides a fair comparison between direct sequence code division multiple access (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) systems for broadband downstream power-line communications (PLCs). The considered schemes seem particularly suitable for high bit rate broadcast flexible communications on low voltage grid in order to guarantee local access. The performance of the considered systems is expressed in terms of bit error rate (BER), derived by simulations under the assumptions of frequency-selective multipath fading channel and additive colored Gaussian noise according to the in-building networks model, under the same overall working conditions of bandwidth occupation, transmitted power, and global data rate.

Journal ArticleDOI
TL;DR: In this article, the authors measured the magnetic field created by electrical appliances and high voltage lines and analyzed the degree of compliance with recent applicable European regulation, which accurately predicts the measured values.
Abstract: The relationship between magnetic fields and the health of people is increasingly being investigated. International organizations have proposed bylaws that put limits on the value of the generated magnetic field. In this work, we measure the magnetic field created by electrical appliances and high voltage lines and we analyze the degree of compliance with recent applicable European regulation. The simulation of the magnetic field generated by electrical lines through a simple model accurately predicts the measured values. The model is used to simulate the behavior of the lines under given conditions. In both cases, an FFT analysis of the magnetic field waveform was performed to study the frequency and amplitude of the possible induced currents.

Journal ArticleDOI
TL;DR: In this paper, a fault location principle using one terminal voltage and current data for EHV transmission lines is described, which is based on distributed parameter line model, breaking through the traditional single-ended fault location ideas.
Abstract: A new fault location principle using one terminal voltage and current data for EHV transmission lines is described in this paper, which is based on distributed parameter line model, breaking through the traditional single-ended fault location ideas. The voltage profile along the healthy line could be calculated using single-ended voltage and current data; however, the voltage profile behind the fault point is not true for a faulted line. Even though, notice the fact that the norm value of derivative function of the "fictitious profile" to distance is minimum at fault point, based on which the fault location function is constructed. The numerical algorithm is also described; this principle is proved by EMTP simulations to be immune to fault resistance, fault types, and fault inception angle. Theoretically, the accuracy of the principle is proportional to the sampling rate of the locator.

Journal ArticleDOI
TL;DR: In this paper, the instantaneous flicker sensation of rapidly varying loads is evaluated by means of a new frequency domain method, applied to the voltages of DC and AC arc furnaces.
Abstract: In this paper, flicker magnitudes of rapidly varying loads are evaluated by means of a new frequency domain method. Analytical expressions of the instantaneous flicker sensation are obtained in terms of interharmonic voltages. The dynamic response of flicker magnitudes of such loads can be clearly described with this analysis, as well as the individual contribution of each interharmonic to the flicker sensation. The proposed method, applied to the voltages of DC and AC arc furnaces, provides very satisfactory results that have been validated with measurements performed with the standardized IEC flickermeter.

Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview of the IEC flicker measurement and assessment procedures and compare them with existing IEEE flicker standards to show the benefits of IEC methodology.
Abstract: This paper is intended to provide an overview of the IEC flicker measurement and assessment procedures. The IEC procedures are correlated with existing IEEE flicker standards to show the benefits of the IEC methodology. Application issues, such as customer impact assessment, are also discussed. Three case studies, two field tests, and one EMTP analysis are provided to show the correlation of IEC flickermeter output values with documented customer complaints. The case studies also provide areas where modifications to the IEC flicker standards may be necessary when developing a new IEEE flicker standard.

Journal ArticleDOI
TL;DR: In this article, the influence of the personal computer processing mode on the generation of line current harmonics has been investigated using a university library building containing over 370 PCs, and the harmonics were monitored from the building switchboard using purpose-designed hardware.
Abstract: The influence of the personal computer processing mode on the generation of line current harmonics has been investigated using a university library building containing over 370 PCs. The harmonics were monitored from the building switchboard using purpose-designed hardware. The PCs were set to execute four types of processing mode: idle, numerical processing, floppy, and hard disk accesses. The results recorded were indicative of harmonics caused by the PC box only, and secondary effects of harmonic production caused by distorted supply voltages were avoided. The results show that hard disk accesses cause the highest level of harmonic production affecting the 3rd and 5th components. Harmonic attenuation was very apparent when comparing the results between a single PC and 124 PCs connected to the same supply phase. However, attenuation and diversity effects due to changes in loading level on the PC power supply were not as predicted, showing an increase in harmonic generation with line current RMS level.

Journal ArticleDOI
TL;DR: An investigation of a methodology using intelligent learning techniques based on system measurements to construct power system load models alongside with distribution network reduction and a population diversity-based genetic algorithm is developed to obtain the structure and parameters of the load model.
Abstract: This paper is concerned with an investigation of a methodology using intelligent learning techniques based on system measurements to construct power system load models alongside with distribution network reduction. A comprehensive load model is proposed to represent the loads in an area of a power system. A population diversity-based genetic algorithm (GA) is developed to obtain the structure and parameters of the load model. Simulation results on a five-bus power system and an IEEE 30-bus power system are given to show the potential of this new methodology of power system modeling.

Journal ArticleDOI
TL;DR: In this article, the seasonal influence on the safety of grounding system by numerical analysis method is systematically discussed, and special measures should be used, long vertical grounding electrodes added to the grounding system can effectively attenuate the seasonality influence, and improve the safety.
Abstract: The low or high resistivity soil layer formed in raining or freezing season affects the safety of the grounding system, and leads to changes of grounding resistance of the grounding system, step and touch voltages on the ground surface. This paper systematically discusses the seasonal influence on the safety of grounding system by numerical analysis method. If the thickness of the low-resistivity soil layer formed in raining season is smaller than the burial depth of the grounding system, the touch voltage would increase. On the other hand, the raining season leads the limit of touch voltage is smaller than the actual touch voltage, even if a surface granite layer is used. The influences of raining on the safety of grounding system must be comprehensively considered. When the high resistivity soil layer is formed in freezing season, the grounding resistance, step and touch voltages would increase with the thickness or resistivity of the freezing soil layer. When the thickness of high resistivity soil layer exceeds the burial depth of the grounding system, the grounding resistance, step and touch voltages would increase sharply, and the touch voltage would exceed the limit of touch voltage decided by a surface granite layer. In order to ensure the safety of the grounding system in freezing season, the grounding system must be designed carefully, and special measures should be used, long vertical grounding electrodes added to the grounding system can effectively attenuate the seasonal influence, and improve the safety of the grounding system.