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In this paper, fault location on three-terminal and tapped transmission lines without requiring line parameters is presented, which mitigates the effect of line parameter variations due to weather and loading conditions on fault-location accuracy. For three-terminal lines, a fault-location method is presented, which utilizes postfault measurements of all three terminals. For tapped lines, two methods are presented. The first one uses postfault measurements of the main two terminals. The second one needs one cycle of prefault measurements at the main terminals as well. Synchronized transient-based measurements are used in methods proposed in this paper. In all of the presented methods, the fault-location problem is converted to an optimization problem and then solved to find the line parameters and the accurate location of the fault. The simulations are carried out by alternative transients program/electromagnetic transients program (ATP/EMTP) software, and the presented algorithms are executed by MATLAB. Simulation results assess the effects of fault resistance, type, and inception angle on the accuracy of the presented methods. Further discussion is also provided on the impacts of synchronization errors, noisy measurements, and nonresistive faults.

Power-electronic sources, such as Type 3 wind turbine generators and static synchronous compensators (STATCOM), interface to the grid through, partial- or full-scale, and power converters that have inherently fast switching capability to control their output current during short circuits. The short-circuit current is a function of the specific converter control algorithm and differs significantly from the conventional rotating machine sources without converter interfaces. Therefore, if a transmission-line protection scheme is designed for conventional sources, (not taking into account these differences in short-circuit current characteristics), reliability can be at risk. Using real-life short-circuit currents on lines supplied by sources having a power converter interface, this paper illustrates the reliability risk to conventional line protection schemes, in particular, to those which use negative-sequence quantities for the detection of unbalanced faults. This paper discusses the protection schemes, adopted by BC Hydro–a large Canadian Electric Utility, for transmission lines interconnecting Type 3 wind turbine and STATCOM sources. Their application for ground faults is independent of the converter control algorithm as long as the source is interconnected to the grid via a transformer which is a source of zero-sequence current.

Locating a fault in a series-capacitor-compensated transmission line (SCCTL) is a challenging task due to the action of a metal-oxide varistor a nonlinear element present as a part of the protection system of the series capacitor. In this paper, an accurate fault-location algorithm that uses synchronized measurements from both ends of the SCCTL is presented which provides fault-location results without using the model of MOV or natural fault loop for single-phase-to-ground, and double-phase-to-ground faults. Another salient feature of the proposed technique is that the subroutines for locating faults in different sections transmission line yield almost identical fault-location results regardless of which section the transmission line is faulted. The proposed technique could also be extended to the double-circuit transmission lines. First, the proposed technique is introduced and its features are elaborated through detailed mathematical analysis. Thereafter, a 500- $\text{kV}$ system with an SCCTL is designed in PSCAD, while the fault-location algorithm is modeled in MATLAB. The proposed algorithm is tested through simulations covering various fault scenarios in an SCCTL. For performance evaluation, the comparative analysis of the proposed technique with a well-known existing technique is performed in this paper.

Series compensated transmission lines challenge legacy protection schemes. In this paper, a dynamic state estimation based protection (EBP) method is proposed to address these challenges. The method requires GPS synchronized measurements at both ends of the line and a high-fidelity model of the protection zone. The paper presents the dynamic model of the protection zone and its impact on the performance of the protection scheme. Numerical simulations show that the method can correctly identify faults, independently of position and type. The paper also compares the proposed method versus legacy protection functions such as distance protection and line differential protection. The comparison shows faster detection of internal faults, immunity to current inversion caused by series capacitors (SCs) and improved detection sensitivity for high-impedance faults.

In this paper, a new adaptive single-phase reclosing method for high-voltage transmission lines is proposed. This method employs local voltage magnitude and angle of the faulted phase. It is shown in this paper that the proposed method is able to quickly identify the fault type and the arc extinction if the fault is transient. This method is effective for various system configurations, including ideally and partially transposed transmission lines, untransposed lines, as well as transmission lines with or without a shunt reactor. Superior performance of the proposed method has been verified using 550 case studies simulated in PSCAD and Matlab and a real case related to a 765-kV transmission line.

In this paper, typical strengths, fault levels, and source impedances are thoroughly analyzed and calculated for the study of quality of supply in 230/400 V 50 Hz distribution systems. Considering all the disparity in distribution network design, this study is based on a comprehensive database containing typical arrangements and equipment in U.K./European systems, as well as on fully documented generic network models supplying four residential load subsectors in the U.K., i.e., from metropolitan to rural areas. Thus, this paper proposes an alternative method for determining reference values of network supply impedances and short-circuit fault levels at different points and locations of the medium-to-low voltage distribution system. The aim of this study is to provide a wider range of benchmark values than those stipulated in the IEC 60725 Standard, which only defines a single-reference threshold of public supply impedances for all types of distribution systems and residential customers. In order to assist network operators in the planning and design of their distribution systems, these values are further disaggregated and classified in this paper according to network/demand type.

This paper presents a new approach for locating short-circuit faults on untransposed transmission lines. Various fault-location algorithms have been proposed previously for transposed lines, which may not always be the case in practice. Existing methods usually require measurements recorded from one or two terminals of the faulted line, which may not be always available. To complement existing methods, this paper proposes a novel, general fault-location method for untransposed lines using sparse wide-area measurements, which is also applicable to transposed lines. Phasor measurement units are utilized to obtain the sparse wide-area synchronized measurements, which may be captured from buses far away from the faulted line. This method fully considers inherent unbalances of untransposed lines, and fully models shunt capacitances of lines based on a distributed parameter line model. Optimal estimation theory is exploited to make the most of available measurements for enhanced estimation. The method is able to locate faults on single-circuit and double-circuit line configurations, and is immune to fault resistances. Another feature of this method is that it does not require the fault type to be known. Extensive simulation studies using the Electromagnetic Transients Program have been performed, and quite accurate results have been achieved.

With the integration of intermittent renewable generation, transmission voltage problems have become more dynamic. The deployment and tuning of numbers of VAr compensators at various locations may not be cost-effective. This paper presents an alternative method, which utilizes existing parallel transformers in distribution networks, to provide reactive power absorption services for transmission systems with low demands. The operation of parallel transformers in small different tap positions, that is, with staggered taps, can provide a means of absorbing reactive power. The aggregated VAr absorption from many pairs of parallel transformers could be used to provide voltage support to the upstream transmission network. This paper focuses on the economic and technical analyses of using the tap staggering method. For the economic analysis, the associated costs of applying the tap staggering technique are investigated through static load-flow studies. The IEEE Reliability Test System is used to carry out the studies and the results are compared with the installation of shunt reactors. In the technical studies, the dynamic impacts of tap staggering or reactor switching on transmission voltages are analyzed. From the results, the tap staggering technique has more economic advantages than reactors and can reduce the voltage damping and overshoots during the transient states.

This paper presents the results of a comparative analysis among three methods for attributing responsibilities of voltage unbalance in the electrical network, namely, the IEC, three-phase power flow, and conforming and nonconforming currents methods. To do this, computational and experimental simulations are carried out based on employing a system comprised of a perfectly transposed transmission line and two loads that are not always balanced. The cases selected for this study also permit the identification of the main advantages and disadvantages of each method under evaluation. This work is characterized as a topic of great interest to the regulatory agencies responsible for establishing regulations, and for utilities and consumers. It is relevant because by using the methods investigated in this paper, the identification of the sources, which generates unbalance, the division of responsibilities, and the application of penalties due to limit transgression will be possible.

Series impedance and shunt admittance parameters of transmission lines are fundamental data for various online and offline power system studies. This paper shows that the active power, reactive power, and voltage magnitude ( $P$ , $Q$ , $V$ ) data measured at the two ends of a transmission line are sufficient to determine the positive-sequence line parameters. The phase-angle information is not essential. Since the $P$ , $Q$ , and $V$ data are readily available from the supervisory control and data-acquisition systems, the proposed method can be easily implemented in existing control centers. Algorithms, characteristics, performances, and potential applications of the proposed method are presented in this paper. Simulation study and field test results show that the proposed technique can be a useful addition to the energy-management systems of utility companies.

This paper focuses on the parameter estimation of transmission lines which is an essential prerequisite for system studies and relay settings. Synchrophasor measurements have shown promising potentials for the transmission line parameter estimation. Majority of existing techniques entail existence of phasor measurement units (PMUs) at both ends of a given transmission line; however, this assumption rarely holds true in nowadays power networks with few installed PMUs. In this paper, a practical technique is proposed for the estimation of transmission line parameters while the required data are phasor measurements at one end of a given line and conventional magnitude measurements at the other end. The proposed method is thus on the basis of joint PMU and supervisory control and data acquisition (SCADA) measurements. A non-linear weighted least-square error (NWLSE) algorithm is employed for the maximum-likelihood estimation of parameters. The approach is initially devised for simple transmission lines with two terminals; then, it is extended for three-terminal lines. Numerical studies encompassing two- and three-terminal lines are conducted through software and hardware simulations. The results demonstrate the effectiveness of new technique and verify its applicability in present power networks.

Lightning is a substantial cause that leads to serious lightning failures, which has a significant influence on the normal operation of the entire power grid. This paper mainly focused on several regions of China with serious lightning activity, presenting the lightning performance of power grids by statistics obtained from long-term monitoring data, and intended to indicate some general characteristics. The lightning tripout rate, the shielding failure tripout ratio, the occurrence frequency corresponding tripout failures of different phases of single-circuit or double-circuit transmission lines, and the multicircuit simultaneous tripout failures of multicircuit transmission lines were analyzed. These statistical results presented a panorama of the lightning protection effect of transmission lines in China. The statistical data in this paper are informative to guide the future research or engineering practice of lightning protection of transmission lines, and will be helpful to evaluate the analysis methods of lightning performance of transmission lines.

For an LCC–MMC hybrid HVDC transmission system with reverse current blocking diodes, this paper presents a method for dc-side harmonic current calculation and dc-loop impedance calculation. First, in the calculation of dc-side harmonic currents, the line-commutated converter at the rectifier side is replaced by the three-pulse harmonic voltage sources; the modular multilevel converter is represented by an equivalent passive circuit based on the linearization theory; an improved calculating method for the coupled line model is introduced into calculating the admittance matrix of the dc transmission lines to improve the computational efficiency; and then this paper describes the complete procedures of the proposed method. Second, based on the dc-side equivalent models mentioned before and the nodal voltage analysis method, this paper presents an analytical method for the calculation of dc-loop impedance according to the definition of dc-loop impedance Finally, the PSCAD/EMTDC simulation verifications have been carried out based on a 1500 MW/ ${+} 500$ kV MMC-HVDC system, a 3000-MW/ ${\pm}$ 500-kV LCC–MMC hybrid HVDC system, and its dc network. The simulation results and the analytical results coincide with each other, and the effectiveness of the proposed methods is proved.

Due to the electromagnetic induction between transmission lines and the associated grounding wires, power frequency current causes flow into the ground network via the metallic tower, which may interfere with grounding resistance measurements. This paper analyzes the mechanisms of this interference, and shows that power frequency interference becomes stronger at phase-wire transposition towers. Grounding resistance measurement by the variable frequency (VF) method has been proven to be effective in dealing with power frequency interference. However, the test equipment based on the VF method is always deactivated when the external interference voltage exceeds a preset level in order to avoid false readings. This paper aims at tackling the problem by introducing a reverse phase cancellation (RPC) method, which acquires and processes the interference signal before generating a cancelling signal with the same amplitude and frequency and a phase which is exactly opposite in polarity. This paper proves that the RPC method represents an excellent improvement over the VF method since it retains the advantages of VF and avoids the trip-out of test equipment due to excessive interference.

Shunt reactors are applied to long extra high-voltage (HV) transmission lines to compensate for their natural capacitance which otherwise could cause overvoltages under light load conditions. However, when the level of compensation approaches around 65% or higher, these reactors themselves can, due to contingency, become the cause of hazardous overvoltages during unbalanced open-phase conditions on the healthy line. This paper reports on an overvoltage incident that occurred on a 500-kV 72% shunt-compensated line in the BC Hydro system. The overvoltage occurred when one of the breaker poles failed to interrupt the current following an inadvertent three-phase trip of the healthy line. The uninterrupted current kept one phase energized for an extended time. Temporary overvoltages during this condition and restrike transients eventually led to surge arrester failures at both terminals. Analysis of voltage and current recordings provided useful insight into the mechanism responsible for the damaging overvoltages as well as the protection and control responses during the disturbance. The intent of this paper is to share the knowledge gained from analyses of the recorded waveforms with other utilities either having or planning for highly compensated lines.

This paper shows that a previously proposed linear-system identification method based on frequency partitioning and adaptive weighting can be successfully applied to the phase-domain frequency-dependent modeling of overhead transmission lines for electromagnetic transient (EMT) simulations. As the framework of the phase-domain modeling, the universal line model (ULM) is used, and the frequency responses of the characteristic-admittance and the propagation-function matrix are realized by linear equivalents obtained by the identification method mentioned above, instead of the well-known Vector Fitting (VF) method. In this paper, numerical techniques to enhance the identification method for this phase-domain line modeling application are also presented. For validation, the proposed approach is applied to the modeling of an existing 500-kV double-circuit transmission line. The effectiveness of the numerical techniques for enhancements are shown through the modeling process, and transient waveforms obtained by the proposed approach are compared with those by the rigorous Laplace transform method and also with a field-test result.

This paper demonstrates the need for and provides an improved fitting of the line parameters when a wide range of frequencies with emphasis on the dc response is the objective. The improved fitting is based on a low-order fitting of a function error for each of the line parameters, that is, the characteristic admittance and propagation function, in the low-frequency range. The function error represents the difference between the analytical evaluation of the line parameters, that is, obtained from a frequency-dependent distributed parameters line model, and their initial rational approximation, for example, given by an electromagnetic transients software tool. The approximated function error, added to the initial rational approximation of the line parameters, provides the enhanced fitted line model. The enhanced fitting improves the dc response of the line and ensures numerical stability in time-domain simulations. This paper applies the proposed fitting approach to the universal line model for time-domain simulations. The simulation results by the enhanced fitting are validated by comparing the results with those obtained from a frequency-domain line model (FDLM). Two case studies are presented to illustrate the proposed fitting approach.

This paper is divided into two main parts. The first one describes the computation of the number of lightning strokes that directly hit transmission lines as well as those strokes that hit the earth's surface near a line and can provoke very high overvoltages. The second one describes a process for computing the consequent short circuits in a line caused by both types of stroke incidence. In the companion paper, some application examples are presented.

This paper presents a new approach to optimal exploitation and reactive power control of long inhomogeneous high-voltage ac cable lines, such as submarine interconnectors including significant land cable stretches. Voltage and reactive power profiles are discussed, highlighting the requirements for full exploitation of power transmission capacity, and giving formulae for optimal voltage control. Capability curves for the lossy inhomogeneous cable line are discussed; this paper also proposes a simple algorithm for controlling the reactive power flow at one end of the line independently from active power, using variable shunt reactors and tap-changing transformers. The application of the presented treatment to a real inhomogeneous line, that is, the 118-km-long 245-kV–50-Hz Malta–Sicily interconnector currently under construction, yields maximum power and optimal voltage drop values in close agreement with detailed simulation results. Power-flow simulations also confirm the effectiveness of the proposed reactive power control algorithm. Finally, total transmission losses associated with the proposed optimal voltage control are evaluated and shown to be competitive with those of state-of-the-art HVDC–VSC systems.

This paper presents a fully automatic leak detection system for slow oscillation high-pressure fluid-filled (HPFF) circuits. It also presents the concept of detecting leaks in such circuits, utilizing only a limited number of sensors. It will describe algorithms built upon this concept, including two different approaches to the construction of the decision module, crucial for detection capabilities. The proposed solution utilizes adaptive digital filters for modeling the circuit behavior and a Bayesian network coupled with a software leak simulator in the decision stage. These tests were performed using data obtained from a real-life circuit, including real-leak data. This paper may enable practical application of high-precision low-cost leak detection solutions for a wide range of HPFF circuits.

This paper proposes a new method of risk assessment for lightning shielding flashover in transmission lines. This is used to improve the performance of lightning shielding failure which is a frequently serious problem. The method can be efficiently implemented in the optimization of a 3-D model. Three-dimensional laser scanning is used to derive the analytical 3-D model to high precision. This includes the data of the whole span line's structure and terrain parameters. In this study, the evaluation of lightning shielding flashover risk of each tower is calculated using the whole span calculation method associated with the laser scanning data and the given parameters of lightning activities. The evaluation results for the Gechen line in the zone near the Three Gorges area are presented based on the proposed method. Using a comparison of theoretical values and actual statistical data, this paper concludes that the proposed new method has better performance than the traditional method.

The geomagnetically induced currents (GICs) produced in power systems during magnetic storms are a function of the electric-field amplitude and direction, and the characteristics of the power system. This paper examines the influence of a number of power system characteristics, which include the resistances and structures of the conductors; the length of the transmission lines; the number, type, and resistances of transformers, the substation grounding resistances, and the topology of the network. It is shown that GIC grows with increasing line length but approaches an asymptotic constant value, and a more relevant parameter than the individual line length is the length of the entire system. This paper also derives the effective GIC for a conventional transformer and an autotransformer, and analyzes the behavior of GIC when the network topology changes illustrated with the GIC-Benchmark Model. The results of these studies provide a guide to estimating GIC impacts on a power network.

This paper presents the interaction between the overhead transmission lines (OHTLs) and their towers. In this paper, the electric field around the tower of the overhead transmission lines is calculated. The charge simulation method, combined with the image method, is used to develop a model that consists of subconductors of the OHTLs and the tower. The charges on the surface of each subconductor of the overhead transmission lines are simulated by a set of infinite line charges, of various charge densities, along the length of the subconductor, and the induced charges on the surface of the tower are simulated by a set of finite line charges.

The mechanism of vertical-arrayed double-bundle transmission-line conglutination is studied in this paper through experiments on a laboratory-based physical model with a 230-m span. Based on the equivalence principle, the conglutination problem in real-world transmission lines has been reproduced in high-voltage and heavy-current experiments where the test circuit is compensated by a series capacitor, so that the output current is continuously adjustable by the voltage regulator and power current transformer. This paper presents, in detail, the experiments carried out, and demonstrated the threshold factors associated with the conglutination phenomenon. The investigation revealed that the number one factor contributing to transmission-line conglutination is the electromagnetic force, which, in turn, is affected by the space between the lines; initial sag and ambient temperature also play important roles. The research results with a thorough understanding of the mechanism of transmission-line conglutination can help provide an understanding of the mechanisms and will enable conduction of numerical analysis of the phenomenon.

The reduced-scale model of HVDC transmission lines in the laboratory is widely used to investigate the ionized fields. This paper is aimed at analyzing impact factors of the ion-current density measurement system based on Wilson plates in the laboratory. Both experimental and numerical simulation methods are used to obtain the characteristics of the measurement system. The results show that measurement data can be calibrated with different Wilson plates, and suitable parameters are proposed in this paper to meet the requirement of measurements. The measurement system described in this paper can be used in other similar applications.

Fault location is considered as one of the essential techniques enabling a smart grid. This paper presents a novel fault location approach for double-circuit transmission lines. Various existing algorithms usually require measurements recorded from one or two terminals of the faulted line. However, when such measurements are not available, these methods are not applicable. To fill this gap, this paper proposes a fault location method by harnessing current measurements from one or more branches, which may not be necessarily taken from the faulted section. The currents from multiple branches are synchronized and can be obtained from phasor measurement units installed in the system. The bus impedance matrix technique is exploited to develop the new method. The shunt capacitance of the line is fully considered by utilizing the distributed parameter line model. The network data are assumed to be available. When multiple synchronized current measurements are available, an optimal estimator capable of identifying possible bad measurement data and, thus, further enhancing the fault location is also proposed. Quite accurate results have been achieved based on simulation studies.

Shield wire segmentation has been used for quite some time as an effective method for reducing transmission-line power losses, with most segmented shield wire applications on extra high-voltage lines utilizing phase-to-phase power-line carrier (PLC) coupling. As transmission system efficiency becomes more of a priority, some utilities may consider applying segmented shield wires to lower voltage lines, such as 115-kV and 230-kV lines, which most often utilize single-phase-to-ground PLC coupling. Thus, knowledge of the effects of segmented shield wires on PLC signal attenuation for various coupling methods would be useful to relay engineers. The purpose of this paper is to present a generalized method to model transmission lines for signal attenuation calculation at PLC frequencies, with special consideration given to shield wire connections. Terminating impedance and phase wire transposition are considered as well. The modeling method presented is validated with field measurements. In a companion paper, signal attenuation results considering the effects of various parameters are analyzed.

A previous paper has been written on the generalized modeling method of overhead transmission lines for use in power-line carrier (PLC) systems. Knowledge of the effects of shield wires on PLC signal attenuation for various coupling methods would be useful to relay engineers. In addition to the effect of the coupling method on PLC signal attenuation, other problems, such as resonance conditions resulting in high signal attenuation may also occur depending on the PLC signal frequency and the length of the shield wire segments. Therefore, the purpose of this paper is to provide awareness to relay engineers of problems that may arise when applying PLC systems on transmission lines with segmented shield wires.

The main purpose of this series of papers is to provide methodology and best business practices to assess the risk posed by geomagnetic disturbances. This paper addresses the methodology used by Dominion Virginia Power to model geomagnetically induced currents. An extreme 100-year geoelectric-field scenario is utilized as a baseline. The impact of topology changes in a large 497-bus system is investigated. Subsequent papers-Parts II and III-will address transformer vulnerability and system voltage stability, respectively.

International audience; Broadband power-line communication (PLC) technologies are one of the main parameters of digital convergence voice-data-video in the home environment. These technologies use the power-line network as a propagation and a communication medium. Its transmission quality depends on the frequency behavior of the propagation medium and the connected household electrical appliances. The impedance of those devices and noise levels has a great impact on the PLC systems. In this paper, a simulator for indoor power-line channels is presented. In this paper, a new approach is presented for modeling temporal variations of noise and channel on indoor power lines. A three-conductor power cable (phase, neutral, and ground) is modeled by a circuit of four elements (resistor R, inductor L, capacitance C, conductance G). The RLCG parameters are deduced from the impedance measurement in open circuit and in short circuit. The cable model is validated in time and frequency domains. Then, the temporal variation of periodic noise is modeled by a stochastic approach. The global model, combining both channel and noise variations, is validated by comparing SPICE simulation and measurement results.

This paper aims at developing a simulation method for the ion-flow field when HVDC transmission lines cross over HVAC transmission lines. A time-domain 3-D method is proposed in this paper, where the 3-D finite-element method and 3-D finite volume method are used to solve the Poisson's equation and the charge conservation law, respectively. The implicit temporal discretization scheme is used to accelerate the computation. An indoor test model is set up in this work, and the simulation results agree well with the measured results from this test model, which validates the proposed method. The proposed method is then used to calculate the ground-level electric field and ion current density under the crossing of ± 800-kV HVDC transmission lines and 500-kV HVAC transmission lines. The presence of HVAC transmission lines is found to have a significant influence on the ion-flow field under the crossing.

The conventional interphase power controller (IPC) can control the power flow of the transmission line. In this paper, a novel topology for IPC, called the unified interphase power controller (UIPC), is introduced. In this topology, the phase-shifting transformers (PSTs) are replaced by voltage-source converters. In this paper, the transient behavior of UIPC is modeled and investigated. The results are compared with the simulation results of IPC and UPFC. It is shown that UIPC has all of the capabilities of IPC and UPFC, such as power-flow control, fault current limitation, voltage isolation, and local bus voltage regulation simultaneously. The results also reveal that UIPC increases the variations range of control variables of IPC and, as a result, the range of variations of active and reactive powers.

In this paper, some useful features are extracted from voltage signals measured at one terminal of the transmission line, which are highly efficient for accurate fault locating. These features are the amplitude of harmonic components, which are extracted after fault inception through applying discrete Fourier transform on one cycle of three-phase voltage signals and then are normalized by a transformation. In this paper, the location of single-line-to-ground faults as the most probable type of fault in the transmission networks is considered. The SLG fault locator, which is designed based on the simple algorithm of k-nearest neighbor (k-NN) in regression mode, estimates the location of fault related to the new input pattern based on existing available patterns. The proposed approach only needs the measured data from one terminal; hence, data communication between both ends of the line and synchronization are not required. In addition, current signals are not used; therefore, the proposed approach is immune against current-transformer saturation and its related errors. Tests conducted on an untransposed transmission line indicate that the proposed fault locator has accurate performance despite simultaneous changes in fault location, fault inception angle, fault resistance, and magnitude and direction of load current.

Performance of the conventional ground distance relaying scheme is adversely affected by different types of ground faults, such as single line to ground, double line to ground, and simultaneous open conductor and ground. This effect is more pronounced due to the considerable value of fault resistance and direction and magnitude of power flow. The work presented in this paper addresses the aforementioned problems encountered by the conventional ground distance relaying scheme when protecting doubly fed transmission lines. Further, a new digital distance relaying scheme is proposed which compensates the errors produced by the conventional ground distance relaying scheme using local-end data only. The detailed analysis of the apparent impedance as seen from the relaying point by the conventional ground distance relaying scheme and the proposed scheme during different types of ground faults is also presented in this paper. The feasibility of the proposed scheme has been tested using MATLAB/SIMULINK software. The simulation results demonstrate the effectiveness of the proposed scheme since it provides accuracy on the order of 98%.

This paper presents a brief review of techniques available for reducing large systems to smaller equivalents. This paper is divided into high frequency equivalents, low frequency equivalents, and wideband equivalents. Numerical examples are presented to demonstrate selected methods of high frequency equivalencing.

A novel apparatus based on variable inductors to control the insertion compensating voltage of the transmission line is proposed in this paper. The apparatus can change the alternative voltage into the desired alternative voltage directly by using the control strategy proposed in this paper and insert the voltage into the line. Since the amplitude and the phase angle of the voltage supplied by the apparatus can be adjusted continuously and independently, the apparatus can control the real- and reactive- power flow independently and realize the direct voltage regulation (DVR) and the phase angle regulation (PAR) of the transmission line. The control methods suited for the proposed apparatus about the independent control of real and reactive power flow in the transmission line and the DVR and the PAR are also proposed. The control strategy and methods are verified with experimental results and simulation results.

This paper presents a new approach for locating short-circuit faults on a double-circuit transmission line. Various algorithms have been proposed previously that usually require measurements recorded from one or two buses of the faulted line. However, such measurements may not always be available in some scenarios, rendering inapplicability of existing methods. To complement existing methods, this paper proposes a novel, general fault-location method by harnessing voltage measurements at one or more buses, which may not be taken from the faulted line. The bus impedance matrix of each sequence network with the addition of a fictitious bus at the fault point can be derived as a function of the fault location. The fault location can then be obtained based on the bus impedance matrix and voltage measurements. The distributed parameter line model is utilized. The network data are assumed to be available so that the bus impedance matrix can be constructed. When multiple voltage measurements are available, an optimal estimator capable of identifying bad measurement data is also proposed for enhanced fault location. Since field data are not available at this time, simulated data are utilized for evaluation studies, and quite accurate results have been achieved.

Sharing the same corridor of the HVAC and HVDC transmission lines can efficiently increase the power transfer capacity of the limited corridor and will be erected in East China. An accurate and efficient numerical analysis method for analyzing the ion-flow field of the ac-dc hybrid lines is helpful for engineering design. In this paper, an upwind finite volume-based algorithm for the solution of the ac-dc hybrid ion-flow field is proposed, which can take the influence of the space charges generated by corona into account. The electric field is solved by the charge simulation method and the finite-element method, while the advection and recombination effects of the space charges are solved by a time-dependent finite volume method. The reduced-scale ac-dc hybrid models are analyzed and the calculating results by the proposed approach in this paper have good agreements with the experimental ones in the literature and in this paper. Finally, the ground-level electric field and ion current density of the hybrid UHVAC and UHVDC transmission lines in parallel are analyzed, providing a reference for the engineering design.

This paper introduces a new noniterative fault-location algorithm for long transmission lines compensated by a series flexible ac transmission systems (FACTS) device. In the proposed algorithm, synchronous voltage and current samples from both ends of the transmission line are used and the distributed parameter line model in the time domain is applied. Due to the difficulties in the modeling of the series FACTS devices during a fault, the presented method does not use the model of the series devices. In this paper, the fault-location problem is converted to an optimization one in which the location and resistance of the fault are the decision variables. The proposed method includes three stages. Two fault locations are obtained, corresponding to the first two stages. In stage three, the obtained results from stages 1 and 2 are compared, and the correct fault location is selected. The proposed algorithm is a noniterative one and it is suitable for transmission lines compensated by any series FACTS device which could have the overvoltage protection and can be in any operating mode. The performance of the proposed algorithm is evaluated under different structural and fault conditions. The simulation results confirm the accuracy of the proposed algorithm.

Aeolian vibrations of power lines are induced by Von Karman vortex shedding. Without dampers, the amplitude of vibration very much depends on conductor self damping, which may be very low. The purpose of this paper is to show measurements of these vibrations carried out by a new experimental device which is able to perform continuous measurements in the full range of frequencies and amplitudes. In this paper, 550 h of continuous recording on four different conductors placed in similar conditions is detailed. An evaluation of self damping power, based on observations, is proposed.

This paper presents a solution for bulk ac power transmission over extra long distance based on an unconventional transmission line that is little longer than a half wavelength (λ/ 2+). This solution is very convenient to be applied in countries where the generation sites are very distant from the consumption centers. However, it has some restrictions regarding feeding loads at intermediate points. To overcome this drawback, an HVAC tap based on power-electronics converters is proposed. This tap allows feeding local loads as well as integrating power plants to the main circuit without changing the transmission system's electrical characteristic. This paper also presents an application example of a λ/ 2+ line with an HVAC tap draining and injecting energy from the line.

In this paper, a new concept of passive-loop technique called the “high magnetic coupling passive loop” is presented. The proposed shielding technique is characterized by high performances and takes all of the advantages of passive and active shields. The shielding technique can be adopted in different application fields: power lines, line transformer connections, etc. In this paper, the proposed shielding is deeply analyzed. The working principle will be explained and validated by means of simulations and laboratory measurements on some prototypes. Finally, the actual performances of the shield installed on a high-voltage power line are presented, discussed, and compared with the result obtained by means of classical passive loops.

Included angle selection for a V-shape insulator string applied in 750-kV compact transmission line is studied in this paper. The mechanical performance of V-shape insulator string is demonstrated from calculation and experiment. A new solution, which is based on the finite-element method and applied to calculate the deformation of V-string, is presented. This paper discusses the relation between deformation (displacements and force) and load on V-string. Loading experiment for V-string is conducted in order to verify the calculation results. Experimental data of displacements for V-shape composite and porcelain insulator string are obtained. Finally, combined with the calculation and experiment results, the selection of included angle for V-shape insulator string is discussed, and recommendations for the included angle value of V-shape insulator string in 750-kV compact transmission line are made.

This paper presents a flexible ac transmission system device under development for the management of power flow under steady-state and dynamic conditions, the bundle-controlled line-impedance modulator (LIM). In its simplest form, an LIM is made of switching modules connected in series with transmission-line segments whose bundles have subconductors insulated from each other. A module contains one switch in series with each subconductor of a bundle and the modules are anchored to dead-end towers in place of yoke plates. Together, with the measurement of sensors and controls, these modules can be used to change series impedances of transmission lines and implement functions, such as deicing, power-flow control, stability control, and line monitoring. In order to illustrate the LIM capabilities, two load-flow studies and one stability study are presented in this paper. Finally, the LIM performance is qualitatively compared to the thyristor-controlled series compensator technology.

The use of metal-oxide varistor surge arresters (MOVs) in lightning protection of overhead transmission lines to improve reliability is of great interest to electric utilities. However due to economic reasons, it is not possible to completely equip an overhead transmission line with surge arresters at each transmission structure. In this paper, an evaluation of lightning protection design on a 115 kV transmission line using surge arresters, utilizing a model based on field data, is presented. The model developed is used for computer simulation using the Alternative Transients Program. Various design procedures aimed at maximizing the reliability of service on the transmission line using a minimal number of surge arresters are analyzed. Different designs considered for transmission line lightning protection using MOV arresters include: the use of a different number of surge arresters per tower, distance between towers with surge arresters and the dependence of these configurations on tower footing resistance. The lightning protection designs are analyzed using `lightning flashover charts,' proposed in this paper. Also, an analytical model of two 115 kV transmission lines in Southwest U.S. has been developed and different surge arrester location strategies used on these transmission lines have been analyzed. Practical experiences and effectiveness of various lightning protection designs used on these transmission lines are discussed.

This paper describes a new algorithm to calculate the per phase impedance between the measurement and fault points on a transmission line, featuring robustness to the uncertainties in load current and fault path resistance. The algorithm, which is ideal for distance relaying, is derived based on a justifiable assumption of the fault path being purely resistive, implying that the unmeasured fault point voltage and fault path current are in phase with each other. This paper illustrates the characteristics of the proposed algorithm and evaluates its performance by using PSCAD/EMTDC simulation.

This paper investigates the economical feasibility of four-phase (4P) overhead transmission lines, considered as a possible alternative to the traditional three-phase (3P) connections. The paper performs an economical comparison between innovative 4P transmission lines and traditional 3P lines, with the goal of evaluating the contests where a 4P connection could become con-venient, accounting for different reliability, land occupation, vis-ual impact, energy losses and investment costs.

This paper presents the results of a study on the use of modal analysis for estimating received signal levels of a power-line carrier (PLC) channel on high voltage transmission lines. The intent of the paper is to serve as a reference. Numerous papers have been written on modal analysis and signal propagation on overhead lines at PLC frequencies. However, for the information to be put to practical use requires reading numerous references, including references on transmission line modeling. Therefore, this paper provides information on transmission line modeling and modal analysis theory needed for using modal analysis for an actual calculation of received signal levels with results in the phase domain, which is the domain in which measurements are usually made. Modal analysis is used to calculate modal propagation constants, which are used in an equation that directly relates sending-end voltage to receiving-end voltage utilizing a multiphase reflection coefficient. To validate calculations using the described methods, field tests were performed on an energized 500-kV transmission line. Results from these tests in the form of a comparison of calculated versus measured voltage levels are provided.