UHV Transmission Lines Research Articles

An Electroscope System Based on Electric Field Measurement Method for UHV Transmission Lines

The paper describes an electric field measurement method based electroscope system to check the electrification state of ultra-high voltage transmission lines, which is composed of three parts: 1) Measuring terminal; 2) Central sever; 3) GPRS and Internet network. The measuring terminal was used to measure the electric field and the location of the measuring points, then the measured data was sent to the central sever by GPRS and Internet network, and requested for an electricity state confirmation.When the sever received a request from a terminal, the electric fields and locations of the measuring points were obtained first, then according to the location of the measuring points, the server searches the corresponding objective transmission lines in the database and read their parameters. According to the parameters of the measuring points and transmission lines, a calculation would be carried out to confirm the electrification state of the transmission lines. For the confirmation calculation, equations for the electric field inverse problem of the transmission lines were set up first, then global regularization and damped Gauss Newton (DGN) method were used to solve the inverse problem.A 500kV double loops transmission line was taken as an example to verify the validity of this method. The electric field and location of 11 measuring points were measured by the measuring terminal firstly, and then sent to the central sever. Electrification state was confirmed by the central sever.

A Distance Protection Relay for a 1000-kV UHV Transmission Line

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A traditional distance protection relay uses a lumped parameter model of the transmission line. For a long 1000-kV UHV line with large distributed capacitance, such a simplified line model is inadequate and can cause malfunction of the relay due to large errors in the impedance measurement. This paper presents a new line model for a distance relay and the procedure of reliable fault impedance measurement and relay setting. It describes the proposed application of the relay developed to a 645-km 1000-kV UHV transmission line including shunt reactor compensation, which is currently being constructed in China. Tests are carried out on an RTDS (real time dynamic system) to evaluate the relay performance, showing significant improvement compared to a more traditional distance relay. The new distance relay is shown to satisfy the requirement of 1000-kV UHV transmission line protection. </para>

A Current Differential Relay for a 1000-kV UHV Transmission Line

This paper describes the principle of a new current differential relay developed for a 1000-kV UHV transmission line that is being constructed in China. The distributed capacitive current along the relatively long overhead line will have a significant effect on the relay performance and should be taken into account in the relay principle. The study results in a new current differential relay based on the steady state transmission line equations, in which the distributed capacitive current is inherently represented. Analysis is carried out for different practical situations where shunt reactors or series capacitors are present in the system for compensation. Laboratory tests show that the relay principle developed in this study can be used as a main protection scheme for the 1000-kV UHV transmission line.

Simple Optimizing Method of Shunt Reactor Connected to Double Circuit UHV Transmission Line for Minimizing Maximum Secondary Arc Current

Simple Optimizing Method of Shunt Reactor Connected to Double Circuit UHV Transmission Line for Minimizing Maximum Secondary Arc Current

A Hybrid Algorithm for High Speed Transmission Line Protection

A common method used in UHV transmission line protection is based on impedance measurement technique. The fault detection speed of impedance protection schemes cannot be improved without sacrificing the relay reach limit. Protection algorithms based on fault generated transient signals have shown promising results in improving the speed, but these methods have inherent reliability problems. This paper examines how the fault generated transient information can be used to achieve fast fault detection speeds in a distance protection scheme while maintaining a high reliability level.

On controlled switching of high voltage unloaded transmission lines

The limitation of switching overvoltages on very high voltage transmission lines is traditionally carried out with the aid of circuit breakers — fitted with closing resistors. This widely used system has repeatedly shown itself to be highly efficient. Nevertheless, it is possible to envisage other methods, in particular, those giving control of the circuit breaker instant of closing. This paper examines the possibilities offered by controlled switching on UHV transmission lines and compares existing solutions. It takes into account the various network characteristics that may be encountered. It details the results in terms of overvoltage levels which could be attained, due to the performance of the circuit breaker. The paper also highlights the critical points relative to the application.

UHV設計送電線への雷撃現象の観測

UHV designed transmission lines have already been in operation at 500kV since 1992. UHV substation equipments have also been energized in the test yard since 1996. For rationalization in insulation design and cost reduction, it is important to evaluate the phenomena of lightning for the UHV designed transmission lines. Some studies to observe current waveshapes have been conducted before, but they were ones conducted on independent towers and do not provide many data in a large-current region. So, we have been observing lightning currents on 60 transmission towers (mainly 500kV lines) since 1994. On UHV-class transmission lines with sections of 500kV-class insulation, lightning observations have been made to study the generation and the propagation of overvoltages into substations. Voltages and currents were recorded at the substations and at junction-tower footings on the UHV system. This paper describes the study of lightning phenomena and EMTP calculations on the UHV transmission lines.

Unbalanced power flow calculation of a power system containing a variable-speed generator

There are some factors that render a power system network unbalanced: UHV transmission lines in which three-phase transmission lines are not transposed, an unbalanced transformer, unbalanced load as well as sustained unbalanced faults. On the other hand, the number of variable-speed generators used in pumping-up power stations has recently been increasing in Japan. This paper presents a new means of calculating unbalanced power flow of a power system which contains variable-speed pumping-up generators. This new technique is based on the phase coordinate method, because a power system which has elements of unsymmetrical impedance can easily be analyzed by using it. In this paper, phase coordinate models of the variable-speed generator and its secondary exciting circuit, composed of a GTO converter/inverter, are analyzed first. Procedures of power flow calculation of unbalanced power systems follow. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 34–43, 2001

Experimental study on the prediction of hum noise from conductor bundles for UHV transmission lines

The audible noise produced by corona discharge from transmission line conductors comprises two major components, namely hum noise and random noise. Hum noise has a frequency that is twice the power line frequency and is generated primarily in rain, fog, and highly humid environments. It is one of the major factors affecting the design of conductor transmission lines for voltages above 500 kV, and it is very important to predict the level of hum noise near transmission lines. In this paper, using a comparison between measured values in the UHV Akagi test line and that using corona cage, an experimental prediction method of hum noise in rain condition is proposed. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 27–36, 1998

96/03902 Mapping a course for industrial lighting

Chapter 5 studies lightning protection and its computation and protective measures of UHV transmission lines, substations, and converter stations on the basis of analysis of the formation mechanism of lightning overvoltage. It innovatively puts forward the comprehensive measures of integrated optimization of the ground wire protection angle, design of the ground wire at the line feed segment, and substation lightning arrester configuration, thus significantly reducing lightning lateral strike or counterstrike probability and effectively suppressing the lightning overvoltage amplitudes to ensure the safety of equipment.

Insulation recovery time after fault arc interruption for rapid auto-reclosing on UHV (1000 kV class) transmission lines

The insulation recovery time after arc interruption must be known in order to select an adequate reclosing dead time of rapid auto-reclosing on transmission lines. The flashover probability of the insulation recovery voltage obtained from the insulation recovery tests using full size insulator assemblies was calculated. The insulation recovery time at the fault point for rapid auto-reclosing on UHV (1000 kV class) transmission lines was estimated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Behavior of post arc gas after arc interruption on UHV (1000 kV class) transmission lines

It is very important to know the insulation recovery time after arc interruption for selecting the adequate reclosing dead time of rapid auto-reclosing on transmission lines. In order to study insulation recovery characteristics after arc interruption on UHV (1000 kV class) transmission lines, many tests were carried out. Full size insulator assemblies were used for measurements of insulation recovery characteristics after arc interruption, and the behavior of post arc gases, which strongly influence the insulation recovery characteristics, was investigated. In this paper the authors describe the behavior of post arc gases after arc interruption of UHV transmission lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A study on a coreless superconducting transformer

A conceptual design for a 1000-MVA-class coreless superconducting autotransformer (CLSCAT) has been developed. For a preliminary experimental study, a small 2.5-kVA CLSCAT has been manufactured and tested. The test result shows that though the exciting current of the CLSCAT is very large, its voltage drop is relatively small compared with the cored transformer. The dielectric strength of liquid helium has been tested using an insulation model. From the insulation test, the availability of the fundamental insulation structure composed of the lamination of small liquid helium gaps separated by solid barriers has been confirmed. From the conceptual design of a 1000-MVA-class CLSCAT, it becomes clear that the CLSCAT has an additional reactive power of about one-third of its rated capacity. This large reactive power can be utilized for the compensation of the capacitive charging current of a cable line or a UHV transmission line. The operating loss, was calculated to be about two-thirds of the conventional transformer. However, this figure is reduced to one-half if the additional reactive power of the CLSCAT is considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Insulation recovery characteristics after fault arc interruption on UHV (1000 kV class) transmission lines

The insulation recovery time after arc interruption must be known to select the adequate reclosing dead time of rapid auto-reclosing on transmission lines. In order to study insulation recovery characteristics after arc interruption on UHV (1000 kV class) transmission lines, many tests were carried out using the high power test facilities of CRIEPI. In this paper the authors describe the experimental results of these tests of insulation recovery characteristics after arc interruption of UHV transmission lines, and some factors influencing these characteristics. >

A microprocessor-based quadrilateral distance relay for [formula omitted] transmission line protection

This paper presents an Intel 8086 microprocessor-based quadrilateral distance relay suitable for the protection of EHV UHV transmission lines. The digital filtering algorithm used for extracting the fundamental frequency components from the complex post-fault relaying signals is based on rationalized Haar transform (RHT). The real and reactive components (R and X) of the apparent impedance of the line as seen by the relay are computed by using the real and imaginary components of the fundamental frequency voltage and current phasors. Using the computed values of R and X, the microprocessor examines whether the fault point lies within the quadrilateral relay's protective zone or not. If the fault point lies in the protective zone of the relay, the microprocessor issues a trip signal to the circuit breaker. The proposed distance relay is reliable, flexible, accurate and fast.

A new Kalman filter approach to digital relaying

A novel Kalman filter approach to digital relaying is presented, in which the traditional application of simple, low-cost analog prefilters is assumed. The sampling rate is not directly coupled to the filter bandwidth; while this one was specified as low (150 Hz at maximum), the sampling period was determined by time resolution and processing cost requirements (1 kHz). To cope with the signal distortion resulting from the prefilters' own transients, a novel observation model is developed for the Kalman filter, with very little extra processing. The coloring effect on the observation noise by prefiltering is modeled in the Kalman filter state space, assuming white input noise, but the simulation tests with a modal-based impedance estimator show that little improvement is achieved with that. Instead, the addition of a colored time-decaying sinusoid to observation white noise in the state space supports improved performances, especially for very noisy faults in long UHV transmission lines with weak sending buses. Time decisions between 1/3 and 1/2 cycle were achieved for faults at the ending bus and at mid-line, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multistory transmission tower model for lightning surge analysis

A multistory transmission tower model to be used in multiconductor analysis by EMTP (Electromagnetic Transients Program) is proposed. The circuit parameters of the model are determined based on the measurement of voltages across the insulator strings on an actual 500 kV transmission tower. The multiconductor lightning surge analysis considered enables one to predict the waveform of each insulator voltage, which is useful in determining the phase and the instant of a back flashover. The new tower model is recommended in Japan to be used in the new multiconductor analysis of EHV and UHV class double circuit transmission lines. The new tower model and conventional tower models are compared in the analysis of minimum back flashover lightning currents at a UHV transmission line. The new model gives about 20% smaller current. >

Practical design of AC 1000 kV insulator assemblies

The design features of the arc horn applied to the insulator assemblies for AC UHV transmission lines are described. These features have been developed on the basis of detailed studies conducted on the corona characteristics and insulating performance. Since the characteristics of the arc horn for the UHV-class insulator assemblies can not be predicted by the extrapolation of the design practice for those of a 500 kV class, the design features have been validated by full-scale tests. A practical design of the arc horn applicable to AC 1000 kV transmission-line insulator assemblies were obtained by making the most use of such effects as the corona shield effect of the conductor and the effect of the electrode configuration on the switching impulse flashover voltage characteristics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of Parameters on The Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Effects of Parameters on The Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Effects of Parameters on the Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Phase-to-phase flashover characteristics needed for insulation design of UHV transmission lines, such as between 8-conductor to 8-conductors configuration and between the jumper line to the lower shield ring were investigated. The results include: (1) Effect of wave front duration of applied voltage. (2) Effect of positive-to-negative voltage ratio. (αm) (3) Effect of time difference between wave peaks of positive and negative voltages. (4) Gap distance characteristics of flashover voltage.