Extra High Voltage Transmission Lines Research Articles

Laboratory investigation of AC corona loss and corona onset voltage on a conductor under icing conditions

Corona losses generated from energized conductors, especially in foul weather conditions, is one of the most important economic factors influencing the design of extra-high voltage (EHV) and ultra-high voltage (UHV) transmission lines. In the present paper, results of laboratory experiments under icing conditions are presented. Two types of ice are considered: rime and glaze. The conditions of ice formation on the test conductor are presented. During the ice accretion, an electric field was applied to the conductor to investigate corona loss and corona onset voltage. The presence of glaze results in a higher corona loss and a lower corona onset voltage compared with rime. The influence of wind velocity and freezing water conductivity were also studied. The test results can help to estimate corona losses of transmission lines in cold climate regions and to improve the design of transmission lines.

Modeling and Simulation of Electrical Resonance in EHV Transmission Line Case Study in West Java Region 500 kV System

Electrical transmission line can be approached by the second order system with the model of capacitive, inductive, and resistive elements. In the system, the capacitive element is represented by the capacitance value between phases and phase to ground. In the other side, inductance of reactor and phase conductor represent the inductance element, whereas resistance of the phase conductor represents the resistance value of the system. As a second order system, the electrical transmission line is potentially experiencing the resonance phenomena if the natural frequency reaches the 50 Hz operation frequency. This paper explains the study of resonance phenomena in Extra High Voltage (EHV) 500 kV transmission line between two 500 kV Substation in West Java Region by the modeling and simulation. The results show that the transmission line is very vulnerable to the resonance phenomenon which is indicated by the existence of voltage up to 800 kV when this transmission line is not yet energized and causing one of the line arrester broken. The results also show that under the resonance phenomena, single pole auto reclose process is potentially failed. This study is expected to increase the concern for the resonance phenomena in the transmission lines.

Pattern Recognition Application of Support Vector Machine for Fault Classification of Thyristor Controlled Series Compensated Transmission Lines

Application of series compensation in extra high voltage (EHV) transmission line makes the protection job difficult for engineers, due to alteration in system parameters and measurements. The problem amplifies with inclusion of electronically controlled compensation like thyristor controlled series compensation (TCSC) as it produce harmonics and rapid change in system parameters during fault associated with TCSC control. This paper presents a pattern recognition based fault type identification approach with support vector machine. The scheme uses only half cycle post fault data of three phase currents to accomplish the task. The change in current signal features during fault has been considered as discriminatory measure. The developed scheme in this paper is tested over a large set of fault data with variation in system and fault parameters. These fault cases have been generated with PSCAD/EMTDC on a 400 kV, 300 km transmission line model. The developed algorithm has proved better for implementation on TCSC compensated line with its improved accuracy and speed.

System-Based Safety Tenets Applied to the Extra-High Voltage Transmission Line Design for Common Uses of Highway Right-of-Way

The rapidly increasing demand for electricity in recent years resulted in increasing needs of electrical system capacity and deployment for alternate uses of highway right-of-way (ROW) for the purpose of electric power generation, transmission, and distribution. In this framework, a systems approach—fundamental principles of system dynamics for identifying, understanding, and analyzing safety requirements of the extra-high voltage power line (EHV)—is used to objectively focus on two main safety issues related to the design and the risk of the EHV transmission line within highway ROW: (1) assess the design and the operation, and (2) evaluate causally related impacts on the public and workers’ safety that matter. A generalized model of the electromagnetic fields distribution and the clearance model are developed for the analysis of the causally related impacts of a conceptual design and the reliability of materials of construction of the electric systems by introducing the number of exposed individuals and the level of the environmental impacts as a second dimension in addition to the risk factors. A worst-case design scenario is evaluated. Sensitivity analysis of effects of the design attributes such as the route configuration, over voltages, and conductor clearance is performed by determining the magnitude of the electromagnetic field strengths and predicting the resulting maximum voltage. Information obtained on the structural design scenario, conductor size and configuration, insulators, and connectors is of value in determining the safety of the design for operation at extra-high voltages within highway ROW.

Secondary Arc Current Analysis of an Untransposed EHV/UHV Transmission Line With Controllable Unbalanced Shunt Reactor

A conventional four-legged shunt reactor serving untransposed extra-high voltage or ultra-high voltage transmission lines may cause the secondary arc difficult to extinguish and result in single-phase autoreclosing (SPAR) failure. This paper proposed an unbalanced shunt reactor (USR) scheme and focuses on the secondary current analysis with respect to untransposed extra high-voltage/ultra-high voltage transmission lines. The fundamental theory of secondary arc calculation for the untransposed transmission line with USR was provided first, followed by the formulation of USR controlling principles and strategy. To validate the effectiveness of secondary arc current suppression, untransposed 1000-kV single-circuit and double-circuit UTL with USR were simulated using the Electromagnetic Transients Program. The results show that USR is effective in suppressing secondary arc current and recovery voltage for single-circuit and double-circuit UTL, which helps increase the SPAR success probability. Furthermore, the secondary arc current and recovery voltage are not sensitive to the variation of USR neutral reactance; hence, the value of neutral reactance can be decided in a wide range. Finally, USR’s role and effect in reducing the inductive electrostatic voltage in double-circuit UTL was discussed when one line is transferred to maintenance.

A novel summation impedance protection adaptive to high‐resistance earth fault detection

While the high‐resistance earth fault frequently occurs on extra high voltage (EHV) transmission lines, existing protection schemes show great limitation for coping with this kind of fault scenario when the fault resistance is very high. In this paper, a novel protection methodology combining the measured impedance of the two ends is introduced, and a so‐called summation impedance protection, making use of this critical information, is thus put forward and assessed. Emphasis is placed on the principle of the summation impedance protection and its adaptive thresholds. A simulation model based on EMTDC/PSCAD, by which the performance of the summation impedance protection is evaluated, is then established. As confirmed by quantitative theoretical and experimental studies, the results indicate that the proposed protection scheme works well even when the fault resistance is extremely high under the internal fault condition, and it keeps itself from maloperation as an effect of its adaptive thresholds wherever an external fault occurs. These results highlight the necessity to work in conjunction with the existing main protections of transmission lines, by which means an enhanced ability to cope with the high‐resistance single‐phase earth fault can be achieved. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Damaging Open-Phase Overvoltage Disturbance on a Shunt-Compensated 500-kV Line Initiated by Unintended Trip

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.

Transforming the electricity generation of the Berlin–Brandenburg region, Germany

We present possible steps for Germany's capital region for a pathway towards high-level renewable energy contributions. To this end, we give an overview of the current energy policy and status of electricity generation and demand of two federal states: the capital city Berlin and the surrounding state of Brandenburg. In a second step we present alternative, feasible scenarios with focus on the years 2020 and 2030. All scenarios were numerically evaluated in hourly time steps using a cost optimisation approach. The required installed capacities in an 80% renewables scenario in the year 2020 consist of 8.8 GW wind energy, 4.8 GW photovoltaics, 0.4 GWel bioenergy, 0.6 GWel methanation and a gas storage capacity of 180 GWhth. In order to meet a renewable electricity share of 100% in 2030, approximately 9.5 GW wind energy, 10.2 GW photovoltaics and 0.4 GWel bioenergy will be needed, complemented by a methanation capacity of about 1.5 GWel and gas storage of about 530 GWhth. In 2030, an additional 11 GWhel of battery storage capacity will be required. Approximately 3 GW of thermal gas power plants will be necessary to cover the residual load in both scenarios. Furthermore, we studied the transmission capacities of extra-high voltage transmission lines in a second simulation and found them to be sufficient for the energy distribution within the investigated region.

A rough membership neural network approach for fault classification in transmission lines

Objective: This paper presents a new approach for fault classification in extra high voltage (EHV) transmission line using a rough membership neural network (RMNN) classifier.Methods: Wavelet transform is used for the decomposition of measured current signals and for extraction of ten significant time–frequency domain features (TFDF), as well as three distinctive time domain features (TDF) particularly in terms of getting better classification performance. After extracting useful features from the measured signals, a decision of fault type of a transmission line is carried out using ten RMNN classifiers. Furthermore, to reduce the training times of the neural network, the rough neurons are used as input layer neurons, and the fuzzy neurons are utilized in hidden and output layer in each RMNN. And the Back Propagation (BP) algorithm is employed for determining the optimal connection weights between neurons of the different layers in the RMNN.Results and Conclusions: To verify the effectiveness of the proposed scheme, extensive simulations have been carried out under different fault conditions with wide variations in fault type, fault resistance, fault location and fault inception angle. Simulations results show that the proposed scheme is faster and more accurate than the back-propagation neural network (BPNN), and it is proved to be a robust classifier for digital protection.

Real time digital simulator implementation of data-mining-based integrated impedance relay for compensated lines

Summary The paper presents integrated impedance-based intelligent relaying for thyristor-controlled series capacitor-compensated transmission lines on Real Time Digital Simulator platform. Integrated impedance is defined as the ratio of sum of the voltage phasors across two ends of the transmission line to the sum of the current phasors through two ends of the same transmission line. The imaginary part of integrated impedance of the transmission line is used as input to a data-mining model known as decision tree that determines whether the fault is within the protected zone or not. Critical issues such as power swing and fault during power swing are also included during validation of the relay on Real time digital simulator platform. The test results obtained indicate that the proposed integrated impedance-based intelligent relaying is highly dependable and secure for protection of extra high voltage transmission lines including thyristor-controlled series capacitor. Copyright © 2014 John Wiley & Sons, Ltd.

Research on Complex Gap Discharge Model of Live Working on EHV and UHV High-Voltage Transmission Lines

This paper obtained the switching impulse flashover characteristic of live working complex gap on extra high voltage (EHV) and ultra high voltage (UHV) high-voltage transmission lines by a large number of experiments. Based on the experimental data and the leader inception discharge model, the complex gap discharge development during the process of entering equipotential and its influencing factors have been analyzed with the electric filed calculation method. Moreover, considering the practical conditions in live working sites, a complex gap discharge model appropriate for side live working on EHV and UHV high-voltage transmission lines has been proposed by introducing a revision coefficient km. It has been found that km is related to the working position and the structure of high-voltage electrode. Through further research on the establishment of the functional relationship, it can provide a comparable accurate theoretical calculation method for the research on the complex gap of live working and can give a guideline for optimizing the test plans.

Accurate Fault Classifier and Locator for EHV Transmission Lines Based on Artificial Neural Networks

The ability to identify the fault type and to locate the fault in extra high voltage transmission lines is very important for the economic operation of modern power systems. Accurate algorithms for fault classification and location based on artificial neural network are suggested in this paper. Two fault classification algorithms are presented; the first one uses the single ANN approach and the second one uses the modular ANN approach. A comparative study of two classifiers is done in order to choose which ANN fault classifier structure leads to the best performance. Design and implementation of modular ANN-based fault locator are presented. Three fault locators are proposed and a comparative study of the three fault locators is carried out in order to determine which fault locator architecture leads to the accurate fault location. Instantaneous current and/or voltage samples were used as inputs to ANNs. For fault classification, only the pre-fault and post-fault samples of three-phase currents were used. For fault location, pre-fault and post-fault samples of three-phase currents and/or voltages were used. The proposed algorithms were evaluated under different fault scenarios. Studied simulation results which are presented confirm the effectiveness of the proposed algorithms.

Protection Scheme for Transmission Lines Based on Correlation Coefficients

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. A correlation technique is developed for faults detection and discrimination. The proposed technique is able to accurately identify the condition of phase(s) involved in all ten types of shunt faults that may occur in extra high-voltage transmission lines under different fault resistances, inception angle and loading levels. The proposed technique does not need any extra equipment as it depends only on the three line-currents measurements which are mostly available at the relay location. This technique is able to perform the fault detection, type and phase selection in about a half-cycle period. Thus, the proposed technique is well suited for implementation in digital protection schemes. The suggested scheme is applied for a part of 500 Kv Egyptian network. Alternative transient program (ATP) and MATLAB programs are used to implement the proposed technique.

Fault location for three-terminal transmission lines using fault voltage sequence components

ABSTRACTA new fault location algorithm for three-terminal high or extra-high voltage transmission lines is presented and validated. The algorithm is based on the transmission line model with lumped parameters considering the distributed capacitance of lines. Only the sequence component of fault voltage is used in fault location to avoid the influence of saturated current transformer. In location formulas, positive sequence components are used for symmetric faults and negative sequence components are used for non-symmetric faults. The schemes for the following three different conditions of three-terminal lines are discussed in detail: single-circuit line with T-connection networks, single-circuit line to double-circuit line with T-connection networks, double-circuit line with T-connection networks. A new faulted branch selection method is proposed. The hypothetical fault distance of each branch is calculated and compared to accurately determine which branch is faulty. ATP simulation indicates that the location precision is satisfied no matter the measurements are synchronised or unsynchronised at three terminals. A quantitative comparison with the other known algorithms reveals that the presented new algorithm has higher location accuracy and can judge fault branch more accurately.

Design on Synchronize Debugging Device for Extra High Voltage Transmission Line Longitudinal Protection

Because of time urgent before putting into operation and different place line protection equipment located, joint debugging for extra high voltage (EHV) transmission line is often not perfect although EHV transmission line is very important for modern grid. In joint debugging process, we tend to adopt static method to do fault simulation, that apply analogue to the device. To overcome the shortages of static fault simulation commonly used, which cannot accurately simulate fault characteristics in runtime, a synchronous joint debugging device is designed based on based on the analysis of the joint debugging process for line longitudinal protection. The device is a lightweight and low cost embedded system with the functions of communication and phase shift, and can offer analog signals to protection devices on both ends of the line. Based on the functions and characteristics of the synchronous joint debugging device, the joint debugging process with this device of optical fiber differential protection is analyzed. The functions of this synchronize testing device can meet the requirements, turning static to dynamic joint debugging.

Research on a novel suppressing methodology for secondary arc extinction based on an impedance paralleled to line circuit breaker

A novel scheme is proposed for secondary arc extinction, preferably applicable to extra high voltage (EHV) and ultra high voltage (UHV) transmission lines. The topology and the operational principle of the scheme are elucidated in details. Mathematical expressions for topology parameters design and optimization under different conditions have been established based on equivalent circuit transform and are verified by simulations. Results suggest that the proposed methodology can largely reduce the forced component of the secondary arc current, one part of the complete response of a circuit under excitation. The recovery voltage is not affected by fault location, transmission power and the shunt inductors. The decay factor and oscillation frequency of the free components of the secondary arc current and the recovery voltage are also computed based on the equivalent impedance network and Laplace Transform. In addition to causing possible resonant overvoltage, the proposed theme may prolong the arcing time due to cancelling zero-crossing of the secondary arc current while shunt inductors are installed at the transmission line terminals. Simplified formula for calculating the critical compensation point are given as to be used as a reference for the re-optimization of the novel theme. The proposed methodology presents an alternative to suppress the secondary arcs for EHV and UHV transmission lines. Copyright © 2013 John Wiley & Sons, Ltd.

Electric field mitigation under extra high voltage power lines

This paper deals with the mitigation of electric fields under extra high voltage transmission lines using active and passive shield wires. Two extra high voltage alternating current transmission lines are modeled and analyzed. One line is operating at 220 kV and the other is at 500 kV. The electric field is calculated at one meter above the ground level for the two transmission lines with and without active and passive shield wires using the charge simulation method (CSM). The effect of different shielding parameters on the ground level field is studied. These parameters include the spacing between shield wires and their number of these wires, and their height above ground as well as the value of the voltage applied to the shield wires. Also, the effects of passive and active shield wires on the magnetic field underneath the lines and the electric field on the conductor's surface are highlighted.

765 kV Transmission Line Design (Electrical Section)

Nowadays, due to the ever increasing energy consumption and power supply optimization, it is required to construct new power plants, substations and transmission lines. In Iran, also, because of increasing demand for electrical energy, for a significant power loss reduction in power transmission over long distances, and to construct high transmission lines that lead to reduction in the economic costs of transmission lines, the transmission lines must be considered at extra high voltage (EHV) levels. These EHV levels should be compared with the low voltage levels in order to extract the benefits. Therefore, in this paper, a review has been conducted on the types of 765 kV transmission lines used in different countries and a comparison between them and the low voltage levels have been performed. Accordingly, the advantages of EHV transmission lines are summarized. Finally, designing a line of 765 kV single-circuit with 6 conductors per bundle based on existing standards is presented. DOI: http://dx.doi.org/10.11591/ijece.v2i5.1591

Insulation design of cryogenic bushing for superconducting electric power applications

Recently, the superconductivity projects to develop commercial superconducting devices for extra high voltage transmission lines have been undergoing in many countries. One of the critical components to be developed for high voltage superconducting devices, including superconducting transformers, cables, and fault current limiters, is a high voltage bushing, to supply high current to devices without insulating difficulties, that is designed for cryogenic environments. Unfortunately, suitable bushings for HTS equipment were not fully developed for some cryogenic insulation issues. Such high voltage bushings would need to provide electrical insulation capabilities from room temperature to cryogenic temperatures.In this paper, design factors of cryogenic bushings were discussed and test results of specimen were introduced in detail. First, the dielectric strength of three kinds of metals has been measured with uniform and non-uniform electrodes by withstand voltage of impulse and AC breakdown test in LN2. Second, puncture breakdown voltage of glass fiber reinforced plastics (GFRPs) plates has been analyzed with non-uniform electrodes. Finally, creepage discharge voltages were measured according to the configuration of non-uniform and uniform electrode on the FRP plate. From the test results, we obtained the basic design factors of extra high voltage condenser bushing, which could be used in cryogenic environment.

Researches on Reactive Compensation for Long-Distance and Highcapacity Hybrid Submarine Cable Lines

In order to balance reactive power, reduce line losses, prevent excessive power frequency and switching over-voltage and adjust and control the line voltage etc. The long-distance and high voltage transmission lines are needed reactive power compensation. High voltage overhead transmission lines and high voltage submarine cable (including mixed-submarine) transmission lines are different, for example, the capacitance in the submarine cable lines is larger than in the conventional overhead lines. Therefore, the reactive power compensation on the EHV transmission lines which contains submarine cable lines is focus on the compensation of submarine cable lines. The reactive power compensation in 500 kV AC submarine cable interconnection project for Hainan power grid and Guangdong power grid[1], which is the first 500 kV long-distance and high-capacity sea trails interconnection project in China and which is just completed soon, is researched by Electro-Magnetic Transient Program——PSCAD/EMTDC (Power System Computer Aided Design/ Electro Magnetic Transient in DC System in this paper). The simulation results verifies that the role of shunt reactor which could absorb charging power and suppress the power frequency overvoltage for the long-distance and high-capacity hybrid submarine cable lines. The conclusions can offer references to suppress power frequency overvoltage and the reactive power compensation in extra high voltage transmission lines which is the mixed mode of overhead transmission lines and submarine cables.