Reliability Of Transmission Lines Research Articles

On damage rate of overhead power transmission lines in power supply systems

The purpose of the article is to analyze the damage rate of overhead power transmission lines (OPL) in medium-voltage electrical distribution networks of the Irkutsk region. The established International Indices that determine the level of reliability of the functioning of electric networks are considered, and information on the compliance of the condition of electric networks in Russia with these indices is analyzed. Analytical information on the damage rate of elements of these networks and their causes in Europe, America, and Russia is presented. The emphasis is placed on the fact that the most common damage is characteristic of overhead power lines, especially 6–10 kV lines. As an object of research, two branches of the Irkutsk electric grid company (IEC) were taken, one of which provides electricity to rural consumers, the other — mainly to consumers residing in the territory of the city Irkutsk. The characteristics of these electric networks, their territorial location and basic technical data are presented. To conduct analytical monitoring of the level of reliability of overhead power transmission lines, logs of disconnection of the Eastern and Southern electric networks of the IEC over a long-term period were used. On the basis of this information, tables of failures and their consequences in the studied electrical networks were compiled for monthly average data over the period under examination for various causes of damage. To plot time diagrams of the parameters under examination, computer programs were compiled in the Matlab system, the use of which made it possible to obtain visualization of changes in failures for various reasons for the electrical networks under consideration. The information on the time of power supply interruptions in these networks, as well as the amount of electricity underutilized by consumers during these interruptions and its cost are analyzed. It is shown that in the electric networks under consideration, most of the power failures are related to the territorial dispersion of these networks, and the low level of equipment controls and insufficient qualification of operating personnel, as evidenced by the significant number of failures for unknown reasons. Besides, a significant part of the failures is due to damage to the overhead line wires, switching equipment and the effect of wind load. Recommendations for improving the condition of power transmission lines and a number of measures aimed at improving the level of reliability of power supply are presented.

Prediction of The High Voltage Insulators Service Life Based on The Effective Values of Leakage Currents

The insulation condition of overhead lines is one of the main factors affecting reliability of overhead power transmission lines. It is known that the process of insulation lapping or rupture is mainly affected by environmental conditions and the degree of pollution of the insulators surface. This paper substantiates the possibility of using the leakage current values of insulators for monitoring the state of insulation and predicting its resource. The results of experimental studies of leakage currents of high-voltage insulators depending on their service life are given, on the basis of which forecasting the possible resource of insulators is carried out. The results obtained can be used to develop more effective diagnostics for detecting insulator failures at an early stage to take appropriate measures to coordinate the insulation.

Transient switching analysis of a nonconventional rural generation system

This paper introduces a nonconventional rural generation system that extracts energy from high-voltage transmission line surroundings. The system was designed for a 230-kV transmission line and consists of a special 20-km collector line and an innovative substation. The energy is coupled to the collector line and supplied through a resonant circuit. There is no physical contact with the transmission line. A detailed electromagnetic study is described, assuring there is no disturbance at the transmission line and that the rural system delivers high-quality energy. Spark gaps were used to avoid overvoltage along the rural feeder. Transmission line reliability is not compromised.

Words high-frequency drying processes simulation of wooden tangent towers in a vacuum chamber

THE PURPOSE. The service life duration of wooden tangent towers used on overhead transmission lines with a voltage of up to 35 kV depends on the quality of lumber drying and subsequent impregnation. The drying of tangent tower workpieces is currently carried out by atmospheric or convective methods and is the longest and one of the energy-consuming stages of their production. At the same time, there are promising electrotechnological drying installations that can reduce the duration and improve drying quality at comparable specific energy costs. Such installations include vacuum high-frequency complexes, the wide introduction of which is complicated by a number of unresolved scientific and technical problems like optimizing vacuum high-frequency drying modes and ensuring electromagnetic field uniformity in long workpieces. The purpose of this article is to obtain mathematical tools that simultaneously describe the cross-effects of electromagnetic phenomena and heat and mass transfer processes in long-sized lumber and contribute to the further solution of these problems. METHODS. The positions of the theory of electromagnetic field, heat mass transfer and heat mass exchange, methods of mathematical modeling were used for this purpose. Also the results of previous studies of electromagnetic field distribution in the cross-section and longitudinal sections of the working chamber loading are taken into account. RESULTS. А one-dimensional mathematical model is obtained. It describes the influence of electromagnetic wave distribution along the length of tangent towers and external medium parameters on the temperature and moisture content in the material. This model is characterized by the possibility of using simple algorithms for analyzing differential equation systems based on the finite differe nce method and requiring less initial data on the drying material properties. CONCLUSION. The obtained by using the proposed model and the method of its analysis the numerical study results are compared with the available experimental data. Based on this comparison it is concluded that the obtained model is adequate and more effective relative to other existing models of vacuum high-frequency drying. Generally, further use of the presented mathematical toolkit to optimize the design and modes of vacuum-high-frequency complexes in the task of drying wooden tangent towers will increase the reliability of overhead transmission lines.

Research on the decision of state maintenance for transmission line based on set pair analysis

Overhead transmission lines are important parts of a power system; their operation state directly affects the reliability level of the entire power system. With the in-depth development of state maintenance work for power grids, correctly evaluating the reliability of overhead transmission lines is the key to successful maintenance. A maintenance decision model for transmission lines is established in this study based on set pair analysis to achieve human financial control and low maintenance efficiency. Full consideration is provided to the influence of environmental factors, and a theoretical basis for transmission line maintenance decision is established.

A Multi-dimensional Analysis Method for the Tripping Risk of Lightning Winding Across the Transmission Line

Trip to cope with the lightning strike caused around power grid, this paper proposed a transmission line based on the mechanism of lightning strike around all lightning strike tripping around risk analysis method. This method needed to detour lightning tripping thunderstorms and risk analysis of transmission lines tower size, proportion of topography, altitude, insulation configuration data were collected, calculated in turn hit distance, distance and exposure correction of line pressure level and single-base tower above factors lightning strike risk. Based on the calculation model, the lightning wind characteristics under different tower shout height, lightning day and terrain were studied to identify the weak links along the line. Select the composition condition calculation of typical tower lightning strike tripping around risk, based on the same area across the terrain and tower usage of extract weight coefficient calculation all lightning strike tripping around risk, through the typical combination of the weighted average of all lightning strike tripping around risk was analyzed. Through the example analysis, verified the feasibility of this method to improve the reliability of transmission lines.

Reintegration-based controlled islanding considering fast and slow active/reactive corrective actions to enhance frequency and transient voltage stabilities

In this paper, a reintegration-based multi-objective intentional controlled islanding (ICI) model is proposed to enhance resiliency of electrical power systems under catastrophic events. This remedial measure plan relies on a mixed-integer linear programming model with two objective functions including reintegration risk and total load shedding value. While ensuring that each island includes only coherent generators, the proposed multi-objective model solves the controlled islanding problem using lexicographic optimization approach. To ease the islands’ reintegration, charging reactive power, reliability, capacity, and power flow disruption of transmission lines are considered in the model. After implementation of controlled islanding, each resulted island may face temporary active/reactive load-generation imbalance, which may put the islands at the risk of frequency instability, transient voltage instability or a combination of both. The proposed model reduces these risks by modeling energy storage systems (ESSs) and static VAR compensators (SVCs) as fast corrective control actions. In addition to modeling voltage dependent loads in the controlled islanding problem, a linear island frequency response (IFR) model is proposed for frequency stability assessment. The test results of the proposed ICI model on the IEEE 39-bus and IEEE 118-bus test systems demonstrate its performance.

Lightning Performance of Unshielded 220kV Transmission Lines Equipped with Metal-oxide Arresters

Overhead ground wires have been proved to be effective to protect conductors from direct lightning strikes, but breakouts of ground wires have been frequently reported. In order to prevent ground wire breakout incidents to happen, unshielded 220kV lines equipped with metal oxide arresters (MOAs) whole line have been proposed in this paper. After cancelling ground wire, lightning strike risk of transmission lines becomes much higher. In order to improve the anti-lightning abilities of unshielded transmission lines, it is necessary to obtain the lightning energy absorption ability of these MOAs. In this paper, simulation model of MOA equipped unshielded 220kV transmission line was built, the influences of lightning parameters, striking occurrence point and grounding resistance of transmission tower on the absorbed energy of MOAs were calculated, and the suggested energy absorption ability of MOA was given, which can give references for the improvement of power supply reliability of transmission lines.

Properties Analysis of Dual IPCs 240 with Three Branches Case Study in an Energy Transmission Line Connected to a Hydroelectric Mini-Power Plant

In this paper, the newly developed “Dual Interphase Power Controller (IPC) 240” technology is used to increase the reliability of transmission lines for small renewable energy plants. This asymmetric compensation method based on symmetrical components has used two IPC. The first one is placed at the sending end of the line and the second IPC at the receiving end of the line. During normal operation of the transmission line formed, the electrical service continuity is ensured at the load using reactances, which adjust according to the power angle. When a permanent single-phase fault occurs, triggering the circuit breakers of the infected phase, the two IPCs are reconfigured so that the first performs a three-phase / two-phase transformation and the second a two-phase/three-phase transformation of voltage to continue providing a sufficient power for the load. Data from a power transmission line (30 kV-5 MW) from a mini hydroelectric power station has been used in a virtual network under Matlab/Simulink to test the functions dedicated to this technology. The results of the tests obtained and presented show the feasibility of this technology. The efficiency is also guaranteed because the electricity service is 100% assured in the absence of contingency and almost 70% during the contingency of the single-phase short-circuit type.

Modeling the Reliability of High-Voltage Power Transmission Lines Taking into Account the Influence of the Parameters of a Sharply Continental Climate

Modeling the Reliability of High-Voltage Power Transmission Lines Taking into Account the Influence of the Parameters of a Sharply Continental Climate

Measures and technical means for increasing efficiency and reliability of extra high voltage transmission lines

Electromagnetic transients are considered in the implementation of three-phase automatic reclose on the transmission line of extra high voltage 750 kV. The influence of automatic shunting of phases and pre-insertion active resistance for limiting the characteristics of the aperiodic component of the current, which obstructs the transition of full current through zero, is evaluated. The paper analyses measures taking into account the effect of changing the degree of compensation of charging power and the angles of switching on an SF6 circuit breaker. Sub-schemes of disconnected undamaged phases of the extra high voltage transmission line for the investigation of the aperiodic current component have been devel oped. The values of the pre-insertion active resistances of different connection and automatic shunting of the phases are determined at which there is an effective reduction of the characteristics of the aperiodic component of the current. In the software environment, a model was developed and switching transient processes were simulated in the 750 kV transmission line. Operating modes that are potentially dangerous for SF6 circuit breakers are determined and recommendations are given to avoid them. Currently the technical and economic requirements for power transmission lines designed for the transport of electricity from large power plants and for the communication of powerful energy systems are increasing. Today there is importance of reducing specific investment in the construction of new and reconstruction of existing lines. The solution to these issues is associated with the maximum use of power lines by increasing their power transfer capability and controlling modes, especially in operating emergency conditions and post-emergency operation of power systems.

Multi‐stage risk‐based dispatch considering short‐term reliability of transmission lines

The reliability of transmission lines (TLs) has great influences on the safe operation of power systems. Random failures from TLs can be caused by multiple uncertainties such as the high load current. In this study, a multi-stage risk-based dispatch model is proposed to minimise the sum of generation cost and risk cost. Impacts of natural ageing, load current, health condition and disaster weather on the short-term reliability of TLs are studied. For ensuring the operation security of power systems in the post-contingency stage, the dynamic thermal rating (DTR) technology is implemented to improve capacities of TLs for coping with the potential overload. In order to solve this non-linear optimiation problem caused by load current-dependent failure probabilities and thermal rating constraints, a double-iteration solving strategy is proposed. In exterior iterations, the sequential linear programming is applied to decouple bilinear terms of the risk cost and locally linearise failure probabilities. Meanwhile, in interior iterations, the Benders decomposition is utilised to further divide the model into the main problem and the sub-problem for coordinating the preventive and corrective control and checking the feasibility of DTR, respectively. Proposed approaches are validated on a modified IEEE 24-bus test system.

Research on the Technical Reliability of the Overhead Transmission Lines Based on the Life Cycle Technology

Based on the actual operating conditions of overhead transmission line, the safety and reliability of overhead transmission line is researched using the life cycle technology. Taking a 220kV overhead transmission line as an example, various parameters at different life stages are measured and analyzed, and finally the technical scheme most conducive to ensuring safe and reliable operation of the overhead transmission line is obtained. The research results provide a reference for the power company to ensure the safety of the power system operation and stimulate the innovation of power technology.

Impact of Dispersed Wind Farms’ Integration on Transient Stability of Interconnected Grid

In this paper, transient stability of wind farm based on Double-Fed Induction Generators is analyzed and discussed. The uncertainty of wind power production is a challenge to maintain the grid’s power stability. Thus, the contribution of integrating wind farms to the stability of the electrical systems during contingencies depends on several factors, including the location of the wind turbines in the electricity grid, the reliability of transmission lines, the relaying algorithms, the utilized protection devices and the wind turbines’ integration mode. This paper studies the benefits of wind turbines’ dispersed integration in the electrical grid by simulating transient stability voltage, current and rotor angle. Based on a real scenario involving a short circuit fault in the grid, a comparison between different types of wind turbines’ integration in the grid’s power has been established, using an optimal power flow calculation. In addition, this work discusses the reduction of power generation costs, based on the cubic cost model, which has been achieved by integrating the wind farm and comparing the production cost to the conventional power plants’. The aim of this article is to prove that the integration of wind farms in dispersed mode can be used as an alternative solution since it stabilizes grid parameters during strong transients. In fact, the response of active and reactive power to the output of the wind farm is stable during short-circuit faults, it minimizes the tripping events in the grid, it reduces energy losses, and ultimately it decreases energy production costs by optimizing the power flow when injected into high-demand PQ buses.

Self-blast state detection of glass insulators based on stochastic configuration networks and a feedback transfer learning mechanism

The self-blast state of a glass insulator directly affects the safety and reliability of transmission lines. To address the insufficient generalization ability of existing detection methods for insulator self-blast states and the drawbacks of deep neural network structures, the theories of transfer learning and closed-loop control are drawn upon to provide an intelligent detection method for the self-blast states of glass insulators. The method proposed in this paper is based on stochastic configuration networks and a feedback transfer learning mechanism. First, to reduce the redundancy of convolutional kernels in the channel extent, the interleaved group convolution strategy is employed to reconstruct the convolutional layers of the Inception network. Second, in view of the different feature applicabilities of different glass insulator images and based on the adaptive convolution module groups, the data structure of the dynamic feature space of insulator images is built with a certain mapping relationship from global to local. Then, the discriminative measure index is used to evaluate the discriminative information of the feature space to enhance the interpretability of the compact feature spance. Third, the fully connected feature vector of the compact feature space is sent to stochastic configuration networks (SCNs), which have universal approximation property to establish the classification criteria of the self-blast states of insulator images with generalization ability. Finally, an imitation of human thinking patterns is employed that exhibits repeated deliberation and comparison. Consequently, based on generalized error and entropy theories, the evaluation index of the objective function is established to evaluate the uncertain detection results of the self-blast states of glass insulator images in real time. Then, the dynamic transfer learning mechanism is constructed based on the constraint of the measurement index of uncertain detection results to realize self-optimizing regulation of the feature space that exhibits multihierarchy and discrimination and reconstructed classification criteria. The experimental results show that compared with other algorithms, the proposed method enhances the generalization ability and detection accuracy of the model.

Investigation of tail pipe breakdown incident for 110 kV cable termination and proposal of fault prevention

For cable termination, which is regarded as a key segment of power grid connecting cable lines with other electrical equipments, its insulation parts withstand much higher electric field strength than the average electric field strength of overall cable line. The excessive local electric field strength may result in the appearance of cable termination breakdown fault which can cause serious harm to the power supply reliability of whole transmission line. Historical statistics show that the breakdown location of cable termination is not confined to the vicinity of stress cone. However, the existing researches have not attached enough importance to the breakdown faults at the tail pipe of cable termination. Thus, it is of considerable significance to study the mechanism of breakdown fault at the tail pipe of cable termination. In this paper, a breakdown fault case of cable termination tail pipe on a 110 kV transmission line is investigated. Firstly, the disassembly inspection is applied to cable terminations of this fault line, and the possible breakdown reasons are preliminarily inferred. Then, a three-dimensional electric field simulation model of intact cable termination is established, and the mechanism of creeping discharge and air discharge inside the tail pipe occurred at the initial stage of breakdown fault is explained by this model. Subsequently, by setting defects on cable insulation surface in the simulation model of intact cable termination and varying the size of defects, the process of cable insulation damage inside the tail pipe formed in the initial stage developing into a penetrating cable insulation damage is simulated. Finally, the mechanism of breakdown fault case of cable termination tail pipe is concluded, and some improvement measures for the installation of cable terminations are proposed to reduce the incidence probability of such breakdown fault at the tail pipe of cable termination. The method for analyzing the breakdown fault case of cable termination tail pipe presented in this paper, which combines the disassembly inspection and simulation analysis, can provide reference and suggestions for the investigation and solution in similar cases.

A case study of rupture in 110 kV overhead conductor repaired by full-tension splice

Rupture accidents of overhead conductors may occur due to its complex operating environment. If wires rupture happens, the overhead conductors can be repaired by full-tension splice (FTS) in practical engineering to restore the mechanical strength and ampacity required. However, with time increases, ageing will occur on the overhead conductors. There may exist potential of rupture in the repaired segment of the conductor. Once the conductor is broken, the reliability of transmission line will be seriously destroyed. Therefore, it is of great importance to investigate the rupture reason and process of conductor repaired by FTS. In this paper, a rupture accident of 110 kV overhead conductor repaired by FTS is discussed. Firstly, the fractography analysis for the conductor sample is conducted, and the rupture reason is preliminarily inferred according to the rupture feature of the sample. Then, the current density distributions in the repaired segment of new conductor and aged conductor are compared by a finite element analysis (FEA) model of electromagnetic field. Also, the reason of high temperature produced in the conductor sample during rupture process is determined. Subsequently, to analyze the relationship between temperature and equivalent plastic strain, a FEA model of structure field for the steel core of conductor is established. Finally, combined with the fractography test results and simulation results, the rupture mechanism of conductor repaired by FTS is summarized in detail. The analytical method and conclusions proposed in this paper can provide references and suggestions for the study of similar conductor rupture accident and optimization of repaired process.

APPLICATION FEATURES OF POLY-CIRCUIT OVERHEAD TRANSMISSION LINES

It was shown the necessity to improve the operational reliability of overhead transmission lines as one of the main parts of the electric power transmission system. Question considered the feasibility of using poly-circuit overhead transmission lines. Analyzed the regulatory framework governing the design and construction of poly-circuit overhead transmission lines, as well as the calculation of electric and magnetic fields. It was shown that the regulatory framework governing nonrelevant to the possibility of using poly-circuit overhead transmission lines with a vertical arrangement of the phases wires. It was substantiated the advisability of additional in-depth studies of the electric and magnetic fields distribution of poly-circuit overhead transmission lines of various designs and voltage levels. It was presented the sequence of modeling the distribution of the electric field for overhead transmission line both traditional and poly-circuit design of 110 kV. It was presented the simulation results that confirm the accounting feasibility the design of transmission towers and the spatial arrangement of wires during the calculating of electric field strength. It was shown that simulation results using will significantly improve the reliability and operational safety of poly-circuit overhead transmission lines.

Short Time Modified Hilbert Transform-Aided Sparse Representation for Sensing of Overhead Line Insulator Contamination

The service condition of the overhead line insulators is significantly affected by the contamination deposited on the insulator surfaces. The reliability of transmission lines is therefore affected in the case of insulator failures. Leakage current signature has widely been reported to be a good indicator of the contamination level on the insulators. Different characteristics extracted from leakage current can be used to sense and classify insulators based on their contamination levels. In this paper, a method based on short time modified Hilbert transform (STMHT) and sparse representation-based contamination level sensing of overhead line insulator has been proposed. STMHT is capable of enhancing the local characteristic of the leakage current waveform and provides a good technique for differentiating between similar kinds of data. Sparse representation-based classification is used for classification of the extracted features. Results show that the performance is comparable or even better with respect to the results reported in the literature. The present method is generic in nature and can be implemented for any other applications addressing topologically similar problems. All necessary experiments are conducted based on IEC 60507 standard.

Determination of the power transmission line ageing failure probability due to the impact of forest fire

With increased occurrences of a forest fire, the short-term reliability of power transmission lines needs to be re-evaluated considering the impact of forest fire on the ageing of transmission lines. How to include the impacts from a forest fire on line ageing in a comprehensive way becomes an important issue for the study of line failure probability. In this study, a method is proposed to evaluate the impact of forest fire on line ageing degree based on dynamic heat balance equation and Weibull distribution. The method will help maintenance staffs to assess the damage level of transmission lines. The method is tested by a contrast experiment and a case study with real meteorological data. Simulation results show that forest fire can greatly threaten the reliability of power transmission lines, while during this process flame characteristics, wind and load ratio could be the major factors that affect the line reliability. With the results obtained, this study also provides the system operator with valuable instructions on how to reduce the damages caused by fire to transmission lines.