kV Double-circuit Transmission Line Research Articles

Simulation Analysis of Electric Field on the Body Surface of Personnel Engaged in Interphase Live Working on 750 kV Double Circuit Transmission Lines on the Same Tower

This article focuses on the assistance of electric lifting devices for phase-to-phase live working. Taking a typical 750 kV double circuit vertical arrangement line on the same tower as the research object, a three-dimensional simulation model of a real tower conductor simulated human is established. The field strength on the human body surface is calculated and analyzed during the process of operators entering the equipotential (conductor) while riding the electric lifting device in order to determine the risk points of the operation and determine the safety protection measures for the human body. Through simulation, it is found that when simulating human entry (exit) and phase-down operations, the human body is located at different distances of 0.4 m-1.5 m directly below the conductor. When not wearing shielding clothing, the maximum field strength of the human head is much greater than the allowable value. If using shielding clothing with a shielding efficiency of 60 dB for safety protection, the surface field strength inside the worker’s clothing can be reduced to 2.25 kV/m, meeting the requirements of live working. Operators should pay attention to the electric field protection at each phase wire when using an electric lifting device to enter (exit) the interphase wire. Equipotential operators must wear a complete set of shielding clothing for 750 kV live working.

Flashover pattern analysis for 275 kV double circuit transmission lines during direct lightning strikes

Lightning overvoltage causes outages of transmission lines (TLs) in tropical countries. Identifying and analyzing the key factors responsible for tripping the lines can improve the performance of the lines. In this work, the flashover patterns due to direct lightning strikes on 275 kV double circuit TLs and towers in Malaysia was evaluated with Electromagnetic Transient Program (EMTP-RV). Three parameters that include lightning current magnitude, power frequency angle and tower footing resistance were analyzed on the line performance during direct lightning strikes. The simulated results found that two key parameters, lightning current at 270 kA and footing resistance at 50 Ω, reveal the highest impact on the insulator flashover. This finding was also verified from multivariate analysis results which is rarely found in the previous works in this field. As a key contribution in this work and in validation to the model, the simulated fault waveform patterns and voltage magnitudes were compared with the actual site data obtained from six different locations in Peninsular Malaysia. The analyzed results show a similar waveform pattern with an overall average voltage magnitude difference of 6.0 % before and after fault. The model is useful to electric utilities for analyzing transient performance of TLs.

Comparative Analysis of 500 kV Double-Circuit Transmission Line Electric Field Intensity: Ethiopian Lines Compliance With ICNIRP

Comparative Analysis of 500 kV Double-Circuit Transmission Line Electric Field Intensity: Ethiopian Lines Compliance With ICNIRP

A protocol for selecting viable transmission line arrester for optimal lightning protection

Direct lightning strikes on overhead lines and towers causes power system outages. Optimal surge arrester placement is a practical and economical protection technique. From research trends, three types of transmission line arresters are in practice: Non-Gapped Line Arrester (NGLA), Externally Gapped Line Arrester (EGLA) and Multi Chamber Insulator Arrester (MCIA). This study proposed a simplified guide for selecting the most suitable line arrester considering the placement configurations, double circuit outage prevention and energy capabilities. Electromagnetic Transient Program was implemented to analyze back flashover performance of a typical 275 kV double circuit transmission line in Malaysia. Critical flashover parameters considered are lightning current magnitude, tower footing resistance, and power frequency angle. Analyzed results from the three arresters found that installing four arresters, two per circuit, at the lower and upper phases respectively, is the most optimal and universal double outage mitigation technique. Energy comparison reveals that MCIA discharges 54% and 44% less energy than NGLA and EGLA respectively. Also, from 132 kV system results, MCIA discharges 74% and 22% lesser energy respectively. From further validation of the simulation model, NGLA discharged 23.8% more energy than EGLA from experimental results. The proposed guide is applicable to double circuit lines below 275 kV.

Adopting Differential Lightning Protection Measures to Reduce Simultaneous Trip Probability of 220 kV Double-Circuit Transmission Line on the Same Tower

Double-circuit lines on the same tower are more widely used due to the increasing shortage of transmission corridors. If lightning strikes cause simultaneous tripping, it will cause severe economic losses and safety problems. Transmission lines with 220 kV voltage level are an essential part of the main grid. Reducing the simultaneous tripping rate of 220 kV lines is extremely important for the safe operation of the power grid. This paper analyses the advantages and disadvantages of several typical lightning protection methods for double-circuit lines on the same tower by simulation calculation. Combined with the characteristics of several typical double-circuit towers, lightning protection design for double-circuit lines is studied, and the differentiated lightning protection methods and basic protection processes for typical lines are proposed.

Performance research on ZigBee wireless sensor network self-organizing network for 220 kV four-circuit transmission lines on the same tower

With the integration of massive power transmission equipment and the Internet of Things (IoT), it is particularly important to choose a suitable low-power sensor networking structure, when facing a large amount of on-site sensing data. To select a suitable ZigBee network structure with a large number of embedded sensing nodes, for 220 kV four-circuit transmission lines on the same tower, this paper uses OPNET simulation software to conduct three different ZigBee wireless sensor network (WSN) models, respectively with star, tree and mesh topologies. Then, the performance of the Media Access Control (MAC) layer (delay and throughput performance), application layer (end-to-end delay and traffic received performance), and network layer (number of hops and packets dropped performance) is further investigated and compared for these three different ZigBee WSNs under 220 kV transmission scenario. Considering that quantity of sensing nodes would influence the ZigBee WSN performance greatly, thus, the simulation results under two application scenarios, 220 kV four-circuit transmission lines on the same tower and 500 kV double-circuit transmission lines on the same tower, were thoroughly compared and analyzed in this paper.

ANALYSIS OF APPROACHES FOR ESTIMATING THE LIGHTNING PERFORMANCE OF OVERHEAD TRANSMISSION LINES

Purpose. A review of the current literature, regarding the existing approaches used to estimate the lightning perfor-mance of overhead power lines, was performed. A review of available lightning activity data over India was also per-formed. Methodology. The electro-geometrical model was chosen to analyze the lightning performance of overhead power lines. International normative documents and national standard were used to highlight the main parameters that should to be paid main attention to when estimating lightning performance of overhead power lines. Results. Presently, approaches from IEEE and CIGRE guides can be used for analysis of statistical distributions of lightning current pa-rameters. Further studies are required on thunderstorm days, ground flash density and current parameters statistical dis-tributions for different locations, which will be supportive in performing analysis for Indian power lines. Originality. To graphically analyze the shielding failure mechanism with a help of electro-geometric model, the sketch of real 220 kV double-circuit transmission line tower was used. Using electro-geometric model it was graphically shown how downward lightning leader that propagate from thunderstorm cloud toward ground can finish its path on the overhead shield wire, phase conductor or ground plane. Practical value. Available data on lightning activity over different parts of India are still not enough complete. It is of great importance to obtain reliable statistical data on thunderstorm characteristics in the area of the studied power line route. Measurement techniques based on satellites have limitations in obtaining ground flash density values. Thus, for India there is a need in development of modern lightning detection networks and related studies on lightning characteristics. Conclusions. Future efforts should be focused on obtaining not only the positions and number of lightning strikes to the overhead power line, and calculation of lightning flashover rate parameters, but also the statistical distributions of lightning current values and related overvoltage parameters at the overhead wires and different phase conductors. References 21, figures 4.

Lightning Surge Analysis of Transmission Line Towers With a Hybrid FDTD-PEEC Method

This paper addresses lightning surges on the transmission systems with a new hybrid method, using a 1D FDTD model for the transmission line and a PEEC model for the tower and lightning channel. Compared with other circuit-based models, mutual coupling between the lightning channel and other parts in the system can be fully considered. This hybrid method has been validated numerically and experimentally, and good agreements are observed. This method then is applied to analyze the lightning surges on a 500 kV double-circuit transmission line system. It is found that the lightning channel has a significant impact on the surge response of the tower struck. Ignoring the coupling from the channel to the tower will weaken the hazard of lightning strikes. However, the influence of its coupling to the transmission line is not critical. The choice of interfacing points between these two models is then suggested. Furthermore, the influence of the tower footing is inves tigated. It is found that the insulator voltage is made of inductive and resistive components. The inductive component becomes dominant in the case of high soil conductivity and low grounding resistance. The voltage generally increases with decreasing soil conductivity and tends to decay slowly with time.

Research on induced current and induced voltage of 500 kV double circuit transmission line

Due to the loop distance of double circuit transmission line on the same tower is small, the electromagnetic coupling and electrostatic coupling between the power failure line and the running line are greatly enhanced, and higher induced current and induced voltage are generated on the power failure line. At the same time, the line is erected without transposition, the line’s three-phase parameter is asymmetrical, and the induced current and induced voltage show obviously phase separation characteristics. The paper apply transient simulation software EMTP to simulate the induced current and induced voltage under different line lengths, transmission power flow and phase sequence arrangement, which provides a reference for the design, planning and operation of 500 kV double lines on the same tower in the regional power grid.

A precise analytical method for fault location in double-circuit transmission lines

The mutual coupling impedance between two circuits of double-circuit transmission lines degrades the performance of the fault location module and ground fault unit of distance relays. The distance measuring unit may underreach when both circuits are in operation. Meanwhile, the overreach problem may arise when one of the parallel circuits is disconnected and grounded at both sides. The appearance of the zero sequence mutual coupling impedance between two circuits causes that single line to ground faults would not be accurately determined by the fault locator module and distance measuring units. Thus, in this paper a new analytical method is presented based on the measurement of voltage and current signals at both ends of the line in service. The fault distance is calculated by analysis of the equivalent sequence network during single line to ground fault condition while the switched-off circuit is grounded at both sides. The proposed formulation for fault location is independent of the fault resistance, so that the estimation accuracy dose not decrease for high fault resistances. In order to evaluate the proposed method performance, a 230 kV double-circuit transmission line is simulated in PSCAD/EMTDC environment considering different transposition strategies. The obtained results show that the proposed method is able to locate the fault distance precisely with the maximum error of 1%, while for most of the cases the error is even much lower. Moreover, fault location, source impedance, external noise and CT saturation have ignorable impact on the estimation accuracy.

Faults analysis of lightning stroke-caused flashover in 220 kV double-circuit transmission lines on the same tower

In this paper, four-phase simultaneous lightning stroke-caused faults have been analysed, which occurred in double-circuit transmission lines on the same tower. According to the fault patrol circumstance, lightning information data, fault recording imformation, ATP-EMTP transient simulation analysis, it can be determined that the four-phase flashover faults were caused by backflashover. The specific process was: lightning stroke top or ground line of 75# tower. The lightning current was shunted by the ground wire and the tower, and was injected into the earth through the grounding device, cause high electric potential to rise on the top of 75# tower, and backflashover overvoltage formed across the insulators of phase B and phase C, leading to insulators flashover and simultaneous trip-out.

Distribution of Magnetic Field in 400 kV Double-Circuit Transmission Lines

A high-voltage AC double-circuit 400 kV overhead power transmission line runs from the city of Elk (Poland) to the city of Alytus (Lithuania). This international 400 kV power transmission line is potentially one of the strongest magnetic field-generating sources in the area. This 400 kV voltage double-circuit overhead transmission line and its surroundings were analyzed using the mathematical analytical methods of superposition and reflections. This research paper includes the calculation of the numerical values of the magnetic field and its distribution. The research showed that the values of the magnetic field strength near the international 400 kV power transmission line exceed the threshold values permitted by relevant standards. This overhead power line is connected to the general (50 Hz) power system and generates a highly intense magnetic field. It is suggested that experimental trials should be undertaken in order to determine the maximum values of the magnetic field strength. For the purpose of mitigating these values, it is suggested that the height of the support bars should be increased or that any individual and commercial activities near the object under investigation should be restricted.

Research on Windage Yaw Flashovers of Transmission Lines under Wind and Rain Conditions

Windage yaw flashovers under strong wind and rain conditions leave a negative impact on the safe operation of transmission lines. However, the mechanism behind this is not well known yet. Therefore, this paper proposes a systematic method, including three basic parts described as simulation of wind and rain loads, calculation of windage yaw, and flashover analysis, to analyze windage yaw flashovers of transmission lines. The YanMeng-particle swarm optimization (YanMeng-PSO) algorithm is proposed to enhance the simulation accuracy. Unlike the conventional approach, the windage yaw status of conductors and insulator strings is dynamically described with key nodes and the breakdown voltage of their clearances rather than windage yaw angle. Furthermore, in the second part, a new method named key-node method (KNM) is proposed to calculate the conductors’ windage yaw. Moreover, the rain effect is also considered in this paper. This paper then presents a case study on a 110 kV double-circuit transmission line section that suffered severe collapse when the typhoon Rammasun landed in Hainan island. Particular focus was placed on the windage yaw flashover before the structural failure of the transmission line. The results validated the significant rain effect and found that conductors/ground suffer more severe windage yaw flashover than insulator strings. Finally, constructive solutions such as interphase spacers, reasonable conductor arrangement in the design phase, and regular measurements and adjustments of conductor sag in the maintenance phase are proposed to improve the design of transmission lines to enhance their capacity against windage yaw flashovers.

A protection technique for series capacitor compensated 400 kV double circuit transmission line based on wavelet transform including inter-circuit and cross-country faults

In this paper, wavelet transform based technique is introduced to detect and classify the faults in a series capacitor compensated double circuit transmission line. The three phase currents of both circuits measured at only one end of the series compensated double circuit transmission line are used to calculate the approximate and high frequency detail coefficients including wavelet energy content of each phase current signal. To evaluate the performance of proposed fault detection technique, simulation studies have been carried out on a series capacitor compensated double circuit transmission line test system. The major advantage of this proposed scheme is that it offers protection to entire transmission line length using one end fault current data only. The test results prove that all types of faults are correctly detected and the faulty phase is accurately identified using proposed technique. This technique is robust to the variation in fault type, fault inception time, fault resistance, ground resistance and fault location.Keywords: Fault detection, fault classification, series capacitor compensated double circuit transmission line, wavelet transform

Analysis of discharge energy on surge arrester configurations in 132 kV double circuit transmission lines

Surge arrester has been proven to be the most effective application to provide optimum lightning protection for the transmission line. Thus, many works on optimizing lightning protection for transmission line have been conducted since the past. However, works on minimizing double circuit outages and surge arrester physical properties during transient overvoltages are less likely to be found. Therefore, in this work, several surge arrester configurations installed on a 132 kV double circuit transmission line were modelled using EMTP-RV to investigate their capability to withstand current and energy discharged by lightning strokes during back flashover phenomena. These configurations were then compared to determine the most effective protection design based on the actual tripping pattern recorded by the lightning detection system (LDS) in Malaysia. The selection was made by considering arresters’ discharge energy due to variation in tower footing resistance, current magnitude, power frequency voltage, lightning tail time and front time, number of towers and span length. It was found that double circuit transmission line tripping can be completely eliminated by installing surge arresters at each phase conductor of one circuit. The selected arresters configuration provides sufficient lightning protection to the transmission line and complies with the discharge energy capability requirement specified by the utility company in Malaysia, of 5.1 kJ/kV for maximum continuous operating voltage (MCOV).

Analysis of Safety Protection Measures for Maintenance Work of 500 kV Double-Circuit Transmission Lines on Same Tower

Four transmission lines on the same tower are widely used because of their obvious economic and social benefits. But it also has high power supply reliability, so the choice of reasonable maintenance mode is particularly important. In this paper, we deducted the maintenance influence of the energized line to non-energized line, calculated and analyzed protection measures of non-energized singular line of 500kV double-circuit transmission line on the same tower with ATP software, and calculated field intensity distribution of typical operating position of the energized double-circuit transmission line with the finite element software. The calculation shows that when using the outage maintenance method, hanging both ground current and personal security line can reduce the current flowing through the operator’s body effectively. When using the live maintenance method, the field intensity of operator body strengths up to 383.69kV/m, The operator needs to wear shielding cloth with at least 43.08 dB shielding efficiency, in order to meet the security requirements.

Remote Sensing Interpretation and early Warning System Designing of Geohazards along Transmission Lines - A Case Study of the Danba - Kangding 500 kV Double Circuit Transmission Line

The landslide and debris flow investigation area for Danba ~ Kangding 500 kv double-circuit transmission line route selection is within Ganzi in Tibetan autonomous prefecture, with the area of about 440 km2. The topography, geomorphology, geologic structure, stratum lithology, natural factors, social and economic conditions have great influences on the transmission lines route selection and its construction. For comprehensive evaluation engineering rationality and construction convenience, remote sensing technology (RS) and geographic information system (GIS) technology are taken to implement geological environment survey. With field investigation, remote sensing images interpretation method is used to determine basic characteristics of the geo-hazards.

Fault diagnosis system for large power generation station and its transmission lines based on fuzzy relations

Summary This paper proposes a fault diagnosis system based on the fuzzy relation theory to estimate the faulty item/section(s) of a large power generation station and its transmission lines. Therefore, it diagnoses the faulted item/section(s) in terms of the degree of membership. Besides that, it also examines the mis-operation of corresponding circuit breakers. The proposed method utilizes the final information of protective relays and corresponding circuit breakers to build the sagittal diagrams which represent the fuzzy relations for each item/section(s). In order to testify the validity and feasibility of that method, a computer simulation of High Dam power generation station and its 500 kV double-circuit transmission lines is used. It is shown from two study cases that proposed fault diagnosis system is useful in diagnosing multiple faults as well as simple faults. Moreover, it has rapid reasoning, correct efficient and using flexible in a power generation station and its transmission lines for online fault diagnosis. Finally, it enables, assists and supports the operator of the power generation station control room to make the right decision, especially in case of loss of the communication with the dispatch center. Copyright © 2014 John Wiley & Sons, Ltd.

Petri Nets Fault Diagnosis System for a Large Power Station and its Transmission Lines

In order to assist and support the operation engineers in control center of a large power station to make rapid and reasonable decision in the critical situations. This paper proposes a fault diagnosis system based on Petri nets to estimate the faulty item/section(s) of that large power generation station and its transmission lines with solving the excess information which received in control center. The proposed methodology utilizes the final information of protective relays and corresponding circuit breakers to build a fault diagnosis model based on Petri net for each item/section(s). It can diagnose and estimate the faulty item/section(s) correctly for multiple faults as well as simple faults. Moreover, it examines the misoperation of circuit breaker based on the relays information and then determines the faulty item/section(s). In order to testify the validity and feasibility of the method, a computer simulation of High Dam power generation station and its 500 kV double-circuit transmission lines is used. It is shown from two study cases that the Petri nets fault diagnosis method has many merits such as: accurate fault diagnosis results, rapid reasoning, less storage memory, easy and flexible correctness of Petri nets fault diagnosis models for each item/section(s). Moreover, it can be applied into a large power generation station and its transmission lines for real time fault diagnosis

Method for Increasing Sensitivity of the Distance Protection on a 330 KV Double-Circuit Transmission Line

Method for Increasing Sensitivity of the Distance Protection on a 330 KV Double-Circuit Transmission Line Possibilities of increasing the distance protection (DP) sensitivity are considered for a double-circuit transmission line connected to a substation busbar only with one circuit-breaker in each phase. The DP sensitivity can be increased on such a line using mutual connections of the phase wires along its whole length. The minimal (optimal) number of the connections is found by the proposed calculation method.