EHV Transmission Lines Research Articles

Detection and Classification of EHV Transmission Line Faults Based on Sign of Reactive Power

Detection and Classification of EHV Transmission Line Faults Based on Sign of Reactive Power

A simple approach for the protection of EHV transmission lines

Due to the geographically widespread nature of the transmission lines, the chances of fault occurrence are more due to outdoor erection. This makes it inevitable to detect and isolate the faulty section of the system as quickly as possible. The existing fault detection and classification algorithms are limited to a specific configuration of transmission lines. This work has proposed a novel and simple methodology to recognize and classify faults on transmission lines by using single-end current data. A Harmonic Phasor Measurement Unit (HPMU) based on a non-recursive DFT algorithm is used to extract the fundamental and second-order harmonic components from current samples. The Equivalent Fundamental Component (EFC) and ΔEFC are estimated from the extracted data. Subsequently, an Index Matrix (P) is derived to recognize the fault. The non-zero value of the determinant of the index matrix detects the occurrence of a fault in the system. Second-order harmonic fault current coefficients are proposed for fault classification based on the second-order harmonic component extracted from HPMU. The proposed method accurately detects and classifies all types of conventional faults and cross-country faults (CCF) for any configuration of transmission network. The proposed method has also been validated under various abnormal conditions in PSCAD/EMTDC to ensure its efficacy.

Fuzzy Location Algorithm for Cross-Country and Evolving Faults in EHV Transmission Line

Fuzzy Location Algorithm for Cross-Country and Evolving Faults in EHV Transmission Line

Audible noise analysis of 750‐kV AC transmission line in high‐altitude area under different weather

AbstractIn order to build UHV AC transmission lines at high altitudes, it is necessary to analyze the audible noise (AN) characteristics of the existing EHV transmission lines at high‐altitude areas to guide the design. The typical test data of AN for 750‐kV single‐circuit transmission lines measured at the Guanting long‐term observation station, located at an altitude of 1854 m, were collected. Two methods of sorting the test data of AN and extracting valid data were given. Then the levels of AN under different weather conditions were analyzed, which showed that AN was raised with the increase of instantaneous rainfall and snowfall. Typical frequency spectrums of AN under different weather were also obtained, the pure tone at 100 Hz was more prominent under rainy and snowy weather, and the pure‐tone oscillation attenuated at different positions. The statistical results and the calculated difference of AN over 5.5 h with continuous rainfall were obtained. For the 750‐kV transmission line in the quiet plateau areas, the calculated difference between AN during rainy days and fair weather can be taken as 25 dB, and the calculated value of the altitude correction coefficient of 2.85 dB/1000 m is better consistent with the measured value.

A continuous wavelet and fast fourier transform-based single-phase adaptive auto-reclosing scheme for ehv transmission lines

A continuous wavelet and fast fourier transform-based single-phase adaptive auto-reclosing scheme for ehv transmission lines

Determining optimal technical solutions for new EHV transmission lines (OHL/UGC) in an early project stage

Determining optimal technical solutions for new EHV transmission lines (OHL/UGC) in an early project stage

A Simple Approach for the Protection of Ehv Transmission Lines

A Simple Approach for the Protection of Ehv Transmission Lines

Influence of the Secondary Arc on the Operation of Single Phase Autoreclosure of the 400 kV interconnection between Hungary and Croatia


 
 Sažetak: Faults on EHV lines are generally single-phase-to-ground ones and not permanent in the majority of cases. Thus single phase auto reclosure (SPAR), at which the faulty phases are tripped for a short time, eliminates the predominant part of the faults [1,2]. The secondary arc, which follows the high power arc after tripping the faulty phases at both side of the line may endanger the successfulness of reclosing if the duration of the switched off interval (dead time) is not long enough to ensure the extinction of the arc. The secondary arcing times recorded on different EHV lines or measured in laboratory tests show significant spread, consequently, to select a dead time according to the longest experimental secondary arc extinction time is not feasible. During commissioning of the double circuit 420 kV interconnection between Hungary and Croatia several staged faults were initiated to analyze the arc extinction performance. Initially the line was in operation by connecting the two circuits in parallel along the 1/3rd of the full length. In this configuration the longest secondary arc extinction time was 4 seconds and the secondary arc has not extinguished in 27s in one of the tests, so the line had to be tripped out to clear the staged fault. Later on, the length of the Croatian section of the line has been significantly shortened after putting a new substation into service. The increased performance of SPAR of the new arrangement has been proved with field tests. A realistic representation of the secondary arcs is essential in determining the auto-reclosure performance of EHV transmission lines. As shown in the paper, the random variation of the arc parameters influences significantly the arc extinction time. The results of the field tests confirmed the importance of the distributed nature of the transmission line and the nonlinear characteristic of the arc resistance in the intermittent region of arcing, where temporary extinctions and sudden re-ignitions in the arc channel produce transient wave processes along the line.

Algorithm for Solving Trip‐Out Rate Due to Shielding Failure of Bent Transmission Line

Accurate assessment of lightning protection performance of extra high voltage transmission lines is important for transmission line design and different lightning protection. Based on the electro‐geometrical model, this paper introduces the angle influence factor, and presents an algorithm for shielding failure trip‐out rate of angle tower, and the existing algorithm is expanded. By establishing the three‐dimensional geometric model of the angle tower, the electrical geometric relations of conductors and ground wires on both sides are analyzed, respectively, and the projection area algorithm for shielding failure is modified. To further verify the application value of the calculation algorithm, the change of the shielding failure trip‐out rate of the typical angle tower with the bending angle of transmission line and the tower height in a 500 kV transmission line is analyzed. The analysis results show that the trip‐out rate of the outside corner is higher than that of the inside one, and with the increase of the angle and the height of the tower, the trip‐out rate shows an upward trend. When the tension tower height is 71.5 m and the angle increases from 0° to 80°, the outside shielding failure trip‐out rate increased by 10.9% and the inside decreased by 9.3%. Compared with the classical electro‐geometrical model calculation, the difference of trip‐out rate is 4.3% when the bending angle is 80°. When the tangent tower height is 70 m and the angle increases from 0° to 40°, the shielding failure trip‐out rate on the outside increased by 5.9% while the inside decreased by 6.2%. The research results provide a simple algorithm for solving bending transmission line and give some reference for lightning protection design of EHV transmission lines. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Improved Electrogeometric Model of UHV Transmission Line Based on Long Gap Discharge and Its Application

Based on long air gap discharge test data and lightning return stroke observation data, an improved electrogeometric model (EGM) considering terrain conditions is established and verified to analyze the lightning shielding performance of UHV transmission lines. The striking distance formula is modified as rs = 0.13 (I2 + 40I)0.814. In this paper, the lightning shielding failure rate of three-phase conductors of EHV and UHV transmission lines calculated by the improved EGM model is consistent with the lightning observation data of actual transmission lines in Japan and the scaled lightning discharge simulation experimental results of UHV transmission lines in plains and mountainous areas of China, which verifies the applicability of the improved EGM model to evaluate the lightning shielding performance of large-scale UHV transmission lines. The improved EGM model is applied to evaluate the influence of tower type and slope steepness on the shielding failure tripping rate of UHV transmission lines. The shielding failure tripping rate of the SZ322 tower is higher than that of the SZT1 tower, and the shielding failure tripping rate of UHV transmission lines is greatly affected by slope gradient and increases with the increase of slope gradient.

ДОСЛІДЖЕННЯ РЕЖИМУ НАПРУГИ В ДАЛЬНІХ ЛІНІЯХ ЕЛЕКТРОПЕРЕДАЧІ ЗМІННОГО СТРУМУ

The charging currents of EHV transmission lines cause the Ferranti effect, which causes an increase in voltage at intermediate points transmission line. The work aims to study the laws of the voltage distribution along the line route and to develop a method for determining the coordinates of a point with extreme voltage. Methodology. Mathematical modeling of long-distance transmission lines in Wolfram Mathematica allowed to form the laws of the voltage distribution along the line and determine the coordinate of the extreme point on the voltage. Results. It is shown that the application of the traditional model of idealized power transmission causes high modeling accuracy only in the modes of unloaded line and low loads. In the range of medium and high loads, the simulation error reaches unacceptably large values. The paper proposes more accurate models for determining the coordinate of an extreme voltage point: linearized and second- and third-order models. It is shown that the proposed models are characterized by higher accuracy in a wide range of loads. Increasing the degree of the model results in higher accuracy, but is associated with an increase in the cumbersomeness of the mathematical model. It is shown that first and second-order models provide sufficient accuracy for typical designs of 750 kV power transmission lines. It is shown that neglecting the losses on the corona has almost no effect on the accuracy of calculating the coordinates of the extreme point on the voltage, which simplifies the linear calculation model and models of the second and third-order. Originality. Mathematical models of the first, second and third orders have been developed for high-precision determination of the coordinate of a voltage-extreme point along a long-distance transmission line. Practical significance. The offered mathematical models are intended for application in problems of regulation and adjustment of parameters of flexible power transmissions. Ref. 12, figure, tables 4.

Research on Type Selection of Diving Tower in 110kV Single and Double Circuit Transmission Line

With the continuous development of EHV (UHV) transmission lines，new lines often need to drill through the built lines，so it is urgent to study the type of diving towers. Based on typical weather conditions and commonly used ground wire models, the basic type and tower type selection of 110kV single and double circuit overpass towers in high altitude areas are studied, and two single and double circuit overpass tower schemes are planned and arranged. And according to the pole tower structure design and optimization theory, the 110kV single-circuit diving tower and the 110kV dual-circuit diving tower are optimized from the structural optimization layout and the pole tower structure node optimization design. The research results show that the single-circuit diving tower adopts the wine glass tower, and the wires are arranged horizontally, and the double-circuit diving tower effectively reduces the height of the tower. The dish-shaped tower is used, and the single-circuit wires are arranged in a triangle pattern, which provides a certain practical guiding significance for the 110kV diving-across technology application.

Research on Resonance Overvoltage of EHV Transmission Lines Caused by Lightning Strike

This paper studies the mechanism and influencing factors of resonance overvoltage of EHV transmission lines caused by lightning. By analyzing the time domain steady state of the simplified resonance circuit, the physical mechanism of resonance is revealed. The characteristics of resonance transient process and overvoltage waveform are analyzed by using electromagnetic transient simulation. The main influencing factors of overvoltage amplitude are also studied. The results show that: 1) During uneven open-phase conditions, resonant circuit involving shunt inductors and line equivalent capacitor obtains energy from lightning strikes, which may lead to resonance. 2) the transient process of resonance can be divided into three stages, including lightning stage, lightning-resonance conversion stage and steady-state resonance stage, among which the voltage of the first two stages are higher; 3) the lightning strike time, lightning current parameters and subsequent lightning strike affect on the overvoltage amplitude, which leads to the random amplitude in overvoltage.

Tests of selected distance protection functions of modern protective relay used for HV and EHV transmission lines protection

Tests of selected distance protection functions of modern protective relay used for HV and EHV transmission lines protection

Construction Management of EVH & UVH Transmission Lines A Practical Guide

Generation projects are generally located in areas nearer to availability of inputs required for power generation such as water, coal, approach roads and having rail transport facilities. The load centers are at different locations depending its own convenience load requirement. Hence there is necessity of transmission of bulk power from generation sites to load or consumer points. Hence the utility of power transmission through EHV/UHV transmission lines. Further for transmission of bulk power from one region of country to another region also warrants establishment of Transmission lines. The technical as well as social and commercial criteria are very important while construction and erection of EHV and UHV transmission lines. These issues are of public as well as organization importance and hence efforts have been made in this presentation to elaborate in detail.

A Hybrid PSO-ANN-based Fault Classification System for EHV Transmission Lines

The paper presents a robust design of Artificial Neural Network Classifier used for the classification of faults occurring on Extra High Voltage Transmission lines with multiple series compensation. The feature selection and model parameters play a vital role in providing better accuracy as well as stability of Classifier in recognition of fault patterns. The paper describes the use of Particle Swarm Optimization (PSO)-assisted training of Artificial Neural Network (ANN). The PSO is used to find the optimal number of features to attain sufficiently high accuracy along with optimal design parameters of ANN so as to reduce the computational burden. A combined use of Multiresolution Wavelet Analysis (MRA) and Statistical Features (SF) module is shown for fault pattern analysis. A Particle Swarm optimization based Neural Network with Feature Selection (PSONNFS) Algorithm developed is applied on a large database of fault patterns with a wide range of operating conditions in series compensated system. The best features found from the PSONNFS algorithm are later used to find the optimal structure of ANN. The results obtained provide an enhanced model of ANN with a high degree of accuracy with optimality in Classifier parameters. A Genetic Algorithm based Neural Network optimization with Feature Selection (GANNFS) is also developed to verify the performance of the classifier. The results of the PSONNFS algorithm are further compared with the GANNFS algorithm. The results obtained show an enhanced model of ANN using PSONNFS which has a high degree of accuracy with optimality in Classifier parameters.

Prospect of voltage uprating of a conservatively designed EHV transmission line

Voltage uprating of existing overhead lines provide a useful method to tackle increasing power demands under present circumstances, where there is growing opposition to the construction of new power transmission installations. In the past, voltage uprating techniques have been applied to lines formerly intended to operate up to 275kV, but there is an incentive to examine the prospect of uprating lines of even higher voltages which have been designed conservatively with deterministic procedures. This paper explores the prospect of voltage uprating of an existing 500kV double-circuit overhead transmission line in Pakistan. The study includes statistical evaluation of line insulation under switching overvoltages, lightning and pollution together with assessment of corona effects and low frequency electric and magnetic fields. It has been shown that voltage uprating of the studied line to 735kV is achievable whilst satisfying performance criteria.

A novel EHV transmission line protection of adequate fault-resistance sensitivity and faulted-phase selectivity

The summation impedance relay (SIR) is characterized by a strong sensitivity to high-resistance faults. However, previous studies have not made SIR completely immune to the adverse influence of distributed capacitive currents and have ignored its inherent deficiency of faulted-phase selectivity. Therefore, a novel protection scheme is proposed. First, by compensating distributed capacitive currents, an improved ground-type SIR (composed of ground distance relays) is created. Using this SIR, the identification of internal high-resistance faults is performed while guaranteeing security under external faults. Then, a novel phase-type SIR (composed of phase distance relays) is designed, based on which a suitable phase-selection algorithm is proposed to distinguish single-phase faults and multi-phase faults. Comprehensive simulations show the security and dependability of the proposed protection scheme in various fault scenarios, including non-linear high-impedance faults and series compensation scenarios. Moreover, the approach’s performance under power swings is investigated, revealing its complementarity with existing protection principles.

Pilot Relaying Scheme Based on Differential Admittance Concept for FSC-Compensated EHV Transmission Line

This article presents a novel per-phase differential admittance (DA) concept-based relaying scheme applied in transmission system with fixed series capacitors. For a given two-bus system, DA is defined as the difference in the sending-end and receiving-end bus admittances at a given instance. This per-phase DA relaying scheme detects, classifies and trips the faulty phase accurately with fast response. The system is modeled and validated with PSCAD/EMTDC software with real-time 400 kV system parameters, and the algorithm has been programmed in MATLAB. The global positioning system time-stamped synchronized measurement is used. Also, the proposed algorithm has been verified successfully with two-machine system hardware with real-time data. The proposed scheme uses only one-cycle moving window, sample-by-sample checking information and has a low computational burden. The benefit of this scheme is that there is no need to change relay threshold settings for uncompensated and series-compensated line. The proposed scheme is tested on a variety of fault parameters. Simulation and hardware results demonstrate the reliability, accuracy and the fast approach of the proposed scheme over other conventional schemes.

Enhanced Summation Impedance Relay for EHV Transmission Lines

For the safety and stability of EHV transmission lines, the identification and isolation of high-resistance single-line-to-ground faults have increasingly been a focus of research. However, the existing protection schemes have shown limitations in different aspects when the fault resistance is extremely high. To solve this problem, an Enhanced Summation Impedance Relay (ESIR) is proposed in this manuscript. An adaptive threshold is set by using the double-end absolute values so that the ESIR can trip the internal fault independent of the data synchronization. Under the open-phase operating conditions, the sound phase ESIR holds sufficient capability against high-resistance faults. Simulation and comparison studies show that the proposed ESIR can work in parallel with several types of existing main protection elements to supplement them to improve high-resistance fault detection. This cooperation enables enhancement of the sensitivity and operating speed of the line protection.