Operation Of Overhead Transmission Lines Research Articles

Triboelectric–electromagnetic hybridized module for energy harvesting of power transmission lines galloping and self-powered galloping state monitoring

With the vigorous advancement of smart power grid, online monitoring is essential for a stable operation of overhead transmission lines. The energy supply that drives the monitoring system has become one of the bottlenecks restricting the development of distributed sensing systems. In view of the self-excited vibration with the characteristics of low-frequency and large-amplitude generated in the conductor galloping, a hybridized generator has been designed to be composed of an electromagnetic generator (EMG), a horizontal TENG (H-TENG), and a vertical TENG (V-TENG) to provide an alternative approach for capturing mechanical energy derived from conductor galloping. Based on triboelectric–electromagnetic working principal, a sophisticated-designed stator and rotor structure oriented to the application scenarios of transmission lines successfully achieved self-power through the designed EMG and galloping state sensing through the designed H-TENG and V-TENG, respectively. The output performance, feasibility and durability of the hybridized generator was well validated on the linear motor platform and the conductor galloping test platform, and the output current was used to realize the characterization of the conductor galloping amplitude and galloping trajectory. This work not only provides an effective and sustainable solution to the self-powered intelligent sensor nodes in the complex surroundings of power transmission system, but also reveals TENG promising potential on the sensing applications in low-power monitoring sensors for conductor galloping.

Lightning Failure Risk Assessment of Overhead Transmission Lines Based on Modified Dempster–Shafer Theory

Lightning has a certain degree of potential threat to the safe operation of overhead transmission lines. In order to make targeted lightning protection arrangements and reduce the impact of lightning on overhead transmission lines, it is necessary to conduct lightning risk assessments on overhead transmission lines. This paper proposes a lightning failure risk assessment method for overhead transmission lines based on a modified Dempster–Shafer theory. First, analyze the historical lightning failure data of the line, determine the lightning failure impact factors, and use confidence to express the relationship between the lightning failure and the impact factor; then, use entropy weight theory and gray relational theory to calculate the value of mass function, and modify it on this basis; finally, use Dempster–Shafer theory to determine the trust degree and fit this with the calculated lightning trip rate to produce the risk assessment. This paper analyzes the lightning failure data of overhead transmission lines in some areas of Hebei Province. The results show that, compared with the evaluation method of the Dempster–Shafer theory, the accuracy of the evaluation is improved to a certain extent after correcting the mass function value. It can be seen that this method can integrate and comprehensively consider different data and can provide a reference for preventing damage to transmission lines by lightning strike weather.

Safe Operation of Overhead Transmission Lines

Safe Operation of Overhead Transmission Lines

Research on the Technology of Conductor Corrosion Detection based on Eddy Current Testing

The detection of conductor corrosion state provides technical guarantee for mastering the corrosion type, corrosion degree and service life of power transmission lines, realizing the timeliness and accuracy of power line replacement, and reducing the hidden danger of line safety. In this paper, a method based on eddy current testing for corrosion detection of power wire is proposed. High and low frequency eddy current testing is used to measure the residual cross-sectional area of wire, and the output database of flaw detection is established to deduce the residual tensile force of wire. Finally, by introducing the artificial single line sample and the actual running conductor for dynamic comparison, the residual tension data of the conductor can be corrected. The results show that the method adopted in this paper is feasible and accurate, which further guarantees the safe and reliable operation of overhead transmission lines.

Calculation of the Dynamic Wind-Induced Deflection Response of Overhead Lines: Establishment and Analysis of the Multi-Rigid-Body Model

Wind-induced deflection flashover severely endangers the normal operation of overhead transmission lines. This paper proposes a multi-rigid-body model for the accurate and efficient calculation of the dynamic wind-induced deflection response of overhead transmission lines under high wind conditions, given the dynamic equation and the general value of the number of equivalent rigid rods of the multi-rigid-body model. The accuracy of the multi-rigid-body model is verified through comparison with the finite element method (FEM) for an engineering example calculation. The efficiency of the multi-rigid-body model is indicated by comparing the time required to solve the wind-induced deflection response of overhead transmission lines with different numbers of spans. In contrast to the traditional static analysis method, the multi-rigid-body model can consider the dynamic characteristics in the wind-induced deflection of overhead lines, which makes the calculation results more accurate. Compared with the FEM, the multi-rigid-body model is easier to use and faster to solve. It is beneficial for development and application in engineering.

Electric Field Simulation of Equipotential Live-line Work in 500kV Cup-type-tower

As an important part of the power grid, the safe and reliable operation of overhead transmission lines is of great significance. In order to ensure the reliability and continuity of power supply in power grid, the overhaul mode of live-line work is usually adopted. At present, there is little research on live-line work of overhead transmission line overhaul arrester at home and abroad. In order to ensure the safety of live-line work operators, this paper models and simulates live-line work of overhauling surge arrester with support clearance in 500 kV cup-type-tower. The distribution of electric field on the surface of live-line work operators under this line structure is calculated and analyzed, which can provide reference for the personal safety of live-line work operators.

Partition dynamic threshold monitoring technology of wildfires near overhead transmission lines by satellite

Wildfires are a major natural disaster that can threaten the safe and stable operation of overhead transmission lines. Compared with large-area forest fires, transmission-line wildfires usually cover a small area and spread rapidly, making monitoring accuracy and real-time requirements of high priority. Wildfire monitoring based on satellite remote sensing has advantages in terms of monitoring-range width and the capacity for real-time monitoring; however, the detection threshold changes dynamically due to the influences of climate, geography, weather, and other factors that affect monitoring accuracy. To focus on small-area wildfires near overhead transmission lines, we developed a partition dynamic threshold calculation method based on time-series prediction. Basic thresholds are obtained based on a large number of historical values, followed by partitioning one of these values according to digital elevation model data and subsequent correction. Compared with conventional constant-threshold monitoring methods, our proposed method significantly reduced missed and false detection rates. Additionally, to improve fire-spot localization to the overhead transmission-line towers, we developed a tower-location algorithm based on block searching. Compared with the traditional traversal algorithm, our algorithm enabled a 15,000-fold increase in operation speed. These improvements will significantly enhance the monitoring of transmission-line wildfires, which are highly reliant upon alarm speed.

Calculation of Admissible Currents for the Protected Wires of 110 kV Overhead Lines

Protected wires have insulation from cross-linked polyethylene with low heat conductivity, which impairs heat removal from the hot wire. A methodology is proposed for designing admissible continuous currents for the insulated wires of overhead transmission lines, taking into account various climatic conditions, and based on the solution of the equation of thermal balance. The materials provided in this article can be used for design and operation of overhead transmission lines on which the protected wires are used.

Estimation of the shielding performance of transmission lines considering effects of landform, lightning polarity and stroke angle

Lightning is the main cause of transmission system outages, affecting reliability of power supply and resulting in economic losses. Shielding failure is an important issue in addressing the lightning performance of overhead transmission lines. In this paper an improved method based on the electro-geometric model is proposed to evaluate the shielding failure flashover rate (SFFOR) of transmission lines, considering the influences of landform, lightning polarity and stroke angle. In the improved method, the striking distances to phase conductors, shield wires and ground are properly differentiated by using recent equations developed to take into account other factors not only magnitude of lightning strokes. These factors include height of wires as well as lightning polarity. To reflect the effects of changes in terrain and height of wires on SFFOR, a method for identifying the topography and the relative position among the wires and ground is proposed. A 400-kV double-circuit transmission line section in complex terrain area was taken as example, and the results show that this method can reflect changes of the SFFOR along the span and can be useful to figure out which towers are easy to be struck by lightning along the entire transmission line. This research is helpful for the design and operation of overhead transmission lines.