scholarly journals Experimental Evaluation of 3D Tortuosity of Long Laboratory Spark Trajectory for Sphere-Sphere and Sphere-Plane Discharges under Lightning and Switching Impulse Voltages

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7409
Author(s):  
Michał Molas ◽  
Marcin Szewczyk
Keyword(s):  
High Voltage ◽  
Transmission Lines ◽  
Development Process ◽  
Power Transmission ◽  
Measurement Data ◽  
Simulation Models ◽  
Leader Development ◽  
Deterministic Models ◽  
Lightning Leader ◽  
Line Design

Evaluation of attractive areas of high- and ultra-high voltage power transmission lines to direct lightning strokes is based on modeling of propagating progress of the lightning leader approaching the transmission line. The aim of the modeling is to determine the effectiveness of lightning protection for a given line design. The statistical models are currently being developed to extend the conventional deterministic models by embracing the randomness of the discharge channel in space and hence to reproduce the statistical distribution of the striking points. These models require experimental data for understanding of the lightning leader development process and to validate the model across the measurement data. This paper reports on the measured trajectories of discharge channels of long laboratory sparks in various high voltage laboratory arrangements. The sparks were initiated by switching and lightning impulses with peak values ranging from 1200 kV to 3364 kV of positive and negative polarity for two types of high-voltage electrode systems (sphere-sphere and sphere-plane), arranged at distances of 3.3 m and 5.5 m from each other. Statistical distributions of angles describing trajectory of discharge channels in space are reported for a total number of 540 recorded discharges. The results can serve as reference measurement data to develop and evaluate the accuracy of simulation models incorporating statistical nature of the lightning leader development process.

scholarly journals Remote Monitoring of Joints Status on In-Service High-Voltage Overhead Lines

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1004 ◽  
Author(s):  
Carlo Olivieri ◽  
Francesco de Paulis ◽  
Antonio Orlandi ◽  
Giorgio Giannuzzi ◽  
Roberto Salvati ◽  
...  
Keyword(s):  
High Voltage ◽  
Transmission Lines ◽  
Remote Monitoring ◽  
Power Transmission ◽  
Measurement Data ◽  
Time Domain Reflectometry ◽  
Overhead Line ◽  
Voltage Transformer ◽  
Remote Monitoring System ◽  
On Line

This work presents the feasibility study of an on-line monitoring technique aimed to discover unwanted variations of longitudinal impedance along the line (also named “impedance discontinuities”) and, possibly, incipient faults typically occurring on high voltage power transmission lines, like those generated by oxidated midspan joints or bolted joints usually present on such lines. In this paper, the focus is placed on the application and proper customization of a technique based on the time-domain reflectometry (TDR) technique when applied to an in-service high-voltage overhead line. An extensive set of numerical simulations are provided in order to highlight the critical points of this particular application scenario, especially those that concern the modeling of both the TDR signal injection strategy and the required high-voltage coupling devices, and to plan a measurement activity. The modeling and simulation approach followed for the study of either the overhead line or the on-line TDR system is fully detailed, discussing three main strategies. Furthermore, some measurement data that were used to characterize the specific coupling device selected for this application at high frequency—that is, a capacitive voltage transformer (CVT)—are presented and discussed too. This work sets the basic concepts underlying the implementation of an on-line remote monitoring system based on reflectometric principles for in-service lines, showing how much impact is introduced by the high-voltage coupling strategy on the amplitude of the detected reflected voltage waves (also named “voltage echoes”).

scholarly journals Global experience of HVDC composite insulators in outdoor and indoor environment

2020 ◽  
Vol 59 (1) ◽  
pp. 606-618
Author(s):  
Mohammad Akbar ◽  
Basharat Mehmood
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Transmission Lines ◽  
Power Transmission ◽  
Green Energy ◽  
Attractive Alternative ◽  
Hvdc Transmission ◽  
Ceramic Insulators ◽  
High Power Transmission ◽  
Aging Performance

AbstractHigh-voltage direct current (HVDC) transmission is known as green-energy transfer technology and has recently become an attractive alternative of high-voltage alternating current (HVAC) due to its high-power transmission capability and lower power loss. Use of composite insulators on direct current (DC) transmission lines experienced rapid growth in recent years due to their high hydrophobicity and better performance in contaminated environment than conventional ceramic insulators. During their service operation on DC lines, insulators are prone to more accumulation of contaminants due to unidirectional electric field. The contaminants under wet conditions allow leakage current to flow on the insulator surface. Being organic in nature, polymeric insulators have a tendency to age under the combined effects of electrical and environmental stresses. To fully understand the long-term aging performance of DC composite insulators, a detailed survey was considered necessary. Towards that end, this paper critically summarizes worldwide experience of aging performance of composite insulators in the field as well as in laboratory conditions.

scholarly journals Wind: generating power and cooling the power lines

2020 ◽  
Vol 17 ◽  
pp. 105-108
Author(s):  
Marko Kaasik ◽  
Sander Mirme
Keyword(s):  
Wind Speed ◽  
Electric Power ◽  
High Voltage ◽  
Transmission Lines ◽  
Power Transmission ◽  
Mixed Forest ◽  
Wind Farms ◽  
Power Line ◽  
Power Lines ◽  
Local Wind

Abstract. The electric power that can be transmitted via high-voltage transmission lines is limited by the Joule heating of the conductors. In the case of coastal wind farms, the wind that produces power simultaneously contributes to the cooling of high-voltage overhead conductors. Ideally this would allow for increased power transmission or decreased dimensions and cost of the conductor wires. In this study we investigate how well the wind speed in coastal wind farms is correlated with wind along a 75 km long 330 kW power line towards inland. It is found that correlations between wind speed in coastal wind farms at turbine height and conductor-level (10 m) are remarkably lower (R=0.39–0.64) than between wind farms at distances up to 100 km from each other (R=0.76–0.97). Dense mixed forest surrounding the power line reduces both local wind speed and the correlations with coastal higher-level wind, thus making the cooling effect less reliable.

scholarly journals Do High-Voltage Power Transmission Lines Affect Forest Landscape and Vegetation Growth: Evidence from a Case for Southeastern of China

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 162 ◽  
Author(s):  
Xiang Li ◽  
Yuying Lin
Keyword(s):  
High Voltage ◽  
Transmission Lines ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Power Transmission ◽  
Mesh Size ◽  
Forest Landscape ◽  
Power Transmission Lines ◽  
Vegetation Growth ◽  
Landscape Types

The rapid growth of the network of high-voltage power transmission lines (HVPTLs) is inevitably covering more forest domains. However, no direct quantitative measurements have been reported of the effects of HVPTLs on vegetation growth. Thus, the impacts of HVPTLs on vegetation growth are uncertain. Taking one of the areas with the highest forest coverage in China as an example, the upper reaches of the Minjiang River in Fujian Province, we quantitatively analyzed the effect of HVPTLs on forest landscape fragmentation and vegetation growth using Landsat imageries and forest inventory datasets. The results revealed that 0.9% of the forests became edge habitats assuming a 150 m depth-of-edge-influence by HVPTLs, and the forest plantations were the most exposed to HVPTLs among all the forest landscape types. Habitat fragmentation was the main consequence of HVPTL installation, which can be reduced by an increase in the patch density and a decrease in the mean patch area (MA), largest patch index (LPI), and effective mesh size (MESH). In all the landscape types, the forest plantation and the non-forest land were most affected by HVPTLs, with the LPI values decreasing by 44.1 and 20.8%, respectively. The values of MESH decreased by 44.2 and 32.2%, respectively. We found an obvious increasing trend in the values of the normalized difference vegetation index (NDVI) in 2016 and NDVI growth during the period of 2007 to 2016 with an increase in the distance from HVPTL. The turning points of stability were 60 to 90 meters for HVPTL corridors and 90 to 150 meters for HVPTL pylons, which indicates that the pylons have a much greater impact on NDVI and its growth than the lines. Our research provides valuable suggestions for vegetation protection, restoration, and wildfire management after the construction of HVPTLs.

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