Dynamic capacity rating for wind cooled overhead lines

When the distance between an obstacle and a power line is less than the discharge distance, a discharge arc can be generated, resulting in the interruption of power supplies. Therefore, regular safety inspections are necessary to ensure the safe operation of power grids. Tall vegetation and buildings are the key factors threatening the safe operation of extra high voltage transmission lines within a power line corridor. Manual or laser intensity direction and ranging (LiDAR) based inspections are time consuming and expensive. To make safety inspections more efficient and flexible, a low-altitude unmanned aerial vehicle (UAV) remote-sensing platform, equipped with an optical digital camera, was used to inspect power line corridors. We propose a semi-patch matching algorithm based on epipolar constraints, using both the correlation coefficient (CC) and the shape of its curve to extract three dimensional (3D) point clouds for a power line corridor. We use a stereo image pair from inter-strip to improve power line measurement accuracy by transforming the power line direction to an approximately perpendicular to epipolar line. The distance between the power lines and the 3D point cloud is taken as a criterion for locating obstacles within the power line corridor automatically. Experimental results show that our proposed method is a reliable, cost effective, and applicable way for practical power line inspection and can locate obstacles within the power line corridor with accuracy better than ±0.5 m.

The maintenance of high-voltage power lines rights-of-way due to vegetation intrusions is important for electric power distribution companies for safe and secure delivery of electricity. However, the monitoring becomes more challenging if power line corridor (PLC) exists in complex environment such as mountainous terrains or forests. To overcome these challenges, this paper aims to provide an automated method for extraction of individual pylons and monitoring of vegetation near the PLC in hilly terrain. The proposed method starts off by dividing the large dataset into small manageable datasets. A voxel grid is formed on each dataset to separate power lines from pylons and vegetation. The power line points are converted into a binary image to get the individual spans. These span points are used to find nearby vegetation and pylon points and individual pylons and vegetation are further separated using a statistical analysis. Finally, the height and location of extracted vegetation with reference to power lines are estimated and separated into danger and clearance zones. The experiment on two large Australian datasets shows that the proposed method provides high completeness and correctness of 96.5% and 99% for pylons, respectively. Moreover, the growing vegetation beneath and around the PLC that can harm the power lines is identified.

Due mainly to changes in land use, high nature value grasslands are becoming increasingly rare in agricultural areas. As a consequence, biodiversity is decreasing and many species are facing the risk of extinction. At the same time, the present‐day landscape contains many “new” grassland habitats, for example golf courses, roadside verges, power line corridors, and railway banks. These habitats are well distributed over the landscape with a potential to connect remnant patches of valuable grasslands. As all kinds of grasslands, they need appropriate management to preserve biodiversity. To achieve this, innovative solutions are needed. In order to exchange knowledge and experiences in this field, we established a cross‐disciplinary working group, with members from a large number of National authorities, Universities, power grid companies, and various other stakeholders such as the Swedish Golf Federation. This group has become an invaluable forum for project cooperation and discussions about practical management issues, monitoring, and research. After 10 years we are now approaching a common understanding on how infrastructure habitats can play an important role in nature conservation. At present, this has led to adaptive management of a large number of high value grasslands, for example in power line corridors, along roadside verges, and on golf courses. In addition, three landscape‐scale projects have been initiated with the long‐term aim to establish a green infrastructure.

The authors of [1] confirm our standpoint presented in [2] concerning the hazard of induced voltage arising from the ground fault in inducing overhead lines (OL). They agree that it is necessary to determine the maximum ground-fault voltage in a network of inducing OL and reduce the induced voltage to a permissible level using terminal and intermediate OL groundings; they also suggest methods of protection from induced voltage at the repair site. They also question the correctness of the OL inducedvoltage grounding technique recommended in [3] (item 4.3.11), which has been included in the new edition of Safety Regulations [4] (items 4.15.52 – 4.15.54) with the only exception that the maximum induced-voltage potential is taken to be 25 V rather than 42 V. The criticism in [3] seems to be valid to the extent that the Safety Regulations (SR) for electric plants fail to specify requirements to the grounding device at the repair site (for an OL grounded at a single point only). On the other hand, it has been argued repeatedly [2, 5] that the single-point grounding should be installed with allowance for the voltage drop associated with the capacitive component of the ground current. It was further argued that the OL single-point grounding using a ground rod with a length of 0.5 m (the technique accepted by SR, item 3.6.8 [4]) develops a voltage that may be hazardous to human health. We believe that the reasons in [1] are quite interesting and should be taken into account when dealing with 330 kV OLs or higher; however, expanding them on all OLs and OL networks under induced voltage will be problematic. In view of the aforementioned, we reiterate that the OL induced-voltage grounding at a single point (at the repair site) is a simple and sufficiently effective means of protection from the electromagnetic component (including ground-fault situations). Protection of the personnel of electric power plants from the electrostatic component of induced voltage is effected by grounding devices of low resistance (grounding wire for 110 kV OL supports, rods for 220 kV (and higher) steel and concrete OL supports, grounding circuits, and special grounding devices for 6 – 10 kV OLs). The capacitive ground current can roughly be estimated using formulas given in [1] or in [4]; based on these data it is possible to determine the safe ground resistance at the repair site. In compliance with the new SR requirements for which the permissible grounding voltage is 25 V (formerly, 42 V), re-evaluated data in [5] for 110 and 220 V twin OLs can be used for practical purposes: safety conditions are reached using a single grounding with R < 30 U per 60 km for a 110 kV OL and per 30 km for a 220 kV OL. To check for safety, the grounding voltage should necessarily be measured at the repair site; this voltage should not exceed the rated value of 25 V. The technique for measuring the grounding voltage is rather simple, and the necessary measurements can readily be accomplished by the repair team at the working site [6]. The single-point grounding technique for induced-voltage OLs can in principle be applied to overhead lines. The use of this technique prevents the discharge of potential from the substation circuit to the de-energized line (intended for repair) through the grounding in emergency short-circuit situations at the substation or in a connected network (110 or 220 kV). Such situations are not uncommon (at the relatively high failure rate of support porcelain insulators for 110 and 220 kV disconnecting switches or actuation of short circuiters). As required by the SR, to prevent the OL under repair from being accidentally energized (or from the discharge of potential from the substation circuit), the grounding at the substation should be installed before the line-disconnecting switch as viewed from the substation. The single-point grounding (rather than the terminal grounding or on-site grounding) is less effective in the case of a “galvanic effect” produced by the accidental contact with a traversing OL. Such accidental effects are disastrous for any OL grounding scheme; however, accidents of this kind are highly unlikely if the appropriate construction-and-use regulations for electric power plants and electric power lines are strictly observed. It should be noted that in certain situations where the induced voltage is difficult to reduce using conventional grounding schemes (terminal grounding and on-site ground-

Power line mapping technique using all-terrain mobile laser scanning

In the last decade, dynamic line rating (DLR) as a novel and cost-effective transfer capacity calculation method has been getting into the scope of transmission system operators (TSOs). By applying DLR method, it is possible to increase the ampacity of the overhead lines (OHLs) averagely in 95% of the time based on the monitoring of the actual weather conditions in the vicinity of the conductors. On the other hand, one important pillar during the application of this method - from the aspect of the TSOs - is the day-ahead transfer capacity prediction for the determination of generation schedules, which requires accurate weather forecast. By using accurate weather parameters as an input of DLR models, there is no sag violation at the maximum allowable conductor temperature. Otherwise, getting precise weather forecast is almost impossible; this affects the sag and, in this way, the whole DLR method. The aim of this article is to present how sag and clearance of the OHL spans change due to weather forecast uncertainties. For the simulations, field data from an OHL equipped with line monitoring sensors and weather stations are applied. Sag-clearance monitoring is also an important aspect in case of DLR applications regarding to the electric and magnetic field strength and distribution. Because of the potential threat for general public and occupational personnel, monitoring of sag increment might be an important aspect in the state of the art DLR related researches.

Wildfires pose a significant threat to power line infrastructure, potentially causing large-scale power outages and severe economic and environmental damage. Early and accurate detection of wildfires within power line corridors is critical for enabling timely intervention and mitigating risks. In this paper, we propose an intelligent wildfire detection system based on the state-of-the-art YOLOv10 object detection algorithm. Leveraging UAV-acquired imagery and real-time edge processing, the system is designed to detect wildfire occurrences with high speed and precision in complex outdoor environments. Compared to traditional image classification and older detection networks, YOLOv10 offers enhanced performance in terms of detection accuracy, computational efficiency, and robustness under varying lighting and background conditions. We construct a wildfire detection dataset specific to power line corridors and perform extensive experiments to evaluate the model. The results demonstrate that the proposed method achieves a mean Average Precision (mAP) of 89.6%, with an inference time of 11.3 ms per frame, significantly outperforming previous YOLO versions and lightweight detection models.

Characterization and modeling of power line corridor elements from LiDAR point clouds

The electricity transmission, gas transmission, and railway industries have developed various methods for the calculation of voltages induced in infrastructure following power line corridors. These tools are typically based on simplified topologies and assumptions that make the implementation of the required algorithms more tractable and data entry screens more alluring. On the other hand, such an approach suffers from reduced accuracy, due to the required simplifying assumptions, and furthermore excludes the possibility of studying complex systems for which the designer is unable to determine what simplifying approximations are the most appropriate. In the absence of confidence in his or her calculations, the designer tends to be overly conservative, resulting in excessive mitigation. This situation arises in particular when the system includes buried components whose through-earth coupling interactions are significant. This paper illustrates this point with a case study and parametric analysis, showing how a calculation based on integrated electromagnetic field modeling results in a more accurate assessment of interference levels and therefore more suitable mitigation.

We live in an urbanizing world. Since 2008, more than half of humanity lives in cities, both large and small, and old and new.[...]

Disperse or die: Colonisation of transient open habitats in production forests is only weakly dispersal-limited in butterflies

Insects have been losing their habitats with the rapid expansion of many urban cities such as Toronto. This study aims at understanding the dispersal patterns insects take once they are placed under a heavy amount of disturbance. The use of power line corridors allows us to have a disturbance gradient within an urban city that allows us to observe the normal distribution of insects across the gradient and compare it to how their distribution patterns change once a disturbance has been applied. It is important in understanding insect dispersal patterns, because only then can we accurately create conservation strategies, and plan urban development to minimize the amount of damage done to insect populations. In this study, sweep nets, pan traps, and point counts were used to sample five areas of a disturbance gradient along a power line corridor. The experiment was conducted over three weeks and it was found that the gradient studied followed a quadratic distribution pattern predicted by the intermediate disturbance hypothesis, although with the application of disturbance, the insects diapered into an exponential type pattern in which the greatest abundance of insects were found in the area of least disturbance. The findings of this study have important implications in understanding the effects of disturbance on insects in urban ecosystems and are a step in the direction of forming a unified theory of insect/disturbance dynamics.

Eastern Hognose Snakes (Heterodon platirhinos) are considered a species of conservation concern in the northeast United States because of their association with rare and declining habitats such as pine barrens and shrublands. These are disturbance-dependent habitats that currently require management to persist. We studied Eastern Hognose Snakes on a pitch pine–scrub oak barren in western Massachusetts from 2008 to 2013 to describe patterns of space use, habitat selection, and survival of this species and to evaluate the effects of habitat restoration and fuels management. We monitored 12 snakes with radio telemetry during the months of May to October 2008–2010. We examined habitat use versus availability using paired logistic regression analyses in which availability was temporally and spatially explicit in relation to radio-tracked snakes' previous use location and likely movements. We found that radio-tracked snakes significantly avoided closed-canopy forests and power line corridors, and inste...

The purpose of this research is to analyze and improve the technical approaches to designing overhead power lines with self-supporting insulated conductors during the transition from bare conductors in low- and medium-voltage networks. The applied methods include analytical evaluation of mechanical and climatic loads using the limit state design approach, comparative assessment of conductor sizing methods based on economic current density and economic current intervals, and modeling of lightning impact using simplified expressions for critical lightning current and insulator flashover probability. The results show that enhancing the reliability and electrical safety of overhead lines requires detailed consideration of the predominance of horizontal loads over vertical ones, the influence of wind pressure, conductor and ground wire weight, insulators and mounting equipment on the dimensions of supports and foundations. The study examines the selection of conductor cross-sections in overhead and cable lines, verifying thermal limits and voltage drop for various voltage levels and network configurations. Particular attention is paid to sizing phase conductors of self-supporting insulated cables considering allowable operating temperatures of thermoplastic and cross-linked polyethylene insulation, the annual duration of maximum load, mechanical strength, and voltage drop constraints. The main lightning impact scenarios are analyzed, including shielding failure, direct lightning strokes to the tower with back-flashover, and lightning strokes to the shield wire in mid-span causing flashover of the shield-to-phase air gap. The research confirms the importance of tower height, grounding resistance, and the inductances of the tower and shield wire for evaluating lightning performance. Structural and technological aspects of erecting insulated overhead lines are presented, including standardization of concrete and steel poles, methods of pole footing in various soils, installation of hooks and cross-arms, conductor stringing using running blocks, pilot ropes and pulling grips, and compression joints for phase conductors. The role of nonlinear metal-oxide surge arresters as a primary means of protecting equipment and insulation in the voltage range from 0.38 to 110 kV is substantiated; the requirements for environmental resistance, pollution performance, mechanical strength, and design of polymeric and porcelain-housed arresters are summarized. The conclusions emphasize that the coordinated use of structural design methods, conductor sizing techniques, lightning protection systems and modern erection technologies significantly increases the reliability, operational safety and energy efficiency of overhead lines employing self-supporting insulated conductors.

Dynamic Line Rating (hereinafter referred to as DLR) is an effective grid management method for transmission system operators (TSOs). It provides solution for the demand of the increasing transmission capacity and for cost-effective network development at the same time. By the application of special temperature sensors, weather stations and proper DLR models the ampacity of the overhead lines (OHLs) could be increased significantly in the 95% of the time. In the existing DLR models several aspects of the implementation are taken into account and in addition to technological realization there are also references which discuss the economic side of this method. Another important question is that in case of DLR application what extent of a direct impact of the increased current load has on the emerging magnetic field, and how affects the electric field in the vicinity of the OHLs indirectly. Although this consequence of DLR can be a risk to human life, it has not been investigated, yet. According to this, researches on this issue can make the application of DLR safer, or occasionally impose restrictions on the application of this method.