Medium Voltage Power Lines Research Articles

A swin transformer based bird nest detection approach with unmanned aerial vehicle images for power distribution and pole towers

AbstractThe authors propose a novel object detection algorithm for identifying bird nests in medium voltage power line aerial images, which is crucial for ensuring the safe operation of the power grid. The algorithm utilises an improved Swin Transformer as the main feature extraction network of Fast R‐CNN, further enhanced with a channel attention and modified binary self‐attention mechanism to improve the feature representation ability. The proposed algorithm is evaluated on a newly constructed image dataset of medium voltage transmission lines containing bird nests, which are annotated and classified. Experimental results show that the proposed algorithm achieves satisfied accuracy and robustness in recognising bird nests compared to traditional algorithms.

Hybrid steel–composite cross-arm for distribution power lines

This paper describes the development of electrically insulating hybrid steel–composite cross-arm for medium-voltage overhead distribution power lines with three conductors. The main goal was to achieve substantial weight savings compared to a common steel cross-arm with three ceramic insulators widely used in the Czech Republic. The structure has been designed as a combination of two main composite components – a pultruded horizontal profile and a braided vertical conical tube. These components are connected by a steel locking component which also serves for attaching the whole cross-arm to common concrete utility poles. The hybrid cross-arm is conceived to insulate electrical current in the default configuration thanks to the properties of the glass fiber reinforced composite materials, yet additional insulating elements can be used to further increase the electrical insulation distance. The materials and components used for the construction are chosen by combining finite element simulations of mechanical and electrical behavior with experimental testing and verification of important characteristics on selected substructures. The final design of the cross-arm is then manufactured and subjected to long-term testing in real-life environmental conditions. The achieved reduction of weight exceeds 50% while maintaining the mechanical rigidity and strength of the steel solution as well as the required insulation properties. The future trend of the cross-arm development is aiming at the weight reduction and increase of manipulation capabilities resulting in lowering many additional costs. In this work the designed cross-arm has half the weight of the original one.

An electric-field high energy harvester from medium or high voltage power line with parallel line

Abstract In order to effectively monitor transmission lines and transmission towers, a number of different types of sensors are needed. A lot of times, these sensors along with the transmission lines and transmission towers are in inaccessible or hard-to-access areas and replacing their batteries is difficult. Yet they need consistent power supply. By harvesting energy directly from these medium and high voltage power lines, these devices can become self-sustaining while the overall system is more friendly to the environment. This paper presents a novel approach to high energy harvesting based on capacitive coupling between the power line and the harvesting line. This technique has several advantages, namely high output voltage, easy adjustment of coupling coefficient, and low cost. The validation and implantation of this harvesting system are proposed with the support of experimental results. This energy-harvesting ability of W and mA levels is achieved for the power line monitoring devices, with higher power output depending on the length and the size of the harvesting line.

Problems Related to Selected Methods and Techniques of as-Built Surveys of Low- and Medium-Voltage Electricity Connectors with a Practical Discussion

Abstract The aim of the paper was to analyse problems related to the inventory (as-built survey) of low and medium voltage power lines. Measurement methods and techniques were analysed as well as the influence of the network type (low and medium voltage) on the as-built survey procedure. For this purpose, information obtained from five as-built survey reports of medium and low voltage using different measurement methods was also used. Three of them were sample as-built survey of low voltage cable lines measured by tacheometric method, one as-built survey of medium and low voltage lines measured by GNSS method and one of low voltage cable made by indirect method using cable locator and measured by GNSS technology. The paper analyses the differences arising from the accuracy of the measurement, the difficulties encountered during the implementation, the time-consuming nature of the work performed, taking into account safety aspects for the persons performing the work.

Electrocution Mortality of Imperial Eagle on Medium Voltage Power Lines in Slovakia

Medium-voltage power lines are one of the most important mortality factors of raptors in Slovakia. Among the frequent victims of electrocution are also rare species, such as the Imperial Eagle (Aquila heliaca). Many of the breeding pairs have gradually relocated from the foothills to nearby agrocenoses, with a higher risk of possible electrocution, as they often use the poles for resting. In Slovakia, the problem of electrocution has been the focus for mitigation measures since 1991. Especially the LIFE Energy project (implemented in 2014–2019) brought new insight into this topic, as systematic monitoring of almost 61,000 medium voltage poles was carried out in 2014–2016. Electrocution was defined as the main mortality factor of cadavers found. Almost 80% (2,992 individuals, 35 species) of all identified carcasses (4,353 individuals, 84 species) died as a result of electrocution. Branch and anchor supports and poles with jumpers above the insulators were the most dangerous configuration, accounting for 34.72% of total recorded electrocution fatalities (0.22 carcasses per pole). Systematic monitoring of the Imperial Eagle population has been carried out since 1977, when the abundance of the breeding population was 2–10 breeding pairs. After 2000, the settlement of the lowlands and the associated gradual increase in the breeding population were recorded, facilitated by targeted conservation measures. In 2022, the population reached 90 breeding pairs with 108 fledged nestlings in Slovakia. For the period 1993–2022, a total of 28 cases of Imperial Eagle mortalities were recorded in Slovakia. More extensive monitoring was carried out within the LIFE Energy project (2014–2019) when 16 victims were found, for the other years these are random cases. Therefore, the presented numbers do not reflect the actual mortality rate of the Imperial Eagle on 22 kV lines in Slovakia. The mortalities of individuals were mainly located below the most frequent types of the support poles with pin-type insulators. A serious problem was often observed especially for juveniles and inexperienced individuals during their first flights, landings and take-offs. Lowest mortality risk was identified for measures that allow birds to perch safely on the crossarm in comparison to antiperching elements. Therefore, the grid operators started to prefer the use of supports with safe crossarm configurations (for newly constructed lines) or insulating materials and elements that reflect these findings. The 22 kV medium voltage lines consist of thousands of supporting poles. It is therefore important to set the priority areas (breeding territories, feeding areas, etc.) where the main efforts should be focused primarily. This approach is fully implemented within the cooperation between Raptor Protection of Slovakia and DSOs in Slovakia, and also under project LIFE Danube Free Sky, under which 800 most dangerous poles will be safe for birds. Project is supported by the European Commission under the LIFE programme and the Ministry of the Environment of the Slovak Republic. Satellite transmitters installed on juveniles also help in the identification of priority poles and also bring new insights into the mortality rate (one from six tagged juveniles in 2022 died as a result of electrocution). Prevention of electrocution is especially important in the case of imperial eagle, as the loss of even one individual can have a negative impact on the viability of the local population. Therefore, many identified risky poles are insulated by DSOs on an ad hoc basis. In Slovakia, the protection of wild bird species in relation to their mortality on power lines is required by the national legislation. Only approved protective elements and crossarm designs that have undergone a risk assessment process can be applied. An important aspect of raptor conservation is the communication, mutual trust, and sharing of up-to-date knowledge between all relevant stakeholders.

Новые данные по гнездовой биологии, экологии и состоянию популяции орлана-белохвоста в Дагестане, Россия

Новые данные по гнездовой биологии, экологии и состоянию популяции орлана-белохвоста в Дагестане, Россия

Energy Harvesting Methods for Transmission Lines: A Comprehensive Review

Humanity faces important challenges concerning the optimal use, security, and availability of energy systems, particularly electrical power systems and transmission lines. In this context, data-driven predictive maintenance plans make it possible to increase the safety, stability, reliability, and availability of electrical power systems. In contrast, strategies such as dynamic line rating (DLR) make it possible to optimize the use of power lines. However, these approaches require developing monitoring plans based on acquiring electrical data in real-time using different types of wireless sensors placed in strategic locations. Due to the specific conditions of the transmission lines, e.g., high electric and magnetic fields, this a challenging problem, aggravated by the harsh outdoor environments where power lines are built. Such sensors must also incorporate an energy harvesting (EH) unit that supplies the necessary electronics. Therefore, the EH unit plays a key role, so when designing such electronic systems, care must be taken to select the most suitable EH technology, which is currently evolving rapidly. This work reviews and analyzes the state-of-the-art technology for EH focused on transmission lines, as it is an area with enormous potential for expansion. In addition to recent advances, it also discusses the research needs and challenges that need to be addressed. Despite the importance of this topic, there is still much to investigate, as this area is still in its infancy. Although EH systems for transmission lines are reviewed, many other applications could potentially benefit from introducing wireless sensors with EH capabilities, such as power transformers, distribution switches, or low- and medium-voltage power lines, among others.

Procedure for Verifying Population Exposure Limits to the Magnetic Field from Double-Circuit Overhead Power Lines

The verification of the limits of the population’s exposure to the magnetic field generated by double-circuit power lines from field measurements carried out on site is not trivial. It requires knowledge of the power line current instant values during the measurement period, the determination of the relationship between current and field at the measurement points (made more complex by the double-circuit overhead line configuration) and the use of that relationship to extrapolate the field values. Nevertheless, the verification of exposure limits for double-circuit power lines from on-site measurements is often conducted with rough, or not particularly stringent, procedures. A practical and straightforward procedure of general validity for non-optimized double-circuit lines is proposed here. No specific measurement position or conductors disposition knowledge is required as well as no complex three-dimensional finite element method code is necessary. The procedure, potentially also applicable to high- and extra-high-voltage lines, is validated on a medium-voltage (15 kV) double-circuit overhead power line study case. Exposure limits assessment suggests that if the line is operated at its rated capacity (230/285 A), the 3 μT quality target is missed. Results are provided with a 95% confidence interval ranging from ±100 nT to ±140 nT in all the cases.

A load switching intelligent sensing system based on medium voltage carrier communication device

As the core line of distribution network load transmission, 10kV medium voltage power line can reduce line loss to a great extent. However, the current situation of the power grid is that the basic information of 10kV line is disordered and the relationship between line changes is fuzzy, which leads to unbalanced load and high line loss rate. At present, the solution is the traditional way such as manual line inspection and power drawing discrimination, which has poor timeliness, low accuracy and the risk of potential personnel injury. In this paper, a load switching intelligent sensing system based on medium voltage carrier communication devicewe is discussed. By using the unique physical line of 10kV medium voltage line to transmit the characteristic sequence signal, the relationship between line changes can be accurately identified in real time, and the load switching intelligent sensing system can make the 10kV medium voltage power line in the optimal load distribution, reduce the line loss and effectively reduce the loss of electric energy.

Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current

Settings of protection are essential to ensure the sensitivity and selectivity needed to detect defects. Making the correct settings requires the calculation of the fault currents with as little error as possible. Fault currents are influenced by the parameters of the electrical networks, including the state of the insulation and the Petersen coil, which changes during their operation electrical networks. This paper analyzes how the insulation parameters of medium voltage power lines, the parameters of the Petersen coil used to treat the neutral of the medium voltage electrical network and the value of the resistance at the fault location influence the fault current in the case of a single-phase fault. The large number of single-phase faults that occur in medium voltage electrical networks justifies this analysis. The symmetrical components method was used to calculate the fault current. The results obtained by calculation were verified experimentally by causing a single-phase-to-ground fault in a real medium voltage network. The paper presents the situations in which the analytical calculation of the single-phase-to-ground fault current can lead to inadmissibly large errors, even over 50%, but also the situations in which the errors fall below 3%.

Measurements and characterisation of low and medium voltage residential, commercial, and industrial NB‐PLC networks for AMI

This study investigates the feasibility of advanced metering infrastructure (AMI) based on narrowband power line communications (NB-PLC) by incorporating all possible types of low voltage (LV) and medium voltage (MV) power line channels. The extensive field measurements are carried out on six selected sites that include residential, commercial, and industrial LV and MV NB-PLC channels. On the basis of measured results, NB-PLC channels of various under evaluation sites are segregated into two classes i.e. worst and good channels for both LV and MV networks. The simulation models for the modelling of LV and MV NB-PLC channels by considering the practical data of measured sites are developed and thus proposed. The proposed methods are validated by comparing the measured and simulated results. A sophisticated mechanism for the modelling of LV and MV network impedances and capacitive coupling device is formulated. The proposed analyses and simulation-based NB-PLC channel models can play a key role in examining the characteristics of various types of NB-PLC channels. This research work will help to standardise the future smart metering equipment and sensing devices of power system protection.

Prediction of power cables failures using a software application

This paper analyses the electrical performance of power supply cables in operation by investigating previous faults and forecasting faults using the Easyfit Professional 5.6 software program. The calculation of the maximum operating time until the first fault occurs is based on an algorithm for estimating the parameters entered in the application, respectively the intervals of good operation time between two successive faults. The case study presented in the paper analyses the probability of failure of a medium voltage power line, under the administration of a distribution operator, based on information collected during maintenance work on medium and low voltage installations in the analysed area.

Lightning protection of a multi-circuit HV-MV overhead line

This paper deals with the assessment of the lightning performance of a medium voltage (MV) power line sharing the same poles of a high voltage (HV) line. We focus on the case of a 15-kV line with compact configuration that is supported by the concrete poles of a 69-kV or a 138-kV transmission line. Due to the taller HV pylons and conductors, the number of direct events to the multi-circuit line is higher than for a MV line alone. The presence of the HV conductors and of the overhead ground wire reduces the amplitudes of the induced overvoltages in the MV conductors due to indirect lightning events. For the considered configurations, with a compact MV line, the number of flashovers per year expected in the double-circuit line due to both direct and indirect flashes is lower than in a MV line alone. It is shown that such a number depends mainly on the line withstand voltage, on the grounding resistance and on the number of surge arresters. The dependence is quantitatively discussed in the paper. The analysis of the overvoltages transferred on the LV side of the distribution transformers is also performed.

Bird mortality on medium-voltage power lines in the Czech Republic

Abstract In 2015–2016, 6,429 km medium-voltage power lines with 76,430 pylons were checked for bird mortality in the Czech Republic. 1,326 bird victims of power lines were found, 156 of which died after collisions, and 1,170 birds were electrocuted. They belonged to 60 species from 12 orders, and birds of prey made up almost half of all victims. Steel pylons bearing several cross-arms including upper and crosswise jumpers were identified as most dangerous from the electrocution point of view. On the other hand, pylons in straight lines with Pařát cross-arms (triangular arrangement of conductors without any horizontal bar) were among the least dangerous, and when they had a simple perch fitted below the cross-arm, no mortality was recorded. But these pylons are new in practice and despite becoming widely used recently, they form less than one tenth of all pylons in the Czech Republic. On other pylons various types of mitigation measures have been installed. Commonly used plastic covers and plastic strips have proved to be especially effective, but only in cases when they are undamaged and correctly installed.

Research on Improving the Success Rate of Electricity Information Acquisition System by Using Medium Voltage Power Line Carrier Communication Technology

This paper studies the application of medium voltage power line carrier in Electricity Information Acquisition System, discusses the main application scenarios of medium voltage power line carrier, compares three upstream communication modes of medium voltage power line carrier, optical fiber and wireless public network, and summarizes the investment cost, construction and maintenance of medium voltage power line carrier. The field operation proves that the medium voltage carrier communication technology can improve the success rate of Electricity Information Acquisition System.

Optimization techniques for determining the section and the economic current density of medium and low voltage power lines

In most situations encountered in practice, the choice of section of the overhead or cable lines is made on the basis of the economic criterion in normal operating mode, which is the basic criterion for sizing. The central theme of this paper is the optimization of the section and the economic current density in the medium and low voltage power lines. The first part presents the calculation mathematical model for the determination of the optimal section and the economic current density for the medium and low voltage electric lines, and the section obtained has to be verified based on the criteria of the maximum admitted voltage drop and the mechanical resistance. The case studies presented reflect the results of the corresponding voltage drop in the case of an electric line portion through which a load unit is transmitted, respectively the power corresponding to the optimal cross section and the maximum voltage drop allowed for a medium voltage overhead line.

A New Coupling Solution for G3-PLC Employment in MV Smart Grids

This paper proposes a new coupling solution for transmitting narrowband multicarrier power line communication (PLC) signals over medium voltage (MV) power lines. The proposed system is based on an innovative PLC coupling principle, patented by the authors, which exploits the capacitive divider embedded in voltage detecting systems (VDS) already installed inside the MV switchboard. Thus, no dedicated couplers have to be installed and no switchboard modifications or energy interruptions are needed. This allows a significant cost reduction of MV PLC implementation. A first prototype of the proposed coupling system was presented in previous papers: it had a 15 kHz bandwidth useful to couple single carrier PSK modulated PLC signals with a center frequency from 50–200 kHz. In this paper, a new prototype is developed with a larger bandwidth, up to 164 kHz, thus allowing to couple multicarrier G3-PLC signals using orthogonal frequency division multiplexing (OFDM) digital modulation. This modulation ensures a more robust communication even in harsh power line channels. In the paper, the new coupling system design is described in detail. A new procedure is presented for tuning the coupling system parameters at first installation in a generic MV switchboard. Finally, laboratory and in-field experimental test results are reported and discussed. The coupling performances are evaluated measuring the throughput and success rate in the case of both 18 and 36 subcarriers, in one of the different tone masks standardized for the FCC-above CENELEC band (that is, from 154.6875–487.5 kHz). The experimental results show an efficient behavior of the proposed coupler allowing a two-way communication of G3-PLC OFDM signals on MV networks.

Notice of Retraction: The Bounded Phase Property of the Time-Reversal Current Transfer Function for the Locations of Longitudinal Defects in Transmission Lines

This paper analytically demonstrates that the boun-ded phase property of the voltage transfer function developed by Codino for the electromagnetic time-reversal method in unmatched media is also valid for the time-reversal current transfer function used as an estimator of the location along the line of soft defects with defect impedance different from zero. Few examples are proposed ranging from medium-voltage power lines to high-speed interconnects, which demonstrate the accuracy and scalability of the method.

Notice of Retraction: Impact of Frequency-Dependent Terminations and Defect Impedances on the Accuracy of the Unmatched-Media Time Reversal Method

In this paper, the analysis of the accuracy of the electromagnetic time reversal method for unmatched media is carried out when the terminal impedances of the transmission line and/or of the defects along it are frequency dependent. Some numerical examples involving a medium-voltage power line and a high-speed interconnect are considered and the results discussed.

Evolving neuro-fuzzy network for real-time high impedance fault detection and classification

This paper concerns the application of a neuro-fuzzy learning method based on data streams for high impedance fault (HIF) detection in medium-voltage power lines. A wavelet-packet-transform-based feature extraction method combined with a variation of evolving neuro-fuzzy network with fluctuating thresholds is considered for recognition of spatial–temporal patterns in the data. Wavelet families such as Haar, Symlet, Daubechie, Coiflet and Biorthogonal were investigated as a way to provide the most discriminative features for fault detection. The proposed evolving neuro-fuzzy classification model has shown to be particularly suitable for the problem because the HIF environment is subject to concept changes. Different from other statistical and intelligent approaches to the problem, the developed neuro-fuzzy model for HIF classification is not only parametrically, but also structurally adaptive to cope with nonstationarities and novelties. New neurons and connections are incrementally added to the neuro-fuzzy network when necessary for the identification of new patterns, such as faults and usual transients including sag, swell and spikes due to the switching of 3-phase capacitors and energization of transformers. Experimental evaluations compare the proposed classifier with other well-established computational intelligence methods, viz. multilayer perceptron neural network, learning vector quantization neural network and a support vector machine model. Results have shown that the evolving neuro-fuzzy system is effective and robust to changes. The system is able to maintain its detection and classification accuracy even in situations in which other classifiers exhibit a significant drop in accuracy due to gradual and abrupt changes of the fault patterns. Fuzzy rules are useful for interpretability purposes and help to enhance model credibility for decision making.