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The inspection of overhead power transmission lines is of the utmost importance to ensure the power network's uninterrupted, safe, and reliable operation. The increased demand for frequent inspections implementing efficient and cost-effective methods has emerged, since conventional manual inspections are highly inaccurate, time-consuming, and costly and have geographical and weather restrictions. Unmanned Aerial Vehicles are a promising solution for managing automatic inspections of power transmission networks. The project "ALTITUDE (Automatic Aerial Network Inspection using Drones and Machine Learning)" has been developed to automatically inspect the power transmission network of Lesvos Island in Greece. The project combines drones, 5G data transmission, and state-of-the-art machine learning algorithms to replicate the power transmission inspection process using high-resolution UAV data. This paper introduces the ALTITUDE platform, created within the frame of the ALTITUDE project. The platform is a web-based, responsive Geographic Information System (GIS) that allows registered users to upload bespoke drone imagery of medium-voltage structures fed into a deep learning algorithm for detecting defects, which can be either exported as report spreadsheets or viewed on a map. Multiple experiments have been carried out to train artificial intelligence (AI) algorithms to detect faults automatically. [ABSTRACT FROM AUTHOR]

Remotely performing real-time distributed generation control and a demand response is a basic aspect of the grid ancillary services provided by grid operators, both the transmission grid operators (TSOs) and distribution grid operators (DNOs), in order to ensure that voltage, frequency and power loads of the grid remain within safe limits. The stochastic production of electrical power to the grid from the distributed generators (DGs) from renewable energy sources (RES) in conjunction with the newly appeared stochastic demand consumers (i.e., electric vehicles) hardens the efforts of the DNOs to keep the grid's operation within safe limits and prevent cascading blackouts while staying in compliance with the SAIDI and SAIFI indices during repair and maintenance operations. Also taking into consideration the aging of the existing grid infrastructure, and making it more prone to failure year by year, it is yet of great significance for the DNOs to have access to real-time feedback from the grid's infrastructure—which is fast, has low-cost upgrade interventions, is easily deployed on the field and has a fast response potential—in order to be able to perform real-time grid management (RTGM). In this article, we present the development and deployment of a control system for DG units, with the potential to be installed easily to TSO's and DNO's substations, RES plants and consumers (i.e., charging stations of electric vehicles). This system supports a hybrid control mechanism, either via ripple signaling or through a network, with the latter providing real-time communication capabilities. The system can be easily installed on the electric components of the grid and can act as a gateway between the different vendors communication protocols of the installed electrical equipment. More specifically, a commercially available, low-cost board (Raspberry Pi) and a ripple control receiver are installed at the substation of a PV plant. The board communicates in real-time with a remote server (decision center) via a 5G modem and with the PV plants inverters via the Modbus protocol, which acquires energy production data and controls the output power of each inverter, while one of its digital inputs can be triggered by the ripple control receiver. The ripple control receiver receives on-demand signals with the HEDNO, triggering the digital input on the board. When the input is triggered, the board performs a predefined control command (i.e., lower the inverter's power output to 50%). The board can also receive control commands directly from the remote server. The remote server receives real-time feedback of the acquired inverter data, the control signals from the ripple control receiver and the state and outcome of each performed control command. [ABSTRACT FROM AUTHOR]

The influence of earth stratification on the conductor impedances is investigated in this paper. A general solution of the electromagnetic-field equations for the case of overhead and underground transmission-line conductors of arbitrary topology and multilayer earth is presented. Generalized expressions for the self and mutual impedances of the conductors are derived. All existing approaches result from the generalized equations, when the corresponding approximations are applied. A suitable integration scheme is also proposed for the calculation of the complex integrals involved in the expressions. Index Terms--Earth conduction, electromagnetic transient analysis, nonhomogeneous earth, transmission line modeling.

The influence of earth stratification on the conductor impedances is investigated in this paper. The generalized expressions for the self and mutual impedance of conductors in the multilayer earth case, which have been derived in a companion paper, are implemented on typical overhead power transmission lines and underground single-core power cable arrangements for discrete and exponential variations of earth resistivity. The accuracy of the results over a wide frequency range is justified by a proper finite-element method formulation. The differences in the impedances due to earth stratification are presented. The influence of the earth stratification on the actual transient responses of the conductor arrangements is also investigated. Index Terms--Electromagnetic transient analysis, finite-element method (FEM), nonhomogeneous earth, power cables, transmission-line modeling.

The homogenous earth representation of two-layer earth structures for earth return impedance calculations is investigated in this paper. This representation is based on equivalent resistivity, which takes properly into account the electromagnetic and the geometrical properties of the two earth layers. The equivalent resistivity can be used in the relatively simpler formulas for the earth return calculations for the case of homogenous earth. The new expression is implemented for six actual cases of two-layer earth structures involving combinations of overhead and underground conductors. Results show that the equivalent resistivity approach can lead to significant simplifications in most cases of switching transient simulations in the presence of two-layer earth structures. Index Terms--Electromagnetic transients analysis, nonhomogeneous earth, power cable modeling, power transmission-line impedance.

The influence of earth stratification on overhead power transmission line impedances is investigated in this paper. A systematic comparison of existing approaches is done, while results are also obtained using a finite-element method formulation. A novel numerical integration technique is proposed for the calculation of the infinite integrals involved. Typical single--and double-circuit line configurations are examined for a combination of layer depths and earth resistivities over a wide frequency range. The influence of the layer depth is also investigated. Results show significant differences from those, corresponding to the case of homogeneous earth. Using the multilayered earth return impedances in transient simulations, the transient responses show that differences occur mainly in cases of asymmetrical faults, justifying the need for a detailed earth model implementation. Index Terms--Electromagnetic transient analysis, finite element method, nonhomogeneous earth, power transmission lines.

The influence of earth stratification on underground power cable impedances is investigated in this paper. A rigorous solution of the electromagnetic field for the case of underground conductors and a two-layer earth is presented. Analytic expressions for the self and mutual impedances of the cable are derived. The involved semi-infinite integrals are calculated by a novel, numerically stable, and efficient integration scheme. Typical single-core cable arrangements are examined for a combination of layer depths and earth resistivities, based on actual measurements. The accuracy of the results over a wide frequency range is justified by a proper finite-element method formulation. The differences in cable impedances due to earth stratification are presented. Finally, a simple switching transient simulation is examined to evaluate the influence of the earth stratification on transient voltages and currents. Index Terms--Electromagnetic transient analysis, finite-element method (FEM), nonhomogeneous earth, power cable modeling.

The influence of earth stratification on overhead power transmission line impedances is investigated in this paper. A systematic comparison of existing approaches is done, while results are also obtained using a finite-element method formulation. A novel numerical integration technique is proposed for the calculation of the infinite integrals involved. Typical single- and double-circuit line configurations are examined for a combination of layer depths and earth resistivities over a wide frequency range. The influence of the layer depth is also investigated. Results show significant differences from those, corresponding to the case of homogeneous earth. Using the multilayered earth return impedances in transient simulations, the transient responses show that differences occur mainly in cases of asymmetrical faults, justifying the need for a detailed earth model implementation. [ABSTRACT FROM AUTHOR]