Lightning-Induced Voltages on Overhead Distribution Lines: Theoretical and Experimental Investigation of Related Problems and their Impact on Power Quality

Recent power quality studies have been focused on the source-identification of voltage disturbances at distribution network busses. This paper describes a method aimed at correlating indirect-lightning events with power systems relay operations, associated with voltage dips. The proposed method, based on the coordinated use of the Italian lightning location system CESI-SIRF, the Italian monitoring system of protection manoeuvres CESI-SAM, and the availability of an advanced simulation tool for the accurate simulation of lightning-induced voltages on complex power networks, namely the LIOVEMTP code, is applied to the real case of an Italian distribution system. The LIOV-EMTP code is also employed along with a statistical procedure based on the Monte Carlo method to carry out a statistical analysis aimed at assessing the lightning performance of a typical Italian distribution line

Partial Discharges detection in 1 MV power supplies in MITICA experiment, the ITER Heating Neutral Beam Injector prototype

MITICA (Megavolt ITER Injector & Concept Advancement), the full scale prototype of ITER Heating Neutral Beam, is under realization at the Neutral Beam Test Facility (Padova, Italy). It is designed to deliver 16.5 MW to ITER plasma, obtained by accelerating negative Deuterium ions up to 1 MeV for a total ion current of 40 A and then neutralized. MITICA Acceleration Power Supply is composed of several non-standard equipment, beyond industrial standard for insulation voltage level (-1 MVdc) and dimensions. Voltage withstand tests (up to 1.265 MVdc) have been performed in five subsequent steps (from 2018 to 2019), according to the installation progress, after connecting equipment belonging to different procurements. During integrated commissioning, started in 2021, two breakdowns occurred in a position of the HV plant not still identified, so they could be occurred either in air or in SF6. To identify the locations of possible weak insulation points, the existing diagnostics for partial discharge detection (the precursor of breakdowns) as a first step have been improved on air-insulated parts by consisting in a set of instrumentation, like capacitive probes and off-the-shelf instruments for AC application (acoustic and electromagnetic sensors). The paper deals with the instruments qualification to assess their suitability for DC usage and then with the investigation performed in MITICA, in particular: 1) sensitivity assessment campaign, with artificially produced corona effect to identify the minimum threshold of each diagnostics 2) voltage application to MITICA plant, moving the instrumentation around equipment and increasing progressively the voltage looking for corona phenomena to identify possible weak insulation points.Comment: Nine pages, twelve figures, accepted manuscript of a paper published in Fusion Engineering and Desig

Concept Design and Development of a Module for the construction of reversible HVDC submarine deep-water Sea Electrodes

Over the last years many HVDC (High Voltage Direct Current) links have been studied, commissioned and built. Among the constraints, one of the most important is the corrosion risk for surrounding submerged/buried metallic structures. When the coastal area is rich of metallic structures, corrosion risk may be unacceptable, requiring the relocation of the electrode at significant distance offshore. As seafloor at the selected location may be considerably deep, relevant issues about installation and maintenance must be addressed in the design phase. A modular electrode design, able to cope efficiently with all such requirements and minimizing the overall cost has been developed

Technical and compatibility issues in the design of HVDC sea electrodes

The HVDC (High Voltage Direct Current) transmission system, although in use since about half a century, is gaining new popularity in recent years, as it can allow to transmit very large amounts of power over long distance at reasonable costs. Many plants are being commissioned and many others are in the design phase, both for mainland and submarine links. Ground/sea electrodes are normally used in such applications, either operated on a full time basis, or during partial failures of one pole of bipolar plants. Due to the adverse effects that stray currents dispersed by such electrodes may have in terms of corrosion to nearby structures, and to the growing concern for environmental issues, the design of sea electrode has to be defined with increasing attention. This paper deals with the technologies and with the design criteria that can be adopted to develop satisfactory sea electrodes