Search results for " HVDC."

Space Charges and Partial Discharges Simultaneous Measurements under DC Stress

2016

In the field of HVDC, the main causes of insulation aging are due to the space charge and PD phenomena. In particular, the purpose of the present work is to verify a possibility to measure simultaneously the space charge and the PDs under DC stress in order to evaluate the correlation between both phenomena. The space charge was measured by using a modified PEA cell and PDs were measured by using a novel wireless sensor system. The space charge profile and the PD pulses carried out simultaneously have been reported and discussed.

Investigation on partial discharges in HVDC cables after polarity reversal events

2020

Due to the accumulation of space charge inside the insulating layer of HVDC cables, the electric field under load conditions may be altered compared to what is established in HVAC cables. For example, a high thermal gradient leads to the inversion of the electric field pattern until the maximum value is reached in proximity of the dielectric-semicon interfaces. These maximum values can be further increased due to transient overvoltages and polarity reversal events until reaching electric field values higher than the rated ones. The main goal of this research is to investigate the possibility that, during these transient phenomena, conditions are created that favor the occurrence of partial …

The effect of the axial heat transfer on space charge accumulation phenomena in HVDC cables

2020

To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating …

Time Evolution of Partial Discharges in a Dielectric Subjected to the DC Periodic Voltage

2022

Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new …

AN ACCURATE MODEL FOR STEADY-STATE AND DYNAMIC ANALYSIS OF THE SICILIAN NETWORK WITH HVDC INTERCONNECTIONS

2021

Sicily is one of the first Italian regions for installed power from renewable energy plants, especially photovoltaic and wind plants, and a crucial point for the Mediterranean energy hub. Its role as nexus between the European and the African Continents is becoming more and more significant due to the realization in a short time of the so called Tyrrhenian link and the High Voltage Direct Current (HVDC) connection with Tunisia. In this framework, the paper presents a model of the Sicily power generation and transmission system, including the Tyrrhenian link and two equivalent buses representing the Sardinian power network and the rest of the Continental Europe (CE) synchronous area, for both …

Modelling of Pulsed Electro Acoustic Method for Space Charge Detection on Single and Multilayer Dielectrics

Reliability of PEA Measurement in Presence of an Air Void Defect

2020

This paper deals with the reliability of the Pulsed Electro-Acoustic (PEA) technique in the case of a specimen containing an air layer. The first approach to this study has been proposed by the authors in previously published works. In these papers, the mathematical description, the PEA cell simulation model, and some experimental tests have been reported. In this work, a more accurate description of the acoustic wave behavior within the PEA cell and specimen with and without an air layer is given. Moreover, the comparison between simulation and experimental tests for both cases (specimen with and without air layer) allowed the validation of the previously developed PEA cell simulation mode…