0000000000462768
AUTHOR
S. Franchi Bononi
Effect of Polarity Reversal on the Partial Discharge Phenomena
In the field of High Voltage Direct Current (HVDC) transmission, the space charge accumulation phenomenon and the Partial Discharges (PD) phenomena are considered the main causes of dielectric ageing. During the years, the degradation effect of both phenomena under constant DC stress has been widely studied by several researchers. In case of polarity reversal, typically carried out to control bi-directional power flow between interconnected High Voltage transmission systems, the space charge movement may not synchronously follow the electric field polarity. This could make the moment of reversing polarity a very critical one, where space charge injected during preceding polarity produces hi…
Different Measurement Setup Configurations for Space Charge test in Mini Cable Specimens with the PEA Method
Under DC stress, the space charge accumulation is believed one of the most responsible of dielectrics ageing. For this reason, due to the increase of the HVDC transmission, a recommendation has been proposed. The latter want to introduce the space charge measure, with the PEA method, in cable specimens during the prequalification or type tests. Considering the several issues related to this kind of measures the aim of the proposed work is find a measurement setup for mini cable specimens which is able to provide a clear and clean space charge profile. Therefore, different tests have been made in this work. In particular, the length of the cable specimen, the width of the pulse electrodes, a…
Interpretation of PEA Output Signal in a Multilayer Specimen
The aim of the present work is to evaluate the acoustic waves behavior within the Pulsed Electro-Acoustic (PEA) cell, in case of a multilayer specimen, in order to avoid misinterpretation of the output signal. Due to the reflection phenomenon of the acoustic waves travelling within the PEA cell, the output signal could be distorted. Because this aspect, for a given PEA cell with certain ground electrode and absorber thicknesses, depends on the sound velocity and thickness of the specimen under test, the latter must be carefully sized. For this aim, some useful relationships, that must be taken into account are given and described. In particular, a three layers sample simulating an air void …