Pulsed Electro-Acoustic Method for specimens and cables employed in HVDC systems: some feasibility considerations

Imburgia, A.; Romano, Pietro; Sanseverino, Eleonora Riva; De, L.; Bononi, S. Franchi; Troia, I.

doi:10.23919/aeit.2018.8577421

Cited by 16 publications

(7 citation statements)

References 14 publications

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“…compatibility of a commercial PEA apparatus should be carefully evaluated on the basis of the characteristics of the specific cable on which space charge measurements should be done. In addition, a physical model of the measurement region of the cable and of the PEA cell should be implemented in order to correctly evaluate the superposition of reflected signals on the direct ones that reach the piezoelectric film [47]. To date, the PEA method is not considered a non-destructive measurement on laying cables since a partial stripping of the outer layers is necessary.…”

Section: Comparison Between the Pea And Thermal Step Methods (Tsm)mentioning

confidence: 99%

Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables

et al. 2019

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This review takes into account articles and standards published in recent years concerning the application of the Pulsed Electro Acoustic (PEA) method for space charge measurement on High Voltage Direct Current (HVDC) cables and mini-cables. Since the 80s, the PEA method has been implemented for space charge measurements on flat specimens in order to investigate space charge phenomena and to evaluate the ageing of dielectrics. In recent years, this technique has been adapted to cylindrical geometry. Several studies and experiments have been carried out on the use of the PEA method for full size cables and HVDC cable models. The experiments have been conducted using different arrangements of the measurement setup and focusing attention on different aspects of space charge phenomena. In this work, the importance of space charge measurement is highlighted and the state-of-the-art PEA method application to full size cables and mini-cables is described. The main aim of this paper is to offer a complete and current review of this technique. In addition, limits on the use of PEA method are examined and main possible directions of research are proposed in order to improve the applicability, reliability, and replicability of this method.

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Section: Comparison Between the Pea And Thermal Step Methods (Tsm)mentioning

confidence: 99%

Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables

et al. 2019

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“…However, each PEA cell allows us to correctly measure the accumulated charge (without reflected signal) in specimens of dielectric material with features in a specific range of values. To facilitate the choice of sample features based on the used PEA cell, some useful graphs have been reported in a previously published work [18,19].…”

Section: Acoustic Wave Behavior Within the Pea Cellmentioning

confidence: 99%

“…In the previously published works, authors have shown that each PEA cell (on the basis of its ground electrode and absorber thicknesses) is suitable to measure space charge on dielectrics with sound velocity and thickness in a fixed range of values [18,19]. If the sample's features fall outside the range allowed by the adopted PEA cell, a certain amount of reflected signals are present within the main space charge profile.…”

Section: Introductionmentioning

confidence: 99%

Reliability of PEA Measurement in Presence of an Air Void Defect

et al. 2020

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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 model. The latter was previously validated only for a single layer specimen, here the good performances of the model have also been confirmed in the case of a multilayer specimen, also with an air layer. Experimental and simulation results show that the air layer acts as a barrier for the acoustic signal, due to the different acoustic impedance between the air and the solid dielectric material which constitute the specimen. Therefore, the aim of the present work is to demonstrate that in the case of a three-layers specimen, composed as dielectric-air-dielectric, the PEA cell is not able to provide the complete profile of the entire specimen under test.

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“…The 20 m long cable under test, equipped with a 20 mm thick XLPE dielectric layer, has been subjected to a voltage of 380 kV. After applying the pulse voltage with magnitude 8 kV, the PEA cell output signal displayed by the oscilloscope is shown in Figure 4 [33]. As it can be seen, the obtained space charge profile is not very clear.…”

Section: Experimental Test On a Cable Specimenmentioning

confidence: 99%

The Industrial Applicability of PEA Space Charge Measurements, for Performance Optimization of HVDC Power Cables

et al. 2019

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Cable manufacturing industries are constantly trying to improve the electrical performance of power cables. During the years, it was found that one of the most relevant degradation factors influencing the cable lifetime is the presence of space charge in the insulation layer. To detect the accumulated charge, the pulsed electro-acoustic (PEA) method is the most used technique. Despite the wide use of the PEA cell, several issues are still present. In particular, the PEA output signal is strongly disturbed by the acoustic waves reflections within the PEA cell. This causes the distortion of the output signal and therefore the misinterpretation of the charge profiles. This, in turn, may result in an incorrect cable characterization from the space charge phenomenon point of view. In 2017, due to the proved degradation effect of the space charge accumulation phenomenon, the IEEE Std 1732 was developed. This standard describes the steps to be followed for the space charge measurement in cables specimens during pre-qualification or type tests. Therefore, cable manufacturing industries started to take a particular interest in these measures. In the light of this, the aim of the present work is to highlight that the enacted standard is not easily applicable since various problems are still present in the PEA method for cables. In particular, in this work, the effect of multiple reflected signals due to the different interfaces involved, but also the effect of the signal attenuation due to cable dielectric thickness, as well as the effect of the PEA cell ground electrode thickness in the output charge profile, are reported. These issues have been demonstrated by means of an experimental test carried out on a full-size cable in the Prysmian Group High Voltage laboratory. To better understand the PEA cell output signal formation, a PEA cell model was developed in a previous work and it has been experimentally validated here. In particular, simulations have been useful to highlight the effect of the reflection phenomena due to the PEA cell ground electrode thickness on the basis of the specimen under test features. Moreover, by analyzing the simulation results, it was possible to separate the main signal from the reflected waves and, in turn, to calculate the suitable ground electrode thickness for the cable specimen under test.

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Pulsed Electro-Acoustic Method for specimens and cables employed in HVDC systems: some feasibility considerations

Cited by 16 publications

References 14 publications

Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables

Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables

Reliability of PEA Measurement in Presence of an Air Void Defect

The Industrial Applicability of PEA Space Charge Measurements, for Performance Optimization of HVDC Power Cables

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