Interpretation of PEA Output Signal in a Multilayer Specimen

Andrade, M. De Araujo; Candela, R.; De, L.; Bononi, S. Franchi; Imburgia, A.; Sanseverino, Eleonora Riva; Romano, Pietro

doi:10.1109/ceidp.2018.8544911

Cited by 8 publications

(3 citation statements)

References 8 publications

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“…The reflections are occurring on the interlayer interface. It is caused by acoustic impedance z transition, defined as z = ρ • υ, where ρ represents material density [24]. In that context, it is important to separate and extract signals representing the space charge without superimposed reflection components.…”

Section: Signal Processing In the Pea Methodsmentioning

confidence: 99%

Bulletin of the Polish Academy of Sciences: Technical Sciences

Florkowski

Kuniewski

2022

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High voltage DC insulation plays an important role, especially in power transmission systems (HVDC) but also increasingly on medium voltage levels (MVDC). The space charge behavior under DC voltage has great importance on electrical insulation reliability. This paper reports investigations of encapsulated space charge in homo-multilayer dielectric materials using the pulsed electro-acoustic (PEA) method. The charge has been introduced on the homo-layer interface by corona sprinkling prior to encapsulation. Two doses of charge density were accumulated on the dielectric surface in two types of dielectric materials Kapton and LDPE. The polarization DC voltage was applied in 2 min intervals in steps corresponding to an effective electric field strength in a range of 8-40 kV/mm for Kapton and 10-50 kV/mm for LDPE. The PEA-based detected space charge was compared at the initial, reference stage, prior to charge accumulation, and after corona sprinkling of defined charge density. The evaluation was based on the PEA time-dependent charge distributions and charge profiles referring to the DC polarization field strength. The goal of the experiment was to identify the relationship and the character of the known sprinkled and encapsulated charge inside homo-layered materials using the PEA method. According to the observations, the ratio between sprinkled charge densities is proportional to the encapsulated, charge densities measured by the PEA method on the interfacial homo-layer for the Kapton specimen. In the case of LDPE, a fast decrease of interfacial charge was observed, especially at a higher polarization field above 10 kV/mm. The encapsulation of the known charge amount can be extended to different types of multilayer material. The presented methodology might be used also for extended calibration of the PEA measurement system.

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Section: Signal Processing In the Pea Methodsmentioning

confidence: 99%

Bulletin of the Polish Academy of Sciences: Technical Sciences

Florkowski

Kuniewski

2022

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“…Based on the reflection phenomenon mentioned above, the authors proposed several works, as well as a MATLAB model simulating the acoustic wave behavior within the PEA cell [13][14][15][16][17][18].…”

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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“…Typically, in the PEA cell output signal only two main peaks due to positive and negative surface charges accumulated in the dielectric interfaces should be present. However, if the reflected waves fall between the two main peaks a signal distortion occurs [26]. For this reason, it is important to evaluate before or after a space charge measurement the acoustic wave behavior with the aim to establish the temporal location of both main peaks as well as their reflections.…”

Section: Introductionmentioning

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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Interpretation of PEA Output Signal in a Multilayer Specimen

Cited by 8 publications

References 8 publications

Bulletin of the Polish Academy of Sciences: Technical Sciences

Bulletin of the Polish Academy of Sciences: Technical Sciences

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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