The Pulsed Electro Acoustic Method (PEA) is a widely used method for the measurement of space charges in High Voltage (HV) dielectrics. This thesis aims to contribute to the optimization of the PEA method by being able to make measurements from different test setups comparable and enhance the reliability of the results interpretation. This work is divided in two main parts with different scopes. In the first part, the work is focused utilizing flat samples, in which the effects of the different electrode materials at the dielectric interface and the use of reference samples for measurement characterization is analyzed. In the second part of this work, the focus is on measurements at HVDC cables for which the effects of different pulsed voltage injection configurations are tested, with a special focus in reduction of the crosstalk between the applied pulse and the acoustic sensor. The obtained results contribute to optimize the application of the PEA method for measurements of the space charge phenomena in HVDC components.@en

The Pulsed Electroacoustic Method is one of the most common methods for space charge measurements in solid dielectrics. This method involves applying a voltage pulse across the dielectric under test, which modifies the electrostatic force balance across the dielectric, creating an acoustic signal that can be measured externally. This work analyzes the influence of the pulsed voltage circuit connection location at the PEA test towards the generated distortion due to the electromagnetic interaction between the pulsed voltage and the acoustic sensor by means of experimental tests. From the tests, it can be observed that the connection locations of the pulsed voltage circuit directly connected to the test cell have a significant influence on the distortion magnitude. In practice, this means that the generated distortion can be significantly diminished by modifying the physical location of the connection to the PEA test cell of the pulsed voltage injection electrodes. The results of this paper could serve as a guideline for the construction of PEA measurement setups to minimize the signal distortion caused by the pulsed voltage, which can also reflect in simpler post-processing.@en

Space charges are one of the main challenges facing the constantly increasing use of extruded high voltage direct current (HVDC) cables. The Pulsed Electro-Acoustic (PEA) method is one of the most common procedures for space charge measurements of insulation. One issue with the PEA method is distortion due to the crosstalk between the applied voltage pulse and the acoustic sensor. This work analyzed two factors involved in the reduction in this distortion: the influence of the exposed semiconductor distance between the injection electrodes and PEA test cell, and the influence of adding a reactance at the grounding circuit of the PEA test cell. The interaction of these two factors with the distortion was analyzed through a series of experimental testing. Moreover, the performance regarding distortion after applying a developed coaxial injection was compared with the standard non-coaxial injection configuration. It was observed that these two factors had a direct impact on distortion and can be utilized for the reduction in distortion arising from the crosstalk of the applied pulsed voltage. The results can be utilized for the consideration of practical aspects during the construction of a PEA test setup for the measurement of full-size HVDC cables.

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Nowadays, with the widespread use of High Voltage Direct Current (HVDC) cables in power systems, the measurements of space charges in full-size cables are becoming more relevant. One of the most common methods used for space charge measurements is the Pulsed Electro-Acoustic (PEA) method. This paper analyzes two factors that influence the electromagnetic interference on the piezoelectric signal. These factors are the connection of the injected pulsed voltage at the PEA test cell and the grounding of the PEA test cell. The influence was analyzed by means of experimental tests to compare different configurations and the electromagnetic distortion created in each one of them. It was observed that the physical location of the pulsed voltage at the electrode has a very important impact on the magnitude of the electromagnetic distortion. Moreover, it is shown that the physical connection of the grounding and the existence of a parasitic capacitance at the PEA test cell are also an important source of distortion.@en

Nowadays, the most common procedures to measure space charges in dielectrics are based on acoustic and thermal methods. For the acoustic methods, one of the biggest challenges in thick dielectrics is the inherent mechanical losses of the material. Several post-processing methods exist to compensate the acoustic losses at the propagating waves. These methods rely on comparing the measured signals coming from the electrodes, which due to the acoustic divergence at the dielectric-electrode interface, may rise to errors. In this paper a comparison of the effects of the electrode configurations is performed and validated using a reference sample. Afterwards, a method for the attenuation compensation avoiding the dielectric-electrode interface by a reference sample is presented.@en

Nowadays, the use of several methods for the measurement of space charges in dielectrics has become more relevant. The availability of different space charge measurement methods brings the necessity of calibration and characterization of measurement equipment to reach standardized measurements. In this paper, a method is presented to apply known charges at built samples which can be used for acoustic and thermal methods to compare measured values with calibration purposes. Experimental tests for validation purposes were performed in flat samples by comparison of results between a single layer and multilayer samples. Moreover, this method can be used to measure the resolution and accuracy of space charge measurement systems.@en