Partial Discharges are a major cause of electrical stress and insulation failure, but their presence is also a symptom of insulation problems. Online Partial Discharges measurement allows for continuous monitoring of the insulation system. An online Partial Discharges measurement system for air insulated switchgear has been developed, based on Transient Earth Voltage (TEV) sensors, and evaluated for morphological analysis of insulation defects. The evaluation has been conducted comparing the developed system with a conventional PD measurement system based on the IEC 60270 standard. The aim of the proposed system is to facilitate its integration with minimal retrofitting and operational disruption assuring the possibility to identify and analyze the defects. A pilot system, employing an air insulated switchgear, was designed and tested. The results from both the Partial Discharges measurement systems are presented and discussed. Furthermore, the impact of a high capacitive load connected to the switchgear is investigated and the possible effects of a capacitive load due to a MV cable is considered by simulating the realistic cable geometry.

Electrical insulation is a critical component in electrical machines. The performance of the insulation system can be adversely affected by operating conditions that induce aging. Assessing the impact of environmental stresses is essential for predicting the failure of electrical insulation. Predicting maintenance to prevent service interruptions caused by insulation breakdown is a key objective. For type I insulating systems used in low-voltage and low-power rotating electrical machines, it has been demonstrated that partial discharges (PDs) are a contributing factor to electrical insulation breakdown. In fact, these insulating systems are not able to withstand the action of PD activity. The inception and evolution of PD activity is an indication of the poor conditions of the electrical insulating system, and this activity can be produced by the electronic power supply. The progressive reduction in partial discharge inception voltage (PDIV) is attributed to the deterioration of insulation properties induced by operational stresses. This study aims to evaluate and compare the effects of thermal stress on various types of enameled wires by collecting the PDIV values over time. In this paper, the authors analyze some particular effects of thermal stress as an aging factor. During the tests, an electrical stress was applied, which acted as a conditioning stress rather than one capable of producing degradation phenomena, as it was not high enough to initiate PD activity. In this research study, twisted pairs prepared from copper wires were evaluated. These wires were coated with various types of enamel and belonged to the thermal class of 200 °C. The samples were subjected to thermal aging tests at different temperatures. An electrical conditioning stress was also applied during all the tests and pertained to the same voltage, amplitude and frequency. The PDIV value pertaining to each sample was regularly measured to monitor its evolution over time.

This study presents a characterization method for High-Frequency Current Transformers (HFCTs) intended for partial discharge (PD) measurement in on-line acquisition systems designed for AI-based processing and clustering. The primary objective is to analyze how key design parameters, ferrite core material, and number of turns, influence HFCT frequency response, attenuation, and sensitivity, thereby providing a basis for optimized sensor design when data analysis is to be performed by means of AI-based algorithms. The investigation focuses on the influence of different ferrite core materials and varying secondary turn numbers on the frequency spectrum and the response to IEC 60270-compliant calibrator impulses Both concentrated and well-distributed HFCT secondary winding configurations are analyzed to evaluate their impact on signal behavior and sensitivity. The experimental results are compared with a simplified theoretical model to validate performance trends and identify key design factors. The HFCT response to IEC 60270-compliant calibrator impulses is examined to assess its suitability for PD measurement systems and monitoring. The results highlight the critical role of core selection and the number of turns in shaping HFCT bandwidth, attenuation, and impulse response, which are essential for accurate and reliable PD detection in continuous monitoring systems to perform the diagnostic of the electrical insulation condition. This diagnostic approach is based on the detection of partial discharge (PD) activity over time, with the objective of identifying evolving phenomena by monitoring the amplitude and characteristics of the signals associated with different defects. Therefore, accurate separation of signals originating from different defects and from noise is essential. These results provide a foundation for designing HFCT sensors suitable for integration into advanced diagnostic frameworks, AI-aided for Condition-Based Maintenance (CBM).

The insulating systems are one of the most important parts for the proper operation of the electrical devices and can be subject to deterioration due to several phenomena like partial discharges. Nowadays, due to the increasing presence of the power electronic devices, there is an interest in studies relevant to the partial discharge activity not only in the presence of pure sinusoidal voltage waveforms, but also when a DC component is added as result of electronic AC/DC conversions or floating potential operations. This work is focused on aging tests on twisted pairs specimens applying pure AC or AC+DC waveforms. The test voltage waveforms are applied to twisted pairs specimens until the total breakdown, assumed as end life criterion, is reached defining the life curves both in AC and AC+DC cases. During the aging, partial discharges are acquired, and it is possible to compute derived quantities useful to define a predictive model of the residual specimen lifetime. For what it concerns the presence of an overlapped DC component, the obtained results suggest that, considering the conditions imposed in this study, no remarkable changes in the aging phenomena and in the measured PD activity are identified.