Conference Agenda

The present work introduces a versatile and cost-effective laboratory system and method for the controlled generation and characterization of partial discharges and electrical arcs in insulation systems composed of solid, liquid, and gaseous materials. The proposed setup, for which a patent application has been filed in Brazil, provides a simple and safe way to generate discharge phenomena and study the dielectric and chemical response of different insulating materials under controlled conditions. It consists of a sealed stainless-steel test cell connected to a variable high-voltage source (up to 50 kV), a protective resistance and attenuation circuit, and a high-frequency current transformer (100 kHz–20 MHz) for discharge detection. During experiments, the system enables a gradual increase of voltage from inception to arc conditions, while continuously recording electrical parameters and observing the evolution of discharge activity. The proposed approach bridges fundamental research and practical diagnostics, contributing to safer, more efficient, and more sustainable high-voltage insulation. This work is being developed as part of the project number PD-10737-124/2023 regulated by the National Electricity Agency (ANEEL).

Synthetic air is becoming increasingly important as a substitute for high global warming potential gases, especially sulfur hexafluoride (SF6), in gas-insulated switchgears (GIS) and instrument transformers. With zero global warming potential (GWP), it is among the most sustainable insulating gases, unfortunately with different material behavior and properties compared to well examined SF6. Therefore, new design criteria based on experimental examinations with synthetic air have to be developed.

In this context, this paper contains the design of a compact high-pressure test vessel that enables experimental investigations under AC and LI stress in synthetic air as well as other alternative gases. First, the requirements of the test vessel are presented and a design is proposed which is mainly based on numerous finite element method (FEM) simulations. Regarding choice of components, standard components from GIS and transformer technology are used, to provide a practical, reproducible test environment. This also ensures the possibility of upgrading to higher voltage levels and a general adaptability of the test vessel. A built-in gap adjustment should allow changing electrode distances within the test environment without pressure loss or change. This can significantly reduce gas consumption and set-up times, depending on the test requirements. The test vessel is designed to operate up to gas pressures of 1.5 MPa (abs.). The electric qualification is done with respect to AC withstand voltage, LI withstand voltage and partial discharge inception and extinction at AC-voltages leading to sufficient operating range for examinations on synthetic air. Furthermore, determined values of AC and LI breakdown voltages correspond exactly with IEC 60052 proving low influence and interactions of the test vessel environment on the investigated insulating gas. As the evaluation of discharge processes closed to solid-gas-interfaces is considered as significant, an arrangement for the examination of the interface behavior is presented. This arrangement is integrated in the test vessel and mainly consists out of a plate-plate electrode configuration with adjustable solid insulation spacer.

Concluding: At optimized costs and minimum room requirements, this paper presents a compact and mobile high-pressure test vessel with an additional opportunity to upgrade to higher voltage levels and enabling various relevant examinations on synthetic air, e. g. pressure depending examinations regarding electrode geometry, electrode material, surface roughness of electrodes as well solid insulating materials and solid-gas interfaces.

Magnet wires serve as the critical component in electric motors, whose insulation integrity fundamentally governs the operational lifetime and reliability of the machine. Nevertheless, surface scratches—inevitably introduced during manufacturing—constitute latent weak points within the insulation system and represent a major initiator of premature insulation failure. To quantitatively assess the impact of such scratches and achieve their early-stage detection, this work systematically examines the evolution of the partial discharge inception voltage (PDIV) in twisted-pair magnet wires under combined thermal (150 °C) and low-pressure (5.4 kPa) stresses, with particular emphasis on scratch location. Experimental results indicate that under ambient conditions, minor scratches lead to a significant increase in PDIV data dispersion. At elevated temperatures, the degradation of insulation homogeneity distorts surface charge distribution, which unexpectedly suppresses PDIV reduction in all but the most severely damaged specimens. In contrast, under low-pressure environments, all scratched samples exhibit marked insulation deterioration. Building on these observations, a diagnostic methodology is proposed to classify scratch types based on their distinctive PDIV responses under different environmental stressors. Further stepwise electrothermal aging tests validate pronounced differences in the degradation pathways among specimens with varying initial scratch configurations. These insights establish a theoretical and experimental framework for shifting insulation condition assessment from reactive fault correction to proactive damage alert, offering crucial guidance for improving the manufacturing quality and operational resilience of high-performance electric motors

The time-frequency (TF) map technique has been utilized over the past decade to classify AC partial discharges in two dimensions. Recently, a more advanced method combining magnitude, time, and frequency (MTF) in three dimensions has been introduced to differentiate between DC arcs, corona, and partial discharge sources in real-time. This paper presents a new approach for classifying signals using MTFA, which improves upon the earlier MTF method. Arcs, partial discharges, and external noise occur in both AC and DC power systems. In AC systems, phase-resolved partial discharge (PRPD) patterns monitor discharge activity and distinguish external noise in two dimensions. During post-processing of the PRPD pattern, frequency features are analyzed using TF or wavelet techniques. The MTFA method, synchronized with the power frequency, provides real-time solutions for classifying partial discharge sources, arcs, and external noise across four dimensions: magnitude, time, frequency, and phase angle. In DC systems, signals can be analyzed in three dimensions—magnitude, time, and frequency (MTF)—or in magnitude pulse sequence (MPS) mode. Additionally, four dimensions, including phase angle information, can be examined in MTFA mode. An experiment using the MTFA approach was conducted on a rotating machine and batteries from a battery energy storage system (BESS). The results show that the MTFA technique offers significantly clearer and more detailed visualization of signals in AC and DC power systems in real time. Its advantage is its ability to classify signals without needing extra processing or expert intervention. It extracts separate PRPD patterns from mixed partial discharge sources, such as surface and internal discharges, as well as external noise, which occur simultaneously in a rotating machine. In a DC system, signals are captured in sync with the power frequency, including PCS noise or signals like corona and surface discharge, which are synchronized with specific phase angles of the power frequency. The detailed specifications of the MTFA tools will be described in the algorithm and hardware setup.

In typical laboratory settings, traditional (IEC 60270) methods for the generation of partial discharge (PD) types have been used over the years. In this paper, a synthetic technique for the generation of these PD types was developed. To achieve this, information on traditional PD generation were first collected providing adequate data for quantitatively characterizing PD types in time and phase domains. Consequently, for the PD modelling, the time domain PD representation was adopted due to its usefulness in presenting a direct representation of a signal, which provided valuable information required to understand the transient characteristics of a signal, such as amplitude variations, frequency content, and pulse shape. The time domain characteristics of the PD types were used to develop the pulse shapes of the 3 types of PD waveforms providing relevant parametric information to be used for modeling, simulation, and generation. With these parameters serving as inputs, the PD types were modeled using a system of algorithms from single and double exponential decay and oscillatory functions which better portrayed the waveforms. The generated PD data from MATLAB was collected, stored and transferred unto an integrated hardware system made up of a Siglent SDG 1062X arbitrary waveform generator, an NI 7841 Multifunction Reconfigurable IO FPGA, and an Agilent DSO6032A oscilloscope, for the synthetic generation of corona, surface, and internal PD pulses. A system for triggering PD pulse types at a specific phase along a power line AC cycle is realized with the help LabVIEW. To validate the system design, results of the integrated PD generation system was compared with PD signal from a commercial PD calibrator and real PD data. In conclusion, the developed system demonstrated a high accuracy in generating PD like signals indicating, possible use of the system for PD generation applications in the absence of the traditional setup.

Fluid filled High Voltage AC (HVAC) cable systems such as self-contained fluid filled (SCFF), Low-Pressure Fluid Filled (LPFF) and High Pressure (HPFF) cable systems, have been in operation since before the 1950’ties in North America and globally. Common practice for site field tests such as commissioning tests, after-repair test or maintenance tests has been, and largely continues to be, to employ HVDC withstand tests. In North America, the guiding standards are IEEE 400.1 and as per CS9. However, for AC Cable systems, DC stresses do not provide for test conditions similar to those experienced under operation and, furthermore, under DC stresses, commonly used diagnostics such as Partial Discharge (PD) measurements or Tan Delta measurements, which allow for identification of life limiting defects in the cable system and/or over all aging, cannot be performed. In particular for asset condition assessment of aged cable systems, diagnostics are in-particular important. While for MV Paper Insulated Lead Covered (PILC) cables AC testing has been commonly employed, for HVAC fluid filled systems, HVDC testing has mainly been used. Anecdotally, the main reason for not employing HVAC testing has been lack of equipment able to energize longer length of fluid filled cable systems. As well, most fluid filled cable systems being encased in steel pipes challenges exist with partial discharge measurements. However, HVAC Resonant Test Systems commonly used for testing of solid dielectric cable systems can be employed for fluid filled cable systems. This paper suggests a framework for commissioning as well as asset condition assessment testing of fluid filled cable systems at near-power frequency (20-300Hz) including voltage levels and durations as well as the use of partial discharge measurements and Tan Delta Measurements and the technical challenges involved. The paper also provides case studies of both commissioning and asset condition assessment tests of cable systems aged 40 year and older. Finally, the paper discusses further work to be performed in the field of site diagnostics of fluid filled cable systems using AC stresses.