Partial Discharge Process Research Articles

Experimental investigation and evaluation of drying methods for solid insulation in transformers: A comparative analysis

Drying of transformer winding insulation has a direct impact on the dependability and durability of the transformer. The extraction of moisture from paper insulation is a crucial need in the manufacturing process of transformers. Insulation efficiency in transformers can be reduced over time due to the detrimental effects of temperature, moisture, and air, often known as aging. Heat, oxygen, and residual moisture increase the deterioration of cellulose in transformer solid insulation. This might potentially result in premature failure of the transformer. The factory's insulation drying process should ensure that the residual moisture content of bulk solid insulation remains below 0.5 %. The primary aim is to maintain a high degree of polymerization, often ranging from 1000 to 800. This article investigates the factors contributing to the degradation of cellulose insulation and analyzes various techniques that are used in manufacturing plants in Kazakhstan. In addition, this study experimentally investigates the impact of vacuum on the process of moisture evaporation and partial discharge (PD) in analysis with other methods of drying transformers.

Experimental assessment of high-energy high nickel-content NMC lithium-ion battery cycle life at cold temperatures

An essential element for the diffusion and environmental impact assessment of electrochemical storage systems is their lifetime. This lifetime also impacts the overall cost of the equipment in which the storage system is used. At the same time, a number of applications, e.g. electric vehicles, do not allow a temperature control of the batteries, although the performances of the latter are very strongly linked to them. The phenomena investigated, such as aging, behavior at low temperature and rapid charge for low temperature, are complex and difficult to model. Only the establishment of databases representative of the conditions of use can lead to elements of response. The exploitation of these databases by artificial intelligence tools is certainly relevant but requires a learning on data representative of the conditions of use and of the phenomena to be evaluated.The work presented in this paper is in this context and is intended to model the influence of the rapid charge at low temperature (0 °C, −10 °C, −20 °C) on the lifetime (initial capacity loss) of lithium-Ion NMC elements. The problem with data-based approaches is the large number of tests required and the development in relevant experimental designs. Faced to this challenge, a consortium of French laboratories and manufacturers has been working together since the 2000s to carry out this type of work. The paper proposes to present a test campaign and summarizes the main results to assess the service life (loss of capacity) for a fast-charging application at low temperature and position them against the manufacturer data established at 25 °C. The impact of two partial discharge processes (50 %) will also be assessed. In a last part, we show that for low temperatures, even for the nominal charge current the life time is reduced to few dozens of cycles and a mechanical destruction of the cell with no activation of the current interrupt device is achieved. This study demonstrates and quantifies the very important impact of low-temperature charging processes on the lifetime of high energy lithium-ion NMC batteries.

Influence of frequency on the partial discharge characteristics of biaxially oriented polypropylene film under nanosecond pulse voltage

Partial discharge (PD) is one of the key factors leading to premature insulation failure of film capacitors used in pulse power devices. To study the effect of frequency on the PD characteristics of biaxially oriented polypropylene (BOPP) film, a sphere-plate electrode was used to simulate defects of the air gap between the film layers. PD experiments of the BOPP film were carried out under 1, 10, 100, 500 Hz, and 1 kHz with a rising edge of 65 ns and a pulse width of 300 ns. The results show that the repetitive partial discharge inception voltage (RPDIV), the number of discharges, the rising stage discharge (RSD) amplitude, and the falling stage discharge (FSD) time-lag, all show an increase and then decrease with increasing pulse frequencies and reach a maximum value at a pulse frequency of 100 Hz. Moreover, the FSD discharge amplitude and the RSD discharge time-lag increase with an increasing pulse frequency. From the perspective of initial electron generation, the quantitative mathematical relationship between PD characteristics (RPDIV, PD amplitude, PD number, and PD time-lag) and frequency was established based on the Fowler–Nordheim field emission effect for the first time, which can reflect the influence of frequency on the memory effect and the development process of PD. The results can provide an experimental basis and a mechanistic explanation for the evaluation of PD characteristics for film capacitors under nanosecond pulse voltage.

Influence of Water Ingress on Surface Discharges Occurring on the Silicone Gel Encapsulated Printed Circuit Boards Developed for Deep-Sea Applications

This paper discusses the influence of water ingress on the electrical discharges that arise on the surface of printed circuit boards that are developed for deep sea applications. The primary concern is the electrical discharges arising on the surface of the PCB bridging localized spots/areas between conductive traces, high voltage terminal, mounting hole options, and so on. The current literature focuses on electrical discharges arising on the surface of PCB at low-pressure environments emulating aircraft and space applications. Extending the same approach to deep-sea environments is not feasible since the pressure is very high and the temperatures are very low. In all, a meager attempt has been made to investigate the possible application of such gel-encapsulated PCBs in adverse high-pressure, salt/sea water, low-temperature, deep-sea environments. This experimental study focuses on studying the influence of deionized and sea water on electrical discharges arising on the surface, between conductive tracks of PCB. A group of PCBs with different gaps between the conductive tracks was produced and immersed in deionized and seawater for a specific duration at standard pressure. Afterward, the discharge characteristics were measured the using partial discharge (PD) test method and the respective phase-resolved PD pattern was studied and analyzed. Pertinent experiments revealed that the PD process and eventual failure manifests as a typical and substantial pattern. The apparent charge measured during the PD inception and near-by failure condition, influenced by deionized and seawater, reveals a regular trend. Naturally, a simple observation of the PD pattern might help to identify the intricacy and to initiate a preventive measure well before the complete system suffers a premature failure. Also, based on these results, making slight structural modifications on the PCB at crucial locations might help in retaining the dielectric integrity of the material.

Spatial Spectral Characteristics of Partial Discharge with Different Electrode Models

In this paper, the spatial spectral characteristics of partial discharge (PD) under different electrode models are mainly studied. In the initial corona discharge stage, the emission spectrum is mainly emitted by the N2(C3IIu→B3IIg) energy level transition of the N2 second positive band system. The spectrum is in the ultraviolet range of 294–436 nm, and its main peak is at 337 nm. The streamer discharge stage spectrum is mainly emitted by the energy level transition of the second positive band system of N2, N+, NO, and O+ and the first positive band system of N2(B3IIg→A3Σu+). In the gap of different polarity electrodes, the ultraviolet spectrum content near the positive polarity is more abundant. The UV spectra ranges are 202–225 nm and 229–292 nm, respectively. The discharge of the needle–sphere system is more intense in visible light and near-infrared light, with peaks at 500 nm and 777 nm, respectively. In addition, the PD process based on the finite element method is simulated by COMSOL Multiphysics software. The simulation results show that the distribution of high-energy electron density varies with the electrode spacing and discharge model. The influence of particle energy level transition on the spatial spectral characteristics of PD is verified. This work provides important insights and possibilities for future fluorescent fiberoptic sensing and positioning for spatial PD detection and positioning using spectral characteristic peaks as detection quantities or excitations.

Study on the Partial Surface Discharge Process of Oil-Paper Insulated Transformer Bushing with Defective Condenser Layer

Oil-impregnated paper condenser transformer bushings are an important part of transformer equipment, and partial discharge (PD) occurred when defects exist on the condenser aluminum foil layers. Firstly, to study the PD process of the oil-paper insulated capacitance graded bushing with the defect of broken aluminum foil, a defective oil-paper bushing discharge sample is constructed to study the PD parameters and capacitance, and to discharge carbonization traces at different voltage levels. Then, in order to verify the process of condenser aluminum foil layer discharge and the space charge variation in the oil-paper insulation system of a sample model, the surface flashovers of a needle-plane discharge model based on the bipolar charge transport model and the hydrodynamic model was built. The simulation, by Transport of Diluted Species physics of COMSOL Multiphysics software, points out the discharge process of aluminum foil electrode caused by space charge action and electric field distortion under an electric field at different voltages. The results of simulation and sample bushing experiments showed that the PD process of the defective condenser foil layer is mainly divided into three stages: tip corona discharge, streamer in oil, and surface flashovers. The voltage amplitude is larger the more electrical branches are discharged and the shorter the discharge time is. The findings of the article have important implications for the discharge of the foil layer inside the oil-paper bushing.

Numerical Simulation Research on Partial Discharge of Particle Defects at Epoxy Interface Excited by High-Frequency Sinusoidal Voltage.

In order to improve the effectiveness of partial discharge detection in attached metal particle insulators, this paper proposes a partial discharge detection method for particle defects in insulators under high-frequency sinusoidal voltage excitation. In order to study the development process of partial discharge under high-frequency electrical stress, a two-dimensional plasma simulation model of partial discharge with particle defects at the epoxy interface is established under plate-plate electrode structure, which realizes the dynamic simulation of particulate defect partial discharge. By studying the microscopic mechanism of partial discharge, the spatial and temporal distribution characteristics of microscopic parameters such as electron density, electron temperature, and surface charge density are obtained. Based on this simulation model, this paper further studies the partial discharge characteristics of epoxy interface particle defects at different frequencies, and verifies the accuracy of the model from two aspects of discharge intensity and surface damages through experimental means. The results show that with the increase in the frequency of applied voltage, the amplitude of electron temperature shows an increasing trend. However, the surface charge density gradually decreases with the increase in frequency. These two factors make partial discharge severest when the frequency of the applied voltage is 15 kHz.

A Reactive Molecular Dynamics Study on Crosslinked Epoxy Resin Decomposition under High Electric Field and Thermal Aging Conditions.

To reveal the microscopic mechanism of synergetic thermal-electrical degradation during a partial discharge process in epoxy insulation materials, the decomposition of crosslinked epoxy resin is investigated using reactive molecular dynamics simulations under high electric field and thermal degradation conditions. Bond-boost acceleration method is employed in reactive molecular dynamics simulations to successfully establish epoxy polymer models with a crosslink degree of 93%. Active molecular species derived from electrical partial discharges are considered in the current work. Small molecule products and decomposition temperature in the degradation process under an electric field are calculated to elucidate the effect of nitric acid and ozone molecules, being the active products generated by electrical partial discharges, on the synergetic thermal-electrical degradation of epoxy resin. Both nitric acid and ozone exacerbate thermal impact decomposition of crosslinked epoxy polymer by decreasing initial decomposition temperature from 1050 K to 940 K and 820 K, respectively. It is found that these active products can oxidize hydroxyl groups and carbon-nitrogen bridge bonds in epoxy molecular chains, leading to the aggravation of epoxy resin decomposition, as manifested by the significant increase in the decomposed molecular products. In contrast, thermal degradation of the epoxy resin without the active species is not expedited by increasing electric field. These strongly oxidative molecules are easily reduced to negative ions and able to obtain kinetic energies from electric field, which result in chemical corrosion and local temperature increase to accelerate decomposition of epoxy insulation materials.

Applicability of the acoustic–electrical joint detection method to identify defects in gas insulated system

AbstractThere are many defects in gas‐insulated metal‐enclosed switchgear (GIS) and gas‐insulated transmission lines (GIL) that may cause accidents, such as floating potentials, metal particles, air gaps, and cracks in support insulators. Nevertheless, to‐this‐date, there is no effective method to recognize them to adjust their operation status. Accordingly, this study compared three typical defect models to explore the partial discharge process, and three typical experimental models were established to identify the characteristic parameters of acoustic and electrical information in the development of defects. The research study shows that that as the voltage increases, the partial discharge of free‐metal‐particle defects and air‐gap defects obtained by the pulse‐current method increase gradually. A sudden increase also occurred in the partial discharge of the floating potential defect. The discharge amount of free conductive particles obtained by an ultrahigh‐frequency detection method was distributed symmetrically on both sides of the applied voltage peak, and the other two defects were on one side of the peak and yielded an obvious phase difference. The particle collision signal obtained by the ultrasonic method was obvious, but had no obvious phase relationship with the applied voltage. However, the obtained floating potential defect information had obvious phase differences, and the ultrasonic method was not sensitive to air‐gap defects. The three typical defects can be identified by the combined method more accurately; this provides a theoretical basis and data support for GIS and GIS voltage tests, detection technologies, and online monitoring methods.

Ab-initio study of vacancy-defective aluminium nitride nanosheets as trifluoroacetonitrile gas sensor

Trifluoroacetonitrile (CF3CN) is a decomposition product from the promising dielectric heptafluoro-isobutyronitrile (C4F7N) under partial discharge process, so can be used to detect failures in gas-insulated switchgear. In this work, we study through density functional theory (DFT) calculations the adsorption of CF3CN on pristine aluminium nitride nanosheets (AlNNS) and defective Al-vacancy (vAl) and N-vacancy (vN) AlNNS, in order to explore the potential of these nanomaterials as sensors for this gas. Our energetic analysis shows negligible adsorption energy for the pristine surface but strong interactions can be observed between the molecule and the monovacancy-defected surfaces, with adsorption energy values estimated to be about −2.2 and −3.1 eV for CF3CN/vN-AlNNS and CF3CN/vAl-AlNNS, respectively, which suggests chemisorption processes. Furthermore, our geometric and bonding studies revealed the formation of new N—Al interactions between gas and monovacancy-defected surfaces, with serious distortions for the vAl-AlNNS nanosheet. The electronic density of states and band structure analysis reveals moderate band gap variations after gas adsorption. In contrast, significant changes in the work function and the magnetic moment of defective AlNNS were computed after gas exposition, for all optimized adsorption configurations. Therefore, based on our results, vacancy-defected AlNNS could be suggested as possible material for CF3CN gas sensing.

Efficient Partial Discharge Detection by Plasmonic Photonic Crystal Fiber Sensor With Bimetallic Grating

In this article, a new approach for optical partial discharge (PD) detection in gas-insulted systems is introduced for the first time to the best of our knowledge. The suggested sensor is based on plasmonic D-shaped photonic crystal fiber (PCF). Further, bimetallic grating structure of Ag/Au is utilized to enhance the sensor sensitivity. For light detection, methyl-red-doped poly (methyl methacrylate) polymer (MR-PMMA) is used as a sensing material for its photochromic characteristics and its fast response to visible light radiation. At resonance, good coupling occurs between the surface plasmon mode and the core guided mode. The radiated light intensity reflects the charge magnitude of the occurred PD process which can be detected by calculating the shift in the resonance wavelength of the loss spectra. The structural geometrical parameters are studied to improve the sensing performance using full vectorial finite-element method. The proposed sensor achieves high sensitivity of 667 pm/mW<inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>cm^&#x2212;2 with a linear performance with the light intensity. Moreover, the proposed sensor has advantages of simple and compact design, fabrication feasibility, electromagnetic interference immunity, fast response, and high sensitivity relative to conventional PD detection techniques using electrical methods. The designed sensor can be also utilized for laboratory testing and it could be evolved to accomplish real-time detection of PD phenomenon in gas-insulted systems.

Lifetime and Aging Degradation Prognostics for Lithium-ion Battery Packs Based on a Cell to Pack Method

Aging diagnosis of batteries is essential to ensure that the energy storage systems operate within a safe region. This paper proposes a novel cell to pack health and lifetime prognostics method based on the combination of transferred deep learning and Gaussian process regression. General health indicators are extracted from the partial discharge process. The sequential degradation model of the health indicator is developed based on a deep learning framework and is migrated for the battery pack degradation prediction. The future degraded capacities of both battery pack and each battery cell are probabilistically predicted to provide a comprehensive lifetime prognostic. Besides, only a few separate battery cells in the source domain and early data of battery packs in the target domain are needed for model construction. Experimental results show that the lifetime prediction errors are less than 25 cycles for the battery pack, even with only 50 cycles for model fine-tuning, which can save about 90% time for the aging experiment. Thus, it largely reduces the time and labor for battery pack investigation. The predicted capacity trends of the battery cells connected in the battery pack accurately reflect the actual degradation of each battery cell, which can reveal the weakest cell for maintenance in advance.

Research on numerical simulation for partial discharge of epoxy interface excited by high‐frequency sinusoidal voltage

High-frequency sinusoidal voltage excitation is proposed as a feasible method to solve the difficulty of partial discharge detection at the epoxy interface. In order to study the development process of partial discharge under high-frequency stress, a two-dimensional plasma simulation model of partial discharge for a needle-plate electrode structure is established by coupling particle transport equation, Poisson equation and plasma chemical reaction. The model adopts a reaction set to reduce the difficulty of modelling generation, transport and disappearance of charged particles. It realises dynamic simulation of the partial discharge at the epoxy interface. The spatial–temporal distribution characteristics of microscopic parameters such as electron density, electron temperature and surface charge are obtained. Based on this simulation model, the partial discharge characteristics of the epoxy interface at different frequencies are further studied in this work. The results show that with the increase of applied voltage frequency, the electron temperature shows an increasing trend, but its increasing rate gradually slows down; while surface charge accumulation decreases uniformly with the increase of applied voltage frequency. These two factors make the partial discharge severest under the frequency of 10 kHz. The results of the model are verified from two aspects of discharge form and discharge intensity by experimental means.

Partial discharge type detection and identification based on its sources

Partial discharge (PD) is a symptom of initial damage to high voltage equipment insulators which if left for a long period will cause total damage to high voltage equipment. This study aims to detect and identify the type of PD based on the source of its discharge so that it can be useful in terms of monitoring and maintenance of high voltage equipment. In this research, the Hilbert fractal antenna sensor is used in the detection process of surface, cavity, and corona PD with different input voltage variables that successfully produce a total of 600 PD signal data on the oscilloscope. To reduce noise on the PD signal, the denoising process is done by utilizing the sym4 wavelet feature found in the MATLAB software. The denoising process generates new data so that the research data becomes 600 original PD signal data and 600 denoising PD signal data. With a statistical approach, all PD signal data is extracted successfully into the mean, skewness, kurtosis, and standard deviation parameters which are useful as input for the PD type identification process. From each of the PD signal statistical data, 450 data are used in the training data process and 150 data are used in the data testing process. The PD type identification process is performed using a back propagation neural network with a mean square error (MSE) level of 0.01. The identification results show that back propagation neural networks are able to identify PD types based on statistical input accurately. In addition, the denoising process also affects the accuracy of the identification results of the PD type that is 95.33% for the original discharge signal to 97.33% for the denoising signal.

Experimental Study on Damage Mechanism of Partial Discharge of Oil-Immersed Laminated PMIA Paper

PMIA (Poly-m-phenylene isophthalamide) is an ideal substitute for traditional cellulose paper in oil-immersed paper insulating scenarios. This paper studies the partial discharge characteristics of oil-immersed laminated PMIA. According to the q-φ scatter diagram, discharge quantity and discharge phenomenon, the partial discharge process of PMIA is divided into 3 stages: creeping discharge, co-existence discharge and pre-breakdown. The micro-structure and chemical components of damaged PMIA are presented. The carbon trace, functional groups, carrier trap characteristics and residual insulation strength in different stages of partial discharge are studied. This paper provides a theoretical basis for the application of PMIA in electrical insulation.

Multi-Physical Tracking and Sensing Technology of Switchgear Partial Discharge Based on Edge Computing and Smart Gateway

In view of the high bottleneck of current partial discharge detection technology, strong professionalism and heavy detection tasks, the partial discharge process is greatly affected by the equipment operating environment and condition factors. The paper proposes a switching device partial discharge multiphysics based on edge computing. Research on perception and state tracking technology. The article aims at the edge computing technology of multi-physical partial discharge signal feature extraction, the construction of multi-physical tracking over-limit early warning model, and the development and trial production of intelligent gateway technology. The research found that the edge computing algorithm proposed in the paper can effectively reduce the cost and power consumption under the premise of ensuring the performance of the detection system.

Numerical Modeling of Partial Discharge in a Void Cavity Within High-Voltage Cable Insulation

Partial discharge (PD) in the void cavity inside the insulation of the high-voltage (HV) cable is one of the critical problems. This article describes an approach to investigate the spatial distribution of plasma species related to PD dynamics in an ellipsoid void. The plasma dynamics of this type of discharge has been simulated using a self-consistent 2-D model. The ellipsoid void has the longest diameter of 1.5 mm and the shortest diameter of 0.4 mm and it is located at 6.8 mm from the center of the HV. The results show that there are two current pulses during each cycle of the applied voltage. The current pulses were obtained at the ends of the ellipse. The results of the spatial distribution for the charged species showing that both O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> are a dominated species. The simulation results revealed, in later PD processes, the N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> start to concentrate at the concave surface of the ellipsoid ends of the void.

Review of Partial Discharge Signal Processing and Monitoring System using Virtual Instrument Software

Most of Partial Discharge (PD) processing systems have been developed using virtual instrument to analyse raw measured PD signal. However, some of researchers had neglected the denoising or recognition technique and only focussed on PD location estimation and vice versa This paper reviews an overview of denoising recognition techniques, denoising analysis, PD sensors, location methods and type of virtual instruments in published PD signal processing signal system. A perfect PD analysis system is more beneficial if both PD denoising and locating are applied in the system. Based on this review, the new design of PD signal processing system based on DWT denoising technique and RC sensor using LabVIEW Software for underground power cable using SCTM as PD location algorithm is proposed.

Charge migration of multilayer oil paper on the process of partial discharge under AC voltage

As one of the main reasons for the deterioration of Nomex paper and charge migration, partial discharge (PD) plays a critical role during PD degradation. In this study, the PD characteristics of multilayer oil paper are focused on. In order to explore the characteristics of charge migration, the experiments of the relative permittivity, conductivity, isothermal surface potential decay, scanning electron microscopy and Fourier infrared spectroscopy have been carried out. The results show that the discharge branches of the second layer are two and three times longer than those in the first layer. In addition, the trap level of the first layer for PD degradation samples increases with the degree of PD degradation. The charges captured by deep traps provide seed charges for PD on the surface of the first layer. The charge transportation will accelerate the formation of shallow traps. The charge distribution and shallow traps contribute to the expansion of discharge branches.

Partial Discharge Signal Extraction Method Based on EDSSV and Low Rank RBF Neural Network

The detection process of partial discharge (PD) ultra-high frequency (UHF) signal is easily affected by white noise and periodic narrowband noise, which hinder the fault diagnosis of high-voltage electrical appliances. In order to extract PD UHF signal and suppress noise effectively, this paper provides a new method to detect PD UHF signal by EDSSV and low rank RBF neural network. Firstly, the singular value decomposition (SVD) is performed on the mixed noises of PD signal. Secondly, the peak index of energy difference spectrum of singular value (EDSSV) is selected as optimal singular value threshold, and then the periodic narrowband noise is eliminated by reconstructing the effective rank order. Finally, radial basis function (RBF) neural network is used to approximate the denoised PD signal, and Gaussian window filter is used to extract the PD signal. To verify the performance of the proposed method, we compared it with other three algorithms in simulation and field detection, including adaptive singular value decomposition (ASVD), singular value decomposition based on S-transform and MTFM (S-SVD) and EMD-WT algorithms. Particularly, four evaluation indices are designed for the detection data, which consider both the noise suppression and feature preservation. The results demonstrate the validity of the proposed method with higher signal-to-noise ratio and less waveform distortion.