A Study on the Effectiveness of Partial Discharge Models for Various Electrical Machines’ Insulation Materials (original) (raw)
Related papers
IEEE Access, 2020
Partial discharges (PD) are produced in the stator insulation of electrical machines while energized. The sources of PD are internal voids, crack, and manufacturing defects, which keep on extending with its normal operation, leading to the complete failure of insulation. The intensity of PD is considerably influenced by the environmental factors, including surrounding temperature, pressure, humidity, and contamination. This paper investigates the influence of these factors on the PD activity in electrical machines and estimates the lifetime of insulation. The PD measurements were conducted by placing the motors in a climate-controlled chamber. The PD trend under varying environmental stresses was investigated over time. Accordingly, PD inception voltage and various discharge characteristic parameters such as accumulated apparent charge, cumulative energy function, average discharge current, discharge power, and quadratic rate have been determined. The combined effect of various environmental stresses on the PD activity was also investigated. The mathematical relationships were developed to estimate the discharge characteristics as the functions of pressure and temperature using the Gaussian model and the Exponential model. Finally, the endurance of insulation was estimated under different environmental conditions based on the average discharge current to differentiate between correct and incorrect PD measurements and to develop a right maintenance schedule for motors in service. INDEX TERMS Environmental stress, lifetime assessment, low voltage motors, insulation, partial discharge.
Partial Discharge Theory, Modeling and Applications To Electrical Machines
2005
Partial discharge monitoring is an effective on-line predictive maintenance test for motors and generators, as well as other electrical distribution equipment. The benefits of on-line testing allow for equipment analysis and diagnostics during normal production. Corrective actions can be planned and implemented, resulting in reduced unscheduled downtime. This paper will present a theory to promote the understanding of partial discharge technology, as well as various implementation and measurement techniques that have evolved in the industry. Then insulation modeling and partial discharge modeling in electrical machines will be introduced. At last traditional partial discharge test methods in electric machines will compare to new method of partial discharge monitoring and corrective actions will interpret.
Energies
In Power Systems, Synchronous Generators (SGs) are mostly used for generating electricity. Their insulation system, of which epoxy resin is a core component, plays a significant role in reliable operation. Epoxy resin has high mechanical strength, a characteristic that makes it a very good material for reliable SG insulation. Partial Discharges (PDs) are a constant threat to this insulation since they cause deterioration and consequential degradation of the aforementioned material. Therefore, it is very important to detect PDs, as they are both a symptom of insulation deterioration and a means to identify possible faults. Offline and Online PDs Tests are described, and a MATLAB/Simulink model, which simulates the capacitive model of PDs, is presented in this paper. Moreover, experiments are carried out in order to examine how the flashover voltage of epoxy resin samples is affected by different humidity levels. The main purpose of this manuscript is to investigate factors, such as t...
Towards a partial discharge free insulation system for the More Electrical Transportation
2020
The research work of this thesis aims to provide new tools to correctly design, qualify and monitor the insulation system of electric motors for the transport sector. These are in fact called to meet performance and reliability requirements much higher than those required by the industrial sector. Moreover, they are subjected to much more aggressive environmental conditions (humidity, altitude and temperature changes) and frequent and sudden changes of the working point. The system that makes the most of this paradigm shift is the electrical insulation system, since, at the same time, it increases the nominal voltage, increases the transients due to the use of low-level inverters and reduces the available space. Currently, electric motor manufacturers install a ground and turn insulation capable of withstanding normal operating voltages without exceeding the dielectric strength of the chosen material. However, if the electric field generated during operation exceeds the dielectric strength of the air and the are some cavities inside the motor, there are pre-discharge phenomena, which accelerate the degradation of the insulation (which, being organic in nature, suffers the effect of electronic bombardment). This lead to a shortening of the useful life of the machine and very often causes premature failure. In general, engineers design the insulation of the machine based on experience and adapting existing solutions. Very often this leads to system over-dimensioning and an avoidable performance deterioration. Moreover, it often does not even guarantee the required reliability. Therefore, the first aim of this thesis was to develop a model capable of determining the so-called Partial Discharge Inception Voltage (PDIV) for random-wound machines (which for the time being remain the most common in this area) and to allow a more precise design of their insulation, allowing optimization of weight and performance. A substantial part of the research has been invested in measuring the PDIV of a multitude of specimens, being of fundamental importance for the design of the stator winding insulation, and in the study of the different environmental parameters that can affect this phenomenon. This study has always been compared with the existing standards (IEC 60034-18), to highlight the points that should be reviewed in the future in the light of the increasing vehicles' electrification. In particular, it was found that altitude and humidity can have a significant impact on insulation. The higher the value of these two parameters, the lower the PDIV of the insulation system. This must be considered during both the design and test phases. Both in the scientific community and in the various technical committees, the impact of using the inverter has also been discussed for years. In this regard, it is critical to understand whether it is necessary to use a voltage wave with similar characteristics to those of service during testing, or it is possible to use a conventional AC generator with a power frequency (cheaper and allowing measures with a much better signal-to-noise ratio). From the measurements made, it has been observed that PDIV does not vary according to frequency and that it tends to be higher as the voltage crests' rise-time decreases. This means that the use of a power frequency AC generator for PD testing is not only possible, but also recommended when testing phase-to-phase and phase-to-ground insulation, because more conservative. Thanks to the large collection of data obtained, it was possible to develop a physical-mathematical approach for the evaluation of the dielectric performance of the insulation, formed by the insulating enamel of the wires (or the slot liners) and the surrounding air, in electric motors for different environmental operating conditions. The algorithm developed has provided the basis for the drafting of a real program (called Discharge) that, assisted by FEM software, allows to analyze in detail various types of motors (random-wound, hairpin, concentrated windings, etc.). Finally, several accelerated ageing tests were conducted, applying different types of stress. In one case, flight conditions were simulated, referring to the aeronautical application of an actuator. In another situation, the impact that frequent start-and-stops have on the service life of an electric motor was studied. It was found that, although PDIV decreases with altitude, the partial discharge activity within the insulation system is less dangerous than on the ground (the service life, with the same over-stress, is longer). On the other hand, it is confirmed that frequent start-and-stops shorten the service life of the insulation, due to the combination of mechanical and thermal stresses. This could force us in the future to include in the standard a specific test to take account of this additional factor, which is new to the world of low-voltage electric motors.
IEEE Electrical Insulation Magazine, 2000
Mengingat sifat minyak mineral yang sulit terurai secara alami dan rentan terhadap bahaya kebakaran, minyak sawit diusulkan sebagai minyak isolasi alternatif. Makalah ini membahas pelepasan sebagian (PD) dalam minyak sawit di bawah tegangan sinusoidal dan perbandingan dengan minyak mineral. PD dibangkitkan dengan menggunakan elektroda jarum-plat, yang memungkinkan peninggian medan listrik di ujung elektroda jarum. Pulsa-pulsa PD dideteksi dengan detector RC dan diukur menggunakan sistem pengukuran berbasis komputer. Hasil-hasil menunjukkan bahwa karakteristik PD dalam kedua minyak adalah sama. PD terjadi pertama kali pada polaritas negatif. PD terjadi pada kedua polaritas tegangan dengan jumlah PD lebih besar pada polaritas negatif. Beberapa penomena peluahan mengindikasikan kehadiran muatan ruang yang mengubah medan listrik dan mempengaruhi aktivitas PD disamping medan utama dari aplikasi tegangan.
IEEE Transactions on Industrial Electronics, 2000
The aim of this paper is to present a method for modeling the lifespan of insulation materials in a partial discharge regime. Based on the design of experiments, it has many advantages: it reduces the number of time-consuming experiments, increases the accuracy of the results and allows lifespan modeling under various stress conditions including coupling effects between the factors. Accelerated aging tests are carried out to determine the lifespan of these materials. The resulting model presents an original relationship between the logarithm of the insulation lifespan and that of electrically applied stress and an exponential form of the temperature. Results show that the most influential factors can be identified according to their effects on the insulation lifespan. Moreover, the lifespan model validity is tested either with additional points which have not been used for modeling or through statistical tests. Finally, it is shown that fractional plans are not suitable to r e d u c e t h e n u m b e r o f e x p e r i m e n t s. T h i s a p p l i c a t i o n o f t h e experimental design is best used during the initial phase, before the final drive has been built and any on-line diagnostic.
A REVIEW OF STUDY AND PERFORMANCE OF PARTIAL DISCHARGE FOR DIFFERENT TYPE OF INSULATION MATERIALS
International Journal of Engineering Technologies and Management Research, 2018
The insulation should be high quality for power transmission and high voltage application, in this way we are studying about the various type of insulation material such as epoxy resin, vulcanized fibres and polyethylene which are having different capacitance value, the power transmission equipment’s has less efficiency due to degradation of insulation material. In this paper, we are studying the partial discharge for the different type of insulation materials.
IEEE Access
In this paper, the results obtained from lab tests on twisted pairs subjected to different voltage waveforms and atmospheric conditions are used to propose how to modify the IEC Std. 60034-18-41. The goal is to make the standard suitable for the More Electrical Aircraft (MEA). The results show that it is initially necessary to screen out materials through simple tests. The enhancement factors for temperature can be modified to consider reduced pressures and temperatures using a simple model. The aging enhancement factor can be reduced considering the reduced sensitivity of the partial discharge inception voltage (PDIV) at low pressures on the enamel thickness. Eventually, reference will be made to the drive discussed in Part I of this series to draw conclusions about the likelihood of partial discharge inception in a random wound stator and how to reduce it by modifying either the inverter or the stator insulation. Reference to a random wound motor is made throughout the paper. INDEX TERMS Partial discharges, More Electrical Aircraft, wide bandgap devices, SiC inverter, qualification, aging. The following are the issues that are most likely to affect the reliability of inverter-fed random wound motors:
IEEE Transactions on Dielectrics and Electrical Insulation, 2015
This paper presents new approach to using Partial Discharge (PD) data for the prediction of the Remaining Useful Life (RUL) of dielectric materials undergoing breakdown. The method presented uses a thermodynamic macro-model in conjunction with an artificial neural network to associate the features in the PD data detected during breakdown to the electrical tree characteristics. The method is presented using electrical tree simulation data from a new dielectric breakdown simulation model. The simulation model is confirmed using experimental data.