LEE- Elektrik Mühendisliği Lisansüstü Programı

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http://hdl.handle.net/11527/19259

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Konu "AC applications" ile LEE- Elektrik Mühendisliği Lisansüstü Programı'a göz atma
  • Öge
    Investigation of electrical, thermal and chemical characteristics of zinc borate-filled htv silicone rubber composites
    (Graduate School, 2023) Özdemir, İdris ; İlhan, Suat ; 826421 ; Electrical Engineering Programme
    For more than 40 years, high-voltage AC systems have used silicone insulators due to their better performance in terms of pollution, ease of installation, and low-weight properties. However, understanding is constrained by AC applications because of usage in HVAC systems. On the contrary, the HVDC application is limited due to the restricted amount of usage of silicone insulators in this area. However, because of the advantage that transferring power over extremely long distances such as interconnection between countries via HVDC system is more economical than HVAC transmission. Therefore, there is a need for silicone insulator applications in HVDC transmission. However, the silicone insulators are exposed to corona discharge under DC and AC high voltage. This causes a loss of hydrophobicity on the surface of silicone insulators. Hydrophobicity means that the surface repeals the water. Therefore, the contamination path is not occurring over the insulator. If it losses this property, some discharge event will happen on the surface. And high-temperature areas will reveal on the surface. Then in that area, erosion can occur. Therefore, the silicone insulator's thermal behavior needs to be enhanced. Therefore, to increase the thermal characteristic of these insulators, some special fillers such as ATH and Silica can be used. Considering the literature and industry, these two fillers are the most widely used and investigated ones. Especially, ATH has a property that can be used as a fire retardant filler in composites. It consists of hydrated water which after a certain point of temperature, it releases this hydrated water content to decrease the internal temperature of the composite. Furthermore, in the insulator, it can protect insulators from tracking and erosion which occur due to discharge events. Because the silicone insulators can regain the hydrophobicity property after a short amount of time. On the other hand, there is another filer compound that acts in similar behavior to ATH called zinc borate. Similar to ATH it has hydrated water inside the filler compound. Therefore, it can be used as a fire retardant filler inside the composite. There limited amount of literature that consists of ZB usage in composite such as rubbers, PVC, and epoxy. The idea behind the utilize the ZB filler in the silicone insulators is that Turkiye has around 73% of boron mines over the world. The succession of this idea can contribute to Turkiye in terms of economic aspects. Additionally, ZB has the properties of fire-retardant, smoke and afterglow-suppressing, and anti-tracking agents. Therefore, it can be a good replacement for ATH filler. Furthermore, a high ATH filler rate needs to be used in the silicone insulators to pass some tests such as the inclined plane test, dynamic drop, and corona discharge test that utilize to evaluate the performance of silicone insulators. Therefore, with a lower amount of ZB filler, silicone insulator samples can succeed in these tests. Additionally, there is some indication of a synergistic relationship between ATH and ZB when the literature is examined. In the combination of ATH and ZB mixtures, ZB acts as a smoke suppressant and creates a barrier on the surface. ATH acts as a fire retardant in the composite. With the scope of the thesis, 4 distinct type of samples contain HTV silicone as the base material as manufactured. These are pure HTV samples, ZB samples, ATH samples, and ATH/ZB mixture samples. Each type has a different amount of filler rate. For example, ZB samples have 5%, 10%, 15%, 20%, and 30% rates of ZB filler. And they are named depending on filler rate. For example, ZB5 consists of 5 percent of ZB filler and 95 percent of HTV silicone. Furthermore, the ATH samples are ATH10, ATH20, ATH30 and ATH50. Lastly, ATH&ZB mixture samples are ATH10ZB10, ATH20ZB10, ATH30ZB10 and ATH30ZB20. These samples are called similar to ATH and ZB samples. For example, ATH10ZB10 comprises 10 percent of ATH and 10 percent of ZB, and the remaining is 80 percent of HTV silicone. And addition to that samples, in order to compare the samples, pure HTV samples which consist of only base HTV silicone is also manufactured. To determine the physical behavior of the samples, density, contact angle, hardness, and surface roughness measurements are utilized. The density of ATH and ZB is higher than the base HTV silicone. Therefore, as aspected, the density and hardness of the final product that consists of filler are increasing with the addition of filler. Moreover, the density and hardness of the ZB sample are higher than the ATH sample which contains the same amount of filler. If the ZB30, ATH30, and ATH20ZB10 samples which comprise 30 percent of filler are compared, the highest density and hardness belongs to ZB30. And the lowest one is ATH30. Furthermore, there is no clear relationship between contact angle and filler rate or type. The highest contact angle belongs to ATH10ZB10. The relationship between surface roughness and filler type or rate is also unrelated in terms of surface roughness measurement. In the following part, the thermal investigation of samples will be given. In this context, to reveal the thermal behavior of the sample, thermogravimetric analysis(TGA), differential thermal analysis (DTA), and thermal conductivity analyses are done. According to thermal conductivity, increasing the filler rate of ATH and ZB increases the thermal conductivity accordingly. Additionally, the TGA and DTA analyses show that as zinc borate concentrations rise, more hydrated water is discharged. When compared to the zinc borate sample, ATH had a significantly higher released water content. The amount of water dehydration rises with the ATH filling rate when the mixture samples are monitored. For chemical structural examination, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) investigations are used. According to the SEM image Due to the low particle size of ATH, the particle size of the ATH50 sample is more uniform. When the SEM picture of ATH30ZB20 is examined, a diversity of particle sizes may be found due to ZB's high particle size. Furthermore, The ZB samples have no -OH bonds, according to FTIR analysis. However, this bond is readily apparent in the ATH samples. On the other hand, the peak of -OH bond transmittance is dramatically increased by rising the ZB by 10%, when ATH30ZB10 and ATH30ZB20 are examined. Lastly, in order to examine the tracking and erosion performance of samples, an experiment called the inclined plane test is applied to samples. this experiment can be applied under AC and DC voltage. For the AC there is a special IEC standard that shows the procedure of the experiment. On the contrary, there is no particular standard for DC applications. Therefore, to examine the DC behavior of the samples, literature is used. For AC application, the voltage magnitude is 3.5 kV. In each test, 5 samples are tested. If all these 5 samples pass the experiment, the voltage magnitude is increasing to 4.5 kV and the experiment is repeated. On the other hand, for DC application, both polarity is used. For +DC, the voltage magnitude is 2.45 kV, and for -DC application, the applied voltage is -3.15 kV. These values are applied considering the literature review of the DC application of IPT. According to the 3.5 kV AC application of IPT, every sample of ATH50 and ATH30ZB20 passed the test. When compared to a pure HTV sample, ZB filler has a detrimental effect. Furthermore, there is a slight improvement with increasing ATH concentration at the low rate of filler. However, due to synergistic effect between ATH and ZB mixture samples gives better results in terms of duration time. In addition to that, ATH50 and ATH30ZB20 samples are tested under 4.5 kV AC. Similarly, they passed this voltage magnitude as well. For + DC and -DC, the IPT experiment provides a similar result to the AC application. Under 2.45 kV +DC voltage, all samples of ATH50 and ATH30ZB20 passed the experiment successfully. If the samples that contain 30 % filler such as ZB30, ATH30, and ATH20ZB10, due to the synergistic effect of ATH and ZB, the result of ATH20ZB10 is slightly better than ATH30 and ZB30. Lastly, under -3.15 kV -DC voltage, four out of five samples of ATH50 successfully passed the experiment. On the other hand, the all sample of ATH30ZB20 samples passed the experiment. In conclusion, in terms of electrical application, the mixture samples have the highest performance in the IPT experiment. It gives slightly better improvement than ATH samples.