Analysis of Phase Resolved Partial Discharge Patterns of Kraft Paper Insulation Impregnated in Transformer Mineral oil

2020 ◽  
Author(s):  
K M Mahesh Kumar ◽  
B Ramachandra ◽  
L Sanjeev Kumar
Keyword(s):  
Partial Discharge ◽  
Mineral Oil ◽  
Kraft Paper ◽  
Discharge Patterns ◽  
Paper Insulation

scholarly journals Development Processes of Surface Trucking and Partial Discharge of Pressboards Immersed in Mineral Oil: Effect of Tip Curvatures

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 554 ◽  
Author(s):  
Bo Gao ◽  
Rui Yu ◽  
Guangcai Hu ◽  
Cheng Liu ◽  
Xin Zhuang ◽  
...  
Keyword(s):  
High Speed ◽  
Weak Link ◽  
Partial Discharge ◽  
Mineral Oil ◽  
Tangential Component ◽  
Surface Tracking ◽  
Damage Degree ◽  
Development Processes ◽  
Paper Insulation

The pressboard surface is the electric weak link of the oil-paper insulation in transformers, and long-term partial discharge (PD) erosion is the dominant cause of degradation in pressboard. To explore the development processes of surface tracking under the effect of tip curvature, the typical needle-plate model was selected to initiate an electric field with a high tangential component on pressboard surface under needle tip curvature of 4~42 μm. With the help of a high-speed camera and a PD detecting system, the development processes of surface tracking and PD were recorded under a sustained AC voltage. A profound difference between surface tracking under different curvatures was discussed. Pressboard surfaces after tests were observed under a scanning electron microscope (SEM), and the damage degree of cellulose fibers was dependent on the tip curvature.

scholarly journals Applying HF and VHF/UHF Partial Discharge Detection for Distribution Transformer

2020 ◽  
Author(s):  
Sakda Maneerot ◽  
Masaaki Kando ◽  
Norasage Pattanadech
Keyword(s):  
High Frequency ◽  
Partial Discharge ◽  
Mineral Oil ◽  
Surface Discharge ◽  
Distribution Transformer ◽  
Impregnation Process ◽  
Distribution Transformers ◽  
Insulating Liquid ◽  
Paper Insulation ◽  
Natural Ester

This paper represents application of high frequency (HF) and very high frequency/ultrahigh frequency (VHF/UHF) partial discharge (PD) detection for a distribution transformer. A capacitive sensor is used to detect the HF electric field caused by charge transfer inside oil–paper insulation due to PD at the defect site, and an electromagnetic sensor or antenna is used for detecting electromagnetic PD transients in the air outside the investigated transformer in the near-field region. Three types of artificial PD sources in air and insulating liquid, which are corona discharge, surface discharge and air void discharge in pressboard, were investigated. Three identical distribution transformers were rated at 22 kV, 400 V and 50 kVA, and were designed and constructed. The first transformer was filled with mineral oil, the second was filled with natural ester and the third was filled with palm oil. The PD generated by the air-filled voids in the insulating papers and pressboards of these transformers with five different conditions were investigated, i.e., non-impregnated paper, impregnated paper for 3 hours, 6 hours, 9 hours and 12 hours. The impregnation process was done with 65°C liquid temperature, and the pressure in the oven was around 5 mbar. From the experimental results, it can be concluded that the electromagnetic PD transients radiated from the corona discharge of both high-voltage (HV) and low-voltage sides in the air are in the VHF range, and surface discharge frequency is extended up to the UHF range. For the PD in the insulating liquid, the phase resolved PD (PRPD) pattern in the HF range is a valuable tool to characterize the PD sources. The PD in an air-filled void inside the insulating paper of the mineral oil transformer is obviously different compared with those of the natural ester transformer and the palm oil transformer. For the manufacturing of distribution transformers in this research, it is found that after the paper insulation is dried out, the impregnation process for a period of 9 hours is suitable for improving the oil–paper insulation with an acceptable PD level. This paper is the cross-field application by applying the antenna and communication theory for detecting the discharge problems in HV equipment.

scholarly journals Effects of Plasma Treated Alumina Nanoparticles on Breakdown Strength, Partial Discharge Resistance, and Thermophysical Properties of Mineral Oil-Based Nanofluids

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3610
Author(s):  
Norhafezaidi Mat Saman ◽  
Izzah Hazirah Zakaria ◽  
Mohd Hafizi Ahmad ◽  
Zulkurnain Abdul-Malek
Keyword(s):  
Thermal Conductivity ◽  
Plasma Treatment ◽  
Base Fluid ◽  
Breakdown Strength ◽  
Partial Discharge ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Alumina Nanoparticles ◽  
Discharge Characteristics ◽  
Nano Alumina

Mineral oil has been chosen as an insulating liquid in power transformers due to its superior characteristics, such as being an effective insulation medium and a great cooling agent. Meanwhile, the performance of mineral oil as an insulation liquid can be further enhanced by dispersing nanoparticles into the mineral oil, and this composition is called nanofluids. However, the incorporation of nanoparticles into the mineral oil conventionally causes the nanoparticles to agglomerate and settle as sediment in the base fluid, thereby limiting the improvement of the insulation properties. In addition, limited studies have been reported for the transformer oil as a base fluid using Aluminum Oxide (Al2O3) as nanoparticles. Hence, this paper reported an experimental study to investigate the significant role of cold plasma treatment in modifying and treating the surface of nano-alumina to obtain a better interaction between the nano-alumina and the base fluid, consequently improving the insulation characteristics such as breakdown voltage, partial discharge characteristics, thermal conductivity, and viscosity of the nanofluids. The plasma treatment process was conducted on the surface of nano-alumina under atmospheric pressure plasma by using the dielectric barrier discharge concept. The breakdown strength and partial discharge characteristics of the nanofluids were measured according to IEC 60156 and IEC 60270 standards, respectively. In contrast, the viscosity and thermal conductivity of the nanofluids were determined using Brookfield DV-II + Pro Automated viscometer and Decagon KD2-Pro conductivity meter, respectively. The results indicate that the 0.1 wt% of plasma-treated alumina nanofluids has shown the most comprehensive improvements in electrical properties, dispersion stability, and thermal properties. Therefore, the plasma treatment has improved the nanoparticles dispersion and stability in nanofluids by providing stronger interactions between the mineral oil and the nanoparticles.

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