| 1. |
- Liu, Daosheng, et al.
(author)
-
Magnetic Properties and Vibration Characteristics of Amorphous Alloy Strip and Its Combination
- 2019
-
In: IET Electric Power Applications. - : Institution of Engineering and Technology (IET). - 1751-8660 .- 1751-8679. ; 13:10, s. 1589-1597
-
Journal article (peer-reviewed)abstract
- Although the cores made with amorphous metal alloy have lowered no-load losses compared with the orientation silicon steel cores, a high cost and noise level are inevitable because the magnetostriction for amorphous metal alloy strip is larger than the ordinary one. This paper mainly focused on the experimental systems and methods for magnetic properties measurement, vibration characteristics and noise level of amorphous alloy strip and combinations. The vibration characteristics and noise level of amorphous alloy composite strip were also studied. The influence of annealing process on magnetic energy, vibration characteristics and noise level of amorphous alloy core were analyzed in detail as well. All the testing results and analysis above are helpful for the transformer manufacturers, and they can replace the expensive amorphous alloy metal strip with the combination ones to reduce the noise and the cost of the cores.
|
|
| 2. |
- Liu, Daosheng, et al.
(author)
-
Frequency-Domain Spectroscopy and Charge Trap Characteristics of Cellulose Based Pressboard Modified by Nano-TiO 2 Particles
- 2021
-
In: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 28:5, s. 1523-1530
-
Journal article (peer-reviewed)abstract
- Dielectric response and charge decay test are widely used for evaluating the electric properties of the insulation pressboards in the converter transformer. In this paper, Frequency Domain Spectroscopy (FDS) test, breakdown test, and charge decay characteristics experiments are carried out on the cellulose pressboards modified by TiO2 with different mass fractions and diameters. The FDS of the modified cellulose pressboards at ambient temperature is measured from 0.0001 to 1000 Hz by IDAX 300. The process is conducted at the laboratory to study the characteristics parameters of the dielectric response behaviors, such as complex relative permittivity. The results show that the values of the relative permittivity for the insulation pressboards modified by TiO2(5 wt%, 10 nm) are reduced. To verify the accurate results, the microstructures of the pressboards modified by 5 wt% with 10 nm diameter are observed by a Scanning Electron Microscope (SEM). The breakdown strength tests are carried on the samples modified by 1 wt%, 3 wt%, 5 wt%, 7 wt% with 10 nm TiO2 under the intensity electric and high-temperature field, respectively. The values of the breakdown strength are increased by 38% and 11.5% for single layer samples and oil/pressboard composite insulation models modified by 5 wt% nano-TiO2 filler. In addition, the charge decay characteristics are tested on the samples. The proper proportion additions can reduce the trap density.
|
|
| 3. |
- Liu, Daosheng, et al.
(author)
-
Investigation on heating aging mechanism of cellulose paper for oil-immersed transformer main insulation
- 2019
-
In: Proceedings - IEEE International Conference on Dielectric Liquids. - 2153-3733 .- 2153-3725. ; 2019-June:June
-
Conference paper (peer-reviewed)abstract
- Power transformer plays a vital role in maintaining reliable and efficient electricity supply. However, in service is increasing and growing older, much and much attention has been paid on their aging condition and life assessment than ever. The aging and degradation of transformer insulation will determine the life-time of its operation. The intensities of these depend on mechanical, thermal and environmental stresses that act on the insulations. Due to the temperature rise, the lifetime of insulation material will be shortened. The accelerated thermal aging method is often adopted to do some evaluation on the oil-paper insulation materials under different temperature for the thermal lifetime model. According to existing aging test, both insulation paper and mineral oil were aged at the same temperature. In this paper, the thermal aging experiments were implemented on the transformer main insulation model made with modified and unmodified insulation paper. The accelerated thermal aging tests were finished, and the superior electric characteristics of the nano-TiO2 and cellulose composition insulation were validated.
|
|
| 4. |
- Liu, Daosheng, et al.
(author)
-
Optimization of Mass Fraction and Particle Size of TiO2 Additives in Application of HVDC Transformer Insulation
- 2019
-
In: Proceedings - IEEE International Conference on Dielectric Liquids. - 2153-3733 .- 2153-3725. ; 2019-June
-
Conference paper (peer-reviewed)abstract
- With the fast development of high voltage direct current (HVDC) transmission technology, higher electrical insulation properties are demanded in application of HVDC converter transformers. The nano adding in the cellulose insulation is a kind of effect method to enhance their electrical insulation properties. In this paper, nano-TiO2 particles with four different diameters (5 nm, 10 nm, 20 nm and 30 nm) and four different loading ratios (1 wt%, 3 wt%, 5 wt% and 7 wt%) are added during preparation of the insulation cellulose paper. To evaluate their dielectric properties, DC breakdown test, partial discharge inception voltage test, the accumulating properties of the surface charge dynamics and trap distribution characteristic are performed on the prepared nano-TiO2 modified paper samples. The experimental results show that the DC breakdown voltage and the partial discharge inception voltage of oil-immersed composition insulating paper are significantly improved by adding nano-TiO2 particles. According to the testing data, the optimum combination of 10 nm particle size and 5 wt% mass fractions were obtained, and the modification mechanism of nano-TiO2 of the nano-composition insulation were presented in the paper.
|
|
| 5. |
- Liu, Daosheng, et al.
(author)
-
Suppression Mechanism of TiO 2 for the Partial Discharge of Oil-paper Insulation in Intensive Electric Field
- 2019
-
In: Proceedings - IEEE International Conference on Dielectric Liquids. - 2153-3733 .- 2153-3725. ; 2019-June
-
Conference paper (peer-reviewed)abstract
- With the rapid development of modern HVDC transmission technology, higher insulation properties are put forward on the oil-paper insulation system of the transformer, which determine the transformer service life to a certain extent. Traditional transformer oil-paper insulation is becoming increasingly difficult to meet the demands of insulation system with large capacity and miniaturization at ultra-high voltage level. In order to improve the insulation strength of oil-paper system, the insulation cellulose paper modified by TiO2 nanoparticles of different diameters (5 nm, 10 nm, 20 nm, 30 nm) were prepared, in addition, each of modified cellulose paper has different mass fraction of TiO2 nanoparticles (1%, 3%, 5%, 7% wt.). The partial discharge (PD) detection platform was established, and the partial discharge inception voltage (PDIV) values of the oil-paper insulation system with and without nanoparticles were measured. To investigate the PD characteristics, the PD waveforms and PD frequency spectrums of modified cellulose paper and the unmodified were obtained. The suppression mechanism of TiO2 nanoparticles on PD was explored through scanning electron microscope (SEM) observation. All the experiment results indicate that adding nano-TiO2 is beneficial to enhance the insulation properties of oil-paper insulation, and the optimum diameter and mass fraction of TiO2 nanoparticles to suppress oil-paper PD were obtained.
|
|
| 6. |
- Liu, Daosheng, et al.
(author)
-
Thermal Aging Effect on Properties of Pure and Doped Nano-TiO2 Cellulose Pressboard
- 2021
-
In: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 28:1, s. 133-141
-
Journal article (peer-reviewed)abstract
- In this research, nano-TiO2 of various diameters is added to cellulose and pressboard is made to enhance its anti-thermal aging characteristics. After thermally aging of the pressboard samples, partial discharge inception voltage (PDIV), AC breakdown strength and relative permittivity are measured. The results show that the dielectric properties of the pressboard made with 10 nm TiO2 has the highest AC breakdown due to closer match of the relative permittivity. The mechanical properties are higher than the unfilled cellulose samples. The change observed of the surface microstructure of the samples show that aging resistance of the filled samples are better than the unfilled samples.
|
|
