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Partial Discharge Process and Characteristics of Oil-Paper Insulation under Pulsating DC Voltage
Lianwei Bao,Jian Li,Jing Zhang,Tianyan Jiang 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.2
Oil-paper insulation of valve-side windings in converter transformers withstand electrical stresses combining with AC, DC and strong harmonic components. This paper presents the physical mechanisms and experimental researches on partial discharge (PD) of oil-paper insulation at pulsating DC voltage. Theoretical analysis showed that the phase-resolved distributions of PDs generated from different insulated models varied as the increase of the applied voltages following a certain rule. Four artificial insulation defect models were designed to generate PD signals at pulsating DC voltages. Theoretical statements and experimental results show that the PD pulses first appear at the maximum value of the applied pulsating DC voltage, and the resolved PD phase distribution became wider as the applied voltage increased. The PD phase-resolved distributions generated from the different discharge models are also different in the phase-resolved distributions and development progress. It implies that the theoretical analysis is suitable for interpretation of PD at pulsating DC voltage.
Lianwei Bao,Jian Li,Jing Zhang,Xudong Li 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.6
Insulation of valve-side windings in converter transformer withstands pulsating voltages, which will produce more serious insulation problems. In this paper, the electric breakdown experiments of oil-paper insulation specimens were executed at pulsating voltages and different temperatures. Experiment and analysis results showed that the breakdown voltage decreased with increasing temperature under pulsating voltage. The influence of temperature proves to be more significant once the temperature exceeds a limitation threshold. A fitting formula between breakdown voltage and the temperature was reported. Finally, in order to clearly understand the breakdown properties under pulsating voltage, the electric field distribution and space charge behavior under pulsating voltage at different temperature were discussed.
Bao, Lianwei,Li, Jian,Zhang, Jing,Li, Xudong The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.6
Insulation of valve-side windings in converter transformer withstands pulsating voltages, which will produce more serious insulation problems. In this paper, the electric breakdown experiments of oil-paper insulation specimens were executed at pulsating voltages and different temperatures. Experiment and analysis results showed that the breakdown voltage decreased with increasing temperature under pulsating voltage. The influence of temperature proves to be more significant once the temperature exceeds a limitation threshold. A fitting formula between breakdown voltage and the temperature was reported. Finally, in order to clearly understand the breakdown properties under pulsating voltage, the electric field distribution and space charge behavior under pulsating voltage at different temperature were discussed.
Partial Discharge Process and Characteristics of Oil-Paper Insulation under Pulsating DC Voltage
Bao, Lianwei,Li, Jian,Zhang, Jing,Jiang, Tianyan,Li, Xudong The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.2
Oil-paper insulation of valve-side windings in converter transformers withstand electrical stresses combining with AC, DC and strong harmonic components. This paper presents the physical mechanisms and experimental researches on partial discharge (PD) of oil-paper insulation at pulsating DC voltage. Theoretical analysis showed that the phase-resolved distributions of PDs generated from different insulated models varied as the increase of the applied voltages following a certain rule. Four artificial insulation defect models were designed to generate PD signals at pulsating DC voltages. Theoretical statements and experimental results show that the PD pulses first appear at the maximum value of the applied pulsating DC voltage, and the resolved PD phase distribution became wider as the applied voltage increased. The PD phase-resolved distributions generated from the different discharge models are also different in the phase-resolved distributions and development progress. It implies that the theoretical analysis is suitable for interpretation of PD at pulsating DC voltage.
Mechanical and Creep Properties of Concrete containing Apricot Shell Lightweight Aggregate
Fan Wu,Changwu Liu,Wei Sun,Lianwei Zhang,Yuanjun Ma 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7
In this study, the mechanical and creep properties of the apricot shell (AS) as a replacement for the coarse aggregate were investigated. The alternative volume ratio of the coarse aggregate was set as 0%, 25%, 50%, 75% and 100%, respectively. The results showed that the coarse aggregate was completely replaced by the AS, the compressive strength, splitting tensile and flexural strength, and modulus of elasticity of apricot shell concrete (ASC) were 26.1 MPa, 1.85 MPa, 3.18 MPa, and 9.3 GPa, respectively, and decreased by 32.6%, 30.7%, 24.8%, and 34.5% compared to the concrete without AS, respectively. However, the oven dry density of AS100 mixture was 1,762 kg/m3, which fulfilled the density requirement of structural lightweight aggregate concrete (LWAC). The creep strain of concrete increased by increasing AS content. When the coarse aggregate was replaced by 100% AS, the strain of AS100 mixture at 380 hours was 16.84 × 10−4. The results indicate that LWAC with an acceptable performance can be produced by using AS as coarse aggregates in concrete.