scholarly journals Partial Discharge Simulation of Air Gap Defects in Oil-Paper Insulation Paperboard of Converter Transformer under Different Ratios of AC–DC Combined Voltage

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6995
Author(s):  
Bing Luo ◽  
Jian Wang ◽  
Dong Dai ◽  
Lei Jia ◽  
Licheng Li ◽  
...  
Keyword(s):  
Fluid Model ◽  
Partial Discharge ◽  
Opposite Polarity ◽  
Air Gap ◽  
Mechanism Analysis ◽  
Surface Charges ◽  
Practical Operation ◽  
Discharge Simulation ◽  
Dc Component ◽  
Paper Insulation

A converter transformer is important primary equipment in a DC transmission project. The voltage on the valve side winding is complex when the equipment is running, including DC, AC, and AC–DC combined voltage. The insulation structure of the valve side winding of a converter transformer is an oil-paper insulation structure, which may have a variety of defects in the manufacturing stage and daily use, resulting in partial discharge. Therefore, it is the key to studying the partial discharge characteristics and mechanism of oil-paper insulation under AC–DC combined voltage. In this paper, we build a two-dimensional air gap model of oil-paper-insulated pressboard considering the actual particles and actual reaction based on the fluid model. The characteristics and evolution mechanism of partial discharge (PD) in pressboard under different AC/DC combined voltages are studied by numerical simulation. The results show that when the DC component increases, the polarity effect of partial discharge is more obvious, while the potential and discharge intensity in the air gap decrease. Further analysis revealed that the DC component in the combined voltage accumulated a large number of surface charges on the surface of the air gap, and the space charge distribution was more uniform and dispersed, which generated an electric field with opposite polarity to the DC component in the air gap and, then, inhibited the development of local discharge in the paperboard. The results of the simulation are consistent with the previous experimental phenomena, and the mechanism analysis of the simulation results also verifies the previous analysis on the mechanism of experimental phenomena. This will lay a theoretical foundation for the further study of partial discharge phenomenon of oil-paper insulation structures in practical operation in the future.

Studies of the effect of temperature on charge accumulation in PVDF-PMMA double-layered thin films based on depolarization current measurements

2021 ◽  
pp. 009524432199640
Author(s):  
Pooja Saxena ◽  
Prashant Shukla
Keyword(s):  
Thin Films ◽  
Polyvinylidene Fluoride ◽  
Short Circuit ◽  
Charge Trapping ◽  
Opposite Polarity ◽  
Air Gap ◽  
Excess Charge ◽  
Polarization Current ◽  
Surface Charges ◽  
Depolarization Current

In this paper, we have reported the interpretation of air gap (Thermally Stimulated Depolarization Current) of surface charges in PVDF-PMMA (Polyvinylidene fluoride (PVDF)–Polymethyl methacrylate (PMMA)) double-layered polymer thin films whose decay could not be observed in metalized electrets with short-circuit TSDC. Since short-circuit TSDC is caused by the relaxations of homo- and hetero-charge flow in one direction and thus makes it difficult to identify, separate, and characterize its components, therefore, an air gap was introduced to the short-circuit TSDC technique to carry out air-gap TSDC. This technique enables one to observe the orientation of dipoles, excess charge decay by ohmic conduction, and decay of surface charge. When a dielectric is charged by an application of an external field, two charges with opposite polarity and different nature can be found. Air-gap TSDC’s of double-layer samples revealed the presence of homo charge; charges trapped at the surface are due to dissipation of space charges thus, the depolarization current is observed to have the same polarity as that of the polarization current. Hetero-charge persists at high temperatures due to the bulk polarization formed because of the electric field created by the homo-charge. Hence, the depolarization current observed in the present study was observed to be of opposite polarity as that of polarization current. The above discussed polymeric layered structure was found to be a source of charge trapping which was identified and confirmed by various calculated parameters.

Development of the Partial Discharge Inception Calculation Model in a Non-uniform Air Gap Considering the Effect of Humidity

2011 ◽  
Vol 131 (12) ◽  
pp. 1017-1023 ◽  
Author(s):  
Norihito Yanagita ◽  
Tatsuro Kato ◽  
Toshiaki Rokunohe ◽  
Takeshi Iwata ◽  
Hiroki Kojima ◽  
...  
Keyword(s):  
Partial Discharge ◽  
Calculation Model ◽  
Air Gap

Failure Mechanism Analysis of Electromagnetic Relay under Mechanical Impact

2013 ◽  
Vol 473 ◽  
pp. 39-45 ◽  
Author(s):  
Guo Wei Zhao ◽  
Yong Chen ◽  
De Yong Li ◽  
Bin Tang
Keyword(s):  
Failure Mechanism ◽  
Magnetic Circuit ◽  
Impact Damage ◽  
Engineering Application ◽  
Air Gap ◽  
Mechanism Analysis ◽  
Mechanical Impact ◽  
Electromagnetic Relay ◽  
Electromagnetic Relays ◽  
The Impact

The aim was to analyze failure mechanism of electromagnetic relay caused by mechanical impact. The principle of electromagnetic relays was studied and the effect of mechanical impact on electromagnetic relays was analyzed in this paper. Based on the established magnetic circuit model, the relationship of the magnetic field strength, the electromagnetic attraction and the impact damage degree was studied. Then, the damage intensity of mechanical impact on magnetic circuit was decided. Afterwards, the structure of electromagnetic relays was improved, and the mechanical impact simulation was studied by ANSYS. The results show that the uncontrollability of electromagnetic relay is mainly caused by air gap, which is aroused by mechanical impact; in addition, the size of air gap is inversely proportional to electromagnetic attraction force. Moreover, the improved structure of relays can increase impact resistance and broaden the scope of engineering application of electromagnetic relay.

Sign in / Sign up

Export Citation Format

Share Document