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The oil-paper insulation in converter transformers is subjected to pulsating DC voltage, mainly consisting of AC and DC voltages. Surface partial discharges (PDs) occurred in converter transformer is significantly influenced by voltage type as well as moisture content in oil-impregnated paper insulation. The influence of moisture content on surface PD behaviors of oil-impregnated paper insulation...
The valve side Wingdings of converter transformers withstand complex electric stress, and the minor insulation of converter transformers withstand combined fundamental AC and harmonic voltages. Surface partial discharge is a main form of discharge occurring in minor insulation and there is a severe lack of empirical research on surface partial discharge in oil-impregnated insulation paper at harmonic...
This paper presents simulation and experiments of UHF detection for partial discharge (PD) in power transformers. Simulations of PD electromagnetic waves propagating in simulated transformer tank, by finite difference time domain (FDTD) approach, were implemented to examine the effects of electromagnetic wave refraction and reflection by transformer components. Actual PD experiments in simulation...
The converter transformer is one of the most critical equipment in high-voltage direct current (HVDC) transmission systems. Valve-side windings withstand complex stresses combined with AC, DC, and pulse voltages. Oil-paper insulation is used within most of HVDC converter transformers. Partial discharge (PD) in oil-paper insulation is a major reason for the development of internal faults in HVDC converter...
In this paper, focus is made on partial discharge (PD) activity in oil-impregnated pressboard used in converter transformers. Voltages over the main insulation of the valve-side windings of the converter transformer were analyzed using the PSIM software. Next, transformer defects were simulated by insulation models to generate PD signals. The dependence of PD inception voltage (PDIV) on the AC plus...
This paper presents an approach for calibration of ultra-high-frequency (UHF) partial discharge (PD) signals in high voltage direct current (HVDC) transformer. A linear relationship between the amplitude of the UHF PD signal and PD apparent charge was obtained through the theoretical analysis. The finite-difference time-domain (FDTD) model of the simulated converter transformer showed that the UHF...
One of the major insulations of high voltage direct current (HVDC) converter transformers is oil-paper insulation. Valve-side windings withstand complex stresses combined with AC, DC, and pulse voltages. Partial discharge in oil-paper insulation is a major incipient fault of an HVDC converter transformer inside insulation. There are few studies on the development characteristics of partial discharge...
Ultra-high-frequency (UHF) approaches, when used to detect partial discharge in converter transformers, can avoid the impulse interference generated by converter valve, thus contributing to high sensitivity. The electromagnetic waves (EM-waves) propagation in transformer could be affected by transformer components and other factors. In this paper, a simulation model of converter transformer was built...
Partial discharge (PD) online monitoring is an effective tool of inspecting insulation defects and identifying potential faults in power transformers. Ultra-high-frequency (UHF) approaches have caught increasing attention recently and been considered as a promising technology for online monitoring PD signals. The size of a UHF sensor for PD online monitoring of transformer is a critical factor for...
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