Transformer On-line Monitoring Research Articles

Optimization of UHF Hilbert Antenna for Partial Discharge Detection of Transformers

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 practical installation inside transformer. This communication presents a compact fourth order UHF Hilbert fractal antenna with desired performance and suitable size for easy installation. Actual PD experiments were carried out for four typical artificial insulation defect models while the antenna was used for PD measurements. The experimental results show that the proposed Hilbert fractal antenna is suitable and effective for UHF online monitoring of PDs in transformers.

Resonant Frequency Calculation and Optimal Design of Peano Fractal Antenna for Partial Discharge Detection

Ultra-high-frequency (UHF) approaches have caught increasing attention recently and have been considered as a promising technology for online monitoring partial discharge (PD) signals. This paper presents a Peano fractal antenna for UHF PD online monitoring of transformer with small size and multiband. The approximate formula for calculating the first resonant frequency of the Peano fractal antenna is presented. The results show that the first resonant frequency of the Peano fractal antenna is smaller than the Hilbert fractal antenna when the outer dimensions are equivalent approximately. The optimal geometric parameters of the antenna were obtained through simulation. Actual PD experiments had been carried out for two typically artificial insulation defect models, while the proposed antenna and the existing Hilbert antenna were both used for the PD measurement. The experimental results show that Peano fractal antenna is qualified for PD online UHF monitoring and a little more suitable than the Hilbert fractal antenna for pattern recognition by analyzing the waveforms of detected UHF PD signals.

Research on the Oil-Gas Permeability of Mixed Hollow Fiber Membrane Made by PTFE and PHFP

Power transformer on-line monitoring on dissolved gas in oil is one of the effective and technical means to achieve the transformer state detection and fault diagnosis, and oil-gas permeability is one of the core technologies to implement transformer on-line monitoring. The traditional methods of oil-gas separation such as vacuum method and mechanical oscillation method were unable to satisfy the requirements of transformer on-line monitoring; and the methods which were used commonly in recent years, like dynamic headspace separation, corrugated tube, carrier gas elution etc, have a high rate of gas-separation and have already been used in some on-line monitoring products. However, the problems still exist: easy formation of oil pollution, so the oil can not be recycled and the device structure is relatively complex. This paper based on the separation principle of polymer membrane, proposes mixed hollow fiber membrane made by polytetrafluoroethylene (PTFE) and polyhexafluoropropylene (PHFP), and designs an oil-gas separation test platform formed by the storage tank, oil-gas permeability tank, temperature controller and gas chromatographic analyzer etc, does laboratory research on the oil-gas permeability of the mixed hollow fiber membrane at different temperatures. The results show that, the permeability of the mixed hollow fiber membrane is obviously better than the commonly used single fluoride film or rubber film, seven fault gases H2, CO, CO2, CH4, C2H6, C2H4, and C2H2 can be separated efficiently form transformer oil within 24 hours. More to the point, the equilibrium time is short, the gas permeability is high and the test platform structure is simple, all of these advantages provide a strong guarantee for the development of on-line monitoring technology on dissolved gas in transformer oil.

Effect of Temperature on Oil-Gas Separation in Membrane Separation Based Transformer On-Line Monitoring

In the same conditions, the transformer on-line monitoring and off-line chromatographic analysis should be consistent, but the actual on-line monitoring is effected by the ambient temperature to make it is different from the off-line chromatographic measurement. this paper analyzes the theory of oil-gas separation, and develops a gas-oil separation test platform first, conducts an experiment about the changes of temperature based on the device, and then compares with the data of off-line measurement, gets the law of temperature affection on the oil-gas separation process, Finally gives the reason of influence of ambient temperature on oil-gas separation in on-line monitoring.

Experimental Application of Leakage Flux to the Detection of Insulation Faults on Disc-Type Winding Transformers

This paper presents an experimental study carried out on a disc-type winding transformer. Although several industrial methods exist for the on-line and off-line monitoring of power transformers, all of them are expensive and complex, and require the use of specific electronic instrumentation. In this paper, an on-line analysis of transformer leakage flux is tested as an efficient alternative procedure for detecting insulating failures during their earliest stages. A power transformer was specifically manufactured for the study. A finite element model of the machine was designed to obtain the transient distribution of leakage flux lines in the machine’s transversal section under normal operating conditions and when shorted turns are intentionally produced. Very cheap, simple sensors, based on air core coils, were built in order to measure the leakage flux of the transformer, and non-destructive tests were also applied to the machine in order to analyse preand post-failure voltages induced in the coils. Results point to the ability to detect very early stages of failure. The asymmetry produced by the failure generates an indicator (induced EMF in the coils) that can be easily distinguished from the one obtained for the healthy machine. In fact, diagnosis can be perfectly achieved in spite of the variation of such an indicator with load.

"On-Line Monitoring of Power Transformers"

A microprocessor based Transformer Monitoring System (TMS) has been developed to provide the continuous on-line monitoring and analysis of power transformer operating parameters. With the TMS, changes in the operating condition of the transformer can be determined from a historic data base and potential problems can be identified prior to becoming major or catastrophic problems. The TMS, which is remotely located at the transformer site in a control cabinet, collects and analyzes all data every ten seconds. Each TMS is periodically polled by a Host Computer (HC) over a fiber optic data link and telephone lines operating at 1200 bps, full duplex. The HC is used to further analyze the data collected for potential problems and to update the historic data base for each transformer.

On-Line Monitoring of Power Transformers

On-Line Monitoring of Power Transformers