A Hilbert fractal antenna and portable monitoring system for partial discharge detection in gas insulated substations

We design a third Hilbert fractal antenna for partial discharge (PD) monitoring in gas insulated substations (GIS) based on fractal principles, and analyze the Hilbert antenna impedance characteristics using an equivalent inductance method of parallel transmission lines. The PD experiment of metal protrusion defect is conducted employing fractal and microstrip antennae. The test results show that the characteristic of the Hilbert fractal antenna has good performance and can detect the PD signal for online monitoring in GIS. A portable online monitoring and locating system for GIS is established using the Hilbert fractal antenna and LabVIEW. The locating accuracy of the PD source in the laboratory meets the requirements of the PD site location.     

Suppression of Periodic Narrowband Interferences in Cable Partial Discharge Detections

There are background noises and interferences in the signal acquired,due to partial discharge(PD) detection system covers a broad frequency band.To suppress periodic narrowband signal which is a quite serious interference in PD measurement,the existing suppression method is introduced,the new method of wavelet packet transform is mainly studied to de-noise the periodic narrowband in XLPE cable PD detection system,which is based on the db4 basic wavelet using soft threshold.The results of the experiment show that wavelet packet transform is effective in restraining the periodic narrowband interferences to extract the PD pulses in XLPE cable PD monitoring system.     

Application of GC FTIR technology in the analysis of SF6 decomposition products

The composition of SF6 decomposition products is directly associated with the safe operation of equipment. Through GC FTIR coupling technique,the SF6 decomposition products are divided, the qualitative analysis is made with FTIR to the outlier,and spectrogram was processed with subtract and searched the analogous one. Above data is used to generate the tridimensional atlas of infrared spectrum absorbance GC holding time. Single gas analysis is compared with local measurement, the foregoing method can make the qualitative analysis and quantitative analysis for the decomposition products, the fault features detected by gas composition and chroma is anastomotic with the actual fault, the result indicates that this method can be used in GIS fault diagnosis.     

New Monitoring and Assessment Method for the Joints of Steel and Concrete Connection in Large span Bridge

The joints of steel and concrete (JSC) is the key substructure to composite bridge, the method of condition monitoring and safety assessment were carried out for JSC with perfobond shear connectors (PBL) and local prestressed tendon in large span bridge. According to the damage mechanism of JSC, new monitoring parameters were proposed. The sensor location layout and the assessment thresholds of PBL were addressed with the consideration of the disadvantage influences of environment, load and concrete creep to local prestressed loss assessment and validated by the static load experiment. Compared the experimental results with field monitoring data, it was found that the new monitoring parameters and new assessment method were feasible and can be used as reference to the same type connectors in large span bridges.     

Thermogravimetry analysis and kinetic characteristics of pulverized coal in O2/CO2 atmosphere

This study conducts non isothermal combustion experiments of three types of pulverized coal by Synthesized Thermogravimetry Analyzer in O2/N2 and O2/CO2 atmospheres. It analyzes the changes of combustion characteristic parameters of pulverized coals in different atmospheres and calculated the kinetic parameters at each condition. The results show that combustion characteristics under O2/CO2 atmosphere are different from those under O2/N2 atmosphere at the same O2 concentration. When N2 is replaced by CO2, both ignition time and burnout time of pulverized coals increase, burnout temperature is higher, and combustion characteristic index declines. DTG curves of coal combustion move to low temperature zones when O2 concentration in O2/CO2 mixture increases. It indicates that both ignition and burnout temperature are lower, burnout time decreases, combustion characteristic index obviously increases, and combustion performance of pulverized coals are improved. Activation energy, frequency factor and reaction order at low temperature stage are lower than those at high temperature stage. Kinetic compensation relationship exists between combustion activation energy and frequency factor in different atmospheres.