Li Ruihai

A new method to remove the aging RTV coatings on glass insulators

RTV coatings had been widely used in electric insulators to prevent pollution flashover performance at external insulation. For the bad weatherability of polymers, RTV coatings will be aging during the long serve time. To remove the aging coatings, many methods had been used, such as solvent dissolve, high pressure water flushing, and dry ice flushing. But it is not easy for these methods to remove the coatings entirely and easily. In this paper we described a new method-laser cleaning, which is a very easy and useful method. We used the continuous laser with Ytterbium Laser System (YLS-2000) and the pulsed laser with IPG fiber laser system (Nd:YAG) in the experiment. Different scanning speed of the laser irradiating and different energy density had been tested to find Optimization parameters which could remove the coatings and not damage the surface of the glass insulators. The both laser irradiating can remove the coatings clearly in the experiment. But the continuous laser will leave the carbon clusters on the surface, which is easy to remove but bad for the insulators. The scanning speed can be higher than 10 mm/s that means the glass insulators with 20mm diameter can be dealt in 3 minutes with pulsed laser. The laser cleaning is a good method to remove the RTV coatings on the glass insulator surfaces up and down. With the cost of laser technology decreases, it will be a better method as a coating removing method.

Characterization of acoustic signal produced by partial discharge in insulation oil

Insulation failure is one of the major causes of catastrophic failure of high voltage apparatus. It is important for the study of partial discharge behavior in electrical apparatus to know the degration of insulating materials. This paper focuses on the analysis of acoustic signal produced by partial discharge in insulation oil. The needle-plane electrode system is assembled to simulate the partial discharge in insulation oil. Wavelet transform is used to analyze acoustic signal. The energy distribution of each level and time domain waveform is analyzed. A low-noise amplifier and a de-coupler are used to detect the acoustic signal with high-sensitivity. A digital acquire card is used to get the acoustic signal and save data in computer.