Detection of partial discharge (PD) signals is one of the most important methods for predictive maintenance of gas insulated switchgears (GIS). Because type of PD source, configuration of a GIS tank and frequency response of a sensor influence a PD spectrum, detected PD pulse has a specified frequency spectrum. Although frequency spectrum is one of valuable information for PD in a GIS, the spectrum measured with spectrum analyzer or FFT processing is generally a result of averaging of many signals so that statistical features of PD are lost. In addition, frequency spectrum is complex and special experience is needed to recognize it. Thus convenient method is required to discriminate various PD pulses. In this paper, we attempt to extract two frequency components from a PD pulse and to process them in order to categorize it easily. Correlation between pulse heights of two frequency components and pulse height distribution resolved with power voltage phase are shown as effective methods to distinguish the type and the location of PD sources.
Wafer charging during Ion Implantation was studied using two measurement methods: (1) the capacitive probe measurement of the surface potential on the Si wafer covered with 1 /spl mu/m thick photoresist and (2) the C-V (capacitance-voltage) measurement to evaluate the degradation of the thin oxide of MOS structure fabricated on the wafer. The wafers loaded on rotating disc were implanted with 35keV As+ at the beam currents of 1 to 10mA. The probe measurement showed that the charge-up phenomenon was to a large extent governed by the behavior of the secondary electrons. From the C-V measurement, the effects of ion beam density and of the photoresist coverage were discussed. It was shown that the four charge sources contributed to the degradation of the oxides: the irradiated ions, the secondary electrons emitted from a gate electrode, the charges accumulated on the photoresist around the gate electrode and the secondary electrons emitted from the disc.
Agglomerates of nanoparticles which inevitably occur in the fabrication process of epoxy nanocomposite can affect the insulation properties of epoxy nanocomposite. This paper presents an attempt to clarify the effect of agglomerate size on two important insulation properties of epoxy/TiO 2 nanocomposite (NC). One is intrinsic AC breakdown strength and the other is long-term partial discharge lifetime. We used a centrifugation technique to control the maximum size of the agglomerates in the range from 5 μm down to 0.05 μm in each sample. As the results, AC intrinsic breakdown strength was increased with decreasing the maximum agglomerate size and became even higher than the neat epoxy resin when the maximum size is less than around 0.05um. On the other hand, partial discharge lifetime decreased with decreasing the maximum agglomerate size. It should be noted that the PD lifetime distinctively decreased when the agglomerate size is less than around 0.2 um indicating the existence of a critical agglomerate size which contribute to the suppression of partial discharge development resulting in the extension of the partial discharge lifetime.
The assessment of the dielectric behavior of thin Polyimide films submitted to high DC stress is investigated considering different characterization methods. Materials of interest are polyimide films of 11 to 16 μm in thickness deposited by spin coating on a silicon wafer. Comparison is made with structures with a thin SiO 2 layer onto the substrate. The laser intensity modulation method appears suited to probe space charges in the films investigated therein. These measurements show that the presence of a SiO 2 layer strongly limits the electrons injection.
Epoxy nanocomposites (NCs) are known to have advantages when used in the electrical insulation of power equipment. Agglomerates of nanoparticles, which inevitably form during the fabrication process, can affect the insulating properties of the resultant nanocomposites. Our previous research has clarified that the impulse breakdown strength of the solid part, rather than the surface, of epoxy-TiO 2 NCs with agglomerates removed was higher than that of unfilled epoxy resin. Here, we investigated the dependence of the TiO 2 filler volume fraction on the AC breakdown strength of NCs whose agglomerate size was controlled. The volume fraction and the maximum agglomerate size were controlled using a simple dilution procedure and a centrifugation technique. The AC breakdown strength of the NCs was found to increase with decreasing volume fraction of TiO 2 nanoparticles when the maximum agglomerate size was controlled at the same level. The variation of the AC breakdown strength of the NCs decreased with decreasing maximum agglomerate size, suggesting that the existence of agglomerates larger than a critical size could affect the breakdown.
The diagnosis algorithm using ultra high frequency (UHF) method with the higher-order electromagnetic wave (EM-wave) was examined as the advanced partial discharge (PD) diagnosis method in a gas insulated switchgear (GIS) in the former paper. Previous studies evaluated the characteristics of EM-waves propagated in a simple coaxial cylindrical pipe, or through an L-shaped or a T-shaped pipe formed by combining these. In the present study, components (a hand hole, a post-type spacer, etc.) present in an actual GIS structure were identified, and an evaluation done mainly through an analysis on what effects their presence has on the mode transformation of EM-waves propagated inside a GIS tank. The direction in which a GIS tank is bent is horizontal (0deg) in the L-shape structure. If there is either a post-type spacer or a shield ring inside, and the signal source is in the 0deg direction, the distribution of the EM-wave strength varied according to through the L-shape structure. Also in the case of a T-shaped structure, the distribution of the output after signals are transmitted through the T-shaped junction varied depending on each component. Based on these characteristics, the diagnosis algorithm for PD with higher-order mode EM-waves was improved taking into account the effects of various components existing in an actual GIS, and a PD diagnosis method more suitable for an actual structure was established.
Direct probing of space charge was carried out on high-density polyethylene doped with antistatic agent using a thermal pulse method. Prominent positive space charge was found to be formed near the cathode by voltage application. The field at the cathode is enhanced by the space charge. The conduction can be quantitatively explained by Schottky-type electron injection under the enhanced cathode field. The anomalous discharge current after short-circuiting, which flows in the same direction as the charging current, can also be explained by the continued electron injection due to the remaining positive space charge.
Numerical simulation of electromagnetic fields was performed to investigate the transmission and reflection characteristics of spacers, L-shaped sections of a GIS bus structure. The resonance frequencies of a cavity between spacers agreed roughly with experiment. The modes of electromagnetic wave are shown to transform to different modes, e.g., from TE11 to TE21 mode, after transmission and reflection through L-shaped sections of a GIS structure.
Germanium is typically used in ultra-shallow junction formation as an amorphization implant to reduce channeling in subsequent low energy boron dopant implants. Several equipment and process considerations can be associated with germanium operation. For example, source life may be adversely affected due to the cycling of refractory metal fluorides from materials used in the arc chamber, and cross-contamination, especially implanted As, may occur on machines that run multiple species. Tool productivity also depends on beam current and beam setup time due to the relatively high doses and low energies required. A number of design and operational improvements have been implemented on the GSDIII/LED and Ultra to address these concerns. Hardware and tuning algorithms for germanium operation are described. Data showing improved source lifetime and low species cross-contamination are presented Strategies for achieving productivity, flexibility, and cycle time improvements, including mixed species operation and germanium-boron chaining, are discussed.
