测量冲击电压的电容电流法

本文介绍了一种利用宽频带电流互感器将电容电流变换成电压信号,然后再积分得到一个正比于冲击高压的低压信号来测量冲击电压的方法,还讨论了各个组成部分的选取原则,并给出了全波及截波下的比对测量结果。     

Artificial neural networks for recognition of 3-d partial dischargepatterns

Partial discharge (PD) measurements have been carried out over the years to assess insulation systems in power apparatus for their integrity and design deficiencies. Digital PD recording, processing and its presentation as 3-d patterns are recent trends in both industry and testing laboratories. Interpretation of these patterns can lead to evaluation of the cause of PD. A need arises to look for methods in the domain of pattern recognition for automating this process. In this context, this paper presents results to demonstrate the possibility of using pattern recognition capabilities offered by a multilayer neural network to recognize 3-d PD patterns     

The use of fractal features for recognition of 3-D dischargepatterns

This work presents further results on the use of fractal features for recognition of 3-D partial discharge patterns. Two fractal features, the fractal dimension and lacunarity were calculated from 3-D discharge patterns and their power to discriminate among various discharge patterns was analyzed. The results indicate that fractal features possess fairly reasonable discriminating abilities     

Effective grounding mesh calculation technique

Efficient potential calculation techniques for the grounding mesh analysis are proposed. Proposals are presented for: an easy treatment of the image currents that appear in the single-layer and two-layer earth; an efficient series image summation technique; and the approximation technique of a rectangular conductor by means of an equivalent cylindrical rod. The validity of a conventional approximation in which the rectangular conductors have been replaced by cylindrical conductors of equal-cross-section areas is examined and shown to be acceptable     

Inhomogeneous field breakdown in GIS-the prediction of breakdownprobabilities and voltages. II. Ion density and statistical timelag

For pt.I see ibid., vol.3, no.3, p.923-30 (1988). An improved model for the calculation of statistical time lags in SF₆ insulated electrode arrangements for positive impulse voltage is presented. On the basis of physical considerations, the production rate of initial electrons is ascribed to the local density of negative SF₆ ions and to field dependent electron detachment. Values of negative ion densities are measured directly, while the detachment coefficient is determined by a fitting procedure to measurements of statistical time lags     

Dielectric spectroscopy in time and frequency domain for HV power equipment. I. Theoretical considerations

Most dangerous breakdowns are caused by the aging effects of HV insulation systems used within HV components, and there is still a lack of appropriate tools to diagnose such systems non-destructively and reliably in the field. This review introduces the theoretical background of dielectric spectroscopy in the time and frequency domains and provides an overview about the specific measuring methods based on this background. The specific methods treated are used for diagnosing electric insulation materials used in power engineering. It indicates that some of these methods may not be sufficient to gain full information about the actual conditions of a test object and that either measurements of polarization and depolarization currents (PDC in the time domain or measurements of C-tan/spl delta/ values (or complex permittivity) in the frequency domain (FDS) should be preferred to obtain a "dielectric response function" which offers much more information to judge the actual state of an insulation material or system.     

Applications of dielectric spectroscopy in time and frequency domain for HV power equipment

Dielectric spectroscopy in the time or frequency domain offers new opportunities for an off-line, on-site insulation condition assessment of HV electric power equipment and its predictive maintenance.     

Inhomogeneous field breakdown in GIS-the prediction of breakdownprobabilities and voltages. I. Overview of a theory for inhomogeneousfield breakdown in SF6

Inhomogeneous field breakdown in SF₆ has been investigated, and a theory has been developed which predicts the breakdown voltage for fast-rising (rectangular) waveforms applied to arbitrary electrode geometries and gas pressures. This theory facilitates the analytical design aspects of many GIS components where previously, engineering judgement and development testing were necessary. It is suggested that extensions of the theory, will permit breakdown voltage prediction for an arbitrary surge waveform, which will facilitate the assessment of test waveform efficacy and the development of a more reliable field, factory, and type tests     

Inhomogeneous field breakdown in GIS-the prediction of breakdownprobabilities and voltages. III. Discharge development in SF6and computer model of breakdown

For pt.II see ibid., vol.3, no.3, p.931-8 (1988). Extensive investigations into various phases of discharge development in SF₆ (corona formation, streamer to leader transmission, leader, and propagation) are summarized, with the goal of familiarizing the engineer with the theoretical and empirical basis of a quantitative model SF₆ breakdown, including breakdown in highly inhomogeneous fields. The quantitative predictive capability of this model is tested for a number of examples, which demonstrate the correct prediction of geometry and pressure dependencies of the breakdown voltage. Combined with the modified volume-time `law', the breakdown model becomes a valuable tool for the power engineer, capable of predicting statistical breakdown characteristics for a wide range of gap geometries and positive voltage waveforms as a function of pressure. The model does not cover negative polarity waveforms and becomes increasingly inaccurate as the waveform risetime increases over about 10 μs. Future research planned to address both of these limitations and practical applications are outline