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Volume 153
Issue 2
IEE Proceedings - Science, Measurement and Technology
Volume 153, Issue 2, March 2006
Volumes & issues:
Volume 153, Issue 2
March 2006
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- Author(s): G.P. Cleary and M.D. Judd
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 153, Issue 2, p. 47 –54
- DOI: 10.1049/ip-smt:20050103
- Type: Article
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Investigations are reported into a range of defects causing partial discharge (PD) activity in high-voltage oil-insulated equipment. The aim is to explore the relationship between radiated ultra-high frequency (UHF) signals and electric charge in a PD current pulse for PD sources in oil insulation. Experiments are performed under high-voltage AC conditions using electrode configurations that included a sharp protrusion, a bad contact, and a free metallic particle. A broadband current transformer is used to measure the PD current pulses with the UHF signals being detected using a pair of sensors mounted inside a metal tank surrounding the PD sources. Current pulses and UHF signals were recorded simultaneously using an oscilloscope with a bandwidth of 3 GHz. The level of correlation between the energy of the radiated UHF signals and the charge content of PD pulses is shown to vary depending on the defect type. Polarity-dependent UHF spectral content and ratio of UHF signal energies measured at the two sensors are shown to exhibit characteristics dependent on the discharge behaviour. These results and the analysis procedures introduced will contribute to the development of effective UHF monitoring systems for oil-insulated high-voltage plant. - Author(s): J. Jin ; C.S. Chang ; C. Chang ; T. Hoshino ; M. Hanai ; N. Kobayashi
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 153, Issue 2, p. 55 –63
- DOI: 10.1049/ip-smt:20045036
- Type: Article
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To ensure the safe and reliable operation of a gas-insulated substation (GIS), it is crucial to quickly identify partial discharge (PD) sources to prevent the occurrance of breakdowns. A method based on wavelet packet transform techniques is developed to meet this requirement. The proposed method extracts is able to extract features from ultra-high frequency resonance signals measured from a test GIS section. These features are subsequently used to train a neural network that is then able to quickly and reliably diagnose PD events. A quality-assurance scheme is developed that ensures the robustness of the PD classification to changes in the background noise level and the location of the PD event within the test GIS section. - Author(s): G. Antonini and G. Ferri
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 153, Issue 2, p. 64 –72
- DOI: 10.1049/ip-smt:20050077
- Type: Article
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A ladder network (LN)-based model for the determination of the delay in coupled interconnects is proposed. The determination of the electrical characteristics of the LN in terms of internal electrical parameters and number of cells allows the estimation, in an approximated but very accurate way, at the time delay for RLC-terminated interconnections. The rational representation of the interconnect allowed by the use of a half-T LN leads to a reduced-order macromodel of the interconnect which is suitable for time delay estimation. Numerical examples confirm the robustness and accuracy of the proposed method which is also suitable for multiconductor transmission lines with both frequency-independent and frequency-dependent per-unit-length parameters. - Author(s): C.J. Carpenter
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 153, Issue 2, p. 73 –80
- DOI: 10.1049/ip-smt:20045008
- Type: Article
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The direction of the magnetic forces on currents, at right-angles to the conductor, leads to an apparent failure of the action-reaction force balance when applied to the component parts of a current-carrying circuit. The electromagnetic railgun provides an example showing the need for a force in the direction of current flow. These and other applications continue a long-standing debate, originating in Ampère's analysis of the nature of the forces on current elements. The paper examines the consequences of Maxwell's ‘dynamical’ approach to currents in terms of ‘electrical fluids’. The conductor surfaces transfer the transverse force on the conduction electrons to the crystal lattice but, since there are no similar constraints in the axial direction, a current element cannot be treated as a single entitity. The implications of the separation into two groups of charge are examined. It is shown that the hydraulic fluid, or ‘hosepipe’, analogue provides a useful insight in terms of momentum and pressure. The corresponding electromagnetic properties provide a ‘dynamical’ alternative to the magnetostatic Maxwell stresses in the field. This also accounts for the reaction in a self-consistent way, but requires such high levels of energy and stress in empty space as to be widely regarded as ‘unreal’. - Author(s): J.E. Jones
- Source: IEE Proceedings - Science, Measurement and Technology, Volume 153, Issue 2, p. 81 –92
- DOI: 10.1049/ip-smt:20045046
- Type: Article
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A full mathematical description of the complex interaction of adjacent point–plane coronae has yet to be given. An essential feature of the phenomenon is the electric field on the planar line running directly below the points. Experimental data, obtained elsewhere, have been manipulated to reveal the functional dependence of this field on the control or independent variables of voltage and geometry. A model in terms of simple functions has then been derived that fits the measurements within reasonable bounds and which is a valuable tool from the point of view of predictive engineering. As for single points, the behaviour is shown to be separable, with a linear dependence on the voltage and an inverse dependence on the gap separation. The distribution is further shown to be represented by cosine power functions of the angles subtended from each planar position to the electrode points and to locations on the central axis between the points. The modelling uses centre-of-charge concepts, and gives an insight to the mutual interactions of the multipoint discharges that are used commercially and also into the behaviour of neighbouring coronas on high-voltage equipment in the environment. What is known of single-point phenomena leads one to expect that the description derived here is likely to hold for a large range of gap sizes and also for positive DC discharges in the absence of streamers.
UHF and current pulse measurements of partial discharge activity in mineral oil
Classification of partial discharge events in gas-insulated substations using wavelet packet transform and neural network approaches
Ladder-network-based model for delay determination in coupled interconnects
Action-reaction forces between current-carrying conductors
On the interaction of adjacent coronae: a description of the electric field behaviour on the planar line beneath twin coronating negative DC points in air
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