There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

A review on machinery diagnostics and prognostics implementing condition-based maintenance

Partial discharges (PD) generate wideband radio frequency interference and, consequently, can be detected using radio receiving equipment. Due to the advances in ultra-high-speed sampling equipment, it is possible to accurately measure the propagation of the PD wavefront as it passes through a 4 element antenna array. From these measurements, the three-dimensional position of the PD source can be calculated using an iterative algorithm. The locating equipment is suitable for use within the vicinity of energized high-voltage plant and can locate sources up to 15 m from the array. Results are presented showing the location ability of the equipment under laboratory and field conditions. A significant advantage is the ability to detect PD sources in energized plant without the need for outages or electrical connections.

Radiometric location of partial discharge sources on energized high-Voltage plant

Note: Includes index + new features guide (1995) + quick reference Reference Record created on 2004-09-07, modified on 2016-08-08

Signal processing toolbox for use with MATLAB : ユーザーズガイド

The subject matter of this paper refers to the improvement of the acoustic emission (AE) method when used for detection, measurement and location of partial discharges (PDs) in oil insulation systems of power appliances. The detailed subject matter refers to the issues connected with the application of modern methods of digital processing of signals obtained during technical high-power measurements. The paper presents the results of measurements and analyses of the AE pulses generated in setups making the modeling of basic PD forms that can occur in oil insulations possible. The research concentrated mainly on the following types of PDs: point-plane, multipoint-plane, multipoint-plane with a layer of pressboard, surface, generated in gas bubbles and on the indeterminate-potential particles moving in oil. In each case, the acoustic pulses generated by PDs in both positive and negative half times of the voltage supplying the spark gaps under study were analyzed. The AE pulses measured were subject to the wavelet analysis. For each of the PD forms the continuous wavelet transform (CWT) was determined and the corresponding time-frequency distributions were drawn. Moreover, for the AE pulses generated by PDs of the surface and multipoint-plane types, the discrete wavelet transform (DWT) was calculated, the runs of the particular details for six frequency levels and the approximation run were presented. In reference to the DWT analysis for the particular details, the probability density functions (PDF) and the autocorrelation functions (ACF) were determined at the particular levels of decomposition. Also columnar diagrams showing the energy value that is transferred at the particular levels of decomposition were presented. Moreover, the energy density spectrum runs determined through a FFT were presented for comparison. The Morlet wavelet was used to determine the CWT, and the symlet wavelet was used to calculate the DWT. Next, the distributions obtained for the particular PD forms underwent a comparative analysis taking into account the voltage polarization. It was observed that different frequency structures occur for the particular PD forms. Also, a different time of coherent structure duration for the particular PD forms was observed.

Application of wavelet analysis to acoustic emission pulses generated by partial discharges

Recently, diagnostic techniques have been investigated to detect a partial discharge (PD) associated with a dielectric material defect in a high-voltage electrical apparatus. Gas insulated switchgear (GIS) is an important equipment in a substation, it is highly desirable to measure a partial discharge (PD) occurring in GIS which is a symptom of an insulation breakdown. As it is important to develop a noncontact method for detecting the insulation fault, this paper proposes a new method to detect the wide-band electromagnetic (E-M) wave emitted from PD using the Wavelet transform. The Wavelet transform provides a direct quantitative measure of spectral content, "dynamic spectrum", in the time-frequency domain. This paper experimentally shows the "dynamic spectrum" of the wide-band E-M wave emitted from PD in the time-frequency domain. This method is shown to be useful for detecting the symptom of the insulation breakdown occurring in GIS.

/pdf/detection-of-wide-band-e-m-signals-emitted-from-partial-3w2g8p3com.pdf

Detection of wide-band E-M signals emitted from partial discharge occurring in GIS using wavelet transform

The electromagnetic waves emitted from partial discharge (PD) due to material defects in high-voltage lectric power apparatus and facilities are broadband signals including VHF, UHF (Very High Frequency, Ultra High Frequency). A VHF-UHF radio interferometer system (VURIS) for locating PD source has been originally designed, constructed and tested. The system is based on the idea extracting the phase differences at different frequencies between a pair of the received signals by the Fourier transform and computing the direction of the electromagnetic waves emitted from PD source. It can be small-sized, more suitable for compact and portable system, because UHF half-wavelength dipole antennas are used to receive the electromagnetic waves and the baseline between the antennas is very short. And it requires fewer antennas to achieve equivalent angular resolution than a narrow band interferometer system, which requires multiple baselines corresponding to a few times of half-wavelength of the observation frequency. Therefore, it's able to reduce the operating time at the measurement site because it's not needed to arrange many antennas at the many points. The indoor test results indicate that the system is able to estimate the arrival angle of the electromagnetic waves emitted from PD source.

Fundamental Study on Locating Partial Discharge Source using VHF-UHF Radio Interferometer System

Non-Contact Detection of Electromagnetic Noise Occurrence due to Partial Discharges by Spatial Phase Difference Method

The electromagnetic (E-M) waves emitted from partial discharge (PD) generated by material defects in high-voltage electric power apparatus and facilities are broadband signals including VHF/UHF components. In this paper, the author proposes an ultra wide band VHF/UHF radio interferometer system (UWB-VURIS) for detecting PD source, which has been originally designed, constructed and tested. The system is based on the idea extracting the phase differences at different frequencies between a pair of the received E-M signals by the fast Fourier transform (FFT) and computing the arrival angle of the E-M waves emitted from PD source. It can be small-sized, more suitable for compact and portable systems. It is able to reduce the operating time at the measurement site because it is not needed to arrange many antennas at the many points. The indoor test results indicate that the UWB-VURIS is able to estimate the arrival angle of the E-M waves emitted from PD source.

http://ieeexplore.ieee.org/iel5/7733/21229/00985270.pdf

Ultra wide band VHF/UHF radio interferometer system for detecting partial discharge source

In this paper, the finite difference time domain (FDTD) method is used to simulate the propagation of electromagnetic (EM) waves emitted from partial discharge (PD) occurred on distribution line. The simulation model is composed of the distribution line, a building, the ground, and four antennas mounted on a vehicle. Three pairs of time difference of arrival (TDOA) among antennas are used to locate PD position in three dimensions. The TDOAs are obtained by using standard cross-correlation (SCC) method. The superimposed positioning optimization on the time delay of arrival (SPOT) method is used to improve the location result.

Masatake Kawada

Papers

Detection of wide-band E-M signals emitted from partial discharge occurring in GIS using wavelet transform

Fundamental Study on Locating Partial Discharge Source using VHF-UHF Radio Interferometer System

Non-Contact Detection of Electromagnetic Noise Occurrence due to Partial Discharges by Spatial Phase Difference Method

Ultra wide band VHF/UHF radio interferometer system for detecting partial discharge source

Locating Partial Discharge Source Occurring on Distribution Line by Using FDTD and TDOA Methods