Experience with on-line insulation diagnostics of surge arresters by PD measurement in the field

2016 ◽  
Author(s):  
H. P. Amorim ◽  
A. T. D. Carvalho ◽  
T. B. Rodrigues ◽  
J. B. S. Borges ◽  
C. F. F. de C. Cunha
Keyword(s):  
Surge Arresters ◽  
On Line ◽  
Insulation Diagnostics

Simulation Study of the MOA Resistive Leakage Current Detection Method

2013 ◽  
Vol 655-657 ◽  
pp. 177-184
Author(s):  
Xian Bin Dai ◽  
Xiao Hua Yuan ◽  
Wen Yao Sun ◽  
Xin Liu
Keyword(s):  
Mathematical Model ◽  
Leakage Current ◽  
Detection Method ◽  
Detection Methods ◽  
Surge Arresters ◽  
Coupling Capacitor ◽  
On Line ◽  
Harmonic Voltage ◽  
The Impact ◽  
Current Detection

On-line monitoring of the insulating state of metal oxide surge arresters (MOA) is monitoring its resistive leakage current. This paper analyses the common detection methods of resistive current, pointed out the problems. According to the relationship among the grid voltage and the flow through the leakage current of MOA, the resistive and capacitive current, put forward a new resistive leakage current detection method, and established a mathematical model. Using this mathematical model, new detection method can be verified by simulation. Confirmed that the new method can effectively reduce the impact of the power grid of the third harmonic voltage and phase coupling capacitor, this create a precise measurement for MOA resistance current online testing.

Development and Experimental Evaluation of Leakage Current Measurement Sensor for Electrical Power Apparatus

2018 ◽  
Vol 19 (6) ◽  
Author(s):  
Mandava Mohana Rao ◽  
Mritunjay Kumar ◽  
Archana L
Keyword(s):  
Leakage Current ◽  
High Voltage ◽  
Electrical Power ◽  
Current Measurement ◽  
Design Parameters ◽  
Optimized Design ◽  
Design Development ◽  
Surge Arresters ◽  
On Line ◽  
Sensor Assembly

Abstract Leakage current measurement plays an important role in determining the healthiness of high voltage insulation of a power apparatus. High voltage (HV) insulation degrades due to electrical, thermal and mechanical ageing and their cumulative effects, and thus the leakage current of the insulation increase over a period of time. The accurate and real time measurement of leakage current enables the utilities to on-line access the healthiness of the insulation. This paper describes about the design, development, calibration and testing of a novel non-contact type passive leakage current sensor which can be used for monitoring of various electrical devices based on the analysis of the leakage current captured by the sensor. The developed sensor has been successfully used for measurement of leakage current in oil-filled HV bushings as well as in gas insulated surge arresters. The sensitivity of the developed sensor as per its design can be in the order of few milli amperes in case of bushing and in the order few micro amperes for surge arrester monitoring. The paper also reported a novel design of bushing adapter-sensor assembly for on-line measuring the leakage current in HV bushings without using the conventional capacitive or resistive tapping based measurements. Further, results covering experimental leakage current measurement on a 420 kV bushing using the developed adapter sensor assembly have also been presented. To establish capabilities of the developed sensor with optimized design parameters, laboratory measurements of leakage current on 420 kV and 145 kV GIS surge arresters have also been carried out and reported in the paper. Third harmonic content of surge arrester leakage current has also been estimated in-line with IEC requirement to assess the healthiness of the surge arrester. Finally, suitability of the developed sensor for leakage current measurement of above power apparatus equipment has also been analyzed and discussed.

The on-line use of histogram data for high-speed correction and alignment of electron microscope images

1984 ◽  
Vol 42 ◽  
pp. 556-557
Author(s):  
William Krakow
Keyword(s):  
Power Spectrum ◽  
High Speed ◽  
Direct Memory Access ◽  
Digital Television ◽  
Contrast Transfer Function ◽  
The Past ◽  
High Resolution Tem ◽  
On Line ◽  
Correction Of Astigmatism ◽  
The Fourier Transform

In the past few years on-line digital television frame store devices coupled to computers have been employed to attempt to measure the microscope parameters of defocus and astigmatism. The ultimate goal of such tasks is to fully adjust the operating parameters of the microscope and obtain an optimum image for viewing in terms of its information content. The initial approach to this problem, for high resolution TEM imaging, was to obtain the power spectrum from the Fourier transform of an image, find the contrast transfer function oscillation maxima, and subsequently correct the image. This technique requires a fast computer, a direct memory access device and even an array processor to accomplish these tasks on limited size arrays in a few seconds per image. It is not clear that the power spectrum could be used for more than defocus correction since the correction of astigmatism is a formidable problem of pattern recognition.

Image registration with a computer driven S.T.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 98-99
Author(s):  
A.M.H. Schepman ◽  
J.A.P. van der Voort ◽  
J.E. Mellema
Keyword(s):  
Spot Size ◽  
Scanning Transmission Electron Microscope ◽  
Small Computer ◽  
Structural Studies ◽  
Area Of Interest ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Specimen Area ◽  
On Line ◽  
Minimum Distances

A Scanning Transmission Electron Microscope (STEM) was coupled to a small computer. The system (see Fig. 1) has been built using a Philips EM400, equipped with a scanning attachment and a DEC PDP11/34 computer with 34K memory. The gun (Fig. 2) consists of a continuously renewed tip of radius 0.2 to 0.4 μm of a tungsten wire heated just below its melting point by a focussed laser beam (1). On-line operation procedures were developped aiming at the reduction of the amount of radiation of the specimen area of interest, while selecting the various imaging parameters and upon registration of the information content. Whereas the theoretical limiting spot size is 0.75 nm (2), routine resolution checks showed minimum distances in the order 1.2 to 1.5 nm between corresponding intensity maxima in successive scans. This value is sufficient for structural studies of regular biological material to test the performance of STEM over high resolution CTEM.

Design and calibration of an IVEM for general 3-dimensional imaging of non-diffracting materials

1992 ◽  
Vol 50 (2) ◽  
pp. 1040-1041
Author(s):  
Neil Rowlands ◽  
Jeff Price ◽  
Michael Kersker ◽  
Seichi Suzuki ◽  
Steve Young ◽  
...  
Keyword(s):  
3D Imaging ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3 Dimensional ◽  
3D Microstructure ◽  
Image Translation ◽  
Digital Correlation ◽  
On Line ◽  
Mechanical Stage ◽  
Projection Angle

Three-dimensional (3D) microstructure visualization on the electron microscope requires that the sample be tilted to different positions to collect a series of projections. This tilting should be performed rapidly for on-line stereo viewing and precisely for off-line tomographic reconstruction. Usually a projection series is collected using mechanical stage tilt alone. The stereo pairs must be viewed off-line and the 60 to 120 tomographic projections must be aligned with fiduciary markers or digital correlation methods. The delay in viewing stereo pairs and the alignment problems in tomographic reconstruction could be eliminated or improved by tilting the beam if such tilt could be accomplished without image translation.A microscope capable of beam tilt with simultaneous image shift to eliminate tilt-induced translation has been investigated for 3D imaging of thick (1 μm) biologic specimens. By tilting the beam above and through the specimen and bringing it back below the specimen, a brightfield image with a projection angle corresponding to the beam tilt angle can be recorded (Fig. 1a).

Software pattern recognition applied to nanodiffraction patterns from a STEM instrument

1986 ◽  
Vol 44 ◽  
pp. 694-695
Author(s):  
G.Y. Fan ◽  
J.M. Cowley
Keyword(s):  
Image Processing ◽  
Pattern Recognition ◽  
Computer Software ◽  
Processing System ◽  
Light Level ◽  
Host Computer ◽  
Low Light ◽  
Image Processing System ◽  
Recent Developments ◽  
On Line

In recent developments, the ASU HB5 has been modified so that the timing, positioning, and scanning of the finely focused electron probe can be entirely controlled by a host computer. This made the asynchronized handshake possible between the HB5 STEM and the image processing system which consists of host computer (PDP 11/34), DeAnza image processor (IP 5000) which is interfaced with a low-light level TV camera, array processor (AP 400) and various peripheral devices. This greatly facilitates the pattern recognition technique initiated by Monosmith and Cowley. Software called NANHB5 is under development which, instead of employing a set of photo-diodes to detect strong spots on a TV screen, uses various software techniques including on-line fast Fourier transform (FFT) to recognize patterns of greater complexity, taking advantage of the sophistication of our image processing system and the flexibility of computer software.

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