Partial discharges in HV machines; initial considerations for a PD specification

Wood, J.W.; Sedding, H.G.; Hogg, W.K.; Kemp, I.J.; Zhu, Heng

doi:10.1049/ip-a-3.1993.0064

Cited by 25 publications

(12 citation statements)

References 5 publications

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“…Further activity is directed towards the definition of the Performance Fingerprint, which could be improved by adding new performance parameters, such as the Mean Square Error (mse), or by giving different weights to those already defined. Last but not least, great effort will be dedicated to the exploitation of the wide potentialities of wavelets in PD measurements as for in the case of Partial Discharges in winding systems [25] which could be studied and identified with the help of a multiconductor transmission line model [26,27] in conjunction with the Wavelet Transform.…”

Section: Resultsmentioning

confidence: 99%

An Improved Methodological Approach for Denoising of Partial Discharge Data by the Wavelet Transform

Petrarca¹,

Lupo²

2014

PIER B

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Abstract-Partial Discharge (PD) measurements may be affected by external noise and disturbances of various natures such as interference from broadcasting stations, stochastic noise, pulses from power electronics, etc. Extracting PD pulses from such a noisy environment is therefore a crucial issue. This paper presents a wavelet based technique for automatic noise rejection. The core of the paper is the use of an improved methodological approach for the selection of a suitable wavelet, which aims at summing up the benefits and overcoming some limitations of previous techniques. Firstly, a very wide set of training signals is used for the identification of the decomposition level and for the calculation of suitable performance parameters that identify each wavelet; then a Performance Fingerprint is introduced in order to summarize the ability of a specific wavelet to reconstruct a partial discharge waveform, and a distance criterion is used for the selection of the most suitable wavelet. Afterwards, useful information is collected for the reconstruction of the PD signal, and finally, results on the application of the algorithm for a set of numerical and experimental signals are presented.

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Section: Resultsmentioning

confidence: 99%

An Improved Methodological Approach for Denoising of Partial Discharge Data by the Wavelet Transform

Petrarca¹,

Lupo²

2014

PIER B

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“…The results obtained on a 500 MW turbine generator model showed that capacitive and inductive coupling in the end-winding were weak, the winding acted as a low-pass filter [37]. Meanwhile, a number of resonance frequencies between 40 MHz and 100 MHz were observed, which might shift lower when the PD pulse was deeper in the stator winding [37]. Differing from that, experiments conducted by Li et al [38] showed obvious coupling between bars in the same slot or end-windings of adjacent slots.…”

Section: Cross-couplingmentioning

confidence: 99%

“…Differing from that, experiments conducted by Li et al [38] showed obvious coupling between bars in the same slot or end-windings of adjacent slots. It should be noted that the frequency ranges exploited by Wood et al [37] and Li et al [38] are 35 kHz~250 kHz and 0~5 MHz, respectively. Thus the above results cannot accurately reflect the frequency characteristics of wide-band PD signals when propagating in stator windings.…”

Section: Cross-couplingmentioning

confidence: 99%

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A Review of Online Partial Discharge Measurement of Large Generators

Luo

Wang³

2017

Energies

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Abstract:Online partial discharge (PD) measurements have long been used as an effective means to assess the condition of the stator windings of large generators. An increase in the use of PD online measurement systems during the last decade is evident. Improvements in the detection capabilities are partly the reason for the increased popularity. Another reason has been the development of digital signal processing techniques. In addition, rapid progress is being made in automated single PD source classification. However, there are still some factors hindering wider application of the system, such as the complex PD mechanism and PD pulse propagation in stator windings, the presence of detrimental noise and disturbances on-site, and multiple PD sources occurring simultaneously. To avoid repetition of past work and to provide an overview for fresh researchers in this area, this paper presents a comprehensive survey of the state-of-the-art knowledge on PD mechanism, PD pulse propagation in stator windings, PD signal detection methods and signal processing techniques. Areas for further research are also presented.

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“…Naturally, one expects that a criterion of an absolute PD magnitude exists for evaluating stator winding insulation condition. Unfortunately, unlike many other types of high-voltage equipment (such as cables), a criterion for acceptable PD levels does not exist for rotating machines due to PD calibration problems [2,3].This article analyzes why one cannot rely on an absolute PD magnitude to assess the insulation condition of rotating machines. How to identify stator insulation deterioration effectively and reliably will be discussed and demonstrated by case studies.…”

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confidence: 99%

Identification of stator insulation deterioration using on-line partial discharge testing

Zhu¹,

Green²,

Šašić³

2001

IEEE Electr. Insul. Mag.

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O n-line partial discharge (PD) testing has been used to provide useful information to diagnose and monitor the integrity of stator winding insulation of large generators and motors for half a century [1]. However, questions remain on how to assess stator insulation problems using PD test data. Many users still ask the question, "How do I know if my machine has a problem?" Does a rotating machine with higher PD readings fail more quickly than one with lower PD readings? Can one use an absolute PD magnitude to turn on a red light for stator insulation deterioration? These questions are critical to successful use of on-line PD testing technology.What is a warning sign for severe stator insulation deterioration? Naturally, one expects that a criterion of an absolute PD magnitude exists for evaluating stator winding insulation condition. Unfortunately, unlike many other types of high-voltage equipment (such as cables), a criterion for acceptable PD levels does not exist for rotating machines due to PD calibration problems [2,3].This article analyzes why one cannot rely on an absolute PD magnitude to assess the insulation condition of rotating machines. How to identify stator insulation deterioration effectively and reliably will be discussed and demonstrated by case studies. The paper concludes that trending of PD activity is the reliable way to identify severe insulation deterioration in rotating machines. What Influences Assessment of Stator Insulation Condition Based Upon PD Magnitudes?There are various types of on-line PD testing systems available. Common types of PD data presentation are pulse height analysis graphs, phase resolved graphs, normalized quantity numbers (NQNs), polar graphs, etc. However, there are difficulties in setting an alarm for severe stator insulation deterioration based upon the data presentation. The difficulties are caused by the following factors: l PD calibration problems in rotating machines; l PD location and PD pulse propagation; l PD detector; l PD type; l Differences among machines and among PD measurements. PD Calibration Problems in Rotating MachinesA PD test specification for rotating machines has not been established, although such specifications exist for other high-voltage equipment. The reason for this is the lack of an effective calibration technique for PD measurement in rotating machines. The conventional PD calibration approach, as stated in IEC 270 and ASTM D1868, is to inject a pulse with a known amount of charge into the machine terminal and to determine the magnitude of the response produced by the PD measurement system. The calibration pulse with a voltage V is injected into the winding via a calibration capacitor C. The injected charge is Q = CV. Then, a scale relationship between the injected charge Q and readings of the PD measurement system can be established.The conventional PD calibration method is not applicable to rotating machines, since:

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Partial discharges in HV machines; initial considerations for a PD specification

Cited by 25 publications

References 5 publications

An Improved Methodological Approach for Denoising of Partial Discharge Data by the Wavelet Transform

An Improved Methodological Approach for Denoising of Partial Discharge Data by the Wavelet Transform

A Review of Online Partial Discharge Measurement of Large Generators

Identification of stator insulation deterioration using on-line partial discharge testing

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