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ABSTRACT: Partial discharge (PD) signals generated within electrical power equipment can be used to assess the condition of the insulation. In practice, testing often results in multiple PD sources. In order to assess the impact of individual PD sources, signals must first be discriminated from one another. This paper presents a procedure for the identification of PD signals generated by multiple sources. Starting with the assumption that different PD sources will display unique signal profiles this will be manifested in the distribution of energies with respect to frequency and time. Therefore the technique presented is based on the comparison of signal energies associated with particular wavelet-decomposition levels. Principal component analysis is adopted to reduce the dimensionality of the data, whilst minimizing lost information in the data concentration step. Physical parameters are extracted from individual PD pulses and projected into 3-dimensional space to allow clustering of data from specific PD sources. The density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm is chosen for its ability to discover clusters of arbitrary shape in n-dimension space. PD data from individual clusters can then be further analyzed by projecting the clustered data with respect to the original phase relationship. Results and analysis of the technique are compared for experimentally measured PD data from a range of sources commonly found in three different types of high voltage (HV) equipment; ac synchronous generators, induction motors and distribution cables. These experiments collect data using varied test arrangements including sensors with different bandwidths to demonstrate the robustness and indicate the potential for wide applicability of the technique to PD analysis for a range of insulation systems.
IEEE Transactions on Dielectrics and Electrical Insulation 11/2011; · 1.09 Impact Factor
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ABSTRACT: Power distribution networks represent a dynamic and complex challenge with regard to the issues of maintenance and providing a reliable, high quality supply. Utilities historically used regular off-line testing to inform themselves of the health of their assets. This method is reasonably effective for this purpose but does have certain drawbacks associated with it; customer supply can be interrupted during the testing process and the cable sample is not tested under normal working conditions. The modern approach for understanding the health of medium voltage (MV) distribution systems is to continuously monitor the assets whilst on-line. The analysis of the captured data is then used to inform decisions regarding asset replacement and maintenance strategies. Partial discharge (PD) activity is widely recognized as a symptom linked to the degradation of high voltage plant. EDF Energy Networks sponsored research is being undertaken to investigate the evolution of PD activity within paper insulated lead covered (PILC) cables containing known defects. An experiment has been designed to stress cable sections in a such a manner that is representative of the conditions met by on-line circuits. A cable section containing a defect that is known to lead to the failure of in-service cables has been PD tested over a range of operational temperatures. The experiment utilizes three-phase energization and thermal cycling to replicate the daily load pattern experienced by circuits in the field.
Solid Dielectrics (ICSD), 2010 10th IEEE International Conference on; 08/2010
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ABSTRACT: Cable distribution networks are inherently complex and inaccessible systems; many of them are coming to the end of their original design life. As assets, they represent a dynamic and challenging issue with regard to the tasks of maintenance and management. Partial discharge (PD) has long been recognized as both a cause and symptom of the degradation of dielectric materials that protect high voltage plant. Utilities use the analysis of PD activity to make pre-fault decisions in areas such as maintenance, supply continuity and asset management. On-line PD monitoring systems are still in their relative infancy. An EDF Energy Networks funded research is investigating and identifying trends in PD activity associated with specific faults that commonly occur in distribution networks. In this paper an experiment to mimic the conditions experienced by on-line cable sections in the field is described. PD measurement has been obtained using conventional techniques covered in IEC 60270 in parallel with a commercially available substation monitor that is employed in distribution networks worldwide. Later work will involve using this experiment to PD test cable samples that contain a range of defects. It is hoped that each defect mechanism will produce an unique trend in PD activity as it degrades towards failure.
Electrical Insulation (ISEI), Conference Record of the 2010 IEEE International Symposium on; 07/2010
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ABSTRACT: Cable distribution networks are inherently complex and inaccessible systems; many of them are coming to the end of their original design life. As assets, they represent a dynamic and challenging issue with regard to the tasks of maintenance and management. Partial discharge (PD) has long been recognized as both a cause and symptom of the degradation of dielectric materials that protect high voltage plant. Utilities use the analysis of PD activity to make pre-fault decisions in areas such as maintenance, supply continuity and asset management. On-line PD monitoring systems are still in their relative infancy. An EDF Energy Networks funded research is investigating and identifying trends in PD activity associated with specific faults that commonly occur in distribution networks. In this paper an experiment to mimic the conditions experienced by on-line cable sections in the field is described. PD measurement has been obtained using conventional techniques covered in IEC 60270 in parallel with a commercially available substation monitor that is employed in distribution networks worldwide. Later work will involve using this experiment to PD test cable samples that contain a range of defects. It is hoped that each defect mechanism will produce an unique trend in PD activity as it degrades towards failure.
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[show abstract]
[hide abstract]
ABSTRACT: Power distribution networks represent a dynamic and complex challenge with regard to the issues of maintenance and providing a reliable, high quality supply. Utilities historically used regular off-line testing to inform themselves of the health of their assets. This method is reasonably effective for this purpose but does have certain drawbacks associated with it; customer supply can be interrupted during the testing process and the cable sample is not tested under normal working conditions. The modern approach for understanding the health of medium voltage (MV) distribution systems is to continuously monitor the assets whilst on-line. The analysis of the captured data is then used to inform decisions regarding asset replacement and maintenance strategies. Partial discharge (PD) activity is widely recognized as a symptom linked to the degradation of high voltage plant. EDF Energy Networks sponsored research is being undertaken to investigate the evolution of PD activity within paper insulated lead covered (PILC) cables containing known defects. An experiment has been designed to stress cable sections in a such a manner that is representative of the conditions met by on-line circuits. A cable section containing a defect that is known to lead to the failure of in-service cables has been PD tested over a range of operational temperatures. The experiment utilizes three-phase energization and thermal cycling to replicate the daily load pattern experienced by circuits in the field.
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[show abstract]
[hide abstract]
ABSTRACT: Power distribution cable networks represent a dynamic and complex challenge with regard to the issues of maintenance and providing a reliable, high quality supply of electrical power. Utilities historically used regular off-line testing to investigate the health of their assets. This method of testing is reasonably effective for this purpose but does have certain drawbacks associated with it; customer supply can be interrupted during the testing process and the cables are generally not tested under normal operating conditions. Meaning that the test data is not representative of the Partial discharge (PD) activity that is apparent under on-line conditions and the testing activity itself could trigger previously dormant PD sources. The modern approach for understanding the health of medium voltage (MV) cable distribution networks is to continuously monitor the assets whilst on-line. Analysis if the field data is then used to inform decisions regarding asset replacement and maintenance strategies. PD activity is widely recognised as a symptom linked to the degradation of the dielectric properties of high voltage plant. UK Power Networks sponsored research is being undertaken to investigate the evolution of PD activity within three-phase paper insulated lead covered (PILC) cables containing introduced defects. An experiment has been designed to stress cable lengths in a manner that is representative of the conditions met by on-line circuits [1]. A cable section containing a defect that is known to lead to the premature failure of in-service cables has been PD tested over a range of operating temperatures. The experiment utilizes three-phase energization at rated voltage as well as thermal cycling of the cable to replicate the daily load pattern experienced by circuits in the field. The extension to this work involves PD testing cable samples containing a range of defects to produce a data set consisting of PD pulses produced by varied sources. Analysis of this data should lead to a better understanding of the signals produced by the premature ageing of these types of cable.
