cliff walton | Imperial College London (original) (raw)

Papers by cliff walton

Research paper thumbnail of Managing Large-Scale Multi-Voltage Distribution System Analysis

Research paper thumbnail of Special graphics requirements or graphic interactive analysis ofhigh density city centre and urban distribution networks

The London Electricity Board operates a large distribution system characterised by a very dense c... more The London Electricity Board operates a large distribution system characterised by a very dense city centre system with a high demand growth. The authors describe the extension of an interactive graphics based network analysis system into this environment and describe the special facilities found necessary to achieve the considerable potential benefits. They outline the background to the Board's needs, and give a review of the critical network data management facilities required, emphasising the close ties to interactive graphic display facilities. Various special application package requirements are also described as part of an extended integrated system. The conclusions are that the new generation of distributed graphics based network information systems have considerable potential. It can be foreseen that district engineers will carry out their own local data capture, updating and analysis without specialist training and yet achieve full corporate data integration and network...

Research paper thumbnail of Detecting and locating MV failure before it occurs. Experience with live line partial discharge detection on underground paper insulated 11 kV cables in London

16th International Conference and Exhibition on Electricity Distribution (CIRED 2001), 2001

ABSTRACT Detecting and locating incipient failure in underground cables before electrical faults ... more ABSTRACT Detecting and locating incipient failure in underground cables before electrical faults occur has significant benefits in terms of customer satisfaction and quality of supply statistics particularly for “worst served customers” and investment targeting. Timely location and targeted replacement of specific sections of unsatisfactory circuits enables the effective service life of the whole circuit to be economically extended. As some 98% of the supply interruptions in London arise from cable systems, London Power Networks (LPN) is seeking to develop techniques to eliminate cable faults before they occur. LPN have recently commenced installing live line multi-functional monitoring equipment on 300 higher fault rate feeder circuits. Preliminary results of live line condition monitoring have shown very encouraging results in being able to detect and locate failure before it occurs

Research paper thumbnail of The Location of Switchgear Partial Discharge by Panel and Techniques to Correlate Switchgear and Cable Partial Discharge with Load and Substation Environment

This paper considers recent developments in on-line condition monitoring techniques both in terms... more This paper considers recent developments in on-line condition monitoring techniques both in terms of new hardware and software developments and new analysis and classification techniques.

Research paper thumbnail of C I R E D SECONDARY SUBSTATION LOAD PROFILING –IDENTIFICATION AND VISUALISATION OF CHANGES

This paper outlines the analytical and graphical techniques being used to classify secondary subs... more This paper outlines the analytical and graphical techniques being used to classify secondary substation load profiles and identify when changes occur. The visualisation techniques being developed to assist Planning Engineers with network assessment of load growth and changing load type are illustrated. The paper also details the projects findings in respect of DG connected at low voltage (LV) and the masking of load.

Research paper thumbnail of Tools for partial discharge testing MV cables and plant

Probably the most useful diagnostic for high voltage insulation is a measurement of partial disch... more Probably the most useful diagnostic for high voltage insulation is a measurement of partial discharge (PD) activity. Even for insulation systems which are designed to be discharge free (such as polymeric cables, enclosed busbars etc), where PD activity is nevertheless present, and hence potentially responsible for insulation deterioration, measurements of PD activity are vital to avoid plant failure. As the PD voltages tend to be small, other electromagnetic interfering signals are always a problem. In addition, there may be many PD sources in a power network, all contributing to the overall measured pulses. The separation and localisation of the PD activity is still a major task in improving the quality of the measured PD data.

Research paper thumbnail of Some advances in PD monitoring for high voltage cables

Some advances have been with detection of the PD activity of medium voltage cables, using an on-l... more Some advances have been with detection of the PD activity of medium voltage cables, using an on-line method of detection. This paper illustrates the relationship between the original VLF (very low frequency) power supply results of PD mapping in medium voltage cables, and the newer on-line monitoring methods. The on-line methods offer the possibility of scanning circuits quickly and relatively cheaply to obtain meaningful PD data for older installed cables

Research paper thumbnail of Incipient fault detection and management of underground LV networks

Research paper thumbnail of REmote control of urban 11kv distribution systems in London Electricity

ABSTRACT First Page of the Article

Research paper thumbnail of Avoidance of MV switchgear failure case studies of on-line condition monitoring

IET Conference Publications, 2009

This paper considers, through a series of practical case studies, the avoidance of major incident... more This paper considers, through a series of practical case studies, the avoidance of major incidents through the targeted use of on-line condition monitoring of MV indoor switchboards. A technique to pin point the location of partial discharge (pd) using time of flight measurement techniques is discussed.

Research paper thumbnail of Partial discharge diagnostics of defective medium voltage three-phase PILC cables

ABSTRACT There are a number of medium voltage (MV) power distribution cable networks worldwide th... more ABSTRACT There are a number of medium voltage (MV) power distribution cable networks worldwide that are constructed predominantly of mass impregnated paper cables - London being one of these. Paper insulated lead covered (PILC) cables were extensively laid in the 50s and 60s before the introduction of cheaper polymeric alternatives that were sufficiently reliable. The current operational state of these networks has shown a gradual increase in failure rates of the previously reliable paper cables that are drawing to the end of their expected design life. Utilities are faced with the prospect of the impending failure of large sections of their prized asset and are keen to develop tools to better understand the health of their hardware. The analysis of partial discharge (PD) signals produced by the cables has been identified as a economically viable option to provide continuous condition monitoring of PILC cable circuits. Clearly, a comprehensive understanding of how PD activity relates to the various failure mechanisms exhibited by cable circuits in the field is required. In order to generate representative and repeatable PD signals from a number of PILC cable samples under rated conditions, an experiment was designed and commissioned. The scope of this paper is to introduce two cable degradation mechanisms that were applied to test cable and show the associated PD activity that was produced. A recently published technique for PD source discrimination was coupled with an understanding of the system and applied to the experiment data to isolate the signals specific to each degradation mechanism.

Research paper thumbnail of Partial discharge testing of defective three-phase PILC cable under rated conditions

The ability to accurately monitor the health of power distribution plant is a very attractive pro... more The ability to accurately monitor the health of power distribution plant is a very attractive prospect for utility companies. This capability would provide a system that engineers could use to assess the real-time state of the network. Analysis of the data produced could allow for more informed decisions to be made in the areas of asset replacement and maintenance scheduling amongst others. It is widely accepted that partial discharge activity is linked with the electrical ageing/degradation of high voltage equipment. Work at Southampton is focused on obtaining a better understanding of the characteristics and trends of partial discharge events associated with medium voltage cables under, 'real life' conditions. An experiment has been developed that allows for service conditions to be applied to defective paper insulated lead covered cable samples. The samples under investigation were exposed to mechanical damage designed to replicate typical problems found on an active circuit. Partial discharge measurement was undertaken during the stressing process.

Research paper thumbnail of Partial discharge in medium voltage three-phase cables

Cable distribution networks are inherently complex and inaccessible systems; many of them are com... more 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

Research paper thumbnail of Networks for tomorrow. Urban and city centre underground distribution for the 21st Century

Fifth International Conference on Trends in Distribution Switchgear: 400V-145kV for Utilities and Private Networks, 1998

ABSTRACT The challenge for electricity utilities in the 21st Century is to deliver ever more reli... more ABSTRACT The challenge for electricity utilities in the 21st Century is to deliver ever more reliable service at reduced cost and with fewer technical and support staff. This creates the driver towards the next generation of distribution networks and management systems. Real-time information and controls integrated with automated network management systems, are required to enable limited investment to be directed at those networks with the poorest performance and highest operational costs. Here, the author describes how London Electricity (UK) has developed an integrated technology strategy for underground distribution development with an underlying methodology which can be adopted for use in other utilities

Research paper thumbnail of Supergen futurenet and flexnet

The paper outlines the work and conclusions of the four year Supergen FutureNet consortium of eig... more The paper outlines the work and conclusions of the four year Supergen FutureNet consortium of eight UK universities and many industrial sponsors that concluded in summer 2007. It then sets out the research program and objectives of the follow-on four year £7m FlexNet consortium and its implications for Smart Grids.

Research paper thumbnail of Discrimination of multiple PD sources using wavelet decomposition and principal component analysis

IEEE Transactions on Dielectrics and Electrical Insulation, 2000

Partial discharge (PD) signals generated within electrical power equipment can be used to assess ... more 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

Research paper thumbnail of Autonomous classification of PD sources within three-phase 11 kV PILC cables

IEEE Transactions on Dielectrics and Electrical Insulation, 2000

ABSTRACT To allow utilities to fulfill self-imposed and regulative performance targets that apply... more ABSTRACT To allow utilities to fulfill self-imposed and regulative performance targets that apply to them, the demand for new tools to help judge the health of modern power distribution networks has increased. The analysis of partial discharge (PD) signals has been identified as a potential diagnostic tool for the condition monitoring of HV plant. In order to investigate the PD activity produced by a range of defects within three-phase paper insulated lead covered (PILC) distribution cable under rated conditions, an experiment has been developed. The experiment incorporates a commercially available on-line PD measurement system employing a high frequency current transformer (HFCT) to record PD data in a manner that is currently in operation in the UK. By replicating field conditions and using realistic hardware to collect experiment data, that any findings or analysis tools developed during this investigation are directly transferable to use in the field. Four defective cable samples, each containing different imperfections that are known to reduce in-service plant life have been fabricated and extensively PD tested. The raw experiment data was processed to produce a dataset containing a range of features from individual PD pulses including time, frequency and time-frequency information. This data was used to optimize and train several support vector machine (SVM) models to perform automated pulse classification. Four SVM models were tested using different combinations of pulse features to identify which characteristics were most effective at transferring source dependent information for classification. The results of the automated algorithm validated the approach returning a classification accuracy of 91.1%.

Research paper thumbnail of Benefits of large scale urban distribution network automation and their role in meeting enhanced customer expectation and regulatory regimes

Electricity Distribution, 2001. Part 1: Contributions …, 2001

London Electricity and London Power Networks have developed and implemented a comprehensive distr... more London Electricity and London Power Networks have developed and implemented a comprehensive distribution network automation system for managing large scale urban distribution networks. Remote control and telemetry has been installed at over 4000 ...

Research paper thumbnail of A new Method for Automatic Multiple Partial Discharge Classification

A new wavelet based feature parameter have been developed to represent the characteristics of PD ... more A new wavelet based feature parameter have been developed to represent the characteristics of PD activities, ie the wavelet decomposition energy of PD pulses measured from non-conventional ultra wide bandwidth PD sensors such as capacitive couplers (CC) ...

Research paper thumbnail of Managing Large-Scale Multi-Voltage Distribution System Analysis

Research paper thumbnail of Special graphics requirements or graphic interactive analysis ofhigh density city centre and urban distribution networks

The London Electricity Board operates a large distribution system characterised by a very dense c... more The London Electricity Board operates a large distribution system characterised by a very dense city centre system with a high demand growth. The authors describe the extension of an interactive graphics based network analysis system into this environment and describe the special facilities found necessary to achieve the considerable potential benefits. They outline the background to the Board's needs, and give a review of the critical network data management facilities required, emphasising the close ties to interactive graphic display facilities. Various special application package requirements are also described as part of an extended integrated system. The conclusions are that the new generation of distributed graphics based network information systems have considerable potential. It can be foreseen that district engineers will carry out their own local data capture, updating and analysis without specialist training and yet achieve full corporate data integration and network...

Research paper thumbnail of Detecting and locating MV failure before it occurs. Experience with live line partial discharge detection on underground paper insulated 11 kV cables in London

16th International Conference and Exhibition on Electricity Distribution (CIRED 2001), 2001

ABSTRACT Detecting and locating incipient failure in underground cables before electrical faults ... more ABSTRACT Detecting and locating incipient failure in underground cables before electrical faults occur has significant benefits in terms of customer satisfaction and quality of supply statistics particularly for “worst served customers” and investment targeting. Timely location and targeted replacement of specific sections of unsatisfactory circuits enables the effective service life of the whole circuit to be economically extended. As some 98% of the supply interruptions in London arise from cable systems, London Power Networks (LPN) is seeking to develop techniques to eliminate cable faults before they occur. LPN have recently commenced installing live line multi-functional monitoring equipment on 300 higher fault rate feeder circuits. Preliminary results of live line condition monitoring have shown very encouraging results in being able to detect and locate failure before it occurs

Research paper thumbnail of The Location of Switchgear Partial Discharge by Panel and Techniques to Correlate Switchgear and Cable Partial Discharge with Load and Substation Environment

This paper considers recent developments in on-line condition monitoring techniques both in terms... more This paper considers recent developments in on-line condition monitoring techniques both in terms of new hardware and software developments and new analysis and classification techniques.

Research paper thumbnail of C I R E D SECONDARY SUBSTATION LOAD PROFILING –IDENTIFICATION AND VISUALISATION OF CHANGES

This paper outlines the analytical and graphical techniques being used to classify secondary subs... more This paper outlines the analytical and graphical techniques being used to classify secondary substation load profiles and identify when changes occur. The visualisation techniques being developed to assist Planning Engineers with network assessment of load growth and changing load type are illustrated. The paper also details the projects findings in respect of DG connected at low voltage (LV) and the masking of load.

Research paper thumbnail of Tools for partial discharge testing MV cables and plant

Probably the most useful diagnostic for high voltage insulation is a measurement of partial disch... more Probably the most useful diagnostic for high voltage insulation is a measurement of partial discharge (PD) activity. Even for insulation systems which are designed to be discharge free (such as polymeric cables, enclosed busbars etc), where PD activity is nevertheless present, and hence potentially responsible for insulation deterioration, measurements of PD activity are vital to avoid plant failure. As the PD voltages tend to be small, other electromagnetic interfering signals are always a problem. In addition, there may be many PD sources in a power network, all contributing to the overall measured pulses. The separation and localisation of the PD activity is still a major task in improving the quality of the measured PD data.

Research paper thumbnail of Some advances in PD monitoring for high voltage cables

Some advances have been with detection of the PD activity of medium voltage cables, using an on-l... more Some advances have been with detection of the PD activity of medium voltage cables, using an on-line method of detection. This paper illustrates the relationship between the original VLF (very low frequency) power supply results of PD mapping in medium voltage cables, and the newer on-line monitoring methods. The on-line methods offer the possibility of scanning circuits quickly and relatively cheaply to obtain meaningful PD data for older installed cables

Research paper thumbnail of Incipient fault detection and management of underground LV networks

Research paper thumbnail of REmote control of urban 11kv distribution systems in London Electricity

ABSTRACT First Page of the Article

Research paper thumbnail of Avoidance of MV switchgear failure case studies of on-line condition monitoring

IET Conference Publications, 2009

This paper considers, through a series of practical case studies, the avoidance of major incident... more This paper considers, through a series of practical case studies, the avoidance of major incidents through the targeted use of on-line condition monitoring of MV indoor switchboards. A technique to pin point the location of partial discharge (pd) using time of flight measurement techniques is discussed.

Research paper thumbnail of Partial discharge diagnostics of defective medium voltage three-phase PILC cables

ABSTRACT There are a number of medium voltage (MV) power distribution cable networks worldwide th... more ABSTRACT There are a number of medium voltage (MV) power distribution cable networks worldwide that are constructed predominantly of mass impregnated paper cables - London being one of these. Paper insulated lead covered (PILC) cables were extensively laid in the 50s and 60s before the introduction of cheaper polymeric alternatives that were sufficiently reliable. The current operational state of these networks has shown a gradual increase in failure rates of the previously reliable paper cables that are drawing to the end of their expected design life. Utilities are faced with the prospect of the impending failure of large sections of their prized asset and are keen to develop tools to better understand the health of their hardware. The analysis of partial discharge (PD) signals produced by the cables has been identified as a economically viable option to provide continuous condition monitoring of PILC cable circuits. Clearly, a comprehensive understanding of how PD activity relates to the various failure mechanisms exhibited by cable circuits in the field is required. In order to generate representative and repeatable PD signals from a number of PILC cable samples under rated conditions, an experiment was designed and commissioned. The scope of this paper is to introduce two cable degradation mechanisms that were applied to test cable and show the associated PD activity that was produced. A recently published technique for PD source discrimination was coupled with an understanding of the system and applied to the experiment data to isolate the signals specific to each degradation mechanism.

Research paper thumbnail of Partial discharge testing of defective three-phase PILC cable under rated conditions

The ability to accurately monitor the health of power distribution plant is a very attractive pro... more The ability to accurately monitor the health of power distribution plant is a very attractive prospect for utility companies. This capability would provide a system that engineers could use to assess the real-time state of the network. Analysis of the data produced could allow for more informed decisions to be made in the areas of asset replacement and maintenance scheduling amongst others. It is widely accepted that partial discharge activity is linked with the electrical ageing/degradation of high voltage equipment. Work at Southampton is focused on obtaining a better understanding of the characteristics and trends of partial discharge events associated with medium voltage cables under, 'real life' conditions. An experiment has been developed that allows for service conditions to be applied to defective paper insulated lead covered cable samples. The samples under investigation were exposed to mechanical damage designed to replicate typical problems found on an active circuit. Partial discharge measurement was undertaken during the stressing process.

Research paper thumbnail of Partial discharge in medium voltage three-phase cables

Cable distribution networks are inherently complex and inaccessible systems; many of them are com... more 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

Research paper thumbnail of Networks for tomorrow. Urban and city centre underground distribution for the 21st Century

Fifth International Conference on Trends in Distribution Switchgear: 400V-145kV for Utilities and Private Networks, 1998

ABSTRACT The challenge for electricity utilities in the 21st Century is to deliver ever more reli... more ABSTRACT The challenge for electricity utilities in the 21st Century is to deliver ever more reliable service at reduced cost and with fewer technical and support staff. This creates the driver towards the next generation of distribution networks and management systems. Real-time information and controls integrated with automated network management systems, are required to enable limited investment to be directed at those networks with the poorest performance and highest operational costs. Here, the author describes how London Electricity (UK) has developed an integrated technology strategy for underground distribution development with an underlying methodology which can be adopted for use in other utilities

Research paper thumbnail of Supergen futurenet and flexnet

The paper outlines the work and conclusions of the four year Supergen FutureNet consortium of eig... more The paper outlines the work and conclusions of the four year Supergen FutureNet consortium of eight UK universities and many industrial sponsors that concluded in summer 2007. It then sets out the research program and objectives of the follow-on four year £7m FlexNet consortium and its implications for Smart Grids.

Research paper thumbnail of Discrimination of multiple PD sources using wavelet decomposition and principal component analysis

IEEE Transactions on Dielectrics and Electrical Insulation, 2000

Partial discharge (PD) signals generated within electrical power equipment can be used to assess ... more 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

Research paper thumbnail of Autonomous classification of PD sources within three-phase 11 kV PILC cables

IEEE Transactions on Dielectrics and Electrical Insulation, 2000

ABSTRACT To allow utilities to fulfill self-imposed and regulative performance targets that apply... more ABSTRACT To allow utilities to fulfill self-imposed and regulative performance targets that apply to them, the demand for new tools to help judge the health of modern power distribution networks has increased. The analysis of partial discharge (PD) signals has been identified as a potential diagnostic tool for the condition monitoring of HV plant. In order to investigate the PD activity produced by a range of defects within three-phase paper insulated lead covered (PILC) distribution cable under rated conditions, an experiment has been developed. The experiment incorporates a commercially available on-line PD measurement system employing a high frequency current transformer (HFCT) to record PD data in a manner that is currently in operation in the UK. By replicating field conditions and using realistic hardware to collect experiment data, that any findings or analysis tools developed during this investigation are directly transferable to use in the field. Four defective cable samples, each containing different imperfections that are known to reduce in-service plant life have been fabricated and extensively PD tested. The raw experiment data was processed to produce a dataset containing a range of features from individual PD pulses including time, frequency and time-frequency information. This data was used to optimize and train several support vector machine (SVM) models to perform automated pulse classification. Four SVM models were tested using different combinations of pulse features to identify which characteristics were most effective at transferring source dependent information for classification. The results of the automated algorithm validated the approach returning a classification accuracy of 91.1%.

Research paper thumbnail of Benefits of large scale urban distribution network automation and their role in meeting enhanced customer expectation and regulatory regimes

Electricity Distribution, 2001. Part 1: Contributions …, 2001

London Electricity and London Power Networks have developed and implemented a comprehensive distr... more London Electricity and London Power Networks have developed and implemented a comprehensive distribution network automation system for managing large scale urban distribution networks. Remote control and telemetry has been installed at over 4000 ...

Research paper thumbnail of A new Method for Automatic Multiple Partial Discharge Classification

A new wavelet based feature parameter have been developed to represent the characteristics of PD ... more A new wavelet based feature parameter have been developed to represent the characteristics of PD activities, ie the wavelet decomposition energy of PD pulses measured from non-conventional ultra wide bandwidth PD sensors such as capacitive couplers (CC) ...