Periodic Reporting for period 1 - emiT (ELECTROMAGNETIC TIME REVERSAL FOR ON-LINE PARTIAL DISCHARGE LOCATION IN TRANSMISSION AND DISTRIBUTION NETWORKS)
Berichtszeitraum: 2019-06-01 bis 2021-05-31
Energy is globally crucial and must be provided when and where needed to avoid a serious impact on society. Among all forms of energy, electricity has an increasingly central role. The rapid and large-scale introduction of renewable energy sources to provide sufficient clean energy to help solve the problems related to climate change is a priority for many governments. It is expected that by 2050 electricity consumption will represent 1/3 of all energy use.
Electricity security is the power system's capability to withstand disturbances or contingencies with an acceptable service disruption level and it represents a crucial concern for policy decision making at all levels in any country. In Europe, energy security is 1 of the 4 actions of the Integrated Roadmap of the EU Strategic Energy Technology Plan. Because electricity is difficult to store efficiently, demand and supply must be matched in real time, hence the need to ensure the resilience of transmission and distribution networks is paramount. Often, service disruption is due to cable insulation damage, which is something often associated with partial discharge (PD) events. PDs are localized electrical discharges that partially bridge the insulation between conductors. PDs are one of the best early-warning indicators of insulation degradation and potential failure meaning that PD location is an excellent method to monitor network integrity and a desirable protection method to enhance electricity security.
The emiT project’s main aim was to develop a new on-line PD location method, based on the innovative electromagnetic time reversal (EMTR) theory, in a way that can overcome the shortcomings associated with classical PD location techniques, resulting in improved accuracy, tolerance of electrical noise, coping with uneven and jointed cables, and reaching these goals using only one observation point (OP) thus avoiding the use of complex synchronised measurements necessary for the classical location approach.
The project focused on 3 specific objectives:
1. To develop a numerical simulation of the system useful to analyse PD events and PD signal propagation on power networks, through training on computational electromagnetics (CEM) at the Host Institution.
2. To design a new EMTR-based method, studying EMTR theory in collaboration with the Academic project partner, The École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, where the first applications of EMTR in the electromagnetic compatibility (EMC) field have been studied.
3. To experimentally validate the method in networks on service, with HVPD ltd, in Salford, UK, the industrial project partner , experts in on-line PD condition monitoring.
Electricity security is the power system's capability to withstand disturbances or contingencies with an acceptable service disruption level and it represents a crucial concern for policy decision making at all levels in any country. In Europe, energy security is 1 of the 4 actions of the Integrated Roadmap of the EU Strategic Energy Technology Plan. Because electricity is difficult to store efficiently, demand and supply must be matched in real time, hence the need to ensure the resilience of transmission and distribution networks is paramount. Often, service disruption is due to cable insulation damage, which is something often associated with partial discharge (PD) events. PDs are localized electrical discharges that partially bridge the insulation between conductors. PDs are one of the best early-warning indicators of insulation degradation and potential failure meaning that PD location is an excellent method to monitor network integrity and a desirable protection method to enhance electricity security.
The emiT project’s main aim was to develop a new on-line PD location method, based on the innovative electromagnetic time reversal (EMTR) theory, in a way that can overcome the shortcomings associated with classical PD location techniques, resulting in improved accuracy, tolerance of electrical noise, coping with uneven and jointed cables, and reaching these goals using only one observation point (OP) thus avoiding the use of complex synchronised measurements necessary for the classical location approach.
The project focused on 3 specific objectives:
1. To develop a numerical simulation of the system useful to analyse PD events and PD signal propagation on power networks, through training on computational electromagnetics (CEM) at the Host Institution.
2. To design a new EMTR-based method, studying EMTR theory in collaboration with the Academic project partner, The École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, where the first applications of EMTR in the electromagnetic compatibility (EMC) field have been studied.
3. To experimentally validate the method in networks on service, with HVPD ltd, in Salford, UK, the industrial project partner , experts in on-line PD condition monitoring.
A Transmission Line Matrix (TLM)-based numerical model was developed to design the new PD location method. The model is able to describe PDs in the context of power networks and to analyse the PD-generated conducted/radiated electromagnetic emissions and their propagation. PD signals on power networks are subject to distortion phenomenon during propagation caused by the variation with frequency of the cable impedance and by the presence of on-line impedance mismatches due to inhomogeneous cable sections, joints, or ring main units. Distortion modifies the PD signals propagation speed and shape, affecting the effectiveness and accuracy of the on-line PD location methods. This phenomenon must be considered during the design process of new PD location methods. The developed TLM numerical test bench reproduces PD signal distortion, so it is a suitable tool for the design of PD location methods and, also, sensors for PD detection.
Using the developed numerical test bench, the new PD location method based on the EMTR theory was designed in conjunction with the EPFL and the University of Applied Sciences and Arts Western Switzerland. The new method is based on the invariance under time reversal in lossless lines of the telegrapher’s equations that describe the PD signal propagation on power lines. The developed method is based on measurements of PD signals at one OP of the line, time reversing the measured signal and back-injecting the time-reversed PD signal into a lossless TLM model of the line. The use of a lossless line for the time reversal phase of the analysis ensures the generality of the method, relying on a knowledge of the generic parameters of the cable under test and not needing a detailed knowledge of the electromagnetic structure of a particular line. The effectiveness of the method was numerically demonstrated and then, experimentally validated, with HVPD Ltd using in-service MV power networks, also with the presence of electromagnetic interference and line impedance mismatches.
The experimental investigations showed that the designed method can localise PDs using one OP with a relative error lower than 1% and a computational time of 2-3 minutes, performing more than 200 simulations of more than 1000 nodes each, for line 2 km long.
The project results have been disseminated through conferences, journal publications and a project website. The activities have been presented at conferences organised by the IWCS, regarded as the premier technical conferences in electrical cables for the industry in USA, and by the IEEE, the world’s largest technical professional organization dedicated to advancing technology for the humanity benefit. The outcomes have been published in IEEE Transactions, in the open access peer-reviewed journal, Energies, published by MDPI, and in the Science and Engineering Journal, published by CIGRE community, the world's foremost source of power system expertise since 1921. The project website is at: https://emit.our.dmu.ac.uk.
Using the developed numerical test bench, the new PD location method based on the EMTR theory was designed in conjunction with the EPFL and the University of Applied Sciences and Arts Western Switzerland. The new method is based on the invariance under time reversal in lossless lines of the telegrapher’s equations that describe the PD signal propagation on power lines. The developed method is based on measurements of PD signals at one OP of the line, time reversing the measured signal and back-injecting the time-reversed PD signal into a lossless TLM model of the line. The use of a lossless line for the time reversal phase of the analysis ensures the generality of the method, relying on a knowledge of the generic parameters of the cable under test and not needing a detailed knowledge of the electromagnetic structure of a particular line. The effectiveness of the method was numerically demonstrated and then, experimentally validated, with HVPD Ltd using in-service MV power networks, also with the presence of electromagnetic interference and line impedance mismatches.
The experimental investigations showed that the designed method can localise PDs using one OP with a relative error lower than 1% and a computational time of 2-3 minutes, performing more than 200 simulations of more than 1000 nodes each, for line 2 km long.
The project results have been disseminated through conferences, journal publications and a project website. The activities have been presented at conferences organised by the IWCS, regarded as the premier technical conferences in electrical cables for the industry in USA, and by the IEEE, the world’s largest technical professional organization dedicated to advancing technology for the humanity benefit. The outcomes have been published in IEEE Transactions, in the open access peer-reviewed journal, Energies, published by MDPI, and in the Science and Engineering Journal, published by CIGRE community, the world's foremost source of power system expertise since 1921. The project website is at: https://emit.our.dmu.ac.uk.
The project activities led to the design of a new reliable PD location method that overcomes the most challenging limitations associated with existing traveling wave-based or reflectometry PD location techniques. The new EMTR PD location method is able to localise PDs with a computational time of a few minutes and a relative error lower than 1% using only one OP along the line, even when the PD signal is subject to high levels of interference. These challenges are addressed by the reflectometry methods using more than one OP with complex synchronised measurements and using the powerful, but computationally heavy, wavelet transform techniques to de-noise the PD signals.
The method, developing a fault-preventive action and contributing to avoiding supply interruptions and blackouts, addresses the reliability and resilience of power networks and helps in guaranteeing Electricity Security. In addition, the adoption of a method that can help to provide early warning of future faults and blackout achieves the following timely objectives of technological, economical and societal relevance: to provide a suitable on-line monitoring of the network integrity improving the reliability; to increase equipment lifetime; to reduce overall operating costs and increase plant productivity; to minimize outage duration of power supply, improving the power quality, the customer satisfaction and the quality of life. Potential users of the project results are cable manufacturers, cable testers, electricity supply companies, network monitoring companies, together with the scientists in the field of power systems reliability, electromagnetic compatibility, source localisation of both intentional and unintentional electromagnetic disturbances.
The method, developing a fault-preventive action and contributing to avoiding supply interruptions and blackouts, addresses the reliability and resilience of power networks and helps in guaranteeing Electricity Security. In addition, the adoption of a method that can help to provide early warning of future faults and blackout achieves the following timely objectives of technological, economical and societal relevance: to provide a suitable on-line monitoring of the network integrity improving the reliability; to increase equipment lifetime; to reduce overall operating costs and increase plant productivity; to minimize outage duration of power supply, improving the power quality, the customer satisfaction and the quality of life. Potential users of the project results are cable manufacturers, cable testers, electricity supply companies, network monitoring companies, together with the scientists in the field of power systems reliability, electromagnetic compatibility, source localisation of both intentional and unintentional electromagnetic disturbances.