Browsing by Author "Duffy, Alistair"
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Item Metadata only 3D Model of partial discharge in defects with different sizes and positions in power cable for distribution and transmission networks(IET, 2020-10-14) Ragusa, Antonella; Sasse, Hugh; Duffy, AlistairThe knowledge of partial discharge (PD) phenomena inside electrical insulation of power cables is an important issue for assessing the insulation condition and its degradation state, obtaining information about the likelihood of failure. PDs cause signals to propagate along the cable, as noise phenomena, and contribute to the insulation degradation, culminating in a disruptive fault with the interruption of power supply. Therefore, PDs are considered the best ‘early warning’ indicators of insulation degradation and their modelling, with the development of on-line PDs location methods, are important topics to increase the networks’ electricity security. In this study, a three-dimensional (3D) model of PD events using the CST STUDIO® Dassault software is proposed. PDs inside air inclusions in epoxy-resin are analysed with different shapes, positions and sizes of the defect. The electric-field distribution is evaluated with the conduction current inside the void and the apparent charges induced on the electrode. The effectiveness of the model is validated by comparing the simulation results with other published experimental results. Finally, a description of a 3D–1D hybrid model useful to describe the propagation of PD signals in power networks is given.Item Open Access Application to Real Power Networks of a Method to Locate Partial Discharges Based on Electromagnetic Time Reversal(IEEE, 2021-09-24) Ragusa, Antonella; Sasse, Hugh G.; Duffy, Alistair; Rubinstein, MarcosThe paper presents an experimental validation of a method to locate partial discharges (PDs) on power distribution and transmission networks. The method is based on electromagnetic time reversal (EMTR) theory, and it uses a Transmission Line Matrix (TLM) model to describe the propagation of the PD signals in the reversed time. Since PDs are regarded as a symptom of insulation degradation, on-line PD location is considered an important approach to monitoring the integrity of a power distribution network, with the aim of detecting and preventing faults and improving network reliability. In this paper, the EMTR-based method is described and its effectiveness in PD localization using only one measurement point is demonstrated in three real 33 kV power lines. Its effectiveness is proved with and without an on-line electromagnetically noisy environment, and its accuracy is evaluated with respect to different signal-to-noise ratio (SNR) levels of the networks. The validation shows that the method is able to locate PDs with an error of 0.14% with respect to the total length of the line in the absence of noise, and with an error that is always lower than 0.5% for an SNR down to -7 dB.Item Open Access Applying the FSV (Feature Selective Validation) method to the comparison of switching for Signal Integrity applications(IEEE, 2021) Zhang, Gang; Duffy, AlistairTo ensure good signal integrity design, there are a number of design principles that should be applied, including avoiding any breaks in a current return path, e.g. a ground plane in a multilayer stack up. Occasionally, these guidelines are not followed: possibly through necessity or convenience. However, it is helpful to the designer to understand the impact of such factors that might influence the quality of the digital signal being transmitted. Typically, such an analysis might be undertaken using eye diagrams but it is more difficult to perform comparative testing on single transitions. This paper applies the FSV method, using the modified transient analysis approach, to single transitions for a PCB track having its return path influenced by a break in the return plane; in this case, the break is a circular ‘gap’ in the ground plane. FSV’s global difference measure is used to quantify the effects of the amount of overlap of the signal track with the gap. The paper illustrates how the modified transient FSV approach can help provide quantified supporting information for the SI designer.Item Open Access Comparing Simulated Impact of Single Frequency and Multitone EMI for an Integrated Circuit(IEEE, 2022-04-21) Devaraj, Lokesh; Khan, Qazi Mashaal; Ruddle, Alastair; Duffy, AlistairElectromagnetic immunity performance characteristics for integrated circuits are currently verified using tests involving single-frequency continuous wave disturbances. In real operational environments, however, systems may be exposed to simultaneous interference sources at multiple frequencies. Simulation results obtained for the electromagnetic susceptibility of a simple voltage-controlled oscillator to randomly generated multitone interference are compared with corresponding data obtained for single frequencies. The results obtained are used to assess the validity of the current approach of testing circuit designs for immunity using single frequency noise source. Notable differences in the output response of the circuit to single and multitone interference, which could possibly lead to system malfunctions, are illustrated.Item Metadata only Design, simulation, and fabrication of a double annular ring microstrip antenna based on gaps with multiband feature(Elsevier, 2022-01-24) Al-Tumah, Wa'il A. Godaymi; Shaaban, Raed M.; Duffy, AlistairA novel double annular-ring microstrip antenna, split into six sectors, is proposed to achieve multiband operation with high gain and impedance bandwidth. The gaps on the driven and parasitic patches excite resonant frequencies that are located in the Ku-, K-, and Ka-bands thus making the antenna capable of these multiband applications. The present design is numerically and experimentally investigated. This investigation indicates that the suggested antenna achieves four operating bands, with impedance bandwidths of 1.72 GHz (12.16–13.88 GHz), 2.04 GHz (19.28–21.32 GHz), 1.54 GHz (24.04–25.58 GHz), and 1.97 GHz (27.37–29.34 GHz) which correspond to the resonant frequencies of 13.10 GHz, 20.72 GHz, 25.00 GHz, and 28.85 GHz, respectively. Also, the new design achieves good values of gain (6.11–8.31) dB and a return loss of between −16.14 dB and −21.52 dB. The commercial tool Ansoft high frequency structure simulator is used to simulate the designed antennas and it compared with the obtained measurement data. The comparison shows close agreement between the simulations and measurements.Item Open Access Detecting Electromagnetic Disturbances on Transmission Lines Using Time Reversal(IWCS, 2020-10-14) Ragusa, Antonella; Sasse, Hugh; Duffy, AlistairTransmission lines can suffer a variety of electromagnetic disturbances. These can range from intentional interference, due to malicious intent, through to the effects of lightning strikes or partial discharge. Given a high-fidelity model of the transmission line, it is possible to take measurement data and ‘run time backwards’ to identify the source of the disturbance. This paper reviews the theory and implementation of electromagnetic time reversal, provides some examples from the literature, and illustrates its operation with current research to identify the source of a partial discharge event on Medium and High Voltage cables.Item Metadata only Determination of the Physical Integrity of Ethernet Cables by Obtaining their Transmission Line Parameters from Measured Impedance Profiles(River, 2023-03-23) Ogundapo, Olusegun; Duffy, AlistairA method of determining the physical integrity of Ethernet cables by obtaining their transmission line parameters (resistance, inductance, capacitance, and conductance) from their measured impedance profiles are presented. The transmission line parameters were extracted across the cable lengths rather than frequencies used in most research. The method can be used to examine the physical integrity of Ethernet cables before their deployment. The study of the physical integrity of Ethernet cables is very important because, in typical installations, cables can be manipulated in the form of repeated coiling and uncoiling. The installation handling stress can adversely affect the signal integrity especially if they are substandard Ethernet cables. In this paper, four Ethernet cables were subjected to three coiling and uncoiling tests to represent installation handling stress. The impedance profiles of the four cables across their lengths were measured for the three handling stress test conducted. The computation of the transmission line parameters of the Ethernet cables using measured impedance profiles was implemented with the aid of Matrix Laboratory (MATLAB). The outcome of the research showed that the method presented will be very useful to cable installers and contractors in making objective decisions in the choice of cables for deployment.Item Open Access Electromagnetic Design and Analysis in Electrical Power Conversion and Usage(MDPI, 2023-02-24) Duffy, Alistair; Zhang, GangItem Metadata only Electromagnetic time reversal for online partial discharge location in power cables: Influence of interfering reflections from grid components(Institution of Engineering and Technology (IET), 2024-04-16) Ragusa, Antonella; Wouters, Peter A. A. F.; Sasse, Hugh; Duffy, Alistair; Rachidi, Farhad; Rubinstein, MarcosIn online single-sided partial discharge (PD) location, the measured PD reflection patterns are affected by the characteristics of all the components of the associated power network. This paper analyses the performance of a PD location method based on electromagnetic time reversal (EMTR) theory, when interfering reflections contribute to the transient signals emitted by the PD event. The topology analysed is formed from a ring main unit (RMU) in a medium voltage grid with mixed cross-linked polyethylene and paper-insulated lead-covered (PILC) cable sections. The PD reflection patterns, observed at the RMU, are disturbed by the reflections coming from the impedance discontinuities of the circuit and by the reflections coming from the cable ends of the PILC cables connected to the RMU. The simulated configuration is chosen such that classical location techniques tend to fail due to overlapping peaks and other signal distortion. This is because the classic techniques are based on identifying individual reflection peaks from which the PD source can be determined via differences in time of arrival. The numerical investigation shows that the accuracy of the EMTR-based location method is robust against these effects, achieving a PD localisation with an error less than the 0.1%. The results also show that the EMTR-based method can localise PDs using a PD monitoring point located somewhere along the network and not necessarily at the line termination.Item Metadata only Electromagnetic Time Reversal Method to Locate Partial Discharges in Power Networks Using 1D TLM Modelling(IEEE, 2020-10-20) Ragusa, Antonella; Sasse, Hugh; Duffy, Alistair; Rachidi, Farhad; Rubinstein, MarcosThis letter sets out to describe the first results of the design process that will lead to a new on-line partial discharge location method based on Electromagnetic Time Reversal theory and using the Transmission Line-Matrix method. A description of the basic steps of the method under design is given together with the modeling procedure used to describe time inverted signal propagation. Finally, the ability of the method to locate partial discharges on power cables both using two observation points and a single observation point is proved in simulation.Item Open Access Electromagnetic Time Reversal to Locate Partial Discharges in Power Networks with Inhomogeneous cables using the Transmission Line Matrix Method(CIGRE Science & Engineering (CSE), 2021-06-01) Ragusa, Antonella; Sasse, Hugh; Duffy, AlistairThis paper describes a method for the on-line location of partial discharges (PD) in power networks based on the electromagnetic time reversal (EMTR) theory. PDs are localized electrical discharges that partially bridge the insulation between conductors and that start in cable insulation defects. Since the insulation degradation is often caused by PD, PD is regarded as a symptom of insulation degradation and on-line PD location is considered the most suitable monitoring method of network integrity assessment to prevent faults and improve network resilience. The proposed method, reversing in time the measured PD signals, refocuses them to their source allowing the location of PD site. The method uses the Transmission Line Matrix modelling approach to solve the backward propagation equations. In this paper, the effectiveness of the EMTR-based method to locate PDs in inhomogeneous power lines, using only one measurement point at a line end, is investigated and proved in simulation.Item Open Access EMI Risk Estimation for System-Level Functions Using Probabilistic Graphical Models(IEEE, 2021-10-19) Devaraj, Lokesh; Ruddle, Alastair; Duffy, AlistairIn general, the functions provided by complex systems often involve multiple sub-systems and components that are functionally dependent on each other. The dependency could be to receive power, control signals, input data, memory storage, feedback etc. With the increasing use of electronic systems to perform critical functions, the potential for malfunctions due to electromagnetic interference need to be identified and mitigated. Hence, a risk analysis, estimating the likelihood and severity of electromagnetic interference effects, is desirable from the very early stages of system development. In this paper, the use of probabilistic graphical models for estimating the likelihood of electromagnetic disturbances causing system malfunctions with various degrees of severity is demonstrated using a very simple case study. Statistical data are synthesised to illustrate the construction of conditional probability distribution tables for a Bayesian Network system model. Factorization and inference techniques are then applied to demonstrate the formulation and answer of queries that could be of value during system risk assessment.Item Open Access Knowledge-Based Approach for System Level Electromagnetic Safety Analysis(2021-09-19) Devaraj, Lokesh; Ruddle, Alastair; Khan, Qazi Mashaal; Duffy, AlistairRoad vehicles and similarly complex systems are constructed by integrating many subsystems and components that are sourced from a large number of suppliers. This process may lead to the emergence of possible system-level safety issues, some of which could be caused by external or internal electromagnetic interference. Assurance of safety by demonstrating compliance with standard tests is becoming increasingly challenging as system complexity rises. This is due to the costs and practical limitations of both component and system-level electromagnetic compatibility testing. Hence, there is a need for additional methods to help estimate the likelihood of electromagnetic interference risks associated with such systems. Probabilistic graphical models, such as Bayesian and Markov networks, are able to provide a better visualization of various features and their relationships in a single graphical structure. Moreover, using template models, a general-purpose representation for various integrated components of a system can be developed for collective inference. Using such methods, this paper proposes a knowledge-based approach to assist risk management in system-level electromagnetic engineering. The purpose of using a knowledge-based approach is to be able to undertake safety risk analyses during the early stages of design, when many factors (e.g. internal, and external electromagnetic interference levels, physical location of the component) remain uncertain.Item Open Access A new method to localize partial discharges on power cables using time reversal and TLM numerical method – A review(2021-10-06) Ragusa, Antonella; Sasse, Hugh G.; Duffy, AlistairInsulation deterioration is often caused by partial discharge (PD) events. The adoption of on-line PD location methods is one of the most suitable methods to perform the power networks condition monitoring to improve their resilience and to guarantee electricity supply security. This paper reviews the results obtained in the design process of a new on-line PD location method based on the use of the electromagnetic time reversal (EMTR) theory and the Transmission Line Matrix (TLM) numerical method. Building on the work previously presented at the IWCS, where the method had been presented using two observation points, this paper shows further progress in this research and as a proof of its effectiveness, shows its ability in locating PDs using only one observation point. The procedure of the method is briefly described and its performance that overcomes the shortcomings of the traditional PD location methods are summarized. Finally, future related activities are described.Item Embargo Practical Evaluation of Electromagnetic Time Reversal to Locate Partial Discharges on Power Networks in the Presence of Noise(IEEE, 2022-09-26) Ragusa, Antonella; Sasse, Hugh; Duffy, AlistairThe paper proposes an analysis of the performance of a new method to localize Partial Discharges (PDs) on power cables under noisy conditions. The new method is based on the use of the Electromagnetic Time Reversal (EMTR) theory and the ransmission Line Matrix (TLM) numerical method. The investigations have been carried out in a voltage reduced experimental set up, using a RG223 coaxial cable. The effectiveness of the EMTR-based method has been evaluated with different noise levels injected into the cable in order to determine how the method works under noisy conditions. The experimental results have shown that the EMTR method is able to localize PD source with an error that is always less than 1%. Averaging is used over several PD signal recordings at the observation point when the reflected signal is hidden by the noise.Item Open Access Reducing the Functional Safety Risks (and other risks) that can be caused by EMI – new IEEE Standard 1848(IEEE, 2020-06-10) Armstrong, Keith; Duffy, AlistairWhen Functional Safety risks must be reduced throughout the lifecycle of an electronic system, the acceptable levels for the risks that could be caused by electromagnetic disturbances or electromagnetic interference (EMI) are about 100dB lower than normal for immunity tests. This means that these risks are in-capable of being verified or validated by immunity testing only. At the time of writing, IEEE Standard 1848 is well on its way towards being published. This is a new type of IEEE Standard, and will provide requirements and guidance on the use of well-proven techniques and measures to help ensure that neither electromagnetic disturbances nor EMI will be the cause of un-acceptable Functional Safety risks. It’s techniques and measures cover: project management; system design; operational design of hardware and software; verification, and validation. They also cover assem-bly/installation; commissioning, maintenance; upgrade; refur-bishment, and disposal. Although intended for reducing Functional Safety risks, the techniques and measures in IEEE 1848 can also be used for reducing any quantifiable risks (mission-critical, reputational, financial, etc.) that could be caused by electromagnetic disturb-ances or EMI.Item Open Access Risk Assessment Approach for EM Resilience in Complex Systems Using Bayesian Networks(IEEE, 2021-08) Devaraj, Lokesh; Ruddle, Alastair; Duffy, Alistair; Martin, AnthonyCurrent trends in the automotive industry are reshaping the architectures and electromagnetic characteristics of road vehicles. Increasing electrification and connectivity are enabling considerable packaging flexibility and leading to radically different electromagnetic environments. At the same time, increasing automation of driving functions will require unprecedented levels of system dependability. However, existing EMC engineering processes were developed in a very different world of low system complexity and incremental technological development. In order to adapt to rising system complexity and the increasingly rapid pace of technological change, it is considered that a more agile risk-based approach is better suited to ensure the electromagnetic resilience of future vehicles and other complex systems. This paper outlines a Bayesian network approach that allows the combination of both technical and nontechnical aspects in assessing the likelihood of issues that could lead to system-level risks. This approach could be used from the earliest stages of product development, where the detailed information required to undertake detailed risk assessment is generally unavailable.Item Metadata only Simulation-based Reactive Scheduling for the Concrete Delivery Problem Using Actual Data and Delivery Site Constraints(2019-05) Kang, Parminder Singh; Duffy, Alistair; Samarghandi, HamedConstruction project control requires reliable delivery schedules. The delivery schedule decisions examine the information available regarding material, equipment, concrete quality controls, delivery times, construction site delays and other external factors such as congestion and traffic conditions. This paper investigates a sector-specific problem for a non-fixed construction project (highway sector) to generate a daily concrete delivery schedule. The objectives of the delivery schedule are to maximize daily throughput and minimize queues at the construction site by considering constraints from the concrete supplier and construction site — comparison of Simulation-based reactive schedule with current manual practice in industry demonstrates 13% throughput improvement by having deliveries just-in-time.Item Open Access Step Frequency TR-MUSIC for Soft Fault Detection and Location in Coaxial Cable(IEEE, 2023-03-27) He, Xin; Wang, Lixin; Yang, Dazhi; Chang, Kaixing; Duffy, Alistair; Zhang, GangSoft faults in cables may trigger short circuits and open circuits in time, in that, they ought to be detected and thus eliminated at an earliest possible stage, as to ensure safe and stable operation of the cables. A method called the time-reversal multiple signal classification (TR-MUSIC) had been proposed in the literature, which has been demonstrated to be an effective technique for locating soft faults in cables, owing to its high resolution and excellent noise robustness. However, traditional TR-MUSIC relies on a vector network analyzer for measuring the scattering matrix of cables, which adds cost and complexity to its implementation. In this regard, a new way of acquiring the desired scattering parameters is herein proposed. An arbitrary function generator is used to inject incident signals into the cable under test, and an oscilloscope is used to collect the reflected signals. After post-processing, the phase of scattering parameters can be obtained. There's another key issue in the image of the detection results, ghost traces caused by the periodicity of Green's function severely impact the vision saliency of the actual fault location, which limits the performance of the fault location. A step frequency variant of TR-MUSIC has been proposed, therefore, to mitigate ghost traces. Experimental results show that the fault location error of the proposed approach is smaller than 0.33% for a 51-m long coaxial cable. Moreover, in the case of introducing noise, the proposed approach can operate in situations with signal-to-noise ratios as low as dB.Item Open Access System Level Risk Analysis for Immunity in Automotive Functional Safety Analyses(IEEE, 2020-09-23) Devaraj, Lokesh; Ruddle, Alastair; Duffy, Alistair; Martin, A.J.M.At present, automotive functional safety and EMC engineering are largely carried out independently. Current EMC regulations aim to avoid unwanted disturbances by setting appropriate immunity threat levels and emission limits. However, with the rapidly evolving technology and complexity of automotive systems, the limits identified in standards may no longer be appropriate. Hence the identification and assessment of EMC-related risks are becoming increasingly necessary. This paper outlines the tools used to support risk analysis for functional safety and presents initial proposals for a graphical method to better align the analysis of EMC risks and functional safety.