Browsing by Author "Duffy, A. P."

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    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, A. P.
    The 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.
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    3D Simulation of Partial Discharge in High Voltage Power Networks
    (IWCS Inc, 2019-10-01) Ragusa, Antonella; Sasse, Hugh G.; Duffy, A. P.
    Partial discharge (PD) events arise inside power cables due to defects of cable’s insulation material, characterized by a lower electrical breakdown strength than the surrounding dielectric material. These electrical discharges cause signals to propagate along the cable, manifesting as noise phenomena. More significantly, they contribute to insulation degradation and can produce a disruptive effect with a consequent interruption of power network operation. PD events are, therefore, one of the best ‘early warning’ indicators of insulation degradation and, for this reason, the modeling and studying of such phenomena, together with the development of on-line PDs location methods, are important topics for network integrity assessment, and to define methods to improve the power networks’ Electricity Security. This paper presents a 3D model of PD events inside a void in epoxy-resin insulation cables for High Voltage (HV) power networks. The 3D model has been developed using the High Frequency (HF) Solver of CST Studio Suite® software. PD events of a few µs duration have been modelled and analyzed. The PD behavior has been investigated using varying electrical stress. A first study of the PD signal propagation in a power network is described.
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    Accurate method for predicting return loss of communication channel.
    (IEEE, 2001) Al-Asadi, M. M.; Duffy, A. P.; Willis, A. J.; Hodge, K.
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    Analysing transient phenomena in the time domain using the Feature Selective Validation (FSV) Method
    (IEEE, 2013-02-04) Jauregui, R.; Zhang, Gang; Rojas-Mora, J.; Ventosa, O.; Silva, F.; Duffy, A. P.; Sasse, Hugh G.
    The increasing application of simulation tools to increasingly complex problems makes the use of validation tools essential to improve confidence in the veracity of those simulation results. IEEE Standard 1597.1 is the first true standard for validation of computational electromagnetic. This standard uses the Feature Selective Validation (FSV) method as the key quantification tool. However, despite its many advantages, there have been some interesting issues surrounding the validation of transients. This paper presents a new approach to the validation of a set of generally representative transient types using the Feature Selective Validation (FSV) method and shows how the previously experienced limitations can be overcome. In order to analyse the main parameters associated with transient comparison, a survey which included 20 experts was conducted. This information was used to identify the significant regions that need to be taken into account in the transient comparison. Finally, using the statistics obtained by the experts, a new solution was defined and its improvement over the existing approach demonstrated.
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    Analysis and modelling of structured wiring communication channels
    (IEEE, 2001-05-01) Al-Asadi, M. M.; Duffy, A. P.; Hodge, K.; Willis, A. J.
    The authors present equations for the calculation of the attenuation constant of both unshielded and shielded cables as a function of cable dimension, material parameters and frequency of operation. An analytical approach is given for calculating the return loss of a communication channel as a function of such parameters as impedance, length and propagation constant. A transmission-line matrix (TLM) method to assess the effects on attenuation and return loss of longitudinal variations along a structured wire cable is developed. Results are presented using both analytical and modelling approaches; these are validated against measurements.
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    Analysis of techniques to compare complex data sets.
    (Emerald, 2002) Coleby, D. E.; Duffy, A. P.
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    Analyzing Transient Phenomena in the Time Domain Using the Feature Selective Validation (FSV) Method
    (IEEE, 2013-05-24) Jauregui, R.; Zhang, G.; Rojas-Mora, J.; Ventosa, O.; Silva, F.; Duffy, A. P.; Sasse, Hugh G.
    The increasing application of simulation tools to increasingly complex problems makes the use of validation tools essential to improve confidence in the veracity of those simulation results. IEEE Standard 1597.1 is the first true standard for the validation of computational electromagnetics method. This standard uses the feature selective validation (FSV) method as the key quantification tool. However, despite its many advantages, there have been some interesting issues surrounding the validation of transients. This paper presents a new approach to the validation of a set of generally representative transient types using the FSV method and shows how the previously experienced limitations can be overcome. In order to analyze the main parameters associated with transient comparison, a survey which included 20 experts was conducted. This information was used to identify the significant regions that need to be taken into account in the transient comparison. Finally, using the statistics obtained by the experts, a new solution was defined and its
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    Antenna efficiency measurements in a reverberation chamber without the need for a reference antenna.
    (Institute of Electrical and Electronics Engineers Inc., 2008) Lee, C. S.; Duffy, A. P.; Lee, C.
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    Application of probabilistic models for multitone electromagnetic immunity analysis
    (IEEE, 2022-10-12) Devaraj, Lokesh; Khan, Qazi Mashaal; Ruddle, Alastair R.; Duffy, A. P.; Perdriau, Richard; Koohestani, Mohsen
    The operational environment of modern electronic systems may include multiple frequency electromagnetic dis- turbances. However, immunity measurements usually employ single frequency continuous waveforms (i.e. single-tones). The performance of two oscillator circuits with different topologies (one simulated and one measured) were used as case studies to in- vestigate immunity to simultaneous single-tone disturbances (i.e. multitones) using probabilistic Bayesian network models. For the multitone analysis, the noisy-OR model was first used to identify the type of causal interactions between simultaneously occurring single-tones. Probabilistic theories derived from the recursive noisy-OR model, which inherits the independence assumptions of the noisy-OR and any known causal dependence between simultaneously occurring single-tones, were then used to predict the probability of higher order multitone failures. For the two case studies, the probability of three-tone failures was estimated using the single-tone and two-tone failure probability values. An improved adaptive recursive noisy-OR model was also proposed to overcome the practical difficulties of obtaining multitone failure probabilities, from either simulations or measurements.
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    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, A. P.; Rubinstein, Marcos
    The 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.
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    Applying the FSV (Feature Selective Validation) method to the comparison of switching for Signal Integrity applications
    (IEEE, 2021) Zhang, Gang; Duffy, A. P.
    To 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.
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    Cable coupling measurements in a reverberation chamber.
    (Electronic Components Association, 2009) Duffy, A. P.; Sasse, Hugh G.; Coates, A.; Lee, C. S.; Hodge, K.
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    Challenges in developing a multidimensional feature Selective Validation implementation.
    (IEEE, 2010) Archambeault, B.; Duffy, A. P.; Sasse, Hugh G.; Li, X. K.; Scase, M. O.; Shafiullah, M.; Orlandi, A.; Di Febo, D.
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    Classification and Clustering Approaches to Understanding Customer Ordering by Customers of a Fresh Food Supplier
    (The 20th Annual Conference of The Chartered Institute of Logistics & Transport, Logistics Research Network (LRN), Derby, UK, 2015-09-11) Clement, Ross; Kang, Parminder Singh; Duffy, A. P.; Hopewell, Ashley
    Purpose: This paper looks at characterization of B2B customers of a fresh food wholesale company supplying SME clients in terms of their weekly orders of a variety of fresh products. Customers whose orders can be predicted (days of the week order is placed, size of order) can easily be supplied without risk of waste due to the wholesaler ordering stock that is not sold to customers before it must be disposed of. Greater understanding of customer order patterns is necessary to improve demand prediction and reduce waste. Research Approach: Extensive real-world data from a fresh food wholesaler has been analysed in bulk. Customers’ weekly orders have been classified into one of nine classes depending on how each week’s order compares to the previous week. Equal order amounts on the same day (or days) of the week as the previous week are the most predictable class. Varying order amounts for orders placed on different days of the week are a much less predictable class. Other classes represent customers who either cease ordering after having made previous orders, or who place an order after not ordering in previous weeks. K-means clustering has also been used to extract clusters of customers showing similar ordering patterns from the customer base. These functions have been integrated into a data visualization tool which displays the clusters in terms of the frequency of occurrence of order classes, and their standard deviation within the clusters.
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    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, A. P.
    Electromagnetic 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.
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    Comparison of 3-dimensional datasets by using the generalized n-dimensional (n-D) Feature Selective Validation (FSV) technique
    (IEEE, 2016-09-28) Zhang, Gang; Orlandi, A.; Duffy, A. P.; Wang, Lixin
    Automatic methods to evaluate the validity of computational electromagnetics computer modeling and simulations have widespread applications. The Feature Selective Validation method is a heuristic technique which has been shown to give broad agreement with visual assessment for 1-dimensional data. As a heuristic technique, extending the dimensionality is an important target for the improvement and development of FSV. One of the major challenges in the development of n-dimensional FSV is the difficulty of obtaining visual assessment results, since the visual comparison of three and higher dimensional data is difficult or even impossible. This paper formulates the comparison of 3-dimensional data based on an established generalized n-dimensional FSV approach. The performance of the approach is investigated by means of the LIVE Video Quality Database which provides subjective scores of 150 distorted videos. A statistical evaluation of the relative performance of FSV and other publicly available full-reference Video Quality Assessment algorithms is presented. Further, parameter tuning is performed to improve the agreement of 3-dimensional FSV results and subjective scores. The proposed approach is finally applied to the self-referenced validation of an electromagnetic simulation model to identify and locate the continuous variation of electric field within a region of space.