A. Haddad

Cardiff University | CU · School of Engineering

This paper explores the influence of the maximum inter-electrode spacing in soil resistivity measurements on the one-dimensional soil modelling process. Soil equivalent models are generated based on actual measurements using a Wenner configuration. The results indicate that soil resistivity models are significantly impacted by the maximum inter-ele...

This article addresses the critical need to reduce grounding impedance for the protection of both individuals and electrical equipment under normal and faulty conditions. While numerous techniques exist for low-frequency applications, challenges arise at higher frequencies due to the inductive behavior inherent in grounding systems. The efficacy of...

This work presents a method to assess the impulse impedance of the wind turbine grounding system (WTGS) considering the adjustable lightning parameters $\alpha$ (adjusting the peak values) and $\beta$ (adjusting the risetime $T_{30}$) of the injected current representative of the first return stroke (FRS). The harmonic grounding impedance (HGI) is...

Induced voltages and currents on the de-energized circuit of a transmission line occur due to inductive and capacitive couplings related to the electromagnetic field generated by the energized side of a double-circuit transmission line. This phenomenon can produce considerably high currents and voltages that might affect the safety of workers du...

Employing correlation analysis, this investigation applied two non-destructive coupling sensors measuring the corona discharge characteristics in air compressed to 6 Bar. The study aimed to understand how harmonic contents, especially those resulting from commutation and overlap angles, affect harmonic voltage distortions. To achieve precise...

The nature of rectifier station operation can introduce harmonics into electrical systems. Understanding the impact of these harmonics on the insulation properties of gases in gas-insulated systems, particularly regarding partial discharge generation and inception voltages, is crucial in assessing SF6 alternatives. This study examined the behaviour...

This study investigated nonlinear resistive field grading material based on a ZnO microvaristor to optimize the distribution of the electric field along with a 36 kV composite bushing surface. In this work, we consider some parameters that influence nonlinear resistive field grading material properties such as different shapes of microvaristor lay...

This paper presents an improved temporal pulse sequence analysis (PSA) method for diagnosing partial discharge (PD) phenomena. The proposed method enables simultaneous high-resolution PD recognition across electrical sensors and ultra-high frequency antennae, facilitating the differentiation of defect types and the quantification of PD severity, as...

This investigation explores the phenomena of Very Fast Transient Overvoltages (VFTOs) within a 400 kV Gas Insulated Substation (GIS), emphasizing the relationship between disconnector operations, trapped charges, and GIS component configurations. Using ATP-EMTP for simulations, this study assesses VFTO phenomena in a 400 kV GIS system through simul...

Bushings are considered as one of the main components of power transformers, a key element of the transmission network. Recently, bushings with composite housings have been adopted because of their advantages over ceramic bushing, e.g., reduced weight, reduced explosive hazard and better performance under polluted conditions and under seismic activ...

The double-ended impedance-based fault location Method (DEFLM) uses the wideband frequency content of the transient generated by the fault to determine the impedance from the point of measurement to the fault. This work evaluates the use of DEFLM in integrated power system such as those in More Electric Vehicles. Two approaches have been investigat...

It is widely recognised that over-reliance on GNSS (e.g GPS) for time synchronisation represents an acute threat to modern society, and a diversity of alternatives are required to mitigate the threat of an outage. This paper proposes a GNSS alternative using time dissemination over national scale transmission or distribution networks. The method ut...

The present paper deals with new modeling to reproduce the electric discharge in the rod-plane air gap system with rubber insulating barrier under AC and impulse voltage. This model considers the randomness character of discharge evolution which is governed by the electric field. The discharges shape obtained by this model are compared with ones gi...

Abstract: This paper investigates the impact of trapped charges on Very Fast Transient Overvoltages (VFTOs) in 400 kV Gas Insulated Substations (GIS) systems. VFTOs pose significant challenges to the design, insulation coordination, and long-term reliability of GIS systems. To study the effects of trapped charges on VFTO magnitudes, the paper utili...

This paper presents a needle-to-plane test setup to simulate one typical potential defect in high voltage direct current gas insulated switchgear, and correspondingly evaluate its generated partial discharge characteristics under multi-order high voltage direct current harmonic components. An arbitrary waveform high voltage source was used to stres...

Investigation of Electric Field Distribution on Polymeric Bushing Using Non-linear Field Grading Materials

This paper examines the surface insulation performance of atmospheric gases, namely, technical air (21/79% O2/N2), nitrogen (N2), carbon dioxide (CO2) and the gas mixture of 4% fluoronitrile (C4F7N) balanced with CO2. The test configuration replicates the contact region between charged metal conductor and solid dielectric both surrounded by the gas...

Nonlinear composites made of ZnO microvaristors mixed with silicone rubber material are promising compounds for field grading and stress control in high voltage applications due to their electric field-dependent properties. A crucial aspect for the utilization of nonlinear composites is to control their nonlinear characteristics in order to fulfill...

Nonlinear composites made of ZnO microvaristors mixed with silicone rubber material are promising compounds for field grading and stress control in high voltage applications due to their electric field-dependent properties. A crucial aspect for the utilization of nonlinear composites is to control their nonlinear characteristics in order to fulfill...

Earthing systems in electrical substation should be of the highest integrity and of robust construction in order to help with the protection of equipment without endangering the health and safety of individuals. For this purpose, several parameters are described by international standards to meet earthing requirements. These parameters include not...

This paper establishes a simultaneous discharge detection experiment setup based on different physical peculiarities of the partial discharge phenomenon with two types of different coupling devices (high frequency current transformer and ultra high frequency antenna) to be ready for examining gaseous insulation degradation under AC or DC voltage. C...

Very fast transient overvoltages (VFTO) are a unique phenomenon in a GIS caused by disconnector operations. These transients have a duration measured in nanoseconds and a frequency greater than several Megahertz. This project examines the magnitudes of transient overvoltage using computer modelling of electrical networks. In the present paper, we p...

The effect of thermal aging on the electrical properties of the insulating oil used for transformers has been explored in this experimental work. In particular the dielectric dissipation factor, the resistivity and the breakdown voltage have been measured and correlated. The numerical results predicted by mathematical model and those measured in th...

A new thermal model of an insulator heat loss coefficient proves that evaporation power loss is more significant than thermal conduction to a moist environment. Consequently, the leakage current in a moist pollution layer may cause dry-band formation. Such bands are bridged and sustained by streamer discharges, which can initiate partial arcing. Cl...

The shape of the radar antenna and its lightning protection diverter strips can cause air ionization and streamer inception, which may lead to lightning attachment. In this paper, we are particularly investigating the field enhancement at the triple junction point formed by the metallic diverter strip, the radome material and the surrounding air. I...

Resin-impregnated paper (RIP) bushing has gained significant interest due to its extended application in Extra High Voltage (EHV) and Ultra High Voltage (UHV) electricity transmission systems. However, the design criterion of its overall structure, the geometry parameters of the condenser layers, and stress release devices, etc., are still not full...

A particle motion excitation and observation platform was established to physically simulate the actual online operating conditions of HVAC/HVDC GIS/GIL as well as study the capture mechanism of particle traps. Experimental results illustrated that, the collision motion style was a principal factor to affect the particle capturing capability, and t...

This paper aims to study and analyse the behaviour of ground electrodes at low and high frequency ranges. Single-layer soil is considered where several values of soil resistivity are selected. Elaborating CDEGS code, simulations are carried out to determine the grounding impedance over frequency up to ten megahertz. A parametric analysis is conduct...

Spacers for the HVDC GIS/GIL play an important role in mechanically supporting conductors and separating compartments. At the same time, their insulation performance affects the stability and safety of system operation. Design rules and knowledge specific to AC spacers do not apply to those of DC spacers. Considering the shape influence on the surf...

This paper is aimed to an overview and recent progress related to an innovative SiR polymeric designed at Cardiff University and its potential application for 400 kV overhead lines. The history of the research & development program and the recent design and manufacturing 400 kV prototypes are presented. The main laboratory results and the ongoing r...

Presentation of a paper talking about the partial discharge inception/breakdown and surface discharge inception/flashover in compressed CO2

This study highlights the heterogeneity impact of fields on the grounding system modelling and the uncertainty of soil resistivity measurements/models caused by this reason. Using Wenner method, six sounding profiles are considered over a square shape area within the same site. Test arrangements and associated results, including soil equivalent mod...

This paper deals with the measurement of earthing impedance of systems subjected to low magnitude variable-frequency currents. Measurement fundamentals are briefly discussed and some factors that can influence the results are underlined. Experimental investigations are conducted to examine the impact of certain selected factors namely, the length o...

Le polyéthylène sous sa forme basse densité (PEBD) est généralement utilisé comme isolant pour les câbles de haute et moyenne tension. En raison de ses remarquables caractéristiques électriques et mécaniques, ce matériau est largement utilisé. Cependant, sous les conditions de service, l'isolation en PEBD peut se dégrader de manière significative a...

Carbon‐fiber reinforced polymer (CFRP) composites are replacing metal alloys in aerospace structures, but they can be vulnerable to lightning strike damage if not adequately protected due to the poor electrical conductivity of the polymeric matrix. In the present work, to improve the conductivity of the CFRP, two electrically conductive epoxy formu...

In combating the threat of irreversible climate change, all sectors will need to reduce their carbon dioxide emissions and wider environmental impact. In addition, the rising cost of fuel and maintenance and the quest for continual improvement in aircraft performance has led the aviation industry to the challenge of transitioning from traditional m...

The shape of the radar antenna and its lightning protection diverter strips can cause air ionization and streamer inception, which may lead to lightning attachment. In this paper, we are particularly investigating the field enhancement at the triple junction point formed by the metallic diverter strip, the radome material and the surrounding air....

The operation of parallel surge arresters can improve energy absorption capability if the arresters are similar and are installed close to each other. However, it has been reported that any small difference in the individual V-I characteristics can lead to unbalance in current sharing. When the arresters are installed some distance away from each o...

This article introduces a complementary criterion for flashover (FOV) of polluted insulators based on the concept of equivalent impedance variation with discharge length and leakage current. An analytical electrothermal model enabling the calculation of critical FOV voltage and critical current of polluted insulators is developed using this complem...

Sulphur hexafluoride (SF6) is currently the preferred dielectric gas used in medium and high voltage power equipment. However, due to the extremely greenhouse effect by SF6, the search for alternative gas comprising a fluoro-organic gas with low environmental concern mixed with a buffer gas (N2, CO2 and O2) have received considerable attention from...

This paper proposes the use of a LoRa like chirp spread spectrum physical layer as the basis for a new Power Line Communication modulation scheme suited for low-bandwidth communication. It is shown that robust communication can be established even in channels exhibiting extreme multipath interference, impulsive noise and low SNR (-40dB), with synch...

This study investigates nonlinear resistive field grading material based on zinc oxide microvaristor to improve the distribution of the electric field along with a 52 kV composite bushing surface. In this study, there are some parameters that influence nonlinear resistive field grading material that has been proposed such as different thickness, le...

Improvement of Electric Field Distribution on 52kV Polymeric Bushing using ZnO Microvaristor

The paper aims to analyse the grounding system performance while considering Marconite coverings as a promising technique to reduce the grounding impedance under low and high frequency currents. Experimental investigations are conducted using vertical ground electrodes subjected to currents of variable frequency up to ten megahertz. Electrodes of d...

Very fast transient overvoltages (VFTO) are a unique phenomenon in a GIS caused by disconnector operations. These transients are associated with a time range in nanoseconds and frequency above several Megahertz. The project involves computer modelling of electrical networks and explores transient overvoltage magnitudes. In the present paper, we pre...

The paper deals with the aspect of soil resistivity measurement and modelling. Using Wenner configuration, a vertical survey is conducted using ABEM/Lund imaging system over a line of 240 m long. The measured results, along with the 1D and 2D equivalent models, are presented and discussed. Utilising the RESAP module of CDEGS software, different mul...

Pollution flashover occurs when soluble and nonsoluble materials cover the surface of an insulator, and this may ultimately cause a reduction in its performance. In this paper, the common type of sodium chloride (NaCl) was used as a soluble pollutant (ESDD) and kaolin as a nonsoluble pollutant (NSDD). Samples of silicone rubber (SiR) insulators wer...

Metal contaminants can distort the surface electric field of the tri-post epoxy insulator and cause serious surface charge accumulation, significantly reducing the insulation performance of the insulator under the superimposed DC and lightning impulse voltage. In this paper, an experimental platform for charge accumulation and surface flashover of...

In this article, investigations of surface discharges using an ultraviolet (UV) intensified high-speed camera system are presented, accompanied by high-frequency response and resolution current recordings. A needle-plane electrode configuration is employed for the generation of a strongly nonuniform electric field on the surface of disk-shaped insu...

This paper deals with the effects of ultraviolet (UV) light radiations on the properties of low-density polyethylene (LDPE) cable insulating materials. The aim is to evaluate changes in their physicochemical, electrical and mechanical properties after exposure to UV radiations. These changes were assessed by Fourier Attenuated Total Reflection Four...

Dynamic wireless charging (DWC), which enables charging while EVs are in motion, is an attractive charging way. However, additional installed power tracks underneath the lane bring a significant concern on its economic viability. This paper proposes a comprehensive framework to evaluate the economic viability of the DWC lane for private EVs. The in...

Numerous circuit models have been proposed to represent the electrode–electrolyte interface (EEI) impedance and bulk medium impedance of conducting media. Following a review, two suitable models are constructed to represent the behavior of conduction in electrolytes and soils, respectively. Both models incorporate a constant phase element in parall...

Soil parameter characterization and the variation of permittivity and resistivity with frequency (dispersion) and current density have been the subject of many experimental studies but significant differences in measured values are found in the literature due to different testing approaches, apparatus, and test sample composition. This article firs...

Light emissions and Schlieren structures were simultaneously observed from streamers produced by tens of kilovolts 1.2/50 μs impulses, representing the high voltage component of lightning, applied across a 4 cm air gap between a variety of electrode geometries and a ground plane in an unconfined environment. The results demonstrated that the light...

HFO1234ze(E) is an environmentally friendly SF6 substitute gas with prominent application potential. To suppress the generation of the HFO1234ze(E) solid decomposition products, which may cause great hazards to the gas–solid insulation strength, a gas mixing scheme screening method based on the reactive force field (ReaxFF) molecular dynamics (MD)...

A power decoupling control for wind power converter based on series-connected modular multilevel converter (SCMMC) and open-winding permanent magnetic synchronous generator (OW-PMSG) is proposed in this paper. The power converter based on SCMMC and OW-PMSG achieves medium voltage direct conversion and transmission and has higher dc-bus voltage comp...

The cover picture shows a gas insulated transmission line (GIL) undergoing partial discharge failure. Under such conditions, chemical reactions will occur between surface epoxy resin molecules, gas insulating medium (sulfur hexafluoride, SF6) and gas impurities (H2O, O2, etc.), resulting in insulation deterioration. The ReaxFFSFOH force field lays...

The aim of this study is the presentation of the results of an in-lab comparative study of electrical and thermal monitoring of artificially polluted, HTV-textured silicone rubber insulators, with different pollution levels. This work is a preliminary study of an in-situ monitoring of 400 kV SiR textured in a polluted environment. The results showe...