Noureddine Harid | Khalifa University (original) (raw)

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Papers by Noureddine Harid

Despite the advantages of polymeric insulators over the conventional glass and porcelain outdoor ... more Despite the advantages of polymeric insulators over the conventional glass and porcelain outdoor insulators, concerns remain about their performance in contaminated environments. In-depth understanding of the problems associated with pollution such as flashover and ageing process requires better determination of electric field strength and its profile over the polymeric surface. This paper investigates the use of a new dynamic pollution model to compute the electric field distribution along the leakage path. The study is performed under wet weather conditions of fog and light rain, which in practice are classified based on wetting and drying action. Nonlinear field-dependent conductivity with simplified modelling assumptions is proposed to characterise the electrical properties of the pollution model. An 11kV polymeric insulator is considered in this study, and the modelling and computation is performed using a Finite Element Method (FEM) package. Comparative field studies show that...

Line uprating offers excellent opportunities for increasing substantially the power transfer capa... more Line uprating offers excellent opportunities for increasing substantially the power transfer capability over existing routes. In this paper, a case study examining the opportunities for uprating of an operational 275kV transmission line using L3 tower-type is presented. The study involved examination of national and international standards for insulation coordination and the infrastructure-stress studies were carried out using the ‘Power Line Systems Computer Aided Design and Drafting’ (PLS -CADD) software. In this way, the transmission line insulation levels, structure strength and electrical clearances were computed, and a proposal is presented for uprating the 275kV line to 400kV using the same route and existing L3 towers. The design calculations revealed that a special insulator with extended creepage length and a low sag conductor would be required if the same tower is to be used without introducing structural modifications.

2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE), 2018

XLPE (Cross-linked polyethylene) samples were subjected to high voltage AC in a plane-plane confi... more XLPE (Cross-linked polyethylene) samples were subjected to high voltage AC in a plane-plane configuration and the voltage was increased to a level such that discharge was observed across the surface of the test sample for durations up to 10hrs. Selected stressed samples together with virgin samples from the same manufactured batch were tested using NMR (Nuclear Magnetic Resonance) spectroscopy. Specifically, 1H NMR spin-lattice (T1) and spin-spin (T2) relaxation time measurements were employed to examine potential changes in the chemical bonding of undamaged and damaged XLPE samples. Preliminary data show that there may be a moderate increase in the T1 and T2 values of the damaged samples in comparison to the undamaged ones. This raises the possibility that NMR can be a useful additional experimental tool in characterizing material degradation.

Sulphur hexafluoride (SF 6 ) has widely been used as an insulator in gas-insulated switchgear (GI... more Sulphur hexafluoride (SF 6 ) has widely been used as an insulator in gas-insulated switchgear (GIS) applications. But due to the fact that it is a greenhouse gas, many researchers have been trying to find alternative solutions for it. Furthermore, SF 6 produces highly toxic and corrosive substances when it is subjected to electrical discharges. Trifluoroiodomethane (CF 3 I) has recently been regarded as a candidate for replacing SF 6 . CF 3 I has been used as a fire suppressor and now many investigations have been carried out throughout the world to assess its capability in high voltage applications. This paper surveys this previous work and identifies some of the properties which are relevant to high voltage applications.

Safety assessment of earthing systems of high voltage installations by national and international... more Safety assessment of earthing systems of high voltage installations by national and international standards are under consideration by international technical working groups. Depending on the selected value of parameters, one standard may be either more or less conservative compared with another. IEC and CENELEC standards for design of earthing systems of ac substations are still based on the concept of satisfying safety under a defined set of worst-case conditions. Yet, in the U.K. and elsewhere, progress has been made to implement forms of risk assessment in earthing applications that provide a measure of individual risk. This paper provides a review of risk assessment processes applied to earthing system safety assessment with particular emphasis on the tolerability of risk framework. Here, a description of risk assessment, both quantitative and qualitative, is provided based on the UK health and safety approach. This framework describes good practice and the determination of con...

Electric Power Systems Research, 2013

ABSTRACT Field experiments and computer simulations of two sectionalized horizontal earth electro... more ABSTRACT Field experiments and computer simulations of two sectionalized horizontal earth electrodes are presented. The electrodes were energized using various voltage sources (dc, and transients of different shapes), and measurements of current and voltage magnitudes along the length of the electrode were examined. Furthermore, by incrementally increasing the length of the test electrodes, the effective length of the earth electrodes was determined experimentally. The experimental and simulation results show reasonably close agreement which gives confidence in predicting the effective length. A new method is proposed to increase the effective length of the horizontal earth electrode by installing an additional insulated parallel conductor which is bonded to the horizontal electrode at points along its length. Such insulated conductor allows current to be distributed further away from the injection point without high leakage as would occur with standard horizontal electrodes buried in the ground. The results show that the current and voltage distributions are modified such that a greater length of buried conductor is utilized and that this contributes to an additional reduction in the earth impedance, and hence the earth potential rise at the point of current injection. The effect of the proposed technique is simulated on a practical wind turbine earthing design, and shows significant gains.

In this work, a method is proposed for the calculation of the electromagnetic field radiated by a... more In this work, a method is proposed for the calculation of the electromagnetic field radiated by a grounding system in a semi-infinite dissipative medium subjected to a current excitation generated by the lightning strike. The assessment of the induced current distribution on the grounding system due to a transient excitation is obtained by solving Pocklington's equation using the method of moments. A new method for the calculation of the transient electromagnetic field following the injection of a lightning current or short circuit is also developed. This method is based on the concept of the hertzian dipoles and the asymptotic expansion of a single dipole. A MATLAB computer program has been developed for the determination of the induced currents. The program is validated by comparing its results with those obtained with the commercial software NEC 4.

Science, Measurement and Technology, …, 1991

... To study the effect of the impulse front duration, a statistical study of the corona charge f... more ... To study the effect of the impulse front duration, a statistical study of the corona charge flow ... a high-voltage coaxial cylinder of 581 mm diameter which was suitably profiled to prevent endeffects. ... The effect of voltage amplitude on the time to first corona inception is shown in Fig. ...

In this paper, an algorithm is proposed to investigate the improvement in HV network reliability ... more In this paper, an algorithm is proposed to investigate the improvement in HV network reliability when the number and location of Remotely Operable Switches (ROS) is changed. Specifically, the Particle Swarm Optimisation PSO is employed to identify; (i) optimal placement of remotely operable protective devices and (ii) the optimal sequence of reconfiguration and restoration of the supply based on a given deployed set of switches. The reliability of the network is measured by calculating the possible number of customers restored post outage, considering both upstream and downstream restorations. In the selection of optimal switching sequences, the voltage and current constraints are also used to ensure that the identified restoration is viable. A successfully developed PSO based algorithm is described and applied to an 11 kV urban distribution network comprising 162 nodes and 31 feeders. Successful results were achieved with optimal number of ROS and reconfigurations have been made wi...

Despite the advantages of polymeric insulators over the conventional glass and porcelain outdoor ... more Despite the advantages of polymeric insulators over the conventional glass and porcelain outdoor insulators, concerns remain about their performance in contaminated environments. In-depth understanding of the problems associated with pollution such as flashover and ageing process requires better determination of electric field strength and its profile over the polymeric surface. This paper investigates the use of a new dynamic pollution model to compute the electric field distribution along the leakage path. The study is performed under wet weather conditions of fog and light rain, which in practice are classified based on wetting and drying action. Nonlinear field-dependent conductivity with simplified modelling assumptions is proposed to characterise the electrical properties of the pollution model. An 11kV polymeric insulator is considered in this study, and the modelling and computation is performed using a Finite Element Method (FEM) package. Comparative field studies show that...

Line uprating offers excellent opportunities for increasing substantially the power transfer capa... more Line uprating offers excellent opportunities for increasing substantially the power transfer capability over existing routes. In this paper, a case study examining the opportunities for uprating of an operational 275kV transmission line using L3 tower-type is presented. The study involved examination of national and international standards for insulation coordination and the infrastructure-stress studies were carried out using the ‘Power Line Systems Computer Aided Design and Drafting’ (PLS -CADD) software. In this way, the transmission line insulation levels, structure strength and electrical clearances were computed, and a proposal is presented for uprating the 275kV line to 400kV using the same route and existing L3 towers. The design calculations revealed that a special insulator with extended creepage length and a low sag conductor would be required if the same tower is to be used without introducing structural modifications.

2018 IEEE International Conference on High Voltage Engineering and Application (ICHVE), 2018

XLPE (Cross-linked polyethylene) samples were subjected to high voltage AC in a plane-plane confi... more XLPE (Cross-linked polyethylene) samples were subjected to high voltage AC in a plane-plane configuration and the voltage was increased to a level such that discharge was observed across the surface of the test sample for durations up to 10hrs. Selected stressed samples together with virgin samples from the same manufactured batch were tested using NMR (Nuclear Magnetic Resonance) spectroscopy. Specifically, 1H NMR spin-lattice (T1) and spin-spin (T2) relaxation time measurements were employed to examine potential changes in the chemical bonding of undamaged and damaged XLPE samples. Preliminary data show that there may be a moderate increase in the T1 and T2 values of the damaged samples in comparison to the undamaged ones. This raises the possibility that NMR can be a useful additional experimental tool in characterizing material degradation.

Sulphur hexafluoride (SF 6 ) has widely been used as an insulator in gas-insulated switchgear (GI... more Sulphur hexafluoride (SF 6 ) has widely been used as an insulator in gas-insulated switchgear (GIS) applications. But due to the fact that it is a greenhouse gas, many researchers have been trying to find alternative solutions for it. Furthermore, SF 6 produces highly toxic and corrosive substances when it is subjected to electrical discharges. Trifluoroiodomethane (CF 3 I) has recently been regarded as a candidate for replacing SF 6 . CF 3 I has been used as a fire suppressor and now many investigations have been carried out throughout the world to assess its capability in high voltage applications. This paper surveys this previous work and identifies some of the properties which are relevant to high voltage applications.

Safety assessment of earthing systems of high voltage installations by national and international... more Safety assessment of earthing systems of high voltage installations by national and international standards are under consideration by international technical working groups. Depending on the selected value of parameters, one standard may be either more or less conservative compared with another. IEC and CENELEC standards for design of earthing systems of ac substations are still based on the concept of satisfying safety under a defined set of worst-case conditions. Yet, in the U.K. and elsewhere, progress has been made to implement forms of risk assessment in earthing applications that provide a measure of individual risk. This paper provides a review of risk assessment processes applied to earthing system safety assessment with particular emphasis on the tolerability of risk framework. Here, a description of risk assessment, both quantitative and qualitative, is provided based on the UK health and safety approach. This framework describes good practice and the determination of con...

Electric Power Systems Research, 2013

ABSTRACT Field experiments and computer simulations of two sectionalized horizontal earth electro... more ABSTRACT Field experiments and computer simulations of two sectionalized horizontal earth electrodes are presented. The electrodes were energized using various voltage sources (dc, and transients of different shapes), and measurements of current and voltage magnitudes along the length of the electrode were examined. Furthermore, by incrementally increasing the length of the test electrodes, the effective length of the earth electrodes was determined experimentally. The experimental and simulation results show reasonably close agreement which gives confidence in predicting the effective length. A new method is proposed to increase the effective length of the horizontal earth electrode by installing an additional insulated parallel conductor which is bonded to the horizontal electrode at points along its length. Such insulated conductor allows current to be distributed further away from the injection point without high leakage as would occur with standard horizontal electrodes buried in the ground. The results show that the current and voltage distributions are modified such that a greater length of buried conductor is utilized and that this contributes to an additional reduction in the earth impedance, and hence the earth potential rise at the point of current injection. The effect of the proposed technique is simulated on a practical wind turbine earthing design, and shows significant gains.

In this work, a method is proposed for the calculation of the electromagnetic field radiated by a... more In this work, a method is proposed for the calculation of the electromagnetic field radiated by a grounding system in a semi-infinite dissipative medium subjected to a current excitation generated by the lightning strike. The assessment of the induced current distribution on the grounding system due to a transient excitation is obtained by solving Pocklington's equation using the method of moments. A new method for the calculation of the transient electromagnetic field following the injection of a lightning current or short circuit is also developed. This method is based on the concept of the hertzian dipoles and the asymptotic expansion of a single dipole. A MATLAB computer program has been developed for the determination of the induced currents. The program is validated by comparing its results with those obtained with the commercial software NEC 4.

Science, Measurement and Technology, …, 1991

... To study the effect of the impulse front duration, a statistical study of the corona charge f... more ... To study the effect of the impulse front duration, a statistical study of the corona charge flow ... a high-voltage coaxial cylinder of 581 mm diameter which was suitably profiled to prevent endeffects. ... The effect of voltage amplitude on the time to first corona inception is shown in Fig. ...

In this paper, an algorithm is proposed to investigate the improvement in HV network reliability ... more In this paper, an algorithm is proposed to investigate the improvement in HV network reliability when the number and location of Remotely Operable Switches (ROS) is changed. Specifically, the Particle Swarm Optimisation PSO is employed to identify; (i) optimal placement of remotely operable protective devices and (ii) the optimal sequence of reconfiguration and restoration of the supply based on a given deployed set of switches. The reliability of the network is measured by calculating the possible number of customers restored post outage, considering both upstream and downstream restorations. In the selection of optimal switching sequences, the voltage and current constraints are also used to ensure that the identified restoration is viable. A successfully developed PSO based algorithm is described and applied to an 11 kV urban distribution network comprising 162 nodes and 31 feeders. Successful results were achieved with optimal number of ROS and reconfigurations have been made wi...