The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform
A Haddad - One of the best experts on this subject based on the ideXlab platform.
-
a technique to increase the effective length of horizontal Earth Electrodes and its application to a practical Earth Electrode system
Asia-Pacific International Conference on Lightning, 2011Co-Authors: A Elmghairbi, M Ahmeda, N Harid, Huw Griffiths, A HaddadAbstract:The ability of a horizontal Earth Electrode in reducing Earth potential rise is limited because, beyond a certain length known as the effective length, no further reduction is obtained. In this paper, field experiments and computer simulations of a horizontal Earth Electrode is presented. The Electrode was energised using different sources (dc, variable frequency ac and transients of different shapes), and current and voltage distributions along the length of the Electrode were examined. Furthermore, by incrementally increasing the length of the test Electrode, the effective length of the Earth Electrode was determined. The experimental and simulation results show reasonably close agreement and also that quite good prediction of the effective length is possible. A new proposed method to increase the effective length of the horizontal Earth Electrode was investigated by installing an additional insulated parallel conductor which is bonded to the horizontal Electrode at points along its length. The results show that the current and voltage distributions are changed such that a greater length of buried conductor is utilised and that this contributes to an additional reduction in the Earth impedance, and hence the Earth potential rise at the point of current injection. Preliminary computer simulations show how this technique can also be extended to a practical Earthing system for wind turbines with good effect.
-
current and voltage distribution in a horizontal Earth Electrode under impulse conditions
International Universities Power Engineering Conference, 2009Co-Authors: M Ahmeda, N Harid, Huw Griffiths, N Ullah, A HaddadAbstract:In this paper, the behaviour of a horizontal Electrode under impulse conditions is investigated experimentally at the Cardiff University outdoor Earthing test facility. The test Electrode consists of 88.5m long copper conductor buried to a depth of 30cm, and is divided into sections with test pits located along the Electrode to enable access for voltage and current measurements along its length. A test circuit is established using an auxiliary current Electrode, and a low voltage impulse generator is used to inject current of different magnitudes and shapes into the test Electrode. The effect of current injection location, Electrode length and current rise time is quantified on the current and Earth potential rise (EPR) distribution along the Electrode. The measured voltage and current signals were analysed at various points on the Electrode to determine the effective length. Good agreement between measured and computed values was obtained. Based on an analysis of the results, the effective length of a horizontal Electrode under the particular test conditions was determined and good agreement between measured and computed values was obtained.
Udayakanthi M.v.p.g. - One of the best experts on this subject based on the ideXlab platform.
-
Identification of causes of distribution transformer failures and introduction of measures to minimize failures
2014Co-Authors: Udayakanthi M.v.p.g.Abstract:Distribution Transformers are costly and critical equipments in electricity distribution network. The Ceylon Electricity Board (CEB) has nearly 24,500 number of distribution transformers installed island wide which are connected to 11kV or 33kV Medium Voltage (MV) networks to meet the present power demand of consumers. Failure of a distribution transformer results to interruption of power supply to the consumers and involve high expenditure in repair or replacement of transformer. Hence protection of distribution transformer is very important. Transformer failure rate of the CEB is nearly 2.5% where internationally acceptable level is less than 2%. When a Distribution Transformer is failed, it is replaced with a new transformer, but there is no proper method established by the CEB to analyze the cause of failure. A detailed investigation of failed transformer is vital important to understanding the actual failure scenario and prevent further incidents. The objective of the study was to identify main causes of distribution transformer failures and propose measures to minimize those failures. This thesis presents the CEB distribution substation installation practices and practical situation of distribution substations which would be the causes for failures. Detail investigation procedure for failed transformers was established in order to find out actual cause for each transformer failure. Through the literature review, different failure modes were identified for each transformer component and common transformer failure causes are lightning, short circuit faults in network, aging, overloading, oil leaks, loose connections and bad workmanship. Failed transformers during the year 2011 were inspected in order find the root causes for failures. It was observed that lightning and overloading are the major causes for transformer failures in Southern Province. It was observed that 28% of transformer failures are due to lightning and 25% are due to overloading. Onsite investigations were carried out and failed transformers were opened whenever necessary to identify the exact causes for failures. Several tests were done before opening failed transformers such as insulation resistant test, polarization index test, ratio test and LV short circuit test. To minimize transformer failures, several measures were proposed. Maintaining the surge arrestor Earth Electrode resistance less than 10Ω, replacing of faulty surge arrestors, installation of LV surge arrestors, proper fuse selection, balancing of loads, and proper crimping of lugs are few recommendations. It is strictly recommended to train the field staff to follow the CEB construction standards of distribution substations when constructing as well as doing operation and maintenance works
M Ahmeda - One of the best experts on this subject based on the ideXlab platform.
-
a technique to increase the effective length of horizontal Earth Electrodes and its application to a practical Earth Electrode system
Asia-Pacific International Conference on Lightning, 2011Co-Authors: A Elmghairbi, M Ahmeda, N Harid, Huw Griffiths, A HaddadAbstract:The ability of a horizontal Earth Electrode in reducing Earth potential rise is limited because, beyond a certain length known as the effective length, no further reduction is obtained. In this paper, field experiments and computer simulations of a horizontal Earth Electrode is presented. The Electrode was energised using different sources (dc, variable frequency ac and transients of different shapes), and current and voltage distributions along the length of the Electrode were examined. Furthermore, by incrementally increasing the length of the test Electrode, the effective length of the Earth Electrode was determined. The experimental and simulation results show reasonably close agreement and also that quite good prediction of the effective length is possible. A new proposed method to increase the effective length of the horizontal Earth Electrode was investigated by installing an additional insulated parallel conductor which is bonded to the horizontal Electrode at points along its length. The results show that the current and voltage distributions are changed such that a greater length of buried conductor is utilised and that this contributes to an additional reduction in the Earth impedance, and hence the Earth potential rise at the point of current injection. Preliminary computer simulations show how this technique can also be extended to a practical Earthing system for wind turbines with good effect.
-
current and voltage distribution in a horizontal Earth Electrode under impulse conditions
International Universities Power Engineering Conference, 2009Co-Authors: M Ahmeda, N Harid, Huw Griffiths, N Ullah, A HaddadAbstract:In this paper, the behaviour of a horizontal Electrode under impulse conditions is investigated experimentally at the Cardiff University outdoor Earthing test facility. The test Electrode consists of 88.5m long copper conductor buried to a depth of 30cm, and is divided into sections with test pits located along the Electrode to enable access for voltage and current measurements along its length. A test circuit is established using an auxiliary current Electrode, and a low voltage impulse generator is used to inject current of different magnitudes and shapes into the test Electrode. The effect of current injection location, Electrode length and current rise time is quantified on the current and Earth potential rise (EPR) distribution along the Electrode. The measured voltage and current signals were analysed at various points on the Electrode to determine the effective length. Good agreement between measured and computed values was obtained. Based on an analysis of the results, the effective length of a horizontal Electrode under the particular test conditions was determined and good agreement between measured and computed values was obtained.
Abanmi Abdulrahma - One of the best experts on this subject based on the ideXlab platform.
-
Influence of Soil Conductivity and Rod-to-Earth Gaps on Lightning Breakdown Voltage and Peak Current of Rod-to-Plane Air Gaps
'Medwell Publications', 2019Co-Authors: Khaled Usama, Eroual Abderrahmane, Alissa Salma, Aldraimli Oma, Abanmi AbdulrahmaAbstract:International audienceThis study deals with the influence of soil conductivity and a rod-to-Earth Electrode gap on lightning impulse voltages. Two types of soils are considered: homogeneous and non-homogeneous/heterogeneous. The heterogeneous soil consists of a metallic plate in contact with a parallelepiped tank filled with water or wetted sand of different conductivities. It is shown that, for homogeneous Earth, the U50 decreases when 50% increasing the soil conductivity and the Electrodes gap decreases. For heterogeneous soil configuration and a given distance from the HV Electrode to the metallic Electrode, the U50 is higher for lower conductivities of 50% homogeneous soil
K Rama - One of the best experts on this subject based on the ideXlab platform.
-
performance of Earthing systems for different Earth Electrode configurations
IEEE Transactions on Industry Applications, 2015Co-Authors: Mohamed Shahriman Mohamed Yunus, Nkwa Agbo Etobi, K RamaAbstract:Changes of behavior of Earthing systems under high impulse conditions from its steady-state conditions have been found to occur in many studies. There are many factors that are thought to cause these changes. However, little studies so far have been conducted on the effects of Earth Electrode dimensions and configurations, particularly at field sites. This paper is to present and discuss the results of field site study on the performance of Earthing systems of different configurations and dimensions.
