George Eduful - Academia.edu (original) (raw)

Papers by George Eduful

Lecture notes in electrical engineering, Sep 28, 2022

2021 IEEE 8th International Conference on Adaptive Science and Technology (ICAST), 2021

Pole-Mounted-Transformer (PMT) failures present a major threat to the Electricity Company of Ghan... more Pole-Mounted-Transformer (PMT) failures present a major threat to the Electricity Company of Ghana (ECG). These failures have been observed to occur frequently during thunder and lightning activities, raising strong suspicion that ECG’s existing pole mounted transformer protection scheme is inadequate. Over the years, the company has used and relied on the protection scheme that separates the primary surge arrester’s grounding from the low voltage neutral terminal of the pole mounted transformer. Unfortunately, literature on the subject is equally inconclusive . Whilst certain schools of thoughts encourage the interconnection of arrester grounding and LV neutral grounding, some codes do not allow it. In this study MATLAB Simulink is used to evaluate the effectiveness of the existing protection scheme adopted by the Electricity Company of Ghana. It was found that separating the HV grounding from the LV neutral grounding makes the transformer more vulnerable to lightning-induced overvoltage. The study recommends alternative solutions to deal with the problem.

World Academy of Science, Engineering and Technology, International Journal of Energy and Power Engineering, 2015

American Journal of Electrical Power and Energy Systems, 2019

Distribution transformers are generally provided with advanced control measures that ensure their... more Distribution transformers are generally provided with advanced control measures that ensure their operation and safety at a high reliability because their failure usually leads to long power outage, increase maintenance cost and unreliable provision of electricity to customers. Despite the protection measures that accompany a distribution transformer, there is still a need to provide extra remote monitoring systems to increase the reliability of operation and the confidence of instantaneous fault reporting. This paper deals with the design and construction of automatic monitoring system for power transformer parameters. An Arduino board coupled with XBEE module were programmed to enable the monitoring of voltage, current and temperature on a typical power transformer. The system was implemented and tested successfully. Results showed that the voltage versus temperature as well as current versus voltage characteristic obtained, were closed to datasheet specifications and therefore confirming the reliability of the proposed design. This system is therefore recommended as an additional protection that should be added to Power Transformers.

This paper presents a technique applied during the conversion of an existing Low Voltage Distribu... more This paper presents a technique applied during the conversion of an existing Low Voltage Distribution System (LVDS) into High Voltage Distribution System (HVDS) in radial networks. HVDS optimization is demonstrated using linear programming techniques in MATLAB optimization tool box. A test application results explain the methodology. The optimization technique proposed estimates the optimal number of unit transformers in the HVDS. This procedure is effective for converting the bulk transformer in the LVDS into an equivalent population of unit transformers in the HVDS. The benefit of the conversion technique is the minimization of transformer no-load losses. As a result, the economy of distribution transformers is improved by savings in operational cost.

2012 IEEE 4th International Conference on Adaptive Science & Technology (ICAST), 2012

A failure condition known as burndown and surface tracking of covered conductor insulating materi... more A failure condition known as burndown and surface tracking of covered conductor insulating material appears to be restricting the widespread use of covered conductors in Ghana. The paper identifies specific problems militating against the use of covered conductors and reviews international experience on the subject with the aim of developing a performance system specification for covered conductor use in Ghana. The paper also discusses advances in protection methods for detecting downed covered conductors and recommends effective protection scheme that must go with the adoption of covered conductors.

In this paper, two major international standards on harmonic emissions in power systems have been... more In this paper, two major international standards on harmonic emissions in power systems have been reviewed. The purpose is to help utility companies and stakeholders take informed decision regarding the safe limit of harmonic emissions and decide on which standard to adopt. The paper describes the principles underlying the original intent of PCC and clarifies some difficulties in relation to application of the standards. It is shown that location of PCC can be selected based on the method of power distribution system.

Based on response curves derived from field measurements, optimum number of vertical ground elect... more Based on response curves derived from field measurements, optimum number of vertical ground electrodes for grounding electrical installation is determined. On sites where the optimum number of the electrodes cannot reach a target ground resistance, a ‘critical resistance area concept’ with conductive backfills is used. In this study, efficiencies of local conductive backfills for reducing ground resistance are investigated. Results show that application of tyre ashes as a conductive backfills lowers ground resistance to over 80%. It is also shown that the most favourable benefit in the ground resistance improvement is to limit the backfill to four electrodes.

Triplen harmonic currents are becoming major concern in the Electricity Company of Ghana (ECG) di... more Triplen harmonic currents are becoming major concern in the Electricity Company of Ghana (ECG) distribution system. Significant levels of triplen harmonic currents generate heats, increase system losses and reduce the economic life spans of distribution transformers. In this paper, the performance of three harmonic suppressors in the control of harmonic emission levels in three ECG’s distribution transformer substations have been investigated. Harmonic parameters monitored include, harmonic currents, Total Harmonic Distortions (THD) and harmonic energy losses. Results show that the neutral blocking harmonic filters can reduce harmonic current in neutral conductors by 88% and consequently decrease harmonic energy loss by 97%. The estimated annual energy savings from the harmonic reduction for each transformer amounted to 10, 707.86 kWh

In this study, technical loss evaluation of distribution transformers in the Electricity Company ... more In this study, technical loss evaluation of distribution transformers in the Electricity Company of Ghana (ECG) distribution system is considered. The purpose is to estimate level and severity of losses in distribution transformers and show that system losses can significantly be reduced by reducing losses in distribution transformers. The focus is however on harmonic related losses. The study analyses harmonic contents of 148 distribution transformers of total capacity of 74 MVA. The number of transformers investigated represents 1.6% of the total number of distribution transformers in the ECG distribution system. The evaluation of the losses was based on ANSI/IEEE C57.110-1986. Impact of harmonics on capacities of the transformers was also examined. Results show that harmonic currents, especially zero sequence harmonics, can increase losses in distribution transformer to over 200%. The cost of energy per year resulting from the harmonic loss was found to be GHc 2,220,395.11/year (US$ 555,098.78/year). It was also found that the harmonic effect de-rates the total capacity of the transformers by 27%. In other words, to ensure that the transformers are working within their economic life span, their total capacity should be reduced by 20 MVA.

Procedia Manufacturing

This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining ... more This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining system losses on HV and LV distribution networks in radial AC distribution systems. Challenges associated with system losses may demand network conversion from LV to HV network. This paper addresses this issue by using HVDS optimization specifically, linear programming techniques with Matlab optimization toolbox to determine the optimal number of unit transformers in the HV network. Studies conducted on a test distribution system using CYMEDIST software show the optimized HVDS has improved voltage profile and a total system loss reduction of 29.50% as compared to the LVDS. Consequently, there is reduced operational cost and increased annual capitalized loss savings in the optimized HVDS. Abstract This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining system losses on HV and LV distribution networks in radial AC distribution systems. Challenges associated with system losses may demand network conversion from LV to HV network. This paper addresses this issue by using HVDS optimization specifically, linear programming techniques with Matlab optimization toolbox to determine the optimal number of unit transformers in the HV network. Studies conducted on a test distribution system using CYMEDIST software show the optimized HVDS has improved voltage profile and a total system loss reduction of 29.50% as compared to the LVDS. Consequently, there is reduced operational cost and increased annual capitalized loss savings in the optimized HVDS.

2011 World Congress on Sustainable Technologies, 2011

Lightning protection design for a structure using Rolling Sphere Method is undertaken. In this ca... more Lightning protection design for a structure using Rolling Sphere Method is undertaken. In this case radius of the sphere is calculated using the 'Leader Potential Concept' for calculating striking distance. The purpose is to evaluate lightning protection performance based on the 'Leader Potential Concept'. It is also demonstrated how low grounding resistance and bonding could be used to mitigate Ground Potential Rise (GPR) and secondary effects of lightning activities on electronic equipment.

There are a number of methods which can be used to improve earth resistance of earth rods on site... more There are a number of methods which can be used to improve earth resistance of earth rods on sites where soil resistivity is high, replacement of the soil within its effective resistance area with more conductive soil being one of them. Replacing the soil in the entire effective resistance area is in general not practical. In this paper, the effectiveness of replacing soil in the critical resistance area only is shown by field tests. Application of this method requires calculation of earth rod resistance as a function of distance away from the rod. An analytical formula, derived and validated using test data to calculate these resistances, is also presented.

2009 2nd International Conference on Adaptive Science & Technology (ICAST), 2009

Based on response curves derived from field measurements, optimum number of vertical ground elect... more Based on response curves derived from field measurements, optimum number of vertical ground electrodes for grounding electrical installation is determined. On sites where the optimum number of the electrodes cannot reach a target ground resistance, a 'critical resistance area concept' with conductive backfills is used. In this study, efficiencies of local conductive backfills for reducing ground resistance are investigated. Results show that application of tyre ashes as a conductive backfills lowers ground resistance to over 80%. It is also shown that the most favourable benefit in the ground resistance improvement is to limit the backfill to 66% of the total number of ground electrodes installed.

Journal of Science and Technology (Ghana), 2009

In this study, the efficiency of materials available for free, namely palm kernel oil cake, tyre ... more In this study, the efficiency of materials available for free, namely palm kernel oil cake, tyre ash, wood ash and powdered cocoa shell, as conductive backfill for reducing earth electrode resistance was evaluated. Earth rod of 30-cm length and 14-mm diameter was installed for each backfilling material at a site and their performance compared with that of a reference earth rod also installed at the same site. The results show that tyre ash provides a stable earth electrode resistance in both dry and wet weather conditions and improves it to about 16%.

2011 IEEE/PES Power Systems Conference and Exposition, 2011

In this paper, application of HRC fuses and MCCBs in low voltage distribution network is examined... more In this paper, application of HRC fuses and MCCBs in low voltage distribution network is examined. Performance of HRC and MCCB are compared under a typical system performance condition. The law of equivalence of contact wear was used to determine life expectancy of MCCB. It is shown that MCCBs are not economically viable in areas where incidence of short-circuit faults

Achieving a Low Ground Resistance using Critical Resistance Area Concept. [AIP Conference Proceed... more Achieving a Low Ground Resistance using Critical Resistance Area Concept. [AIP Conference Proceedings 1247, 145 (2010)]. George Eduful, Joseph Ekow Cole, Philip Yaw Okyere. Abstract. Based on response curves derived ...

Lecture notes in electrical engineering, Sep 28, 2022

2021 IEEE 8th International Conference on Adaptive Science and Technology (ICAST), 2021

Pole-Mounted-Transformer (PMT) failures present a major threat to the Electricity Company of Ghan... more Pole-Mounted-Transformer (PMT) failures present a major threat to the Electricity Company of Ghana (ECG). These failures have been observed to occur frequently during thunder and lightning activities, raising strong suspicion that ECG’s existing pole mounted transformer protection scheme is inadequate. Over the years, the company has used and relied on the protection scheme that separates the primary surge arrester’s grounding from the low voltage neutral terminal of the pole mounted transformer. Unfortunately, literature on the subject is equally inconclusive . Whilst certain schools of thoughts encourage the interconnection of arrester grounding and LV neutral grounding, some codes do not allow it. In this study MATLAB Simulink is used to evaluate the effectiveness of the existing protection scheme adopted by the Electricity Company of Ghana. It was found that separating the HV grounding from the LV neutral grounding makes the transformer more vulnerable to lightning-induced overvoltage. The study recommends alternative solutions to deal with the problem.

World Academy of Science, Engineering and Technology, International Journal of Energy and Power Engineering, 2015

American Journal of Electrical Power and Energy Systems, 2019

Distribution transformers are generally provided with advanced control measures that ensure their... more Distribution transformers are generally provided with advanced control measures that ensure their operation and safety at a high reliability because their failure usually leads to long power outage, increase maintenance cost and unreliable provision of electricity to customers. Despite the protection measures that accompany a distribution transformer, there is still a need to provide extra remote monitoring systems to increase the reliability of operation and the confidence of instantaneous fault reporting. This paper deals with the design and construction of automatic monitoring system for power transformer parameters. An Arduino board coupled with XBEE module were programmed to enable the monitoring of voltage, current and temperature on a typical power transformer. The system was implemented and tested successfully. Results showed that the voltage versus temperature as well as current versus voltage characteristic obtained, were closed to datasheet specifications and therefore confirming the reliability of the proposed design. This system is therefore recommended as an additional protection that should be added to Power Transformers.

This paper presents a technique applied during the conversion of an existing Low Voltage Distribu... more This paper presents a technique applied during the conversion of an existing Low Voltage Distribution System (LVDS) into High Voltage Distribution System (HVDS) in radial networks. HVDS optimization is demonstrated using linear programming techniques in MATLAB optimization tool box. A test application results explain the methodology. The optimization technique proposed estimates the optimal number of unit transformers in the HVDS. This procedure is effective for converting the bulk transformer in the LVDS into an equivalent population of unit transformers in the HVDS. The benefit of the conversion technique is the minimization of transformer no-load losses. As a result, the economy of distribution transformers is improved by savings in operational cost.

2012 IEEE 4th International Conference on Adaptive Science & Technology (ICAST), 2012

A failure condition known as burndown and surface tracking of covered conductor insulating materi... more A failure condition known as burndown and surface tracking of covered conductor insulating material appears to be restricting the widespread use of covered conductors in Ghana. The paper identifies specific problems militating against the use of covered conductors and reviews international experience on the subject with the aim of developing a performance system specification for covered conductor use in Ghana. The paper also discusses advances in protection methods for detecting downed covered conductors and recommends effective protection scheme that must go with the adoption of covered conductors.

In this paper, two major international standards on harmonic emissions in power systems have been... more In this paper, two major international standards on harmonic emissions in power systems have been reviewed. The purpose is to help utility companies and stakeholders take informed decision regarding the safe limit of harmonic emissions and decide on which standard to adopt. The paper describes the principles underlying the original intent of PCC and clarifies some difficulties in relation to application of the standards. It is shown that location of PCC can be selected based on the method of power distribution system.

Based on response curves derived from field measurements, optimum number of vertical ground elect... more Based on response curves derived from field measurements, optimum number of vertical ground electrodes for grounding electrical installation is determined. On sites where the optimum number of the electrodes cannot reach a target ground resistance, a ‘critical resistance area concept’ with conductive backfills is used. In this study, efficiencies of local conductive backfills for reducing ground resistance are investigated. Results show that application of tyre ashes as a conductive backfills lowers ground resistance to over 80%. It is also shown that the most favourable benefit in the ground resistance improvement is to limit the backfill to four electrodes.

Triplen harmonic currents are becoming major concern in the Electricity Company of Ghana (ECG) di... more Triplen harmonic currents are becoming major concern in the Electricity Company of Ghana (ECG) distribution system. Significant levels of triplen harmonic currents generate heats, increase system losses and reduce the economic life spans of distribution transformers. In this paper, the performance of three harmonic suppressors in the control of harmonic emission levels in three ECG’s distribution transformer substations have been investigated. Harmonic parameters monitored include, harmonic currents, Total Harmonic Distortions (THD) and harmonic energy losses. Results show that the neutral blocking harmonic filters can reduce harmonic current in neutral conductors by 88% and consequently decrease harmonic energy loss by 97%. The estimated annual energy savings from the harmonic reduction for each transformer amounted to 10, 707.86 kWh

In this study, technical loss evaluation of distribution transformers in the Electricity Company ... more In this study, technical loss evaluation of distribution transformers in the Electricity Company of Ghana (ECG) distribution system is considered. The purpose is to estimate level and severity of losses in distribution transformers and show that system losses can significantly be reduced by reducing losses in distribution transformers. The focus is however on harmonic related losses. The study analyses harmonic contents of 148 distribution transformers of total capacity of 74 MVA. The number of transformers investigated represents 1.6% of the total number of distribution transformers in the ECG distribution system. The evaluation of the losses was based on ANSI/IEEE C57.110-1986. Impact of harmonics on capacities of the transformers was also examined. Results show that harmonic currents, especially zero sequence harmonics, can increase losses in distribution transformer to over 200%. The cost of energy per year resulting from the harmonic loss was found to be GHc 2,220,395.11/year (US$ 555,098.78/year). It was also found that the harmonic effect de-rates the total capacity of the transformers by 27%. In other words, to ensure that the transformers are working within their economic life span, their total capacity should be reduced by 20 MVA.

Procedia Manufacturing

This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining ... more This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining system losses on HV and LV distribution networks in radial AC distribution systems. Challenges associated with system losses may demand network conversion from LV to HV network. This paper addresses this issue by using HVDS optimization specifically, linear programming techniques with Matlab optimization toolbox to determine the optimal number of unit transformers in the HV network. Studies conducted on a test distribution system using CYMEDIST software show the optimized HVDS has improved voltage profile and a total system loss reduction of 29.50% as compared to the LVDS. Consequently, there is reduced operational cost and increased annual capitalized loss savings in the optimized HVDS. Abstract This paper evaluates HVDS and LVDS concepts by system performance. This is achieved by examining system losses on HV and LV distribution networks in radial AC distribution systems. Challenges associated with system losses may demand network conversion from LV to HV network. This paper addresses this issue by using HVDS optimization specifically, linear programming techniques with Matlab optimization toolbox to determine the optimal number of unit transformers in the HV network. Studies conducted on a test distribution system using CYMEDIST software show the optimized HVDS has improved voltage profile and a total system loss reduction of 29.50% as compared to the LVDS. Consequently, there is reduced operational cost and increased annual capitalized loss savings in the optimized HVDS.

2011 World Congress on Sustainable Technologies, 2011

Lightning protection design for a structure using Rolling Sphere Method is undertaken. In this ca... more Lightning protection design for a structure using Rolling Sphere Method is undertaken. In this case radius of the sphere is calculated using the 'Leader Potential Concept' for calculating striking distance. The purpose is to evaluate lightning protection performance based on the 'Leader Potential Concept'. It is also demonstrated how low grounding resistance and bonding could be used to mitigate Ground Potential Rise (GPR) and secondary effects of lightning activities on electronic equipment.

There are a number of methods which can be used to improve earth resistance of earth rods on site... more There are a number of methods which can be used to improve earth resistance of earth rods on sites where soil resistivity is high, replacement of the soil within its effective resistance area with more conductive soil being one of them. Replacing the soil in the entire effective resistance area is in general not practical. In this paper, the effectiveness of replacing soil in the critical resistance area only is shown by field tests. Application of this method requires calculation of earth rod resistance as a function of distance away from the rod. An analytical formula, derived and validated using test data to calculate these resistances, is also presented.

2009 2nd International Conference on Adaptive Science & Technology (ICAST), 2009

Based on response curves derived from field measurements, optimum number of vertical ground elect... more Based on response curves derived from field measurements, optimum number of vertical ground electrodes for grounding electrical installation is determined. On sites where the optimum number of the electrodes cannot reach a target ground resistance, a 'critical resistance area concept' with conductive backfills is used. In this study, efficiencies of local conductive backfills for reducing ground resistance are investigated. Results show that application of tyre ashes as a conductive backfills lowers ground resistance to over 80%. It is also shown that the most favourable benefit in the ground resistance improvement is to limit the backfill to 66% of the total number of ground electrodes installed.

Journal of Science and Technology (Ghana), 2009

In this study, the efficiency of materials available for free, namely palm kernel oil cake, tyre ... more In this study, the efficiency of materials available for free, namely palm kernel oil cake, tyre ash, wood ash and powdered cocoa shell, as conductive backfill for reducing earth electrode resistance was evaluated. Earth rod of 30-cm length and 14-mm diameter was installed for each backfilling material at a site and their performance compared with that of a reference earth rod also installed at the same site. The results show that tyre ash provides a stable earth electrode resistance in both dry and wet weather conditions and improves it to about 16%.

2011 IEEE/PES Power Systems Conference and Exposition, 2011

In this paper, application of HRC fuses and MCCBs in low voltage distribution network is examined... more In this paper, application of HRC fuses and MCCBs in low voltage distribution network is examined. Performance of HRC and MCCB are compared under a typical system performance condition. The law of equivalence of contact wear was used to determine life expectancy of MCCB. It is shown that MCCBs are not economically viable in areas where incidence of short-circuit faults

Achieving a Low Ground Resistance using Critical Resistance Area Concept. [AIP Conference Proceed... more Achieving a Low Ground Resistance using Critical Resistance Area Concept. [AIP Conference Proceedings 1247, 145 (2010)]. George Eduful, Joseph Ekow Cole, Philip Yaw Okyere. Abstract. Based on response curves derived ...