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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.

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.

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.

Within a period of two years, the Electricity Company of Ghana (ECG) lost a total of six grounding transformers in a particular substation. The situation created a lot of instability and resulted in huge productivity losses to both the company and its customers. The failures were believed to be related to wrong selection of grounding transformer rating. However, using the concept of capacitive charging current of a system, it was found that the short time rating of the grounding transformers were rightly selected. Analysis of the phenomenon strongly linked the damages to protection deficiency. This paper discusses analysis of the problem and proposes decision criteria for selecting a grounding transformer.

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 are rampant. Where electro-dynamic stress associated with circuit interruptions is of a major concern, application of HRC fuses is proposed. The study goes further to recommend a suitable combination of MCCBs and HRC fuses as effective means of protecting distribution transformers.

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 ground electrodes.

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.

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%.

This paper presents a study on Palm Kernel Oil Cake (PKOC) as an earth resistance-reducing agent. The PKOC is a derivative of palm kernel nut after extraction of oil. Significant earth resistance reduction is obtained by means of replacing soil within ‘critical resistance area’ of an earth electrode with the PKOC.The properties of PKOC as an earth resistance-reducing agent is investigated. Among the important properties considered are moisture content, moisture holding capacities, pH (acidity) level, and its resistivity. The paper presents and discusses the techniques in the PKOC application and reports the results achieved which demonstrate effectiveness of the PKOC.