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This paper summarizes the results of a post grid impact assessment of a Distributed Generated 20 MWp Solar PV plant on a 33-kV interconnection bus of a 161/33 kV substation within the Electricity Company of Ghana’s Limited distribution network located in the Gomoa Onyadze community in the Central Region of Ghana. The PV plant was commissioned since 2015. The paper assesses the impact of the PV plant in the following areas: The Demand Profile; Power Factor at the Point of Common Coupling (PCC); The Voltage Total Harmonic Distortion at the PCC; The Current Total Harmonic Distortion at the PCC; and the Voltage Profile at the PCC. The load profile was significantly distorted due to the active generation of the solar PV Plant. It now assumes a duck shape. The power factor at the 33 kV PCC bus deteriorated within the periods of active solar PV generation from 7:00 hours to 19:00 hours and went as low as 0.187 at noon time. The Voltage Total Harmonic Distortion (THD V) Levels at the 33 kV PCC bus where the solar PV Plant is interconnected, far exceeded the ECG allowable limits for THD V of 3%. The values were as high as 10%. The Current Total Harmonic Distortion (THD A) Levels at the 33 kV PCC bus of Transformer 1 far exceeded the limits of THD A of 5%. The values were as high as 65%. There was no significant impact on the voltage profile at the 33-kV bus where the solar PV plant was interconnected.

A number of studies have shown that better DG PV integration impacts, on the network are obtained when the DG PV are operated at lower power factors. However, at lower power factors, losses tend to increase, whilst voltage improvement is rather realized in the sub — transmission network. In this study, with the help of the CYME distribution software, the optimal impacts of varying the DG PV power factors on the ECG 33 kV sub — transmission network voltages and losses, are studied. The study revealed that as power factors at which DG PV is operated are reduced, bus voltages generally increase. However, losses rather tend to follow a U-shape trajectory. The minimum loss recorded in the sub-transmission network was 1.032 %, representing a 6.522 % reduction over the base case scenario value of 1.104 %. The corresponding optimal power factor of the DG PV was found to be 0.97.

In this paper, CYME Distribution software has been used to assess the impacts of solar Photovoltaic (PV) distributed generation (DG) plant on the Electricity Company of Ghana (ECG) 33 kV sub-transmission network at different PV penetration levels. As ECG begins to encourage DG PV interconnections within its network, there has been the need to assess the impacts on the sub-transmission losses and voltage contribution. In Tema, a city in Accra - Ghana, ECG has a 33 kV sub-transmission network made up of 20 No. 33 kV buses that was modeled. Three different locations were chosen: The source bus, a bus along the sub-transmission radial network and a bus at the tail end to determine the optimal location for DG PV interconnection. The optimal location was determined based on sub-transmission technical losses and voltage impact. PV capacities at different penetration levels were modeled at each location and simulations performed to determine the optimal PV penetration level. Interconnection at a bus along (or in the middle of) the sub-transmission network offered the highest benefits at an optimal PV penetration level of 80%. At that location, the maximum voltage improvement of 0.789% on the neighboring 33 kV buses and maximum loss reduction of 6.033% over the base case scenario were recorded. Hence, the optimal location for DG PV integration within the 33 kV sub-transmission utility network is at a bus along the sub-transmission radial network., {"references":["Ghana Grid Company Limited (GRIDCo), 2014 Electricity Supply Plan: GRIDCo, Tema: 2014.","Ministry of Energy, Republic of Ghana: National Energy Policy: February, 2010.","International Renewable Energy Agency (IRENA) Working Paper, \"Renewable Energy Technologies: Cost analysis series, Volume 1: Power sector: Issue 4/5, Solar Photovoltaics\", June 2012. p.12 – 13.","S. J. Lewis, \"Analysis and Management of the Impacts of a High Penetration of Photovoltaic Systems in an Electricity Distribution Network.\" Innovative Smart Grid Technologies Asia (ISGT).\" p.1 – 7, IEEE PES, 2011.","A. Sheikhi, A. Maani, F. Safe, A. M. Ranjbar, \"Distributed Generation Penetration Impact on Distribution Networks Loss\" International Conference on Renewable Energies and Power Quality (ICREPQ '13), Spain 20th – 22nd March, 2013.","Lucian Ioan Dulau, Mihail Abrudaen, Dorin Bica, \"Effects of Distributed Generation on Electric Power Systems.\" The 7th International Conference in Interdisciplinarity in Engineering (INTER – ENG 2013), Pg. 681 – 686, 2013.","Abraham Ellis, \"Grid operations and High penetration PV\", Sandia National Laboratories. Utility/Lab workshop on PV Technology and Systems, November 8 – 9, 2010, Tempe, Arizona. Available: http://www1.eere.energy.gov/solar/pdfs/2010ulw_ellis.pdf","Wei Song, Xinghua Zhou, Xiaolong Liu, Hongting Zhou, \"A study on impacts of Distributed Generation voltage in Distribution network system.\" Asia Pacific Energy Equipment Engineering Research Conference (AP3ER 2015), 2015.","Global Energy Consulting Engineers India, \"National Technical and Commercial Loss Study for ECG & VRA/NEDCo, Ghana\" submitted to the Ministry of Energy, Government of Ghana, 2012.\n[10]\tIEEE Standards Coordination Committee 21, \"IEEE Application Guide for IEEE Std. 1547™, IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems\" IEEE, 3 Park Avenue New York (NY), 15th April 2009\n[11]\tIng. Godfred Mensah, \"Basic System Planning for ECG Staff.\", System Planning Division, Electricity Company of Ghana (ECG), November 2015."]}

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.