In Ghana, the bulk generation and transmission of electricity was largely provided by the Volta River Authority (VRA) until the transmission and systems operation component was hived off to create the Ghana Grid Company Limited – GRIDCo.
GRIDCo’s core responsibilities are to undertake economic dispatch and transmission of electricity from wholesale suppliers to bulk customers; acquire and manage assets, facilities and systems required to transmit electrical energy; provide metering and billing services to bulk customers; and carry out transmission system planning and implement necessary investments to provide the capacity to reliably transmit electric energy.
Prospects in the electricity sector in Ghana are very high and it is projected that by the next five years about 1,000 MW of additional generation would be added to the grid. Power evacuation from the generating stations to bulk customers is facilitated by almost 5,000 km of high/extra high voltage transmission lines and substations.
With the rapidly increasing demand (at about 10% per annum) and associated generation capacity, GRIDCo has pursued an aggressive system expansion, upgrade and rehabilitation programme to meet the load growth and reliability requirements. The huge power system infrastructure, both present and future, cannot be built and managed efficiently and economically without adequate and reliable geospatial information.
Use of Geospatial Systems in GRIDCo
In order to achieve its development functions, GRIDCo has deployed geospatial technology from project conception stage through to specific site selection, land acquisition and valuation, design and construction phases of project implementation.
However, geotechnical data usage is not very advanced at the engineering phase of project implementation, which results in diversions, land litigations, conflicts with other environmental and social requirements, multiple payments of compensation and inadequate valuation of property, all of which result in delays in project implementation and also non-optimized location of the facilities.
The main processes, procedures and techniques used in GRIDCo in developing transmission system facilities include:
Site and Route Selection
Routing of transmission lines is more difficult than routing of other public infrastructure. In developing countries like Ghana, transmission line route selection, which forms the basis for optimum transmission line design, can be time consuming and does not necessarily produce satisfactory results because the whole process is done manually. The objective is to select the best and shortest possible route that meets all acceptable technical requirements and is financially acceptable with minimum socio-environmental impact.
The site selection and survey work carried out for transmission lines involves the identification of a topographic map in 1:50,000 and a town sheet map of 1:2,500, covering the two ends of the line. Subsequently, an office study is done to emphasize all possible existing and future obstructions which can interfere or compromise the project. Thereafter, a preliminary line route is drawn on the topographic map showing where the proposed line will traverse. A field trip is undertaken to verify and confirm the possibility of the preliminary route identified. Another office discussion is carried out to finalize the proposed route prior to detailed survey. At the end, the best and shortest possible route with minimum environmental and social implications is then proposed for detailed survey.
On the other hand, while selecting site for substations, the following points have to be considered: availability of land, nature of soil and vegetation, closeness to existing power lines facilities, availability of access road and closeness to the load centre or generating plant.
The preliminary survey data is used to establish project cost estimates to be used for budgetary purposes. The preliminary survey is then followed by a detailed survey involving the cartographic survey of the entire route right of way (ROW) or substation site.
Following the award of construction contracts, a final survey is carried out to ‘spot” the towers and detailed engineering surveys for the “As Found” terrain for substation sites. Additional conflicts may be established once again. Sometimes resolution of these conflicts has resulted in project cost increase of over 15%.
In general, there is always a major restriction to the level of overview, judgment and optimisation that is required in the implementation of projects.
It is believed that the use of the present advanced technologies such as Geographic Information Systems (GIS), Aerial Photography, Google Earth maps, etc would reduce and/or eliminate the conflicts, reduce the project implementation time, reduce project costs and fully optimize lines and substation designs.
Use of Geospatial Information in Operation and Maintenance
After the construction of the facility, all the geospatial data gathered from the transmission line are stored and does not feature in the maintenance and operation of the transmission lines and substations.
However, with the appropriate geospatial information available, all the maintenance activities could be expedited and executed at minimum cost.
After the acquisition of the geospatial data from the field through the conventional means, the ability to manage, analyze and visualize it relative to the economic, social and environmental issues and obstructions becomes very difficult, hence the challenges the agency faces in the cost of its operation.
There is, however, growing awareness in GRIDCo about the need to use geospatial technology and thus expedite and enhance project development and implementation, as well as improve the operation and maintenance of these facilities.
Way Forward in the Use of Geospatial Technology in GRIDCO
Each of the factors for transmission line route and substation selection corresponds to a spatial data set. Therefore, selecting of transmission line and substation for power transmission is a spatial problem. GIS is currently one of the most effective tools for resolving such complicated problems. GIS is already used in transmission line routing as a technical tool. In GIS, raster data models which is used for storage and visualization of spatial data sets provides important advantages. GRIDCo intends to undertake the following activities to enhance its usage of geospatial technology in its operations.
• Convert all analogue drawings into digital format
• Survey and mapping of all GRIDCo facilities
• Convert all existing infrastructure and facilities into GIS format
• Use more of aerial photography and satellite imagery
• Procure state-of-the-art software in GIS
• Link all geospatial data set to GIS in order to enhance operations and maintenance
To achieve the above objectives, GRIDCo has made a budgetary allocation of USD 2 million over the next 5 years towards the implementation of GIS and other advanced geospatial technology.