Geomagnetically induced current model for the Namibian High Voltage Network
Geomagnetically Induced Currents (GICs) are low-frequency currents that enter power transmission networks through the grounded-neutral points of the transformer windings. The paper presents a model to emulate the flow of this current. As early as in 1998, GICs studies within the Southern African region focused on demonstrating the existence of GIC in this mid-middle latitude region. Recent literature has amply argued, proved and demonstrated the presence of GICs in the Namibian Transmission Network during a Geomagnetic Disturbance (GMD). Geomagnetic disturbances are perturbations in the magnetosphere which produce variations in the Earth's geomagnetic field, hence leading to flow of GIC in the transmission networks. Since the GICs are DC-like currents they are also essentially referred to as “quasi-DC” currents. Consequently, conventional AC models used in power system studies cannot be used directly to analyse the GIC flow in the electric transmission system, and hence there is need for the development of a working DC model to carry out GMD impact studies on the Namibia Power Network. In this paper, a working quasi-DC model for the Namibia High Voltage (HV) Transmission network is presented. The model is tested via modelling and simulation of GIC flows in the network using the EPRI OpenDSS (Open Distribution Simulation Software). The partial results seem to suggest that the magnitudes of GICs in the network are increasing with the expansion and development of the network since early 2002. The effects of probable network contingencies, based on N-1 Criterion, on the flow of GICs are also presented.
Geomagnetically induced currents in the Southern African electricity transmission network
This report describes the findings of the extended investigation into the existence and effects of geomagnetically induced currents (GICs) on the Southern African network. This would also apply to any other network at mid-latitude. The transmission network was modelled and the GICs calculated for major storms at various substations. Thereafter equipment was installed at two substations to monitor the performance of transformers during geomagnetic storms. The measured results were compared to calculated for verification of the modelling technique used and assumptions made. This report also describes the performance of network equipment such as transformers and reactors in the presence of GICs. Condition monitoring is used to investigate the link between degradation of these units and geomagnetic activity. The development of a preparation process and mitigational techniques are also described in the report. By combining the advanced warning process with operational procedures it could assist network operators to manage the network during a geomagnetic storm and thus reduce the probability of network perturbations and equipment damage.
Public health in eight European countries: an international comparison of terminology.
OBJECTIVES
The aim of this paper was to assess the use of different terms pertaining to public health in selected Member States of the European Union.


STUDY DESIGN AND METHODS
Qualitative research methods were used to compare the terminology among eight Member States. Seven to nine core terms were defined for each country, and a search was performed for these terms in the names of institutions and professional titles, organized into three comparable categories.


RESULTS
The data analysis showed considerable diversity in terminology. The three most commonly used terms for each country, and the frequency distribution of the core terms for all eight countries were determined.


CONCLUSION
Public health terminology and underlying concepts vary among Member States of the European Union. A large number of loosely related terms are in use, indicating the lack of a common conceptual framework for the discipline of public health. The most commonly used terms pertaining to public health are 'health sciences' and 'health promotion'. 'Public health' is not among the most commonly used terms.