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.
Advanced geomagnetic storm forecasting: a risk management tool for electric power system operations
Geomagnetic disturbances (i.e., space storms) can impact the operational reliability of transmission systems. Solar Cycle 22 (the most recent solar cycle extending from 1986 to 1996) demonstrated to the power industry the need to take into consideration the potential impacts of geomagnetic storms. Experience gained from the unprecedented scale of these recent storm events provides compelling evidence of a general increase in electric power system susceptibility. Important infrastructure advances have recently been put in place that provide solar wind data. This new data source along with numeric model advances allows the capability for predictive forecasts of severe storm conditions, which can be used by impacted power system operators to better prepare for and manage storm impacts.