Implication of using auxiliary service voltage transformer sub-stations for rural electrification
Michael Juma Saulo and Charles Trevor Gaun
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Abstract: Providing an affordable and reliable electricity supply to rural communities is seen by countries round the world as one of the major keys to development. A good quality and stable electricity supply can provide a wide variety of benefits including lighting (allowing evening activities), clean cooking and heating, access to television/radio, telephone (including mobile), improved health (due to example refrigeration), and many small industrial uses. Often this can be provided by extending the main electricity network to the community. However, for remote rural areas the costs involved can be very high. Therefore, Un-conventional Rural Electrification (URE) technologies are thus very relevant, particularly for countries in sub-Saharan Africa (SSA), as they have potential to make connection to the electricity network affordable. While such systems are already in use, their penetration level is very low. Hence, if the penetration level of such system in power network increases, what is the effect on power and voltage quality, stability and capacity constraints of the overall system? What are the limiting factors, and how can this limit be determined for any particular rural electrification project. These are some of the major questions that this paper address progressively. The paper investigated the maximum penetration level of sub-station based Auxiliary Service Voltage Transformer (ASVT) technologies in transmission power networks with regard to voltage quality, stability, and capacity constraints. This was done by comparing the simulation results of ASVT(s) penetration on a transmission power network with the constructed Surge Impedance Loading (SIL) curves. The curves were derived from the ABCD parameters of the transmission line under investigation. Results showed that ASVT sub-station technologies can be applicable to any HV transmission line whose voltage level is within the 6% tolerance when the load power factor is varied between 0.2 and unity power factor. Moreover, the Loadability tests carried out showed that ASVT system could be operated within allowable voltage profile, if 1MW at 0.3 to 0.5 power factor lagging load was connected.