Physically smaller dielectric materials would improve the optimisation of space for power systems. Development of nanotechnology provides an effective way to improve the performances of insulating oils used in power system applications. In this research study, we focused on the development of nanomodified vegetable oils to be used in power transformers. Higher conduction currents were observed in virgin linseed oil than in virgin castor oil. However, for both virgin linseed and virgin castor oil, the DC conduction current increased approximately linearly with the applied DC voltage. In nanomodified linseed oil, the characteristic curve showed two distinct regions: a linear region (at lower applied voltage) and a saturation region (at slightly higher voltage). Conversely, in nanomodified castor oil, the characteristic curve showed three distinct regions: a linear region (at lower applied voltage), a saturation region (at intermediate applied voltage) and an exponential growth region (at higher applied voltage). The nanomodified linseed oil exhibited a better dielectric performance than the nanomodified castor oil. Overall, the addition of nanodielectrics to vegetable oils decreased the dielectric performance of the vegetable oils. The results of this study contribute to the understanding of the pre-breakdown phenomenon in liquid nanocomposite dielectrics.

Absiruc;: One of mankind's greatest modera challenges i m poverty alleviation. The provision of electricity c m greatly assist in tbh regard 111. The tapping of small amounts of power from nn HVDC transmission b e represents a solution to the above problem espceirlly in rural areas. The work conducted to facilitate tbe pubiishlng of this paper was divided into two phases namely, a technical feasibility study and an economic VlabWty study. This paper addresses the technical feasibility of tapphg small amounts of power from HVDC transmission lines. The paper aualyses the dynndc rbaractenlrtics of the parallel-cascaded tapping station. The results obtained clearly indicate that the parallel-rascaded tapping station prove to be a viable solution to tapping small amounts of power from an HVDC transmission line. A fnture paper will address the economic feasib+ty of tapping small amounts of power from HVDC transmission lines. Indcx icnns: Rural electrification, HVDC transmission lines, voltage source inverter, EMTDC r. INTRODUCTION Today, almost half the world's population, especially those in developing countries in South Asia and subSaharan Afiica, are without electricity [I]. Elechicity is essential for sustainable human development. Its availability is fundamental for economic development and social uplifhnent. Orthodox methods for the provision of electricity supplies, such as a central power station with a transmission and distribution network, which is ideal in industrial counixies and urban areas, may not be the most economical means of providing electricity supplies in developing countries, particularly in rural areas where the demand per customer is only a small hction of a kilowatt [I]. Mobilizing of capitaI and developing of new technologies is necessary in supplying power to these rural areas. In the &can context, there are large amounts of hydropower in Central Afiica, in countries such as the Democratic Republic of Congo, whereas the major load centers are in the Southem Afi-ican region. Therefore, high voltage direct current (I-IVDC) transmission is likely to be the most economical means to transmit these large quantities of energy to the Southem Afican region. HVDC transmission does offer technical and economical advantages over W A C (high voltage alternating current) transmission for long distances. Manuscript received May 19,2004. This work was suppned in pan by tbe Eskom and THIUP. L. Chetty i s With Technology Services International, Eskom Enterprises, Priwte Bag 40175, CLevcland, Johannesburg, South A6ica (phone: +27 11 629 5408; fax +27 11 629 5369; e-mail: tean.chetty@ eskommza). A. C. Britten is with Technology Services International, Eskom Enterprises, Private Bag 40175, Cleveland, Johannesburg, South AMca @bone: +27 I 1 629 5033; fax: +27 I I 629 5369; e-mail tony.briiten@ csloncoa). N.M. 1jumk.a , is with the UniveFsity of Kwa-Zulu Natal, Durban, South AMca. He is the Dean for the Fztcutly of Engineering (Westville ~amous). k-mail: iiumban@ukm.co.zai However, HVDC ttammission does suffer a s...

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One of mankind’s greatest modern challenges is poverty alleviation. The provision of electricity can greatly assist in this regard. The tapping of small amounts of power from an HVDC transmission line represents a solution to this problem especially in rural areas. This paper analyses the dynamic characteristics of a parallel-cascaded tapping station. The results obtained clearly indicate that the parallel-cascaded tapping station proves to be a viable solution to tapping small amounts of power from an HVDC transmission line.

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