Techno-Economic Analysis for Replacement of 11kV Overhead Koteshwor Feeder by Underground Distribution System

Abstract

Cost effective, Aesthetic and Reliable energy supply is the need of any mankind. In this study, technical and economic analysis for replacement of 11 kV overhead distribution feeder by 11kV underground cable is done with reference to Koteshwor Feeder under Baneshwor Distribution and Consumers Service. The cable rating and reliability indices of like SAIDI, SAIFI, ENS etc. of the feeder is performed by using DIgSILENT PowerFactory software. According to the connected load in each branches rating of cable is XLPE cable of size from 25 mm square to 400 mm square recommended and other related technical design is done by using available standards. Also, the reliability of overhead distribution system is evaluated by using real time system data system and similarly, historical IEEE standard data is used for underground distribution system. The reliability indices are compared for both distribution systems. Result shows that the SAIFI value is 49.99 per annum which is very high as compared to designed underground system which is 0.337 for designed underground distribution system. Also, the energy not supplied (ENS) value of existing system is almost five-time higher value as compared to designed underground distribution system. The replacement cost estimation is evaluated by using Nepal Electricity Authority unit rate and KEI industries quoted price for NEA underground project. The B/C ratio and Present Worth value for the 25-year period of useful life shows that the replacement of the existing overhead distribution system by underground distribution system is financially viable and can be payback in 6 to 7 year by saving revenue NRs. 3,424,993.00 obtained from the lower value of Energy Not Supply (ENS) of underground distribution system than overhead distribution system. In order to get the continuous of supply, aesthetic and public safety in electricity distribution field one may have to bear initially extra cost to use underground distribution systems which finally get payback. Thus, in case of densely populated city like Kathmandu, underground distribution system is reasonable requirement for continuous supply, aesthetic and public safety in electricity distribution filed.