W. Li et al., Determining number and timing of substation spare transformers using a probabilistic cost analysis approach, IEEE POW D, 14(3), 1999, pp. 934-939
Compared to the N-1 security design principle in each substation, common sp
are transformers shared by multiple substations can avoid considerable capi
tal expenditure and still assure a sufficient reliability level. Using comm
on spare transformers has been already a practice of some utilities in dist
ribution substation transformer planning. This paper presents a probabilist
ic approach to determining the number and timing of spare transformers shar
ed in a substation group. The proposed approach is based on the aging failu
re model of transformers, the overall reliability analysis and the probabil
istic damage cost model for a substation group, the capital cost model for
spares and the present value method. The spare transformer scheme obtained
using the presented approach provides both cost efficiency and sufficient r
eliability. A single transformer substation group in a non-urban region is
given as an application example to illustrate the procedure of the method.