The software design of power system computation often requires modifications due to modernization of existing network and automation of the power system operation. Object-oriented design has gained widespread importance and acceptance in software development due to its advantages over other methodologies. An object-oriented design for power system analysis is proposed in this paper with greater concentration on power system equivalents and distribution system. The important contribution of this paper is the development of software objects for various transmission and distribution system components, which can be reused in most of the power system analysis programs. © Indian Institute of Science.