This paper describes the development of an IEC 61850 based substation automation system (SAS) architecture. IEC 61850 is a standard for the design of electrical SAS. It defines the communication between IEDs in the substation and the related system requirements. The GOOSE messaging, Substation Configuration description Language (SCL) makes IEC 61850 more reliable, and the bottlenecks faced like the one of interoperability have been addressed. In addition to lowering the installation and commissioning costs, a significant reduction in maintenance cost can also be achieved. It minimizes costs of technological obsolescence because of a global acceptance and adoption and future-proof concept of abstract services as well as independence of mapping to protocols. The above architecture is modeled using UML and XML. Lower equipment migration costs, reduced wiring, ease in integration and the ease in adding functionalities to the existing SAS makes IEC 61850 based SAS a widely accepted norm.