Experience in incremental replacement and continuous upgrade of an energy management system

New England Power Exchange (NEPEX), after evaluating several alternatives, decided to upgrade their existing EMS system using phased replacement. As a first step, a security upgrade system (SUS) was added to perform all network security functions. The SUS was designed for continuous improvement through future releases from the vendor. Since its installation, the SUS has gone through two upgrade cycles within the last three years. Upgrade of EMS software offers considerable advantages to a utility, viz. new functionality, access to the latest technology, uniformity with other users of the software, standard fixes to software bugs. It also poses considerable risks by compromising integrity of the system during upgrade. This study discusses our experience through two upgrade cycles. In particular, it discusses the methodology used to track changes to the software during and between upgrades and the effort required for the upgrade. The study suggests several guidelines to make future upgrades of EMS software easier to perform.