The impact of IEDs on the design of systems used for operation and control of power systems

The design of systems used for operation and control of electric power systems, commonly called a supervisory control and data acquisition (SCADA) system, energy management system (EMS) or distribution management system (DMS) is still oriented towards deterministic operations. However, the advent of intelligent electronic devices (IEDs) in the substation, and the potential volume of time data they can supply, creates a requirement to re-assess the basic design criteria. This paper begins with a brief overview of the main elements of substation automation. It then considers some of the typical features and functions that make up the significant characteristics of a SCADA/EMS/DMS. The paper considers both the 'positive' and 'negative' impacts of IED data volumes in such areas as database and display principles, processing of alarms and events, alarm identification and performance of control functions, and design of analytical programs. The easiest solution, which seems to be the preferred method today, is to make slight adjustments to the basic designs; and ignore the balance of the issues. On the other hand, incorporating the capabilities of IEDs, and taking advantage of the data volumes in the basic EMS/DMS design can greatly increase the ability of the control system and the operators to manage the electric power system in a safe, reliable and economic manner.