3 Levels of IEC 61850 based SAS architecture

• Station level :

It includes Human Machine Interface (HMI) and gateways to communicate with remote control center and integrate IEDs at the bay level to the substation level. It also performs different process related functions such as implementation of control commands for the process equipment by analyzing data from bay level IEDs.

• Bay level:

The process level equipments are connected to station bus via IEDs at the bay level that implement monitoring, protection, control and recording functions.• Process level. It includes switchyard equipment, sensors and actuators. The current and potential transformers are located at the process level to collect system data and send them to bay level devices for automatic control & protection operations which are achieved through circuit breakers and remotely operated switches.

• Station bus:

It exists at the substation level and is used for communication between IEDs at the bay level and the stationlevel. Several Redundancy methodologies are employed to select station bus architecture for improving thereliability and performance of various protection and control functions carried out by IEDs at the stationlevel.