Page 32 - From Smart Grid to Internet of Energy

Introduction to smart grid and internet of energy systems Chapter 1 21

substation automation in addition to communication standards. Although IEEE
1815 is one of the most widely adopted standard in substation automation, it
only includes communication standards for low bandwidth monitoring and con-
trol operations. On the contrary, IEC 61850 provides real time protection and
control applications in high bandwidth in addition to others provided by IEEE
1815 standard. Thus, IEC 61850 is the most convenient and widespread proto-
col used for substation automation and communication systems. IEC 61850
standard describes a wide variety of IED types as breaker, switches, merging
units, protection and control devices in addition to generic IED definitions.
The protection and control IED devices accomplish supervising the control
and protection operation throughout their service bay unit while breaker and
switches are required to monitor the actual situation of circuit breakers, to com-
municate with protection and control IEDs for information signals and manages
trip or close operations regarding to receive protection signals. The merging
unit type IEDs are responsible to provide sampled status signals to protection
and control IEDs corresponding to acquired measurement signals from field
sensors such as current and voltage transducers that generate sampled measured
values (SMV). The acquired analog values are converted to digital signals and
transmitted to protection and control system to provide instant status informa-
tion. The communication architecture of IEC 61850 standard has been con-
structed in a hierarchical structure that is comprised by station, bay, and
process levels as illustrated in Fig. 1.7 [13]. The Process Level includes field

FIG. 1.7 Hierarchical diagram of an IEC 61850 based substation automation [13].