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configured IED description files. All these files are constructed in the same
methods and format but have different scopes depending upon the need.
17.2.2.1 Setting up Protocols Using IEC 61850
The first step is to define the SAS functions, IEDs and their relation to the
primary substation components. Additional notes should be made on any
specific functions and the information to be transferred to other IEDs in the
system. These functions should be defined using SCL.
An IED-ICD file is generated and transferred to SCD file by an IED con-
figuration tool; this is done for each different IED in the system.
Additionally, the system specification can be described in SCL by a SSD
file and/or transferred to a SCD file using a system specification tool.
Then the SCD-61850 file is downloaded to each IED using the system
configuration tool.
The SCD file defines the substations, IEDs, communication, and logic
nodes using SCL.
The following items should be confirmed by the manufacturer to confirm
compatibility with IEC-61850:
Protocol implementation conformance statement.
Protocol implementation eXtra information for testing.
Model implementation conformance statement.
17.2.2.2 Security of IEC-61850
Using IEC-61850 retains the security of the following criteria:
Confidentiality: protecting information.
Authentication: clear definition of user.
Access control: different level of access.
Message integrity: ensures that message is not tampered with.
17.3 GENERAL DESCRIPTION OF A SUBSTATION
AUTOMATION SYSTEM
As discussed earlier in this chapter, an automatic control system in a substa-
tion are divided in three levels locally in substation, and one level in the
master station, as follows:
1. Master station level.
2. Substation level.
3. Bay level.
4. Process level.
A substation automation system such as that shown in Fig. 17.2 has dif-
ferent interface systems, hardwired or optical interfaces, and a process bus.
