Understanding and Simulating the IEC 61850 Standard - CiteSeerX

SERVER
LOGICAL-DEVICE
LOGICAL-NODE
DATA OBJECT
LOGICAL-DEVICE
LOGICAL-NODE
DATA OBJECT
DATA ATTRIBUTE
LOGICAL-DEVICE
LOGICAL-NODE
DATA OBJECT
DATA ATTRIBUTE
...
...
...
...
Figure 3: Hierarchy of the IEC 61850 data model
reasons. Firstly, data objects are just logical collections
of the contained data attributes while (primitive) data attributes
are the de facto logical correspondence to the
physical entities (memory units, registers, communication
ports, etc.); secondly, the purpose of data objects is
for the convenience of managing and exchanging values
of a group of data attributes sharing the same function.
Despite data objects, the IEC 61850 standard provides
the concept of data set as another ways to manage and
exchange a group of data attributes. Members of a data
set can be data objects or data attributes. The concept of
data set is somewhat similar to the concept of view in the
area of database management systems. In the IEC 61850
standard, most services involve data sets. Members in a
data set unnecessarily come from the same logical node
or the same data object, thus providing high flexibility
of data management. Data sets are categorized into permanent
ones and temporary ones. Permanent data sets
are hosted by logical nodes and will not be automatically
deleted unless on the owners’ explicit requests; temporary
data sets are exclusively hosted by the association
having created them and will be automatically deleted
when the association ends.
Compatible Logical Node
Common Data Class
0..2
TrgOp
1
Functional Constraint
1
DAType
1..n
1 1*
1
1
1
SERVER
1
1..n
LOGICAL DEVICE
1
1..n
LOGICAL NODE
1
1..n
DATA
1
1..n
FCDA
0..n
1
2.6 Service model
BasicType
Services provided by ACSI include querying object set,
getting/setting data values, controlling system objects,
report manipulation, log manipulation, and other services
like file upload/download. Table 3 gives a list of
ACSI services defined in the IEC 61850 standard.
All ACSI services are requested by applications and
responded by servers. In order to request a service in
a server, an application must first establish a valid twoparty
application association (TPAA) with the server.
The TPAA maintains the session states and provides a
virtual view of the server to the application. A typical
interaction procedure between an application A and a
server S goes as follows:
1. A establishes a TCP connection with S;
2. A “logs in” to S by requesting the Associate service
from S, providing authentication related information
as parameters;
Figure 4: The data model of the IEC 61850
3. S validates the information provided by A and creates
a TPAA object, which provides a virtual view
of S to A;
4. A requests subsequent services while S processes
the requests and responses with appropriate responses
defined in the IEC 61850 standard;
5. A issues a Release request to S;
6. S reclaims the TPAA of A and ends the session.
The virtual view of server provided by a TPAA enforces
the access control policies set forth by the server.
This virtual view defines which objects in the server are
visible and accessible to the application and what kinds
of service of those objects are accessible from the application.
The concept of virtual view is very flexible and
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