F.9
Date Code 20170927 Instruction Manual SEL-751 Relay
IEC 61850 Communications
IEC 61850 Operation
For Unbuffered Reports, as many as seven clients can enable the RptEna
attribute of the URCB at a time, resulting in multiple client associations for
that URCB. Once enabled, each client has independent access to a copy of that
URCB. The Resv attribute is writable, however, the SEL-751 does not support
reservations. Writing any field of the URCB causes the client to obtain its own
copy of the URCB-in essence, acquiring a reservation.
Reports are serviced at a 2 Hz rate. The client can set the IntgPd to any value
with a resolution of 1 ms. However, the integrity report is only sent when the
period has been detected as having expired. The report service rate of 2 Hz
results in a report being sent within 500 ms of expiration of the IntgPd. The
new IntgPd begins at the time that the current report is serviced.
Supplemental
Software
Examine the data structure and value of the supported IEC 61850 LNs with an
MMS browser such as MMS Object Explorer and AX-S4 MMS from Sisco,
Inc. The settings necessary to browse an SEL-751 with an MMS browser are
as follows:
Time Stamps and
Quality
In addition to the various data values, the two attributes quality and t (time
stamp) are available at any time. The relay determines the time stamp when it
detects a change in quality or data.
The relay applies a time stamp to all data and quality attributes (Boolean,
Bstrings, Analogs, etc.) in the same fashion as when it detects a data or quality
change. However, there is a difference in how the relay detects the change
between the different attribute types. For points that are assigned as SER
points, i.e., programmed in the SER report, the relay detects the change as the
receipt of an SER record (which contains the SER time stamp) within the relay.
For all other Booleans or Bstrings, the relay detects the change via the
scanner, which compares the last state against the previous state to detect the
change. For analogs, the scanner looks at the amount of change relative to the
dead band configured for the point to indicate a change and apply the
timestamp. In all cases, the relay uses these time stamps for the reporting model.
Functionally Constrained Data Attributes mapped to points assigned to the
SER report have 4 ms SER-accurate time stamps for data change events. To
ensure that you get SER-quality time stamps for changes to certain points, you
must include those points in the SER report. All other FCDAs are scanned for data
changes on a 1/2-second interval and have 1/2-second time-stamped accuracy. See
the SET R command for information on programming the SER report.
The SEL-751 uses GOOSE quality attributes to indicate the quality of the data
in its transmitted GOOSE messages. Under normal conditions, all attributes
are zero, indicating good quality data. Figure F.3 shows the GOOSE quality
attributes available to devices that subscribe to GOOSE messages from
SEL-751 datasets that contain them. Internal status indicators provide the
information necessary for the device to set these attributes.
For example, if the device becomes disabled, as shown via status indications
(e.g., an internal self-test failure), the SEL-751 sets the Validity attribute to
invalid and the Failure attribute to TRUE. Note that the SEL-751 does not set any
of the other quality attributes. These attributes always indicate FALSE (0). See the
Architect online help for additional information on GOOSE Quality attributes.
OSI-PSEL (Presentation Selector) 00000001
OSI-SSEL (Session Selector) 0001
OSI-TSEL (Transport Selector) 0001
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