R.6.33
Date Code 20111215 Reference Manual SEL-421 Relay
DNP3 Communications
DNP LAN/WAN in the SEL-421
Data Access
The data access methods listed for Serial DNP3 in Table 6.4 are also available
for DNP LAN/WAN, with the exception of Virtual Terminal classes.
Tab le 6.19 lists the appropriate settings for DNP LAN/WAN. The DNP3
master session must be configured for one of the data access methods below.
As with Serial DNP3, in both the unsolicited report-by-exception and
quiescent polling methods shown in Table 6.19, you must make a selection for
the session’s PUNSLnn setting. This setting enables or disables unsolicited
data reporting at power up for this session. If your master can send the DNP
message to enable unsolicited reporting from the SEL-421, you should set the
session’s PUNSLnn to No.
See DNP3 in the SEL-421 on page R.6.5 for more information on configuring
DNP LAN/WAN sessions.
Event Data
The same serial DNP event data objects are available for DNP3 over an
Ethernet network. However, configuration is slightly different. You can still
configure the SEL-421 to either report the data without a polling request from
the master (unsolicited data) or hold the data until the master requests it with
an event poll message.
With the event class settings ECLASSB, ECLASSC, and ECLASSA, you can
set the event class for binary, counter, and analog information. Virtual terminal
information is not supported for DNP LAN/WAN since Telnet is available to
provide this capability. As with serial DNP3, you can also use the classes as a
simple priority system for collecting event data.
For event data collection, you must also consider and enter appropriate
settings for dead band and scaling operations on analog points shown in
Tab le 6.20. You can set and use either default dead band and scaling according
to data type or use a custom data map to select dead bands on a point-by-point
basis. See Custom Data Mapping on page R.6.38 for a discussion of how to
set scaling and dead-band operations on a point-by-point basis.
The setting ANADB defines default dead-band operation for analog events. A
DNP3 master may also impose its own default dead band that it will use for
event data for a specific channel that override the relay’s ANADB setting.
Because the default variations of DNP Objects 30 and 32 use integer data, you
must use scaling to send digits after the decimal point and avoid rounding to a
Table 6.19 DNP LAN/WAN Access Methods
Access Method Master Polling SEL-421 Settings
Polled static Class 0 Set ECLASSB, ECLASSC,
ECLASSA to Off, UNSLnn
to No (where nn is the
session number from 01–
10).
Polled report-by-exception Class 0 occasionally, Class
1, 2, 3 frequently
Set ECLASSB, ECLASSC,
ECLASSA to the desired
event class, UNSLnn to No.
Unsolicited report-by-
exception
Class 0 occasionally,
optional Class 1, 2, 3 less
frequently, mainly relies on
unsolicited messages
Set ECLASSB, ECLASSC,
ECLASSA to the desired
event class, set UNSLnn to
Yes and PUNSLnn to Yes or
No.
Quiescent Class 0, 1, 2, 3 never, relies
completely on unsolicited
messages
Set ECLASSB, ECLASSC,
ECLASSA to the desired
event class, set UNSLnn
and PUNSLnn to Yes.
NOTE: Most RTUs that act as
substation DNP3 masters perform an
event poll that collects event data of
all classes simultaneously. Confirm
that the polling configuration of your
master allows independent polling for
each class before implementing
separate classes in the SEL-421.
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