Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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16.9
Date Code 20171006 Instruction Manual SEL-400 Series Relays
DNP3 Communication
DNP3 in the Relay
Event Data
DNP3 event data objects contain change-of-state and time-stamp information
that the relay collects and stores in a buffer. You can configure the relay 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, ECLASSA, and ECLASSV
you can set the event class for binary, counter, analog, and virtual terminal infor-
mation. You can use the classes as a simple priority system for collecting event
data. The relay does not treat data of different classes differently with respect to
unsolicited messages, but the relay does allow the master to perform independent
class polls.
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 relay.
For event data collection you must also consider and enter appropriate settings
for dead band and scaling operation on analog points shown in
DNP3 Settings—
Custom Maps on page 12.15 . You can either set and use 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
Configurable Data Mapping on page 16.23 for a dis-
cussion of how to set scaling and dead-band operation on a point-by-point basis.
The serial port settings ANADBA, ANADBV, and ANADBM (ANADBA n ,
ANADBV n , and ANADBM n for Ethernet port settings on session n ) control
default dead-band operation for the specified data type. Because DNP3 Objects
30 and 32 use integer data by default, you can use scaling to send digits after the
decimal point and avoid truncating to a simple integer value.
With no scaling, the value of 12.632 would be sent as 12. With a scaling setting
of 1, the value transmitted is 126. With a scaling setting of 3, the value transmit-
ted is 12632. You must make certain that the maximum value does not exceed
32767 if you are polling the default 16-bit variations for Objects 30 and 32, but
you can send some decimal values using this technique. You must also configure
the master to perform the appropriate division on the incoming value to display it
properly.
Set the default analog value scaling with the DECPLA, DECPLV, and DECPLM
settings (DECPLA
n , DECPLV n , and DECPLM n for Ethernet port settings on
session n ). Application of event reporting dead bands occurs after scaling in the
DECPLA, DECPLV, and DECPLM. For example, if you set DECPLA to 2 and
ANADBA to 10, a measured current of 10.14 amperes would be scaled to the
value 1014 and would have to increase to more than 1024 or decrease to less than
1004 (a dead band of 0.2 amperes) for the relay to report a new event value.
The relay uses the NUMEVE and AGEEVE settings (NUMEVE n and AGEEVE n
Ethernet port settings for session n ) to decide when to send unsolicited data to the
master. The relay sends an unsolicited report when the total number of events
accumulated in the event buffer reaches NUMEVE. The relay also sends an unso-
licited report if the age of the oldest event in the buffer exceeds AGEEVE. The
relay has the buffer capacities listed in
Table 16.7 .
Table 16.7 Relay Event Buffer Capacity
Type Maximum Number of Events
Binary 1024
Analog One event per analog input in the DNP3 Map
Counters One event per counter input in the DNP3 Map
Virtual Terminal Objects 5