Sel 751A, Инструкция по эксплуатации

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D.7
Date Code 20100129 Instruction Manual SEL-751A Relay
DNP3 Communications
DNP3 in the SEL-751A
In both the unsolicited report-by-exception and quiescent polling methods
shown in
Table D.5 , you must make a selection for the PUNSOL n setting.
This setting enables or disables unsolicited data reporting at power up. If your
DNP3 master can send a message to enable unsolicited reporting on the
SEL-751A, you should set PUNSOL
n to No.
While automatic unsolicited data transmission on power up is convenient, this
can cause problems if your DNP3 master is not prepared to start receiving data
immediately on power up. If the master does not acknowledge the unsolicited
data with an Application Confirm, the device will resend the data until it is
acknowledged. On a large system, or in systems where the processing power
of the master is limited, you may have problems when several devices
simultaneously begin sending data and waiting for acknowledgement
messages.
The SEL-751A allows you to set the conditions for transmitting unsolicited
event data on a class-by-class basis. It also allows you to assign points to event
classes on a point-by-point basis (see
Configurable Data Mapping on
page D.13 ). You can prioritize data transmission with these event class
features. For example, you might place high-priority points in event class 1
and set it with low thresholds (NUMEVE
n and AGEEVE n settings) so that
changes to these points will be sent to the master quickly. You may then place
low priority data in event class 2 with higher thresholds.
If the SEL-751A does not receive an Application Confirm in response to
unsolicited data, it will wait for ETIMEO
n seconds and then repeat the
unsolicited message. In order to prevent clogging of the network with
unsolicited data retries, the SEL-751A uses the URETRY
n and UTIMEO n
settings to increase retry time when the number of retries set in URETRY n is
exceeded. After URETRY n has been exceeded, the SEL-751A pauses
UTIMEO n seconds and then transmits the unsolicited data again. Figure D.1
provides an example with URETRY n = 2.
Figure D.1 Application Confirmation Timing With URETRY n = 2
Unsolicited report-
by-exception Class 0 occasionally,
optional Class 1, 2, 3 less
frequently; mainly relies
on unsolicited messages Set ECLASSB n , ECLASSC n ,
ECLASSA n to the desired event class;
set UNSOL n to Yes and PUNSOL n to
Yes or No
Quiescent Class 0, 1, 2, 3 never;
relies completely on
unsolicited messages Set ECLASSB n , ECLASSC n ,
ECLASSA n to the desired event class;
set UNSOL n and PUNSOL n to Yes.
Table D.5 DNP3 Access Methods (Sheet 2 of 2)
Access Method Master Polling SEL-751A Settings
RX DATA
(Event Data Confirmation)
TX DATA
ETIMEOn
Retry Retry Retry
Confirmation
UTIMEOn
UTIMEOn ETIMEOn