Sel 751A, Instruction Manual

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D.6
SEL-751A Relay Instruction Manual Date Code 20100129
DNP3 Communications
DNP3 in the SEL-751A
➤
TCP is strongly recommended for LANs
➤
User Datagram Protocol (UDP) may be used for highly reliable
single segment LANs
➤
UDP is necessary if broadcast messages are required
➤
The DNP3 protocol stack shall be retained in full
➤
Link layer confirmations shall be disabled
The Technical Committee has registered a standard port number, 20000, for
DNP3 with the Internet Assigned Numbers Authority (IANA). This port is
used for either TCP or UDP.
TCP/UDP Selection
The Committee recommends the selection of TCP or UDP protocol as per the
guidelines in
Table D.4 .
DNP3 in the SEL-751A
The SEL-751A is a DNP3 Level 2 remote (slave) device.
Data Access
Table D.5 lists DNP3 data access methods along with corresponding
SEL-751A settings. You must select a data access method and configure each
DNP3 master for polling as specified.
Table D.4 TCP/UDP Selection Guidelines
Use in the case of… TCP UDP
Most situations X
Non-broadcast or multicast X
Mesh Topology WAN X
Broadcast X
Multicast X
High-reliability single-segment LAN X
Pay-per-byte, non-mesh WAN, for example, Cellular Digital Packet Data
(CDPD) X
Low priority data, for example, data monitor or configuration information X
Table D.5 DNP3 Access Methods (Sheet 1 of 2)
Access Method Master Polling SEL-751A Settings
Polled static Class 0 Set ECLASSB n , ECLASSC n ,
ECLASSA n to 0; UNSOL n to No
Polled report-by-
exception Class 0 occasionally,
Class 1, 2, 3 frequently Set ECLASSB n , ECLASSC n ,
ECLASSA n to the desired event class;
UNSOL n to No
NOTE:
Because unsolicited
messaging is problematic in most
circumstances, SEL recommends
using the polled report-by-exception
access method to maximize
performance and minimize risk of
configuration problems.
NOTE:
In the settings in Table D.5 ,
the suffix n represents the DNP3
session number from 1 to 3. All
settings with the same numerical
suffix comprise the complete DNP3
session configuration.