ABB RER620 - Link Mode; COT Length; OA Length; Link Address Length

1MAC306892-MB C Section 3
Vendor-specific implementation
RER620 19
Communication Protocol Manual
3.6.6 Link mode
• Unbalanced
• Balanced (default)
1
The settings defines the link mode. In the unbalanced mode, the protective relay listens for
the client's commands and responds when needed. In the balanced mode, the protective
relay opens the connection and sends a spontaneous report when something happens.
3.6.7 COT length
• Min: 1
•Max: 2
• Default: 1
•Unit: bytes
Many communication frames include the cause of transmission information (COT). The
length of COT element is configurable and should be set to same value throughout the
network. Typical values are '1' for IEC 60870-5-101 and '2' for IEC 60870-5-104.
3.6.8 OA length
• Min: 1
•Max: 3
• Default: 2
•Unit: bytes
For the communication frames, the information object address (IOA) length is
configurable and should be set to the same value throughout the network. Typical values
are '2' for IEC 60870-5-101 and '3' for IEC 60870-5-104.
3.6.9 Link address length
• Min: 1
•Max: 2
• Default: 1
•Unit: bytes
In a communication frame, the destination address is defined. The length of a link address
element is configurable and should be set to same value throughout the network. Typical
values are '1' for IEC 60870-5-101 and '2' for IEC 60870-5-104.
1. STARTDT must always be sent before any user data transfer from the controlled station (for example,
general interrogated information) is initiated. Any pending user data in the controlled station is sent
only after the STARTDT con