ABB RELION REF615R, Technical Manual

Page: 640 / 664

It is recommended to enable biasing only at one end of the bus.
Termination is enabled at each end of the bus.
It is recommended to ground the signal directly to ground from one node
and through capacitor from other nodes.
The two 2-wire ports are called COM1 and COM2. Alternatively, if there is only one 4-
wire port configured, the port is called COM2. The fiber-optic ST connection uses the
COM1 port.
Table 451: EIA-485 connections for COM0001-COM0014
Pin 2-wire mode 4-wire mode
10 COM1 A/+ COM2 Rx/+
9 B/- Rx/-
8 COM2 A/+ Tx/+
7 B/- Tx/-
6 AGND (isolated ground)
5 IRIG-B +
4 IRIG-B -
3 -
2 GNDC (case via capacitor)
1 GND (case)
14.3.7.2 COM0023 jumper locations and connections
The optional communication module supports EIA-232/EIA-485 serial communication
(X6 connector), EIA-485 serial communication (X5 connector) and optical ST serial
communication (X12 connector).
Two independent communication ports are supported. The two 2-wire ports are called
COM1 and COM2. Alternatively, if only one 4-wire port is configured, the port is called
COM2. The fibre-optic ST connection uses the COM1 port.
Section 14
1MRS240050-IB C
Protection relay's physical connections
634 REF615R
Technical Manual