ABB REU 610 Technical Reference Manual page 121

1MRS755972
Voltage Relay
Technical Reference Manual - ANSI Version
RS-485 connection for the DNP 3.0 communication module
If the relay is provided with the optional DNP 3.0 communication module,
the cable is connected to terminals X5.8/1-2 and X5.8/4-8. The connection
socket is a 8-pin header-type socket and the terminals are of screw
compression type.
The DNP communication module follows the DNP standard and is intended
to be used in a daisy-chain bus wiring scheme with 2- or 4-wire, half-duplex,
multi-point communication.
The maximum number of devices (nodes) connected to the bus
where the relay is being used is 32, and the maximum length of
the bus is 1200 meters in optimum conditions and with slow
communication speed.
When connecting the relay to the bus, a quality twisted pair shielded cable is
to be used. The conductors of the pair are connected to A and B. If signal
ground is being used for balancing potential differences between devices/
nodes, a quality dual twisted pair shielded cable is to be used. In this case, one
pair is connected to A and B, and one of the conductors of the other pair to
signal ground. When connecting one device to another, A is connected to A
and B to B.
When using a 4-wire bus, one pair is connected to +RX and -RX and the
other to +TX and -TX. If signal ground is being used, a quality cable with
three or several pairs is to be used and one of the conductors of a pair
connected to signal ground.
The cable shield is to be connected directly to ground (shield GND) in one
point/device of the bus. Other devices connected to the bus should have the
cable shield connected to ground via a capacitor (shield GND via capacitor).
Signal ground can only be used for balancing potential
differences between devices/nodes if all devices connected to the
bus have isolated DNP interfaces.
The DNP communication module is provided with jumpers for setting bus
termination and fail-safe biasing. The bus is to be terminated at both ends,
which can be done by using the internal termination resistor on the DNP
communication module. The termination resistor is selected by setting jumper
X6 or/and X12 to the ON position. If the internal termination resistor of 120Ω
is used, the impedance of the cable should be the same.
REU 610
121