ABB REU 610 Technical Reference Manual page 114

REU 610
114
Voltage Relay
Technical Reference Manual
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 earth (shield GND) in one point/
device of the bus. Other devices connected to the bus should have the cable shield
connected to earth 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.
The bus is to be biased at one end to ensure fail-safe operation, which can be done
using the pull-up and pull-down resistors on the communication module. The pull-
up and pull-down resistors are selected by setting jumpers X8, X7, X13 and X11 to
the ON position.
The 2-wire bus is selected by default (jumper X14) without termination or biasing.
The jumpers X6, X7, X8 and X12 are in OFF position. The jumpers X11 and X13
are in ON position.
1MRS755769