GE Multilin G650, Manual

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GEK-113285A G650 Generator Protection & Control System 1-17
1 GETTING STARTED 1.4 650 HARDWARE
1
1.4650 HARDWARE 1.4.1 MOUNTING & WIRING
Please refer to Chapter 3. Hardware for detailed mounting and wiring instructions.
1.4.2 650 COMMUNICATIONS
The Enervista 650 Setup software communicates to the relay via the faceplate RS232 port or the rear RS485/Ethernet
ports. To communicate via the faceplate RS232 port, a standard “straight-through” serial cable is used. The DB-9 male end
is connected to the relay and the DB-9 or DB-25 female end is connected to the PC COM1 or COM2 port as described in
Figure 1–16:.
To communicate through the G650 rear RS485 port from a PC RS232 port, the GE Multilin RS232/RS485 converter box is
required. This device (catalog number F485) connects to the computer using a “straight-through” serial cable. A shielded
twisted-pair (20, 22 or 24 AWG according to American standards; 0.25, 0.34 or 0.5 mm2 according to European standards)
connects the F485 converter to the G650 rear communication port.
In order to minimize communication errors that could be caused by external noise, it is recommended to use a shielded
twist pair. In order to avoid loops where external currents could flow, the cable shield must be grounded only at one end.
The converter box (-, +, GND) terminals are connected to the relay (SDA, SDB, GND) terminals respectively. For long
communications cables (longer than 1 km), the RS485 circuit must be terminated in an RC network (i.e. 120 ohm, 1 nF).
This circuit is shown on Figure 1–17: RS485 CONNECTION FOR 650 UNITS, associated to text Zt(*).
Figure 1–16: RELAY- PC CONNECTION FOR RS232 FRONT PORT
To minimize errors from noise, the use of shielded twisted pair wire is recommended. For correct operation, polarity must
be respected, although a different polarity will not damage the unit. For instance, the relays must be connected with all
RS485 SDA terminals connected together, and all SDB terminals connected together. This may result confusing
sometimes, as the RS485 standard refers only to terminals named “A” and “B”, although many devices use terminals
named “+” and “-“.
As a general rule, terminals “A” should be connected to terminals “-“, and terminals “B” to “+”. The GND terminal should be
connected to the common wire inside the shield, when provided. Otherwise, it should be connected to the shield. Each
relay should also be daisy chained to the next one in the link. A maximum of 32 relays can be connected in this manner