GE Multilin
C70 Capacitor Bank Protection and Control System
3-23
3 HARDWARE
3.2 WIRING
3
Figure 3–23: CPU MODULE COMMUNICATIONS WIRING
b) RS485 PORTS
RS485 data transmission and reception are accomplished over a single twisted pair with transmit and receive data alternat-
ing over the same two wires. Through the use of the port, continuous monitoring and control from a remote computer,
SCADA system, or PLC is possible.
To minimize errors from noise, the use of shielded twisted pair wire is recommended. Correct polarity must also be
observed. For instance, the relays must be connected with all RS485 “+” terminals connected together, and all RS485 “–”
terminals connected together. Though data is transmitted over a two-wire twisted pair, all RS485 devices require a shared
reference, or common voltage. This common voltage is implied to be a power supply common. Some systems allow the
shield (drain wire) to be used as common wire and to connect directly to the C70 COM terminal (#3); others function cor-
rectly only if the common wire is connected to the C70 COM terminal, but insulated from the shield.
To avoid loop currents, ground the shield at only one point. If other system considerations require the shield to be grounded
at more than one point, install resistors (typically 100 ohms) between the shield and ground at each grounding point. Each
relay needs to be daisy-chained to the next one in the link. A maximum of 32 relays can be connected in this manner with-
out exceeding driver capability. For larger systems, additional serial channels must be added. It is also possible to use com-
mercially available repeaters to have more than 32 relays on a single channel. Avoid star or stub connections entirely.
842722A3.CDR
100Base-T
COMMON
+
+
—
—
D1a
D2a
D3a
D4b
D4a
BNC
IRIG-B
input
CPU
V
Co-axial cable
Shielded
twisted-pairs
Ground at
remote
device
RS485
COM2
100Base-T
100Base-T
COMMON
+
+
—
—
D1a
D2a
D3a
D4b
D4a
BNC
IRIG-B
input
CPU
U
Co-axial cable
Shielded
twisted-pairs
Ground at
remote
device
RS485
COM2
100Base-T
100Base-FX
Port 1
Port 2
100Base-FX
Tx1
Rx1
COMMON
+
+
—
—
D1a
D2a
D3a
D4b
D4a
BNC
IRIG-B
input
CPU
T
Co-axial cable
Shielded
twisted-pairs
MM fiber-
optic cable
Ground at
remote
device
RS485
COM2
100Base-FX
100Base-FX
Tx2
Rx2
Tx3
Rx3
Tx1
Rx1
Port 3
Port 1
Port 2
Port 3
Port 1
Port 2
Port 3
100Base-FX
Tx1
Rx1
Summary of Contents for C70
Page 10: ...x C70 Capacitor Bank Protection and Control System GE Multilin TABLE OF CONTENTS ...
Page 394: ...5 270 C70 Capacitor Bank Protection and Control System GE Multilin 5 10 TESTING 5 SETTINGS 5 ...
Page 676: ...E 10 C70 Capacitor Bank Protection and Control System GE Multilin E 1 OVERVIEW APPENDIX E E ...
Page 698: ...H 8 C70 Capacitor Bank Protection and Control System GE Multilin H 3 WARRANTY APPENDIX H H ...