2.4
SEL-749M Relay Instruction Manual Date Code 20080918
Installation
I/O Configuration
Communications Card. Either the DeviceNet™ (see Appendix E:
DeviceNet) or the EIA-232/ EIA-485 communications card is supported
in Slot C. The EIA-232 / EIA-485 card provides one serial port with one of
the following two serial port interfaces:
➤ Port 4A, an isolated EIA-485 serial port interface
➤ Port 4C, nonisolated EIA-232 serial port interface, supporting
the +5 Vdc interface
Select either EIA-232 or EIA-485 functionality using the Port 4 setting
COMM interface. Table 2.3 shows the port number, interface, and type of
connector for the two protocols.
The communications card supports the following protocols:
➤ Modbus RTU Slave
➤ SEL ASCII and Compressed ASCII
➤ SEL Fast Meter
➤ SEL Fast Operate
➤ SEL Fast SER
➤ SEL Fast Message Unsolicited Write
➤ SEL Settings File Transfer
Voltage Card. Supported in Slot E only, order this card when you have
three-phase (wye or delta) PTs. With a voltage card installed, the
SEL-749M tracks the frequency (using positive-sequence voltage) and
samples at 16 times a cycle, see Processing Specifications on page 1.10
for more information.
Current Card. Supported in Slot Z only, this card provides current inputs
for three-phase CTs and one neutral CT. Secondary phase current ratings
are either all 1 A or all 5 A; you cannot order a combination of 1 A and
5 A phase CTs on one card. However, the phase CTs and the neutral CT
can be of different current rating. You can order one of two neutral CT
ratings, 1 A or 5 A. With a current card installed, the SEL-749M tracks
the frequency (using positive-sequence current) and samples at 16 times a
cycle—see Processing Specifications on page 1.10 for more information.
able 2.3 Communications Card Interfaces and Connectors
Port Interface Connectors
4A EIA-485 5-pin Euro
4C EIA-232 D-sub
NOTE: The relay tracks the
frequency if 3V1 is greater than
0.75 V.
Table 2.4 Voltage Card Terminal Designation
Te r mi n a l N u m b e r Description
01 VA, Phase A voltage input
02 VB, Phase B voltage input
03 VC, Phase C voltage input
04 N, Common connection for VA, VB, VC
NOTE: The relay uses 3I1 to track the
frequency if 3V1 is not available and
3I1 is greater than 0.25 A (5 A) or
0.05 A (1 A).
Courtesy of NationalSwitchgear.com
To Next Page
Loading...
