Schweitzer Engineering Laboratories SEL-751 - AC;DC Control Connection Diagrams; Figure 2.17 Analog Output Wiring Example; Table 2.18 Typical Maximum RTD Lead Length; Figure 2.18 Output OUT103 Relay Output Contact Configuration

2.26
SEL-751 Relay Instruction Manual Date Code 20170927
Installation
AC/DC Control Connection Diagrams
Table 2.18 shows the maximum cable lengths for the RTD connections.
Analog Output Wiring
Connect the two terminals of the analog output as shown in Figure 2.17. Also
connect the analog output cable shield to ground at the relay chassis ground,
programmable logic controller (PLC), or meter location. Do not connect the
shield to ground at both locations.
Figure 2.17 Analog Output Wiring Example
AC/DC Control Connection Diagrams
This section describes fail-safe versus nonfail-safe tripping, describes voltage
connections, and provides the ac and dc wiring diagrams.
Fail-Safe/Nonfail-Safe
Tripping
Figure 2.18 shows the output OUT103 relay coil and Form C contact. When the
relay coil is de-energized, the contact between A07 and A08 is open while the
contact between A07 and A09 is closed.
Figure 2.18 Output OUT103 Relay Output Contact Configuration
Table 2.18 Typical Maximum RTD Lead Length
RTD Lead AWG Maximum Length (meters)
26 184 m
24 290 m
22 455 m
20 730 m
18 1155 m
NOTE: RTD inputs are not internally
protected for electrical surges
(IEC 60255-22-1 and IEC 60255-22-5).
External protection is recommended
if you want surge protection.
NOTE: Connection of dc voltage to
the analog output terminals could
result in damage to the relay.
Analog Output
Relay Chassis Ground
Meter
or
PLC
AO_0 1
02
01
Contacts shown with
OUT103 relay coil de-energized
A07
A08 A09
OUT103
Relay Coil
NOTE: Fast hybrid contacts are
designed for fast closing (50 s) only.
Fail-safe mode operating time (time
to open the contacts) for fast-hybrid
contacts is <8 ms (the same time as
for a normal output contact).