Rockwell Automation 1402-LSM Line Synchronization Module Installation Instructions - Manual (Page 14)

Chapter 2
Installation
2–4
Other factors may affect CT accuracy. The length of the CT cabling should
be minimized because long cabling could contribute to excessive power load
on the CT and inaccuracy. The CT burden rating must exceed the combined
burden of the LSM plus cabling plus any other devices connected in the
measuring circuit (burden is the amount of load being fed by the CT,
measured in Volt–Amps calculated at 5A full scale.).
Overall accuracy is dependent on the combined accuracy of the Bulletin
1402, the CT’s, and the PT’s. Instrument accuracy Class 1 or better is
recommended.
!
ATTENTION: A CT circuit must not be opened under power.
Wiring between the CT’s and the LSM should include a terminal
block for shorting the CT’s. Open CT’s secondaries can produce
hazardous voltages, which can lead to personal injury or death,
property damage or economic loss.
Connection for Three Phase WYE (Star), 4 Wire Systems
Figure 2.1 shown on Page 2–7 provides a wiring diagram for 4–wire WYE
(Star) systems. The “Voltage Mode” of the LSM should be set to “1” (as
described in Chapter 3, “General Operation”) for 4–wire WYE systems.
The LSM senses the line to neutral (or ground) voltage of each phase. The
PT primaries and secondaries must be wired in a WYE (Star) configuration
as shown in the figure. Voltage input leads should be protected by circuit
breakers or fuses at their source. If the power rating of the PT’s is over 25
Watts, secondary fuses should be used. Wiring and polarity marks must be
exactly as shown for correct operation.
Connection for Three Phase WYE (Star), 3 Wire Systems
Figure 2.2 shown on Page 2–8 provides a wiring diagram for 3–wire WYE
(Star) systems. The “Voltage Mode” of the LSM should be set to “1” (as
described in Chapter 3, “General Operation”) for 3–wire WYE systems.
The LSM senses the line to neutral voltage of each phase. The PT primaries
and secondaries must be wired in a WYE (Star) configuration as shown in
the figure. Voltage input leads should be protected by circuit breakers or
fuses at their source. If the power rating of the PT’s is over 25 Watts,
secondary fuses should be used. Wiring and polarity marks must be exactly
as shown for correct operation.
PT and CT Wiring Connections