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3–6 EPM 5300 SERIES ADVANCED POWER METERS – INSTRUCTION MANUAL
CT CONNECTION CHAPTER 3: ELECTRICAL INSTALLATION
3.2 CT Connection
If the meter is connected directly to the current (up to 10 Amps max.), maintain the exact
connection to avoid incorrect polarity.
When the meter is connected using the CTs, you must maintain the correct CT polarities. CT
polarities are dependent upon correct connections of CT leads, and upon the direction the
CTs are facing when clamped around conductors. The dot on the CT must face the line
side; the corresponding secondary connection must connect to the appropriate input on
the meter. Failure to connect CTs properly results in inaccurate power readings. If your
meter is not reading power properly, it is more than likely the CT is incorrectly wired.
Note
CTs are shorted if connected to the terminal block model DSP2 or 3 even if it is detached
from the meter.
3.2.1 Helpful Debugging Tools
Option 1: Isolating a CT Connection Reversal power reading
If your meter does not read the correct watts after installation, it almost always means
that the CT’s have been wired in the wrong polarity. To check the polarity of the CT after the
monitor has been installed, look at the single phase WATT readings to see that each of the
readings are positive (assuming you are consuming power). If one of the WATT readings is
negative, that particular phase CT is reversed.
To check the single phase WATT reading, press the Power button twice while the
annunciator is positioned to WATTS. Then press the Phase/Next button to cycle through
the phases. After connecting the polarity of the CTs, the WATT and VAR readings should be
correct.
Option 2: Isolating a CT Connection Reversal using Voltage Readings
Z KW reading. It should be positive.
Z If negative, reverse the CT wires on terminals 8 and 9.
Z Connect terminal number 6 potential. If KW decreases to about
zero, reverse CT wires on terminals 10 and 11.
Z Connect terminal number 7 potential. If KW is one-third of
expected reading, reverse CT wires to terminals 12 and 13.