Electro Industries 1252, Installation And Operation Manual

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Electro Industries/GaugeTech
Doc # E107706 V1.2 5
4-2
Q
It is important to maintain the polarity of the CT circuit when connecting to the Nexus. If the
polarity is reversed, the Nexus will not provide accurate readings. CT polarities are dependent upon
correct connection of CT leads and the direction CTs are facing when clamped around the
conductors. EIG recommends using shorting blocks to allow removal of the Nexus Meter from an
energized circuit, if necessary. Shorting blocks are not required for proper meter operation.
4.6: Isolating a CT Connection Reversal
Q For a WYE System, you may either:
1. Check the current phase angle reading on the Nexus External Display (see Chapter 6). If it is
negative, reverse the CTs.
2. Or, go to the Phasors screen of the Communicator EXT software (see Communicator EXT
User Manual ). Note the Phase Relationship between the Current and Voltage; they should be in
phase.
Q
For a DELTA System:
Go to the Phasors screen of the Communicator EXT software program. The current should be
30 degrees off the phase-to-phase voltage.
4.7: Instrument Power Connections
Q The Nexus requires a separate power source. To use AC power, connect the line supply wire to the
L+ terminal and the neutral supply wire to the N- terminal on the Nexus. To use DC power, connect
the positive supply wire to the L+ terminal and the negative (ground) supply wire to the N- terminal
on the Nexus. Power supply options and corresponding suffixes are listed in the following table:
CT Size (VA) Maximum Distance from CT to Nexus (Feet)
2.5 10
5.0 15
7.5 30
10.0 40
15.0 60
30.0 120
EIG Recommendations
W WA AR RN NIIN NG G!!!!
DO NOT leave the secondary of the CT open when primary current is flowing. This may
cause high voltage, which will overheat the CT. If the CT is not connected, provide a
shorting block on the secondary of the CT.