Electro-Voice 250, 1252 Isolating a CT Connection Reversal, Instrument Power Connections

	EIG Recommendations
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

WARNING!!

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.

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

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.

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

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:

Electro Industries/GaugeTech Doc # E107706 V1.25 4-2