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Secure the relay to the DIN rail ensuring the release latches at the bottom of the relay engage the rail. If the relay is to
be mounted in any other position take appropriate steps to prevent the relay from disengaging from the DIN rail.
9.1.3 Connections
Refer to Figure 9.1 for electrical connections to the Sigma monitor relay. Terminals on the relay will accept up to #14
AWG wire.
Connect the G terminal on the Sigma monitor relay to a suitable grounding point. Connect control power to terminals L
and N. An isolation transformer is recommended as the source of supply to prevent excessive voltage being applied to
the relay’s internal power supply.
This grounding point should be electrically common to the grounding point of the NGR.
The Sigma monitor relay must be grounded as described above. As the relay’s housing is non-metallic, no chassis
bond is required.
Connect the sensing resistor input terminals on the Sigma monitor relay to the R terminal of the NGRS-XX sensing
resistor as shown in the connection diagram below.
Connect terminals 47 & 48 on the Sigma monitor relay to the X1 and X2 terminals of the zero sequence current sensor
as shown in the connection diagram below.
Refer to the description of the trip relay operating mode settings for an explanation of the shunt (not failsafe) and un-
dervoltage (failsafe) operating modes and the relay contact states for each of these operating modes. The connection
of field devices to the terminals of the Sigma monitor relay must be as specified in the installation specifications. These
include the trip relay terminals, the auxiliary fault relay terminals, the external reset, test and the G/F meter terminals.
If door/panel mounted or remote test and/or reset controls are required, connect momentary single pole single throw
(SPST) normally open contact pushbuttons to the appropriate terminals on the Sigma monitor relay. Refer to the con-
nection diagram below. These contacts are to be voltage free.
If a panel/door mounted or remote ground fault meter is required, an I-Gard GM-AM1 type meter or a meter conform-
ing to specifications given in this document can be connected to the appropriate terminals on the Sigma monitor relay.
Refer to Figure 9.1. The I-Gard percentage ammeter is designed for use in this application. If a meter other than the
I-Gard GM-AM1 is used, observe the polarity shown on the front panel and in Figure 9.1.
9.2 Zero Sequence Current Sensor
9.2.1 Location
The ZSCS should be mounted near the system transformer neutral (whether a transformer or a generator) along with
the NGRS-XX sensing resistor and NGR.
9.2.2 Mounting
The overall dimensions of the T2A ZSCS are 104 mm x 104 mm x 44 mm. If another size zero sequence current sen-
sor is used please refer to document C-700EM sensors.
9.2.3 Connections
The neutral point of the system is to be connected to the ungrounded end of the neutral grounding resistor such that
this conductor passes through the window of the ZSCS.
The secondary terminals, X1 and X2, must be connected to the appropriate terminals on the Sigma monitor relay as
shown in the connection diagram below.
