2 INSTALLATION
2-15
2.6 Ground CT Input
All current carrying conductors must pass through a
separate ground fault CT in order for the ground fault
function to operate correctly. If the CT is placed over
a shielded cable, capacitive coupling of phase current
into the cable shield during motor starts may be
detected as ground current unless the shield wire is
also passed through the CT window; see Figure 2.9a.
If a safety ground is used it should pass outside the
CT window; see Figure 2.9b.
The connections to the 269 internal ground CT are
made directly via #10 screws. The ground CT is
connected to terminals 73 and 72 for a 5 amp
secondary CTs, or to terminals 73 and 74 for a GE
Multilin 50:0.025A (2000:1 ratio) CTs, as shown in
Figure 2.4, Figure 2.5, and Figure 2.7. The polarity of
the ground CT connection is not important. It is
recommended that the two CT leads be twisted
together to minimize noise pickup. If a 50:0.025A
(2000:1 ratio) ground CT is used, the secondary
output will be a low level signal which allows for
sensitive ground fault detection.
NOTE: The GE Multilin 2000:1 CT is actually a
50:0.025A CT recommended for resistance
grounded systems where sensitive ground fault
detection is required. If higher levels are to be
detected, a 5 Amp secondary CT should be used.
For a solidly grounded system where higher ground
fault currents will flow, a 5 amp secondary CT with a
primary between 20 and 1500 A may be used to
surround all phase conductors. The phase CTs may
also be residually connected to provide ground
sensing levels as low as 10% of the phase CT
primary rating. For example, 100:5 CTs connected in
the residual configuration can sense ground currents
as low as 10 amps (primary) without requiring a
separate ground CT. This saves the expense of an
extra CT, however 3 phase CTs are required. If this
connection is used on a high resistance grounded
system verify that the ground fault alarm and trip
current setpoints are below the maximum ground
current that can flow due to limiting by the system
ground resistance. Sensing levels below 10% of the
phase CT primary rating is not recommended for
reliable operation.
When the phase CTs are connected residually, the
secondaries must be connected in such a way to
allow the 269 to sense any ground current that might
be flowing. To correctly display ground current and
trip or alarm on ground fault, the connection to the
269 must be made at terminals 72 and 73 as shown
in Figure 2.4 and Figure 2.7. These terminals are
designed to accept input from a 5A secondary CT.
The 269 must also be programmed for a 5A
secondary ground CT with the primary being equal to
the phase CT primary. This is done in SETPOINTS,
page 1.
2.7 Trip Relay Contacts
The main control relay or shunt trip coil of the motor
starter or circuit breaker should be connected to the
Trip relay contacts of the 269. These contacts are
available as normally open (NO), normally closed
(NC), and can switch up to 10 amps at either 250
VAC or 30 VDC with a resistive load. Silver cadmium
oxide contacts are used because of their ability to
handle high inrush currents on inductive loads.
Contact GE Multilin if these contacts are to be used
for carrying low currents since they are not
recommended for use below 0.1 amps. Connection to
the motor contactor or breaker is shown in Figure 2.4,
Figure 2.5, and Figure 2.7.
The Trip output relay will remain latched after a trip.
This means that once this relay has been activated it
will remain in the active state until the 269 is manually
reset. The Trip relay contacts may be reset by
pressing the RESET key (see section 3.1) if motor
conditions allow, or by using the Emergency Restart
feature (see section 2.12), or the External Reset
terminals, or by remote communications via the
RS485 port.
The Trip relay may be programmed to be fail-safe or
non-fail-safe. When in the fail-safe mode, relay
activation or a loss of power condition will cause the
relay contacts to go to their power down state. Thus,
in order to cause a trip on loss of power to the 269,
output relays should be programmed as fail-safe.
The Trip relay cannot be reset if a lock-out is in effect.
Lock-out time will be adhered to regardless of
whether control power is present or not. A maximum
of one hour lockout time is observed if control power
is not present.
The Trip relay can be programmed to activate on any
combination of the following trip conditions: overload,
stator RTD overtemperature, rapid trip, unbalance,
ground fault, short circuit, RTD overtemperature,
acceleration time, number of starts per hour, single
phase (see section 3.4 for factory preset
configurations).
Connections to the Trip relay contacts are made via a
terminal block which uses #6 screws.
NOTE: The rear of the 269 relay shows output relay
contacts in their power down state. Figure 2.4, Figure
2.6, and Figure 2.7 show output relay contacts with
power applied, no trips or alarms, and Factory
Configurations in effect (i.e. TRIP - fail-safe, ALARM -
non-fail-safe, AUX.1 - non-fail-safe, AUX.2 - fail-safe).
See Figure 2.5 for a list of all possible contact states.
WARNING: In locations where system voltage
disturbances cause voltage levels to dip below
the range specified in the Specifications (1.5), any
relay contact programmed failsafe may change
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