GE 239 Instruction Manual page 48

4 PROGRAMMING
a) CT INPUTS
At 3+$6( &7 35,0$5< !  $ , the 239 shifts the 02725 )8// /2$' &855(17 settings by a
factor of 10 to remove the extra decimal place (see Figure 4–3: SETPOINTS PAGE 2
– SYSTEM SETUP above). If changing the 3+$6( &7 35,0$5< setting causes it to
cross the 50 A value, the 02725 )8// /2$' &855(17 is reset to 0 A, forcing the opera-
NOTE
tor to restore the correct value. In previous firmware versions, crossing the 50 A
value by changing the 3+$6( &7 35,0$5< setting changed the 02725 )8// /2$' &855(17
setting by a factor of 10 automatically, often without the operator's knowledge.
• PHASE CT PRIMARY: Enter the primary current rating of the phase current transformers. All
three phase CTs must be of the same rating. For example if 500:5 CTs are used, the phase CT
primary value entered should be 500. When the relay is shipped with factory defaults loaded, the
phase CT ratio is set off. When off is the CT value, the 239 is forced to a trip state as a safety pre-
caution until a valid CT value is entered. Ensure that the CT is connected to the correct 1 A or 5
A terminals to match the CT secondary.
• GROUND SENSING: Ground sensing on solid or low resistance grounded systems is possible
with residually connected phase CTs as shown in Figure 2–3: TYPICAL WIRING DIAGRAM on
4
page 2–4. If this connection is used enter residual. The ground CT primary will automatically be
the same as the phase CTs. For more sensitive ground current detection a separate core bal-
ance (zero sequence) CT which encircles all three phase conductors can be used. In this case
select core balance 50:0.025. A GE Multilin 50:0.025 CT is available. If a conventional 5 A sec-
ondary CT is used to encircle the 3 phase conductors, enter core balance x:5. It is then neces-
sary to specify the CT primary using the next message *5281' &7 35,0$5< .
• GROUND CT PRIMARY: This message will only be visible if the ground sensing in the previous
message is selected as core balance x:5. Enter the CT primary current. For example, if a 50:5
CT is installed for ground sensing enter 50. One amp CTs can also be used for ground sensing.
In this case enter the CT primary value multiplied by 5. For example, if a 100:1 ground CT is
installed and the ground sensing is selected as core balance x:5 enter 500 for the primary value.
• NOMINAL FREQUENCY: Enter the nominal system frequency as either 50 or 60 Hz. The 239
uses this information in the detection of Phase Short Circuit and Ground Fault Trips.
b) MOTOR DATA
• MOTOR FULL LOAD CURRENT (FLC): Enter the full load amps from the motor nameplate.
This is the maximum rated current at which the motor can operate without overheating. It is the
1.0× pickup point on the timed overcurrent characteristic. When the current exceeds this value,
the timed overcurrent feature begins to time, eventually leading to a trip. Immediate overload
warning and undercurrent setpoints are multiples of this value. Timed overcurrent is not active
during motor starting.
• OVERLOAD PICKUP INHIBIT: Enter the overload pickup (service factor) specified on the motor
nameplate if shown. Otherwise enter an overload pickup of 1.00. The pickup inhibit will operate
during start and/or run depending upon the value programmed in the setpoint 86( 29(5/2$'
3,&.83 ,1+,%,7 21 described below. During a running condition this value adjusts the pickup at
which the overload curves begin timing. If the overload pickup is 1.15 for example, the overload
curves will not begin to operate until the phase current reaches 1.15 × FLC. During a start, 6$)(
67$// 7,0( and /2&.(' 52725 &855(17 setpoints will not be used until the current reaches the
overload pickup inhibit setting.
This setpoint acts as a lower cutoff for the overload pickup. The trip times are not shifted, but just
cut-off below the value specified by the overload pickup inhibit setting.
4-10
Courtesy of NationalSwitchgear.com
239 Motor Protection Relay
4 PROGRAMMING
GE Multilin