GE 239 Instruction Manual page 62

4 PROGRAMMING
When enabled, by programming setpoint 6 3527(&7,21?3+$6( &855(17?3+$6( 6&?3+$6( 6?& 75,3
75,3
, short circuit protection is active at all times, including during motor starts. It can be disabled
by setting the setpoint 6 3527(&7,21?3+$6( &855(17?3+$6( 6&?3+$6( 6?& 75,3 2)) .
• PHASE S/C PICKUP: The phase current short circuit trip level can be set from 1 to 11 times the
phase CT primary. When any phase current meets or exceeds this setpoint value during start or
run conditions and is maintained for the 3+$6( 6& '(/$< setpoint, the selected relay(s) will acti-
vate.
• PHASE S/C DELAY: The trip can be instantaneous (no intentional delay) or can be delayed by
up to 60000 ms to prevent nuisance tripping or allow co-ordination with associated system
switchgear. The 6 3527(&7,21?3+$6( &855(17?3+$6( 6&?3+$6( 6?& '(/$< setpoint represents the
intentional delay added to the detection and output relay activation delays of the 239. When this
setpoint is set to ,167 the 239 will trip within 45 ms of the onset of the short circuit. Both the short
circuit trip level and time delay should be set to co-ordinate with other system protective relays to
minimize equipment shutdown during a high current fault.
c) IMMEDIATE OVERLOAD
4
• IMMEDIATE OVERLOAD ALARM: When the average phase current exceeds the full load cur-
rent (FLC) setpoint the phase timed overload protection begins timing. This will eventually lead to
a trip unless the overload disappears. Immediate overload warning can be used to alert an oper-
ator or to produce an alarm output using this setpoint. This feature should be set to off for sys-
tems that experience overloads as part of normal operation such as crushers.
• IMMEDIATE OVERLOAD PICKUP: The immediate overload pickup setpoint is adjustable from
0.5 × FLC to 11.0 × FLC. The alarm relay will activate immediately when the average three phase
current exceeds this setpoint value when the motor is running. This feature can also operate dur-
ing start condition using the ,1+,%,7 21 67$57 )25 setpoint described below.
• INHIBIT ON START FOR: If all other conditions are met for an immediate overload alarm to
occur and the motor is starting, the alarm will occur when the delay set in this setpoint has
elapsed. If this setpoint is set to 81/,0,7(' , the immediate overload alarm will never occur during
a start.
d) MECHANICAL JAM
• MECHANICAL JAM FUNCTION: In protecting driven equipment such as pumps, gearboxes,
compressors and saws, it is often desirable to have an immediate trip in the event of a locked
rotor during running. During startup the mechanical jam can be disabled using the ,1+,%,7 21
67$57 )25 setpoint described below, since a typical inrush of 600% is normal. Use of this feature
with loads that experience overloads as part of normal operation such as crushers is not recom-
mended.
• MECHANICAL JAM PICKUP: If a fast trip for mechanical jam is required, enable the feature and
enter the average current pickup value above the normal maximum expected operating average
phase current.
MECHANICAL JAM DELAY: If the average phase current exceeds the 0(&+$1,&$/ -$0 3,&.83
•
setpoint value when the motor is running, and remains this way for the time delay programmed,
one of the assigned relay(s) will activate. Since the mechanical jam function can be assigned to
any relay, if 75,3 , $8;,/,$5< , or 75,3
trip and the "CAUSE OF LAST TRIP: MECHANICAL JAM" message will be displayed. Con-
versely, if the function is assigned to ALARM, and the above conditions are met, the fault is con-
sidered to be an ALARM, and the 239 will display "MECHANICAL JAM ALARM".
4-24
Courtesy of NationalSwitchgear.com
$8; 5(/$<6 are assigned, the function is considered to be a
239 Motor Protection Relay
4 PROGRAMMING
GE Multilin