GE M60 UR Series

GE Multilin M60 Motor Protection System 5-163
5 SETTINGS 5.6 GROUPED ELEMENTS
5
d) AMP UNBALANCE
PATH: SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  MOTOR  AMP UNBALANCE 1(2)
This element receives current inputs from the source selected by the SETTINGS  SYSTEM SETUP  MOTOR  MOTOR
LINE SOURCE setting. Generally, this element compares the ratio of motor negative sequence current (I_2) to the positive
sequence current (I_1) times an adjustment factor to compensate for the actual motor load to a set threshold. The adjust-
ment factor is used to prevent nuisance alarms at light loads. If the motor is operating at an average current level equal to
or greater than the programmed full load current (FLA, as selected by the
SYSTEM SETUP  MOTOR  MOTOR FULL LOAD
AMPS setting) the adjustment factor is one. If the motor is operating at an average current level less than the programmed
full load current (as selected by the SYSTEM SETUP  MOTOR  MOTOR FULL LOAD AMPS setting) the adjustment factor is
the ratio of average current to full load current. It is intended that the Amp Unbalance 1 element is used to generate an
alarm and Amp Unbalance 2 element is used to generate a trip.
A declaration of a “single-phasing” condition is made 2 seconds after the unbalanced current level exceeds 40%, or the
average current is above 25% of FLA and the current in any one phase is less than 2% of FLA
• AMP UNBAL 1(2) PICKUP: This setting selects the level of unbalanced current that generates a stage 1 (intended to
alarm) output. Note that a supply voltage unbalance of 1% creates a current unbalance of 6% in a typical three-phase
induction motor; a supply voltage unbalance of 2% creates a current unbalance of 12%. As a 2% voltage unbalance is
common in most applications, a setting of 0.15 is often used as the alarm level, and
AMP UNBAL 1 PICKUP is usually set
to this level or higher.
• AMP UNBAL 1(2) PICKUP DELAY: The alarm delay is often set from 5 to 10 seconds. A higher level of unbalance will
cause motor stress in a shorter period; thus, a reasonable setting is 3 to 10 seconds.
• AMP UNBAL 1(2) RESET DELAY: This timer can be used to maintain the output until other equipment or an operator
can react to the unbalance condition.
 AMP UNBALANCE 1

AMP UNBAL 1
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
AMP UNBAL 1 PICKUP:
0.0%
Range: 0.0 to 100.0% in steps of 0.1
MESSAGE
AMP UNBAL 1 PICKUP
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
AMP UNBAL 1 RESET
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
AMP UNBAL 1 BLOCK:
Off
Range: FlexLogic operand
MESSAGE
AMP UNBAL 1 TARGET:
Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
AMP UNBAL 1 EVENTS:
Disabled
Range: Disabled, Enabled