GE 869

4–176 869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION CHAPTER 4: SETPOINTS
Current Elements
Figure 4-64: Current Elements Display Hierarchy
Description
The relay has six setpoint groups with phase, neutral, and ground elements per group. The
programming of the time-current characteristics of these elements is identical in all cases
and is only covered in this section. The required curve is established by programming a
Pickup Current, Curve Shape, Curve Multiplier, and Reset Time. The Curve Shape can be
either a standard shape or a user-defined shape programmed with the FlexCurve feature.
Inverse Time
Overcurrent Curves
The Inverse Time Overcurrent Curves used by the Time Overcurrent elements are the IEEE,
IEC, GE Type IAC, ANSI, I
2
t and I
4
t standard curve shapes. This allows for simplified
coordination.
If none of these curve shapes is adequate, FlexCurves may be used to customize the
inverse time curve characteristics. The definite time curve is also an option that may be
appropriate if only simple protection is required.
Table 4-24: OVERCURRENT CURVE TYPES
A time dial multiplier setting allows the selection of a multiple of the base curve shape
(where the time dial multiplier = 1) with the curve shape setting. Unlike the
electromechanical time dial equivalent, operate times are directly proportional to the time
multiplier (TD MULTIPLIER) setting value. For example, all times for a multiplier of 10 are 10
times the multiplier 1 or base curve values. Setting the multiplier to zero results in an
instantaneous response to all current levels above Pickup.
Time Overcurrent time calculations are made with an internal energy capacity memory
variable. When this variable indicates that the energy capacity has reached 100%, a Time
Overcurrent element will operate. If less than 100% energy capacity is accumulated in this
variable and the current falls below the dropout threshold of 97 to 98% of the Pickup value,
Setpoints
Device
System
Inputs
Outputs
Protection
Monitoring
Control
FlexLogic
Data Capture
Group 1
Phase IOC
Phase TOC
Neutral TOC
Phase Directional OC
Neutral Directional OC
Neutral IOC
Ground IOC
Ground TOC
Level 1 Level 2 Level 3 Level 4
Data Capture
Power
Frequency
Voltage
Group 2
Group 3
Group 4
Group 5
Group 6
Current
Motor
Negative Sequence IOC
Testing
IEEE ANSI IEC GE TYPE IAC OTHER
IEEE Extremely
Inverse
ANSI Extremely
Inverse
IEC Curve A (BS
142)
IAC Extremely
Inverse
I
2
t
IEEE Very Inverse ANSI Very Inverse IEC Curve B (BS
142)
IAC Very Inverse I
4
t
IEEE Moderately
Inverse
ANSI Normally
Inverse
IEC Curve C (BS
142)
IAC Inverse FlexCurves A, B, C
and D
ANSI Moderately
Inverse
IEC Short Inverse IAC Short Inverse Definite Time