GE 845 User Manual

CHAPTER 4: SETPOINTS PROTECTION
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–153
Current Elements
Figure 4-52: Current Elements Display Hierarchy
Description
The relay has six setpoint groups. 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. Accurate coordination may require changing the
time overcurrent characteristics of particular elements under different conditions.
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 with downstream devices.
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 4-23: OVERCURRENT CURVE TYPES
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
Negative Sequence TOC
Ground Directional OC
Negative Sequence Dir. OC
Negative Sequence IOC
Level 1 Level 2 Level 3 Level 4
Restricted Ground Fault
Data Capture
Power
Frequency
Voltage
Group 2
Group 3
Group 4
Group 5
Group 6
Current
Transformer
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 Recloser Curve
Definite Time

GE 845 Specifications

General

Brand	GE
Model	845
Category	Protection Device
Language	English