GE 735

GE Power Management
735/737 Feeder Protection Relay 5-1
5 OVERCURRENT CURVES 5.1 OVERVIEW
5
5 OVERCURRENT CURVES 5.1 OVERVIEW 5.1.1 DESCRIPTION
This chapter lists the 3 possible curve types, and their corresponding curve shapes. They are listed as follows:
ANSI CURVES
• Moderately Inverse
•Normal Inverse
•Very Inverse
• Extremely Inverse
• Definite Time
IAC CURVES
• IAC Short Time
•IAC Inverse
• IAC Very Inverse
• IAC Extremely Inverse
• Definite Time
IEC/BS142 CURVES
• IEC Short Time
• IEC A (Normal Inverse)
• IEC B (Very Inverse)
• IEC C (Extremely Inverse)
• Definite Time
For the graphs shown in this chapter, the per unit value (on the x-axis) is given as:
where:
I = current input to relay
I
pu
= pickup current setpoint
CT = CT secondary, that is1 or 5 A
Per Unit
I
I
0
----
I
I
pu
100
⁄()
CT
×
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