Setting Example - ABB RELION RET670 Applications Manual

Section 9
Current protection
9.2.3.2
526

Setting example

Directional phase overcurrent protection, four steps can be used in different ways,
depending on the application where the protection is used. A general description is
given below.
The pickup current setting of the inverse time protection, or the lowest current step of
the definite time protection, must be defined so that the highest possible load current
does not cause protection operation. The protection reset current must also be
considered so that a short peak of overcurrent does not cause the operation of a
protection even when the overcurrent has ceased. This phenomenon is described in
Figure 262.
Current I
Pickup current
Reset current
The IED does not reset
ANSI09000146 V1 EN-US
Figure 262: Pickup and reset current for an overcurrent protection
The lowest setting value can be written according to Equation 422.
1MRK 504 163-UUS A
GUID-20729467-24AB-42F0-9FD1-D2959028732E v1
Line phase current
Time t
ANSI09000146-en-1.vsd
Transformer protection RET670 2.2 ANSI
Application manual