9.2.3.2 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
257.
Pickup current
Current I
The IED does not reset
Line phase current
Time t
Reset current
ANSI09000146-en-1.vsd
ANSI09000146 V1 EN
Figure 257: Pickup and reset current for an overcurrent protection
The lowest setting value can be written according to Equation 450.
1MRK 506 369-UUS - Section 9
Current protection
Line distance protection REL670 2.2 ANSI 499
Application manual
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