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Section 7
Current protection
[ ]
=
t s
EQUATION1261 V2 EN-US
tPRCrvx , tTRCrvx , tCRCrvx : These parameters are used by the customer to create the inverse
reset time characteristic curve. For more information, refer to
HarmRestrainx : Enables the block of step x from the harmonic restrain function (2nd
harmonic). This function should be used when there is a risk of an unwanted trip caused by
power transformer inrush currents. It can be set to
7.1.3.2
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 operating 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 88.
Current (A)
IEC05000203 V4 EN-US
Figure 88: Operate and reset current for an overcurrent protection
The lowest setting value can be written according to Equation 25.
148
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A
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B
IxMult
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p
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i
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C
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in
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Operate current
Reset current
The IED does not reset
Technical manual .
Off / On .
GUID-20729467-24AB-42F0-9FD1-D2959028732E v1
Line phase current
Time (s)
IEC05000203-en-2.vsd
Busbar protection REB670
1MRK 505 370-UEN D
(Equation 24)
Application manual
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