ABB Relion 670 Series Applications Manual page 128

Section 8
Current protection
For IEC inverse time characteristics, the possible delay time settings are instantaneous (1) and IEC
(2 = set constant time reset).
For the customer tailor-made inverse time delay characteristics (type 17), all three types of reset
time characteristics are available: instantaneous (1), IEC (2 = set constant time reset) and ANSI (3 =
current dependent reset time). If the current-dependent type is used, settings
be given.
tResetx : Constant reset time delay in seconds for step x.
tPCrvx , tACrvx , tBCrvx , tCCrvx : These parameters are used by the customer to create the inverse
time characteristic curve. See equation
information, refer to
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ANSI-EQUATION1261 V1 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
8.1.3.2 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 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 55.
122
Technical manual .
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35 for the time characteristic equation. For more
Technical manual .
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1MRK 511 407-UUS Rev. J
pr , tr and cr must
(Equation 35)
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Phasor measurement unit RES670
Application manual