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Section 24
Inverse time characteristics
836
æ
ö
( )
n
P
æ
ö
å
i j
ç
÷
D ×
-
³
t
ç
÷
C
ç
÷
è
ø
Pickupn
è
ø
=
j
1
EQUATION1644 V1 EN
where:
j = 1
Dt
n
i (j)
For inverse time operation, the inverse time characteristic is selectable. Both the IEC and
ANSI/IEEE standardized inverse time characteristics are supported.
For the IEC curves there is also a setting of the minimum time-lag of operation, see
figure 329.
×
A td
is the first protection execution cycle when a fault has been detected,
that is, when
i
>
1
Pickupn
EQUATION1646 V1 EN
is the time interval between two consecutive executions of the
protection algorithm,
is the number of the execution of the algorithm when the trip time
equation is fulfilled, that is, when a trip is given and
is the fault current at time j
1MRK 511 365-UUS A
Phasor measurement unit RES670 2.1 ANSI
Technical manual
(Equation 87)
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