ABB RES670 Technical Manual page 890

Section 26
Inverse time characteristics
884
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-US
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 346.
×
A td
is the first protection execution cycle when a fault has been
detected, that is, when
i
>
1
Pickupn
EQUATION1646 V1 EN-US
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 511 408-UUS A
Phasor measurement unit RES670 2.2 ANSI
Technical manual
(Equation 90)