ABB RELION 670 Series Technical Manual page 1391

1MRK 502 066-UUS B
æ
n
å
ç
D ×
t
ç
è
=
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 704.
Operate
time
tMin
IEC05000133 V2 EN-US
Figure 704: Minimum time-lag operation for the IEC curves
In order to fully comply with IEC curves definition setting parameter tMin shall be set to the value
which is equal to the operating time of the selected IEC inverse time curve for measured current of
Technical manual
ö
( )
P
æ ö
i j
÷
- ³ ×
ç ÷ C A td
÷
è ø
Pickupn
ø
IMin
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
Current
IEC05000133-3-en.vsd
Section 26
Inverse time characteristics
(Equation 231)
1385