ABB REC650 - Page 621

( )- × × - = ×
>
æ ö
æ ö
ç ÷
ç ÷
è ø
è ø
p
op
i
t B k C A k
in
EQUATION1190 V1 EN (Equation 76)
where:
t
op
is the operating time of the protection
The time elapsed to the moment of trip is reached when the integral fulfils according
to equation 77, in addition to the constant time delay:
0
- × ³ ×
>
æ ö
æ ö
ç ÷
ç ÷
è ø
è ø
ò
p
t
i
C dt A k
in
EQUATION1191 V1 EN (Equation 77)
For the numerical protection the sum below must fulfil the equation for trip.
1
( )
=
D × - ³ ×
>
æ ö
æ ö
ç ÷
ç ÷
è ø
è ø
å
p
n
j
i j
t C A k
in
EQUATION1192 V1 EN (Equation 78)
where:
j = 1 is the first protection execution cycle when a fault has been
detected, that is, when
1
i
in
>
>
EQUATION1193 V1 EN
Dt
is the time interval between two consecutive executions of the
protection algorithm,
n is the number of the execution of the algorithm when the trip time
equation is fulfilled, that is, when a trip is given and
i (j) is the fault current at time 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 285.
1MRK 511 287-UEN A Section 19
Time inverse characteristics
615
Technical manual