ABB RED650 - Page 879

For inverse time characteristics a time will be initiated when the current reaches the
set start level. From the general expression of the characteristic the following can
be seen:
( )- × × - = ×
>
æ ö
æ ö
ç ÷
ç ÷
è ø
è ø
p
op
i
t B k C A k
in
EQUATION1190 V1 EN-US (Equation 94)
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 95, 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-US (Equation 95)
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-US (Equation 96)
where:
j = 1 is the first protection execution cycle when a fault has been
detected, that is, when
1
i
in
>
>
EQUATION1193 V1 EN-US
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 411.
1MRK 505 394-UEN A Section 25
Inverse time characteristics
Line differential protection RED650 2.2 IEC 873
Technical manual