ABB RET650 Technical Manual page 635

1MRK 504 135-UEN A
Technical manual
æ
p
æ ö
i
- × × -
( t B k ) ç
ç ÷
op
è ø
>
in
è
EQUATION1190 V1 EN
where:
t is the operating time of the protection
op
The time elapsed to the moment of trip is reached when the integral fulfils according
to equation 110, in addition to the constant time delay:
æ ö
p
t
æ ö
i
ò
- × ³
ç C ÷ dt
ç ÷
è > ø
in
è ø
0
EQUATION1191 V1 EN
For the numerical protection the sum below must fulfil the equation for trip.
æ ö
p
æ ö
n i j ( )
å
D × -
t ç C ÷
ç ÷
è ø
>
in
è ø
=
j 1
EQUATION1192 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 271.
Time inverse characteristics
ö
= ×
C ÷ A k
ø
×
A k
³ ×
A k
is the first protection execution cycle when a fault has been
detected, that is, when
i
>
1
>
in
EQUATION1193 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
Section 21
(Equation 109)
(Equation 110)
(Equation 111)
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