ABB Relion 611 Series, Technical Manual

Page: 480 / 536

The user can define the delayed inverse reset time characteristics with the following
formula using the set
Curve parameter D .
t s
D
I
I
k
[ ]
=
>





 −














⋅
2
1
A060817 V3 EN
(Equation 45)
t[s] Reset time (in seconds)
k
set
Time multiplier
D set
Curve parameter D
I Measured current
I> set Start value
9.2.3 Inverse-timer freezing
When the
BLOCK
input is active, the internal value of the time counter is frozen at the
value of the moment just before the freezing. Freezing of the counter value is chosen
when the user does not wish the counter value to count upwards or to be reset. This
may be the case, for example, when the inverse-time function of a protection relay
needs to be blocked to enable the definite-time operation of another protection relay
for selectivity reasons, especially if different relaying techniques (old and modern
relays) are applied.
The selected blocking mode is "Freeze timer".
The activation of the
BLOCK
input also lengthens the minimum delay
value of the timer.
Activating the
BLOCK
input alone does not affect the operation of the
START
output.
It still becomes active when the current exceeds the set Start value , and inactive when
the current falls below the set Start value and the set Reset delay time has expired.
Section 9
1MRS757454 D
General function block features
474 611 series
Technical Manual