Inverse-Timer Freezing - ABB RELION REX640 Technical Manual

Section 11
General function block features
11.2.3
1690
The user can define the delayed inverse reset time characteristics with the following
formula using the set Curve parameter D.
 
 
D
t s [ ] =   k
⋅
2
I
 
 
1
  − 

I
>
 
 
GUID-D324E98B-F672-4029-8322-054AE0E29CD3 V1 EN
t[s] Reset time (in seconds)
k Set Time multiplier
Curve parameter D
D Set
I Measured current
Start value
I> Set

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.
1MRS759142 C
(Equation 360)
REX640
Technical Manual