ABB Relion REC615, Техническое руководство

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t s
D
I
I
k
[ ]
=
>





 −












⋅
2
1
(Equation 83)
t[s] Reset time (in seconds)
k set
Time multiplier
D set
Curve parameter D
I Measured current
I> set
Start value
11.2.4 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.
11.3 Voltage based inverse definite minimum time
characteristics
11.3.1 IDMT curves for overvoltage protection
In inverse-time modes, the operate time depends on the momentary value of the
voltage, the higher the voltage, the faster the operate time. The operate time
calculation or integration starts immediately when the voltage exceeds the set value
of the Start value setting and the
START
output is activated.
1MRS758755 C General function block features
REC615 & RER615
Technical Manual
815