ABB RELION REX640 - 3.15.4.2 Limit value supervision

Value unit
Value minimum
Value maximum
”Dimensionless”
100Ω
Input mode
”Resistance”
100
0
1600Ω
Input
AI_VAL
Input minimum Input maximum
Figure 71: Output as a ratio of the resistance range
The output scaling function:
k =
−
−
Input maximum Input minimum
Value maximum Value minimum
(Equation 4)
f k= − ⋅ +Value minimum Input minimum
(Equation 5)
AI VAL
f
k
_ =
−Input
(Equation 6)
3.15.4.2 Limit value supervision
All the measurement inputs have individual limit supervision modules that operate
similarly as in the measurement functions. The measured values are compared
against their set value limits. The limit supervision outputs are HIGH_ALARM,
HIGH_WARN, LOW_WARN and LOW_ALARM.
When an output is scaled, Value maximum and Value minimum are the range limits
to which the output value is limited or scaled. Hysteresis is added to the range limit
values so that the output value is allowed to slightly exceed or go below the limit
value before being treated as out of range.
The pre-defined hysteresis values are set based on the set Value unit .
Table 105: Pre-defined hysteresis values based on Value unit
Value unit Hysteresis
Dimensionless Based on the scaling function
1
Ampere 0.1 mA
Table continues on the next page
Basic functions 1MRS759142 F
176 REX640
Technical Manual