ABB RELION REX640 - Page 372

If Voltage low limit ≤ U < Voltage high limit ,
I>(effective) = I> - [ ((I> - A) / (C – D)) * (C – U) ]
(Equation 28)
A set Start value low
I> set Start value
C set Voltage high limit
D set Voltage low limit
Here U represents the measured input voltage. The voltage slope characteristic is
graphically represented.
Figure 223: Effective start value or voltage slope characteristic
To achieve the voltage slope characteristics,
Voltage high limit must
always be set to a value greater than Voltage low limit .
If Voltage high limit is lower than Voltage low limit , the voltage step
characteristic is active with Voltage low limit being the cutoff value.
The value of the setting Start value should always be greater than the
setting Start value low . Otherwise, Start value low is used as the effective
start value.
External input control mode
The External input control mode is used to enable voltage control from an external
application. If Control mode is set to the "Input Control" mode, the effective start
value for all phases is influenced by the status of the binary input ENA_U_MULT.
Protection functions
1MRS759142 F
372 REX640
Technical Manual