ABB RELION REX640 - Page 371

Voltage control mode
In the Voltage control mode, the Effective start value is calculated based on the
magnitude of input voltages U_AB, U_BC and U_CA. The voltage dependency is
phase sensitive, which means that the magnitude of one input voltage controls the
start value of only the corresponding phase, that is, the magnitude of voltage inputs
U_AB, U_BC and U_CA independently control the current start values of phases A, B
and C.
Two voltage control characteristics, voltage step and voltage slope, can be achieved
with the Voltage high limit and Voltage low limit settings.
The voltage step characteristic is achieved when the Voltage high limit setting is
equal to the Voltage low limit setting. The effective start value is calculated based
on the equations.
Voltage level Effective start value (I> effective)
U < Voltage high limit Start value low
U ≥ Voltage high limit Start value
In this example, U represents the measured input voltage. This voltage step
characteristic is graphically represented in Figure 222 .
Figure 222: Effective start value for voltage step characteristic
The voltage slope characteristic is achieved by assigning different values to Voltage
high limit and Voltage low limit . The effective start value calculation is based on the
equations.
Voltage level
Effective start value (I> effective)
U < Voltage low limit Start value low
U ≥ Voltage high limit Start value
1MRS759142 F Protection functions
REX640
Technical Manual
371