ABB RELION REX640 Technical Manual page 1122

Protection and control

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Protection functions

to capacitor manufacturing tolerances. The natural unbalance current must be

compensated for before using the measured unbalance current for the function

operation. The natural unbalance current needs to be recorded when there is no

fault in the capacitor banks, and it is initiated through the command

unbalance , available under menu path Control > CUBPTOC. By selecting Record

unbalance with value "Record", the measured unbalance current

as the natural unbalance current

and angle of the recorded natural unbalance current I_AMPL_NAT and I_ANGL_NAT

are available in the monitored data view.

Once the natural unbalance current is recorded during further executions of the

function, the natural unbalance current is subtracted from the measured unbalance

Figure 630: Natural unbalance compensation. (a) Healthy condition when the natural

unbalance is recorded (b) Unbalance compensation during faulty conditions

The natural unbalance current compensation is enabled using the setting

Comp Enable . If Natural Comp Enable is set to "FALSE", the unbalance current is not

compensated. If

current is calculated based on the equation.

The amplitude I_AMPL_COMP and the angle I_ANGL_COMP of the compensated

unbalance current

to obtain the compensated unbalance current

Natural Comp Enable is set to "TRUE", the compensated unbalance

are available in the monitored data view.

and is stored as a reference. The amplitude

1MRS759142 F

is considered

(Equation 286)

Technical Manual