ABB RELION REX640 Technical Manual page 1018

Protection and control

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Table of Contents

Protection functions

Measurement mode

3Phase-phase

If the polarity of the voltage signals is opposite to the normal polarity, the

correction can be done by setting

impedance vector by 180 degrees.

If the magnitude of the voltage is less than 0.05 · U

is not reliable and the impedance calculation is disabled. U

phase voltage.

The calculated impedance magnitudes and angles are available in the Monitored

data view. The impedance angles are provided between -180...180 degrees.

Impedance reach check

The operating characteristic is a circular offset mho on the impedance plane. The

operating characteristics are defined with the

settings. If the calculated impedance value enters the circle in the impedance plane,

the module sends an enabling signal to start the Timer.

Phase Sel for Z Clc

If all three phase voltages and phase currents are fed to the protection

relay, the positive-sequence alternative is recommended.

The calculated apparent impedance is converted to pu impedance as the

operating characteristics are defined with the pu settings.

Voltages and currents

U_AB, U_BC, U_CA, I_A, I_B, I_C

{ U_A,U_B,U_C } or { U_AB,U_BC,U_CA } and

I_A, I_B, I_C

Voltage reversal to "Yes", which rotates the

, the calculated impedance

Offset , Diameter and Displacement

1MRS759142 F

is the rated phase-to-

Technical Manual