ABB RELION REX640 Technical Manual page 1029

Protection and control

Hide thumbs Also See for RELION REX640:

Table of Contents

1MRS759142 F

The current measurement of the function is based on two alternative measurement

modes, "DFT" and "Peak-To-Peak". The measurement mode is selected using the

Measurement mode setting.

If the current magnitude is below 0.02 · I

the impedance value is not evaluated and the maximum impedance value (99.999

pu) is shown in the Monitored data view.

The calculated phase-phase impedance amplitudes Z_AMPL_AB, Z_AMPL_BC and

Z_AMPL_CA are available as pu values in the Monitored data view.

Underimpedance detection

The operating characteristic is an origin-centric circle on the impedance plane. The

origin-centric circular characteristic is defined using the

calculated impedance value enters the circle in the impedance plane, the module

sends an enabling signal to start the Timer.

Figure 571: Origin-centric circular operating characteristics

Separate zones with an offset-mho characteristic can be designed using multiple

instances of the UZPDIS function with

the distance of the top of the circle from R-axis. If the sign of the

the top of the circle is above the R-axis and if it is negative, the top of the circle

will be below the R-axis.

circle is displaced from the X-axis. If the sign of the

Technical Manual

The calculated impedances are converted to a pu impedance as the

operating characteristics are defined using the

Offset and Displacement setting values as shown in Figure

Displacement is the distance by which the center of the

is the nominal phase current,

Polar reach setting in

Polar reach setting. If the

Offset enable setting and parameterized

Displacement setting is positive,

Protection functions

Offset is positive,