ABB RELION REX640 Technical Manual page 954

Protection and control

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Protection functions

The phase-to-phase measuring elements are based on the formula:

The faulted phase identification is done by comparing the measured impedance to

the operating characteristics in the impedance domain. If a measured fault loop

impedance is inside the characteristics, the corresponding phases are identified as

The shape of the characteristic is selected with the

Two shapes are available.

• "Mho (circular)", Non-directional mho

• "Quadrilateral", Non-directional quadrilateral

The two shapes can be flexibly configured. It is possible to set the reactive reaches

independently in forward and in reverse direction and for phase-to-earth (Gnd) and

phase-to-phase (PP) measurement elements, for example, the

X Gnd Rv reach GFC , X PP Fwd reach GFC and X PP Rv reach GFC settings. Also,

the resistive reach in case of quadrilateral characteristic can be set both forward

and reverse independently of reactive reaches, for example, the

GFC, Ris Gnd Rv Rch GFC, Ris PP Fwd Rch GFC and Ris PP Rv Rch GFC settings. The

characteristic is always mirror-symmetric around the reactance axis.

In case of heavy loaded feeders, the optional load encroachment logic can be

enabled with the

The impedance settings are in primary ohms.

Load Dsr mode GFC setting. The logic reserves an area for load

1MRS759142 F

(Equation 262)

(Equation 263)

(Equation 264)

(Equation 265)

(Equation 266)

Z Chr Mod Ph Sel GFC setting.

X Gnd Fwd reach GFC ,

Ris Gnd Fwd Rch

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