ABB RELION REX640 Technical Manual page 942

Protection and control

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Protection functions

Imp zone shape

Quadrilateral

Mho (circular)

Mho Dir line

Offset Dir line

Bullet (combi)

Figure 523: Possible combinations of Directional mode Znx and Zone characteristics

settings. Pol. here means that the shape of the characteristic is affected by the

selected polarization method of mho circle (Pol quantity zone = "Cross pol", "Pos.

seq. volt.", "Self pol")

The directional lines are polarized with the set polarizing quantity of all impedance

measuring elements. In addition, the memory voltage that is based on positive-

sequence voltage substitute for the measured voltage with any impedance

measurement element polarization if the corresponding voltage drops too low.

DSTPDIS has separate and independent measurement elements for each fault

loop in the distance protection zone. In addition to the full scheme design, the

separate measuring elements are used for general fault detection and faulted phase

DSTPDIS supports both fault detection dependent control of zone timers and zone-

dedicated phasewise timer control for maximum application flexibility.

The impedance measurement is always done the same way regardless of the zone

shape. The operation is based on the impedance mapping approach where the

fault loop impedance is first calculated and then compared to the zone boundaries.

If impedance is recognized within the operation zone, the corresponding operate

output is activated after the operate time has elapsed.

The impedance measurement is based on full-cycle DFT filtered current and voltage

Directional mode Znx

Non-directional

Pol. = polarization method affects (mho)zone shape

1MRS759142 F

Technical Manual