ABB RELION 620 Series Technical Manual page 511

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1MAC504801-IB E

620 series ANSI

Technical Manual

blinder R and Outer blinder R intercepting at R-axis. The blinders are at the same angle as

the Impedance angle. The second blinder of each outer and inner pair is automatically

made symmetrical with the origin of the R-X plane.

For a correct operation, it is required that the setting for Inner blinder R is

less than the setting for Outer blinder R.

The circular mho characteristic can be further divided into two zones by setting Zone 2

enable to "Yes". The boundary between zones is set using the setting Zone 1 reach. The

lower portion of the circle, Zone 1, is separated from the upper portion, Zone 2, by a line,

perpendicular to the blinders, located at a set percentage of the Forward reach setting

from the origin.

GUID-96D30A49-89E3-46B5-863E-69C483838C54 V1 EN

Operating region for out of step with double blinder

A third zone, Zone 3, can be enabled by setting Zone 3 enable to "Yes". Zone 3 is defined

to include the area outside of the circular mho characteristic but inside a larger circle

centered on the origin that represents impedance with the magnitude of the minimum

positive-sequence current defined by setting Min Ps Seq current and the rated positive-

sequence voltage.

the zones should be coordinated with the settings for any distance protection functions.

shows the three zones. Settings that determine the shape of

Protection functions

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