Zone Reach Setting Higher Than Minimum Load Impedance - ABB RELION 670 SERIES Applications Manual

Line distance protection

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1MRK 506 369-UUS -

Line distance protection REL670 2.2 ANSI

Application manual

GUID-11DD90FA-8FB5-425F-A46F-6553C00025BE V1 EN

is a maximum load-impedance angle, related to the maximum load power.

To avoid load encroachment for the phase-to-phase measuring elements, the set resistive

reach of any distance protection zone must be less than 160% of the minimum load

EQUATION579 V3 EN

is applicable only when the loop characteristic angle for the phase-to-phase

faults is more than three times as large as the maximum expected load-impedance angle.

More accurate calculations are necessary according to equation 148.

RFPPZx 1.6 Z

IECEQUATION2307 V2 EN

All this is applicable for all measuring zones when no Power swing detection function

ZMRPSB (78) is activated in the IED. Use an additional safety margin of approximately

20% in cases when a ZMRPSB (78) function is activated in the IED, refer to the

description of Power swing detection function ZMRPSB (78).

Zone reach setting higher than minimum load impedance

The impedance zones are enabled as soon as the (symmetrical) load impedance crosses the

vertical boundaries defined by RLdFwd and RldRev or the lines defined by ArgLd. So, it

is necessary to consider some margin. It is recommended to set RLdFwd and RldRev to

90% of the per-phase resistance that corresponds to maximum load.

The absolute value of the margin to the closest LdAngle line should be of the same order,

that is, at least 0.1 • Z

The load encroachment settings are related to a per-phase load impedance in a

symmetrical star-coupled representation. For symmetrical load or three-phase and phase-

to-phase faults, this corresponds to the per-phase, or positive-sequence, impedance. For a

Impedance protection

(Equation 397)

(Equation 398)

(Equation 399)