ABB RET670 Applications Manual page 189

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1MRK504116-UUS C

Application manual

EQUATION792 V1 EN

This equation is applicable only when the loop characteristic angle for the single phase-

to-ground faults is more than three times as large as the maximum expected load-

impedance angle. For the case when the loop characteristic angle is less than three

times the load-impedance angle, more accurate calculations are necessary according to

equation 93.

EQUATION578 V3 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 impedance.

EQUATION579 V2 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 95.

IECEQUATION2307 V1 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).

IED application

(Equation 92)

(Equation 93)

(Equation 94)

(Equation 95)

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