EQUATION1720 V1 EN (Equation 278)
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.
min
2 1 0
0.8 cos sin
2 1 0
load
R R
RFPG Z
X X
× +
£ × × ¶ - × ¶
× +
é ù
ê ú
ë û
EQUATION1721 V2 EN (Equation 279)
Where:
∂ 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.
RFPP 1.6 Zload£ ×
load
1.6 Z£ ×RFPP
EQUATION579 V2 EN (Equation 280)
Equation 94 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.
loadmin
R1
RFPP 1.6 Z cos sin
X1
J J
£ × - ×
é ù
×
ê ú
ë û
IECEQUATION2307 V1 EN (Equation 281)
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).
Section 3 1MRK504116-UUS C
IED application
338
Application manual
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