ABB REL650 Applications Manual page 143

1MRK 506 334-UUS A
Application manual
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 54.
é
£ × ×
RFPG 0.8 Z
ê
ë
load min
GUID-11DD90FA-8FB5-425F-A46F-6553C00025BE V1 EN
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 Z
load
EQUATION579 V2 EN
RFP
Equation 55 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 56.
é
× ê
£ ×
RFPP 1.6 Z cos
load min
ë
IECEQUATION2307 V1 EN
All this is applicable for all measuring zones when no Power swing detection function
ZMRPSB (68) is activated in the IED. Use an additional safety margin of approximately
20% in cases when a ZMRPSB (68) function is activated in the IED, refer to the
description of Power swing detection function ZMRPSB (68).
Load impedance limitation, with Phase selection with load encroachment,
quadrilateral characteristic function activated
The parameters for shaping of the load encroachment characteristic are found in the
description of Phase selection with load encroachment, quadrilateral characteristic
function (FDPSPDIS, 21).
× +
2 R 1 R 0
¶ - ×
cos sin
× +
2 X 1 X 0
ù
R1
J J
- ×
sin
ú
û
X1
Impedance protection
ù
¶
ú
û
Section 6
(Equation 54)
(Equation 55)
(Equation 56)
137