ABB REL670 2.2 IEC - Load Impedance Limitation, Without Load Encroachment Function

2X1Zx X0Zx
arctan
2 R1Zx R0Zx
loop










EQUATION2304 V2 EN-US (Equation 259)
Setting of the resistive reach for the underreaching zone 1 should follow the
condition to minimize the risk for overreaching:
RFPEZx 4.5 X1Zx


IECEQUATION2305 V2 EN-US (Equation 260)
The fault resistance for phase-to-phase faults is normally quite low, compared to
the fault resistance for phase-to-earth faults. To minimize the risk for overreaching,
limit the setting of the zone1 reach in resistive direction for phase-to-phase loop
measurement in the phase domain to:
61
R
FPPZx X Zx


IECEQUATION2306 V3 EN-US (Equation 261)
8.9.3.7 Load impedance limitation, without load encroachment function
GUID-A7CDE76A-D5B5-4641-9324-2E9A99071DF5 v1
The following instructions are valid when Phase selection with load
enchroachment, quadrilateral characteristic function FRPSPDIS is not activated. To
deactivate the function, the setting of the load resistance RLdFw and RLdRv in
FRPSPDIS must be set to max value (3000). If FRPSPDIS is to be used for all or
some of the measuring zones, the load limitation for those zones according to this
chapter can be omitted. Check the maximum permissible resistive reach for any
zone to ensure that there is a sufficient setting margin between the boundary and
the minimum load impedance. The minimum load impedance (Ω/phase) is
calculated as:
Z
loadmin
U
2
S
-------=
EQUATION571 V1 EN-US (Equation 262)
Where:
U is the minimum phase-to-phase voltage in kV
S is the maximum apparent power in MVA.
The load impedance [Ω/phase] is a function of the minimum operation voltage and
the maximum load current:
Z
load
U
min
3 I
max
×
----------------------
=
EQUATION574 V1 EN-US
(Equation 263)
Section 8 1MRK 506 369-UEN B
Impedance protection
310 Line distance protection REL670 2.2 IEC
Application manual