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


1
R 2 R1Zx R0Zx RFPEZx
3
  
IECEQUATION2303 V2 EN-US (Equation 136)
2X1Zx X0Zx
arctan
2 R1Zx R0Zx
loop










EQUATION2304 V2 EN-US (Equation 137)
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 138)
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 zone 1 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 139)
8.3.3.7 Load impedance limitation, without load encroachment function
SEMOD55087-97 v9
The following instructions are valid when Phase selection with load encroachment,
quadrilateral characteristic function FDPSPDIS is not used. The setting of the load
resistance RLdFw and RLdRv in FDPSPDIS must in this case be set to max value
(3000). If FDPSPDISis 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 140)
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:
Section 8 1MRK 506 369-UEN B
Impedance protection
230 Line distance protection REL670 2.2 IEC
Application manual