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jX
R
ZPE/2
ß
ArgLd
(Ref)
?
O
rc
F
φ
Load
|Zlo
ad|
|Zlo
ad|
/2
Ohm/phase
en06000406.vsd
IEC06000406 V1 EN-US
Figure 148: Definition of the setting condition to avoid load encroachment for earth-fault
loop
The maximum setting for phase-to-phase fault can be defined by trigonometric analyze of the
same figure
. The formula to avoid load encroachment for the phase-to-phase measuring
elements will thus be according to equation
Load
Z
ZPP 1.6
2 (1 cos( PP))
j
£
×
× -
EQUATION1605 V1 EN-US
(Equation 206)
where:
j
PP
= 180°–2·(ArgPP-
Q
Load)
All this is applicable for all measuring zones when no power swing detection element or blinder
is activated for the protection zones. Use an additional safety margin of approximately 20% in
cases when a power swing detection element is in the protection scheme, refer to the
description of the power swing detection function.
7.4.3.8
Load impedance limitation, with load encroachment function activated
SEMOD154469-129 v3
The parameters for load encroachment shaping of the characteristic are found in the
description of Faulty phase identification with load encroachment for mho (FMPSPDIS), refer
"Load encroachment characteristics"
7.4.3.9
Setting of minimum operate currents
SEMOD154469-132 v5
The operation of the distance function will be blocked if the magnitude of the currents is
below the set value of the parameter
IMinOpPP and IMinOpPE.
The default setting of
IMinOpPP and IMinOpPE is 20% of IBase where IBase is the chosen base
current for the analog input channels. The values have been proven in practice to be suitable in
most of the applications. However, there might be applications where it is necessary to
increase the sensitivity by reducing the minimum operate current down to 10% of
IBase.
Section 7
1MRK 505 343-UEN B
Impedance protection
240
Application manual
Summary of Contents for Relion 670 series
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