jX
R
ZPG/2
β
LdAngle
(Ref)
γ
O
rc
F
φ
Load
|
Z
l
o
a
d|
|Z
l
o
a
d
|/
2
Ohm/phase
ANSI06000406-1-en.vsd
ANSI06000406 V1 EN
Figure 134: Definition of the setting condition to avoid load encroachment for ground-
fault loop
The maximum setting for phase-to-phase fault can be defined by trigonometric analyze of
the same figure
134. The formula to avoid load encroachment for the phase-to-phase
measuring elements will thus be according to equation 186.
Load
Z
ZPP 1.6
2 (1 cos( PP))
j
£ ×
× -
EQUATION1605 V1 EN (Equation 186)
where:
jPP
=
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.
Section 8 1MRK 506 369-UUS -
Impedance protection
276 Line distance protection REL670 2.2 ANSI
Application manual
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