Load Impedance Limitation, With Load Encroachment Function Activated - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
8.1.3.9
8.1.3.10
Transformer protection RET670 2.2 ANSI
Application manual
£ ×
RFPG 0.8 Z
load min
EQUATION1721 V2 EN-US
Where:
ϑ is a maximum load-impedance angle, related to the minimum load impedance conditions.
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.
RFPPZx  
1.6 Z
load
EQUATION579 V3 EN-US
Equation 99 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 100.
£ × ×
RFPP 1.6 Z cosJ
loadmin
EQUATION580 V1 EN-US
All this is applicable for all measuring zones when no power swing detection element
is in the protection scheme. 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 Power swing detection (ZMRPSB, 68) function.

Load impedance limitation, with load encroachment function activated

The parameters for load encroachment shaping of the characteristic are found in the
description of the phase selection with load encroachment function, section
guidelines". If the characteristic for the impedance measurement is shaped with the
load encroachment algorithm, the parameter RLdFw and the corresponding load angle
ArgLd must be set according to the minimum load impedance.
Setting of minimum operating currents
The operation of the distance function can be blocked if the magnitude of the currents
is below the set value of the parameter IMinPUPP and IMinPUPG.
é × +
2 R 1 R
× ¶ -
cos
ê
ë
× +
2 1
X X
R1PP
×
– -------------- - sinJ
X1PP
Section 8
Impedance protection
ù
0
× ¶
sin
ú
û
0
(Equation 98)
(Equation 99)
(Equation 100)
SEMOD168247-129 v2
"Setting
SEMOD168247-132 v2
247