ABB Relion 670 series, Руководство по применению, Страница: 230 / 760

R
X
RLdFw
RLdRv
ArgLd
ArgLd
ArgLd
ArgLd
IEC09000127-1-en.vsd
IEC09000127 V1 EN-US
Figure 140: Load encroachment of Faulty phase identification with load encroachment for
mho function FMPSPDIS characteristic
The use of the load encroachment feature is essential for long heavy loaded lines, where there
might be a conflict between the necessary emergency load transfer and necessary sensitivity
of the distance protection. The function can also preferably be used on heavy loaded medium
long lines. For short lines the major concern is to get sufficient fault resistance coverage and
load encroachment is not a major problem. So, for short lines, the load encroachment function
could preferably be switched off.
The main settings of the parameters for load encroachment are done in Faulty phase
identification with load encroachment for mho function FMPSPDIS. The operation of load
encroachment function is always activated. To deactivate the function, setting
LoadEnchMode
should be set off or the setting of
RLdFw and RLdRv must be set to a value much higher than
the maximal load impedance.
7.4.2.5 Short line application
SEMOD154453-105 v6
The definition of short, medium and long lines is found in IEEE Std C37.113-1999. The length
classification is defined by the ratio of the source impedance at the protected line’s terminal
to the protected line’s impedance (SIR). SIR’s of about 4 or greater generally define a short line.
Medium lines are those with SIR’s greater than 0.5 and less than 4.
In short line applications, the major concern is to get sufficient fault resistance coverage. Load
encroachment is not so common. The line length that can be recognized as a short line is not a
fixed length; it depends on system parameters such as voltage and source impedance, see
table 20 .
Section 7 1MRK 505 343-UEN B
Impedance protection
224
Application manual