Short Line Application - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
8.12.2.4
[1] RLdRv=RLdRvFactor*RLdFw
Transformer protection RET670 2.2 ANSI
Application manual
The IED has a built in feature which shapes the characteristic according to the
characteristic shown in figure 176. The load encroachment algorithm will increase the
possibility to detect high fault resistances, especially for phase-to-ground faults at
remote line end. For example, for a given setting of the load angle LdAngle, the
resistive blinder for the zone measurement can be set according to figure
higher fault resistance coverage without risk for unwanted operation due to load
encroachment. Separate resistive blinder settings are available in forward and reverse
direction.
The use of the load encroachment feature is essential for long heavily 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. Load encroachment is not a major problem. .
X
Zm
Load impedance area in
ANSI05000495 V2 EN-US
Figure 176: Load encroachment phenomena and shaped load encroachment
characteristic
[1]

Short line application

Transmission line lengths for protection application purposes are classified as short,
medium and long. 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
forward direction
LdAngle
R
LdAngle
Section 8
Impedance protection
176
Zm
ZL
LdAngle
LdAngle
RLdFwd
RldRev
ANSI05000495_2_en.vsd
GUID-331451C9-EA93-481A-BA2E-D729EDB98828 v4
affording
R
373