ABB Relion 670 Series Technical Reference Manual page 226

Section 6
Impedance protection
220
1. Residual current criteria, that is, separation of faults with and without ground
connection
2. Regular quadrilateral impedance characteristic
3. Load encroachment characteristics is always active but can be switched off by
selecting a high setting.
The current pickup condition DLECND is based on the following criteria:
1. Residual current criteria
2. No quadrilateral impedance characteristic. The impedance reach outside the load
area is theoretically infinite. The practical reach, however, will be determined by
the minimum operating current limits.
3. Load encroachment characteristic is always active, but can be switched off by
selecting a high setting.
The DLECND output is non-directional. The directionality is determined by the
distance zones directional function. There are outputs from FDPSPDIS (21) that
indicate whether a pickup is in forward or reverse direction or non-directional, for
example FWD_A, REV_A and NDIR_A.
These directional indications are based on the sector boundaries of the directional
function and the impedance setting of FDPSPDIS (21) function. Their operating
characteristics are illustrated in figure 101.
X
60°
Non-directional (ND)
ANSI05000668 V1 EN
Figure 101: Characteristics for non-directional, forward and reverse operation of
Phase selection with load encroachment, quadrilateral characteristic
FDPSPDIS (21)
X
60°
R
Forward (FWD)
1MRK505222-UUS C
X
60°
R
60°
Reverse (REV)
en05000668_ansi.vsd
Technical reference manual
R