ABB Relion 670 series, Technical Reference Manual

Page: 333 / 1232

The difference, compared to the distance zone measuring function, is in the
combination of the measuring quantities (currents and voltages) for different types of
faults.
The characteristic is basically non-directional, but FRPSPDIS (21) uses information
from the directional function ZDRDIR to discriminate whether the fault is in forward
or reverse direction.
The pickup condition PHSELZ is essentially based on the following criteria:
• Residual current criteria, that is, separation of faults with and without ground
connection
• Regular quadrilateral impedance characteristic
• Load encroachment characteristics is always active but can be switched off by
selecting a high setting.
The current pickup condition PHSELI is based on the following criteria:
• Residual current criteria
• 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.
• Load encroachment characteristic is always active, but can be switched off by
selecting a high setting.
The PHSELI output is non-directional. The directionality is determined by the distance
zones directional function ZDRDIR.
There are output from FRPSPDIS (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 FRPSPDIS (21) function. Their operating
characteristics are illustrated in figure
101 .
1MRK505222-UUS C
Section 6
Impedance protection
327
Technical reference manual