Operation Principle - ABB REL650 series Technical Manual

Section 6
Impedance protection
Table 35: FDPSPDIS Non group settings (basic)
Name Values (Range)
GlobalBaseSel 1 - 6
6.2.6
130
Unit Step
- 1

Operation principle

The basic impedance algorithm for the operation of the phase selection measuring
elements is the same as for the distance zone measuring function. Phase selection with
load encroachment, quadrilateral characteristic FDPSPDIS (21) includes six impedance
measuring loops; three intended for phase-to-ground faults, and three intended for phase-
to-phase faults as well as for three-phase faults.
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.
A current-based phase selection is also included. The measuring elements continuously
measure three phase currents and the residual current, and compare them with the set
values. The current signals are filtered by Fourier's recursive filter, and separate trip
counter prevents too high overreaching of the measuring elements.
The characteristic is basically non-directional, but FDPSPDIS (21) uses information from
the directional function (ZDNRDIR) to discriminate whether the fault is in forward or
reverse direction.
The pickup condition STCNDZI is essentially based on the following criteria:
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.
Default Description
1 Selection of one of the Global Base Value
groups
1MRK 506 335-UUS A
Technical manual