Functionalityapplication - ABB REL650 Applications Manual

Section 6
Impedance protection
6.4.2
6.4.3
150

FunctionalityApplication

The evaluation of the direction to the fault is made in the directional element ZDNRDIR
(21D) for the quadrilateral and mho characteristic distance protections ZQMPDIS (21).
Setting guidelines
AngleRCA and AngleOp: these settings define the operation characteristic. Setting
AngleRCA is used to turn the directional characteristic, if the expected fault current angle
does not coincide with the polarizing quantity to produce the maximum torque. The angle
is positive, if operating quantity lags the polarizing quantity and negative if it leads the
polarizing quantity. The setting AngleOp (max. 180 degrees) defines the wideness of the
operating sector. The sector is mirror-symmetric along the MTA (Maximum Torque
Axis).
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
Directional elements for ground-faults must operate at fault current values below the
magnitude of load currents. As phase quantities are adversely affected by load, the use of
sequence quantities are preferred as polarizing quantities for ground directional elements.
Optionally six possibilities are available:
• Zero-sequence voltage polarized (-V
• Negative-sequence voltage polarized (-V2)
• Zero-sequence current (I
• Dual polarization (-V
• Zero-sequence voltage with zero-sequence current compensation (-V0Comp)
• Negative-sequence voltage with negative-sequence current compensation (-
V2Comp)
The zero-sequence voltage polarized ground directional unit compares the phase angles of
zero sequence current I
0
The negative-sequence voltage polarized ground directional unit compares
correspondingly I with -V2.
2
In general zero sequence voltage is higher than the negative sequence voltage at the fault,
but decreases more rapidly the further away from the fault it is measured. This makes the -
V polarization preferable in short line applications, where no mutual coupling problems
0
exist.
Negative sequence polarization has the following advantages compared to zero sequence
polarization:
)
0
)
0
/I )
0 0
with zero sequence voltage -V
1MRK 506 334-UUS A
at the location of the protection.
0
Application manual