Basic Characteristics - ABB REL650 Applications Manual

Section 6
Impedance protection
6.6.2.2
6.6.3
158
Distance IEDs located in interconnected networks see these power swings as the swinging
of the measured impedance in relay points. The measured impedance varies with time
along a locus in an impedance plane, see figure 75. This locus can enter the operating
characteristic of a distance protection and cause, if no preventive measures have been
considered, its unwanted operation.
jX
Operating characteristic
IEC09000224 V1 EN
Figure 75: Impedance plane with Power swing detection operating characteristic
and impedance locus at power swing

Basic characteristics

Power swing detection function (ZMRPSB) (68) reliably detects power swings with
periodic time of swinging as low as 200 ms (which means slip frequency as high as 10%
of the rated frequency on the 50 Hz basis). It detects the swings under normal system
operating conditions.
ZMRPSB (68) function is able to secure selective operation for internal faults during
power. The operation of the distance protection function remains stable for external faults
during the power swing condition, even with the swing (electrical) centre located on the
protected power line.
The operate characteristic of the ZMRPSB (68) function is easily adjustable to the
selected impedance operate characteristics of the corresponding controlled distance
protection zones as well as to the maximum possible load conditions of the protected
power lines.
Setting guidelines
Setting guidelines are prepared in the form of a setting example for the protected power
line as part of a two-machine system presented in figure 76.
Impedance locus at
power swing
R
IEC09000224_1_en.vsd
1MRK 506 334-UUS A
Application manual