ABB RELION 670 Series Technical Manual page 421

1MRK 502 066-UUS B
7.14.8 Operation principle
The protection function is based on signal injection into a stator winding. These square wave
signals are generated in a separate injection unit REX060.
The injection signals are connected to the stator winding via:
• secondary winding of a voltage transformer (VT) located at the stator neutral point
• open delta winding of a three-phase VT set located at generator terminals
• secondary winding of a distribution transformer (DT) located at the stator neutral point; note
that REX062 is typically required for such arrangement
• open delta winding of a three-phase grounding transformer (GT) located at generator
terminals; note that REX062 is typically required for such arrangement
In the REX060 unit the injection voltage and current signals are amplified to a level adapted to the
analogue voltage inputs of IED. In IED the measured signals are processed and evaluation will give
detection of stator faults.
7.14.8.1 Configuration principle
Figure 222
Technical manual
shows a typical installation for stator injection.
Section 7
Impedance protection
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