Page 60 - Practical Power System and Protective Relays Commissioning
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Power Transformers Theory Testing and Commissioning Chapter | 5 57
FIGURE 5.13 Vector groups of three-phase transformers with winding connections.
The main causes of overexcitation are:
1. System over-voltage.
2. System underfrequency.
3. Light loading of TL (Transmission Line).
