5.1.2. Transformer Reserve Index

The Transformer Reserve Index is an index of transformers that can increase safety and reliability. It is a very important index in identifying whether power equipment can respond to normal failure and random interruption. However, charging stations, specifically fast charging stations, where production increase appears to produce impulse signals in their connected transformers and responses from transformers must be received. An example of this condition from real data has been explained in a study from São Miguel Island. Figure 8 has illustrated this fact in a curve by time and daily load [19].

**Figure 8.** Transformer inputs in a fast and slow charge system by daily load versus time.

This problem can be partially solved by reserve index. To solve the mentioned issue, except transformer reserve, charging stations storage reserve is more sensible. Hence both of the reserves should increase logically.
