An area is:
•a trace, starting from a source or
•a trace, starting from a transformer in the direction of high-voltage towards low-voltage.
The network below contains the following areas:
•source with 150kV network
•150/10kV transformer with 10kV network
•two 10/0.4kV transformers with their respective 0.4kV networks.
Example of a network with 4 areas