The Regional and/or Local Distribution transmission systems are classified by levels, based on the nominal voltage of Operation, according to the following definition:
Level 4: Systems with rated voltage greater than or equal to 57.5 kV and less than 220 kV.
Level 3: Systems with rated voltage greater than or equal to 30 kV and less than 57.5 kV.
Level 2: Systems with rated voltage greater than or equal to 1 kV and less than 30 kV.
Level 1: Systems with rated voltage less than 1 kV. ( Source: R.CREG – 097- 2008; Art 1)