| Type of ground network | Description |
| TN | A system in which the supply equipment neutral is solidly grounded, electric installation cases are connected to the neutral wire. |
| ΠΆΠΆ | A system in which the neutral of supply equipment and electric installation case are solidly grounded, open conductive non-current-carrying parts of electrical installation are grounded with the help of grounding device, which is electrically independent from the supple neutral. |
| IT | A system in which the supply equipment neutral is insulated and grounded through apparatus and high-resistance equipment, electric installation cases are solidly grounded. |