Grounding Types and Distribution Networks

International regulations define low-voltage distribution networks in three ways. According to the TS 3994 standard, these distribution networks are named as follows. The application of grounding types varies depending on the facility type and its importance. While our traditional network structure is TT, using IT systems and isolated transformers in hospitals is extremely important. The LV Surge Arrester system selection also depends heavily on the grounding structure. Products should be selected and installed according to TT, TN, TNC, and TNS system characteristics. Choosing the wrong product for the wrong grounding type may cause protection issues. Therefore, site inspection is very important.

You can contact the Lightning Protection Center expert team for site inspection and LV surge arrester product selection.

1. TN System
2. TT System
3. IT System

In these systems, named according to connection types, the first letter indicates the transformer grounding status, and the second letter indicates the device grounding status. T stands for grounded, N for neutral, I for isolated.

You may be interested: Grounding Measurement

1-TT Networks

In TT networks, the star point of the network is grounded, providing operational grounding. The metal parts of the devices connected to the network are grounded separately from the operational grounding.

2-TN Networks

The TN network system is widely used. In TN networks, the neutral point is directly grounded, providing operational grounding.

TN-C system: The protective conductor (PE) and neutral (N) are combined into a PEN conductor, which runs throughout the network.

TN-S system: In TN-S systems, the protective conductor and neutral are separate throughout the network.

TN C-S System: In this system, PE and N conductors are separate in one part of the network and combined in another.

3-IT Networks

In IT networks, the star point of the transformer is completely isolated from the ground or grounded through a high-impedance element (coil, resistor). Devices connected to this network are also grounded.