An example of a three-level coordinated protection in power distribution systems

Using a three-stage protection suits virtually all types of applications.

Wiring the protection of Type 1 (lightning current suppressor) of the mains for objects with the main fuse up to 63 A connected by an earth cable, the TN-C network for LPL III (houses, small office buildings, agricultural buildings and residential buildings) and LPL IV (buildings and halls free of people and internal equipment).

Fig. 1. An example of wiring coordinated three-level protection of power distribution systems

Notes:

1. The example shows the placement of SPD in individual jednotlivých distributors.

2. Protecting the surge suppressor is only necessary if the main backup fuse is more than 160 A (in industrial applications it is recommended to use it every time, due to periodic inspections).

3. Proper coordination between the Type 1 and Type 2 of the SPD requires the cable length of at least 10 meters, or using a decoupler (for a correct solutions of the SPD coordination - see the example below).