Coordination of SPD with the control systems in the main switchboard or in close vicinity

The application with the control system uses the Type 3 of SPD with a high frequency filter, which protects the system both against overvoltage, and also against noises that occur in the low voltage networks. The SPD type 3 with a high frequency filter can be connected as follows:

Fig. 1. An example of connection of coordinated protection by SPD Type 1+2 and SPD Type 3 with HF filter

Notes:

1. The example illustrates the coordination (observing the correct cable lengths) between SPDs in individual control panels (distribution boards).

2. If the coordination distance between individual steps cannot be observed, an RTO decoupler must be used (see “Securing proper coordination of SPDs”).