Coordination of SPD, decouplers

The SPDs in the installation can only function properly if proper mutual coordination between them is provided - i.e. ensuring minimum required impedance between individual stages of SPD. This is achieved either by the minimum length of the cable (Fig. 1.), or by inserting an RTO decoupler (Fig. 2.). A correct selection of decouplers should be based on the documentation of the SPD manufacturer.

Fig. 1. Coordination provided by the length of the wire among individual stages of SPD

If the required coordination length of wires is not observed, the RTO decouplers must be inserted between individual stages:

Fig. 2. Coordination is provided by installing an RTO decoupler