SPD for direct current DC applications and for photovoltaic applications. They are generally installed as close as possible to the origin of the installation, e.g. in Main Distribution Boards (MDBs), as well as in Sub Distribution Boards (SDBs).
SPDs for telecommunication and signalling applications. Typical installation: in series with the signal/telecommunication circuit for the equipment with "low resistability" according Recommendation ITU-T K.45 / "low surge immunity" according IEC/EN 61000-4-5.
High Voltage Surge Arresters. Typical use: high voltage surge arresters for the protection of HV/MV transformers, switches and power transmission lines. Designed, produced and tested in accordance with the IEC standards.