05/12/2021
Hakel SPD BD
In the most adverse of situations, SPD need to arrest as much as 100 kA. When distributed into individual strands, the current values amount to 25 kA per strand (using a TN-C) system. That is why we recommend that master distributors of LV unit substations (in buildings qualifying as LPL I protection level) be fitted with the HS 50-50 sealed spark gap with gas filling. Being SPD Type 1, the equipment guarantees the equalisation of potential and disposal of the lightning current as well as the switching surge that is generated in the power supply lines entering the building.
It is capable of arresting Iimp currents as large as 50 kA. Unit substations of individual buildings then should be fitted with the SPC25, a combination of SPD Type 1 and 2, that features dual varistors for higher safety and offers 25 kA of arrestable impulse current. Secondary substations and control cabinets should be equipped with SPD Type 2. An example of that class in our product range is the PIII-275, which is offered as a complete, sealed unit or with replaceable modules.
If the protected device is located within 5 m from the secondary substation or control cabinet, the system must be further equipped with a SPD Type 3 unit, for example the PI-3k. It is a high-frequency filter with attenuation min. 30 dB in the frequency band 0.15‐30 MHz that also features protective devices – varistors produced for rated currents from 16 to 400 A. In that case, an impulse separation suppressor PI-L needs to be inserted between SPD Type 2 and 3 to provide correct coordination of the arresters. Shielded cables need to be provided between the substation and the protected equipment for its proper operation.
Whenever controlling electronics is being protected, it is recommended that SPD Type 3 be fitted directly within the device. The category of auxiliary SPD, which are fitted as the end-line devices in the electrical system (sockets) includes ZS-1.1 with optical signalling of correct function of the surge protection and ZS-1.2 which has a miniature piezosiren. Other type modules are ZS-1L and ZS-1P which are fitted in wall boxes below the socket, in floor boxes or gutters.
