General specifications Besides providing differential protection, in compliance with the current laws, the allpurpose relay CRD 23/DIN prevents the risk of permanently deactivating the systems if they trip in an unsuitable way (transient faults). These, which are caused by rapid overvoltages through lightning strikes, increase the normal dispersion in the installations. The relay provides: ■ Safety, by maintaining the lighting and/ or signalling systems in an active status, in the weather conditions in which they are essential. ■ Rationality, by doing away with unnecessary maintenance work for faults which, owing to their transitory nature, can no longer be identified. Operation If the dispersion exceeds the setting level, CRD 23/DIN acts on the line’s remote control switch (switch contact) and, after the selected resetting time (1 to 15 min.), conducts a test in order to re-activate the system. If there are permanent faults, the relay definitively cuts out the system after three attempts to reset it, by releasing the main circuit-breaker (switch contact). All these operations are commonly carried out within the times and according to the methods envisaged by the standards in force CEI 64-8 and CEI EN 61008-1. Owing to these special features the CRD 23/DIN relay is particularly suitable in unmanned plants where deactivation owing to transient faults can lead to hazard situations.