The NH system is classified as a plug-in fuse system and is made up of the following: fuse base (possibly with connection covers and phase cover), fuse inserts with contact blades, device for replacing the fuse inserts (low-voltage plug-in handle). Maintenance and servicing must be carried out by qualified personnel. NH fuse inserts of operating class gG are used to protect cables, devices and systems. They safely switch off impermissible overcurrents and short-circuit currents up to the rated breaking current. Fuse inserts gG also protect electrical devices and systems from the electrodynamic effects of high short-circuit currents. VDE 0636 Part 201, IEC 60269-1 and -2.