The NEC does not permit fuses in neutrals or in the grounding conductor. The fundamental principal is to keep the neutral(grounded conductor) and the grounding conductors at ground protential. If either of them is disconnected without simultaneously opening all phases, there will be a voltage between many parts of the system and the earth. In addition the neutral and grounding conductor(s) carry fault current during phase to ground faults. If is is diconnected there is no path and phase protection may not function. NEC 2005 and earlier "240.22 Grounded Conductor No overcurrent device shall be connected in series with any conductor that is intentionally grounded, unless one of the following two conditions is met: (1) The overcurrent device opens all conductors of the circuit, including the grounded conductor, and is designed so that no pole can operate independently." See also NEC Paragraph 240.4 General Requirements for grounding and bonding. Fusing a neutral is a big NO-NO.