Fusing Cables

[Squizzy]

Working with alot of underground service cables at the moment ranging from 25mm to 240mm. Problem I have is that the local utility taps them straight onto the mains and then they go straight to the service pillar. Then the consumers mains are connected straight to them (some have fuses but not many)then it runs to the boundry fuses often through the consumers roof space etc. I have a real problem with this as the only protection on most of these cables between the consumers board fuses or boundry fuses is a HV drop out fuse. Our electrical Wiring Rules states that all cables must be protected by at least a fuse because if there is a fault in the roof space the only thing protcting it is a HV Drop Out Fuse which is any distance away through small mains often with splices increasing impedance and therefore would not guarentee the DOF going leaving a burning cable on the customers side and in their roof. What are the your Utility's guidelines for installing riser cables....

[BigClive]

Here in the UK the house feeds are tapped directly off a main underground secondary and the coaxial cable (phase surrounded by combined earth/neutral cores) enters the premises and goes straight into the fused cable head. I guess it's just a simpler way to do things with the fuse protected by being indoors. I'd guess that if the cable itself developed a fault then it's relatively large size would result in significant enough current flow to kill the streets supply. (Unless it's already been pushed beyond a sensible limit and had hyper-fuses fitted!)

If you used a fuse at the source of the houses supply it would need either individual fuse pillars for each house out in the street, or common fused pillars with a cable to each residence. Much more complicated.

[Squizzy]

Fusing it is simple we use Krone and Fistra fuse units on the poles for some cables and for bundled conductor, the units are bracket and a fuse tray with the 3 fuses in them. All you have to do is tap the overhead to the krone or Fistra and put the cable in the other side. Then its just a matter of using a switching stick to pull the unit and its isolated and that length of cable is directly fused. Why the Utility continues to design stuff like that its crazy having mains potential cables in domestic properties and against the Australian Standars AS3000 but the Utility can do what it wants to and does.

[CPOPE]

In general the customer in the US is required to fuse as close as is practiable to the service point. Service point is defined as the demarcation point where customer wiring connects to the Utility.

The Utility in general is required to follow the NESC.
http://standards.ieee.org/nesc/

The Utility sets minimum requirements for customer service connection requiremets.
http://www.nstar.com/business/service_requirements/docs/elecrequire.pdf?unique=20080412045334

THe customer must follow the NEC.
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70&cookie%5Ftest=1
THe requirement for the customer owned service disconect fuse/breaker is in Article 230:confused:

[BigClive]

Yeah, Squizzy, but that's up a pole. I thought you were talking underground where a whole street may be fed from one cable with connections spliced on at every home.

Things are different in America. As far as I can see it looks like most meters are external to the premises. In the UK and I guess Australia, they are predominantly Internal. Squizzy's original post seemed to be in regard to long runs of cable to indoor meters.