Hi

I am looking at a guideline that gives the expected useful lives municipal electrical reticulation as follows:

Lines
Underground 25 - 45yrs
Overhead 20 - 30 yrs
Cables 25 - 45 yrs


What I don't understand is the difference between overhead lines and cables - based on the EUL I would guess that cables are the same as underground lines but then why have two categories - or would it be equally correct to say that cable are the same as overhead lines?

There is no explanation of the differences in the guidelines.

I would read that as the life expectancy of the physical cable itself is 25-45 years.

When used in underground applications the life expectancy is unchanged.

When used in overhead applications (subject to weathering) the life expectancy is reduced to 20-30 years.

Either way 10 years seems a big margin!

Just my interpretation and I'm not qualified.

Not sure i understand your terminology so here goes generally.

underground cables are insulated and protected with a waterproof and armored sheath. Generally they have a 50 year lifespan and faults anr invariamly due to damage caused by excavations. Ulser cables had paper and oil insulation and were moisture sensitive so covered with a continuous lead sheath whilst modern cables are plastic and at 415v at least are capable of operating with water running out od the cores ( I have seen this!)

Overhead lines are uninsulated and rely on the insulating properties of air to prevent flashover. that is why they are high to prevent touching As they are exposed to the elements they deteriorate (oxidize) asnd are subject to weather damage. there are various standards with various lifetimes. as access is easier it is cost effective to design a shorter lifetime.

Overhead cables are insulated lines run overhead. they do not have to be separated to insulate them and are subject to the same weather conditions but are less liable to corrosion.

There is more - but do you rewally want to know!

What is the context of your question and I can be more specific - voltage, location, operating company all make a difference.

Cheers1

Its a bit out of context but I think when they say cables they are referring to the cables of the overhead lines as opposed to the wood poles and fittings.

Generally with overhead lines you refurbish them piecemeal so for example after maybe twenty years you would go through replacing fittings and some poles but leaving the cables and some poles in place. Then after 40 years you would go along and do a complete rebuild.

OK - thanks for the feedback guys - I spoke to one of my contacts in the electricity distribution industry and he informs me that cables are insulated overhead lines and lines are uninsulated. Hence the difference in EUL.

So V8kid wins first prize. You can move to the front of the class.