Diversity for a new install

Perhaps a ring main would work well.

Z.

Well you won't get much help on this from the diversity calculations in the OSG.  To a larger extent it will depend how well insulated these places are - things like caravan parks can be very variable, and if it is not warm then folk use the oven to warm  the place etc.. That said you can take comfort from the way the DNOs calculate loads for streets - a  500KVA substation may feed 50-70 houses per phase single phase and the odd parade of shops with 3 phase, and the fuses rarely fail unless there is a real fault.

To facilitate maintainence you probably want to lay it out as a few tree and branch radials with a box or pillar by each chalet that also means that if there is a problem, zones can be isolated and then power brought in for another zone if required,

How will site loads (street lighting etc) be handled?

This link is to a document by SP - pages 18-20 show how they estimate the demand for houses with substation load, but sadly not for chalets and caravans, other DNOS publish very similar information.

Mike.

I maintain an old established holiday chalet park with about 80 holiday chalets. The main intake room has 3 X 200 Amp main fuses. I suggested that the supply be upgraded as many chalet owners are installing new electric showers, cookers, ovens, grills, and heating etc. There have been no major fuse blowing issues reported due to overloading. I did once change  an old M.E.M. switch fuse due to old age, minor wear and rust.

Some of the sub mains are protected by old hot wire fuses.

I can only assume that luck plays a great part in having no regular fuse blowing. The fact that everybody does not have a morning shower at the same time. The fact that the park is never fully occupied. The fact that most people eat out whilst on holiday, and that the park is only open from April to October must contribute as well.

The park is fully electric with no gas or gas bottles at all.

I do feel that some remote chalets may suffer from high Voltage drop with heavy loads.

Z.

63 amps per unit sounds reasonable if they are to be all electric.

But that does not mean that the total demand will be 63 amps for each unit at the same time.

When calculating transformer size and the like, the DNOs allow about 10 amps per all electric dwelling for large numbers of homes. If calculated on that basis, then for 200 units you need about 2,000 amps, and 800 amps per phase would probably suffice.

To a large extent it depends on the pattern of use. If by "holiday home park" it is intended primarily for fine weather use, then about 10 amps per unit is reasonable.

If however these cabins are to become full time homes, all with electric heating, then on a cold winter day 800 amps per phase might prove insufficient. Especially if electric cars become popular.

Whilst the DNOs allow about 10 amps per home if mains gas is not available, this presumes that some houses will use bottled gas, oil, or solid fuel for heating.  If use of these fuels is not expected, then winter demand might reach 20 amps per unit. Say an average of a couple of 2 kw heaters and a few hundred watts for lighting and small appliances.

The other risk is that all the holiday cabins might be let not to random holiday makers, but to persons all attending some large political, religous, or cultural event. That can tend to increase maximum demand if large numbers all arrive at the same time and turn on heaters.

Ultimately it comes down to engineering judgement and some knowledge of expected use. Is the electricity to be metered, or included in the rent ? If included it will be used far more liberally.

A suburban housing estate of 200 homes might have two or three empty and for sale, and another half a dozen empty due to holidays. So about 5% consuming almost nothing. 200 holiday homes could well have every single unit used at the same time.

Cables will almost certainly be sized for voltage drop rather than for current carrying capacity.