EV max demand vs. Normal high load reporting to DNO

gkenyon: 
 

vantech: 
 

Why notify one and not the other? 

 

The answer to this question is very simple.

Whilst you may have a service head with a 100 A fuse holder, the fuse inside may well be 60 A or 80 A.

There are a number of different reasons for this, but basically, for most properties, until an EV charger is required it's not really a problem.

So, you notify the DNO if your MD (including EV) will exceed 60 A.

The DNO will then be able to do whatever they need to do. In some cases, it's as simple as replace the fuse, in others it may involve upgrading the service cable, reinforcement of local network, etc.

Occasionally there's a minor problem that some of the not-so-smart meters have to be protected by an 80 A fuse, and there's nothing the DNO can do about that. In those cases, the largest service fuse you will be given is 80 A.

I have read here that the DNOs allocate 2-4Kw to each property when they design the network - this being the case, is the offer of an 80A or 100A fuse there “just because“ or are they actually accepting of the fact some properties could for long periods, draw 40-60A, with things like chargers and showers, cookers and hot tubs running? 

If you aren’t required to notify maximum demand changes, for instance when installing electric showers and hot tubs, how can they gauge the system maximum demand? This is what I don’t understand. They request this info for EV chargers, but don’t seem to take into account the maximum demand that could come from say, 5-6 properties on the same transformer splashing out on hot tubs that can all draw up to 28-32A in many cases. 

Thanks.

I most installations, unless 60 A load curtailment is used in the charger, the addition of a charger almost certainly will tip the MD above 60 A. 

I agree that other situations may cause an increase in MD, but if EV will then it's a no-brainer?

IF you walk around a typical housing estate and count the transformers and eyeball the ratings, you will find perhaps half megawatt units supplying 50-70 properties per phase. Perhaps in very densely built up areas you will see megawatt units,  (and in flats where really big blocks may have HV risers and transformers both at ground level and part way up ) and as things get more spread out smaller sizes are used as the voltage drop and copper costs conspire to mean that most houses are within a few hundred metres of the transformer secondary that supplies them. If you have a ttransformer that feeds very few properties the average load assumptions break down, so you do not find a 50kW unit supplying 29 houses, or an 2kw supplying