Am I right in saying that fuses are not protecting the network, and that cables and transformers are burning out instead?

We are not getting to that stage here are we?

We have not had pavement link boxes exploding for a while.

I expect Con Ed is still profitable all the while.


Angram

Perhaps the USA should consider following the lead of Saudi Arabia, and start planning to join the 220V world, allowing thinner final circuit cables for a given power, or as they seem to desperately need, more power for a given installation. I think we could be in for a long wait.  Interestingly the Saudis are, at least on paper, moving to the UK fused plug model, not the round pin Europlug.

I can see the merits of a higher utilisation voltage such as that being adopted by Saudi Arabia, simplicity and smaller conductor sizes. In the particular instance of Saudi Arabia, this also means the end of 127 volts which is a rather odd voltage these days. Only a limited range of 127 volt lamps and appliances are available and the usual practice is to use equipment intended for 120 volts.

This tends to over stress such equipment especially if the nominal 127 volt supply is on the generous side. An actual 127 volts is probably OK for a 120 volt appliance. but 133 volts (127 plus 5%) is a bit high, and 140 volts (127 plus 10%) is almost certainly too much.

Also with a 127/220 volt system, there is little opportunity to increase the 220 volts to the new widely used standard of 230 volts. An existing 220 volt appliance should be fine at 230 volts, but a 120 volt appliance is unlikely to tolerate a nominal 133 volts that is likely to reach 140/145 volts actual.


Therefore Saudi Arabia have IMO made a very sensible decision.


As regards the USA, a higher utilisation voltage seems unlikely to help much with the recurring large blackouts. The main problem seems to be marginal high voltage transmission capacity and marginal medium voltage distribution capacity, neither of which will be relieved by increasing the utilisation voltage.

What America needs is either increased capacity, or reduced demand , or grid tied PV on a large scale. The increased air conditioning demand in hot weather  is a significant problem, which could be relieved by large scale adoption of grid tied PV. This could reduce transmission and distribution demand significantly and reduce thermal stress on cables and transformers at the hottest time of day.

I was being a bit tongue in cheek, I do not honestly expect the USA to up its voltages for final distribution or it's HV networks any time soon, but I do find the Saudi example fascinating, and I hope it goes well for them.

It cannot be worse than the situation in Brazil which seems to manage to have both 110V and 220V in adjacent towns, using the same plugs and sockets for both systems.

Regarding the grid tied PV suggested for USA, this gives rise to the problem we have in this country where it is possible to push the fault level over the capability of the transmission switchgear. This has led to projects such as the one with UK Power Networks : https://innovation.ukpowernetworks.co.uk/projects/powerful-cb/ which will allow more distributed generation to be connected.

As far as the 110/220V supplies of Brasil is concerned, I spent a number of years in South Korea which had a similar system, albeit with different sockets/plugs - American flat pin 110V and round pin 220V - and my flat had a mixture of both types (though I measured the voltages and they were actually 120V and 208V). The interesting aspect was that you could readily buy transformers to convert between the voltages, particularly 110-220 (some older flats only had one set of sockets) and new equipment could generally be switched between the voltages anyway. Adaptors to plug into either socket were also readily available. A stark warning was issued as a Norwegian visiting had brought his (230V) fax machine and to get it to work had bought a 110V/220V and plugged it in to (you guessed it) a 220V socket. It can be reported that the survival time of 230V equipment on 440V (or at least 416V) is not measurable on a stopwatch.......

Alasdair

Angram:

Am I right in saying that fuses are not protecting the network, and that cables and transformers are burning out instead?

We are not getting to that stage here are we?

We have not had pavement link boxes exploding for a while.

I expect Con Ed is still profitable all the while.


Angram

I suspect that a lot of the UK network is not protected against overload by fuses either. Many DNO substations have outgoing LV fuse ratings that total several times the transformer capacity. Reliance is placed on prudent design and hopefully cautious estimates of the maximum likely load, rather than on fuses.

The fuses generally only blow in case of a short circuit.

Small pole mounted transformers are often "protected" by HV fuses of several times the nominal input current, these are primarily to protect the rest of the network from a faulty transformer, not to protect the transformer.

The odd blow-up does occur, but not that many. The USA approach is perhaps similar but a bit less cautious ?


The blowing-up of pavement link boxes may not be load related, I would suspect water ingress and insulation breakdown.

At times like this you need An expert to find the overload.


I'm sure  #Lyle Dunn will like that.


Andy B.