Just to provide a statement on what's been said about supply availability (including broken neutrals).

Availability of supply for business-critical, mission-critical and life-safety supplies, is very complex.

You need to be very careful that the "supply security measures" you put in place, do not have a failure rate that makes them more of a risk to the final system availability, than the original supply.

AJJewsbury said:

Coping with persistent over voltages doesn't seem to be something we're particularly good at - even something as simple as a broken N (feeding 400V to 230V loads) tends t cause a lot of damage.

Yes, that's true ... we know that the BBC used the term "surge" which does have a defined meaning to us as electrical engineers, and of course that doesn't include persistent overvoltage ... but the actual event could have been something else.

There are also unusual conditions that can persist in certain HV faults, that are never normally seen (and you'd have to vastly over-design to address).

mapj1 said:

ilder parts of the world tend to have voltage monitoring relays

Agree ... also many of the over/under-voltage relays are not as reliable as the supply itself (although if you have the £££ you can buy what you like).

As a sidebar or for the curious

gridradar.net/.../wide-area-monitoring-system

As a sidebar or for the curious

gridradar.net/.../wide-area-monitoring-system