V.O.E.L.C.B.

Sparkingchip:

Perhaps we have gone full circle.


Back in the 1940’s the distribution network was considered unreliable due to war damage, then through the fifties and sixties everything got tidied up after the nationalisation of the individual electricity companies by the Government, but after seventy years and denationalisation we are back where we started due to a lack of maintenance and upgrades.

Yes, which actual skilled competent distributor or meter inspector comes to check the condition of the main head or metering equipment on a regular basis in our homes? Or is that job down to us, if and when an electrical inspection and test is carried out? And, is a ten year period too large a time between inspections?


Z.

Sparkingchip:

In that second document I linked to there is a good diagram comparing methods of earthing, the Australians used two earth rods with a VOELCB as in the diagram I posted earlier, being the Home Office recommended method.

Indeed the diagrams are very interesting. I will study them more thoroughly when I have had my afternoon nap and am fresher. Australian r'e on the right must have a bridge over the N conductor. I could not quite make it out, and initially thought that it must be a joint to N. Do you have a clearer image please? I think that re electrode on the left is the consumer's earthing electrode, and r'e is the V.O.E.L.C.B.s earth electrode that we called the "E" terminal of the device. Both electrodes must be isolated from the N terminal. The right hand r'e electrode must be positioned out of the resistance area of the left hand electrode.


When I was a child in the 50s, after I had had a bath I would sit on a towel placed on a hot tank in the bathroom. The prefab was very basic in design. The hot water tank was a cuboid shape and was galvanised steel. The tank contained an electric immersion heater. The electrical supply was via overheads to the bungalow. The earthing must have been via the underground metal water pipes. I do not ever remember inspecting the electrical fuse box. I was wondering just what would have occurred if the immersion heater had developed an earth fault due to a split element sheath. Presumably the loft header tank was metal, all pipes were metal, the bath was metal, the taps and internal pipes were metal, so effectively bonding was automatically present of all metal water pipes and connected stuff. So if the earthing was not 100 per cent perfect and the pipework rose in Voltage above true Earth, all metalwork would be at the same potential so no shock would occur to me in the bathroom.


Z.



 

 but because I am careful and take care of my property, and the installation was well made, no fault had ever developed. This is why the absence of RCD protection indoors does not frighten me. ?

I suppose that R.C.D.s are similar to car seat belts, air bags or any automatic fire extinguishing system. Rarely needed but when they are...................essential.


An R.C.D. saved me from a nasty shock/death once. All hail the R.C.D.


There have been cases where an indoor R.C.D. would have saved a life, as well as those protecting outdoor equipment.


The very sad case of Emma Shaw comes to mind.

Young mother electrocuted as she mopped up water from leaky boiler died after catalogue of workmen's errors | Daily Mail Online


IET discussion......

IET Forums - EMMA SHAW CASE (theiet.org)


Z.

Kelly Marie Angel:

I didn't realise PME  had been around that long I 5hought it was invented in the 1970s  

1930s was the earliest I've seen of this principle in the UK, but it was around elsewhere well before.  Of course, we could quibble about what exactly we mean by each of the many names that have been invented for much the same principle with mild variations, all within a general TN-C* concept.


It would be convenient to link to a comment I made in another thread (here, 11 days ago, 4th page), but these links seem always to go to the top of the thread, not the specific posting or even the right page: so I've copied the relevant part below. 


The most thorough reference I know of about the early days is "The use of protective multiple earthing and earth-leakage circuit-breakers in rural areas", H.G. Taylor 1937, from IET-digital-library here.  I'd be impressed if Sparkingchips's recent excellence at finding freely available versions of old papers succeeds here... (Note that Gilbert's work with comments is a lot more detailed than the abstract that was found in an earlier post here, although the abstract is very helpful about the flavour of the work.)  


There were many good technical works in those days: I'd hesitate to say they were long before their time, as they were very appropriate to what was happening then. But in modern times the basic principles and existing knowledge can easily get forgotten, and the same steps be repeated by each new generation, so we're often behind the knowledge that's out there somewhere.  I've many times been amazed when learning more of the work that went on then in the 1930s and 1940s with radio and radar, then computers, aircraft, etc.: in that context the electrical power feels like a conservative development, although plenty was going on there too.


The copied text as mentioned above:
"It [PME] was studied and trialled [in the UK] by ERA (electricity research association) in the late 1930s. Voltage-operated ELCBs with TT ('normal earthing') were also discussed. Both were seen as options for safety in rural supply, if one didn't want a further conductor.  Fact-finding missions (probably not by that name) were made to German utilities and factories. The German utilities had done some chopping and changing between systems. [...] Concerns with 'PME' in the UK were not just the needless-to-say ones, but also the expectation of some normal load currents straying through the ground ... concern for the sake of telephones and telegraphs. On the factory side, one of the 1930s works mentions a German case with one voltage-operated ELCB per machine-tool, where operators were seen rigidly following the instruction of pressing to test before starting their work."

 

Sparkingchip:

It seems that no one is going to pick up on a major cause of lost neutrals were bombs, balloons (which I presume were barrage balloons) and aircraft.

 

Sorry - I thought I knew the content of that paper, but I'd forgotten those references to the very different times.

A deliberate use of barrage-type balloons against power lines (higher voltage):  https://en.wikipedia.org/wiki/Operation_Outward