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

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."

 

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."