On 29/4/21 10:11 am, David Batho wrote:
> I wonder if the “boots” around the rails in new-build systems are any more effective than return current bonds. There was quite a fuss in the Sydney papers when a teenage (?) girl, walking barefoot down George Street during construction fo the SLR line, got a sock when she stepped in puddle. I seem to recall that the explanation was that they were trying out the electrical supply system.
That incident was not from the LR power supply. The only connection with the LR project was they were digging up the same street. The electrical pit ('domestic' 3 phase mains to the street, not LR power supplies) had been opened and when the lid was put back on, a cable was crimped between the lid and the frame. This eventually cut through the insulation.
Most contractors opening pits do not keep a record of pit openings, so it was impossible to determine who was actually responsible. The LR project copped it only because they had been doing major construction in the area. They were unable to prove that LR contractors who were the ones who opened the pit and disturbed the cable or any one else for that matter. But the media had already decided the light rail project was at fault so that was that.
Closer to my office a major brand new fibre optic cable failed installation testing due to the same thing, a loop in a pit along the way had come loose and got stuck between the lid and frame. Several thousand dollars of cable had to be re-run. The contractor took the hit.
>
> Does standing water, such as after rain, increase the electrolysis?
>
And dirt and grime etc.
Attempting to 100% insulate rails at ground level is a fools errand. The Melbourne approach of multiple bonds to earth return cables appears to be more robust and effective.
> David
>
>
>> On 28 Apr 2021, at 10:20 am, Mal Rowe mal.rowe@... mailto:mal.rowe@gmail.com> wrote:
>>
>> A couple of tramway projects are to happen over the next couple of weeks.
>>
>> *Firstly*, there is a program to install a substantial amount of kerbing in the CBD to enforce tram lane separation.
>>
>> Details are at: https://yarratrams.com.au/media/2176/cbd-kerbing-project-overview.pdf
>>
>> One of the most common accidents involving cars and trams in the city involves taxis doing an illegal U-turn in the rush to get a fare. This should reduce that - especially since the areas where this is most common are marked for kerbs.
>>
>> *Secondly*, route 57 trams will be diverted via Haymarket on Monday and Tuesday next for what Yarra call a "Power Supply Upgrade".
>>
>> Details at: https://yarratrams.com.au/media/2174/north-melbourne-tram-works-update-may-2021.pdf
>>
>> Looking at the work sites, my assumption is that the work involves renewal of return current bonds - to reduce electrolysis.
>>
>> While new builds of tramways usually try to insulate the rail return from ground to prevent electrolysis, established systems like Melbourne bury tons of copper in the ground to keep return currents away from buried infrastructure. (Pic attached).
>>
>> Mal Rowe - expecting cab drivers to be quite unhappy
>>
>>
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>> <Earth-bonds_SwanstonSt_22May2011.JPG>
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