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Powering the Shard

Former Community Member
Former Community Member
Afternoon one & all


I know we have single and three phase power, single mainly for domestic and three phase for commercial and small industrial.  But what sort of supply would The Shard have, does it have several 3 phase supplies or does it have an even higher supply that is then lowered via step down transformers to supply the various floors etc?
  • 0
    This link may be of interest.


    Many buildings in London (well almost anywhere with load of more than a megawatt actually, and also  buildings with a lot less load than that in more spread out areas) have a dedicated  HV supply  and  transformer, usually in the basement in a built up area, or on an H pole outside rurally..

    However when the building is tall enough that voltage drop on the way up is also a problem, (and lift motors are not a small load either) then as the link above suggests, it gets quite a lot more complex than just one transformer, and there is HV distribution in the building too.

    The onset of the economics forcing a  move the HV nearer are at about 1 volt per metre phase to phase - so any run of more than about 400m for LV 3 phase, 11km for 11kV and about half the length of the UK for the supergrid.

    It is possible to have oversized cables or systems that compensate for line droop, but as a rule of thumb it is a pretty good start.

  • 0
    11kV/20kV step up transformers

    That surprised me!


      - Andy.
  • 0
    An interesting question and one to which I had never turned my mind!


    Come to think of it, the fairy light on the top would be a 600 m circuit if the transformer were at ground level. So yes, substations on various floors.
  • 0
    A building of this size is not going to tap into the 415 V 3-phase local supply. It is going to have is own substation. And that substation will not be the source of the 415 V supply for the building. More likely the substation secondary will be something like 3·3 kV. This will supply 3·3 kV / 415 V transformers dotted around on various floors. If there is large machinery, this may be fed from the 3·3 kV.


    That's my guess anyway; there are various possibilities.


    I now await some bright spark with intimate knowledge of the Shard to tell us how it really is set up.
  • 0
    well the link I posted below suggested they had about 6 megawatts of load in total and implied they intended to stepped up from the incoming 11kV to 20kV for the internal distribution, which surprised me, I'd have expected an 11kV loop to be easier, but may be about keeping the cable ducts to a manageable diameter for other reasons (even at 20kV phase to phase ~ 15kV phase to ground 6MVA is around 150 amps per phase)

    Mind you 20kV phase to phase is one of the French and Italian HV distribution standards, where we might normally use 11kV or 33kV (or occasionally 6,6 in the UK) so perhaps the choice of primary voltage for the upstairs HV to LV transformers may have been as simple as a cut and paste from the last job by the Italian architects.
    a note from the cahier techniques about HV in varying countries.
  • Former Community Member
    0 Former Community Member
    AJJewsbury:
    11kV/20kV step up transformers

    That surprised me!


      - Andy.


    Not that uncommon in that part of town - it's the only practical way to wring more out of existing infrastructure. 20kV is becoming an increasingly normal supply intake voltage in some UK cities.


    The choice of internal HV distribution voltage is principally driven by size constraints (every m2 of riser is space on each floor that can't be let) - 20kV again is becoming increasingly common on taller buildings (which follows a similar philosophy on tall buildings across the globe)


    It does raise an eyebrow for UK centric engineers.


    Regards


    OMS


  • 0
    Very close to the Shard is a DNO 22kV sub station. 


    A coupe of years ago my company inspected a very large building near by. In that area there is a 22kV ring supplying the larger buildings. In the building we inspected there were 2 very large panel with a 11kV private transformer on the ends of the panel in the basement. These transformers were supplied from 2No.  22kV to 11kV DNO transformers.There was further transformer on the end of a panel in a roof plant room along with 4 No. 1MVA standby generators.


    I worked with an engineer who worked on the Shard electrical installation project. I cannot remember the exact details but he did tell me that there were a number, he did tell me but I have forgotten, up on floors in the building. I assume there was a 22kV/11kV DNO transformer in the basement supplying an 11kV private ring of transformers up the building.


    Another  building I visit from time to time has 11 No. 11kV private transformers in a ring supplied from 2 No. DNO 11kV feeders.
  • 0
    Interesting, clearly London is becoming more "continental" . Joking aside it seems quite wasteful to have extra transformers for 11 to 22 rather than just run round in the incoming voltage, or alternatively to raise the HV loop to 33kV and get the currents down.

    I presume that the problem is one of legacy equipment and use of existing cable ratings, as there are plenty of 33kV to 400V transformers on the ends of long lines in very rural places, so it can be done, just maybe not in the middle of existing system.

    Similar problems are slowing down the voltage increase on the London underground, which is/ has been trying to move from 630-ish DC to more like 750 to align with the 3rd rail railways (and at the current rate of progress will be just about done in time for all  the 3rd rail railway to start planning change to 25kV overhead lines.)
  • Former Community Member
    0 Former Community Member
    mapj1:

    I presume that the problem is one of legacy equipment and use of existing cable ratings, as there are plenty of 33kV to 400V transformers on the ends of long lines in very rural places, so it can be done, just maybe not in the middle of existing system.

     


    Sure it "can be done" - but no single developer wants to pay the burden of sorting out infrastructure - they only want to pay the minimum for their little bit - hence the UKPN approach of pushing up the voltage to wring what they can out of the infrastructure locally.


    Curiously, we also see a lot of infrastructure going the "other way" - two recent projects have both had 10kV infrastructure used rather than the more traditional 11kV


    Regards


    OMS


  • 0
    Just as a matter of interest OMS, what type of tx do you specify? I am sure fire safety is a crucial aspect.

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