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BS7671 switched protective conductors

Former Community Member
Former Community Member
While referencing BS7671 relating to standby generator earthing I came across the clause below:

537.1.5 Where an installation is supplied from more than one source of energy, one of which requires a means of earthing independent of the means of earthing of other sources and it is necessary to ensure that not more than one means of earthing is applied at any time, a switch may be inserted in the connection between the neutral point and the means of earthing, provided that the switch is a linked switch arranged to disconnect and connect the earthing conductor for the appropriate source, at substantially the same time as the related live conductors.


The requirement for the Earth switch pole to close at substantially the same time, should this be early make - late break to ensure this system is earthed prior to live conductors being closed?


Bill
Parents
  • Former Community Member
    0 Former Community Member
    Bill,

    I think you really need to look at why this is required in the greater picture.

    With the DNO network being primarily TN-C, that is with CNE or PEN conductors, and being largely in a very poor state of repair, the requiement is there to limit the possibility of diverted and stray currents for one thing.

    Also with Neutral being a live current carrying conductor, one needs to be careful of the switching arrangements of that also.


    HTH
Reply
  • Former Community Member
    0 Former Community Member
    Bill,

    I think you really need to look at why this is required in the greater picture.

    With the DNO network being primarily TN-C, that is with CNE or PEN conductors, and being largely in a very poor state of repair, the requiement is there to limit the possibility of diverted and stray currents for one thing.

    Also with Neutral being a live current carrying conductor, one needs to be careful of the switching arrangements of that also.


    HTH
Children
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