Hi all. I am trying to determine if this system is considered as a TT or TNS based on the image above.
From BS7671
TN System is
A system having one or more points of the source of energy directly earthed, the exposed conductive-parts of the installation being connected to that point by protective conductors.
TT System is
A system having one point of the source of energy directly earthed, the exposed-conductive-parts of the installation being connected to earth electrodes electrically independent of the earth electrodes of the source.
The design earth fault current return path is from the equipment earth bar to the equipment earth electrode to the buried bare copper ring back to the transformer earth electrode and back to the transformer earth bar then back to the transformer neutral.
I am trying to determine whether a fault current path that uses an earth electrode system can still be considered a protective conductor, and whether this arrangement would be classified as a TN-S system rather than a TT system, given that the installation earth electrodes are not electrically independent from the source earth electrodes.
