Yes, Mike, I mistakenly sent the information two times, as the transformer rating is 11kV/400V. This information I missed the first time. Apologies. 

thanks - I still can't see anything there to suggest it's TT though - are you sure it's not TN? (TN-S would be much simpler and more usual with private transformers).

   - Andy.

I appreciate your observation, Andy. I simply want to express my opinion regarding the earth leakage current. Since the project load distribution is unbalanced due to the majority of the connected load being idle and not in use, is this the source of the earth leakage current? As a result, three phase load balancing is impossible. There will be an unbalanced current in the transformer neutral due to the unbalanced load on the transformer. The N-PE connection in the Main LV Panel will be a path for circuiting the imbalanced current to earth even if it is connected to the ground earthing system since the transformer neutral is not directly earthed to the ground electrode and is instead connected to the distribution board neutral. The ground earthing system is connected to the N-PE link  of all distribution panels by a ring earthing system in the project.

Sounds to me like there's a number of different things potentially going on here.

Protective conductor currents - i.e. the "leakage" from filters and the like on electronic equipment) will occur just the same whatever the load or earthing arrangements (presuming things are earthed) - unbalanced 3 phase loads don't really make much difference to how protective conductor currents occur from single phase equipment, although where the protective conductor currents are in phase with the load currents, there will be a tendency for them to cancel out much more locally to the loads (e.g. at a local DB earth bar if several single phase loads are fed from difference phases). Typically we're talking milliamps per load.

Different arrangements of earthing the N don't make any difference protective-conductor-currents (i.e. leakage from individual loads) but  some arrangements - typically TN-C-S where a protective conductor also carries neutral currents (i.e a PEN conductor) can result in a portion of the neutral current flowing in what conventionally is considered to be the earthing system - usually referred to as diverted neutral currents. In a sound system that can only happen where the N is earthed at two or more points (creating a PEN conductor) - in conventional TN-S (and indeed TT) systems N is earthed a single point only, with N otherwise insulated throughout, so there's no route for neutral current to circulate via the earthing system. Where a PEN conductor is involved, the N current will divide between the conductor and parallel paths provided by the earthing system according to the relative impedances - if the parallel path is all metallic then a significant proportion of the N current is going to be diverted - so we're often talking a very significant number of amps.

  - Andy.

Thanks Andy. Well explained.