1.Various Zs readings were taken throughtout the installation were taken a loop impedance tester and they were all high compared to the previous recorder results. 2. The vector group of the the transformer is Dyn 11 3. yes but maybe the earth passed through the transformer housing down the supplementary earth back to the 6.6kv switchgear and was strapped down to neutral at another transformer 4. So if that is the case then it is an oversight on the electrical contractor and because they had a reasonable earth loop reading they never thgought to strap it down to neutral 5. therefore we are correct to strap down on the LV side and not have the supplementary earth repaired