The mitigation solution called "Zero buffer zone substation" has the objective of eliminating the buffer zone of a MV/LV energy distribution substation which is normally equal to approximately 2-2.5 metres from the perimeter of the substation itself.
Elimination of the buffer zone, as set forth in the regulation, is ascertained by using software that is experimentally validated and verified in compliance with standard IEC EN 62110:2012-11 at 20 cm from the substation walls.
Based on the configuration of the MV/LV transformer substation usually comprised of a MV panel, a MV/LV transformer generally in oil bath and a LV panel, the calculation model is created using MAGIC software, validated in accordance with M.D. of May 29 2008, which is used to take into consideration the major sources of magnetic emissions:
• MV panel;
• MV/LV transformer;
• connection wires between MV/LV transformer and LV switching panel;
• connection wires between MV panel and the MV transformer terminals
• LV switch panel.
The study is conducted by verifying the magnetic induction values generated by the substation in its surrounding area on different x-y planes parallel to the treadable surface of the substation and placed at various z distances from it.
A shield that guarantees observance of the quality limit (3 μT) at the nominal current is designed for each emission source.
The shielding elements that, as a whole, provide the magnetic induction mitigation action, are built by coupling highly conductive and high magnetic permeability materials, and refer to all aforementioned sources.
The substation is built by installing the equipment and shields in accordance with the project and the provided instructions.
The demonstration of the performance of this shielding solution was verified through a campaign of magnetic induction measurements along the outer perimeter of the substation every 0.50 m and at a distance of 0.20m from it. Measurements were taken at each point, at three different heights from the substation's treadable surface (0.5; 1; 1.5 m). Lastly, the average of the measurements taken at the three different heights was calculated for each measuring point.
This activity confirms the elimination of the buffer zone of the secondary substation and represents the final testing of the installed mitigation system.
Following the proposed mitigation activity, it is possible to affirm that the substation has a buffer zone, in compliance with M.D. of May 29 2008, of 0 (zero) metres from all of its walls.
There are two types of shielding that can be adopted for 400 and 630 kVA substations.