SHIELDING FOR POWER DISTRIBUTION SUBSTATIONS WITH ZERO BUFFER ZONE: FRZERO SUBSTATION
The mitigation solution called the “Zero buffer zone substation” seeks to reduce the buffer zone for a MV/LV power distribution substation to zero; indeed, such buffer zones are normally at least 2-2.5 metres from the perimeter of the substation itself.
The buffer zone is reduced to zero, as required by the regulations, using a validated software that has been experimentally verified at 20 cm from the substation walls, in compliance with CEI EN 62110:2012-11.
Starting from the MV/LV transformer substation configuration — usually consisting of an MV switchgear, an MV/LV transformer, generally in oil, and a LV switchgear — the MAGIC software helps create a calculation model that takes into account the major sources of magnetic emissions and is validated in accordance with the Ministerial Decree of 29 May 2008.
- MV switchgear;
- MV/LV transformer;
- conductors connecting the MV/LV transformer to the LV switchgear;
- conductors connecting the MV switchgear to the transformer’s MV terminals;
- LV switchgear.
Fig. 16 – Secondary transformer substation
Fig. 17 – Shielding element design and simulation
Fig. 18 – Shielding element installation
The study is conducted by verifying the magnetic induction values generated by the substation in the area surrounding the substation itself; such values are measured on different x-y planes parallel to the substation floor and positioned at different z heights from the floor. For each of the emission sources, a shield is designed to ensure compliance with the quality limit (3 μT) at nominal current.
The shielding elements — that together constitute the magnetic induction mitigation intervention — are realised by coupling highly conductive materials with high magnetic permeability affecting all the above-mentioned sources.
The substation is realised by installing the equipment and shields in accordance with the design and indications provided.
Fig. 19 – Valori misurati durante il collaudo del sistema di schermatura
The performance of this shielding solution was demonstrated by a campaign of magnetic induction measurements taken along the external perimeter of the substation, every 0.50 m, and at a distance of 0.20 m from the substation itself. For each point, measurements were taken at three different heights above the substation floor (0.5; 1; 1.5 m).
Finally, at each measurement point, the measurements taken at the three different heights were then averaged.
This activity confirms reduction of the secondary substation buffer zone to zero and constitutes installed mitigation system testing.
Following the proposed mitigation work, it can be stated that the substation has a buffer zone of 0 (zero) metres from all its walls, in accordance with Italian Ministerial Decree of 29 May 2008.
There are two shielding variants that can be adopted for 400 and 630 kVA substations.