The minimum clearance required between side wall and the Main Switchboard is Most low voltage switchboards in Singapore need to be by undergo a series of stringent tests performed by an independent third party laboratory. UESTION 2 distribution transformer for a building is specified as 6.6 kVI415 V, 2 MVA, ONAN, YN11. Explain the term ONAN.

ONAN stands for "Oil Natural Air Natural," which describes the cooling method used for transformers. In this system, the transformer is cooled by the natural circulation of oil, which absorbs heat generated during operation, and air is used to cool the oil. This means that for transformers like the one specified, the cooling relies on nature’s elements without the need for any additional cooling equipment, making it both cost-effective and reliable for enhancing operational efficiency. The YN11 designation refers to the transformer’s connection group, indicating that the transformer has a Y-connected (wye) primary winding and a delta-connected secondary winding. This configuration plays a crucial role in the voltage relationship and the phase shift between the primary and secondary sides, making it essential for determining how the transformer will perform in various load conditions and power distribution systems.