Transformer installations

Transformer installations may be classed under the following heads: (a) Choice of transformers with regard to size and construction; (b) Location of transformers with regard to accessibility and fire hazard; (c) Methods of Cooling; (d) Testing of oil and treating of deteriorated oil; (e) Choice of connections for high pressure windings, whether star or delta. In making a choice of transformers for plants up to 5,000 or 6,000 kw. capacity having only one transmission line, two banks of transformers connected in parallel, each bank comprising three single-phase units, and one extra single-phase unit for use in cases of emergency, are preferable. For larger stations, and especially those supplying several independent transmission lines, preference should be given to the three-phase type of transformer on account of its space economy.