Distribution Transformer –
Transformers are among the most efficient machines ever designed by mankind, and are usually built of copper or aluminum. As copper has conductivity almost twice that of aluminum, it is often preferred in transformer construction. The largest power transformers have efficiencies at full load of 99.75%. Distribution copper-based transformers are smaller, less efficient and more lightly loaded. Transformers in urban distribution (typically 250-1,000kVa) may lose 1-2% of energy transformed as heat. For smaller transformers in rural areas (50-100kVa), efficiency in operation can be as low as 95%
Most of the distribution transformers installed by the State Electricity Boards use high levels of energy which results in huge losses. A large number of Distribution Transformers used in India, particularly in smaller ratings such as 25KVA, 63KVA, 100KVA (11KV/415V, 3 phase) use conventional materials and methods of manufacture, resulting in very high losses.
The failure rate of these transformers is very high, around 16% (in Govt. SEBs), which is not favorably comparable to international norms of 1 to 2%. Further the life of these conventional transformers is very low (6-8 years). The higher failure rate also adds to the already high Transmission & Distribution (T&D) losses in the power distribution network of SEBs.
Why Choose Copper
The advantages of using Copper in transformer windings:
Inherent low loss material
Special skills not needed during jointing and termination (significant percentage of transformer failure can be attributed to defective joints and termination)
Copper scores over Aluminium in several respects such as conductivity, resistance, thermal conductivity, better withstanding capability during short circuit, etc.
Easy availability and competitive pricing favors “Copper” usage.