What are the main differences between Power transformer and distribution transformer?
Power transformers For transmitting networks of higher voltages for step-up and step-down application (400 kV, 200kV, 110kV, 33kV) and are generally rated above 200MVA in power transformers. For lower voltage distribution networks as a means for connecting end users among 11 kV, 3.3kV, 440V, 230V is basically rated less than 200MVA in distribution transformers.
Transformer Size/ Insulation Level: Power transformer is for heavy load transformation load, it has 100% efficiency and high voltage greater than 33 kV. Distribution transformer is lesser in size when compared to this transformer and the main uses of this device can be found in generating station and Transmission sub station and higher level insulation. The distribution transformer is used for the electrical energy distribution at low voltage less than 33kV for works related to industry and 440V-220V for household purposes. A lower efficiency of 50-70% size is enough , lower magnetic losses, easier installation, without full load.
Iron Losses and Copper Losses Transmission network uses Power transformer as they do not directly connect with the users, there is very less load fluctuation. Throughout the day for 24 hrs they are loaded and the specific weight that is the division of iron weight by copper weight is very less. In distribution network a power transformer is used and so they are connected to the consumer which leads to higher load fluctuations. The iron losses takes place 24 hrs a day and copper losses depends on the load cycle as it is not loaded fully and the specific weight is more as average loads are about 75% of full load and these are made in such a way that efficiency occurs at its maximum of 75% of full load. All day efficiency is defined in order to calculate the efficiency with power basis. The main use of power transformers are in step up devices for I2r loss minimizing a given power flow. For utilizing the core to maximum these transformers are designed and it will operate with more clarity near the B-H curve. The above kind of design cannot be applied for distribution transformers. While designing it the efficiency throughout the day comes into the picture. Typical load cycle for supply depends on its supply. For taking care of the peak load the core design will be done along with all-day-efficiency.
Power transformer commonly works on full load. Hence, its design has a motto to reduce the copper loss. The core losses are less because the distribution transformer is working on loads less than full load most of the time. The flux density is higher in Power transformer when compared to distribution transformer.
Maximum efficiency The major distinction between distribution transformer and power transformer is its design for maximum efficiency at 60 to 70 % load but power transformer has 100 % load with maximum efficiency because it works at 100% load near the generating station. Join the electrical training course to make your career in this field as an electrical designer. Stay connected to CRB Tech for more technical optimization and other updates and information.