What is the difference between distribution transformers and power transformers?
◆ Distribution transformers are mainly used in power distribution networks to provide power to various users, generally high voltage to 66kV and low voltage 380/220V, 3kV, 6kV, 10kV. Power transformers are used to transfer electric energy between power grids of different voltage levels. For example, a regional substation has a transformer between 500kV and 220kV to exchange electric energy between the two power grids. The capacity of this transformer is It is very large and does not have the task of providing power to users.
◆ The mainstream energy-saving distribution transformers mainly include energy-saving oil-immersed transformers and amorphous alloy transformers. Oil-immersed distribution transformers are divided into S9, S11 and S13 series according to their loss performance. In comparison, the no-load loss of the S11 series transformers is 20% lower than that of the S9 series, and the no-load loss of the S13 series transformers is 25% lower than that of the S11 series.
◆ As China's "energy conservation and consumption reduction" policy continues to deepen, the state encourages the development of energy-saving, low-noise, and intelligent distribution transformer products. Some high-energy-consuming distribution transformers operating on the grid no longer conform to industry development trends and are facing the need for technological upgrading and replacement. In the future, they will gradually be replaced by energy-saving, material-saving, environmentally friendly, and low-noise transformers.
◆ The State Grid Corporation of China has widely used S11 series distribution transformers and is gradually promoting the S13 series in urban network transformation. In the future, S11 and S13 series oil-immersed distribution transformers will completely replace the existing S9 series operating on the network. The amorphous alloy transformer combines energy saving and economy. Its remarkable feature is that the no-load loss is very low, only about 20% of the S9 series oil-immersed transformer;
◆ It complies with the national industrial policy and the requirements of power grid energy conservation and consumption reduction. It is a distribution transformer with ideal energy saving effect. It is especially suitable for rural power grids and other places with low load rates. Although the National Development and Reform Commission began to encourage and promote amorphous alloy transformers as early as 2005, China's amorphous alloy transformers have not been mass-produced due to insufficient production capacity of raw material amorphous alloy strips.
◆ The proportion of amorphous alloy transformers used in network operation is only 7%-8% of distribution transformers. Only Shanghai, Jiangsu, Zhejiang and other regions nationwide use amorphous alloy transformers in large quantities. Competition for distribution transformers is fierce. Faced with the pressure of high raw material costs, as well as deficiencies in the construction of energy-saving evaluation systems and market supervision and management, the high initial investment in choosing energy-saving transformers makes the promotion of energy-saving transformers bring certain difficulties.
◆ The supply and distribution method of the 10kV high-voltage power grid adopts a three-phase three-wire neutral point ungrounded system operation mode. Most user transformers use the D/yn11 connection method to operate the neutral point directly grounded system, which can realize three-phase four-wire power supply. Folding capacity selection During the operation of distribution transformers, some may be underloaded due to excessive capacity, and some may be overheated or even burned due to overload or overcurrent operation. Improper selection of the capacity of this device affects the reliability and economy of the power supply of the power system.
