2. Cold standby operation: refers to the situation where there are no safety measures on each side of the connected equipment, and there are obvious or identifiable disconnection points on each side of the connected equipment. The equipment itself has no abnormalities, and all circuit breakers and isolation switches are in the open position waiting for the closing command. Once closed, the equipment can operate normally.

3. No load operation: refers to the working state in which the primary winding of a transformer is connected to the power supply and the secondary winding is open circuit. At this point, the current in the primary winding is called the no-load current of the transformer. The no-load current generates a no-load magnetic field. Under the action of the main magnetic field, electromotive force is induced in the primary and secondary windings.

In summary, there are currently three operating modes for transformers: parallel operation, cold standby operation, and no-load operation.

In addition, considering the cost of purchasing transformers, choosing transformers with excessive capacity is also a waste that outweighs the benefits. If the selected transformer capacity is too small, it is easy to cause serious consequences such as transformer burnout. Therefore, how to correctly select transformer capacity is an important link in energy conservation and loss reduction in the power grid.

So how should we choose the capacity of a transformer?

The selection of transformers should follow the principle of “small capacity, dense distribution points”. The transformer should be located at the center of the load, and the power supply radius should be around 0.5 kilometers. For power supply and lighting, the selection of transformers for the manufacturing industry should consider the simultaneous power of the electrical equipment. Transformers can be installed at around 1.5 times the load.

Transformers should be maintained once before operation, and transformers in operation or shutdown should be regularly maintained once a year.

Maintenance methods for transformers:

1. Connect the backup transformer, disconnect the high and low voltage circuit breakers of the transformer to be repaired, remove the operation fuse of the power supply, close the grounding switch, fully discharge the transformer, lock the high voltage cabinet, and place a “stop closing” sign at the switch.

2. Maintenance of dry-type transformers, cleaning of ceramic sleeves and casings to ensure cleanliness and tidiness, inspecting the casings, gaskets, and ceramic sleeves for cracks, discharge marks, or aging of rubber pads, and checking for deformation of cables and busbars. Any problems should be promptly resolved.

3. Check if the contact surface of the busbar is clean. If there is an oxide layer on the contact surface, it should be removed and coated with electric composite grease.

4. Check whether the transformer is well grounded, whether the ground wire is corroded, and solve any problems in a timely manner.

5. Check each lead terminal, pin, grounding screw, and connecting bus screw. If there is any looseness, tighten it in a timely manner.

6. Clean the dust around the transformer and accessories, and check if the fire protection facilities and ventilation system are in good condition.

The iron core materials used in transformers mainly include iron sheets, low silicon sheets, and high silicon sheets. Adding silicon to steel sheets can reduce their conductivity, increase their resistivity, reduce eddy currents, and reduce their losses. We usually refer to steel sheets with added silicon as silicon steel sheets. The quality of the silicon steel sheets used in transformers is closely related, and the quality of silicon steel sheets is usually represented by magnetic flux density B. Generally, the B value of black iron sheets is 6000-8000, low silicon sheets are 9000-11000, and high silicon sheets are 12000-16000.

2. The materials commonly used for winding transformers include

Enamel wire, sandbag wire, silk wire, the most commonly used enamel wire. The requirements for wires are good conductivity, sufficient heat resistance of the insulation paint layer, and certain corrosion resistance. In general, it is best to use high-strength polyester enameled wire of Q2 model.

3. Insulation materials

In winding transformers, insulation materials must be used for the isolation between the coil frame layers and the isolation between the winding resistances. Generally, the transformer frame material can be made of phenolic cardboard, the layers can be isolated with polyester film or telephone paper, and the winding resistances can be isolated with yellow wax cloth.

4. Impregnating material

After the transformer is wound, the final process is to impregnate the insulation paint, which can enhance the mechanical strength of the transformer, improve insulation performance, and extend its service life. Generally, cresol varnish can be used as the impregnating material.

One coil connected to an AC power source is called a primary coil (or primary coil), while the other coil connected to an electrical appliance is called a secondary coil (or secondary coil). The actual transformer is very complex, and inevitably there are copper losses (coil resistance heating), iron losses (iron core heating), and magnetic leakage (magnetic induction lines closed by air). The ideal conditions for a transformer to be established are: ignoring the leakage flux, ignoring the resistance of the primary and secondary coils, ignoring the loss of the iron core, and ignoring the no-load current (the current in the original coil when the secondary coil opens). For example, when a power transformer is operating at full load (with the rated output power of the secondary coil), it is close to the ideal transformer situation.

(1) Iron core. The iron core is the main magnetic circuit part in a transformer. Usually with a high silicon content and thicknesses of 0.35mm, 0.3mm, and 0.27mm respectively, it is made by stacking hot-rolled or cold-rolled silicon steel sheets coated with insulating paint on the surface. The iron core is divided into two parts: the iron core column and the horizontal plate, and the iron core column is covered with a winding; Horizontal plates are used for closed magnetic circuits.

(2) Winding. The winding is the circuit part of a transformer, which is wound with double wire insulated flat wire or enameled round wire. The basic principle of a transformer is the principle of electromagnetic induction. Taking a single-phase dual winding transformer as an example, its basic working principle is explained: when a voltage U1 is applied to the primary winding, the current I1 flows through it, generating alternating magnetic flux O1 in the iron core. These magnetic fluxes are called the main magnetic flux. Under its action, the two windings induce electromotive force, and finally drive the transformer control device.

2. Classified by structure: there are double winding transformers, three winding transformers, multi winding transformers, and autotransformers.

3. Classified by cooling method: there are oil immersed transformers and dry-type transformers.

4. Classified by cooling methods: there are natural cooling, air cooling, water cooling, forced oil circulation air (water) cooling, and water internal cooling.

5. Classified by iron core or coil structure: core type transformer (plug-in iron core, C-type iron core, ferrite iron core), shell type transformer (plug-in iron core, C-type iron core, ferrite iron core), ring type transformer, metal foil transformer, radiation type transformer, etc.

6. Classified by the number of power phases: single-phase transformer, three-phase transformer, multiphase transformer.

7. Classified by conductive materials: there are copper wire transformers, aluminum wire transformers, and semi copper and semi aluminum, superconducting transformers, etc.

8. Classified by voltage regulation method: it can be divided into non excitation voltage regulating transformers and on load voltage regulating transformers.

9. Classified by neutral insulation level: there are fully insulated transformers and semi insulated (graded insulation) transformers.

1. Intermediate frequency transformers have a large output and low price, and are mainly exported, which drives their rapid development. At present, the industry average price of intermediate frequency transformers for enterprises in China’s electronic system is 0.626 yuan/unit, but the average factory price for most enterprises is between 0.20 and 0.30 yuan/unit, with the highest being around 1 yuan/unit.

2. The market demand for power transformers is strong. Power transformers are labor-intensive products that are mainly customized by users. In recent years, there has been strong demand in domestic and international markets, making them a rapidly developing popular product. According to the “2013-2017 Market Demand Forecast and Investment Strategy Planning Analysis Report of China’s Power Transformer Industry” by Forward looking Network, India is expected to grow by 25%. Communication, computers, and consumer electronics products are its three main markets, with the growth of communication demand playing a significant driving role. Currently, the global annual demand for power transformers has exceeded 10 billion US dollars and is developing towards surface installation, high-power, and high-voltage.

If amorphous alloy transformers can completely replace the new S9 series distribution transformers, such as 10kV level distribution transformers with an annual demand of 50 million kVA, then they can save 10 billion kW of electricity in one year? Above h. At the same time, it can also bring good environmental benefits of building fewer power plants, reducing greenhouse gas emissions into the atmosphere, greatly reducing direct pollution to the environment, making it a new generation of truly green and environmentally friendly products. In summary, if the country can widely promote the use of three-phase amorphous iron core distribution transformers in the development and renovation of urban and rural power grid systems, it will ultimately achieve energy-saving and environmental benefits.

According to a research report released by MarketsandMarkets, the world’s second-largest market research institution, the global power transformer market is expected to generate revenue of $20.71 billion (approximately RMB 132.04 billion) in 2015. With the continuous growth of electricity demand and the continuous improvement of transmission and distribution infrastructure, this figure is expected to increase to $29.91 billion (approximately RMB 190.7 billion) by 2020, with a compound annual growth rate of 7.6% during this period.

The report points out that the continuous growth of global electricity demand will lead governments, both developed and developing countries, to increase investment in power generation facilities and transmission and distribution infrastructure to meet the needs of economic and social development. It is expected that global electricity demand will continue to grow at an annual growth rate of 2.4% from 2009 to 2035.

Power supply method of transformer

The 10KV high-voltage power grid adopts a three-phase three wire neutral ungrounded system operation mode.

The user transformer power supply mostly adopts the neutral point direct grounding system operation mode of Yyn0 connection, which can achieve three-phase four wire or five wire power supply, such as TN-S system.