Most of the electricity needed by humans in all countries of the world is generated by production centers such as heating, hydropower and nuclear power plants. These centers have turbines and three-phase alternatives, and the voltage generated by the generators must be increased to a level that is cost-effective for transmission. Sometimes several generating centers are connected by grids to distribute the required electrical energy continuously and in sufficient quantities in different cities and regions.
In distribution areas, in order for the voltage to be usable for general use and factories, the voltage must be lowered. It increases and decreases the voltage by Transformers Done. Obviously, energy distribution among all consumers in a city from the main distribution center is not possible and will require a large cost and voltage drop. Therefore, each main center is divided into several centers or smaller posts (city posts) and each post is divided into several smaller distribution points (regional posts). Each of these centers, in turn, uses voltage distribution and conversion transformers.
In general, in the family and distribution of electrical energy, transformers are the main pillars and members and their importance is not less than transmission lines or power generators. Fortunately, due to the presence of minimal dynamic devices in them, they face less problems and vulnerabilities. Of course, this does not mean that protection and service can be neglected. In this article, first a brief theory and definitions of the types of transformers are given, then the role of transformers in the power generation and distribution network, and finally a description of the service and repair of transformers is provided.
Theory and definitions of transformers
Transformers, in simple terms, are a device consisting of two sets of primary and secondary windings that are placed in a magnetic field and around sheets of special iron called the transformer core. Insulators or bushings or insulators and finally the transformer container or chamber.
The operation of transformers is based on the transfer of electrical energy from a system with a certain voltage and current to another system with a different voltage and current. In other words, a transformer is a static device that in aMagnetic field Transmits electric current and pressure between two or more windings of the same frequency and size.
Types of Transformers
Manufacturers and standards in different countries have each categorized transformers and provided definitions for their rating. Some transformers are known according to their cases and order of operation, such as power transformers, autotransformers or amplifier transformers and a group of transformers other than instrument transformers (current and voltage transformers) are called power transformers and so-called power transformers. They know that electric pressure is generated on their secondary side.
This type of segmentation in practice covers a wide range, on one side of which are small and portable low-voltage transformers for hand-held lamps and the like, and on the other side are very large transformers to convert the generator output voltage to mains voltage and lines. Power transmission. Between these two sizes (average) are distribution or transmission transformers in electrical installations and transformers converted to standard voltages.
Transformers are often designed as core or wall. In the core type, each of the coils consists of half a low pressure coil and half a high pressure coil, and each is located on one core arm. In the wall type, the coils are wound on a core and half of the magnetic metal circuit is closed on one side and the other half on the other side of the core.
Most often, the wall type is used for low voltage and large output and the core type is used for high voltage and small output (three-phase or single-phase).
Power and Power Transformers Like the main power plant transformer and autotransformer power transformers, power transformers are usually three-phase, but sometimes they may use three single-phase transformers at high powers due to their large volume and weight and transportation problems. Industrial transformers such as welding transformers, starting transformers and transformer transformer transformers for traction and absorption systems used in railways and electric trains. Special transformers for testing, measuring, protection of electrical consumption, etc.
Distribution transformers and its types
Distribution transformers are one of the important equipments of power distribution networks that are used in 33, 20, 11KV distribution substations in order to reduce the voltage level and bring it to the level that can be used by consumers.
Types of Distribution
Transformers Distribution transformers are divided into several types according to their operating mechanism, structure and components:
a) Classification of transformers in terms of type of insulation and cooling material
1. Oil transformers
These types of transformers are divided into two categories in terms of tank design and how they communicate with the surrounding air:
1.1. Expansion source oil transformers (conservatory)
The design of this type of distribution transformers is such that the oil system with outside air, through the chamber Dehumidifiers The expansion and contraction of the reservoir oil is compensated for in the expansion source or conservator.
1.2. Hermetic transformers of
the building This type of transformers is such that the oil has no contact with the outside air and the change in oil volume due to temperature changes is compensated in two ways:
– Compensation to increase the volume of oil by resilience of the tank wall )
– Using a radiator tank with rigid walls that part of the upper space of the tank is filled with an inert gas such as nitrogen and changing the volume and pressure of this gas to compensate for the change in the volume of the transformer oil.
2. Dry resin transformers
This type of transformers is oil free and the coils are resin coated and surrounded by casting and resin injection. The most important advantage of these transformers is the elimination of the risk of fire due to oil.
B) Classification of transformers in terms of type of operation and how to use
1. Power transformers that are responsible for transmitting electrical energy by changing the voltage level and are often designed as outdoor installation and ground or indoor installation of transformers indoor.
2. Ground transformers, which are in fact a transformer to create the center of the star (zero point) in the transmission posts and do not have a secondary winding to transfer energy.
3. Ground and auxiliary transformers, which are called compact, and are in fact a combination of a ground transformer with a distribution transformer in one device.
4. Special distribution transformers that are usually used to supply power to industrial units and are divided into different types in terms of specific technical specifications required by the consumer such as power, voltage, number of windings, number of phases, connections, type of load, environmental conditions, etc. Some of them can be used, such as single-phase transformers, three-wire, rectifier, furnace, with voltage adjustment switch under load, with forced cooling system, bushings coming out of the walls, with cable boxes and special protective equipment designed and Are produced pointed out.
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