Electric energy "generation, transmission, change, distribution, use" five links

Compared with the substation equipment, the transmission line is relatively simple, and its composition is also relatively simple. According to the equipment status maintenance, the transmission line is mainly divided into 7 units and 1 environment, the 7 units are poles, ground wires, insulators, fittings, pole and tower foundation, grounding devices, ancillary facilities, an environment refers to the channel environment.

3. Transmission types:

According to the nature of transmission current, transmission is divided into AC transmission and DC transmission. The first successful implementation of direct current power transmission was in the 1880s. However, because the voltage of DC transmission was difficult to continue to improve under the technical conditions at that time, the transmission capacity and benefits were limited. At the end of the 19th century, DC power transmission was gradually replaced by AC power transmission. The success of transmission ushered in a new era of electrified society in the 20th century. At present, three-phase AC power transmission is widely used, and the frequency is 50 Hertz (or 60 Hertz). Since the 1960s, DC power transmission has been developed, which is combined with AC power transmission to form a hybrid AC-DC power system

4, transmission voltage level:

The level of transmission voltage is the main symbol of the development level of transmission technology. The main voltage levels of China's transmission lines are:

Generally speaking, the larger the power capacity, the higher the voltage level used by the line. The use of ultra-high voltage transmission can effectively reduce line loss, reduce line unit cost, occupy less arable land, make full use of line corridors, reduce power loss on transmission lines and line impedance voltage drop reasons: P=U*I

According to the above formula, under the premise of constant power, increasing voltage can reduce the current, thus reducing the heat loss of the transmission line.

Third, power transformation

1, substation overview:

Substation is the power system. The rated voltage of the generator in the power system is generally below (15 ~ 20) kV by a process in which the voltage is changed from low grade to high grade (boost) or from high grade to low grade (buck) through a certain device. Commonly used transmission voltage levels are 765 kV, 500 kV, 220-110 kV, 35-60 kV, etc. Distribution voltage levels are 35-60 kV, 3-10 kV, etc. The electrical appliances of the electricity department have high-voltage electrical equipment with a rated voltage of 3 to 15 kV and low-voltage electrical equipment such as 110 volts, 220 volts, 380 volts, etc., and want to connect the different voltages to form a whole need to pass the power transformation.

2, substation classification:

There are two kinds of variable pressure: pressure boost and pressure drop:

1) Boost the pressure

In the power system, the power plant converts the natural primary energy into electricity and sends electricity to distant power users. In order to reduce the power loss and line impedance voltage drop on the transmission line, the voltage needs to be increased.

2) Reduce blood pressure

In order to meet the safety of power users, the voltage should be reduced and distributed to each user.

3. Principle of transformer parts

Transformer is the main component to achieve power transformation, its main principle is the principle of electromagnetic induction, when the transformer once apply AC voltage UI, the current flowing through the primary winding is I1, then the current will produce alternating magnetic flux in the core, so that the primary winding and secondary winding electromagnetic contact, according to the principle of electromagnetic induction, alternating magnetic through the two windings will induce electromotive force, Its size is proportional to the number of winding turns and the maximum value of the main pass, the side with more winding turns is high voltage, and the side with fewer winding turns is low voltage, when the secondary side of the transformer is open, that is, when the transformer is no-load, the secondary terminal voltage is proportional to the number of turns of the primary and secondary winding, and the transformer plays the purpose of transforming the voltage.

4. Substation - Substation

Substation is the place where the voltage and current of electric energy are transformed, concentrated and distributed in the power system. It is the intermediate link between the power plant and the power user, and the power grid of various voltage levels is connected through the substation. In order to ensure the quality of electric energy and the safety of equipment, voltage adjustment, power flow control (the flow direction and distribution of voltage, current and power in each node and branch of the power system) and protection of transmission and distribution lines and main electrical equipment are also needed in the substation.

Iv. Power Distribution

Distribution overview

Distribution refers to the network that plays the role of energy distribution in the power network. Usually refers to the low-voltage side of the secondary step-down transformer in the power system directly or after the step-down user power supply network, it is directly connected with the user in the power system and the distribution of electric energy to the user.