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

2. Distribution network composition

The distribution system consists of a distribution substation (which usually reduces the transmission voltage of the grid to the distribution voltage), a high-voltage distribution line (that is, a voltage above 1 kV), a distribution transformer, a low-voltage distribution line (a voltage below 1 kV), and the corresponding control and protection equipment.

3. Distribution network classification

Distribution according to voltage is generally divided into high voltage distribution, medium voltage distribution and low voltage distribution:

High voltage distribution voltage: 35KV, 63KV, also known as local power network;

Medium voltage distribution voltage: 10kv:

Low voltage distribution voltage: 380/220v

Distribution is divided into urban distribution network, rural distribution network and factory distribution network according to power supply area:

Urban distribution network: provides urban residents with work and life, and the load is relatively concentrated

Rural distribution network: provide electricity for agricultural production and normal rural life. Large power supply radius

Factory distribution network: provides the electric energy required for the production of industrial bases, and the load is large

Power distribution is divided into AC power supply mode and DC power supply mode according to the power supply mode:

Ac power supply mode:

Three-phase three-wire system: divided into triangular wiring (for high voltage distribution, three-phase 220 volt motor and lighting) and star wiring (for high voltage distribution, three-phase 380 volt motor)

Three-phase four-wire system: for 380/220 volts low-voltage power and lighting mixed distribution.

Three-phase two-wire one-place system: mostly used in rural power distribution.

Three-phase single-wire system: commonly used for electric railway traction power supply.

Single-phase two-wire system: mainly residential electricity.

Dc power supply mode:

Second-line system: used for urban trolleybus, subway locomotive, mine traction locomotive and other power supply;

Three-wire system: supply power plants, substations, distribution stations for their own use and secondary equipment electricity, electrolysis and electroplating electricity.

5, the main indicators of the distribution network

The distribution network mainly has the following four indicators:

Power supply reliability: Power supply reliability refers to the reliability of continuous power supply to users.

Network loss rate: The network loss rate can be defined as the ratio of the amount of energy lost by the power network to the total power supply, usually expressed in percentage.

Voltage fluctuation and voltage flicker: Voltage fluctuation refers to the rapid change of the grid voltage or the periodic change of the voltage envelope first. Voltage flicker refers to the main feeling of the human eye to the lamp flicker, causing the lamp flicker fluctuation voltage, called flicker voltage.

Voltage pass rate: The voltage pass rate refers to the percentage of the voltage pass time of a certain point in the power system in the total time within the statistical time.

Development of distribution network

The high and middle voltage distribution network is developing into a grid

Closed-loop operation

Big change of relay protection configuration

Ac scheme and light DC scheme of the grid

Superconducting of AC grid

Power flow controller is widely used

6. Power distribution

The main functions of the distribution network are as follows:

1) The main function of the distribution network is to accept electric energy from the transmission network, and distribute it step by step or consume it locally, that is, reduce the high-voltage electric energy to the various voltages that make the operation suitable for the needs of users, and form a multi-level distribution network to supply power to various users.

2), 10kv and below distribution lines for the user power supply, responsible for the transmission and distribution of electrical energy tasks.

6. Electricity

Overview of electricity use

Electricity is the process of consuming electricity through electrical appliances, is the final node of the power link, daily life is everywhere with electricity links: fluorescent lamps, computers, air conditioners, washing machines, industrial machines.

2, electricity classification

Electricity is mainly divided into four categories according to the load:

Urban electricity consumption: household appliances for urban residents, which has an annual growth trend, as well as obvious seasonal passive characteristics.

Rural electricity: electricity for rural residents and electricity for clothing production.

Commercial electricity consumption: lighting, air conditioning, power and other electricity consumption in the commercial sector covers a large area, and the growth of electricity consumption is stable, and the commercial load also has the characteristics of seasonal fluctuations.

Industrial electricity: industrial production of electricity, the proportion of general industrial electricity in the composition of electricity ranks first.

3, electricity feedback

Through the situation of electricity consumption, it can also guide the construction of power generation, transmission, transformation and distribution in the four links of the power system, so it can also be said that electricity is the first link of power "generation, transmission, change and distribution".