Technology | the difference between high voltage and low voltage, strong electricity and weak electricity

Many new friends in the electrical industry are not very clear about the concept of high voltage and low voltage. Even if they have been friends for many years, they may only contact a part of the electric family, and there is not much knowledge about the high and low voltage professions. So, the knowledge that may be in this piece is not very systematic. Here today to help us sort out what knowledge in this area, for your reference.

1. Let us first look at what is a high voltage electrical appliance:

The internationally recognized high-voltage and low-voltage electrical appliances have a boundary voltage of 1000V (1500V for DC). AC 1000V or above is a high-voltage electrical appliance, and 1000V or less is a low-voltage electrical appliance. Sometimes transformers are also included in high-voltage electrical appliances.
2. Let us see what is a low-voltage electrical appliance:

A low-voltage electrical appliance is a component or device that can manually or automatically turn the circuit on or off according to external signals and requirements to switch, control, protect, detect, change and adjust the circuit or non-electrical object. According to the working voltage of the control electric appliance, it can be divided into two categories: high-voltage control electric appliance and low-voltage control electric appliance, with the boundary of AC 1000V and DC 1500V. In general, low-voltage electrical appliances can be divided into two major categories of distribution electrical appliances and control electrical appliances, and are the basic components of complete electrical equipment. In industrial, agricultural, transportation, national defense, and people's electricity use, most of them use low-voltage power supply, so the quality of electrical components will directly affect the reliability of low-voltage power supply systems.

After the above analysis, we must see that the definition of high and low voltage is based on the AC 1000V (DC 1500V) limit. Simply put, the high voltage above 1000V is high voltage, the low voltage below 1000V is low voltage; DC and so on.

3. About the popular classification of high voltage electrical appliances

In high-voltage electrical appliances, generally according to the voltage level, the high pressure is divided into medium pressure, high pressure, ultra high pressure, and extra high pressure.

Description:

1. The dividing line between high voltage and low voltage is 1000V according to IEC standards, while China does not have 1000V voltage level, and the high voltage and low voltage dividing line is actually 3000V.

2. There is no essential difference between the so-called high pressure, ultra high pressure and extra high pressure (only as the voltage increases, the insulation requirements and safety requirements are different), but people's names are different. The boundaries are not clearly defined, but they are only customary. Therefore, the complete set of electrical reminds you: there will be differences in different versions.

3. In the above table, we saw that the nominal voltage of the power grid is lower than the rated low voltage on the equipment, in order to protect the normal operation of the equipment.

The nominal voltage and equipment voltage of the grid mentioned in the above table, I understand as follows:

1) Rated voltage of the power grid: The power grid refers to the entire power supply and distribution system, including power plants, substations, lines, and power sides; in China 10KV, 35KV refers to the rated voltage of the power grid.

2) Rated voltage of electric equipment: For the switch of our country, the rated voltage of our equipment is 12KV, 40.5KV, etc.;

It means that the 12KV power equipment (or switch) should be used for the 10KV power grid, and the 40.5KV power equipment (or switch) should be used for the 35KV power grid; because the rated voltage of the power equipment is higher than the grid rated voltage;

At present, the voltage levels commonly used in China are: 220V, 380V, 6kV, 10kV, 35kV, 110kV, 220kV, 330kV, 500kV. Power systems are generally composed of power plants, transmission lines, substations, distribution lines, and electrical equipment. A voltage line of 35 kV or more is usually called a power transmission line. Voltage lines of 10kV and below are called distribution lines. China's prescribed safety voltage is 36V, 24V, 12V.

Let me take a closer look at it.

About strong electricity: The concept of strong electricity is relative to weak electricity. The strong electricity and the weak electricity are divided by voltage, and the working voltage is strong under 220V AC, and the following is weak electricity.

Strong power generally means that the AC voltage is above 24V. Such as electric lights, sockets, etc. in the home, the voltage is 110 ~ 220V. Electrical appliances such as lighting fixtures, refrigerators, televisions, and audio equipment (inputs) in household electrical appliances are all strong electrical equipment.

Strong power category: Power engineering (10KV or above) power supply and distribution engineering (10KV/380V/220V) is a strong power. Strong electrical equipment: high voltage circuit breakers, high voltage cabinets, transformers, sockets, etc. These devices are characterized by operating voltages above 220V.

What is a strong electric box? The strong electric box is the distribution box. The voltage inside the distribution box is generally 380/220V, which is used for electric energy distribution. The following can be equipped with various electrical equipment such as lights, fans and pumps. The switch box for the house to enter the home is a type of distribution box.

What is a match? The matching group is: a battery with similar battery capacity and several batteries with similar battery voltages are used in series.

Identification of strong electricity:

(1) Strong electricity is not equal to power consumption. Many of the powerful electric power is used for power, such as electric motors, air conditioners and elevators, but strong electricity is also used for power supply of computers, televisions and other equipment. For example, the power of an electric car is a 12V battery, and it cannot be called a strong power.

(2) It cannot be demarcated by frequency or AC or DC. For example, 800KV DC transmission must be a strong power.

(3) It is not possible to divide the boundary by the current. Many high-voltage devices can operate at very low currents, while communication power supplies are low-voltage, high-current.

Classification of strong electricity:

People in the electronic world are accustomed to two parts: strong electricity (electricity) and weak electricity (information). The two are related and different. Generally speaking, the object of high-power processing is energy (electricity), which is characterized by high voltage, large current, high power and low frequency. The main considerations are to reduce losses, improve efficiency, and weak electricity. The processing object is mainly information, that is, the transmission and control of information, which is characterized by low voltage, small current, low power and high frequency. The main consideration is the effect of information transmission, such as the fidelity, speed and breadth of information transmission. ,reliability. In general, weak current projects include television engineering, communications engineering, fire engineering, security engineering, imaging engineering, etc., and integrated wiring engineering for the above projects. Weak electricity is for strong electricity. Strong electricity = (380/220), high voltage regardless.

The use of strong electricity:

In the power system, the voltage below 36v is called the safety voltage, the voltage below 1kv is called the low voltage, the voltage above 1kv is called the high voltage, and the line directly supplying the power to the user is called the distribution line. For example, the user voltage is 380/220v. It is called the low-voltage distribution line, which is the strong electricity mentioned in the home decoration (because it is the highest voltage used by the family). Strong power generally means that the AC voltage is above 24V. Such as electric lights, sockets, etc. in the home, the voltage is 110V~220V. Household electrical appliances such as lighting fixtures, electric water heaters, heaters, refrigerators, televisions, air conditioners, and audio equipment are all strong electrical equipment.

The difference between strong and weak:

Strong electricity generally refers to building power installation, lighting, sockets, and power distribution rooms. According to national standards, basically, 110V or 220 power equipment and pipelines are installed.

Weak electricity refers to fire-fighting, intelligent and other types of work. Generally, the equipment used for electricity is basically low-voltage electricity, including fire protection, network, broadcasting, building intercom, monitoring security, building automation and so on.

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