How should dry type transformers be equipped with lightning protection?

The high-voltage cabinet should be lightning protected and the low-voltage should be grounded.

1. Forward and reverse conversion overvoltage.

When the low-voltage side line is struck by lightning, the lightning current invades the low-voltage winding and enters the ground through the neutral grounding device, and the grounding current IJD produces a voltage drop on the grounding resistor RJD. This voltage drop causes a sharp increase in the neutral potential on the low voltage side. It is superimposed on the low-voltage winding and overvoltages occur, endangering the low-voltage windings.

At the same time, this voltage is increased to the high-voltage side by the electromagnetic induction of the high-voltage winding according to the transformation ratio, and the phase voltage of the high-voltage winding is superimposed, resulting in a dangerous overvoltage of the high-voltage winding. This phenomenon of overvoltage of the high-voltage winding caused by lightning overvoltage is transformed to the high-voltage side by electromagnetic induction, causing the overvoltage of the high-voltage winding to be called "positive transformation" overvoltage.

When the high-voltage side line is struck by lightning, the lightning current is discharged into the ground through the high-voltage side arrester, and the grounding current IJD produces a voltage drop on the grounding resistor RJD. This voltage drop acts on the neutral point on the low voltage side, and the outlet wire on the low voltage side is equivalent to grounding through the resistor, so the majority of the voltage is added to the low voltage winding. Through electromagnetic induction, this voltage drop rises to the high-voltage side in a variable ratio and is superimposed on the phase voltage of the high-voltage winding, resulting in an overvoltage of the high-voltage winding resulting in a breakdown accident.

This phenomenon of lightning strike on the high-voltage side, acting on the low-voltage side, and then transforming to the high-voltage side through electromagnetic induction, causing the overvoltage of the high-voltage winding is called "inverse conversion overvoltage".

2. The influence of different wiring of the transformer on the positive and negative conversion overvoltage.

YZN11 wiring: When the low-voltage side line is lightning, the lightning current enters the two "half-windings" on the low-voltage side, the size is equal, the direction is opposite, and the magnetic flux on each core column just cancels each other, so it will not produce positive conversion overvoltage in the high-voltage winding. In the high-voltage side of the line lightning fall, in fact, due to the transformer structure and magnetic flux leakage and other reasons caused by the asymmetry of the magnetic circuit, so the magnetic flux can not be completely offset, the forward and reverse conversion overvoltage still exists, but it is small, can be considered to have a better lightning protection effect.

YYN0 wiring: The transformer of this connection method is a standard wiring in China. It has many advantages:

Under normal conditions, it can keep the voltage of each phase unchanged, and can provide two different voltages of 380 and 220V to meet user requirements; When a single-phase ground short circuit occurs, the increase of the voltage of the other two phases can be avoided; It can avoid the danger of high pressure channeling into the low pressure side. Therefore, almost all distribution transformers in the distribution network use this connection.

First, set the arrester correctly. In order to prevent the transformer from being damaged by lightning striking the 10kV line, a set of valve-type arresters should be installed on the high and low voltage sides of the distribution transformers wiring Y0 or YY. Practice has proved that the closer the arrester is to the distribution transformer, the better the lightning protection effect.

The high and low voltage side arrester can be installed on the top cover edge of the transformer, and then the transformer shell, the arrester down conductor and the transformer neutral wire are connected together, and the three are grounded together. The grounding down conductor should be made of copper stranded wire (or steel strand) with a cross-sectional area of 25mm2, and the length should reach the shortest, so that the lightning overvoltage acting on the distribution transformer is similar to the residual voltage of the arrester, and the risk of breaking down the insulation of the transformer is reduced.

2. Regularly test the lightning arrester. In order to protect the transformer from lightning strikes, for the distribution transformer of 100kVA and soil, the lightning arrester is tested once a year, and the grounding resistance value shall not be greater than 4; Arresters below 100kva shall be calibrated once every two years, and the grounding resistance value shall not be greater than 10; Those who are unqualified should be dealt with in a timely manner.

3. Test the grounding resistance. Before the thunderstorm season (February and March) every year, the grounding resistance of the transformer is tested, and if it does not meet the specified value, measures are taken in time, and the lightning protection facilities are checked at the same time, especially the inspection of the down conductor at the soil junction and all joints to meet the requirements. In order to reduce lateral error and ensure personal safety, the ground resistance value should be measured with the ground down conductor disconnected.

Fourth, it is forbidden to apply salt to the grounded soil to reduce soil resistivity. Because salt is seriously corrosive to the grounding body, after adding salt, the grounding resistance may meet the requirements, or even very small, but after a long time, the grounding resistance is far greater than the specified value. When lightning strikes, the transformer is burned out as a result of a counterattack.

1. Erect lightning cables.

2. Improve the insulation level of the line itself.

3. Use the top line of the triangular arrangement as a lightning protection line.

4. Strengthen the protection of weak points of insulation.

5. Adopt automatic reclosing device.

6. The iron foot of the insulator is grounded.

7. Anti-direct lightning. Lightning rods are installed to protect the entire substation building from direct lightning strikes.

8. Incoming lightning protection. Install lightning protection wires in the 1-2km section of the incoming line to protect the line from direct lightning strikes, so as to avoid damage to the equipment along the lightning voltage along the substation.

9. Lightning protection of power distribution device. In order to prevent lightning shock waves from invading the substation along the high-voltage line and causing harm to the power transformer, a group of valve-type lightning arresters should be installed on each section of the bus of the substation, and should be as close to the transformer as possible.

10. Lightning protection of high-voltage motor. The FCD type magnetic blow valve X09 type arrester with better performance is used to protect the rotating motor or the metal oxide arrester with series clearance is adopted, and installed as close to the motor as possible.

11. The building where the first or flammable materials are stored is equipped with an independent lightning rod or overhead lightning cable, so that the protected building and the hood, discharge pipe and other objects protruding from the roof are within the protection range of the lightning receiver.

12. Lightning protection nets should be laid on non-metallic roofs, and all metal pipes and equipment in the room should be well grounded and there should be no open loops to prevent induced overvoltage.

13. The low-voltage line is directly buried with all cables; The overhead line adopts a cable into the home, and the metal sheath of the cable is connected to the ground of the electrical equipment; For low-voltage overhead inlet and outlet lines, lightning arresters are installed at the inlet and outlet. Overhead metal pipelines, buried or trenched metal pipes, in and out of the building, should be connected to lightning protection grounding devices.

14. Stay indoors and close doors and windows; People who work outdoors should take refuge in buildings.

15. Do not touch antennas, water pipes, barbed wire, metal doors and windows, building exterior walls, and stay away from live equipment such as wires or other similar metal devices.

16. Reduce the use of ** and portable**.

17. Do not stand on the top of a mountain, on the roof of a building or other objects close to high conductivity.

18. Do not dispose of flammable materials contained in open containers.

A lightning arrester is installed in the high-voltage cabinet or on the bus, and if the transformer is nearby, the transformer is not equipped with a lightning arrester.

If the transformer is separated from the high-voltage cabinet or bus with long-distance lines and cables, the transformer should be equipped with a lightning arrester.

High-voltage distribution cabinet refers to the electrical products used in power system power generation, transmission, distribution, power conversion and consumption to play the role of on-off, control or protection, etc., and the voltage level is in, mainly including high-voltage circuit breakers, high-voltage isolation switches and grounding switches, high-voltage load switches, high-voltage automatic reclosing and sectionalizers, high-voltage operating mechanisms, high-voltage explosion-proof distribution devices and high-voltage switchgear. The high-voltage switchgear manufacturing industry is an important part of the power transmission and transformation equipment manufacturing industry, and occupies a very important position in the entire power industry.

In the distribution room, the cable is not very long, so there is no need to reinstall it.

It can not be installed, but the low-voltage main cabinet should be installed.

It's better to install it, so it's safe.

Hello pro is very happy for you: it is not recommended to install the 10kv dry-type transformer directly under the lightning rod, this is because: 1 The lightning rod is generally installed above the transformer, so as to direct the lightning and other high-energy currents to the ground.

If the transformer is installed under the lightning rod, the lightning rod may not function properly, causing the transformer to be damaged by excessive lightning strike voltage. 2. The shell of the dry-type transformer is usually made of insulating materials, and in the case of friendly insulation performance, it can be sold to partially play the role of isolating lightning. However, if it is installed directly under the lightning rod, the closer it is to the lightning rod, its insulation performance may be affected, which in turn increases the risk of being struck by lightning.

Therefore, it is recommended to install the 10kV dry-type transformer at a distance from the antenna than the lightning rod, and the installation should be comprehensively considered and planned according to the actual situation. At the same time, in the design and selection, we should choose a suitable lightning protection scheme according to the local meteorological characteristics, lightning frequency and other factors. Hope it can help you dear.

Hello, according to the provisions of the Code for Construction and Acceptance of Electrical Equipment Installation Engineering (GB 50257-2012), the installation of 10kV dry-type transformer should follow the following principles: leave the place with more harmful gases, vapors and dust, stay away from flammable and explosive dangerous places and corrosive gas places, and should have good ventilation conditions and heat exhaust facilities. At the same time, the installation of lightning rods should also follow the relevant specifications, usually the position of the lightning rod should be higher than the highest point of the building, and a certain distance from the edge of the building.

Therefore, according to these specifications, 10kV dry-type transformers should generally not be installed under lightning rods. Of course, the specific situation also needs to be comprehensively considered according to the actual situation of the site, if there are special needs in the installation process, you can ask professional electrical engineers for design and consultation.

(1) Install lightning rods: Outdoor power distribution devices should be equipped with lightning rods to protect against direct lightning strikes.

2) Install lightning cables: substations and distribution stations in canyon areas can use lightning cables to protect against direct lightning strikes.

3) Install lightning arresters: to prevent lightning intrusion waves from harming the electrical devices of the substation, especially to the main transformer.