Lightning protection for 10 KV distribution transformers

With the increase in residential electricity demand, the power supply quality of the power distribution system has received widespread attention. Strengthening the operation and maintenance of the power distribution system to ensure the safety of power supply in all aspects has become the focus of power enterprises.

In the power system, the distribution transformer bears the important responsibility of power conversion. Once it is damaged, the power supply of the power system will be forced to be interrupted.

Analyzing the main reasons for the damage of the distribution transformer, the level of insulation protection configuration determines the safety of the distribution transformer to a certain extent. When a lightning strike occurs, an overvoltage that the distribution transformer cannot withstand is formed inside, resulting in equipment damage.

From the basic situation of the distribution network construction, the laying area of ​​the distribution network is relatively large. Considering the economic cost, there is generally no special lightning protection line along with the distribution network, and the insulation level of the distribution network is low, which directly increases The risk of lightning strikes and the hazards of lightning overvoltages.

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Table of Contents

10KV lightning protection standard for distribution transformers

10 kV transformer
10 kV transformer

Doing a good job of lightning protection of distribution transformers and reducing the risk of damage to the transformer by lightning is of great significance to the safe and stable operation of the distribution network.

According to the design of lightning overvoltage protection, it needs to include the design of line lightning shielding, lightning intrusion wave overvoltage protection, etc.

The lightning protection design of the substation needs to combine the operating experience of the substation, the topography, the existing distribution lines in the area, and the intensity of lightning activities.

Carry out calculation analysis and technical and economic comparison, follow the principle of differentiation, and determine the protection plan.

For 10 kV distribution transformers, Y or Yn wiring is widely used at present.

According to the requirements of the design regulations, in addition to installing a lightning arrester on the high-voltage side, a complete over-voltage protection scheme should also design a lightning arrester on the low-voltage side, and reasonably control the distance between the arrester and the transformer.

In the overvoltage protection operation, many distribution transformers are not protected by lightning arresters on the low-voltage side, which undoubtedly affects the lightning protection effect;

However, the transformers equipped with lightning arresters on the high and low voltage sides have not escaped the threat of lightning damage. It can be seen that the protective effect of installing lightning arresters on the low voltage side is effective.

From the perspective of the installation method of the lightning arrester, it is necessary to ensure the lightning protection effect.

The lightning arrester should be as close as possible to the transformer, installed between the transformer and the high-voltage fuse, and the “three-in-one” grounding method should be adopted when wiring.

Experimental results show that the closer the distance between the arrester and the transformer, the better the protection effect.

Problems in lightning protection of 10KV distribution transformers

The problem of grounding down conductor

The length of the ground down conductor in the lightning protection of 10KV distribution transformers does not meet the design requirements;

First of all, the length is relatively too short, which has no effect of leakage current in the power distribution protection of the distribution transformer, which will increase the current carried by the down conductor, which will lead to safety accidents.

Secondly, the structure of the down conductor is unstable, and some parts are not fixed with clips.

Because long-term wind and sun will cause the down conductor to become loose, when a lightning strike is received, the lightning impulse current will also directly cause the ground down conductor that is not fixed by the clip to be pulled up from the soil surface. This will lead to human life safety issues.

Finally, because the grounding down conductor has not been treated with reasonable anti-corrosion technology, the insulation surface of the down conductor will be damaged during a long period of low temperature and high-temperature weather.

This shortens its service life. At the same time, damage to the surface of the ground down conductor will lead to the failure of its leakage function and diversion function, causing a safety accident.

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The installation point of the arrester is unreasonable

There is no corresponding lightning arrester installed on the low-voltage side of the 10KV power distribution to protect it. The occurrence of this problem will produce forward and inverse transformed voltages, which will directly lead to damage to the insulation of the distribution transformer.

In addition, there is no lightning protection device installed on the side of the power user’s incoming line.

If there is a current short-circuit fault inside the user, especially those high-voltage users, the fault situation will change.

In severe cases, it will cause distribution transformer failures, which will affect a large area of ​​power outages in the distribution network.

2.3 Lack of lightning protection measures for the low-voltage side of 10KV distribution transformers

The low-voltage side of the 10KV distribution transformer lacks lightning protection. When lightning enters the power distribution from the low-voltage side, it will cause damage to the low-voltage side winding of the power distribution.

In addition, when the current appears in the high-voltage winding, it will directly threaten the insulation of the high-voltage winding layer and cause safety accidents.


Lightning protection measures for 10KV distribution transformers

Install lightning arrester

In the lightning protection of 10KV distribution transformers, a lightning arrester needs to be installed on the high-voltage side, and its installation location needs to be close to the transformer. This installation method can become a relatively high lightning protection measure.

Judging from the actual effect, this protective measure did not significantly reduce the lightning risk of the transformer.

Under the situation that the protective effect of the existing measures is not ideal, some scholars have started to improve the protection technology, conducted a series of simulation experiments, and proposed more reliable protection measures, one of which is the installation of lightning arresters.

It can be seen from the results of the simulation experiment that the installation of a lightning arrester on the high-voltage side can protect the insulation of the installation place by clamping the potential;

Then install a lightning arrester on the low-voltage side, which can protect the weak points of the original protective measures.

In order to avoid the problem of residual voltage superimposition and voltage drop, the installation method of the arrester needs to be connected to the transformer shell and the tap of the low-voltage bushing at both ends of the arrester, and form a “four-point integrated” connection form.

Therefore, in the lightning protection of distribution transformers, zinc oxide lightning arresters can be selected for distribution lines, and the parts of the distribution lines that are easily hit by the current can be used for comprehensive lightning protection for distribution transformers, switches, and other lines.

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Set the ground down conductor scientifically

The length of the down conductor between the housing of the 10KV distribution transformer and the arrester needs to be shortened, otherwise, the voltage drop will increase.

When the surge arrester and the current caused by the voltage drop due to lightning strikes are superimposed, it will damage the insulation of the distribution transformer.

In addition, relevant personnel is required to fix the ground down conductor with clips, so as to ensure that the ground down conductor is deeply pierced in the soil and the structure is stable.

At the same time, it is also necessary to do a good job of anti-corrosion technical treatment for the ground electrode and the ground down conductor and strengthen the anti-corrosion ability of the surface of the ground electrode and the ground down conductor.

This can not only guarantee the service life of the ground down conductor but also make its leakage and diversion effect more stable.

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Protection of coil insulation performance and material performance

In the lightning protection process of 10KV distribution transformers, the handling of short-circuit faults requires relevant technical personnel to ensure the insulation performance of the coil insulation accessories.

In optimizing the related test of its performance, it is necessary to avoid the occurrence of related problems such as internal leakage or power connection, which can promote the normal and stable operation of the transformer equipment to a certain extent.

Thereby directly improving the stability and safety of the entire power system operation.

And in the actual installation process, materials with higher requirements must be used, and attention must be paid to the installation position of the transformer, which must be in a dry place, so as to ensure the service life of the transformer.

The protection of the material performance of the 10KV distribution transformer mainly means that in the process of dealing with the lightning short-circuit fault of the distribution transformer, we must pay attention to the material of the winding and the use of related performance.

In the actual selection process of transformer winding materials, the actual conditions of the various parameter data of the transformer must be combined, so that the overall mechanism of the distribution transformer can be more coordinated, and it can also ensure its scientific and reasonable operation.

At the same time, during the selection and use of transformer winding materials, mechanical resistance and short-circuit resistance strength must also be ensured, so as to improve the actual use efficiency of the transformer as a whole.

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Design and structure of lightning protection rod

The design of lightning protection rods can satisfy the electrical characteristics of lightning strikes to the utmost extent, and to a certain extent also fully consider the relevant mechanical properties required in overhead circuits.

This can reduce the current shielding rate. To a certain extent, it is installed in the overhead ground wire required in the overhead line and has a certain torsion ability for the circulation capacity and grip strength required by the overhead ground wire.

Because the lightning rod is a special kind of hardware, it must ensure the corresponding length of the needle bar, and a counterweight ball must be set on the needle bar to maintain its balance.

In order to meet the performance of overhead transmission lines, it is necessary to have sufficient grip strength for the lightning protection rod.

In this way, designers can fully use the special hardware of lightning rod without destroying the ground wire.

This can also make its own quality have uneven anti-icing ability, thereby ensuring the actual effect of the lightning rod.

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The specific installation and application of lightning protection rods

There are many models of current lightning protection rods for shielding strikes, and different models can be applied to different lightning protection ranges.

First of all, the installation process of the lightning protection rod is to clamp the needle bar of the lightning rod in the lower hole position, and then assemble the balance ball and sleeve, spring washer, nut, and other processes. The relevant installer must follow the requirements of the relevant design regulations. The line for construction;

Second, it is necessary to install matching protective wire on the overhead ground wire. The protective wire can protect the surface of the transmission line from corrosion and damage, increase its service life, and maximize the insulation capacity of the surface of the transmission line;

The third is to install the wire clip in the middle of the protective wire, and then fix it;

Fourth, the fourth is that the direction of the needle bar of the lightning rod must be the periphery of the line ground, so that the anti-vibration hammerhead faces the tower head to a certain extent, in order to fully ensure the effect of lightning protection and grounding.

These all need to set up an independent grounding body, such as steel pipes, round steel, etc., but also need to check the relevant resistance parameters of the grounding body, to determine whether the grounding body can be installed safely, and to ensure its stability.

To a certain extent, fix the steel bars in place, ensure that someone is in possession of the scaffolding and other construction equipment at the installation site, and ensure construction safety to a certain extent, so as to ensure the lightning protection effect of the transmission line.

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Use intermittent and lightning arrester cooperation to protect 10KV distribution lines

Use of parallel gap insulators;

To a certain extent, the insulation coordination between the protection gap and the line insulator string needs to be based on the related function of the protection gap.

In this process, the design of the protection gap distance is required to capture the root of the arc when the line flashover is accumulated, and gradually guide the equipment fault current into the underground, which can protect the line parts, insulators, and wires.

This will also increase the service life of the line and ensure that the lightning can be smoothly led into the ground, playing a protective role for the 10KV distribution transformer.

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In short, the lightning protection of 10KV distribution transformers is extremely important.

Because it is the key to protecting the safe operation of the surrounding power system.

Therefore, the problems that arise during the lightning protection process require relevant personnel to conduct in-depth research and troubleshoot the problems, so as to ensure that the role of lightning protection is reflected.

Therefore, in order to protect the lightning protection of 10KV distribution transformers, it needs to be optimized and improved accordingly to solve hidden dangers.

Only in this way can it be ensured that when the 10KV distribution transformer is subjected to lightning, the probability of accidents can be reduced, and the safe operation of the distribution network can be guaranteed.

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