Almost every power transformer heats up during operation due to natural physical processes. With severe overheating, the insulation wears out, which leads to premature failure of the device. To reduce the negative impact of this phenomenon, the magnetic circuit, windings and other parts should be cooled. For this, various transformer cooling systems are used.
The main difference between the latter is associated with the environment in which the equipment is located and the introduction of additional devices for temperature control. Please note that modern transformers use oil, water, air cooling. Dry devices should be sent to a separate category.
Markings and types of transformer cooling systems
The marking and type are determined in accordance with the state standard GOST 11677-75. The full specification and gradation is written here. Consider each group individually:
- C - dry transformers, which due to their peculiarities can use natural air cooling. Some variations are supplied with forced air circulation and are designated as SD.
- M - power equipment with natural oil and air cooling. They are mainly used for distribution networks with low transformer power. In large substations, there are variations with forced circulation of MC, NMC oil.
- D - equipment that has natural cooling of oil and forced air. There are several variations of DC and NDC, depending on the additions in the form of circulation of the process fluid.
- H - the presented type is less common, since non-combustible dielectrics are used for implementation. In most cases, such products are less susceptible to explosions, which ensures greater safety for people and the substation as a whole.
It should be noted that in modern practice there are foreign gradations in this direction. Almost all of these transformer cooling systems are duplicated in the relevant standards.
Main advantages and disadvantages
Practical of each type is accompanied by a number of technical features, advantages and disadvantages. Next, we present the main criteria by which positive or negative positions are determined:
- Temperature level. The main purpose of cooling is to maintain a natural, supportive working environment for equipment. The latter is largely determined by the installation environment, the load level of power plants.
- Cost of sales. Almost every energy supply company seeks to reduce equipment costs, so it uses old proven solutions in the form of oil cooling.
- Degree of security. This is an important criterion, which involves the application of a solution at different energy facilities. For nuclear power plants, it is preferable to use more modern and rational proposals to maintain the desired temperature regime. When at a substation of a distribution network with small currents, a variant of type C can be used
Please note that in Russia, Belarus, and Ukraine, power transformers are used with the cooling system of NMC and NDC.
Type M cooling
The presented type is considered the most common due to its relative cheapness, extended service life and some other features. Oil-filled transformers with natural oil circulation and without additional blowing are used at distribution network substations. The cooling system of the transformer M has some nuances of operation:
- The need to monitor oil levels and gas extraction to determine the state of the art. Attendants must visit the distribution substation at least once every six months.
- The design must be airtight. Traces of smudges indicates the need for technical or major repairs.
The theft of oil is considered a negative factor in operation. This is a common practice when breakdown and discharge of technical fluid from the transformer tank occurs. Due to the barbaric actions, overheating and shorting of equipment is carried out with subsequent burnout.
Transformer cooling system D, DC
At large substations, the natural circulation of oil is supplemented by automatic blowing, which is triggered by an increase in temperature. The cooling system of the transformer DC has a more perfect operation, as it avoids overheating even at high loads. It should be noted that this type is the most common and will be so for several more decades. An important feature of operation is the need for proper regulation of airflow. The latter should turn on automatically provided that the temperature increases to 75 degrees, with the reverse shutdown when it decreases.
Type H Cooling
The type of cooling system for transformers N is difficult to find in modern operation. However, over time, their number will increase. As the main medium, distilled water with additives is used, which serves as a good dielectric and allows you to maintain the desired temperature. It should be noted that such a system is often combined with forced air type equipment.
As for the shortcomings - the products are priced more expensive. This moment is felt during operation, because to top up the liquid you will need to use a special solution that costs money. In the rest, the presented option takes place in modern operation at substations of various types.
Cooling options C, SG
Unlike transformer oil cooling systems, Type C variants do not use any liquid to adjust temperature conditions. Temperature reduction is carried out by natural air circulation, which is acceptable in the following cases:
- Transformer up to 63 kVA, which have a normal operating environment and low load.
- Power equipment that is used in low temperature conditions.
- Temporary construction site where the duration of use of the products is not important.
In other cases, it is recommended to focus on the solutions described above. This will extend the service life and save significant money.
Which option to give preference?
There is no single answer to this question, since there are many factors that determine the solution. As practice shows, in the modern market transformers such as NDC and NMC are used, which are accompanied by natural circulation of oil and forced air supply. Such products have increased resistance to temperature extremes, creates a protective film that prolongs the life of the equipment.
Along with this, there are more advanced and safer technologies that help to avoid force majeure situations. For example, fires in substations when all the outdoor switchgear equipment is completely burned out. It is necessary to move forward to technological progress, but also not to forget about the achievements of past years. After all, old equipment will have to work for a very long time.
Conclusion
Power equipment of substations is in constant operation and heats up under the influence of physical phenomena. With an increase in workload, the temperature will increase and lead to burnout of the working elements. To extend the service life, various transformer cooling systems are used. In modern practice, options with the air, oil and water methods of adjusting the environment are used.
The choice of cooling method is largely determined by a number of criteria, among which one can single out the cost, the possibility of creating a support system, and environmental features. At substations 220/110/35/10, mainly the type of NMC and NDC are used, which are considered combined.