How Much You Know To Purchase The 12.5 mva Transformer In 2022?

Whether you are a farmer, a hotel owner, a principal, a Bitcoin mining user, or even an individual. You will both need transformers.
If your technical engineer tells you that we need one or several 12.5MVA transformers, do you know what to do to buy the most suitable 12.5MVA transformer?
First of all, you need to understand a certain knowledge of transformers.
For a 12.5MVA transformer, it is certain that it must be a power transformer; not a pole mounted transformer or pad mounted transformer.
Second, you need to find the right supplier.
Beijing Daelim Transformer as a professional transformer supplier, has ability to design and produce transformers according to ANSI/IEEE/CSA/IEC/EU/NZ/AS ... etc standards, also have UL listing when exporting.

   



Daelim team always based on the principle of DAELIM, AT A EDGE, owns professional engineer team and sales team, have exported hundreds of transformers to USA and Canada market.
Exporting for 16 years, serving customers on 5 continents, it has been widely recognized by customers all over the world. 
Let’s check what our customers’ evaluation together~

Why Are Transformers Rated MVA?
How About The 12.47KV Distribution Transformer's Connection Method?
What Causes The Oil Leakage Of 12.5MVA Transformer?
Why Are Lightning Rods Erected In 35KV Substations?
How To Distinguish The High And Low Voltage?

What Is The Moisture Absorber For A 12.5MVA Transformer?

What Are The Factors That Affect The Price Of 12.5MVA Transformers?


Why Are Transformers Rated MVA?

The rated capacity of the transformer refers to the rated value of the apparent power. The capacity indicated on the nameplate of the transformer is the rated capacity, which is the product of the rated no-load voltage, rated current and corresponding coefficient.  For a three-phase transformer, the rated capacity is equal to = 3 × rated phase voltage × phase current, and the rated capacity is generally expressed in kVA or MVA.
1MVA=1000KVA, from this point of view, MVA is a simplified version of KVA. Generally, power transformer is more commonly used for MVA.

How About The 12.47KV Distribution Transformer's Connection Method?
Commonly used 12.47KV distribution transformers have two connection methods: Dyn1 and YNyn0
How to choose the right wiring method?
Dyn1 wiring method
The wiring method of Dyn11 is shown in the figure below. Single-phase short-circuit and three-phase short-circuit current are similar in magnitude to the overall short-circuit current.
Zero sequence current and third harmonic current can only flow in the closed loop of high voltage delta connection, but they cannot flow in star connection.
The chaining of triangles can solve the problem of partial phase operations:
When the three-phase load on the low-voltage side runs unbalanced, this connection method does not drift the potential-voltage neutral point on the low-voltage side, and the output voltage pass rate of each phase is high.
When the fuse of one phase on the high-voltage side is blown, it will not affect the other two-phase loads.

YNyn0 wiring method
The wiring method of YNyn0 is shown in the figure below.
The advantage of using this connection method is that when one phase of the high-voltage fuse is blown, the voltage of the other two phases will not be affected, and the power outage range can be reduced to 1/3.
In this case, the lighting load of the single-phase power supply on the low-voltage side will not be affected, but the three-phase power supply is different, and it needs to be equipped with a phase loss protection device to avoid burning the power load due to phase loss operation.
Daelim's engineers remind you that only iron-core transformers with a capacity of 1600kVA and below are allowed to use Yyn0 connection.

Sometimes Daelim's customers will request to change the YNyn0 connection transformer to Dyn1 connection, which requires engineers to redesign.
This is because of the requirements of dielectric strength, YNyn0 has lower requirements than Dyn1, and the neutral current of the YNyn0 connection transformer should not be too large.

What Causes The Oil Leakage Of 12.5MVA Transformer?

 



1. The manufacturing defects and material problems of the 12.5MVA transformer lead to the phenomenon of pores, blisters, virtual welding, and de-soldering, thereby causing the transformer to leak oil;
2. The installation is not in place, the flange connection is not flat, and the gasket around the gasket cannot be evenly stressed during installation; another point is that when the gasket is installed, the amount of compression is insufficient, the operating temperature of the transformer increases, and the oil becomes thinner, resulting in oil leakage of the transformer, compression The amount is too large, and the gasket is seriously deformed;
3. The quality of the plate butterfly valve is poor, and the transformer with a long production date, the connection surface of the ordinary plate butterfly valve used is relatively rough and thin, which can easily cause oil leakage of the transformer;
4. The aging, cracking and deformation of the sealant lead to the failure of the rubber seal and the cracking of the weld;
5. Improper consignment, collision of parts and incorrect hoisting and transportation during consignment and construction and transportation, resulting in parts being damaged and deformed, welding openings, cracks, etc., resulting in oil leakage.
Beijing Dalin has rich experience in exporting transformers and has advanced technology. The 12.5MVA transformer designed and produced by Daelim can well avoid this problem.

Why Are Lightning Rods Erected In 35KV Substations?
The lightning strike suffered by the 35kv substation is the downward lightning. The downward lightning will directly strike the electrical equipment of the substation, or the lightning wave formed by the induced lightning overvoltage and the direct lightning overvoltage of the overhead line will invade the substation along the line.

Therefore, avoiding direct lightning strikes and lightning waves from damaging the incoming lines and transformers of substations has become the key to lightning protection in substations. Usually, the substation is realized by installing lightning rods.

The lightning rod is a lightning receiver that protects electrical equipment and buildings from direct lightning strikes. Its function is to attract lightning to the lightning rod and safely introduce the lightning current into the ground, thereby protecting the equipment.

When installing lightning rods in substations, all equipment should be within the protection range of lightning rods.
In addition, measures should be taken to prevent counterattack accidents when lightning strikes the lightning rod.

For 35kV substations, independent lightning rods must be installed to protect the safety of outdoor equipment and structures.
The distance between the independent lightning rod and its grounding device and the protected buildings and cables and other metal objects should not be less than five meters. The underground distance between the main grounding grid and the independent lightning rod should not be less than three meters. The grounding resistance shall not be greater than 10Ω, and shall meet the requirements of no counterattack accident.

For substations of 110kV and above, the installation of lightning rods is the main measure for direct lightning protection.
Due to the high insulation level of this type of voltage level power distribution device, the lightning rod can be directly installed on the structure of the power distribution device, and the underground connection point between the lightning rod and the main grounding grid should be longer than 15 meters along the grounding body.

Therefore, the high potential generated by the lightning rod will not cause a counterattack accident of electrical equipment.

How To Distinguish The High And Low Voltage?

 

   



Low voltage: below 1000V
Medium Voltage: 10kV, 20kV, 35kV
High Voltage/Ultra High Voltage: 110kV, 220kV, 330kV, 500kV

 

What Is The Moisture Absorber For A 12.5MVA Transformer?
12.5MVA oil immersed Power transformer transformers will be equipped with moisture absorbers.
A dehumidifier, also known as an air filter, is a round glass container. It has the functions of preventing moisture and anti-deterioration of transformer oil, so as to maintain good insulating properties of insulating oil.

The moisture absorber is installed on the respirator line of the transformer oil pillow.
The upper end is connected to the oil surface in the oil conservator through the joint pipe, and the lower end is the inlet and outlet of the air, which is communicated with the atmosphere through the oil seal, which can play the role of breathing. However, the container will be filled with hygroscopic materials such as silica gel or activated alumina.

The working principle of the moisture absorber is as follows: when the temperature of the transformer decreases, the volume of insulating oil shrinks, and the oil level in the oil conservator drops. The oil level in the lower oil seal of the moisture absorber has changed.
When the oil level in the outer oil chamber of the oil seal continues to drop to the edge of the cylindrical cylinder exposed in the oil valve, the outside air will break through the oil valve, and enter the oil conservator after being filtered by the moisture absorption device, and the moisture and impurities in the air will be adsorbed. On the absorbent in the dehumidifier.
When the temperature of the transformer rises, the volume of the transformer oil expands, creating pressure on the air in the oil conservator, and the process is the opposite of the above. Usually the moisture absorber is suspended under the oil conservator.

The moisture absorbing agent in the moisture absorber is a spherical, rod-shaped or irregular block-shaped porous fixed substance with strong moisture absorption function.
After the moisture absorbing agent has been used for a long time and is damp, the adsorption efficiency will be reduced, and it must be replaced with a new product or regenerated.
The regeneration of the moisture absorbent adopts the baking method.
For example, dehydration regeneration is performed by using an electric heating furnace, a drying furnace or a hot air furnace.
Different types of silica gel have different baking temperatures: generally coarse-pored silica gel 400~500 °C; fine-pored silica gel ≤ 250 ° C; blue silica gel ≤ 120 ° C.
Due to the poor heat transfer performance of silica gel, the thickness of silica gel stacking during baking is preferably 20~50mm. When the silica gel is baked to its original color, the regeneration is considered complete.
In order to improve the moisture absorption performance, the silica gel is preferably impregnated with calcium chloride solution, and the silica gel impregnated with calcium chloride solution is white.
But this kind of silica gel is not easy to distinguish after it is wet.
In order to indicate the moisture level of the silica gel, color-changing silica gel can be used.
The color-changing silica gel must be impregnated with a calcium chloride solution to give it a light blue color.
The moisture absorption performance of color-changing silica gel is not as good as that of white silica gel.
Therefore, the amount of color-changing silica gel used does not need to be too large. It can be installed in a place where the moisture absorber can be easily observed.
When the color-changing silica gel changes from light blue to pink, it proves that the silica gel in the moisture absorber has been damp and must be replaced or dried.
If activated aluminum chloride is used as a moisture absorbing agent, during regeneration, the activated aluminum chloride can be heated to 450~500℃ with an electric heating furnace until the original white color is restored. When heating, the temperature should be strictly controlled not to exceed 500 ℃.

 

 


 

What Are The Factors That Affect The Price Of 12.5MVA Transformers?
The price of Dalin's export 12.5MVA transformer is mainly affected by the following two aspects:
1. Transformer material
Commonly used transformer materials include copper, aluminum, silicon steel sheet, fuel tank material, insulating oil and accessories.
The regular configuration price will be lower, on the contrary, the higher the configuration, the higher the price. It depends on the specific needs of customers.
2. Industry influence
Transformers are related to many industries, such as the transportation industry. If there is a boom, the demand for transformers will be large and the price will be high. If there is a recession, the demand will be small and the price will be lower.
For pricing and professional transformer solutions, please feel free to contact Daelim Transformer Team.


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