High Voltage Transformer Guide In 2022
High voltage transformers are not common in our daily life. It can only be seen on the outskirts of the city or near power plants. However, it plays a vital role in the development of a city and a country's livelihood/economy. Today, let's talk about high voltage transformers.
What is a high voltage transformer?
Internationally, it is generally divided according to voltage level: high-voltage transformers usually refer to transformers with a voltage of 66-220 kV; medium-voltage transformers with a voltage of 3-35kV; low-voltage transformers with a voltage of less than 1kv. The voltage of the ultra-high voltage transformer is higher than 330 kV and less than 1000 kV; the ultra-high voltage refers to the transformer with a voltage greater than or equal to 1000 kV.
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What are high voltage transformers used for?
We all know that the role of the transformer is to change the voltage of the alternating current. There are generally two types of high-voltage transformers: step-up transformers and step-down transformers. The function of the step-up transformer is to increase the voltage, and the function of the step-down transformer is to reduce the voltage.
High voltage step-up transformer
Generally, the output voltage of the generator set is 3-20kv, and the voltage is relatively low. If it is directly transmitted, the power loss in the line will be very huge. So, in order to reduce the power loss and reduce the current in the transmission line, we need to increase the voltage of the transmission line. Therefore, the electricity from the power plant must first pass through the high-voltage step-up transformer to increase the voltage to 35-500kv; the efficiency of the high-voltage transformer can reach more than 98%. During the transmission process of high-voltage electrical energy, the loss of electrical energy can be greatly reduced.
High voltage step-down transformer
Whether it is industrial electricity or residential electricity, the voltage is not more than 500v alternating current. As we mentioned above, the power generated by the power plant needs to be boosted by a step-up transformer to continue to transmit power. When the high-voltage transmission line is sent to the substation in the power receiving area, a step-down transformer is required to reduce the voltage to 6-10kv, and finally, the high-voltage distribution line is sent to the power distribution station to reduce the voltage to 220/380v for users to use.
Electric energy needs to go through many times of step-downs in the process of being transported to the power-consuming area, and the step-down process is all realized by the transformer.
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How do high voltage transformers work?
The working principle of a high-voltage transformer is the same as that of a generator, which is based on the principle of electromagnetic induction. The incoming coil (primary side coil) of the transformer is energized to generate a fluctuating magnetic field through the iron core. The fluctuating magnetic field passes through the secondary coil of the iron core, causing the secondary coil to generate a fluctuating electric field and electromotive force. The number of turns of the primary and secondary coils of the iron core is different, which determines the difference between the input and output voltages. The more turns of the coil, the higher the voltage; the smaller the number of turns of the coil, the lower the voltage. Therefore, the volume of the high-voltage transformer is usually relatively large.
What is the difference between LV and HV?
LV is short for low voltage; HV is short for high voltage. In a transformer, there will be a low voltage side and a high voltage side. So how do we identify the high and low voltage of the transformer and what is the difference?
1. Uppercase and lowercase letters through the transformer bushing
Generally, the high-voltage side is usually marked with capital letters ABC, and the low-voltage side usually marked with lowercase letters abc
The insulation performance of the high-voltage side bushing is higher than that of the low-voltage side, so the high-voltage side transformer bushing will be larger than the low-voltage side bushing. If it is a finished transformer, it can be distinguished from the bushing. The distance between the live part of the high-voltage side bushing and the box cover is large, and the cross-sectional area of the terminal is small; the low-voltage bushing is the opposite; if the transformer is only If it is the body of the device, it can be judged from the outlet of the coil: the cross-sectional area of the outlet on the high-voltage side is small, while the cross-sectional area of the outlet on the low-voltage side is larger.
3. Use a multimeter to measure the coil resistance.
The small resistance is the low-voltage side, and the large resistance is the high-voltage side.
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High voltage transformer manufacturers
There are far fewer high-voltage transformer manufacturers than medium and low-voltage transformers. Because high-voltage transformers have relatively high requirements and standards for technology, qualification, equipment, and environment. Daelim Transformer is a professional high-voltage transformer manufacturer in China, the voltage level can reach 230kv. The technical engineer team has rich experience in international transformer projects and can design and produce transformers that conform to IEEE, IEC, CSA, ANSI, AS, GOST, and other international standards.
Daelim Transformer has more than 16 years of experience in exporting transformers, high voltage transformers, and exporting to the United States, Canada, Mexico, Denmark, Ecuador, Chile, Myanmar, and other countries. High-quality transformers and efficient and professional services have won unanimous praise and long-term cooperation from customers. Famous partners include Meal, Amazon, ABB, etc.
High voltage transformer price
There are many factors that affect the price of high-voltage transformers. Here we talk about 5 relatively large price factors.
1. The voltage level and capacity of the transformer
The higher the voltage rating of the transformer, the higher the price. The larger the capacity, the higher the price.
2. Transformer accessories
High voltage transformer tap changer:
The voltage regulating switch of the transformer or the device part of the equipment, we can also call the tap changer. The tap changer of the transformer is mainly divided into a no-load voltage regulating device and an on-load voltage regulating device. These two are the voltage regulation methods when the tap changer of the voltage regulation part of the high voltage side of the transformer is not used. Usually, the cost of the on-load voltage regulator will be relatively high. An important factor affecting the price of high-voltage transformers is that the brand requirements of the pressure regulating switch, especially the pressure regulating switch of international famous brands, such as the German MR tap changer, the price of each set will be 100 times the price of ordinary brands.
The voltage regulating method of the voltage regulating switch is mainly determined according to the design of the Electric Power Engineering Design Institute, so you may have doubts, so what is the difference between the no-load voltage regulating switch and the on-load voltage regulating switch of the high-voltage transformer?
The no-load tap changer is also called non-excitation voltage regulation. That is, when the high-voltage side and the low-voltage side of the transformer are disconnected from the current source at the same time, the turns ratio of the transformer winding is changed by changing the tap on the primary voltage side, and then the turns ratio of the transformer winding is changed, so that the voltage can be adjusted. To put it simply, the voltage regulation operation can only be carried out when the transformer stops working and is powered off.
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The other is the on-load tap changer: contrary to the no-load voltage regulation switch, the voltage regulation operation can be carried out without cutting off the running transformer. This pressure regulation method is more convenient and fast.
No-load tap changer vs on-load tap changer
It can be seen from the above comprehensive introduction that the difference between the on-load tap changer and the no-load tap changer is that the off-load tap changer does not have the function of converting and adjusting the voltage gear during the operation of the transformer. During the shifting process of the pressure tap changer, the no-load tap changer has a short and temporary disconnection action. When the on-load load current is disconnected, it will cause arcing at the contacts inside the transformer. In this case, it will directly cause damage to the tap changer.
But in another case, the tap changer of the on-load voltage regulation equipment runs with the same current during the voltage regulation process, because there will be a short-circuit and excessively large dwell resistance in the middle, so there is no voltage regulation process. Temporarily disconnected. When the voltage gear is adjusted up and down step by step, there is no arcing that we mentioned above.
Obviously, we will have problems. Since the on-load tap changer can safely and effectively realize the voltage regulation function, why should we consider using the no-load tap changer?
The main reason is actually cost. Due to the above-mentioned pressure regulation process, the design of a no-load tap changer will reduce a lot of material costs in terms of accessories and internal design, resulting in cost reduction. The price of the on-load tap changer transformer is 20%-50% higher than that of the no-load tap changer transformer.
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The brand of transformer voltage regulating switch that Daelim often uses is Guizhou Long March, which is made in China. Guizhou Changzheng Electric Co., Ltd. has been specializing in the production of transformer on-load tap-changers and off-excitation tap-changers since the 1970s. It is one of the most influential on-load switch manufacturers in China. Won national awards and China intellectual property certification. Like the Huaming brand, the quality is excellent, and the price and delivery time are better than those of foreign brands.
3. Transformer oil
Transformer oil accounts for about 20% of the total weight of the transformer. Therefore, the amount of transformer oil is very large, and the cost of different transformer oils will be quite different.
Usually, the oil used in transformers is divided into mineral oil and vegetable oil. Vegetable oil is environmentally friendly and its price is higher than that of mineral oil. Imported vegetable oils such as FR3 will be about three times more expensive than regular mineral oils. Therefore, the cost of the transformer will be much higher.
We generally use mineral oil No. 25 or No. 45 that meets ANSI/IEEC standards. If FR3 or RAPO vegetable oil can be requested, Daelim can also provide it.
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4. Short-circuit impedance of high-voltage transformers
What is the short circuit impedance of a transformer?
Short circuit impedance is also called impedance voltage. Usually different international standards have different impedance values, which is an important reference for transformer suppliers. This value is usually displayed as a percentage value. Generally, the larger the impedance, the higher the manufacturing cost of the transformer, and the more expensive the transformer will be.
For owners who end up using transformers, the short-circuit impedance value is also a particularly important reference technical measure. This quantity takes into account the transmission and distribution quality of the transformer and tests the stable and reliable performance of the actual power supply system. At the same time, the most important thing is to evaluate the safety performance of transformers after series and parallel connections.
Impedance values that are too large or too small are not very good. Both the engineering designer and the transformer manufacturer must comprehensively consider this value and strictly meet the requirements of different countries and different international standards. The actual value of impedance will have an allowable error range, which we call loss tolerance. For example, in the Canadian standard CSA C 57.12.34, the impedance value of the transformer is 4% to 5.75%, and the allowable value of impedance tolerance is ±7.5%.
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5. High-voltage transformers at high altitudes
Standard transformers are all at an average altitude of 1000 meters, but there are special cases. If the transformer is used in high-altitude areas, such as in some high-altitude mountainous countries, an altitude of 4000 meters is required, which will affect the cost of the transformer.
Higher altitude means cooler temperatures and more extreme weather such as sandstorms, thunderstorms and storms, and higher UV exposure. The lower the overall working ambient temperature of the transformer, the lower the insulation withstands the voltage level required by the transformer.
When the transformer works in a low-temperature working environment, it will generate more power consumption and increase the temperature rise. In addition, a large temperature difference can easily cause damage to the internal and external seals or internal and external mechanical structures of the transformer. Naturally, high-performance requirements are put forward in the transformer design stage, which means higher costs.
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Therefore, in high altitude conditions, compared with the average altitude, we must improve the performance of the transformer, and directly increase the clearance to meet the high altitude by increasing the withstand voltage rating.
In addition, we also need to consider the spraying of the transformer sealing surface material. The main consideration is that the intensity of ultraviolet rays at high altitudes will be higher, so all internal and external spray paints need to use special anti-ultraviolet coatings to avoid high-intensity and long-term ultraviolet radiation, and the outer walls and transformers of the outer walls will fade or even fall off, affecting protection. performance and appearance.
Therefore, the price of high-voltage transformers used in high-altitude areas will be higher. You can choose according to the actual requirements and situation of yourself or the owner. Daelim can customize the most suitable and economical transformer technical solution for you according to your technical requirements.
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