Dry-type transformer is a kind of important power equipment, which plays an important role in the work. It is mainly used in the fields of high-voltage power transmission, power distribution and industrial electricity, and its operation principle is based on the principle of electromagnetic induction.
One, dry power transformer definition
Epoxy cast resin dry-type transformer is an important power equipment in the power distribution system. Because epoxy resin is flame retardant, flame retardant, self-extinguishing solid insulating material, that is safe and clean. Therefore, epoxy resin casting dry-type transformer has no oil, flame retardant, low operating loss, disaster prevention capability is widely used. Relative to the oil transformer, dry-type transformer because there is no oil, there is no fire, explosion, pollution and other problems, loss and noise down to a new level, more transformers and low-voltage screen in the same distribution room to create the conditions.
Second. different types dry type transformer
1, epoxy resin casting dry-type transformer: used in insulating materials with polyester resin and epoxy resin. At present, the castable insulated dry power transformer mostly uses epoxy resin.
2, Vacuum Pressure Impregnated Transformer (VPI)
impregnated air insulated dry transformer: currently used very little. Winding wire insulation, insulating structural materials according to the need to choose different heat-resistant grades of insulation materials, made of class B, F and H insulated dry transformers.
3, winding and insulation dry type transformer: winding and insulation dry type transformer is a kind of resin insulated, now the manufacturer is less.
4, composite insulation dry type transformer: (1), high voltage winding adopts casting type, low voltage winding by dipping insulation; Adopted pouring type (2), high pressure, low pressure with copper foil, aluminum foil winding foil type winding.
Third. the structure of the dry transformer
Four. dry type transformer technical
1.dry type transformer insulation class
| A | E | B | F | H | |
| Max. temperature ℃ | 105 | 120 | 130 | 155 | 180 |
| Winding temperature rise | 60 | 75 | 80 | 100 | 125 |
| Performance reference temperature | 80 | 95 | 100 | 120 | 145 |
2、Transformer insulation level
Transformer insulation level, also known as insulation strength, is the level with the level of protection as well as other insulation part of the level, that is, withstand voltage value
LI75 AC35/AC3
LI--Lightning impact withstand voltage (75KV)
AC - frequency withstand voltage (high voltage 35KV, low voltage 3KV)
3、Temperature rise, cooling mode
① transformer temperature rise, for air-cooled transformer is the temperature of the measurement part of the temperature and the cooling air temperature difference; for water-cooled transformer is the temperature of the measurement part of the temperature and the difference between the water temperature at the entrance of the cooler.
② transformer cooling by the type of cooling medium and the type of circulation to mark. Divided into: dry self-cooling (AN), dry air-cooled (AF), oil immersed self-cooling (ONAN), oil immersed air-cooled (ONAF), strong oil air-cooled (OFAF), strong oil-water-cooled (OFWF), strong oil-guided air-cooled and water-cooled (ODAF and ODWF).
4, no-load current, no-load loss
①When the transformer secondary winding open circuit, the primary winding to apply the rated frequency of the rated voltage, the primary winding of the current into the no-load current.
② no-load current active component is loss current, the active power drawn into the no-load loss.
5, impedance voltage, load loss
① When the secondary winding transformer is shorted, the voltage applied by the primary winding to flow the rated current is called the impedance voltage.
② The active power taken when the secondary winding is shorted and the primary winding flows the rated current is called the load loss.
Five. dry type transforme installation;
1, the transformer installation site must be clean and dry, in the infrastructure construction is not basically completed, it is best not to enter the transformer, to avoid the transformer by the site construction damage and insulation damage. Transformer mobile approach should not damage any parts on the transformer, especially fans, iron cores, external regulator connection copper rods, and high and low voltage insulators. When the transformer is installed and moved, special attention should be paid to the safety of personnel to prevent dumping and loss of control.
2, the installation of the transformer is relatively simple, (1) as long as the thermometer sensor wire is inserted into the corresponding socket of the temperature display, and the screw is fixed, (2) and the high and low pressure two groups of fan power cord connected to the corresponding temperature controller identification terminal, (3) a power cord connected to the switch, a power cord connected to the temperature controller terminal can be.
(3) The installation of the transformer must take into account the (grounding) insulation distance between the transformer coil and the metal parts, as well as the distance between the high-voltage cable joint, the high-voltage connection copper rod and the shell, and must meet the insulation distance of the voltage level to the ground. Because the high voltage connecting rod has the corresponding voltage level of the heat shrinkable insulation envelope, it can be lower than the normal insulation distance required in the air.
Six, dry transformer operation and maintenance
1, dry-type transformer running environmental requirements: rain, moisture and dust, to prevent the invasion of harmful gases and small animals. Should have the transformer effective ventilation and cooling conditions. Especially in the high temperature season, should pay attention to the indoor temperature reduction. Ventilation volume according to each kilowatt loss (P0 + PK) 3 ~ 4m3/min.kw selection. In the confined space (i.e., inside the transformer shell) the temperature around the transformer should not exceed 40 ℃, and the relative humidity of the air during operation should not exceed 95%. For coastal hot and humid areas, basements and poorly ventilated operation of the transformer, it is recommended that the transformer indoor installation of air conditioning dehumidification and cooling.
2, the transformer shift, if it is no excitation voltage regulation, should be the transformer high and low voltage power supply, experience electricity, connected to the ground wire. The three coils should be adjusted to the same position at the same time. If the output voltage is required to decrease, it is adjusted to the first gear, and if the output voltage is required to increase, it is adjusted to the n gear. At the same time, pay attention to the degree of tightening of the gear screw, it is not tight in place, and it is easy to discharge and burn the terminal, if it is too tight, the screw will be broken. So feel it. The recommended output voltage is 390 to 400V.
3. Parallel operation of transformer. Three conditions must be met: the input and output voltage are the same; The connection group is the same; Impedance voltage difference is not more than 10%. (The best capacity is similar) The phase sequence is not found before operation, generally the user has the low-voltage or high-voltage connection reversed. The measurement of the connection group of our company before the factory should be repeated several times, which should be guaranteed. Our company's factory transformer has not yet found that the connection group has errors. Unless the user changes the factory condition of the transformer.
4, transformer maintenance precautions:
transformer thermometer is generally set: fan start 100 ℃, fan stop 80 ℃, alarm 130 ℃, trip 150 ℃. (F-class insulation allowed maximum temperature 155 ℃) transformer shutdown and package during the insulation should be kept dry. - The temperature at which the fan starts should not be lowered, otherwise the fan will be easily damaged and increase energy consumption
