News Category

Electrical knowledge

Transformer operation details

Views : 172
Update time : 2018-06-08 14:51:24
1.the transformer should be fitted with nameplate. The nameplate shall indicate the manufacturer's name, rated capacity, rated capacity once or twice, once or twice rated voltage, current, impedance, voltage and wiring group and other technical data. Transformer capacity, specifications and models must meet the design requirements. Accessories spare parts complete, and the factory certificate and technical documents. Steel: a variety of steel sections should meet the design requirements, there is no significant corrosion. Bolt: In addition to anchor bolts and shockproof bolts, galvanized bolts should be used, with the corresponding flat washers and spring pad. Other materials: welding electrodes, antirust paint, paint and other adjustments should be consistent with the design requirements, and product certification.

2.operating conditions
Construction drawings and technical information is complete. Construction of the basic construction is completed, elevation, size, structure and embedded strength meet the design requirements. Roofing, roof shotcrete is completed, the roof without water, doors and windows and glass installed in good condition. The indoor rough ground engineering is over, the site is clean and the road is smooth.

3.operating process
transformer transformer installed in place can be used directly thrown into the transformer car indoors, or set up a temporary track with road wood, with three steps to take, hanging chain to the temporary track orbit, and then use the chain into the indoor suitable position. Transformer in place, should pay attention to its position and distance from the wall and the drawings consistent with the allowable error of ± 25mm, drawing without marking, according to the vertical track in place, the distance from the wall not less than 800mm, from the door shall not be less than 1000mm. Transformer bench installation: double pole installation transformer, two of the root open to 2m. Distribution transformer stand with two or four channels fixed to the two poles, the height of the platform from the ground of not less than 25m, the plane slope of not more than 1/100. Waist bar should be used with a diameter of not less than 4mm wire wound more than two laps, winding should be tight, waist bar from the live part of not less than 0.2m. At the same time high-voltage transformer stigma installed dust cover, transformer hanging warning signs.

 Drop-out fuse installation Transformer high and low voltage side should be equipped with fuses. The vertical height of the bottom of the high-voltage side fuse to the ground is not less than 4.5m, the horizontal distance of each phase fuse should not be less than 0.5m, in order to facilitate the operation and fuse fuse fuse box can fall down smoothly, drop-type fuse The axis of the device should be at a 15 ° ~ 30 ° angle to the vertical. The vertical distance between the bottom of the low-voltage side fuse and the ground is not less than 3.5m and the horizontal distance of each phase fuse is not less than 0.2m. Drop fuse fuse selection according to "ensure that the distribution transformer internal or high, low-voltage outlet casing short circuit occurs quickly fuse" principle to choose, the fuse blow time must be less than or equal to 0.1s. According to rules and regulations: the capacity of 100kVA and below, the high-voltage side of the fuse rated current transformer capacity by the rated current of 2 to 3 times the selection; capacity of 100kVA or more, high-voltage side of the fuse rated current transformer capacity rated current of 1.5 to 2 Times choice. Low voltage side of the fuse fuse selection by the low voltage side of the rated current.

 Arrester Installation and Operation Experience Proof: The external danger affecting the safe operation of distribution transformers is mostly caused by lightning accidents. Therefore, the transformer should be equipped with lightning protection device. I Bureau of non-gap composite insulation jacket metal oxide surge arresters instead of the original valve-type ceramic surge arresters, the power frequency voltage tolerance, good sealing, protection and stability. Arrester should be installed between the fuse and the transformer, and as close to the transformer. This will not only effectively protect the transformer, and easy maintenance. In addition, low-voltage surge arresters should also be installed on the low-voltage side in order to prevent intrusion of inverse converted waves and low-voltage side lightning waves. In order to avoid lightning current in the grounding resistance of the voltage drop and arrester residual voltage superimposed together on the transformer insulation, the arrester should be grounded end, the transformer shell and low voltage side of the neutral point with a cross section of not less than 25mm2 more shares Copper plastic wire connected together, and then leads to the ground device connected to the line.

 Grounding Device In the transformation of rural power grid, rural small-capacity transformers are distributed more frequently. During the thunderstorm season, 10kV distribution transformers often suffer from lightning strikes. As the grounding resistance is too large to reach the prescribed value, the lightning current can not rapidly escape into the earth and cause the arrester itself Residual pressure is too large, or in the grounding resistance have a high voltage drop, causing the transformer burned accident. Therefore, the grounding resistance of the grounding device must comply with the regulations. For 10kV distribution transformers: the capacity below 100kVA, the grounding resistance should not exceed 10Ω; capacity above 100kVA, the grounding resistance should not exceed 4Ω. Grounding device construction should be completed grounding resistance test, before passing back to earth. At the same time, the transformer housing must be well grounded, the housing ground application bolts tightened, welding can not be directly welded, in order to overhaul. The part of the grounding device consists of a horizontal grounding body and a vertical grounding body. The horizontal grounding body adopts a 40 × 4mm flat steel with a length of 6m, while the vertical grounding body adopts 3 L50 × 50 × 5mm angles with a length of 2m Respectively with the horizontal grounding welding. Horizontal grounding body buried in the soil depth of 0.6 ~ 0.8m, vertical grounding body is based on the level of grounding into the ground. Ground lead wire with 40 × 4mm flat steel, in order to test the convenience and safety of electricity, for the column-mounted transformer, lead wire connection point should be located in the channel under the transformer.

 Changeable drop lines Newly built and renovated changeable drop lines should be insulated wire, the cross section should be according to the rated capacity of the transformer, but the high voltage side lead wire copper core should not be less than 16mm2, aluminum core should not be less than 25mm2 , To eliminate the use of single-wire and unqualified wire. At the same time should take into account the fall of the safety of buildings around the distance.

4. Transformer handover test
Transformer handover test: measure the DC resistance of the coil together with the bushing; check the transformer ratio of all taps; check the wiring group of the three-phase transformer and the polarity of the individual transformer leads; together with the bushing Insulation resistance; coil together with the casing to do AC voltage withstand test.

5.Transformer power transmission check
Transformer power transmission test before doing a comprehensive inspection to confirm compliance with the commissioning conditions before they can be put into operation. Before the transformer is put into operation, it must be checked by the quality supervision department. Transformer test before the test content; ① a variety of handover test documents are complete, the data meet the requirements. ② transformer should be cleaned, wipe clean, no debris left on the top cover, body and accessories without defect. ③ transformer, the second lead phase is correct, good insulation. ④ ground wire is good. ⑤ ventilation installation is completed, working properly. ⑥ signs hanging, door lock.

6.Transformer power transmission test run acceptance
Send electricity test run: When the pressure vessel is put into for the first time, the full pressure impact can be switched on and the impact can be normally input by the high pressure side when closing. After the first power transformer, the duration should not be less than 10min, no abnormalities. Transformer should be 3 to 5 times the total pressure impact switch, there is no abnormal situation, magnetizing inrush should not cause malfunction of protective devices. Transformer test run should pay attention to the impact of current, no-load current, a secondary voltage, temperature. And make a detailed record. Transformer no-load operation 24 hours, no abnormalities, can be put into operation.
① transformer starts charging, no abnormal situation after 24H, should handle the acceptance procedures.
② acceptance should hand over the following information and documents: Change the design certificate. Product manuals, test reports, certificates and installation drawings and other technical documents. Installation inspection and adjustment records.