Technical standards for transformer maintenance
Writer： Hengfeng you electric Time：2022-04-25 views：times
A transformer is a device that converts the voltage so that the high voltage is reduced or the low voltage is increased. It is a device that converts AC voltage, AC current and impedance. In order to ensure the normal operation of different electrical appliances and ensure the safe use of electricity.
1. Intact standard of transformer:
1) Normal operation
2) The treatment shall meet the requirements of the nameplate.
3) The oil temperature shall not exceed 85 ℃, and the oil level shall be within the specified monitoring line.
4) The sound is normal.
2. The structure is intact and the insulation performance is good
1) The preventive test indexes of coil, porcelain bushing and tap changer are qualified;
2) All indexes of transformer oil are qualified.
3. The main body is complete and clean, the parts and accessories are complete, and the technical performance is good
1) The nameplate on the shell is complete and legible.
2) According to the design regulations, it is equipped with gas relay, conservator, thermometer, moisture absorber, oil level gauge, cooling system, explosion-proof cylinder, oil regeneration device and grounding wire, and these devices have good technical performance.
3) The appearance shall be neat, the porcelain parts shall be complete without leakage, the primary and secondary auxiliary equipment shall act flexibly, and the protective devices shall be complete and reliable.
1、 Problem handling -- overload in transformer operation
The overload capacity of transformer refers to the maximum capacity it can output in a short time. All transformers are allowed to have different degrees of accident overload and normal overload according to their different operating conditions. Normal overload can be used frequently, while the capacity of accident overload can only be used under accident conditions. Under special circumstances, if one of the transformers in operation fails and stops operation, or there is no standby transformer, the transformer in operation is allowed to be overloaded due to accident.
If the maximum load of the standard (average) load curve in summer (June, July and August) is lower than the rated capacity of the transformer, the allowable overload rate of the transformer in winter (November, December, January and February) is: 1% for each under load in summer and 1% for overload in winter, but the maximum shall not exceed 15%.
2、 Maintenance and purification of insulating oil
Oil extraction tests are often carried out on transformers, oil circuit breakers and other oil filled electrical equipment, which is of great significance to ensure the uninterrupted and accident free operation of electrical equipment.
The purpose of taking oil samples from the transformer for voltage withstand test is not only to determine the electrical insulation strength, but also to check many indicators.
One year after the transformer is put into operation, the first oil sample test under its normal operation state; After that, the oil sample test shall be conducted at least once every five years (for 8000kVA and above transformers, the color spectrum analysis of dissolved gas in oil shall be conducted once a year). When the sealing of the transformer is damaged or fails, the oil sample shall be taken out of the plan for electrical strength test. For transformers in operation, the electrical strength of oil shall not be less than 25 kV.
Simple identification method of insulating oil quality
1. The inspection method of oil color is to filter the insulating oil to be tested twice with filter paper (at 20 ℃ - 22 ℃), put the oil in the test tube, and compare the color with a group of test tubes with 15 standard oil colors. Although the oil color inspection can not directly determine whether the insulating oil can be used, it can quickly and easily identify the degree of oil quality change. For example, new oil is generally light yellow and becomes darker after oxidation. Dark new oil is not allowed. The oil color darkens rapidly during operation, which indicates that the oil quality has deteriorated.
2. For transparency inspection, put the new oil in a glass bottle with transparent color and blue purple fluorescence; Put the running oil into a glass bottle. If the fluorescence and transparency are lost, it indicates that there is a mechanical mixture and free carbon in the oil.
3. Smell, the new insulating oil generally has no smell, or carries the smell of kerosene. If there is another smell, the oil quality is bad. For example: burning smell - overheating when dry; Sour taste - serious aging of oil; Acetylene smell - over arc generated in the.
3、 Economic operation of transformer
For transformers that can allocate loads to each other and operate separately, the distribution of economic load shall be considered to minimize the total loss within a certain period of time (generally, the load of each transformer shall not be less than 50%). During the shutdown of two or more transformers, the power loss of all transformers shall be reduced properly.