The DC resistance tester under UHV power can help many power workers conduct various power tests more conveniently.

Abnormal operation of power transformers can lead to serious safety accidents. Proper daily maintenance and upkeep can ensure the safe and smooth operation of transformers. Today we will share the daily maintenance techniques for transformers.

1、 Strengthen daily maintenance and regular inspections

According to the division of labor among management personnel in Taiwan, in addition to regularly carrying out transformer work, I also require management personnel to strengthen daily work and divide responsibilities. The key inspection contents include:

1. Observe the appearance. The main inspection is to check for oil leakage, smoking or emission of parts. Loose welding of the transformer casing or unstable rubber pads can lead to transformer leakage. If the oil level is too low, it will lose insulation protection, causing discharge between the conductive parts or between the conductive parts and the shell, and in severe cases, it will burn out the transformer. Therefore, faults should be eliminated and oil should be replenished in a timely manner to ensure that the oil level remains at 1/4 to 3/4 of the oil level. For loose components, poor contact, or even discharge, the transformer drop insurance should be promptly cut off to eliminate hidden dangers.

2. Check the moisture absorbing device. When the volume of transformer oil expands and contracts due to changes in load or ambient temperature, it forces the gas inside the oil storage tank to breathe through the moisture absorbing device to remove impurities and moisture from the air and maintain the insulation strength of the transformer oil inside the transformer.

3. Regularly inspect the casing. Sleeve is a component insulator composed of conductive tubes and sleeve type insulators. In the case of a transformer, it is used to electrically connect its internal windings to the power system or electrical equipment.

1) Check if the oil level in the casing is normal.

2) Check whether the surface of the casing is clean, free from cracks, damages, discharge points, and other phenomena.

3) Check if the connection between the sleeve terminal and the busbar is loose.

4) Check if the oil level of the oil paper capacitor bushing is normal.

5) Check if the oil paper capacitor cap is loose.

4. Listen to the sound. The normal operation of the transformer will produce a uniform and subtle buzzing sound, and the sound will change when the transformer experiences faults with different characteristics. At this point, measures should be taken based on the on-site situation to identify the cause of the malfunction.

5. Replace the oil and dust on the high and low voltage bushings, clean and wipe off the oil and dust in a timely manner, and discharge the dirt flash. When the climate is humid or rainy, prevent the bushing from short circuiting between phases, the high voltage fuse from melting, and the matching from not working. I require people to clean at least once every two months.

6. Observe the oil color, regularly check the oil temperature, especially in situations with large load changes, large temperature differences, and harsh weather, increase the frequency. The top oil temperature of oil immersed distribution transformers in operation should not exceed 95 ℃.

7. Shake and measure the insulation resistance of the transformer, check if the leads are secure, and pay special attention to whether the low-voltage outgoing connections are in good contact and whether the temperature is abnormal.

8. Strengthen power load measurement. During peak electricity consumption periods, strengthen the load measurement of each distribution transformer, increase the number of measurements if necessary, and adjust distribution transformers with unbalanced three-phase currents in a timely manner to prevent the neutral line current from burning the leads and causing damage to user equipment and distribution transformers. The wiring group is Yyn0, and the three-phase load should be balanced as much as possible. Not only should one or two phase power sources be used, but the neutral line current should not exceed 25% of the rated current on the low-voltage side, so that the distribution transformer does not overload or operate under unbalanced load.

9. Regularly check and replace one or two fuses. It is strictly prohibited to use aluminum wire instead of fuses. As is well known, primary fuse protection systems and secondary fuses protect transformers.

2、 Prevent external damage

1. Reasonably select the installation location of the distribution transformer, try to be close to the load center, and control the power supply radius within 0.5km. Meanwhile, try to avoid installing lightning strikes or low-lying water areas as much as possible. Due to its location in the county town, there are many transformers at the intersection. In order to reduce car collisions with iron towers, anti-collision signs are posted on the towers along the way.

2. Try to avoid installing low-voltage meter boxes on distribution transformers. Due to long operation time, the glass of the meter box is damaged or the low-voltage pile head of the transformer cannot be replaced in a timely manner. More than 95% of public distribution transformers are equipped with JP cabinets, which provide good protection for the safe operation of transformers.

3. Do not adjust the tap changer without authorization, in order to avoid improper adjustment of the tap changer, resulting in phase to phase short circuit and burning of the distribution transformer.

4. Install insulation covers at the high and low voltage ends of distribution transformers to prevent natural disasters and external damage. Install high and low voltage insulation covers in narrow residential areas and forest areas where animals frequently enter and exit to prevent objects from falling off the connection posts of distribution transformers and burning them.

5. Regularly cut off the circuit channels to prevent branch contacts from causing low voltage short circuits and burning distribution transformers.

3、 Precautions for use

1. Prevent transformer overload operation: Long term overload operation can cause coil heating, insulation aging, and short circuits between boxes, phases, or to ground. As a decomposition of oil;

2. Preventing aging and damage of transformer core insulation: Aging of core insulation or damage to clamping bolt sleeves can cause large eddy currents in the core, and long-term heating of the core can cause insulation aging;

3. To prevent damage to insulation during maintenance: compensation should be provided for repairing the iron core of the transformer.

Pay attention to protecting the coil or insulation sleeve, and promptly deal with any scratches found.

4. The minimum unbalanced current of the transformer's low voltage shall not exceed 25% of the rated value; The voltage variation of transformer power supply is allowed to be plus or minus 5% of the rated voltage.

5. Ensure good contact of wires: poor contact at the internal joints of the coil, poor contact at the connection points between coils, poor contact at the high and low voltage sides of the sleeve contact points, and poor contact at the fulcrum of the tap can cause local overheating, insulation damage, short circuits, or open circuits. The high-temperature arc generated at this time will cause the insulation oil to decompose, producing a large amount of gas and increasing the pressure inside the transformer. When the pressure exceeds the protection value of the gas circuit breaker and does not trip, an explosion will occur.

6. Maintain good grounding: For the use of protective zero low voltage systems, the neutral point on the low voltage side of the transformer should be directly grounded. When this current is too high and the contact resistance is high, the junction will experience high temperatures, igniting surrounding combustibles.

7. Prevent overheating: The transformer should be monitored when the working temperature changes. If the transformer coil wire is of Class A insulation, its insulation is mainly paper and cotton yarn, and temperature has a great impact on insulation and service life. For every 8 ℃ increase in temperature, the insulation life will be reduced by about 50%. Transformers operate at room temperature (90 ℃) and have a service life of approximately 20 years. If the temperature rises to 105 ℃, the lifespan is 7 years. If the temperature rises to 120 ℃, the lifespan is only two years. Therefore, transformers must maintain good ventilation and cooling during operation. If necessary, forced ventilation can be used to reduce the temperature rise of the transformer.