Common faults of power transformers: winding faults and bushing faults

Writer： Hengfeng you electric Time：2023-04-18 views：times

Power transformer is a static power equipment that changes the magnitude of AC voltage, and is one of the core equipment in the power system. In the process of energy transmission and distribution, power transformer is the core of energy conversion and transmission, and is a necessary path for various industries and households in the national economy to source energy.
 
If a transformer malfunctions, it will affect the safe and stable operation of important equipment in the power system. Once an accident occurs, it will cause significant economic losses. Hengfengyou Electrical Engineer analyzes various power transformer accidents, identifies the causes, summarizes methods for handling accidents, and minimizes accident losses to minimize damage to the system.
 
01 winding fault
 
There are mainly inter turn short circuits, winding grounding, phase to phase short circuits, wire breaks, and joint welding. The reasons for these faults are as follows:
 
① During manufacturing or maintenance, local insulation is damaged, leaving defects;
 
② Due to poor heat dissipation or long-term overload during operation, debris may fall into the winding, resulting in excessive temperature and insulation aging;
③ Poor manufacturing process, insufficient compression, mechanical strength unable to withstand short circuit impact, resulting in winding deformation and insulation damage;
 
④ Damping of the winding, insulation expansion, blockage of the oil duct, causing local overheating
 
⑤ The insulation oil deteriorates due to the mixing of water, or the contact area with the air is too large, resulting in a high acid value of the oil, a decrease in insulation level, or a low oil level. Some windings are exposed to the air and cannot be treated in a timely manner.
 
Due to various reasons mentioned above, insulation breakdown during operation can cause short circuits or grounding faults in the windings. The fault phenomenon during inter turn short circuit causes the overheating oil temperature of the transformer to increase, the power side current to slightly increase, the DC resistance of each phase is unbalanced, and sometimes there is a squeaking and bubbling sound in the oil. A slight inter turn short circuit can cause gas protection action; In severe cases, differential protection or overcurrent protection on the power side will also operate. Discovering inter turn short circuits should be dealt with promptly, as inter turn short circuits in windings often cause more serious faults such as single-phase grounding or inter phase short circuits.
 
02 casing failure
 
This type of malfunction is commonly caused by explosion, flashover, and oil leakage, which can be caused by:
 
① Poor sealing, poor insulation due to moisture, or oil leakage;
 
② Improper configuration of respirators or failure to handle inhalation of moisture in a timely manner;
 
③ Capacitor bushings are generally used on the high-voltage side of transformers (110kV and above), which may have sand holes or cracks due to poor porcelain quality;
 
④ There are defects in the manufacturing of the capacitor core and internal free discharge;
⑤ Severe scaling of the casing.
 
Hengfengyou is a professional electrical company specializing in the production, manufacturing and sales of electrical distribution products, mainly engaged in the production and global sales of distribution transformers, rectifier transformers, electric furnace transformers, etc. We have provided OEM / ODM services for customers in Europe, America and the Middle East for 20 years. It can provide customized production of transformer core, transformer coil and transformer shell. Hengfengyou Electric will provide you with the best electrical product solutions. https://www.hengfengyou.com  ； info@hengfengyou.com   WhatsApp：+86158 5325 2696（Jack）    +86158 5326 5269（Alisa）