As a core equipment in the power transmission and distribution system, transformers play a vital role in ensuring stable power supply. However, transformer burnout accidents occur from time to time due to various factors, which not only cause economic losses but also affect the normal operation of production and life. This article will detail the common causes of transformer burnout and corresponding solutions, focusing on the application and protection of 315kva dry type transformer and dry type step down transformer, to provide practical reference for relevant practitioners and users.
I. Common Causes of Transformer Burnout
Transformer burnout is usually caused by improper operation, poor maintenance, equipment quality problems or external environmental factors. The following are the most common causes, which also apply to 315kva dry type transformer and dry type step down transformer.
1. Lack or improper configuration of fuses
There is no fuse on the high and low voltage sides of some distribution transformers. Even if drop-out fuses and horn fuses are installed, the fuses are often replaced with aluminum or copper wires. When low-voltage short circuit or overload occurs, the fuses cannot blow normally, resulting in transformer burnout. In addition, the fuses on the high and low voltage sides of the transformer are generally configured too large. When the transformer is seriously overloaded, the fuses cannot play a protective role, leading to burnout. This problem is particularly prominent in some old 315kva dry type transformer and dry type step down transformer that have been in operation for a long time.
2. Unbalanced three-phase load operation
In rural areas or some industrial sites, there are many lighting lines, most of which adopt single-phase power supply. In addition, the randomness of jumper wires during construction and inadequate management lead to unbalanced load operation of the transformer. Long-term unbalanced operation will cause the insulation of a certain phase coil to age and damage, and even burn out the transformer. For dry type step down transformer used in commercial buildings and small industrial workshops, unbalanced load is also one of the main causes of burnout.
3. Problems with tap changers
The tap changer is an important component of the transformer to adjust the output voltage. There are two main problems that lead to transformer burnout: first, unauthorized adjustment of the tap changer by non-professional personnel leads to poor contact of the tap changer, local overheating and burnout; second, the poor quality of the tap changer itself causes incomplete contact of the star contact, resulting in short circuit or ground discharge, which further burns out the transformer. This is also a common fault point in 315kva dry type transformer.
4. Oil leakage and insulation dampness (for oil-immersed transformers)
Oil leakage is the most common external abnormal phenomenon of oil-immersed transformers. The transformer body is filled with oil, and all connection parts are equipped with rubber beads and gaskets to prevent oil leakage. After long-term operation, some rubber beads and gaskets in the transformer will age and crack, causing oil leakage. Oil leakage will lead to reduced insulation performance after damp, discharge short circuit, and finally burn out the transformer. For dry-type transformers such as 315kva dry type transformer, although there is no oil leakage problem, damp environment will also lead to insulation degradation and burnout.
5. Lightning strike damage
Most of the high and low voltage lines of distribution transformers are introduced by overhead lines. If the arrester is not put into operation in time or no 10kV arrester is installed, the transformer will be burned out when struck by lightning. Especially in areas with frequent thunderstorms, the risk of lightning strike damage to transformers is higher, including 315kva dry type transformer and dry type step down transformer used in outdoor environments.
6. Other common causes
In addition to the above reasons, core multi-point grounding, short circuit at the low-voltage side, and man-made damage can also cause transformer burnout. For example, when a ground or phase-to-phase short circuit occurs on the low-voltage side of the transformer, a short-circuit current 20-30 times higher than the rated current will be generated, which will produce great mechanical stress and high temperature, burning out the transformer in a very short time; man-made damage such as electrochemical corrosion between copper and aluminum wires and bushing flashover discharge are also important factors leading to transformer burnout.
II. Countermeasures to Prevent Transformer Burnout
Aiming at the above causes of transformer burnout, we can take targeted measures to effectively reduce the occurrence of burnout accidents, especially for 315kva dry type transformer and dry type step down transformer, which need more targeted protection according to their use environment and characteristics.
1. Install and configure fuses correctly
When building a new power distribution system, high and low voltage fuses should be installed in time. During the operation of the transformer, if the fuse is burned out or stolen, it should be replaced in time. At the same time, the fuses should be reasonably configured: for transformers with a capacity of more than 100kVA (such as 315kva dry type transformer), fuses with 1.5-2.0 times the rated current should be configured; for transformers with a capacity of less than 100kVA, fuses with 2.0-3.0 times the rated current should be configured; the fuses on the low-voltage side should be selected to be slightly larger than the rated current to ensure that the fuses can blow normally when a fault occurs and play a protective role.
2. Avoid unbalanced three-phase load operation
Strengthen the actual measurement of power load. Before the peak load period, use a clamp ammeter to measure the load of each transformer, adjust the load reasonably, and avoid unbalanced three-phase operation of the transformer. For dry type step down transformer used in places with complex loads, regular load detection should be carried out, and load adjustment measures should be taken in time if the three-phase load current is seriously unbalanced to prevent insulation aging caused by partial overload.
3. Standardize the operation and maintenance of tap changers
Generally, it is not allowed to adjust the tap changer when the low-voltage side voltage of the 10kV transformer is within the range of 7% ~ - 10%. When adjusting the tap changer, it must be tested and adjusted by maintenance and test technicians to avoid poor contact caused by improper adjustment. For 315kva dry type transformer that needs frequent voltage adjustment, the tap changer should be inspected regularly to ensure its good contact and stable operation.
4. Strengthen insulation protection and anti-lightning measures
For oil-immersed transformers, regularly check for oil leakage, replace aging rubber beads and gaskets in time, and ensure good insulation performance; for dry-type transformers such as 315kva dry type transformer, avoid installing them in humid environments, and take moisture-proof measures if necessary. Before the arrival of the thunderstorm season every year, all arresters on the distribution transformer should be sent to the maintenance and test department for inspection, and installed in time after passing the test to prevent lightning strike damage.
5. Do a good job in pre-commissioning inspection and regular maintenance
Before the transformer is put into operation, the following detection work should be done well: first, switch on and off with load three times without misoperation; second, test with the test button three times, which should act correctly; third, test with test resistance grounding three times, which should act correctly. At the same time, regularly clean the dirt on the surface of the transformer bushing, check whether there are flashover marks on the bushing, whether the grounding is good, and whether the lead wires used for grounding have broken strands, desoldering or fracture; use a megohmmeter to detect that the grounding resistance shall not be greater than 4Ω. For 315kva dry type transformer and dry type step down transformer, regular maintenance should also include cleaning the coil surface and checking the cooling system to ensure stable operation.
6. Prevent man-made damage
Avoid using aluminum-copper wire direct connection at the transformer lead-out end to prevent electrochemical corrosion; strengthen the management of transformer operation, prohibit unauthorized operation and disassembly, and regularly inspect the transformer's external environment to avoid damage caused by external forces. JINSHANMEN TECHNOLOGY CO., LTD reminds users that standardized operation and regular maintenance are the key to reducing man-made damage to transformers.
III. Conclusion
The normal operation of transformers, including 315kva dry type transformer and dry type step down transformer, is closely related to standardized management, correct operation and regular maintenance. Most transformer burnout accidents are avoidable as long as we identify potential risks in time, take targeted preventive measures, and strictly follow the operation and maintenance specifications.
JINSHANMEN TECHNOLOGY CO., LTD has been committed to providing high-quality power transmission and distribution equipment and professional technical support. If you have any questions about the selection, use and maintenance of 315kva dry type transformer, dry type step down transformer and other transformers, we will provide you with professional solutions to help you ensure the safe and stable operation of power equipment.