Views:17 Author:Site Editor Publish Time: 2015-01-16 Origin:Site
Insulating fluids, known for its dielectric features and chemical stability, are commonly used in power and distribution transformers. The main function is to insulate, prevent electric arc taking place and dissipate the heat generated during the transformer’s working. However, the oil in service will gradually deteriorate, and in turn raise the possibility of equipment malfunctions. The preventative measure is to perform a regular maintenance.
The two main role of transformer oil is cooling agent and insulator. Oxidization and contamination are the two problems to degrade oil during operation.
When the oil is exposed to oxygen, acid will form and build up. The acid accumulation will then become sludge, and adheres to the surface of transformer windings. Envelop by this oil sludge, dispersing heat will become a more difficult task, and as a vicious spiral, the windings will get hotter and cause even more sludge. The high temperatures and acid level speed up the insulation property degradation of the oil, and if the situation left unattended, will cause the electrical equipment to break down.
If the transformer seal is leaking, water and particulate will find their way into transformer oil, and the presence of the moisture and solid contaminants will lower the oil’s dielectric strength. So, the cleaner, the better.
Oil-immersed Transformer Maintenance begins with oil testing, and it’s a systematic task. Initial testing is introduced to set a base line, followed and compared with the results of yearly testing to tell when and what treatment is needed.
The following six factors are commonly covered by annual transformer oil analysis:
Dielectric Strength: This is to see to what degree voltage the insulating oil can withstand before breaking down. The higher the value, the better the oil’s insulation property.
Acid Number: This indicates the oxidization problem and sludge level of the oil. Neutralization need to be later introduced should the value is high.
Interfacial Tension: This discovers the existence of polar compounds, which will show the worsening of transformer materials, such as winding, paper, paint, etc.
Color: Clear transparency is preferable, while cloudy and dark color shows the oil is experiencing aging and presence of moisture.
Water content: Measured by PPM, since water conduct electricity much better than oil, a tiny amount mix in transformer oil will cause drastic fall of breakdown voltage.
Dissolved Gas: The presence of gases indicates possible arcing and overheat problems.
These tests should be taken regularly so as to monitor the transformer condition and ensure safe operation. Normally, certain parameters are recommended based on the kilovolt-ampere and voltage class of the transformer. Test results outside the predetermined values should be taken seriously, and remedial action need to be performed if the oil condition requires.