Transformer partial discharge generation and prevention - Database & Sql Blog Articles
Partial discharge is a common phenomenon in high-voltage electrical equipment such as transformers, where the internal insulation experiences localized discharges under the influence of high voltage. Unlike full breakdown or flashover, partial discharge occurs only in specific areas of the insulation and does not immediately cause complete failure. This makes it difficult to detect with the naked eye, as the discharge is very weak and requires highly sensitive instruments to identify.
During normal operation, the internal insulation of a transformer is constantly subjected to working voltages. As the voltage level increases, the electric field strength within the insulation becomes more intense, making it more prone to partial discharge at weak points. Common causes include concentrated electric fields at certain points, such as air bubbles in solid insulation, impurities remaining in the material, moisture or gas in the oil, or irregularities at the interface between different dielectric materials. These conditions can lead to localized stress, triggering partial discharge.
The effects of partial discharge may appear as small burn marks on solid insulation or dendritic patterns in the oil. Though the discharge itself is brief and energy is low, its long-term impact can be significant. The discharge generates active gases like ozone and nitrogen oxides, which chemically degrade the insulation, increasing its conductivity and leading to thermal breakdown over time. Most cases of internal insulation aging in transformers are attributed to this type of discharge.
There are several methods used to detect partial discharge in transformers:
- Electrical Measurement Method: This involves using an oscilloscope or radio jammer to detect the characteristic waveforms or interference levels caused by the discharge.
- Ultrasonic Measurement: Sound waves produced during the discharge are captured and converted into electrical signals. By analyzing the time difference between the electrical and acoustic signals, the distance to the discharge location can be determined.
- Chemical Analysis: This method focuses on detecting changes in the composition of dissolved gases in the transformer oil. It helps identify whether partial discharge or localized overheating has occurred based on gas content and ratios.
In recent years, online partial discharge detectors have been developed to continuously monitor and automatically detect discharges while the transformer is in operation, improving early warning capabilities.
To prevent partial discharge, manufacturers should focus on proper design, use high-quality materials, and ensure strict quality control throughout the production process. Operators, on the other hand, must perform regular maintenance and monitoring to minimize the risk of partial discharge and ensure the safe and reliable operation of transformers.
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