Bushing failures contribute significantly to the failure statistics of power transformers. On average, one out of four transformer failures are due to issues with the bushings. Not only are failures likely to occur but 50% of bushing failures end in fires. Bushing failure can occur for several reasons such as reduction in dielectric strength, thermal integrity or mechanical strength.
What is Online Bushing Monitoring?
Offline tests are performed on a routine schedule – maybe once every few years. Yet many failure mechanisms on bushings can occur in a very short period of time measured in days to weeks. Additionally, some failures are temperature and voltage dependent that are difficult to simulate during offline tests.
Online bushing monitoring overcomes these offline test limitations to increase the performance and reliability of the transformer.
Online monitoring of bushings provides data during all weather conditions, loads, and at rated voltage, with the same sensitivity as an offline measurement. Learn more about online bushing monitoring methods and case studies in this white paper.
50% of bushing failures end in fires!
On Average 25% of transformer failures are bushing related
On Average 1 Out Of Every 200 Transformers Experiences A Major Failure Each Year.
How Do Offline Bushing Tests Compare to Online Monitoring?
Why the Data May Not Match
Offline bushing tests and online monitoring are both important to evaluate the health of your bushings. However, there are times when the data from offline tests and online monitors may not match. This can be due to several reasons. Typically, offline testing is performed at near ambient temperature with a test voltage of 10kV. Online systems meanwhile, are measuring the performance of the bushing at full operating voltage and temperature. Since the “test” parameters are different, the results may be different.
To learn more about why the data may not match, check out our webcast presentation on Online Monitoring vs Offline Testing.