Carbon Particles Detection in Transformer Oil Based on Lens-Free Holographic Technology

Transformer oil plays a pivotal role in the power system. Within this crucial part, carbon particles can originate from arcing or severe carbonization processes. The presence of these carbon particles poses a threat as it diminishes the insulation capabilities of the transformer oil, thereby making it necessary to observe the particles in the transformer oil in time to ensure the stable operation of transformer. To this end, a lens-free holographic microscope was hereby proposed to detect carbon particles. By holographic acquisition and reconstruction, the concentration and size of carbon particles could be obtained. For this experimental system device, the minimum to 5-
$\mu \text{m}$
carbon particles could be directly detected in transformer oil. This resolution is equivalent to a typical
$40\times $
objective lens. In the experiment, the prepared sample is placed on the sensor to record the hologram, and the area and volume of the particles are obtained by calculation, which allows the detection of a large number of particles in several minutes or less. Due to the high sensitivity of the method, the performance of transformer oil could be judged at the early stage of the accident, preventing further deterioration events from their occurrence. Overall, this method matters considerably in detecting particles in transformer oil because of its merits of large field of view, simple operation, convenient carrying, and low cost.