The content of furfural dissolved in insulating oil is one of the key indicators to evaluate the aging state of oil-immersed power equipment. Surface-enhanced Raman spectroscopy (SERS) technology enables the direct detection of furfural in insulating oils

but the detection time is up to 360 min and limited to mineral insulating oils. Therefore

this study investigates the rapid detection of furfural in different insulating oils by Raman spectroscopy and factors affecting detection limit variability. Firstly

a 4-ATP-CNTs@NiO-Fe2 O3-Ag filter substrate with a pore size of 220 nm and an angled sample injector is developed for the enrichment and filtration of furfural

enabling rapid detection of furfural in mineral insulating oil

with the equilibrium detection time of only 120 seconds. Then

different types of insulation oils (PAFE palm oil

25# Karamay mineral insulation oil

RAPO rapeseed-based natural ester

FR3 soy-based natural ester

PCIE pentaerythritol ester) are studied for the detection of furfural SERS

revealing differences in the limit of detection (LOD) ranging from low to high as follows: 0.005 mg/L (palm oil)<0.01 mg/L (rapeseed oil)<0.025 mg/L (mineral oil)<0.05 mg/L (soybean oil)<0.1 mg/L (pentaerythritol ester). Finally

it has been confirmed that the viscosity of insulating oil is the main parameter affecting the dissolution of furfural LOD in the oil and its underlying reasons. The higher the viscosity

the stronger the binding ability of furfural with various insulating oils

making it more difficult for furfural to adsorb on the surface of the SERS filter membrane due to molecular thermal motion

and resulting in a higher LOD. This study is of great significance for the rapid and highly sensitive detection of furfural in different types of insulating oils using SERS

ensuring the safe and stable operation of various oil-immersed transformers.