According to oil flow cycling characteristics from bottom to up

three fiber Bragg grating（ FBG）temperature sensors

A

B

C are installed in fuel tank bracket is fixed in three locations which are used to measure oil temperature of top

middle and bottom layer of transformer. The grating center wavelength varies with temperature

by variation of FBG center wavelength can realize measurement of oil temperature change.Experimental results show that the highest oil temperature at top

middle and bottom of transformer are 73

66. 5

52. 2 ℃ respectively

open the blower in turn after 14

5

3 min began to cool

corresponding cooling time constant are 4 364

3 236

1 527 s

about after 25 min

temperature is stable at 64

52

45 ℃. The analysis shows that

in top

middle

bottom layers

oil temperature decreases after opening fan and cooling rate increased.