Cleaning, oil sample injection, and resistivity testing method for the oil cup of the insulating oil volume resistivity tester:
(I) Cleaning of the oil cup of the insulating oil volume resistivity tester.
①. Loosen the nut to separate the inner electrode and the insulating plate (if necessary, the shielding ring can be removed and cleaned together).
②. Clean the inner and outer electrodes and the insulating plate with a cleaning agent (preferably boil them in a 5-10% trisodium phosphate aqueous solution for five minutes), then rinse thoroughly with tap water, and finally rinse twice with distilled water. Then dry in an oven at 105±1°C. The dried oil cup can be placed in a desiccator to cool for later use.
③. For continuous testing, if it is estimated that the next measurement value will be lower than the current result, the oil cup can be directly rinsed twice with the test oil, and then the measurement can be performed.
3. Inject the oil sample into the oil cup.
Inject the test oil into the cleaned and dried oil cup, place the inner electrode, gently stir with the inner electrode, then remove the inner electrode and pour out the test oil from the oil cup. Re-inject the test oil up to the standard line. Place the inner electrode and wipe off the residual oil around the oil cup. Place the oil cup into the thermostat for heating and maintaining constant temperature.
(II) Measurement of resistivity using the insulating oil volume resistivity tester
1. Insert the test head into the electrode under test;
2. During measurement, the range multiplier is generally selected as 10^12 Ω·cm, but the criterion is not to overflow. Press the function switch to "Test". Observe the test screen. If the screen displays "1", it indicates under-range (overflow). Turn the range switch clockwise to increase the multiplier. If the screen displays "0.10", it indicates over-range. Turn the range switch counterclockwise to decrease the multiplier. The range should be selected with a low multiplier but without overflow.
3. When the range multiplier is selected as 10^14 Ω·cm or above, press the heating switch; otherwise, restore it to its original position.
4. When the 60-second timer ends and a long "beep..." signal sounds, it indicates the test is complete, and the reading is automatically locked. Record the resistivity ρ value of the insulating oil. Immediately restore the function switch to the "Discharge" position.
5. After discharging for 5 minutes, unplug the measuring head and reinsert it into the inner electrode of another oil cup to test the next oil sample. Remember not to unplug the measuring head during the measurement process.
