1. Collect oil samples
To collect oil samples for transformer oil test, it is necessary to collect oil samples in advance. Whether the oil samples are correct or not directly affects the authenticity and accuracy of the oil test. Therefore, the following requirements are put forward for the container for collecting oil samples, the method for collecting oil samples, and the storage and transportation of oil samples:
(1) The container for oil sample collection is a colorless glass bottle with a frosted glass stopper, or a 100ml all-glass syringe and a small-mouth bottle, and a light-shielding bottle is used for the measurement of the oil medium factor.
(2) Cleaning of the oil sample container. It mainly includes the following two aspects.
① The oil sample bottle should be cleaned with solvent before sampling to prevent the intrusion of dust and moisture. The solvent can be gasoline, trisodium phosphate, etc. After cleaning, wash with clean water and distilled water for several times, and dry in a 105 ℃ oven to clean and dry the oil sample bottle. After drying and cooling, plug the bottle tightly.
② After the oil sample is taken, a label should be attached, indicating the name, source, date, weather conditions, and sampler of the oil sample.
(3) The method of collecting oil samples. It mainly includes the following three aspects:
① For transformers in operation, samples should be taken from the lower oil drain valve. First clean the oil and dust on the outer surface of the oil drain valve, then release about 2ml of oil to flush the valve, and at the same time use the released oil to rinse the container for collecting oil samples twice, and finally take the sample officially; when sampling, the oil column of the oil flow should go down along the inner wall of the bottle to prevent air from being brought into the oil; gently shake the obtained oil sample to distribute the sundries in the oil evenly without forming air bubbles. Then rinse the oil cup with the oil sample (the oil cup itself should be clean) at least 2 times, and finally inject the oil sample along the cup wall to the point where the oil level is not less than 10mm above the electrode. If the oil test is not carried out on-site, the sampling bottle should be tightly stoppered, sealed with paraffin or varnish, and labeled.
② For small transformers without oil drain valves, when the transformer is powered off, clean it in advance and insert a dry glass tube into the bottom of the transformer to take oil samples. The method of taking the oil sample is to first press one end of the glass tube with the thumb, insert it into the bottom of the oil tank, release the thumb, press the oil into the glass tube by the oil pressure in the tank, and then press the end of the glass tube with the thumb to take out the oil sample.
③ When sampling with a glass syringe, because its core can move freely (as shown in Figure 1), it can compensate for the expansion and contraction of the oil sample with temperature changes, and it can also prevent the oil sample from contacting the air, especially for equipment with a small amount of oil.
(4) Storage and transportation of oil samples. It mainly includes the following two aspects.
① The test should be done as soon as possible after the oil sample is taken out, generally within 4 days. In the case of long-distance delivery, a syringe sample should be used for more than 4 days, as shown in Figure 1.
(a) Flush connections; (b) Wet and flush syringes; (c) Empty syringes; (d) Take oil samples; (e) Remove syringes
② The oil sample should avoid light and violent vibration during transportation.
2. Replace the silicone
(1) Replace the silicone for the oil purifier. When the transformer is running, when the acid value of the oil increases significantly, it should be considered to replace the new silica gel. Silica gel should be screened for particles with a particle size of 6~8mm. Whether the replacement of the silicone is carried out under a power failure depends on the situation. First, close the butterfly valves at the upper and lower ends of the oil purifier to ensure that the butterfly valves are completely closed, and then open the lower oil drain plug first, then open the upper air relief plug to drain the oil, and finally open the lower flange of the oil purifier to release the old silica gel, open the upper flange and pay attention to check whether the inlet and outlet baffles (non-metallic materials) of the oil purifier are in good condition. After cleaning with qualified transformer oil, close the lower flange, and pour new silica particles of 6~8mm particle size from the upper flange hole that have been screened and cleaned with qualified transformer oil (do not need to be too full). The total weight of the adsorbent is about 0.5%~1% of the total weight of the transformer oil, seal the flange (replace the rubber ring with a new one), and put it into use in the transformer after inspection. For the oil purifier on the cooler, the butterfly valve at both ends of the inlet and outlet can be closed, and the new silicone can be replaced after removing it. The rest of the steps are the same as the above. A large number of old silica gels that have been replaced can be restored and reused after being burned in a burning furnace.
(2) The moisture absorber replaces the silica gel. It mainly includes the following aspects.
① Remove the moisture absorber from the transformer, pour out the internal adsorbent, check that the glass cover is in good condition, and clean it.
② Put the dry adsorbent into the moisture absorber. In order to monitor the working performance of the adsorbent, color-changing silica gel can generally be used, and a gap of 1/6-1/5 height is left under the top cover. The newly installed adsorbent should be dried and the particle size should not be less than 3mm.
③ The expired adsorbent changes from blue to pink, and can be placed in an oven for drying, and the drying temperature is raised from 120℃ to 160℃. The time is 5h, and it is blue after reduction and reused.
④ Replace the rubber pad, and the quality of the rubber pad must meet the standard requirements.
⑤ Inject transformer oil into the lower oil seal cover, add oil to the normal oil level line, so as to have a breathing effect, and finally tighten the cover (the gasket should be removed when the moisture absorber is newly installed).