The first thing to know is the working life of three-phase dry-type transformer. It can be used correctly to maximize its economic value. The service life of three-phase dry-type transformer is 20 years. It is a common phenomenon that the temperature rise of dry-type transformer is above 120 °C for a long time under 100% full load operation. When the ambient temperature (summer) is above 35 °C, the temperature rise of dry-type transformer will reach above 125 °C. This will accelerate the aging of dry-type transformer insulation. This will shorten the service life of dry-type transformers. Dry-type transformer has two characteristics: 1. Keep out moisture. 2. Maximum temperature rise should not exceed 140 °C. In addition, it is important that the capacity of dry transformers should not exceed 1.3 times. The dry-type transformer runs at 100% full load for a long time, so long as it is not loaded, does not appear the big short-circuit current temperature rise, maintains below 120 °C, conforms to the biggest economic benefit. The problem is how to control the temperature rise of dry-type transformer? 1. Strengthen the control of dry-type transformer air-cooled Motor, improve the reduction of ambient temperature. Second, there should be no significant change in the load adjustment. In this way, the long-term operation within the scope of the Factor of safety can generally enable dry-type transformers to complete the normal service life. Explain the moisture problem. In general, many dry-type transformers are installed in underground buildings. Especially now the high-rise building multi-dry-type transformer is also in the second floor, the third floor underground. That's the trend in the underground environment. The indoor environment temperature is 20 °C and the relative humidity is not more than 80% . Dry-type transformers must be out of service for one week before they can be put into operation after the insulation tests are completed. On the question of temperature rise. The temperature rise must be kept at 120 °C or below 5 °C and generally can not be changed rapidly. Because the temperature rise is related to the load temperature rise is related to the aging of insulation. The life of a transformer is temperature. Each increase of 6 °c reduces the lifetime and is also related to the operation time. In my work experience, I have experienced the premature replacement of dry-type transformers due to the usual high temperature rise of transformers due to the aging of insulation. The replaced dry-type transformer has actually operated for about 18 years.
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