6 points for maintenance of dry-type transformers

Writer： Hengfeng you electric Time：2023-03-31 views：times

Epoxy cast dry-type transformers have many advantages such as flame retardant, self-extinguishing, moisture resistance, high mechanical strength, small size, light weight, and strong short circuit resistance, and are widely used. However, dry-type transformers also have some disadvantages, such as their heat dissipation performance is not as good as that of oil-immersed transformers under poor ventilation. Below is a summary from the electrical engineer EVAN of Hengfengyou Electric, who has been dedicated to designing and manufacturing Dry-type Transformer, Oil-immersed Transformer, Single-phase Transformer, Amorphous Alloy Transformer, Special Transformer for many years, Some experiences on operation and maintenance of dry-type transformer are summarized for reference.
 
1. Regular cleaning
 
If excessive dust accumulation is found, it must be removed immediately to ensure air circulation. In places with large dust deposits, dry-type transformers should be cleaned at least once every six months. For dust in the ventilation duct. Use a vacuum cleaner or compressed air to remove. If it is not removed in a timely manner, it will affect the heat dissipation of the transformer, and will also lead to reduced insulation of the transformer or even insulation breakdown. For example, our company's 220kV Weizhuang substation and 35kV station transformer were subjected to a power outage test. Using a 2500V photoohmmeter to measure the insulation resistance of the iron core of the Yu-type transformer, the insulation resistance of the iron core decreased to 3M2, which is much lower than the previous test data of 100M. The main reason is that the dust in the ventilation duct of the transformer was not cleaned up, and the insulation resistance of the iron core increased to 100M after cleaning.
 
 
2. Strengthen the operation and maintenance of ventilation equipment, ensure smooth ventilation of transformers, and ensure the normal operation of ventilation equipment, mainly to ensure the normal operation of fans. "If the load is small and it is proven that the transformer does not have a particularly hot spot (which can be detected by an infrared thermometer and its own temperature controller), it is possible to reduce the number of fans in operation, but it is necessary to ensure the normal operation of the fans. Once thermal damage occurs to a dry-type transformer, it will seriously damage the internal windings, with unimaginable consequences. Generally, it emits 1 kw of heat loss,", The required ventilation rate of 4 m3/min should be installed around transformers without enclosures. The doors and ventilation holes of the transformer room should be equipped with measures to prevent rain, snow, birds, snakes, and other small animals from entering.
 
 
 
3. Strengthen temperature monitoring
 
Generally, it is necessary to strengthen the observation of the temperature controller to see whether the displayed three-phase temperature is balanced, and whether there is a sudden change in the temperature display value of a certain phase. At present, the connector between the temperature controller and the internal thermistor (temperature measurement) of the transformer uses a pin type plug, which can lead to misjudgment of the temperature controller once the contact is poor. However, if monitoring is strengthened, abnormal working conditions of the temperature controller can be found, and measures should be taken in advance to avoid failures. For large capacity transformers and transformers in important locations, when ordering, the jade transformer manufacturer can be required to install an additional thermistor per phase to achieve dual configuration of temperature controllers, which can effectively prevent such failures.
 
 
 
4. Actively carry out dehumidification work to ensure its dryness
 
In some humid places (such as rainy and dark places), if a dry-type transformer that has been shut down is started, it is necessary to check whether there is abnormal humidity. If any, start hot air to dry the surface to prevent insulation breakdown. For oxygen cast dry-type transformers, this surface wetness does not affect the insulation inside the windings, so they can be put into operation after treatment. Once the transformer is put into operation, the heat generated by its loss will restore the insulation resistance to normal.
 
 
 
5. Carefully check whether fasteners and connectors are loose to ensure the mechanical strength of dry type transformers
 
During long-term operation of transformers, due to external knowledge of the path and other reasons, it is inevitable that fasteners and connections will become loose due to stress and vibration at the ends. If the above phenomenon occurs, it is possible to generate a hot spot. For this reason, temperature indicating wax sheets should be installed at high and low pressure terminals and all places where overheating may occur, and regular observation should be conducted. In combination with cleaning and preventive testing, the terminals and connectors should be tightened.
 
6. Actively carry out rust removal work to prevent iron core rust
 
The iron cores of dry-type transformers are exposed to air and are prone to corrosion. If large areas of iron core corrosion occur, it will increase transformer losses, reduce efficiency, and even directly affect the life of the transformer. Therefore, it is necessary to regularly remove rust and prevent rust on the iron core. In addition, the withstand voltage level of dry-type transformers currently produced is lower than that of oil-immersed transformers, so it is necessary to strengthen the configuration and maintenance testing of lightning arresters. Zinc oxide lightning arrester is preferred for lightning arrester. The high-voltage side should be led in by cables and should not be directly connected to overhead lines.
 
 
 
If you have more questions about the photovoltaic double split step-up transformer, please visit www.hengfengyou.com to consult our sales manager at Hengfengyou Electric.