Normal operation of electrical devices depends on regular maintenance. Transformer maintenance is a prerequisite for its reliable operation.
How often is it necessary to perform transformer maintenance? It is not easy to give a clear answer to this question, since it depends on the technical condition of the equipment and not two units are the same. The standards set a maximum interval of four years.
Stages of transformer maintenance
Transformer maintenance usually begins with an external examination. If any defects are found, they should be eliminated. After a visual inspection, a number of preliminary procedures are performed, including: checking the reliability of connections, cleaning insulator radiators and tank, removing dirt from expander, refilling oil, taking oil samples.
It is very important to perform a transformer leak test. A leak can happen because of unsealed tank lid and can be eliminated by tightening the bolts. Otherwise, the seals are replaced. The seal material is generally made out of oil resistant rubber.
The tank and radiators are cleaned from dust and oil. Insulators are cleaned with gasoline. When refilling, it is important to keep a new oil temperature close to the oil in transformer within 5 ºC. The oil temperature is controlled by a special thermometer, which is located on tank lid.
Attention is also paid to silica gel in the air dryer. If silica gel has a pink color, it is replaced, to guarantee a reliable operation of an air dryer. The used silica gel is regenerated through drying at a temperature of 100-120 ºС for 15-20 hours or at 400-500 ºС for 2 hours. The recovery is final when the adsorbent obtains a bright blue color.
A thermosyphon filter is cleaned depending on the acid number of oil. The acid number is determined by the oil tests. If the acid number exceeds 0.1 mg KOH / g, it is necessary to perform the following tasks:
- Drain the oil from an expander.
- Remove a filter cover.
- Remove a sorbent container.
- Remove used silica gel and replace it with fresh (dry).
Maintenance of air transformers
The maintenance of a dry transformer has some differences. After removing the tank cover, determine that there are no mechanical damages to the windings and other important parts. Also check the reliability of connections and grounding. It is advisable to dry a transformer with hot air, and also to wipe the insulators.
After maintenance procedures it is mandatory to measure the winding insulation resistance.
Maintenance of measuring transformers
Measuring transformers are used to measure currents flowing in the circuit. Also, such transformers monitor the presence of the phase of an electrical signal. And they operate in specific and set Voltage.
The maintenance of a measuring transformer begins with cleaning it from dirt and dust, inspecting the insulation; checking the oil level in the tank and testing for leaks in the welded seams and seals. The oil leaks are removed by tightening the fastening bolts. If there is no result, a new gasket of oil resistant rubber is installed.
GlobeCore equipment for transformer maintenance
GlobeCore produces a wide range of equipment that significantly improve transformer maintenance
The available equipment:
- transformer oil regeneration;
- transformer oil refilling units;
- transformers vacuum treatment and drying of solid insulation;
- oil heating units;
- hot air drying unit.
Equipment needed for Transformer maintenance
Oil filled, dry or measuring transformers need proper maintenance, to eliminate the influence of mechanical, thermal and electrodynamic forces on the equipment. Transformer maintenance detects the development of various defects and prevents emergency shut-downs.
Depending on the work performed, there are routine and capital maintenance of transformers. Routine maintenance and repairs does not present great difficulties. It checks the individual nodes that can deteriorate rapidly. Capital maintenance of a transformer includes the tests of all parameters as well as thorough inspection and repair of all parts.
It is difficult to determine a frequency of maintenance, since no two transformers of the same power are in the same condition. It is due to the changes in operating loads. Therefore, the standards set the maximum time for maintenance: routine transformer maintenance should be carried out at least every four years, and capital maintenance every eight years after commissioning and more often if necessary.
What equipment to choose for transformer maintenance?
Some of the maintenance can be performed manually using simple instruments. For example, you can take oil samples, clean insulators and a tank; tighten the nuts to restore the tightness of seals between the tank and the lid. But it is impossible to refill transformer oil without special equipment. Before refilling, the oil must be prepared (degassed, cleaned from impurities) and stored until it is installed in a transformer.
GlobeCore produces equipment that significantly simplifies the operastion of businesses specializing in repair and maintenance of electrical equipment.
GlobeCore recommends the following models:
- UVD – easy to operate mobile plant for refilling degassed oil in a transformer;
- INEY – a unit for vacuum treatment of power transformers and drying of solid insulation;
- PPM – transformer oil heating unit. It is used before refilling or changing the oil;
- “Mojave heat” –a hot air drying unit for drying a transformer tank with dry hot air. It protects the insulation from moisture entering the active parts of transformer during depressurization, repair or maintenance;
- CMM – degasses and cleans power transformers and transformer oil from mechanical impurities through a combination of treatment methods (temperature and vacuum, adsorbents, filtration) and always achieves the best results;
- СММ-R – restores important operational parameters of electrical insulating oil. The equipment can be connected directly to an energized transformer;
- TSS – transformer safety system that connects an oil-processing plant to a transformer. It also monitors the oil level in a tank, tests for leaks and air in the connecting hoses.
GlobeCore regularly expands the functionality of its equipment. The units for transformer maintenance can be equipped with additional sensors, as well as a monitoring and control system via mobile device.