Oil filling in high-voltage transformer bushings

Transformer oil filling is a process operation that takes place during transformer maintenance. If necessary, oil is topped up either directly into the transformer tank or into the high-voltage bushings.

Features of high-voltage transformer bushings maintenance

The reliability and safety of power generation, transmission, and distribution to a final consumer depends on operation of high-voltage equipment. In order to transmit high voltage over long distances, high-voltage conductors are used and connected to the power transformer winding, while bushings are used to connect these conductors. They constitute an important connecting element between the power transmission line and the transformer substation. The reliability of power supply to consumers depends on the steady operation of bushings. Due to this, the materials used therein shall have a high mechanical and dielectric strength which is often ensured by insulating oils capable of withstanding high voltages without overheating.

A vacuum drying and degassing technology is normally used in installation and maintenance of high-voltage bushings, which makes it possible to avoid an electrical breakdown and ensures a low level of residual moisture for short circuiting prevention. However, during operation, the volume of oil in a high-voltage bushing may decrease, for example, due to periodic sampling of oil for analysis, or a sealing failure. In this case, oil filling is required to regain the oil level so that a high-voltage transformer bushing functions properly.

Transformer oil filling machine UVD

GlobeCore has developed a technology for oil preparation by oil degassing and filling in high-voltage transformer bushings which is implemented in the UVD machine.

The UVD oil filling machine consists of three main components:

• a vacuum pump;
• an oil preparation unit;
• an oil filling unit.

The insulating oil is filled in a 30-liter preparation unit through a filler neck. Next, the vacuum pump starts running, and the oil is degassed for four hours. Then the vacuum pump stops running, and a portion of oil with a volume of four liters is fed from the preparation unit into the filling unit due to rotation of a piston crank. After the filling unit has been filled with oil, it is connected to the high-voltage transformer bushing by means of a special tube, and the required volume of oil is forced out of the filling unit into the high-voltage bushing due to reverse rotation of a piston crank.

As you can see, oil filling in high-voltage bushings based on GlobeCore technology is quite easy. The UVD machines are designed to be practicable and as user-friendly as possible. Wheeled mounting allows the machine to be easily moved between transformers, which greatly facilitates the maintenance process. Owing to compact dimensions (length — 0.9 m, width — 0.78 m, and height — 1.5 m), the equipment can be used in a limited space. If necessary, the oil filling unit may be detached from the skid and separately moved to the transformer.

Thus, the timely use of GlobeСore technology for oil filling in high-voltage transformer bushings allows enhancing the power supply reliability and reducing the financial costs associated with power outages due to failures of high-voltage bushings and transformer downtimes.

Transformer oil filling machine UDM

GlobeCore product line also includes oil filling equipment not only for high-voltage bushings, but also for a transformer tank. This is a multipurpose UDM machine which ensures saving the oil parameters obtained as a result of drying and degassing; oil delivery to transformer operation site, and oil filling in transformer. In terms of design, the machine is a 1,000-liter container mounted on a wheeled trailer with all the auxiliary equipment required: an input pump for oil feeding into container, an oil meter, a fine filter, a vacuum pump for maintaining the oil parameters, jack supports for securing the machine in situ, a hose for connecting the machine to a transformer, a power generator for offline operation, as well as sensors for automation and monitoring of oil filling parameters.