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This product is an earthing transformer with a built-in arc suppression coil (Petersen Coil) for centralized earth fault compensation. It can be of fixed rating type or have fixed tappings for regulating the compensation value.

This product is usually used in addition to an already existing adjustable arc suppression coil at the primary substation when the need for compensation has increased, and the existing adjustable arc suppression coil has become too small.

Shunt reactors are used for compensating capacitive reactive power generated by long and lightly loaded distribution lines and underground cables. Shunt reactors can also be designed to work as combined shunt reactors with Peterson coil duty. In such a case, the reactor will compensate for earth fault when the neutral is earthed – in other words, compensate both earth fault currents and reactive power.

When it comes to shunt reactors, good basic electrical design and a strong and rigid mechanical construction are essential. This combination reduces the vibrations in the structure and thus also the noise level.

The design of a shunt reactor for centralized compensation is, in many aspects, the same as for a traditional power transformer. There are, however, some design features that are specific for shunt reactors. For example, the shunt reactor has an iron core that is divided by one or several air gaps, which minimizes losses, noise level, and vibration.

Smaller shunt reactors can be made with a corrugated tank design, either as hermetically sealed or breathing type. For larger power ratings, we recommend using a rigid radiator tank design with an oil expansion tank.

Shunt reactors always work continuously and at full power when connected to the network, unless equipped with tappings and operated at lower power ratings. For load variation (seasonal or daily), a variable shunt reactor (VSR) can be an economical solution. Such units are generally equipped with an on-load tap changer (OLTC) for regulating the reactive power.

Specifications:

• oil-immersed shunt reactor up to 72,5 kV and 40 MVAr
• fixed or with tappings:
  • • manually operable off-circuit tap changer
    • motor-driven off-circuit tap changer
    • variable type (VSR) with on-load tap changer
• with or without arc suppression reactor function for compensation of neutral current with fixed tappings
• in accordance with reference standard IEC 60076-6

One of our solutions for distributed earth fault compensation is called BTB Treactor. The transformer earthing reactor, or Treactor, is a distribution transformer with additional features for compensating earth fault currents. It’s equipped with a built-in arc suppression reactor (Petersen Coil).

24 kV series:

• oil-immersed distribution transformer 50-1000 kVA, 20 500 V +-2×2,5 % / 400 V
• earthing transformer with maximum neutral current 15 A as standard
• arc suppression reactor for compensation of neutral current with fixed tappings: 0-5-7,5-10-12,5-15 A
• 2-hour duty cycle of the earthing transformer and arc suppression reactor. Other ratings and duty cycles are available upon request.

Shunt reactors are used for compensating capacitive reactive power generated by long and lightly loaded distribution lines and underground cables. Shunt reactors can also be designed to work as combined shunt reactors with Peterson coil duty. In such a case, the reactor will compensate for earth fault when the neutral is earthed – in other words, compensate both earth fault currents and reactive power.

Both the above-mentioned types can be further combined with a distribution transformer inside the same tank to better utilize compact substation space.

When it comes to shunt reactors, good basic electrical design and a strong and rigid mechanical construction are essential. This combination reduces the vibrations in the structure and thus also the noise level. The shunt reactor has an iron core that is divided by one or several air gaps. This design minimizes losses, noise levels, and vibration.

24 kV series:

• 20,5 kV oil-immersed shunt reactor
• fixed reactor tappings at 59-89-118-148-178 kVAr
• with or without arc suppression reactor function for compensation of neutral current with fixed tappings at 5-7,5-10-12,5-15 A
• possibility to integrate with oil-immersed distribution transformer inside the same tank
• in accordance with reference standard IEC 60076-6

A return path for an earth current is needed to protect a system against earth fault currents. Sometimes called neutral couplers or grounding transformers, earthing transformers are used to create an artificial neutral point in a three-phase system, making neutral earthing possible. The earthing can be made through e.g. an arc-suppression coil or neutral earthing resistor.

When designing earthing transformers, the rated current and fault time duration are our key design parameters.

Our standard earthing transformers are naturally cooled and hermetically sealed with a corrugated tank. The insulating liquid is inhibited mineral oil, and the standard surface treatment is suitable for environments up to corrosion level C3 (ISO 12944).

Our design is flexible and can also meet specific requirements, such as zero sequence impedance or short circuit impedance, if required.

The multi-voltage transformer, also called multi-tap transformer, is a transformer especially designed to operate at different grid voltages with a fixed secondary voltage. The various primary voltages are achieved with tapped windings connected to off-circuit tap changers.

A typical multi-voltage transformer is, in general, being transported and handled far more times compared to transformers permanently installed. The multi-voltage transformers will often operate far out under continuous heavy load (GSU / Generator Step-Up) and sometimes in high ambient temperatures. Our multi-voltage transformers are electrically, thermally, and mechanically reinforced and designed to cope with the stress and strains that may occur during transport and operation.

Transformers for rectifier and converter applications have several purposes in addition to transforming the voltage of the feeding electrical network to the voltage level of the rectifier or frequency converter.

Converter and rectifier transformers are specially designed to withstand the current harmonics caused by the rectifier or frequency converter. These transformers are usually made with multiple secondary windings that are phase-shifted (e.g., Dyn11d0) for achieving 12-, 18-, 24-pulse operation. The higher the pulse number, the better the harmonic reduction towards the supply network. However, the harmonic cancellation means additional stress on the transformer active part due to additional energy losses. The balance of impedances between the multiple secondary windings is an important design parameter when making phase-shifted transformers.

Converter and rectifier transformers are also equipped with an earthed screen between the primary and secondary windings to reduce the radio frequency disturbances caused by the converter/rectifier.

Our carefully designed transformers will work without overheating even in heavy-duty operation, ensuring overall good performance and a long lifetime.

Starting transformers are used as current limiters for starting three-phase induction motors, eliminating supply voltage dips in, for example, weak networks and for larger electrical motors.

These transformers are designed to suit a specific application. We help our customers find the right size and impedance, considering all parameters, such as the motor’s size, starting phase, starting time, load cycle, etc.

The staring transformer can be dry type air-cooled, open type for installation in a switchgear cubicle, enclosed type in a separate enclosure, or a liquid-cooled transformer tank with mineral oil or synthetic fluid.

Furnace transformers operate under severe conditions due to frequent overcurrent caused by the short circuits in the furnace and the overvoltage caused by the operating of circuit breakers.

The challenge when designing this type of transformer is the combination of high current and low voltages. Furnace transformers are usually equipped with on-load voltage regulation for operating the furnace at different stages of the process.

The transformer’s mechanical design is usually made to fit the on-site space limitations and the LV bushing arrangement to fit the interconnections to the furnace. The cooling is typically forced water cooling (OFWF) since the transformers, in most cases, are located close to the furnace due to the high current on the transformer secondary side.

Traction transformers are always designed and manufactured according to a specific railway system and based on detailed parameters.

Traction systems can be divided into two major groups: AC and DC systems.

Typical system set-ups are:

• 15 kV AC 16 1/3 Hz
• 25 kV AC 50 Hz
• 1.5 kV DC
• 3 kV DC
• 1.2 kV DC

In the traction system, you may have a combination of stationary transformers (supply- or feeding transformers) and autotransformers as well as booster transformers. There are mainly three different systems in use:

• Single-phase feeding system with a return conductor
• Single-phase feeding system with a booster transformer
• Two-phase feeding system with an autotransformer

Each of these systems has its advantages, which should be considered when choosing the traction system.

Our standard booster transformer is developed for the Finnish railway system at 25 kV AC 50 Hz. We can also design and manufacture booster transformers for other markets according to the customer’s specific requirements.