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7.2 Parts of a Power Transformer

In addition to structural elements, we classify the components of a power transformer in:

Active parts: This label encompasses the magnetic and electric circuits, which are the elements responsible for the reception and transmission of electrical energy within the transformer. The input/output system enables the interconnection of the transformer's electrical circuit with its input and output power lines. The input and output system of a transformer comprises primarily high-voltage terminals (insulators with smaller conductors) and low-voltage terminals (insulators with larger conductors) (Fig. 7.4). In addition, the transformer comprises a number of other components, including the cooling system, which plays an important role in the transformer's functionality.

! Diagram of an electrical circuit showing a transformer with labeled components. The transformer includes multiple insulators and connections, with numbered labels indicating specific parts. A large circular component is connected via a pipe, and several internal structures are visible, suggesting the flow of electricity. The diagram is detailed, focusing on the arrangement and interaction of the components within the transformer system.

Fig. 7.4 Parts in a power transformer. Original from Fluppe37 at nl.wikipedia. Source From wikicommons under 3.0 CC use license [3]

Parts in a power transformer include:

Tank
Lid
Conservator tank
The oil level indicator (end of conservator tank)
Buchholz relay for detecting gas bubbles after an internal fault
Piping to conservator tank and Buchholz relay
Tap changer to change output voltage
The motor drive of the tap changer (can be controlled by an automatic voltage regulator)
Drive shaft for tap changer
High voltage (HV) bushing connects the internal HV coil with the external HV grid
High voltage bushing current transformers for measurement and protection
Low voltage (LV) bushing connects LV coil to LV grid
Low voltage current transformers
Bushing voltage-transformer for metering the current through the passing bushing
Core
Yoke of the core
Limbs connect the yokes and hold them up
Coils
Internal wiring between coils and tap changer
Oil release valve
Vacuum valve

These components are necessary for good transformer operation. As other electrical machines during operation it emits heat, which must dissipate into the surrounding environment in order to maintain the operational temperature within acceptable limits.

练习题

What do the 'active parts' of a power transformer encompass?

A. The cooling system and oil circulation components

B. The magnetic and electric circuits responsible for reception and transmission of electrical energy

C. The structural elements such as the tank and lid

D. The protection devices and monitoring equipment

Which statement correctly describes the difference between high-voltage (HV) and low-voltage (LV) terminals in a transformer?

A. HV terminals have larger conductors and LV terminals have smaller conductors

B. HV terminals have smaller conductors and LV terminals have larger conductors

C. Both HV and LV terminals have the same conductor size

D. HV terminals use copper conductors while LV terminals use aluminum conductors

What is the primary purpose of the Buchholz relay in a power transformer?

A. To regulate the output voltage automatically

B. To measure the current through the bushing

C. To detect gas bubbles after an internal fault

D. To connect the internal coil with the external grid

Which of the following components are considered part of the active parts of a power transformer? (Select all that apply)

A. Core

B. Coils

C. Yoke of the core

D. Conservator tank

E. Internal wiring between coils and tap changer

Which of the following statements about transformer bushings are correct?

A. HV bushing connects the internal HV coil with the external HV grid

B. LV bushing connects the LV coil to the LV grid

C. HV bushing current transformers are used for measurement and protection

D. Bushing voltage-transformers are used for metering current through the passing bushing

The tap changer in a power transformer is used to change the output voltage.

The high-voltage (HV) bushing connects the external HV coil with the internal HV grid.

Like other electrical machines, a transformer emits heat during operation that must dissipate into the surrounding environment to maintain acceptable operational temperature limits.

The Buchholz relay is designed for detecting ___ after an internal fault in a power transformer.

In a power transformer, the limbs connect the ___ and hold them up.

Explain the relationship between the active parts of a transformer and its primary and secondary windings.

Describe the function of the input/output system in a power transformer and name its primary components.

In a step-down transformer, which statement correctly describes the relationship between the high-voltage (HV) bushing and the transformer windings?

A. The HV bushing connects the internal HV coil to the external HV grid, and since the HV side is the primary in a step-down transformer, this bushing connects to the winding that receives power.

B. The HV bushing connects to the secondary winding because the HV side always delivers power in any transformer.

C. The HV bushing is only used for measurement purposes and does not connect to any power windings.

D. The HV bushing connects to the LV coil because higher voltage requires smaller conductors.

The active parts of a power transformer, which encompass the magnetic and electric circuits, correspond to the core active elements described for static machines: the primary and secondary electrical circuits and the magnetic core.

Which of the following statements correctly describe how transformer components relate to the formation of electrical circuits in transformers?

A. Transformer loops are formed by winding conductors on the appropriate magnetic core.

B. The coils (item 18 in the transformer parts list) form the electrical circuits of the transformer.

C. The core and yoke (items 15 and 16) form the magnetic circuit of the transformer.

D. The Buchholz relay forms part of the electrical circuit for power transmission.

E. Concentric windings are commonly used in transformers to save material and space.

In a step-up transformer, the low-voltage (LV) bushing connects to the ___ winding, which is the side through which the transformer receives energy.

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