Shunt reactor with auxiliary power

Abstract

A shunt reactor is presented comprising a primary winding (1) and a steel core (2). The steel core comprises a bottom yoke (3), a top yoke (4), a first limb (5), a second limb (6) and a main limb (7). The first limb, the second limb and the main limb are arranged in parallel and between the top yoke and the bottom yoke to form a support to a magnetic flux passing through the steel core. The primary winding is wound around the main limb to generate the magnetic flux passing through the steel core. The shunt reactor further comprises an auxiliary winding (8; 8') arranged to be wound around the bottom yoke, the top yoke, the first limb or the second limb and configured to generate an auxiliary electric power from the magnetic flux generated by the primary winding. The primary winding and the auxiliary winding are electrically insulated from the steel core and from each other. A cooling fan (12) is configured to be driven by the auxiliary electric power generated by the auxiliary winding.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to shunt reactors. BACKGROUND

[0002] The main application of shunt reactors is to supply inductive power to the power grid in order to keep voltage stability and power factor at an appropriate level. Shunt reactors are usually self-cooled equipment, i.e. only passive radiators are used to reduce the oil temperature and are similar to a thermosyphon.

[0003] Shunt reactors dissipate energy due to Joule effect, hysteresis losses and other principles. A general engineering goal is to reduce as much as possible the energy dissipated in the equipment, for example by using better quality materials and arranging the components in an optimized layout.

[0004] In power systems, the losses can be tens of kilowatts, which makes cooling an important factor regarding the equipment design.

[0005] The cooling system of a shunt reactor can be more efficient if a fan is used in combination with passive radiators. When an auxiliary fan is combined with the passive cooling of a shunt reactor, a higher flexibility is achieved to operate the shunt reactor under non-standard conditions, such as overvoltage and high ambient temperature, without affecting the expected lifetime of the shunt reactor. A shunt reactor with less footprint and lower mass can be provided, allowing to reduce the equipment cost, the consumption of raw materials, such as copper and steel, and the cost of civil works. Most importantly, a better control of the expected lifetime can be further achieved.

[0006] When a shunt reactor is equipped with a fan, the cooling fan and other auxiliary devices usually require an external power supply. However, in shunt reactors located in remote areas, the auxiliary power required to obtain cooling and other devices arranged to be connected with the shunt reactor can be both complex and expensive.

[0007] In US 1984996, a ventilation system for electrical windings is provided, in which a cooling fan is used that is excited by an auxiliary winding arranged inside the main winding. However, this solution cannot be directly applied to shunt reactors. SUMMARY

[0008] It is an object of the present invention how to implement an auxiliary power supply in a shunt reactor.

[0009] According to an aspect of the present invention, a shunt reactor is presented, comprising a primary winding and a steel core. The steel core comprises a bottom yoke, a top yoke, a first leg, a second leg and a main column. The first leg, the second leg and the main column are arranged in parallel and between the top yoke and the bottom yoke to form a support to the magnetic flux passing through the steel core. The primary winding is wound around the main column to generate the magnetic flux passing through the steel core. The shunt reactor further comprises an auxiliary winding arranged to be wound around the bottom yoke, the top yoke, the first leg or the second leg and configured to generate an auxiliary electric power from the magnetic flux generated by the primary winding. The primary winding and the auxiliary winding are electrically insulated from the steel core and the primary winding and the auxiliary winding are electrically insulated from each other.

[0010] The shunt reactor can further comprise a cooling fan configured to be driven by the auxiliary electric power generated by the auxiliary winding.

[0011] The shunt reactor can further comprise a cabinet and cooling radiators, wherein the primary winding and the steel core are arranged inside the cabinet. The cooling radiators can be arranged on the outside of the cabinet and configured to passively cool the cabinet. The cooling fan can be configured to increase the air circulation through the cooling radiators to improve their cooling efficiency.

[0012] The shunt reactor can further comprise a control cabinet arranged outside the cabinet, a feedthrough flange through the cabinet, and a power cable connected to the control cabinet and the auxiliary winding. The power cable can be arranged to pass through the feedthrough flange.

[0013] The auxiliary winding can comprise a number of turns around the bottom yoke, the top yoke, the first leg or the second leg, the number of turns being configured depending on the magnetic flux density in the steel core and the operating voltage of the cooling fan.

[0014] The auxiliary winding applies the magnetic induction inside the shunt reactor core as an auxiliary power source, which can be used for e.g. shunt reactor cooling. Thus, no external power source is needed to power the cooling fan.

[0015] Further, the auxiliary circuit will require less cabling and the operational risks due to e.g. weather effects on the cables and / or protection devices are reduced.

[0016] Generally, unless otherwise indicated herein, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field. All references to "a / an / the [element, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed unless explicitly stated. BRIEF DESCRIPTION OF DRAWINGS

[0017] Aspects and embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

[0018] Figure 1 is a diagram schematically illustrating an overview of a shunt reactor according to embodiments presented herein;

[0019] Figure 2 is a diagram schematically illustrating in detail a part of the shunt reactor shown in Figure 1 ; and

[0020] Figure 3 is a diagram schematically illustrating in detail a part of an alternative configuration of the active part of the shunt reactor shown in Figure 1 . DETAILED DESCRIPTION

[0021] Aspects of the disclosure will now be described more fully below with reference to the accompanying drawings, in which certain embodiments of the application are shown.

[0022] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of all aspects of the application to those skilled in the art. Like reference numerals refer to like elements throughout the description.

[0023] According to aspects of the present application, reference is made to Figure 1 and Figure 2 A shunt reactor is presented, the shunt reactor comprising a primary winding 1 and a steel core 2. The steel core comprises a bottom yoke 3, a top yoke 4, a first limb 5, a second limb 6 and a main limb 7. The first limb 5, the second limb 6 and the main limb 7 are arranged in parallel and between the top yoke 4 and the bottom yoke 3 to form a support for a magnetic flux passing through the steel core 2. The primary winding 1 is wound around the main limb 7 to generate the magnetic flux passing through the steel core 2. The shunt reactor further comprises an auxiliary winding 8 wound around the bottom yoke 3, the top yoke 4, the first limb 5 or the second limb 6 and configured to generate an auxiliary electric power from the magnetic flux generated by the primary winding 1. The primary winding 1 and the auxiliary winding 8 are electrically insulated from the steel core 2 and from each other.

[0024] The shunt reactor can further comprise a cooling fan 12 configured to be driven by the auxiliary electric power generated by the auxiliary winding 7.

[0025] The shunt reactor can further comprise a tank 10 and cooling radiators 13. The primary winding 1 and the steel core 2, i.e. the active part 9 of the shunt reactor, are arranged inside the tank and the cooling radiators 13 are arranged on the outside of the tank 10 and are configured to passively cool the tank 10. Cooling fans are configured to increase the air circulation through the cooling radiators to improve their cooling efficiency.

[0026] The shunt reactor can further comprise a control cabinet 11 arranged outside the tank 10, feed-through flanges 14 through the tank 10, and power cables 15 connected to the control cabinet 11 and the auxiliary winding 1. The power cables 15 are arranged to pass through the feed-through flanges 14.

[0027] The auxiliary winding 8 can comprise several turns around the bottom yoke 3, the top yoke 4, the first leg 5 or the second leg 6. The number of turns can be configured depending on the magnetic flux density in the steel core 2 and the operating voltage of the cooling fans 12.

[0028] The aspects of the present invention will be described in further detail next. Figure 1 and Figure 2 The aspects of the present invention will be described in further detail next.

[0029] The steel core 2 can be described as having the shape of a number 8 lying on its side in a straight line. Thus, the top yoke 4 is arranged upwards from the first leg 5, the second leg 6 and the main leg 7, and the bottom yoke 3 is arranged below the first leg 5, the second leg 6 and the main leg 7. The steel core 2, including the legs 5, the bottom yoke 3, the top yoke 4 and the main leg 7, is regarded as a one-piece part from an electromagnetic point of view, even though the different parts are usually manufactured separately and then assembled together.

[0030] The control cabinet 11 can be configured to detect the temperature of the shunt reactor and to control the cooling fans 12 depending on the temperature. The temperature can be measured in the top of the tank 10 by a temperature sensor 16. The cooling fans 12 can be powered by direct connections 15 to the auxiliary winding 5 or via the control cabinet 11. In the latter case, voltage control can be applied to the auxiliary power to adapt it to different electrical equipment.

[0031] The shunt reactor can be regarded as two parts: the active part 9 inside the tank 10, and the external part comprising the tank 10 and other external devices and accessories.

[0032] The active part 9 is immersed in oil that acts as a coolant and a dielectric insulating medium. The heat generated in the primary winding 1 and the auxiliary winding 8 and the steel core 2 is transferred to the oil, and the oil exchanges heat with the radiators 13.

[0033] Cooling is achieved through natural convection of oil internally within the windings / steel core and natural convection of oil to air externally via the radiator 13 of the housing 10. According to international standards, this is known as Oil-Immersed Natural-Air Natural–ONAN.

[0034] By installing an auxiliary winding 8 wrapped around the steel core 2, the magnetic flux from the primary winding 1 can be utilized.

[0035] The steel core 2 of the shunt reactor can be made, for example, of steel sheet, and is the heaviest part of the shunt reactor. Therefore, the steel core 2 can advantageously be equipped with additional parts and components for structural support. These additional parts and components are mainly located on the sides of the steel core 2, near the first core post 5 and the second core post 6, but generally have gaps above the top yoke 4. Thus, the auxiliary winding 8 is illustrated in this advantageous position around the top yoke 4, even though the same auxiliary power can be received from the positions around the bottom yoke 3, the first core post 5, and the second core post 6.

[0036] The active part 9 has been referenced. Figure 1 and Figure 2 A description is provided for single-phase applications. (Reference) Figure 1 and Figure 3 A three-phase application is presented. The active section 9 is similar for the three-phase application, except that the core includes three parallel main posts 7a, 7b, and 7c between the bottom yoke 3 and the top yoke 4, and the primary winding includes one winding 1a, 1b, and 1c per phase, which are wound around the three main posts 7a, 7b, and 7c respectively. The location of the auxiliary winding 8 is further illustrated around the bottom yoke 3 rather than the top yoke 4, even though the same auxiliary power can be received from the locations around the bottom yoke 4, the first core post 5, and the second core post 6.

[0037] The aspects of this disclosure have been described above primarily with reference to several embodiments and examples thereof. However, as will be readily apparent to those skilled in the art, other embodiments besides those disclosed above are also possible within the scope of the invention as defined by the appended claims.

Claims

1. A parallel reactor, comprising a primary winding (1) and a steel core (2); - The steel core includes a bottom yoke (3), a top yoke (4), a first core post (5), a second core post (6), and a main post (7), wherein, The first core post, the second core post, and the main post are arranged in parallel and between the top yoke and the bottom yoke to support the magnetic flux through the steel core; and - The primary winding is wound around the main post to generate the magnetic flux through the steel core; The shunt reactor is characterized in that it further comprises: - An auxiliary winding (8; 8') is arranged to be wound around the bottom yoke, top yoke, first core post, or second core post and is configured to generate auxiliary power from the magnetic flux generated by the primary winding; - Wherein, the primary winding and the auxiliary winding are electrically insulated from the steel core and the primary winding and the auxiliary winding are electrically insulated from each other. -The cooling fan (12) is configured to be driven by the auxiliary power generated by the auxiliary winding. -The auxiliary winding includes a number of turns around the bottom yoke, top yoke, first core post or second core post, the number of turns being configured depending on the magnetic flux density in the steel core and the operating voltage of the cooling fan.

2. The parallel reactor according to claim 1, further comprising a housing (10) and a cooling radiator (13), wherein, The primary winding and the steel core are arranged inside the housing, and the cooling radiator is arranged on the outside of the housing and configured to passively cool the housing, wherein the cooling fan is configured to increase air circulation through the cooling radiator to improve their cooling efficiency.

3. The parallel reactor according to claim 2, further comprising a control cabinet (11) disposed outside the enclosure, a feedthrough flange (14) passing through the enclosure, and a power cable (15) connected to the control cabinet and the auxiliary winding, the power cable being disposed through the feedthrough flange.

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