Distribution transformer and system for providing power from source grid to customer site

Abstract

A distribution transformer for providing power to a site includes a ferromagnetic core; a primary winding configured to be connected to a source grid at a source grid voltage; and a secondary winding configured to be coupled to a service cable that supplies electrical energy to at least one of the sites at a first line voltage and supplies electrical energy to at least another of the sites at a second line voltage, where the second line voltage is higher than the first line voltage.

Description

Technical Field

[0001] This disclosure pertains to the distribution of electricity from the power grid to residential sites. Background Technology

[0002] The increase in electricity use in homes and businesses has resulted in a significant transfer of electricity to customer sites, including residential sites. High-voltage electricity is distributed through the source grid. Distribution transformers are used near residential sites, for example, to connect to the source grid and supply power to nearby residential sites at a voltage lower than that found in the source grid. Distribution transformers supply power through secondary conductors (also known as service cables) that connect the distribution transformer to the residential sites at a line voltage of 120 V, for example, to provide 120 V / 240 V service to each residential site.

[0003] Service cables connecting to residential sites consist of conductive metallic material (called conductors) encased in an insulating sheath. The type and size of the conductor, as well as the insulation, are the primary factors determining the upper limits of the conductor's current and voltage. Other environmental factors can reduce the conductor's energy transfer capabilities.

[0004] As residential site demand for electricity continues to increase, service cables that were previously sufficient to provide the required power may no longer be adequate. To meet this demand, service cables, typically located underground, are replaced with larger service cables capable of delivering higher currents, thus providing a greater amount of power to the residential site. For example, an I / O site inlet cable that was previously sufficient to provide 100 A of service to a residence may no longer be sufficient and can be replaced with a 4 / O site inlet cable to provide 200 A of service.

[0005] The complexity and cost of replacing service cables are substantial, with the buried power distribution conductors located around and above them, including in landscaping and civil infrastructure. These costs will amount to billions of dollars annually over the next few decades.

[0006] The goal is to improve power distribution to residential sites. Summary of the Invention

[0007] According to one aspect of the embodiment, a distribution transformer for supplying power to stations is provided. The distribution transformer includes: a ferromagnetic core; a primary winding configured to be connected to a source grid voltage; and a secondary winding configured to be coupled to a service cable supplying power to at least one of the stations at a first line voltage and to at least another of the stations at a second line voltage, wherein the second line voltage is higher than the first line voltage.

[0008] According to another aspect of the embodiments, a system is provided for connecting a source grid to a residential site including a first residential site and a second residential site. The system includes: a distribution transformer for providing power, the distribution transformer having at least one primary voltage connection connected to the source grid at a source grid voltage, and a secondary voltage connection for providing power to the first residential site and the second residential site; a first service cable group connecting these secondary voltage connections to the first residential site at a residential line voltage suitable for residential service at the first residential site; and a second service cable group connecting these secondary voltage connections to the second residential site at a line voltage higher than these residential line voltages for step-down at the second residential site.

[0009] According to another aspect of the embodiments, a method is provided for transmitting electrical energy from a source grid to a residential site including a first residential site and a second residential site. The method includes: using a distribution transformer to step down the grid voltage to a line voltage of 120 V along a first service cable group, and providing a 120 V / 240 V service to the first residential site; and using the distribution transformer to step down the grid voltage to 480 V along a second service cable group, to provide 480 V and 100 A for stepping down at the second residential site. Attached Figure Description

[0010] Embodiments of this disclosure will now be described by way of example only with reference to the accompanying drawings, in which:

[0011] Figure 1 This is a schematic diagram of an existing electrical system; Figure 2 This is a schematic diagram of an example electrical system according to an embodiment; Figure 3 This is a front view of an example of a distribution transformer according to one aspect of an embodiment; Figure 4 This is a cross-sectional side view of a distribution transformer according to one aspect of an embodiment; Figure 5 This is a schematic diagram illustrating an example of a distribution transformer according to one aspect of an embodiment; Figure 6 This is a schematic diagram illustrating another example of a distribution transformer according to one aspect of an embodiment; Figure 7 This is a schematic diagram illustrating another example of a distribution transformer according to one aspect of an embodiment; Figure 8 This is a schematic diagram illustrating yet another example of a distribution transformer according to one aspect of an embodiment; and Figure 9This is a schematic diagram illustrating yet another example of a distribution transformer according to one aspect of an embodiment. Detailed Implementation

[0012] For the sake of simplicity and clarity, reference numerals may be repeated in the accompanying drawings to indicate corresponding or similar elements. Numerous details are set forth to provide an understanding of the examples described herein. These examples can also be practiced without these details. In other instances, well-known methods, processes, and components have not been described in detail to avoid obscuring the described examples. This description is not intended to limit the scope of the examples described herein.

[0013] As mentioned above, the service cables providing electrical connections to existing residences are limited based on conductor type and size, insulation, and environmental factors. For example, limitations on service cables can depend on whether the service cable is buried directly or in underground conduits, the depth of the burial, the soil thermal resistivity, whether the service cable is bundled with other conductors, its proximity to other conductors or heat sources, the variety of loads and load factors, ambient temperature, ground temperature, and other factors.

[0014] In many cases, service cables are insufficient to supply the higher current to a residence. However, voltage limitations may be high enough that the rated voltage of the service cable significantly exceeds the voltage utilized at the residential site. Historically, the size of service cables was determined by matching the current supplied to the residential site. As electricity demand increases while voltage remains constant, current increases, necessitating the replacement of service cables.

[0015] The distribution transformer connected to the service cable converts high-voltage power from the source grid into one or two lower secondary voltages for use at residential sites. This is achieved using a primary winding structure with multiple turns of electrical conductors wound around a ferromagnetic core and a secondary winding structure. The same lower secondary voltage is provided to all residential sites connected to the transformer. To change the voltage at one residential site, the secondary voltages of all residential sites must be changed, or a separate distribution transformer must be used.

[0016] Figure 1 This is a schematic diagram illustrating an existing electrical system in which a distribution transformer 102 connects a power grid 104 to three residential sites 106. The distribution transformer includes a primary winding connected to the power grid 104 at a power grid voltage of 15 / 25 kV, and a secondary winding surrounding the core for supplying power to a first residential site at a line voltage of 120 V. A corresponding service cable 112 connects the secondary winding to each of the residential sites 106, providing 120 / 240 V and 100 amps of service at each residential site 106.

[0017] Instead of replacing service cables or installing multiple transformers, a single distribution transformer, as disclosed in this disclosure, simultaneously supplies three or more secondary voltages to different residential sites. One set of voltages may be equal to the original or typical voltage allocated to a residential site, while other higher voltages are provided to facilitate the delivery of a larger volume of power to one or more other residential sites. Therefore, a greater volume of power can be supplied to residential sites using existing service cables.

[0018] Then, a site transformer is used at each residential site that provides these other higher voltages. The site transformer is connected to the service cable of the residential site and is used to reduce the voltage to the residential voltage, for example, and to provide a higher current than previously supplied to the residence.

[0019] Therefore, an electrical system for connecting a source grid to residential sites including a first residential site and a second residential site includes a distribution transformer for supplying power. The distribution transformer has: a ferromagnetic core; a primary winding surrounding the core for connecting to the source grid at a source grid voltage; and a secondary winding surrounding the core for supplying power to the first residential site at a line voltage of 120 V and to the second residential site at a line voltage of 480 V. A first service cable assembly connects the secondary winding to the first residential site at a line voltage of 120 V and provides 100 amps of service at the first residential site at 120 V and 240 V. A second service cable assembly connects the secondary winding to the second residential site at a line voltage of 480 V and a current of 100 A. The site transformer includes a site core; a site primary winding surrounding the site core that can be coupled to a second service cable bundle; and a site secondary winding surrounding the site core that is coupled to the site cable to provide 200 amps of service at 120 V and 240 V at the second residential site.

[0020] refer to Figure 2 The figure illustrates an example electrical system 200 according to an embodiment. The electrical system 200 includes a distribution transformer 202 that connects a power grid 204 to residential sites, which in this example include three residential sites referred to as a first residential site 206, a second residential site 208, and a third residential site 210.

[0021] Distribution transformer 202 can be any suitable distribution transformer. Distribution transformer 202 is connected to source grid 204 with a source grid voltage, which can be in the range of approximately 15 kV to 25 kV. Other grid voltages (such as 5 kV, 8 kV, 35 kV, or any other suitable grid voltage) are also possible. Distribution transformer 202 also includes connectors 211, 212, 213, 214, and 215, which are used to supply power to the first residential substation 206, the second residential substation 208, and the third residential substation 210. Other distribution transformers can be successfully employed.

[0022] The first service cable bundle 216 connects the distribution transformer 202 to the first residential site 206 with line voltages for use at the residential site. These line voltages may be, for example, 120 V, thus providing 120 V / 240 V and 100 A service at the first residential site 206.

[0023] The second service cable bundle 218 connects the distribution transformer 202 to the second residential site 208 with line voltages for use at the residential site. These line voltages may be, for example, 120 V, thus providing 120 V / 240 V and 100 A service at the second residential site 208.

[0024] The third service cable bundle 220 connects the distribution transformer 202 to the third residential site 210 at a higher line voltage than the first service cable bundle 216 and the second service cable bundle 218. The third service cable bundle 220 can provide electrical connection at a line voltage of 480 V and 100 A.

[0025] Site transformer 224 includes a site primary winding and a site secondary winding surrounding the site core, and is used to convert a higher line voltage, such as 480 V, to a residential voltage, such as 120 / 240 but 200 A. The site primary winding is connected to a third service cable bank 220 to draw power from the distribution transformer. Site cable 228 is connected to the site secondary winding to distribute power at the third residential site 210 at a lower voltage and a higher current than the voltage received via service cable 220.

[0026] The site transformer 224 can be, for example, a 50kVA isolation transformer – 240 / 480 V primary – 120 / 240 V secondary – single phase.

[0027] Therefore, the use of distribution transformer 202 and site transformer 224 facilitates the distribution of power to residential sites at different voltages, including providing 100 A of service to one or more residential sites at a line voltage of, for example, 120 V, while also providing a higher voltage, for example, 480 V, to one or more other residential sites at a current of 100 A. Site transformer 224 receives the higher voltage and provides a lower voltage, for example, 120 V / 240 V, and a higher current of 200 A at the residential sites.

[0028] exist Figure 3 The image shows a front view of an example distribution transformer 202 according to an embodiment. In this example, the distribution transformer 202 includes a primary winding 302 and a secondary winding 304 surrounding a ferromagnetic core 306. Primary voltage connectors 308, 310 are used to connect to the primary winding 302 wound around a post 312 of the ferromagnetic core 306. Although two primary voltage connectors 308, 310 are shown, alternatively, a single primary voltage connector may be used to connect to the primary winding 302, and another connector may be used to connect to ground.

[0029] Secondary voltage connectors 211, 212, 213, 214, and 215 are used to connect to the secondary winding 304 that is wrapped around the second post 313 of the ferromagnetic core 306.

[0030] Primary voltage connectors 308 and 310 are connected to the power grid at the source grid voltage. Secondary voltage connectors 211, 212, 213, 214, and 215 are connected to the first service cable group 216, the second service cable group 218, and the third service cable group 220.

[0031] The example shown and described illustrates three residential sites. However, the distribution transformer 202 can be used to connect to any suitable number of residential sites. For example, the distribution transformer 202 can be used to connect to approximately 12 residential sites.

[0032] Figure 4 An example of a distribution transformer 202 housed in a housing 402 is shown. The distribution transformer 202 includes secondary voltage connectors 211, 212, 213, 214, and 215, which are connected to a secondary winding 304 that surrounds a second post 312 of a ferromagnetic core 306. The secondary voltage connectors 211, 212, 213, 214, and 215 are located on a connection surface 404 within the housing 402 and are accessible within the housing 402 via a hinged door 406.

[0033] As mentioned above, distribution transformers are not limited to Figure 3 and Figure 4 The exact transformer shown is not specified. Other distribution transformers can be successfully used. Figures 5 to 9 Examples of distribution transformers are shown. Different reference numerals are used to describe each example of a distribution transformer in this article.

[0034] exist Figure 5 In the example, the distribution transformer is a center-tapped single-phase transformer 500. Primary voltage connectors 502 and 504 are electrically coupled to the primary winding 508 and connected to the power grid to supply power to the primary winding 508 wound around the ferromagnetic core 506.

[0035] The secondary winding 509 is also wound around the ferromagnetic core 506 and is subdivided along the length of the secondary winding 509 to provide different secondary voltages at the secondary voltage connectors 510, 512, 514, 516, and 518 in accordance with Faraday's law of induction.

[0036] Three center secondary voltage connectors 510, 512, and 514 can be used to connect to a service cable to provide power to a residential site at the line voltage used at the residential site, for example, thereby providing 120 V / 240 V service at the residential site.

[0037] External and intermediate secondary voltage connectors 510, 516, and 518 can be used to connect to service cables to provide power to other residential sites at higher line voltages, for example, to provide 480 V service.

[0038] Figure 6 Another example of a suitable distribution transformer is shown. In this example, the distribution transformer is a single-column segmented single-phase distribution transformer 600. Primary voltage connectors 602 and 604 are electrically coupled to the primary winding 608 and connected to the power grid to supply power to the primary winding 608 wound around the ferromagnetic core 606.

[0039] In this example, the secondary winding 609 is also wound around the ferromagnetic core 606 and is subdivided along its length into four connections to provide different secondary voltages at the secondary voltage connectors 610, 612, 614, and 616 in accordance with Faraday's law of induction.

[0040] In this example, the three bottom secondary voltage connectors 610, 612, and 614 can be used to connect to the service cable to provide power to the residential site at the line voltage used at the residential site, for example, thereby providing 120 V / 240 V service at the residential site.

[0041] The top two secondary voltage connectors 610 and 616 can be used to connect to the service cable to provide power to other residential sites at a higher line voltage, for example, to provide 480 V service.

[0042] Figure 7 Another example of a suitable distribution transformer is shown. In this example, the distribution transformer is a three-stage single-phase distribution transformer 700. Primary voltage connectors 702 and 704 are electrically coupled to the primary winding 708 and connected to the power grid to supply power to the primary winding 708 wound around the ferromagnetic core 706.

[0043] The secondary winding comprises two windings 709 and 710 wound around a ferromagnetic core 706. The first secondary winding 709 is subdivided along its length with connections to provide different secondary voltages at secondary voltage connectors 712, 714, and 716 according to Faraday's law of induction. The second secondary winding structure 710 has connections at its ends to provide a single secondary voltage at secondary voltage connectors 718 and 720.

[0044] In this example, the three bottom secondary voltage connectors 712, 714, and 716 in the diagram can be used to connect to the service cable to provide power to the residential site at the line voltage used at the residential site, for example, thereby providing 120 V / 240 V service at the residential site.

[0045] The two secondary voltage connectors 718 and 720 above can be used to connect to the service cable to provide power to other residential sites at a higher line voltage, for example, to provide 480 V service.

[0046] Figure 8 Another example of a suitable distribution transformer is shown. In this example, the distribution transformer is a single-phase tap-out transformer 800. Primary voltage connectors 802 and 804 are electrically coupled to a single winding 808 and connected to a source grid to supply power to the winding 808 wound around a ferromagnetic core.

[0047] The unique winding structure 808 is subdivided along its length into connections to provide different secondary voltages at secondary voltage connectors 810, 812, 814, and 816 respectively, in accordance with Faraday's law of induction.

[0048] In the example shown, three lower secondary voltage connectors 810, 812, and 814 can be used to connect to the service cable to provide power to the residential site at the line voltage used at the residential site, for example, thereby providing 120 V / 240 V service at the residential site.

[0049] The secondary voltage connector 816 above can be used to connect to a service cable to provide power to other residential sites at a higher line voltage, for example, to provide 480 V service.

[0050] Figure 9Another example of a suitable distribution transformer is shown. In this example, the distribution transformer is a three-phase distribution transformer 900. Primary voltage connectors 902, 904, and 906 are electrically coupled to primary windings 908, which may be configured in a delta or Y configuration, and these primary voltage connectors are connected to a source grid to provide power to the primary windings 908 wound around a ferromagnetic core 910.

[0051] Secondary windings 912 are wound around corresponding ferromagnetic cores in ferromagnetic cores 910. In this example, the secondary windings 912 are interconnected in a delta configuration, have connections at the interconnection points of the secondary windings 912, and one of these secondary windings is subdivided along its length with connections. These connections provide different voltages at connectors 914, 916, 918, 920, and 922.

[0052] In the example shown, three lower center secondary voltage connectors 914, 916, and 918 can be used to connect to the service cable to provide power to the residential site at the line voltage used at the residential site, for example, thus providing 120 V / 240 V service at the residential site.

[0053] The two secondary voltage connectors 920 and 922 above can be used to connect to the service cable to provide power to other residential sites at a higher line voltage, for example, to provide 480 V service.

[0054] Advantageously, the distribution transformers according to this disclosure simultaneously supply three or more secondary voltages to different residential sites. One set of voltages may be equal to the original or typical voltage allocated to a residential site, while other higher voltages are provided to facilitate the delivery of a larger amount of power to one or more other residential sites. Therefore, a greater amount of power can be supplied to residential sites using existing service cables.

[0055] The scope of the claims should not be limited to the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the entire specification.

Claims

1. A distribution transformer for supplying power to a site, the distribution transformer comprising: Ferromagnetic core; A primary winding configured to be connected to the source grid at the source grid voltage; A secondary winding configured to be coupled to a service cable supplying power to at least one of these sites at a first line voltage and to at least another of these sites at a second line voltage, wherein the second line voltage is higher than the first line voltage.

2. The distribution transformer according to claim 1, wherein, These service cables include a first service cable group for supplying power to a first of these sites at the first line voltage, wherein the first line voltage is 120 V.

3. The distribution transformer according to claim 2, wherein, These service cables include a second service cable group for supplying power to a second of these sites at the second line voltage, wherein the second line voltage is 480 V.

4. The distribution transformer according to claim 1, wherein, The secondary winding is configured to be coupled to a first plurality of stations among these stations using the service cables of the corresponding group to supply power at 480 V.

5. The distribution transformer according to claim 4, wherein, The secondary winding is configured to be coupled to a second or more stations among these stations using the service cables of the corresponding group to supply power at a line voltage of 120 V.

6. A system for connecting a power grid source to a residential site including a first residential site and a second residential site, the system comprising: A distribution transformer for providing electricity, the distribution transformer having at least one primary voltage connection connected to the source grid at the source grid voltage, and a secondary voltage connection for providing electrical energy to the first residential site and the second residential site; A first service cable bundle connects these secondary voltages to the residential line voltage suitable for residential service at the first residential site. The second service cable group connects these secondary voltages to the second residential site with a line voltage that is higher than the residential line voltage and is used to step down the voltage at the second residential site.

7. The system according to claim 6, wherein, The first service cable bundle connects these secondary voltage connections to the first residential site at 120 V residential line voltage, thereby providing 120 V / 240 V service.

8. The system according to claim 7, wherein, The second service cable bundle connects these secondary voltage connections to the second residential site with a higher line voltage of 480 V, thereby providing the residential site with 480 V and 100 amps.

9. The system according to any one of claims 6 to 8, comprising a site transformer including a site core, a site primary winding surrounding the site core and coupled to the second service cable assembly, and a site secondary winding surrounding the site core and coupled to the site cable to provide service at the second residential site.

10. The system according to claim 9, wherein, These site cables connect the site transformer to the second residential site at 120 V residential line voltage, thereby providing the second residential site with 120 V / 240 V and 200 amps of service.

11. The system according to claim 9, wherein, The system is used to connect to other residential sites, and the system includes additional service cable bundles, each of which connects the secondary winding to the corresponding residential site among these additional residential sites.

12. The system according to claim 11, wherein, These additional service cable assemblies include additional first cable assemblies that connect the secondary winding to the residential sites in these additional residential sites at a line voltage of 120 V and provide 120 V / 240 V service at the respective residential sites.

13. The system according to claim 11 or claim 12, wherein, These additional service cable assemblies include additional second cable assemblies, which each connect the secondary winding to a corresponding other residential site in these additional residential sites with a corresponding line voltage of 480 V.

14. The system of claim 13, comprising a plurality of additional site transformers, each site transformer having an additional primary winding connected to a corresponding group in these additional second service cable groups, and an additional secondary winding coupled to the additional site cables to provide 120 V / 240 V and 200 amp service at corresponding other residential sites in these additional residential sites.

15. A method for transmitting electrical energy from a source grid to a residential site including a first residential site and a second residential site, the method comprising: Using a distribution transformer, the grid voltage is stepped down to the line voltage of 120 V along the first service cable group, and 120 V / 240 V service is provided to the first residential site; The distribution transformer is used to step down the grid voltage to 480 V along the second service cable group to provide 480 V and 100 A for stepping down at the second residential site.

16. The method of claim 15, further comprising using a site transformer to step down the 480 V and 100 A along the second service cable bundle to a line voltage of 120 V along the second site cable, and providing 120 V / 240 V and 200 A service to the second residential site.

17. The method of claim 16, comprising upgrading the service to 200 A by stepping down the grid voltage to 480 V along the first service cable bundle to provide 480 V and 100 A to the first residential site.

18. The method of claim 17, comprising adding an additional site transformer at the first residential site and using the additional site transformer to step down the 480 V and 100 A to a line voltage of 120 V along the first site cable, and providing 120 V / 240 V and 200 A service to the first residential site.

19. The method of claim 18, further comprising utilizing an existing site service access cable as the second service cable bundle to provide 480 V and 100 A for step-down at the second residential site.

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