Substation system

Abstract

The transformation system (1) includes: a PVT (11) having a primary winding (PW) that receives a primary voltage from a power line (PL) of a power system on the primary side, and a secondary winding (SW) that outputs a secondary voltage lower than the primary voltage on the secondary side; a first CT (13) that is located upstream of the PVT (11) and downstream of the power line (PL); and a second CT (21) that is located on a line connecting the primary ground side of the primary winding (PW) and the ground terminal.

Description

Technical Field

[0004]

[0001] One aspect of the present invention relates to a substation system.

Background Art

[0002] Regarding a substation system that converts the voltage supplied from a transmission line by a transformer, various configurations have been proposed. For example, in Non-Patent Document 1 below, it is disclosed that a PVT (power voltage transformer) is used as the transformer. A PVT is also referred to as an SSVT (station service voltage transformer).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a substation system, a plurality of CTs (Current Transformers) may be provided for the protection and monitoring of PVTs. Cost reduction of such a substation system is desired.

Means for Solving the Problems

[0005] A substation system according to one aspect of the present invention comprises a PVT having a primary winding that receives a primary voltage from a power transmission line of a power system on the primary side and a secondary winding that outputs a secondary voltage lower than the primary voltage on the secondary side; a first CT located upstream of the PVT and downstream of the power transmission line; and a second CT located on a line connecting the primary ground side of the primary winding and the ground terminal. [Effects of the Invention]

[0006] According to one aspect of the present invention, a power substation system that is less expensive than conventional systems can be realized. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram illustrating one example configuration of the substation system of Embodiment 1. [Figure 2] This is a diagram illustrating an example configuration of a comparative substation system. [Figure 3] This figure illustrates an example of the location of the primary grounding terminal in the substation system of Embodiment 1. [Figure 4] This figure shows an example configuration of the substation system according to Embodiment 2. [Figure 5] This figure shows another example configuration of the substation system of Embodiment 2. [Figure 6] This figure shows yet another configuration example of the substation system of Embodiment 2. [Figure 7] This figure shows yet another configuration example of the substation system of Embodiment 2. [Modes for carrying out the invention]

[0008] [Embodiment 1] The substation system 1 of Embodiment 1 is described below. For the sake of clarity, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals in subsequent embodiments, and their descriptions will not be repeated. For the sake of simplicity, known technical matters will also be omitted as appropriate. Each component, material, and numerical value described herein is merely an example unless otherwise specified. Therefore, for example, unless otherwise specified, the positional and connection relationships of each component are not limited to the examples in the figures. Also, the figures are not necessarily drawn to scale.

[0009] (Example configuration of substation system 1) Figure 1 is a diagram illustrating one example configuration of the substation system 1. Figure 1 schematically shows the substation system 1 and its surrounding configuration. Explanations of the components in Figure 1 that are not highly relevant to the content of Embodiment 1 are omitted. This also applies to subsequent figures.

[0010] As shown in Figure 1, the substation system 1 is connected to the transmission line PL in the power grid. For example, the transmission line PL may be an extra-high voltage transmission line. In Figure 1, a three-phase, three-wire transmission line PL is shown as an example. In Figure 1, a schematic single-line diagram of the substation system 1 connected to one phase (e.g., T phase) of the transmission line PL is shown.

[0011] The substation system 1 has a PVT 11. The PVT 11 is a power supply instrument transformer that is smaller than conventional power transformers, making it suitable for small substations such as micro substations. Therefore, Embodiment 1 illustrates a case where the substation system 1 is located inside a micro substation.

[0012] The PVT11 has a primary winding PW and a secondary winding SW. The primary winding PW is located on the primary side of the substation system 1. The primary winding PW receives the primary voltage from the transmission line PL. The turns ratio of the primary winding PW and the secondary winding SW is set so that the primary voltage can be converted to a secondary voltage lower than the primary voltage.

[0013] The secondary winding switch (SW) is located on the secondary side of the substation system 1. The secondary winding switch outputs a secondary voltage corresponding to the primary voltage. The secondary winding switch is connected to load equipment (not shown). In this way, the PVT 11 can convert the primary voltage (e.g., extra-high voltage) to a secondary voltage (e.g., low voltage) and supply the said secondary voltage to the load equipment.

[0014] Substation system 1 has a first CT13 and a second CT21. As described below, the roles of the first CT13 and the second CT21 are different.

[0015] The first CT13 is a current transformer (CT) used to detect the primary current flowing from the transmission line PL to the primary winding PW in order to protect the PVT11. Therefore, as shown in Figure 1, the first CT13 is located upstream of the PVT11 and downstream of the transmission line PL.

[0016] During a power system fault, a fault current (e.g., several hundred to tens of thousands of amperes) exceeding the rated value of the primary current (e.g., several tens of amperes) may flow through the primary winding PW. The current transformation ratio of the first CT13 is set to convert the primary current, which is the fault current, into a smaller current (e.g., several amperes) suitable for the protective relay. In this specification, the current obtained by the conversion of the primary current by the first CT13 is referred to as the protection judgment current.

[0017] The first CT13 supplies a protection judgment current to the protection relay. Based on the protection judgment current, the protection relay switches the connection state between the transmission line PL and the PVT11 (more specifically, the primary winding PW). In the example in Figure 1, a GCB (gas insulated circuit breaker) is located downstream of the first CT13 and upstream of the PVT11. Therefore, as an example, the protection relay may activate the GCB to disconnect the PVT11 from the transmission line PL when the protection judgment current exceeds a predetermined threshold. This protects the PVT11 from fault current. For these reasons, the first CT13 may also be called a protection CT or a high-current CT.

[0018] Unlike the first CT 13, the second CT 21 is a CT for measuring the primary current (e.g., generally 10 A or less) flowing during the normal operation of the power system. The current transformation ratio of the second CT 21 is set so that the primary current during normal operation can be converted into a smaller current suitable for another measuring instrument (e.g., a data logger). In this specification, the current obtained by converting the primary current by the second CT 21 is referred to as the measurement current. The second CT 21 supplies the measurement current to the measuring instrument. Thus, in the substation system 1, through the conversion by the second CT 21, the primary current during normal operation is monitored by the measuring instrument. From the above, the second CT 21 may be referred to as a measurement CT or a small-current CT.

[0019] The symbol N in FIG. 1 represents the terminal connected to the primary grounding side of the primary winding PW. In this specification, this terminal is referred to as the primary grounding side terminal. In the following description, N is used as the symbol for referring to the primary grounding side terminal. The primary grounding side of the primary winding PW may be drawn from the primary winding PW to the primary grounding side terminal N using an arbitrary lead wire (e.g., a neutral wire).

[0020] The symbol n in FIG. 1 represents the terminal connected to the secondary grounding side of the secondary winding SW. In this specification, mainly the primary grounding side of the primary winding PW and the primary grounding side terminal N are described, so no further description is given for the secondary grounding side of the secondary winding SW.

[0021] In a general substation system, the primary grounding side of the primary winding of the transformer is grounded. Therefore, in the example of FIG. 1, the primary grounding side terminal N is grounded via the grounding wire 15. And in the substation system 1, the second CT 21 is located on the line connecting the primary grounding side of the primary winding PW and the grounding terminal.

[0022] The first CT13 is subjected to a primary voltage, which is a high voltage supplied from the power transmission line PL in the power system. Therefore, the first CT13 must be a high-voltage CT capable of withstanding such a high voltage. Consequently, the cost of the first CT13 is relatively high. On the other hand, as will be described later, the second CT21 does not have to be a high-voltage CT. For example, the second CT21 may be a low-voltage CT (a CT with voltage resistance that is not sufficient to withstand the high voltage mentioned above).

[0023] (Comparative example) Figure 2 is a diagram illustrating an example configuration of substation system 1R as a comparative example. Figure 2 is a counterpart to Figure 1. Substation system 1R is an example of a conventional substation system. As shown in Figure 2, substation system 1R has a second CT12 instead of the second CT21 in Figure 1.

[0024] The second CT12, like the second CT21 in Figure 1, is a measuring CT (a CT used to measure the primary current flowing during normal operation of the power system). However, the second CT12 is located upstream of the PVT11 and downstream of the first CT13. In the example in Figure 2, the second CT12 is located upstream of the GCB.

[0025] In the substation system 1R shown in Figure 2, the primary voltage is also applied to the second CT12, which is located upstream of the PVT11. Therefore, in substation system 1R, a high-voltage CT must also be used for the second CT12. Consequently, the cost of the second CT12 is relatively high in substation system 1R.

[0026] Furthermore, since the second CT12 is a measuring CT, it generally has lower resistance to large currents compared to the first CT13, which is a protective CT. For this reason, in substation system 1R, if a fault occurs in the power grid and the fault current flows through the second CT12, there is a risk that the second CT12 may be damaged.

[0027] (Effects of Substation System 1) As described above, in the substation system 1 of Figure 1, unlike the substation system 1R of Figure 2, the second CT (second CT21 in the example of Figure 1) is located on the line connecting the primary ground side of the primary winding PW to the ground terminal.

[0028] Therefore, the primary current in substation system 1 is, Transmission line PL → Primary winding PW → 2nd CT21 → Earth The current flows in this order. In other words, according to the connection relationship of substation system 1, the path of the primary current can be set as described above. Therefore, the primary current flowing during normal operation of the power system can be measured by the second CT.

[0029] Therefore, in the substation system 1 shown in Figure 1, unlike the substation system 1R shown in Figure 2, the second CT does not need to be placed upstream of the PVT 11. As a result, in substation system 1, it is not necessary to use a high-voltage CT as the second CT. Consequently, it becomes possible to use a relatively inexpensive low-voltage CT as the second CT. As described above, substation system 1 can reduce the cost of a substation system having multiple CTs (e.g., a first CT and a second CT) compared to conventional systems.

[0030] Furthermore, in substation system 1, unlike substation system 1R in Figure 2, the second CT is located downstream of the GCB. Therefore, in substation system 1, the GCB can protect the second CT from fault current in the event of a fault in the power grid. Consequently, substation system 1 makes it possible to protect the second CT more safely than in conventional systems.

[0031] (supplement) The secondary current in substation system 1 (the current flowing through the secondary winding switch) is determined according to the power demand of the load equipment. Therefore, for example, the secondary current in substation system 1 may be determined according to the number of households to which power should be supplied by substation system 1.

[0032] Conventional large-scale power substations using power transformers are generally designed to supply electricity to large households (e.g., tens of thousands of households). On the other hand, micro-substations using PVTs are small-scale substations designed to complement large-scale substations, for example, in areas where power infrastructure is underdeveloped. Therefore, micro-substations using PVTs are generally designed to supply electricity to small households (e.g., a few hundred households).

[0033] Therefore, the secondary current in a micro substation is smaller than that in a large substation. As a result, the primary current in a micro substation is also smaller than that in a large substation. For example, as mentioned above, the primary current in a micro substation is generally 10A or less. On the other hand, the primary current in a large substation is several hundred A to tens of thousands of A. For this reason, micro substations require the use of current transformers (CTs) that can measure smaller primary currents compared to large substations.

[0034] According to the substation system 1, the second CT21 can be used as a CT capable of measuring smaller primary currents compared to large substations. In addition, the substation system 1 can also provide safer protection for the second CT21. For these reasons, the substation system 1 is suitable for micro-substations.

[0035] (Example of the location of the primary ground terminal) Next, referring to Figure 3, we will describe in more detail the location of the primary grounding terminal N in the substation system 1. Figure 3 is a diagram illustrating an example of the location of the primary grounding terminal N. In Figure 3, the internal structure of the PVT 11 and its surrounding configuration are schematically shown. In Figure 3, the various parts related to the secondary winding SW are omitted from the illustration.

[0036] As shown in Figure 3, the PVT11 may have an insulating container 30 and a terminal box 34. The insulating container 30 is an example of a container for the PVT11. The terminal box 34 is another example of a container for the PVT11. The primary ground terminal N may be located inside the container of the PVT11.

[0037] The insulating container 30 may be a sealed container. For example, if the PVT 11 is a gas-insulated type, the insulating container 30 is a pressure vessel containing insulating gas. For another example, if the PVT 11 is an oil-insulated type, the insulating container 30 may be a container containing insulating oil. Therefore, the insulating container 30 does not have to be a pressure vessel. The primary winding PW is located inside the insulating container 30. Reference numerals 31 and 32 in Figure 3 indicate the high-voltage side (transmission line side) and the primary ground side of the primary winding PW, respectively.

[0038] Unlike the insulating container 30, the terminal box 34 may be an open container. For example, the terminal box 34 may be a container with an openable portion. The terminal box 34 is a connection interface for connecting each part of the PVT 11 to parts other than the PVT 11 on the low-voltage side. The terminal box 34 may be provided with connection terminals for connecting a secondary winding switch (not shown) to load equipment.

[0039] As shown in Figure 3, the second CT21 may be located inside the terminal box 34. By positioning the second CT21 inside the terminal box 34, maintenance of the second CT21 becomes easier.

[0040] The primary ground terminal N may also be located inside the terminal box 34. In the example in Figure 3, the primary ground side 32 of the primary winding PW is led to the primary ground terminal N via a sealed terminal 33. By positioning the primary ground terminal N inside the terminal box 34, maintenance of the primary ground terminal N becomes easier. In addition, wiring work to connect the primary ground terminal N to the ground terminal also becomes easier.

[0041] However, as will be apparent to those skilled in the art, the position of the primary ground terminal N in Embodiment 1 is not limited to the example in Figure 3. For example, the primary ground terminal N in Embodiment 1 may be located inside the insulating container 30.

[0042] [Embodiment 2] In a substation system according to one aspect of the present invention, the primary ground side of the primary winding PW only needs to be connected to the second CT21. Therefore, for example, the positional relationship between the primary ground terminal N and the second CT21 is not limited to the example of Embodiment 1. Figure 4 is a diagram showing an example configuration of a substation system in Embodiment 2. Figure 4 is a diagram that corresponds to Figure 3. The substation system in Figure 4 is referred to as substation system 2.

[0043] As shown in Figure 4, the primary grounding terminal N may be located outside the container of the PVT11. In the example in Figure 4, the primary grounding terminal N may be covered by another non-sealed container. As shown in Figure 4, even when the primary grounding terminal N is located near the grounding terminal, the wiring work to connect the primary grounding terminal N to the grounding terminal is made easier.

[0044] Figure 5 shows another example of the substation system configuration in Embodiment 2. The substation system in Figure 5 is referred to as substation system 2A. In the example in Figure 5 as well, the primary grounding terminal N is located outside the container of the PVT 11. Substation system 2A has a PVT 11A instead of a PVT 11. Unlike the PVT 11, the PVT 11A does not have a terminal box 34. Thus, a PVT according to one aspect of the present invention does not necessarily have to have a terminal box. In the example in Figure 5, the primary grounding terminal N and the second CT 21 are located outside the container of the PVT 11.

[0045] Figure 6 shows yet another configuration example of the substation system in Embodiment 2. The substation system in Figure 6 is referred to as substation system 2B. Substation system 2B has a PVT 11. In the example in Figure 6, the primary grounding terminal N is located inside the terminal box 34. On the other hand, the second CT 21 is located outside the container of the PVT 11. Thus, even if the PVT according to one aspect of the present invention has a terminal box, the second CT 21 may be located outside the terminal box.

[0046] Figure 7 shows yet another configuration example of the substation system in Embodiment 2. The substation system in Figure 7 is referred to as substation system 2C. Substation system 2C has a PVT 11. In the example in Figure 7, the primary grounding terminal N is located inside the terminal box 34. On the other hand, the second CT 21 is located inside the insulating container 30.

[0047] [Variation] In the embodiments described above, through-type CTs are exemplified as each CT. However, as will be apparent to those skilled in the art, a CT according to one aspect of this disclosure may be a wound-type CT.

[0048] 〔summary〕 A substation system according to embodiment 1 of the present invention is a substation system comprising: a PVT having a primary winding that receives a primary voltage from a power transmission line of a power system on the primary side and a secondary winding that outputs a secondary voltage lower than the primary voltage on the secondary side; a first CT located upstream of the PVT and downstream of the power transmission line; and a second CT located on a line connecting the primary ground side of the primary winding and the ground terminal.

[0049] The substation system according to embodiment 2 of the present invention may be provided with a primary grounding terminal connected to the primary grounding side of the primary winding in embodiment 1, and the primary grounding terminal may be located inside the container of the PVT.

[0050] In the substation system according to aspect 3 of the present invention, in aspect 2, the PVT may be provided with a terminal box as the container, and the primary grounding terminal may be located inside the terminal box.

[0051] The substation system according to aspect 4 of the present invention may be provided with a primary grounding terminal connected to the primary grounding side of the primary winding in aspect 1, and the primary grounding terminal may be located outside the container of the PVT.

[0052] In the substation system according to aspect 5 of the present invention, in aspect 3 or 4, the PVT may be provided with a terminal box as the container, and the second CT may be located inside the terminal box.

[0053] The substation system according to aspect 6 of the present invention may be located inside a micro substation in any one of aspects 1 to 5 described above.

[0054] [Additional Notes] One aspect of the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of one aspect of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. [Explanation of Symbols]

[0055] Substation systems 1, 2, 2A, 2B, 2C 11 PVT 13 1st CT 21 2nd CT 30. Insulating containers (examples of PVT containers) 32 Primary ground side of the primary winding 34 Terminal box (another example of a PVT container) PW Primary Winding SW secondary winding N Primary ground terminal (terminal connected to the primary ground side of the primary winding) PL transmission lines

Claims

1. A PVT having a primary winding that receives a primary voltage from a power transmission line of the power system on the primary side, and a secondary winding that outputs a secondary voltage lower than the primary voltage on the secondary side, The first CT is located upstream of the above PVT and downstream of the above power transmission line, A substation system comprising a second current transformer (CT) located on a line connecting the primary ground side of the primary winding and the ground terminal.

2. It is equipped with a primary ground terminal connected to the primary ground side of the primary winding mentioned above. The substation system according to claim 1, wherein the primary grounding terminal is located inside the container of the PVT.

3. The above PVT is equipped with a terminal box as the above container, The substation system according to claim 2, wherein the primary grounding terminal is located inside the terminal box.

4. It is equipped with a primary ground terminal connected to the primary ground side of the primary winding mentioned above. The substation system according to claim 1, wherein the primary grounding terminal is located outside the container of the PVT.

5. The above PVT is equipped with a terminal box as the above container, The substation system according to claim 3 or 4, wherein the second CT is located inside the terminal box.

6. The substation system according to claim 1, located inside a micro substation.

Images