Current measurement system and power plant

Abstract

By ensuring an insulation distance of 20 mm or more from the electrical circuit inserted through the central opening of the main current transformer, we achieve "reduced workload and easier installation" as well as "space saving and strength assurance." [Solution] The current measurement system 1 installed in the electrical circuit has a main current transformer 2, an auxiliary current transformer 3, and a measuring instrument 4, and the insulation distance Z from the electrical circuit inserted through the central opening 2b of the main current transformer 2 is 20 mm or more. Two auxiliary coil members 3a that output current values ​​corresponding to the output from each main current transformer 2 attached to two of the three-phase three-wire electrical circuit are built into one auxiliary housing 3b, or the opening direction of the central opening 2b of the roughly rectangular main current transformer 2 and the insertion direction of the electrical circuit are roughly horizontal, or in a power plant 10 having a power generation unit 11, a conversion unit 12, a transformer 13, a load switch 14, and a control panel housing 15, the main current transformer 2 attached to the electrical circuit between the transformer 13 and the load switch 14 may be fixed in a suspended manner inside the control panel housing 15.

Description

Technical Field

[0001] The present invention relates to a current measurement system provided in an electric circuit and a power plant having such a current measurement system.

Background Art

[0002] Conventionally, a current control system for suppressing power consumption is known (see Patent Document 1). This current control system includes a circuit breaker for wiring to prevent overcurrent from flowing through a power load, current measurement means for measuring the current flowing through the power load, moving average current calculation means for calculating a moving average current value based on the measurement current measured by the current measurement means, average current comparison means for comparing the moving average current value calculated by the moving average current calculation means with a caution average current value set based on the tripping current value in the overcurrent operation characteristics of the circuit breaker for wiring, and partial stop signal generation means for stopping the operation of a part of the adjustable power load among the power loads. When the moving average current value exceeds the caution average current value, the partial stop signal generation means generates the partial stop signal, and based on the partial stop signal, a part of the adjustable power load is forcibly stopped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The current control system described in Patent Document 1 is shown in paragraph 0022, FIG. 1, etc. to be retrofitted to an existing switchboard such as a small or medium-sized factory or a small or medium-sized store. When retrofitting or the like, it is necessary to attach a current transformer for high voltage or the like to the power supply line from the system to the load (so-called main circuit). However, in the current control system described in Patent Document 1, installing the current transformer requires disconnecting the main circuit, stripping the insulation, and connecting the wires with soldering or terminals. Furthermore, the current transformer is heavy (for example, about 7 kg), resulting in a heavy workload.

[0005] Furthermore, in small and medium-sized factories and shops, there are many distribution boards of 300 kVA or less (so to speak, small distribution boards), and in some cases, power consumption can be reduced by retrofitting solar power generation equipment or reverse power relays to these distribution boards to control self-consumption. In this case, the reverse power relay operates based on the current value flowing through the main circuit, etc., and therefore it is necessary to install a high-voltage current transformer, etc., in the main circuit within a small distribution panel. However, there is insufficient space to install the current transformer within this distribution panel, and there is a risk that the mounting strength to the mounting frame of the current transformer may be insufficient.

[0006] In view of these points, the present invention aims to provide a current measurement system and power plant that can achieve "reduced workload" and "space saving and strength assurance" by setting the insulation distance from the electrical circuit to the central opening of the main current transformer installed in the electrical circuit to 20 mm or more. [Means for solving the problem]

[0007] The current measurement system 1 according to the present invention is a current measurement system installed in an electrical circuit, and the current measurement system comprises a main current transformer 2 attached to the electrical circuit, an auxiliary current transformer 3 that outputs a current value corresponding to the output from the main current transformer 2, and a measuring instrument 4 that measures at least the current value flowing through the electrical circuit based on the output from the auxiliary current transformer 3, wherein the main current transformer 2 comprises an annular coil member 2a, and the annular coil member 2a is provided with a central opening 2b that can secure a predetermined insulation distance Z with respect to the electrical circuit through which it is inserted, and the first feature is that the insulation distance Z is 20 mm or more.

[0008] A second feature of the current measurement system 1 according to the present invention is that, in addition to the first feature described above, the circuit is a three-phase, three-wire system, a main current transformer 2 is attached to each of the three wires of the circuit, the auxiliary current transformer 3 outputs a current value corresponding to the output from each of the main current transformers 2, the auxiliary current transformer 3 is equipped with two auxiliary coil members 3a that output current values ​​corresponding to the output from each of the main current transformers 2, and the two auxiliary coil members 3a are housed in a single auxiliary housing 3b.

[0009] A third feature of the current measurement system 1 according to the present invention is that, in addition to the first or second feature described above, the annular coil member 2a in the main current transformer 2 is substantially rectangular in shape, the central opening 2b in the substantially rectangular annular coil member 2a is also substantially rectangular in shape, and the substantially rectangular annular coil member 2a is attached to the circuit such that the opening direction of the central opening 2b is substantially horizontal, and the direction in which the circuit is inserted into the central opening 2b is also substantially horizontal.

[0010] The power plant 10 according to the present invention is a power plant having the current measurement system 1 described above, and the power plant comprises a power generation unit 11, a conversion unit 12 that converts a DC current or AC current from the power generation unit 11 into a low-voltage AC current L, a transformer 13 that can transform the low-voltage AC current L from the conversion unit 12 into a higher voltage AC current H, a load switch 14 provided between the transformer 13 and the system K, and a panel housing 15 that at least houses the load switch 14, wherein the main current transformer 2 is attached to the circuit between the transformer 13 and the load switch 14, and the substantially rectangular annular coil member 2a of the main current transformer 2 is fixed in a suspended manner inside the panel housing 15, which is its first feature.

[0011] These features allow the electrical circuit to be inserted through the central opening 2b of the main current transformer 2, and the insulation distance Z from the inserted circuit to be 20 mm or more. Unlike Patent Document 1, when installing the main current transformer 2 of the current measurement system 1 in an existing distribution board of 300 kVA or less, it is not necessary to cut the electrical circuit (main circuit, etc.), strip the insulation, or connect it with soldering or terminals. As a result, regardless of the weight of the main current transformer 2, the workload can be reduced ("reduced workload") and it can be said that this also leads to "easier installation." At the same time, even if the current flowing through the circuit is high voltage (for example, 6600V), a sufficient insulation distance Z is ensured between the circuit and the main current transformer 2. This suppresses the flow of large currents on the output side of the main current transformer 2, thereby reducing the risk of electric shock. Furthermore, by including not only the main current transformer 2 and measuring instrument 4 but also an auxiliary current transformer 3 as the current measurement system 1, it can be said that regardless of the output voltage of the main current transformer 2 and the input voltage of the measuring instrument 4, any configuration of the main current transformer 2 and measuring instrument 4 can be used by adjusting the auxiliary current transformer 3 (for example, the number of turns of the auxiliary coil member 3a).

[0012] Furthermore, by integrating the two auxiliary coil members 3a, which output current values ​​corresponding to the output from each main current transformer 2 attached to two of the three-phase three-wire circuit, into a single auxiliary housing 3b, the number of components to be handled during the installation of the current measurement system 1 into the circuit is reduced, thus further reducing the workload.

[0013] Furthermore, by making the annular coil member 2a of the main current transformer 2 roughly rectangular in shape, since panel enclosures such as distribution boards are usually composed of frame pipes and mounting frames that extend linearly in the vertical, horizontal, and height directions within a cubicle (box-shaped), it becomes possible to fix the roughly rectangular annular coil member 2a in contact with the end faces of these frame pipes, either with its end face (either the end face of the roughly rectangular annular coil member 2a itself or the end face of the main enclosure 2c), thereby ensuring sufficient mounting strength ("ensuring strength"). Simultaneously, in the roughly rectangular main current transformer 2, by making the direction of the opening of the central opening 2b roughly horizontal, and by making the direction in which the electrical circuit is inserted into the central opening 2b roughly horizontal, there are more parts and locations where the electrical circuit inside the enclosure of a panel such as a distribution board is normally routed roughly along the vertical, horizontal, and height directions (especially the vertical and horizontal directions) (in other words, there are more parts and locations where the main current transformer 2 can be installed), and the degree of freedom of installation is increased.

[0014] Furthermore, in the case where the main current transformer 2 is installed in the circuit between the transformer 13 and the load switch 14 inside the panel enclosure 15 (i.e., the circuit on the load side of the load switch 14), and the reverse power relay is activated based on the output from the main current transformer 2, compared to the case where the main current transformer 2 is installed in the circuit on the system K side of the load switch 14, the generation of reverse power can be detected at a position further away from system K, and as soon as detection occurs, the reverse power relay can interrupt or disconnect the circuit with a predetermined circuit breaker, thereby further reducing the possibility of reverse power flowing to system K. Simultaneously, by suspending and fixing the annular coil member 2a of the main current transformer 2 within the panel enclosure 15, there is a space that originally exists below the frame pipes that constitute the panel enclosure 15 and extend in a substantially horizontal direction. By installing the main current transformer 2 in this space, space efficiency is increased, and it can be said that "space saving" can be achieved within the panel enclosure 15. [Effects of the Invention]

[0015] According to the current measurement system and power plant of the present invention, by setting the insulation distance from the circuit to the central opening of the main current transformer installed in the circuit to 20 mm or more, it is possible to achieve "reduced workload" and "space saving and strength assurance". [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram illustrating the current measurement system according to the present invention. [Figure 2]A drawing substitute photograph showing the main current transformer in the current measurement system, where (a) shows the top perspective and (b) shows the bottom perspective. [Figure 3] A drawing substitute photograph showing an example of mounting the main current transformer in the current measurement system. [Figure 4] A schematic diagram showing the test configuration of the current measurement system, where (a) is the test configuration when the input is 100%, 20%, 5%, etc., and (b) is the test configuration when the input is 0.2%, etc. [Figure 5] A schematic diagram showing the current measurement system according to the present invention and a power plant.

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. <Overall Configuration of Current Measurement System 1> In FIGS. 1 to 5, a current measurement system 1 according to the present invention is shown. This current measurement system 1 is a device provided in the electric circuit D and has a main current transformer 2, an auxiliary current transformer 3, and a measuring instrument 4, which will be described later. Furthermore, the current measurement system 1 may have a measurement unit 4a, a relay unit 4b, and a measurement housing 4c, which will be described later, and may also have electric circuits (primary-secondary sensor circuit 1a and secondary-tertiary sensor circuit 1b) connecting between the main current transformer 2 and the auxiliary current transformer 3 or between the auxiliary current transformer 3 and the measuring instrument 4. Note that the primary-secondary sensor circuit 1a may be grounded, and terminals may be provided at the tips of the primary-secondary sensor circuit 1a and the secondary-tertiary sensor circuit 1b. Such a current measurement system 1 may be provided for the electric circuit D simultaneously with the manufacture of a power plant 10 or a switchboard to be described later, or may be retrofitted to an existing power plant 10 or switchboard (even provided after the manufacture of 0 in the power plant 10 or switchboard). There are no particular limitations on the power supply of the current measurement system 1 either, but it may be shared with the voltage of the electric circuit D as the measurement target described above (that is, 110V, 220V, 440V of 60Hz or 50Hz, or 100V or more and 200V or less), or it may be 100V or 110V of direct current.

[0018] In addition, the "electric circuit D" and other electric circuits in the present invention are those that conduct electricity (current), including conductors such as copper, aluminum, silver, gold, nichrome, etc., cables in which these conductors are covered with insulators, general electric wires, conducting wires, and the like. If this electric circuit D is three-phase three-wire (3φ3W), single-phase three-wire (1φ3W), etc., it will be in a set of three, and if it is single-phase two-wire (1φ2W), etc., it will be in a set of two. Depending on the power distribution method (power transmission method) of the electric circuit D, a plurality of wires may be grouped as one set. Hereinafter, the electric circuit D will be mainly described as being three-phase three-wire. Such an electric circuit D includes a high-voltage circuit 16H described later, which is the main circuit, and the current measurement system 1 may be provided in the high-voltage circuit 16H or the like.

[0019] Here, the current, voltage, power, and capacity in the present invention may be values within the rated range. In this case, they can be referred to as rated current, rated voltage, rated power, and rated capacity. These rated currents, etc. can also be said to be the limit values of currents, etc. compensated by the manufacturer for the safe use of electrical products. Furthermore, the rated value can also be said to be the usage limit and conditions under which safe and proper operation is guaranteed for equipment and devices. When the current in the present invention is alternating current, the value of the current (current value), the value of the voltage (voltage value), the value of the power (power value), and the value of the capacity (capacity value) may be effective values.

[0020] Furthermore, there are no particular limitations on the voltage value of the current flowing through circuit D. For example, it may be an extra-high voltage value (also called extra-high voltage, such as 22,000V, 33,000V, 77,000V, etc., voltage values ​​exceeding 7,000V), or a high voltage value (if the current is AC, a voltage value exceeding 600V and not exceeding 7,000V (such as 6,600V), and if the current is DC, a voltage value exceeding 750V and not exceeding 7,000V), or a low voltage value (if the current is AC, a voltage value of 600V or less, and if the current is DC, a voltage value of 750V or less).

[0021] <Main Current Transformer 2> As shown in Figures 1-5, the main current transformer 2 is a current transformer (CT) installed in the aforementioned circuit D, and is a device that detects the current in circuit D, and can be said to have a current detection function. Furthermore, the main current transformer 2 can also be called the main CT or primary CT. The main current transformer 2 is equipped with an annular coil member 2a, which will be described later, and a central opening 2b, which will be described later, and a distance (insulation distance Z) is secured from the electrical circuit D inserted through the central opening 2b to the central opening 2b (particularly its inner circumferential surface (inner end surface)). In addition, the main current transformer 2 may also include a main housing 2c that has an annular coil member 2a inside (built in). Such a main current transformer 2 may exist as a single unit in a current measurement system 1, but it may also exist as a unit of two or more units. Hereafter, we will assume that there are mainly two main current transformers 2 in one current measurement system 1, and that when the aforementioned circuit D is a three-phase three-wire system, each main current transformer 2 is attached to two of the three wires.

[0022] The main current transformer 2 can be of any configuration as long as it can detect the current in the predetermined circuit D. For example, it can be a fluxgate type (open-loop or closed-loop type), a Hall element type (open-loop or closed-loop type), a CT (Current Transformer) type, or a Rogowski coil type. Furthermore, the main current transformer 2 may be a switchable type that can be installed to the aforementioned circuit D without cutting, stripping, soldering, or otherwise connecting the circuit D, and without removing terminals or connecting components in the circuit D, but it does not have to be a switchable type. The main current transformer 2 is not particularly limited as long as it can detect current, but it can be electronic, mechanical, three-phase (a system that detects two phases out of three wires), or single-phase.

[0023] Furthermore, there are no particular limitations on the current transformation ratio of the main current transformer 2 between the primary side (circuit D side) and the secondary side (output from main current transformer 2 (auxiliary current transformer 3) side). For example, the minimum value may be 10:1 or 100:1, and the maximum value may be 5000:1 or 20000:1 (1500:1 or 15000:1, etc.). In other words, if the current transformation ratio between the primary and secondary sides of the main current transformer 2 is 1500:1, even if the current flowing through the circuit D being measured is very large, for example, 1500A, the current output from the main current transformer 2 will be approximately 1A (1000mA). Conversely, if the current transformation ratio between the primary and secondary sides of the main current transformer 2 is 15000:1, even if the current flowing through the circuit D being measured is very large, for example, 1500A, the current output from the main current transformer 2 will be approximately 0.1A (100mA). Furthermore, there are no particular limitations on the rated range (detectable range) of the main current transformer 2. For example, it may be 15A or more and 1800A or less, preferably 20A or more and 1650A or less, and even more preferably 25A or more and 1500A or less. Other ranges such as 0.1A or more and 5.0A or 1A or more and 50A or less are also acceptable. Furthermore, the maximum value of the current actually flowing through the main current transformer 2 may be 10 to 20 times the maximum value of the current rating range mentioned above (for example, 40,000A, 36,000A, 30,000A, etc.), and the minimum value of the current actually flowing through the co-main current transformer 2 may be 0A.

[0024] <Annular coil member 2a, central opening 2b> As shown in Figures 1-5, the annular coil member 2a is part of the main current transformer 2 described above, and is an annular coil member with a central opening 2b, which will be described later, located approximately in the center of it. The annular coil member 2a is not particularly limited in shape or configuration, but may be, for example, roughly rectangular (roughly rectangular or roughly square), or it may be roughly circular, roughly elliptical, or roughly track-shaped (with a rectangular section between two semicircular sections). Furthermore, the central opening 2b may be roughly rectangular, or it may be roughly circular, roughly elliptical, roughly track-shaped, or other shapes. Furthermore, the shapes (types) of the annular coil member 2a and the central opening 2b may be approximately the same (approximately similar), but they may also be different (for example, the annular coil member 2a may be approximately rectangular and the central opening 2b may be approximately square). Hereafter, the annular coil member 2a will be described assuming that it is mainly roughly rectangular (or similar), and the central opening 2b will be described assuming that it is mainly roughly rectangular (or similar, or similar).

[0025] The roughly rectangular annular coil member 2a may be roughly rectangular in shape (i.e., roughly rectangular) in plan view, having a pair of roughly parallel and opposing long sides and a pair of roughly parallel and opposing short sides, or it may be roughly rectangular in shape (i.e., roughly square) in plan view, having four sides of equal length (and two pairs of opposing sides). The roughly rectangular annular coil member 2a may have windings wound only around its edges (i.e., the sides), or it may have windings wound across both the corners and the sides, or windings wound only around the corners. When a roughly rectangular annular coil member 2a has windings around its edges, the windings may be wound around each of the four opposing pairs of edges, or around two adjacent edges, all four edges, any three edges, or any one edge. Hereafter, we will assume that the roughly rectangular annular coil member 2a has windings wound around each of its opposing pairs of sides (that is, there are two windings wound around one roughly rectangular annular coil member 2a). From these two wound wires, one end and the other end (so to speak, the beginning and end of the winding) may protrude as lead wires, etc. Alternatively, the ends of each winding may be connected to each other or to each other (or one end to the other) with screws or the like to create electrical conductivity, thereby connecting the two wound wires in series. Each of the two wound wires connected in series may have a connecting terminal, such as a round or open-ended type, at the end that is not connected to the other, and these connecting terminals may be color-coded, for example, red and blue.

[0026] There are no particular limitations on the material of the winding in the roughly rectangular annular coil member 2a. For example, the winding can be considered an electric wire, and its material can be any material or wire type that can conduct electricity, such as polyurethane copper wire (UEW), polyester copper wire (PEW), polyamide-imide copper wire (AIW), nichrome wire, silver, gold, aluminum, etc. Furthermore, the diameter of the winding wire is not particularly limited, but it may be 0.1 mm or more and 10.0 mm or less, preferably 0.2 mm or more and 5.0 mm or less, and even more preferably 0.3 mm or more and 1.0 mm or less (such as 0.6 mm). There are no particular limitations on the number of times such a winding is made (number of turns), but for example, the upper limit may be 50,000 turns or less, preferably 25,000 turns or less, more preferably 10,000 turns or less, and even more preferably 2,000 turns or less, while the lower limit may be 10 turns or more, preferably 100 turns or more, more preferably 300 turns or more, and even more preferably 500 turns or more (such as 1,500 turns, 1,000 turns, 750 turns, etc.). The upper and lower limits for the number of turns of the winding described above can be combined with each other, for example, between 10 and 50,000 turns, or between 300 and 2,000 turns.

[0027] Furthermore, if multiple windings are provided around a single roughly rectangular annular coil member 2a, the number of turns for each winding may be the same or different. Furthermore, with respect to the number of turns of the windings in the roughly rectangular annular coil member 2a (if there is one wound winding, it is the number of turns of that winding; if there are multiple wound windings, it is the total number of turns of those multiple windings), the predetermined circuit D that is the subject of measurement can be said to have 1 turn. Therefore, the current transformation ratio of the primary side (the predetermined circuit D side) and the secondary side (the output from the main current transformer 2 (primary-secondary sensor circuit 1a) side) of the main current transformer 2 is 1: the number of turns of the windings in the roughly rectangular annular coil member 2a (i.e., 1: the number of turns of the windings in the roughly rectangular annular coil member 2a) with respect to the number of turns of the predetermined circuit D, which is 1. Such a roughly rectangular annular coil member 2a may have two roughly U-shaped cores (not shown), and may also be equipped with a coil bobbin (not shown), a fixing device (not shown), etc. Furthermore, the roughly rectangular annular coil member 2a may have only one roughly rectangular core, and it may not have a coil bobbin (i.e., the winding is directly wound around the roughly rectangular annular coil member 2a), nor may it have fasteners or the like.

[0028] Furthermore, the core material may be silicon steel such as grain-oriented silicon steel or ultrathin silicon steel, electrical steel, dust materials such as iron dust, Sendust, or Permalloy, ferrite, amorphous materials, or Finemet (registered trademark). Furthermore, there are no particular limitations on the material of the coil bobbin, but it may be made of engineering plastics such as polyacetal or polycarbonate, or synthetic resins such as silicon resin or nylon (polyamide), or other materials such as fiber-reinforced plastic, ceramics, or wood. Furthermore, the fastener is not particularly limited in its configuration, but may be, for example, a cable tie. If the shape and area of ​​the opening inside the coil bobbin are substantially the same as the cross-sectional shape and area of ​​the core (in other words, the core fits tightly into the coil bobbin), then the coil bobbin can also be said to be a fastener.

[0029] The main housing 2c (so to speak, a casing, which can also be described as roughly rectangular) incorporating such a roughly rectangular annular coil member 2a is not particularly limited in terms of its external dimensions (length, width, and height), the size of the central opening 2b, or its weight. For example, the external dimensions could be such that the vertical length (for example, the length in the shorter direction) is 70 mm or more and 230 mm or less, preferably 90 mm or more and 200 mm or less, and more preferably 110 mm or more and 170 mm or less (e.g., 136.5 mm), the horizontal length (for example, the length in the longer direction) is 70 mm or more and 250 mm or less, preferably 100 mm or more and 220 mm or less, more preferably 130 mm or more and 190 mm or less (e.g., 160 mm), and the height (thickness or length in the vertical direction) is 1 mm or more and 50 mm or less, preferably 3 mm or more and 40 mm or less, and more preferably 5 mm or more and 30 mm or less. Furthermore, the size of the central opening 2b may be, for example, 60 mm to 190 mm, preferably 75 mm to 160 mm, and even more preferably 90 mm to 130 mm (such as 105 mm), provided that the length and width are both approximately the same (i.e., the central opening 2b is approximately square). Furthermore, the total weight of the main housing 2c, which incorporates the roughly rectangular annular coil member 2a, may be, for example, 0.5 kg or more and 1.7 kg or less, preferably 0.6 kg or more and 1.4 kg or less, and even more preferably 0.7 kg or more and 1.1 kg or less (such as 0.8 kg).

[0030] Furthermore, there are no particular limitations on the configuration of the main enclosure 2c. For example, a roughly rectangular annular coil member 2a may be placed in the lower part of the enclosure, the enclosure lid may cover the roughly rectangular annular coil member 2a (placing a lid on top), and the enclosure lid may be fixed with fasteners such as screws or bolts. In this case, fixing holes (screw holes, bolt holes, etc.) may be provided at the four corners of the roughly rectangular main enclosure 2c. Furthermore, the fixing holes may be through holes. In this case, screws or bolts may not only fix the enclosure lid to the lower part of the enclosure, but also fix the entire main enclosure 2c containing the roughly rectangular annular coil member 2a to the panel enclosure 15 (especially the frame pipe 15a or mounting frame 15b, etc.) described later. Here, there are no particular limitations on the vertical and horizontal spacing of the fixing holes, but for example, the vertical length (for example, the length in the shorter direction) may be 55 mm or more and 215 mm or less, preferably 75 mm or more and 185 mm or less, and more preferably 95 mm or more and 155 mm or less (e.g., 121.5 mm), and the horizontal length (for example, the length in the longer direction) may be 60 mm or more and 240 mm or less, preferably 90 mm or more and 210 mm or less, and more preferably 120 mm or more and 180 mm or less (e.g., 148 mm). Furthermore, while there may be only one annular coil member 2a in a single main housing 2c, there may also be two or three or more. Hereafter, we will assume that there is mainly one annular coil member 2a in each main housing 2c.

[0031] <Insulation distance Z> As shown in Figures 1 and 3, the insulation distance Z is the distance from the inner surface of the central opening 2b in the main current transformer 2 (the inner surface of the main housing 2c) to the electrical circuit D inserted through this central opening 2b. The insulation distance Z may be 20 mm or more, and to elaborate further, the lower limit may be 20 mm or more, preferably 25 mm or more, more preferably 30 mm or more, and even more preferably 35 mm or more (such as 20 mm or 30 mm). Furthermore, there are no particular limitations on the upper limit of the insulation distance Z, but it may be, for example, 100 mm or less, preferably 80 mm or less, and even more preferably 60 mm or less. The lower limits of this insulation distance Z may also be combined with any of the upper limits. Furthermore, if the annular coil member 2a of the main current transformer 2 is approximately rectangular in shape, there will be four inner surfaces of its central opening 2b, both vertically and horizontally. The distances from each of these four inner surfaces to the electrical circuit D are all insulation distances Z, and each of these insulation distances Z is 20 mm or more. This is also true when the annular coil member 2a has a shape other than a roughly circular shape. If the central opening 2b is roughly circular, the distance from its inner surface to the electrical circuit D in the circumferential direction is all the insulation distance Z, and all of these insulation distances Z are 20 mm or more.

[0032] <Auxiliary current transformer 3> As shown in Figures 1, 4, and 5, the auxiliary current transformer 3 is a current transformer (CT) that outputs a current value corresponding to the output from the main current transformer 2 described above. It is a device that detects the current in the primary-secondary sensor circuit 1a through which the output current from the main current transformer 2 flows, and can be said to have a current detection function. Furthermore, the auxiliary current transformer 3 can also be said to be an auxiliary CT. The auxiliary current transformer 3 includes an auxiliary coil member 3a (described later) and an auxiliary housing 3b (described later). Such an auxiliary current transformer 3 may exist as a single unit in a current measurement system 1, but it may also exist as a unit of two or more units. In the following description, we will assume that there is mainly one auxiliary current transformer 3 in one current measurement system 1, but mainly two auxiliary coil members 3a in one current measurement system 1.

[0033] The auxiliary current transformer 3 can be of any configuration as long as it can detect the output current in the primary-secondary sensor circuit 1a from the main current transformer 2. For example, it can be a fluxgate type (open-loop or closed-loop type), a Hall element type (open-loop or closed-loop type), a CT (Current Transformer) type, or a Rogowski coil type. Furthermore, the auxiliary current transformer 3 may be of the switching type, but it does not have to be of the switching type, with respect to the aforementioned primary-secondary sensor circuit 1a. The auxiliary current transformer 3 is not particularly limited as long as it can detect current, but it can be electronic, mechanical, three-phase (a method that detects two phases out of three wires), or single-phase, for example.

[0034] Furthermore, there are no particular limitations on the current transformation ratio of the auxiliary current transformer 3 between the secondary side (sensor circuit 1a side between primary and secondary) and the tertiary side (sensor circuit 1b (measuring instrument 4) side between secondary and tertiary). For example, the minimum value may be 2:1 or 3:1, and the maximum value may be 20:1 or 50:1 (12:1 or 8:1, etc.). In other words, if the current transformation ratio between the secondary and tertiary sides of the auxiliary current transformer 3 is 12:1, and as described above, the current transformation ratio between the primary and secondary sides of the main current transformer 2 is 15000:1, then even if the current value flowing through the circuit D (to which the main current transformer 2 is installed) is very large, for example, 1500A, the current value output from the main current transformer 2 will be approximately 1A (1000mA) and will flow into the primary-secondary sensor circuit 1a. The current value output from the auxiliary current transformer 3 to the secondary-tertiary sensor circuit 1b via this current value will be approximately 0.083...A (83.3...mA), etc. This is true even if the current value flowing through the circuit D being measured is a different value. If the current value flowing through the circuit D being measured is 30A, the current value output from the main current transformer 2 will be approximately 0.02A (20mA), etc., and will flow into the primary-secondary sensor circuit 1a. After passing through this current value, the current value output from the auxiliary current transformer 3 to the secondary-tertiary sensor circuit 1b will be approximately 0.00166...A (1.66...mA), etc. Furthermore, there are no particular limitations on the rated range (detectable range) of the auxiliary current transformer 3. For example, it may be 0.010A (10mA) or more and 1.200A (1200mA) or less, preferably 0.013A (13mA) or more and 1.100A (1100mA) or less, and even more preferably 0.016A (16mA) or more and 1.000A (1000mA) or less. Other acceptable ranges include 0.00006A (0.06mA) or more and 0.00333A (3.33mA) or 0.00066A (0.66mA) or more and 0.03333A (33.33mA) or less.

[0035] <Auxiliary coil member 3a, auxiliary housing 3b> As shown in Figure 1, the auxiliary coil member 3a is part of the auxiliary current transformer 3 described above, and is a coil member. Such auxiliary coil members 3a are not particularly limited in shape or configuration, but for example, they may be roughly circular, or they may be rectangular (roughly rectangular or roughly square), roughly elliptical, roughly track-shaped, etc. Hereinafter, the auxiliary coil member 3a will be assumed to be mainly of a roughly circular shape. The differences between this roughly circular auxiliary coil member 3a and the roughly rectangular annular coil member 2a described above are not only its shape (plan view), but also the presence or absence of a core, the number of turns, and the number of auxiliary coil portions 3a in one auxiliary housing 3b. We will begin by describing these differences.

[0036] The roughly circular auxiliary coil member 3a is roughly circular (roughly ring-shaped or roughly annular) in a plan view, and can also be described as roughly circular in shape. To elaborate on the plan view shape of the roughly circular auxiliary coil member 3a, it may be strictly circular in plan view, or it may be slightly elliptical in plan view. The roughly circular auxiliary coil member 3a may or may not have a core, and if it has a core, it may have one or more cores, and may also be equipped with a coil bobbin, fixing device, etc. In the following description, the roughly circular auxiliary coil member 3a will be described primarily as having no core.

[0037] The auxiliary coil member 3a, which is roughly circular in shape and does not have a core, is, in other words, simply a winding made by winding wire in a roughly circular shape. There are no particular limitations on the number of turns (windings) in this manner, but for example, the number of turns of the auxiliary coil member 3a may be less than the number of turns of the annular coil member 2a described above. For example, the upper limit may be 50 turns or less, preferably 40 turns or less, and even more preferably 30 turns or less, and the lower limit may be 2 turns or more, preferably 3 turns or more, and even more preferably 5 turns or more (such as 12 turns or 8 turns). The upper and lower limits for the number of turns of the winding described above can be combined with each other, for example, between 2 and 50 turns, or between 5 and 30 turns. The input primary-secondary sensor circuit 1a may be wound around such a roughly circular auxiliary coil member 3a that does not have a core, and there are no particular limitations on the number of times it is wound; for example, it may be once or two or more times. However, if the number of turns of the primary-secondary sensor circuit 1a is, for example, 2, then the current transformation ratio of the secondary side (primary-secondary sensor circuit 1a side) and the tertiary side (output from auxiliary current transformer 33 (primary-tertiary sensor circuit 1b) side) of the auxiliary current transformer 3 will be 2 turns for the number of turns of the primary-secondary sensor circuit 1a, and the number of turns of the winding in the auxiliary coil member 3a, such as a roughly circular type without a core (i.e., 2: number of turns of the winding in the auxiliary coil member 3a, such as a roughly circular type without a core), meaning that half of the number of turns of the winding in the auxiliary coil member 3a, such as a roughly circular type without a core, is wasted. Therefore, the following description assumes that the number of turns (windings) of the input primary-secondary sensor circuit 1a around the auxiliary coil member 3a, such as a roughly circular type without a core, is 1.

[0038] The auxiliary coil member 3a described above may be built into one auxiliary housing 3b, or it may be built into two or three or more (see Figure 1). In the following description, the auxiliary coil member 3a will be described as being built into a single auxiliary housing 3b, mainly in pairs, unlike the main current transformer 2 described above. The auxiliary housing 3b (so to speak, the casing) incorporating such an auxiliary coil member 3a is not particularly limited in shape or size (length, width, and height). For example, its shape may be roughly rectangular or cubic, or it may be roughly cylindrical, ellipsoidal, or spherical. Hereafter, the auxiliary enclosure 3b will be described assuming that it is mainly in the shape of a roughly rectangular parallelepiped. The dimensions of the auxiliary housing 3b, which is roughly rectangular in shape, may be, for example, a vertical length (e.g., length in the shorter direction) of 10 mm or more and 100 mm or less, preferably 20 mm or more and 80 mm or less, more preferably 30 mm or more and 60 mm or less (e.g., 40 mm), a horizontal length (e.g., length in the longer direction) of 40 mm or more and 130 mm or less, preferably 50 mm or more and 110 mm or less, more preferably 60 mm or more and 90 mm or less (e.g., 70 mm), and a height (thickness or length in the vertical direction) of 5 mm or more and 60 mm or less, preferably 10 mm or more and 50 mm or less, more preferably 20 mm or more and 40 mm or less (e.g., 30 mm).

[0039] Furthermore, there are no particular limitations on the configuration of the auxiliary housing 3b. For example, if one auxiliary housing 3b contains two auxiliary coil sections 3a, then for each auxiliary coil section 3a, two sensor circuits (1st-2nd sensor circuits) 1a are connected to the secondary side (i.e., the main current transformer 2 side), and two sensor circuits (2nd-3rd sensor circuits) 1b are connected to the tertiary side (i.e., the measuring instrument 4 side). As a result, a total of four sensor circuits 1a and 1b are connected to the two auxiliary coil sections 3a, totaling eight sensor circuits 1a and 1b. These eight sensor circuits 1a and 1b (e.g., conductors or cords) may extend from the inside to the outside at one end of the auxiliary housing 3b (see Figure 1). Here, these eight sensor circuits 1a and 1b may be color-coded. For example, in the three-phase three-wire circuit D, the primary-to-secondary sensor circuit 1a from the main current transformer 2 attached to the R phase may be colored red and white, and the primary-to-secondary sensor circuit 1a from the main current transformer 2 attached to the T phase may be colored blue and green. Also, the secondary-to-tertiary sensor circuit 1b to the measuring instrument 4 may be colored in a different color than the four colors mentioned above. Furthermore, the auxiliary housing 3b may have mounting pieces 3c that protrude outward from end faces such as the lower side of the sensor circuits 1a and 1b described above, and fixing holes (such as screw holes or bolt holes) for fixing with fixing means such as screws or bolts may be provided at the corners of these mounting pieces 3c. Furthermore, there are no particular limitations on the materials used for the windings and other components of the auxiliary coil member 3a, nor its diameter; however, it may be the same as or different from the annular coil member 2a described above.

[0040] <Measuring instrument 4> As shown in Figures 1, 4, and 5, the measuring instrument 4 is a device that measures at least the current value flowing through the circuit D based on the output from the auxiliary current transformer 3 described above. The measuring instrument 4 may have a measuring unit 4a (described later), a relay unit 4b (described later), or a measuring housing 4c (described later). In addition, the measuring instrument 4 may also include a correction unit 4d that corrects the value of the current in the circuit D measured by the measuring unit 4a based on the current output from the auxiliary current transformer 3. The measuring instrument 4 may also have an output unit (not shown) that digitizes the output current from the auxiliary current transformer 3 described above and outputs it to the measuring unit 4a described later, or to the control unit of the power plant 10 described later, either via a wired connection using a communication cable or wirelessly. The measuring instrument 4 may have any of the following values ​​for the detection interval by the main current transformer 2 described above, or the output interval (communication speed) of the output unit described above. For example, the output interval may be 0.1 seconds or less, 0.05 seconds to 2.00 seconds, 0.75 seconds to 1.50 seconds, or 0.10 seconds to 1.00 seconds (such as 0.1 seconds).

[0041] <Measurement unit 4a> As shown in Figure 1, the measurement unit 4a is the part that measures at least the value of the current in a predetermined circuit D based on the current output from the auxiliary current transformer 3 via the secondary-tertiary sensor circuit 1b. The measurement unit 4a may be built into (or provided within) the measurement housing 4c, which will be described later. The measurement unit 4a is not particularly limited in its configuration, but for example, it may include an A / D converter, a CPU (central processing unit) that calculates and processes the value of the current output from the main current transformer 2 via the auxiliary current transformer 3 and after A / D conversion, memory, and an LCD (liquid crystal display) described later. In addition, the measurement unit 4a may also include another auxiliary CT between the auxiliary current transformer 3 and the A / D converter or CPU. In addition, the measuring unit 4a measures at least the value of the current in the circuit D. However, if the measuring unit 4a is also connected to the low-voltage side of an instrument transformer in the power plant 10 or a switchboard (described later), it may also measure the voltage and power values ​​in a predetermined circuit D, or measure reactive power, power factor, energy, reactive energy, etc. In addition, the measurement unit 4a may also measure the frequency of the alternating current at a predetermined power level, or the zero-sequence current.

[0042] <Relay section 4b> As shown in Figure 1, the relay unit 4b is the part that performs relay operations according to the value (value such as current value) in a predetermined circuit D measured by the measurement unit 4a described above. If the measuring instrument 4 has a relay unit 4b, it can be said that it has a relay function. Here, in the present invention, "according to the value in the predetermined circuit D measured by the measuring unit 4a" means that when the measured current, etc., becomes greater than or equal to a predetermined value (threshold) (exceeds the threshold) or becomes less than or equal to a predetermined value (threshold) (falls below the threshold), the relay operation described later will be performed. Furthermore, the threshold value, such as the current value, may be, for example, a power value such as reverse power (in this case, the computer 4 having the relay unit 4b can also be said to be a reverse power relay (RPR)) or a voltage value such as ground fault overvoltage (in this case, the computer 4 having the relay unit 4b can also be said to be an over voltage ground relay (OVGR)). In other words, it may be not only current values ​​such as overcurrent, instantaneous overcurrent, and ground fault overcurrent, but also other values ​​such as voltage values ​​such as undervoltage, or frequency values. Furthermore, "according to the value in the predetermined circuit D measured by the measurement unit 4a" includes not only cases where the relay operation described later is performed immediately after the measured current value or other value exceeds a predetermined value (threshold), but also cases where the next relay operation is performed after a predetermined time has elapsed.

[0043] Furthermore, the specified time may be 0.1 seconds or more and 15.0 seconds or 0.2 seconds or more and 5.0 seconds or more, 0.5 seconds or more, or 3.0 seconds or more (such as 2.0 seconds) after the threshold is exceeded or fallen below the threshold (that is, if 2.0 seconds or so have elapsed after the threshold is exceeded, the relay operation described later may be performed). In addition, this specified time may be adjustable in 0.1-second steps (0.0 seconds, 0.1 seconds, 0.2 seconds...15.0 seconds) from 0.0 seconds to 15.0 seconds. Furthermore, in the present invention, "relay operation" means, for example, in the power plant 10 described later, an operation to interrupt the circuit from the power generation unit 12 to the system K via a signal using any circuit breaker or load switch 14 described later, or, if the power generation unit 11 has a power conditioner (a power conditioner that converts DC current or AC current to AC current), stopping the conversion of said power conditioner. The signals from the relay unit 4b may include, in addition to the "trip" signal (a signal to interrupt the circuit) to the circuit breaker mentioned above, an "on" signal (a signal to turn the circuit breaker itself ON), an "off" signal (a signal to turn the circuit breaker itself OFF), and a signal to release the interruption of a predetermined circuit D. Furthermore, the signal from relay unit 4b may include a signal to stop the conversion of the power conditioner or a signal to start the conversion of the power conditioner. The relay unit 4b is not particularly limited in its configuration, but may be a contact-type (electromagnetic) relay using an electromagnet, or a contactless relay using a semiconductor element. Furthermore, if it is an electromagnetic relay, it may be a make-type (a-contact that closes when current is passed through the electromagnet), a break-type (b-contact that opens when current is passed through the electromagnet), a transfer-type (c-contact that switches multiple contacts by passing current through the electromagnet), a ratchet-type (which switches the opening and closing of the contacts each time current is passed through the electromagnet), or any other type of polarized relay with a permanent magnet in parallel with the electromagnet. Such relay units 4b may exist as one (one element) in a single measuring instrument 4, but they may also exist as multiple (multiple elements).

[0044] <Measurement enclosure 4c> As shown in Figures 1, 4, and 5, the measurement housing 4c is a housing that incorporates at least the measurement unit 4a described above. Furthermore, the measuring housing 4c can be said to be a measuring housing 4c when the measuring instrument 4 has a measuring unit 4a but no relay unit 4b, but it can also be said to be a measuring relay housing 4c when the measuring instrument 4 has both a measuring unit 4a and a relay unit 4b. The measurement housing 4c may be equipped with a display unit (not shown), such as an LCD (liquid crystal display), that is visible from the outside and displays values ​​such as the current value measured by the measurement unit 4a described above. This display unit may also be equipped with a backlight. The information displayed on the display unit may include not only the current value measured by the measurement unit 4a, but also voltage, power, or numbers representing the mode or status. In addition, the measuring housing 4c may have an operating section (not shown), and there are no particular limitations on the configuration, function, or location of this operating section, but for example, it may have multiple buttons. The functions of the control panel may include, for example, a button to turn the display on and off (display button), a reset button to reset the coil material 1, buttons to select a mode or state (such as a "+" button or a "-" button), or a set button to confirm (set) the selected mode, etc. The position of such an operating unit may also be, for example, located on the front of the measuring housing 4c, below the display unit described above. The measuring housing 4c may have terminal sections (also called terminal blocks, not shown), and there are no particular limitations on the number or position of these terminal sections. For example, one measuring housing 4c may have one terminal section or multiple terminal sections (such as three). The terminal section may also be located, for example, on the lower half of the back of the measurement housing 4c.

[0045] <Power Plant 10> As shown in Figure 5, the power plant 10 according to the present invention has the current measurement system 1 described above, and also has a power generation unit 11 (described later), a conversion unit 12 (described later), a transformer (which can also be described as being for power generation or for the power load 21b) 13 (described later), a load switch 14 (described later), and a control panel enclosure 15 (described later). The power plant 10 has at least a load switch 14 built into the panel enclosure 15, and may also have the above-mentioned current measurement system 1, the high-voltage circuit 16H described later, the instrument transformer (which can also be considered an add-on) 17 described later, the zero-sequence voltage detector (which can also be considered an add-on) 18, etc., inside the panel enclosure 15. Furthermore, the power plant 10 may also have a generator circuit breaker 19 (described later), another transformer (which could also be called one for lighting loads) 20, loads 21 (lighting load 21a, power load 21b), and load circuit breakers 22. It may also have control devices, vacuum circuit breakers (VCB), disconnecting switches (DS), overcurrent relays (OCR), etc. (not shown). In addition, the power plant 10 may have a voltage and current transformer (VCT) 31a and pole air switches (PAS) 31b in the circuit (high-voltage circuit 16H) between the load switch 14 and the system K, and may also have electricity meters for purchased electricity, electricity meters for sold electricity, and protective relay devices (Storage Over Current Ground, SOG) attached to the pole air switches (not shown). Furthermore, the pole air switches may also have built-in instrument transformers, current measurement systems, and surge arresters. These trading transformers 31a, pole-mounted air switches 31b, electricity meters for purchased electricity, electricity meters for sold electricity, and protective relay devices may be assumed to be part of the system on the K side (power company side), as described later.

[0046] <Power generation section 11> As shown in Figure 5, the power generation unit 11 is the part that generates electricity, and can have any configuration. For example, it may perform solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, solar thermal power generation, power generation using heat from the atmosphere or other heat present in nature, or power generation using biomass (organic matter derived from plants and animals that can be used as an energy source). In addition, the power generation unit 11 may generate electricity using ocean thermal energy, wave power, ocean currents, or tides. In a single power plant 10, there are no particular limitations on the number of power generation units 11; for example, there may be one or multiple units. The power generation capacity of the power generation unit 11 is not particularly limited, but may be, for example, 100kW or more and 30,000kW or less, preferably 300kW or more and 20,000kW or less, and even more preferably 500kW or more and 10,000kW or less. The following describes the solar power generation unit 11, which generates electricity using solar power.

[0047] The solar power generation unit 11 is equipped with a solar cell 11a. In addition, the photovoltaic power generation unit 11 may also include a pyranometer for measuring solar radiation intensity, and a current collector for collecting DC current from solar cells 11a and junction boxes and sending it to a conversion unit 12, which will be described later. The photovoltaic power generation unit 11 may have multiple solar cells 11a, and these multiple solar cells 11a may be connected in series to form a solar cell string. The photovoltaic power generation unit 11 may have a junction box in which multiple solar cell strings are connected in parallel, and there may be multiple such junction boxes.

[0048] <Solar cell 11a> As shown in Figure 5, each solar cell 11a generates DC power between its positive and negative poles when exposed to light. Solar cells 11a are typically panel-shaped, and the amount of power generated varies depending on the angle at which they are installed. The solar cell 11a may be installed at a predetermined angle to the installation site via a mounting frame (not shown), in which case the area beneath the mounting frame may be used for growing grass or cultivating crops. Furthermore, among the multiple solar cells 11a, the positive terminal of one solar cell 11a is connected to the negative terminal of another solar cell 11a, and the positive terminal of that solar cell 11a is connected to the negative terminal of yet another solar cell 11a, and so on, until multiple solar cells 11a are connected in series to form a single solar cell string.

[0049] Thus, the voltage between the positive and negative terminals of the entire solar cell string, in which multiple solar cells 11a are connected in series, is the sum of the DC voltages generated by each solar cell 11a, and fluctuates depending on the weather, time of day, etc. The power output from the power output terminal of the solar cell string is the sum of the power of each solar cell 11a, and may be between 500W and 6000W. The multiple solar cell strings described above are connected in parallel to a single junction box. Therefore, the voltage between the positive and negative terminals of each solar cell string is the same. However, the current from multiple solar cell strings flows into a single junction box, and the power collected in the junction box may be between 2.5 kW and 90 kW.

[0050] <Conversion Unit 12> As shown in Figure 5, the conversion unit 12 is the part that converts the DC current or AC current from the power generation unit 11 described above into a low-voltage AC current L. The conversion unit 12 may include an inverter that converts the direct current from the solar cell 11a into alternating current, and may also include a controller that controls the voltage and frequency of the alternating current converted by the inverter, as well as an air circuit breaker (ACB). The conversion unit 12 is also called a power conditioner (abbreviation for power converter). In a single power plant 10, there are no particular limitations on the number of conversion units 12; for example, there may be multiple units (e.g., four or five) or just one unit.

[0051] The conversion power (capacity) that the conversion unit 12 can convert is not particularly limited, but for example, it may be 30kW or more and 10000kW or less, preferably 50kW or more and 5000kW or less, and even more preferably 100kW or more and 2000kW or less (such as 250kW or 500kW). Furthermore, the converted power of the conversion unit 12 may be less than the power generated by the solar power generation unit 11 (in other words, the power generation capacity may be greater than the converted power), in which case the solar cell 11a can be said to be overloaded relative to the conversion unit 12. In addition, the conversion unit 12 may have an undervoltage relay (UVR), an overvoltage relay (OVR), an underfrequency relay (UFR), an overfrequency relay (OFR), or passive or active islanding protection devices.

[0052] <Transformer 13> As shown in Figure 5, the transformer 13 is a device that transforms (steps up) the low-voltage AC current L from the conversion unit 12 described above into a higher-voltage AC current H, and is a so-called transformer. Note that "transformer" is an abbreviation of "transformer". Furthermore, when the transformer 13 transforms the current from the power generation unit 11 via the conversion unit 12, it can be said to be a transformer for power generation, and when it transforms the current used for the power load 21b, it can be said to be a transformer for the power load 21b. In a single power plant 10, there are no particular limitations on the number of transformers 13; for example, there may be multiple (e.g., two) or just one. Furthermore, in the power plant 10 described later, the transformer 13 can be said to be connected between the system K (high-voltage circuit 16H side) and the conversion unit 12 (low-voltage circuit 16L side). The capacity of the transformer 13 (in VA, continuous rating) is not particularly limited, but for example, it may be 50 kVA or more and 2000 kVA or less, preferably 100 kVA or more and 1500 kVA or less, and even more preferably 200 kVA or more and 1000 kVA or less (such as 300 kVA or 500 kVA).

[0053] The transformer 13 is not limited in its configuration; for example, it may be a two-winding transformer, a three-winding transformer, or a transformer with four or more windings. The following description will primarily assume that transformer 13 is a two-winding transformer. The transformer 13, which is a two-winding transformer, may, for example, have its primary side be the high-voltage circuit 16H side and its secondary side be the low-voltage circuit 16L side. In this case, there are no particular restrictions on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 16H side, may be 5000V or more and 40000V or less, preferably 5500V or more and 30000V or less, and more preferably 6000V or more and 25000V or less (such as 6600V or 22000V), and the voltage of the secondary side, which is the low-voltage circuit 16L side, may be 10V or more and 1000V or less, preferably 50V or more and 800V or less, and more preferably 100V or more and 600V or less (such as 210V or 105V to 210V).

[0054] There are no particular restrictions on the wiring method of the primary and secondary sides of the transformer 13. For example, the primary side, which is the high-voltage circuit 16H side, may be connected in a star configuration (Y connection), and the secondary side, which is the low-voltage circuit 16L side, may be connected in a triangle configuration (Δ connection) (i.e., Y-Δ connection). In addition, the primary side and secondary side may be connected in a YY configuration, Δ-Y configuration, or Δ-Δ configuration. Transformer 13 may be an oil-filled transformer (such as self-cooled, air-cooled, or water-cooled) or a dry-type transformer (such as self-cooled, air-cooled, or water-cooled), and may also have a contact prevention plate or be grounded in the Class B configuration.

[0055] <Load switch 14> As shown in Figure 5, the Load Break Switch (LBS) 14 is installed in the circuit between the transformer 13 and the system K (high-voltage circuit 16H, which will be described later) and is built into the panel enclosure 15, which will be described later. The load switch 14 is a device that switches the high-voltage circuit 16H (all three phases and three wires together) when a high-voltage AC current H (load current) is flowing through it, and is also called a high-voltage AC load switch. The load switch 14 may have power fuses (four, etc., not shown). Furthermore, the load switch 14 may have an insulating barrier, and the load switch 14 may be opened and closed by a hook operation. In a single power plant 10, there are no particular limitations on the number of load switches 14. For example, there may be one, or there may be multiple (for example, two), and the number may be the same as the number of transformers (the total number of transformers (for power generation and / or for power load 21b) 13 mentioned above and the other transformers (for lighting load 21a) 22 described later). In the following discussion, we will primarily assume that there is one load switch 14 in the power plant 10. The main current transformer 2 in the current measurement system 1 described above may be provided in the circuit (high-voltage circuit 16H) between the load switch 14 and each transformer (transformer 13 for power generation, transformer 20 for lighting load 21a, etc.).

[0056] <Controller enclosure 15> As shown in Figures 3 and 5, the panel enclosure 15 is an enclosure that houses at least the load switch 14 described above, which is among the equipment in the power plant 10. The panel enclosure 15 may be a distribution panel enclosure, or any other panel enclosure such as a power receiving panel, power receiving and distribution panel, or grid connection panel. The control panel enclosure 15 may also incorporate other components such as a current measurement system 1, a high-voltage circuit 16H, an instrument transformer 17, and a zero-sequence voltage detector 18. The control panel enclosure 15 may have any configuration, but for example, it may be formed in a roughly rectangular parallelepiped shape overall. Such a panel enclosure 15 may be composed of frame pipes 15a and mounting frames 15b that extend linearly in the vertical, horizontal, and height directions. In particular, the frame pipes 15a that extend linearly in the vertical and horizontal directions may have the substantially rectangular annular coil member 2a of the main current transformer 2 of the current measurement system 1 described above suspended and fixed to them. As shown in Figure 3, to elaborate on this suspension-type fixing, the substantially rectangular annular coil member 2a may be fixed in a suspension-type manner to the flat plate portion or bottom surface of the frame pipe 15a that extends linearly in the horizontal direction, either directly or via the mounting frame 15b. Here, there are no particular limitations on the shape or configuration of the mounting frame 15b, but for example, it may be roughly L-shaped, and in this case, the roughly L-shaped mounting frame 15b may be fixed to the roughly rectangular annular coil member 2a by fastening means such as screws on the upper side and on either the left or right side, so as to avoid the central opening 2b. In addition, the mounting frame 15b may be in the shape of a rod or a flat plate with a longitudinal direction, and in these cases, the mounting frame 15b may be fixed to the roughly rectangular annular coil member 2a only on the upper side or only on one side, avoiding the central opening 2b.

[0057] <High voltage line 16H, low voltage line 16L> As shown in Figure 5, the high-voltage circuit 16H is a circuit that connects the transformer 13 and the system K mentioned above and carries the high-voltage alternating current H, and can also be described as a high-voltage cable. Furthermore, the high-voltage circuit 16H may branch off at some point (for example, between the main current transformer 2 and the transformer 13 of the current measurement system 1) and be connected to the instrument transformer 17 or the zero-sequence voltage detector 18. Since this branched circuit also carries a high-voltage alternating current H, it can be said to be a high-voltage circuit 16H. High-voltage circuits 16H can be configured as a set of three wires if it is a three-phase three-wire (3φ3W) or single-phase three-wire (1φ3W) system, or as a set of two wires if it is a single-phase two-wire (1φ2W) system, and so on, depending on the power distribution system (power transmission system).

[0058] On the other hand, as shown in Figure 5, the low-voltage circuit 16L is a circuit that connects the conversion unit 12 and the transformer 13 described above and carries a low-voltage alternating current L, and can also be called a low-voltage cable. Furthermore, the low-voltage circuit 16L may also branch off at some point (for example, between the transformer 13 and the converter 12) according to the number of converters 12, and since each of these branched circuits carries a low-voltage alternating current L, it can also be said to be a low-voltage circuit 16L. In addition, the circuit between transformer 13 and load 21 (power load 21b), and the circuit between transformer 20 for the lighting load 21a (described later) and load 21 (lighting load 21a), also carry a low-voltage alternating current L, and can therefore be considered low-voltage circuits 16L. Low-voltage circuits (16L) can also be configured as a set of multiple wires depending on the power distribution system (power transmission system). For example, three-phase three-wire (3φ3W) or single-phase three-wire (1φ3W) systems may consist of three wires, while single-phase two-wire (1φ2W) systems may consist of two wires.

[0059] <Instrument transformer 17, zero-sequence voltage detector 18> As shown in Figure 5, the Voltage Transformer (VT) 17 is installed in the high-voltage circuit 16H described above and is a device that transforms (steps down) the high-voltage AC current H flowing through the high-voltage circuit 16H into a lower voltage transformer output current. Furthermore, there may be more than one (e.g., two) instrument transformers 17 in a single power plant 10. The instrument transformer 17 may be connected to the measuring instrument 4 described above by an electrical circuit. The capacity of the instrument transformer 17 is not particularly limited, but for example, it may be 10VA or more and 500VA or less, preferably 20VA or more and 300VA or less, and even more preferably 40VA or more and 200VA or less (such as 100VA). The instrument transformer 17 is not limited in its configuration and may be a transformer with three or more windings, but it will be mainly described as a two-winding transformer. The instrument transformer 17, which is a two-winding transformer, may, for example, have its primary side be the high-voltage circuit 16H side and its secondary side be the measuring instrument 4 side, which is a reverse power relay. In this case, there are no particular restrictions on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 16H side, may be 5000V or more and 40000V or less, preferably 5500V or more and 30000V or less, and more preferably 6000V or more and 25000V or less (such as 6600V or 22000V), and the voltage of the secondary side, which is the measuring instrument 4 side, may be 10V or more and 600V or less, preferably 20V or more and 400V or less, and more preferably 50V or more and 300V or less (such as 110V). The instrument transformer 17 may have power fuses (PF) on the primary and / or secondary sides.

[0060] As shown in Figure 5, the Zero Phase Potential Device (ZPD) 18 is installed in the high-voltage circuit 16H described above and is a device that detects whether or not a zero-phase voltage has been generated on the high-voltage circuit 16H side when a ground fault (such as a complete single-line ground fault in a three-phase three-wire system) occurs in any of the systems (including the system K side) on the high-voltage circuit 16H side of the power plant 10. The zero-phase voltage detector 18 is also known as a zero-phase voltage transformer (ZVT), etc. The zero-sequence voltage detector 18 may also be connected to the measuring instrument 4 described above by an electrical circuit. When such a zero-sequence voltage detector 18 detects a zero-sequence voltage, a zero-sequence output current of a lower voltage (for example, about 1V or about 6-9V) corresponding to the zero-sequence voltage generated in the power plant 10, etc., is output from the zero-sequence voltage detector 18 and flows through the circuit to the measuring instrument 4, which is a ground fault overvoltage relay. In addition, the zero-sequence voltage detector 18 may incorporate a capacitor 18a or a transformer (zero-sequence transformer) 18b to divide the voltage, and may also be grounded in the Class A configuration.

[0061] <Generator circuit breaker 19, another transformer 20, load 21, load circuit breaker 22, control device, etc.> As shown in Figure 5, the power generation circuit breaker 19 is a device capable of interrupting the low-voltage AC current L from the conversion unit 12 described above. In other words, it is a device installed in the low-voltage circuit 16L, which will be described later, and capable of interrupting the low-voltage circuit 16L. It can also be said to be a low-voltage circuit breaker. The generator circuit breaker 19 may be a molded case circuit breaker (MCCB) or an earth leakage circuit breaker (ELCB). There may be more than one power plant circuit breaker 19 in a single power plant 10. For example, as described above, if the low-voltage circuit 16L branches between the transformer 13 and the converter 12, according to the number of converters 12, one circuit breaker 19 may be provided between the branching point and the transformer 13, and one more may be provided between the branching point and each converter 12.

[0062] As shown in Figure 5, the other transformer 20 can also be described as a transformer for the lighting load 21a, and is a device that transforms (steps down) the power from the grid K and the power generation unit 11, etc., and is a so-called transformer. Note that "transformer" is an abbreviation of "transformer". The capacity of the transformer 20 for the lighting load 21a may be the same as that of the transformer 13 described above, and the configuration of the transformer 20 for the lighting load 21a may be a two-winding transformer or the like. The primary side of the transformer 20 for the lighting load 21a is also the high-voltage circuit 16H side, and its secondary side can be said to be the low-voltage side. In this case, there are no particular restrictions on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 16H side, may be the same as that of the transformer 13 described above, and the voltage of the secondary side, which is the low-voltage side, may be 10V or more and 1000V or less, preferably 50V or more and 800V or less, and even more preferably 100V or more and 600V or less (105V to 210V, etc.). There are no particular restrictions on the wiring method of the primary and secondary sides of the transformer 20 for the lighting load 21a. For example, the primary side, which is the high-voltage circuit 16H side, may be a star connection (Y connection), and the secondary side, which is the low-voltage side, may be a single-phase three-wire connection (i.e., a Y-three connection). In addition, the primary side and secondary side may be Y-Δ connection, YY connection, Δ-Y connection, or Δ-Δ connection. The transformer 20 for the lighting load 21a may also be an oil-filled transformer or a dry-type transformer. It may also have a contact prevention plate or be equipped with Class B grounding.

[0063] As shown in Figure 5, the load 21 is a device that consumes power from the power generation unit 11 via the conversion unit 12, and power from the grid K via the grid connection unit 14, transformer 13, etc. Load 21 can be any configuration, but for example it could be lighting in a factory (lighting load 21a), an industrial motor in a factory (power load 21b), or a lighting distribution board connected to multiple lights. It could also be an air conditioner, fluorescent lights, home appliances in a house or office building, a vehicle such as an electric car or a gasoline car, or equipment inside such a vehicle. Furthermore, as shown in Figure 5, the load circuit breaker 22 is a device capable of interrupting the circuit between the transformer 20 for the lighting load 21a and the load 21 (lighting load 21a), and the circuit between the transformer 13 and the load 21 (power load 21b), and may be a circuit breaker or a ground fault circuit interrupter.

[0064] The control device may be a device connected to the measuring instrument 4 mentioned above, which receives a stop signal output from the measuring instrument 4 as a reverse power relay or ground fault overvoltage relay, and controls the conversion of the conversion unit 12 mentioned above, or it may be a smart logger, a sequencer, a computer, etc. In a single power plant 10, the number of control devices may be one or more. The control device may be powered by an uninterruptible power supply (not shown) or similar device. Furthermore, monitoring, configuration changes, and operation of the control device may be performed directly by the user, but may also be performed remotely via the internet, telephone lines, etc.

[0065] <Exam / Exam Structure> In the tests of the present invention, test configurations 1 and 2 are prepared for measuring the ratio error between current and power using the current measurement system 1 described above, and these are used in the tests. First, let's take a closer look at the structure of these two exams.

[0066] <Test Configuration 1> As shown in Figure 4(a), in Test Configuration 1, for each of the approximately rectangular annular coil members 2a (primary and secondary current transformation ratio of 1500:1) of the two main current transformers 2 (side 1 and side 3) in one current measurement system 110, the test equipment for Test Configuration 1 consists of a device that supplies a predetermined input current value (reference value), which is the AC current to be measured (frequency 50Hz or 60Hz), as the primary input to the approximately rectangular annular coil member 2a (voltage 4-phase current 4-phase protection relay tester (RX4744 manufactured by NF Circuit Design Block Co., Ltd.) and a digital power meter (Yokogawa Electric). A "WT1600" X1 manufactured by Daiichi Electronics Co., Ltd. and a protective relay digital multi-relay X2 (connected to the 0.1A terminal of a "DMR-RW1" manufactured by Daiichi Electronics Co., Ltd.) that inputs the output current flowing from the approximately rectangular annular coil member 2a to the primary-secondary sensor circuit 1a, are used. The output from the protective relay digital multi-relay X2 is input to the two auxiliary coil sections 3a of the auxiliary current transformer 3 (so to speak, secondary input), and the output current from the auxiliary current transformer 3 is input to the measuring instrument 4 via the secondary-tertiary sensor circuit 1b (so to speak, tertiary input). Furthermore, a metal mounting panel X3 is attached to the measuring instrument 4, and a predetermined voltage AC current is supplied to the measuring instrument 4 from equipment X1. In addition, the measuring instrument 4 is also supplied with power from a separate control power supply. This type of test configuration 1 can be described as a configuration with inputs of 100%, 20%, 5%, etc.

[0067] <Test Structure 2> As shown in Figure 4(b), in Test Configuration 1, the protective relay digital multi-relay X2 was removed, and the outputs from the approximately rectangular annular coil members 2a of the two main current transformers 2 were directly input to the two auxiliary coil portions 3a of the auxiliary current transformer 3 via the primary-secondary sensor circuit 1a (so to speak, secondary input). Furthermore, in addition to grounding the primary-secondary sensor circuit 1a, an earth plate X4 was provided that extended over the entire current measurement system 1 (main current transformer 2, auxiliary current transformer 3, and measuring instrument 4). This earth plate X4, the metal mounting panel X3, the measuring instrument 4, and the circuit that supplies a predetermined voltage AC current from equipment X1 to the measuring instrument 4 were all connected and grounded. In addition, the power supply for the measuring instrument 4 was changed by removing the separate control power supply and connecting a predetermined voltage AC current from equipment X1. This configuration was Test Configuration 2. This type of test configuration 2 can be described as a configuration for an input of 0.2%, etc.

[0068] <Exam> The test will measure whether the difference in the number of turns in the auxiliary coil portion 3a of the auxiliary current transformer 3 affects the ratio error of the current value and power value. For the above-described test configurations 1 and 2, we used test example A, in which the auxiliary coil portion 3a of the auxiliary current transformer 3 had "8 turns", and test example B, in which it had "12 turns". Due to this difference in the number of turns, 100% of the rated current for test example A was 200A, and 100% of the rated current for test example B was 30A. Furthermore, regardless of whether the ratio error of current or power was being measured, for the main current transformer 2 in the above-described test configuration 1, a current in the range of 120% to 0.4% of the rated current (strictly speaking, 120%, 100%, 80%, 60%, 50%, 40%, 20%, 10%, 8%, 6%, 5%, 4%, 2%, 1%, 0.8%, 0.6%, 0.5%, 0.4%, 0%) was input, and for the main current transformer 2 in the above-described test configuration 2, a current in the range of 0.2% of the rated current was input, and the measurement was taken by measuring instrument 4 after passing through auxiliary current transformer 3. Table 1 shows the ratio error of the current values ​​through the main current transformer 2 on side 1 and side 3 when 100%, 20%, 5%, and 0.2% of the rated current are input from the measurement results of the measuring instrument 4. Table 2 shows the ratio error of the power value (assuming a power factor (cosφ) = 1) based on the AC current supplied to the measuring instrument 4, with respect to the currents through the main current transformer 2 on side 1 and side 3. Furthermore, the input from device X1 (primary input) can be said to be, so to speak, the predetermined circuit D.

[0069] [Table 1]

[0070] [Table 2]

[0071] <Evaluation of the exam> From Tables 1 and 2, regarding the measurement of ratio errors in current and power values, regardless of whether the number of turns in the auxiliary coil portion 3a of the auxiliary current transformer 3 is "8 turns" or "12 turns," or the input percentage, it can be said that, generally speaking, the measurement is within the specified value of the inherent error of the measuring instrument 4. However, in the case of auxiliary current transformer 3 in test example B with a 100% input, the measurement exceeds the specified value of the inherent error of the measuring instrument 4, but this can also be considered a measurement error.

[0072] <Other> The present invention is not limited to the embodiments described above. The structure, shape, dimensions, and other details of the current measurement system 1, the power plant 10, and other components or the overall structure can be modified as appropriate in accordance with the spirit of the present invention. The electrical circuit D that is the target of measurement by the current measurement system 1 does not have to be a three-phase three-wire system; for example, it could be a single-phase three-wire system or a single-phase one-wire system. Even if the circuit D that is the target of measurement by the current measurement system 1 is a three-phase, three-wire circuit, a main current transformer 2 may be attached to each of the three wires of the circuit D. In this case, it can also be said that the number of auxiliary coil portions 3a in the auxiliary current transformer 3 will also be three. Even if there are multiple auxiliary coil members 3a (such as two or three) in the auxiliary current transformer 3, these auxiliary coil parts 3a do not necessarily have to be housed in a single auxiliary housing 3b. In this case, each auxiliary coil part 3a may be housed in a separate auxiliary housing 3b. The shape of the annular coil member 2a and the shape of its central opening 2b in the main current transformer 2 do not have to be approximately rectangular; for example, they may be approximately circular. In the roughly rectangular annular coil member 2a of the main current transformer 2, it is acceptable for it to be mounted to the circuit D such that the opening direction of its central opening 2b is not roughly horizontal. In this case, the opening direction of the central opening 2b may be slightly offset from the horizontal (i.e., diagonally), or it may be mounted in a roughly vertical direction. Furthermore, the direction in which the electrical circuit D is inserted into the central opening 2b of the annular coil member 2a in the main current transformer 2 does not have to be approximately horizontal. In this case, the direction in which the electrical circuit D is inserted may be slightly off from the horizontal direction (i.e., at an angle), or it may be approximately vertical. The measuring instrument 4 may have only a measuring unit 4a and may not have a relay unit 4b or a correction unit 4d.

[0073] The power plant 10 does not need to have the load switch 14 built into the panel enclosure 15, nor does it need to have the load switch 14 itself. In this case, the power plant 10 may have a vacuum circuit breaker. In the power plant 10, the main current transformer 2 (a roughly rectangular annular coil member 2a) does not have to be installed in the circuit between the transformer 13 and the load switch 14. In this case, for example, it does not have to be installed in the circuit between the system K and the load switch 14. The roughly rectangular annular coil member 2a in the main current transformer 2 does not necessarily have to be fixed inside the enclosure 15; in this case, for example, it may be fixed outside the enclosure 15. Furthermore, the roughly rectangular annular coil member 2a in the main current transformer 2 does not necessarily have to be fixed in a suspended manner, even if it is fixed inside the enclosure 15. For example, it may be fixed inside the enclosure 15 in a way that protrudes laterally from the frame pipe 15a that extends in the vertical direction (in other words, so that the opening direction of the central opening 2b is roughly vertical). The power plant 10 may have an energy storage unit for storing energy. The energy storage unit may be a capacitor device, an uninterruptible power supply, or other types of batteries such as lead-acid batteries, lithium-ion batteries, nickel-metal hydride batteries, or nickel-cadmium batteries. It may also be a device that stores hydrogen produced by electrolysis of water using power generated from the power generation unit 11, etc., and extracts power using a fuel cell or the like when needed. Alternatively, it may store energy as kinetic energy using a flywheel or store energy as potential energy using pumping. In this case, the energy storage unit may be connected to the aforementioned conversion unit 12 or low-voltage circuit 16L, etc., and may charge the power output from the power generation unit 11, etc., or flow the charged power to the load 21 for consumption (self-consumption), or if it is possible to sell the power, it may flow the charged power to the grid K. The power plant 10 and its related grid K, as described above, will be explained in detail below.

[0074] <System K> As shown in Figure 2, System K is the system that transmits (receives) electricity to the power plant 10, and refers to the entire system for power companies and others to supply electricity to consumers, and can also be called the power grid K. Specifically, System K is equipped with facilities such as substations, transmission lines, and distribution lines, and may also include power plants. Furthermore, System K may also have the aforementioned trading transformer 31a, pole-mounted air switch 31b, electricity meter for purchased electricity, electricity meter for sold electricity, and protective relay devices. The power handled in such a system K can be either AC or DC, but the following explanation will assume it is AC. In system K, since most of the transmitted power is alternating current, it is transmitted via a three-phase three-wire (3φ3W) system on the transmission lines. To reduce transmission losses during transmission, the main long-distance transmission sections are transmitted at the highest possible voltage (for example, 6600V or 22000V). The electricity transmitted through system K is transformed (stepped down) in several stages near the point of consumption, and after the pole-mounted transformers, distribution is also carried out using single-phase two-wire (1φ2W) systems. System K may be a power grid owned by a power company (commercial power grid), or it may be a system or internal power grid owned by an organization such as a company or local government (independent power grid). [Industrial applicability]

[0075] The current measurement system of the present invention can be used for self-consumption type solar power plants (a type of power plant) regardless of their power generation amount or scale. In addition to self-consumption type solar power plants, it can also be used for non-self-consumption type solar power plants, plants that generate electricity using generators (AC motors, etc.) rotated by wind, hydro, wave, geothermal, etc., and even plants that do not have a power generation unit. It can be used both indoors and outdoors. The power plant of the present invention can be used for self-consumption type solar power plants, regardless of their power generation capacity or scale. In addition to self-consumption type solar power plants, it can also be used in non-self-consumption type solar power plants, and in plants that generate electricity using generators (such as AC motors) rotated by wind, hydro, wave, or geothermal power, and can be used both outdoors and indoors. [Explanation of symbols]

[0076] 1. Current measurement system 2 Main current transformer 2a Annular coil component of the main current transformer 2b Central opening of the main current transformer 3 Auxiliary current transformer 3a Auxiliary coil member 3b Auxiliary enclosure 4 Measuring Instruments 10 Power Plants 11 Power Generation Department 12 Conversion section 13 Transformer 14 Load switch 15-inch cabinet D electric circuit Z insulation distance L Low voltage AC current H High-voltage alternating current K lineage

Claims

1. A current measuring system installed in an electrical circuit, The current measurement system comprises a main current transformer (2) attached to the circuit, an auxiliary current transformer (3) that outputs a current value corresponding to the output from the main current transformer (2), and a measuring instrument (4) that measures at least the current value flowing through the circuit based on the output from the auxiliary current transformer (3). The main current transformer (2) includes an annular coil member (2a), The annular coil member (2a) is provided with a central opening (2b) that can secure a predetermined insulation distance (Z) with respect to the electrical circuit through which it is inserted. A current measurement system characterized in that the aforementioned insulation distance (Z) is 20 mm or more.

2. The aforementioned circuit is a three-phase, three-wire system. The main current transformer (2) is attached to each of the three wires of the aforementioned circuit. The auxiliary current transformer (3) outputs a current value corresponding to the output from each of the main current transformers (2). The auxiliary current transformer (3) comprises two auxiliary coil members (3a) that output current values ​​corresponding to the output from each of the main current transformers (2). The current measurement system according to claim 1, characterized in that the two auxiliary coil members (3a) are housed in one auxiliary housing (3b).

3. The annular coil member (2a) in the main current transformer (2) is substantially rectangular in shape. The central opening (2b) in the aforementioned roughly rectangular annular coil member (2a) is also roughly rectangular in shape. The current measuring system according to claim 1 or 2, characterized in that the substantially rectangular annular coil member (2a) is attached to the electrical circuit such that the opening direction of the central opening (2b) is substantially horizontal, and the direction in which the electrical circuit is inserted into the central opening (2b) is also substantially horizontal.

4. A power plant having the current measurement system (1) described in claim 3, The power plant comprises a power generation unit (11), a conversion unit (12) that converts a direct current or alternating current from the power generation unit (11) into a low-voltage alternating current (L), a transformer (13) capable of transforming the low-voltage alternating current (L) from the conversion unit (12) into a higher voltage alternating current (H), a load switch (14) provided between the transformer (13) and the grid (K), and a panel enclosure (15) that at least houses the load switch (14). The main current transformer (2) is installed in the circuit between the transformer (13) and the load switch (14). A power plant characterized in that the substantially rectangular annular coil member (2a) in the main current transformer (2) is fixed in a suspended manner inside the panel housing (15).

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