Long cable type measurement system, control panel, and power plant

Abstract

To realize "extension and securing accuracy of a cable" and the like by connecting shield line of a shield of a sensor cable to a current measuring terminal of a measurement part and grounding the measurement part.SOLUTION: A measurement system 1 for measuring a current value of a predetermined cable way comprises: a current sensor 2 outputting sensor current D according to a current value of the cable way; a sensor cable 3 through which the sensor current D flows; and a measurement part 4 measuring the current value of the cable way based on the sensor current D. A shield line 5b of a shield 5 of the sensor cable 3 is connected to a current measuring terminal 4A of the measurement part 4, and the measurement part 4 is grounded. Alternatively, the shield line 5b of the shield 5 may be connected to a current measuring terminal 4Ab at low potential side; a terminal having substantially the same potential as the current measuring terminal 4Ab at the low potential side is grounded; or length of the sensor cable 3 may be set to be 20 m or more and 2000 m or less. The measurement system 1 including a relay part 6 and a power storage part 11 are provided in a panel housing 10' of a control panel 10, and the measurement system 1 measures received power from a system G of an electric power plant 100.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measurement system, a control panel, and a power plant for at least measuring a current value of a current flowing through a predetermined electric circuit.

Background Art

[0002] Conventionally, a method for renovating an existing structure that renovates a building provided with a power load supplied with power from an existing power source is known (see Patent Document 1). This method for renovating an existing structure installs a distributed power source and a secondary battery in the existing structure when renovating the existing structure, and installs a power control panel for performing power control on the distributed power source and the secondary battery. The distributed power source and the secondary battery are connected to the power control panel, and the existing power source and the power load are connected. After the renovation of the existing structure is completed, the power control panel performs power control on the distributed power source and the secondary battery, and controls the amount of power supplied from the existing power source.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for renovating existing structures described in Patent Document 1, paragraph 0080 states that "when renovating an existing building, a power control panel is installed and connected to the existing commercial power supply and power load, as well as to the newly installed solar power generation equipment and secondary batteries. By installing this power control panel anew during renovation, it becomes possible to handle the situation regardless of the capacity or quantity of the newly installed solar power generation equipment and secondary batteries." Paragraph 0064 states that "the shortfall in power generated by the solar power generation equipment relative to the power load will be covered by power stored in the secondary batteries or power supplied from the commercial power supply. In zero-energy control, the supply of power from the commercial power supply is suppressed as much as possible." Figure 8, etc., discloses "the amount of power supplied from the commercial power supply." Therefore, when connecting newly installed power control panels, solar power generation equipment, etc., to existing commercial power sources (i.e., grids and receiving equipment) and power loads, it is necessary to always accurately monitor the power from the grid and receiving equipment. To achieve this, a current sensor is installed in the busbar circuit between the grid and the power load, and the output current corresponding to the high-voltage AC current (and its current value) flowing through the busbar circuit is output via an output cable to a measuring device inside the power control panel.

[0005] However, due to electrical noise and electromagnetic waves from existing structures, building wiring, and electrical equipment such as home appliances interfering with the output cable between the current sensor and the measuring device, the accuracy of the current value could only be ensured up to a length of approximately 10 meters when determining the power supply from the grid and power receiving equipment. Furthermore, because the locations of power grids and receiving equipment are fixed in existing structures and buildings, the approximately 10m long output cable severely limits the locations where new power control panels can be installed, creating a problem in accommodating the installation of new power control panels and solar power generation equipment. Such problems are not limited to cases where power control panels or solar power generation equipment are newly installed in existing structures or buildings; they also apply to other cases, such as when a power generation system and its control panel are newly installed for an existing grid connection panel that connects to the grid, or for an existing load connected to that grid connection panel.

[0006] In view of these points, the present invention aims to provide a measurement system, control panel, and power plant that achieve "extension of the cable and assurance of accuracy" by connecting the shield wire of the sensor cable's shield to the current measurement terminal of the measurement unit and grounding the measurement unit. [Means for solving the problem]

[0007] The measurement system 1 according to the present invention is a measurement system for measuring at least the current value of a current flowing in a predetermined circuit, the measurement system comprising: a current sensor 2 attached to the circuit and outputting a sensor current D corresponding to the current value of the current flowing in the circuit; a sensor cable 3 through which at least the sensor current D from the current sensor 2 flows; and a measurement unit 4 that measures at least the current value of the current flowing in the circuit based on the sensor current D input via the sensor cable 3, the measurement unit 4 comprising a current measurement terminal 4A to which the sensor cable 3 is connected, the sensor cable 3 having a shield 5 attached, the shield 5 comprising a conductive shield layer 5a covering the sensor cable 3 and a shield wire 5b conductive to the conductive shield layer 5a, and the shield wire 5b connected to the current measurement terminal 4A of the measurement unit 4. By doing so, electrical conductivity is established to the sensor cable 3. The measurement unit 4 is, The terminal connected to the aforementioned sensor cable 3 is Its first characteristic is that it is grounded.

[0008] A second feature of the measurement system 1 according to the present invention is, in addition to the first feature described above, that the current measurement terminal 4A of the measurement unit 4 includes a high-potential side current measurement terminal 4Aa and a low-potential side current measurement terminal 4Ab, the sensor cable 3 includes a forward sensor cable 3a that carries current from the measurement unit 4 to the current sensor 2 and a return sensor cable 3b that carries current from the current sensor 2 to the measurement unit 4, at least the forward sensor cable 3a and the return sensor cable 3b are covered by one conductive shield layer 5a, the forward sensor cable 3a is connected to the high-potential side current measurement terminal 4Aa, the return sensor cable 3b is connected to the low-potential side current measurement terminal 4Ab, and the shield wire 5b of the shield 5 is connected to the low-potential side current measurement terminal 4Ab. This allows electrical conductivity to be established in the return sensor cable 3b. The measurement unit 4 is at approximately the same potential as the low-potential current measurement terminal 4Ab. and is electrically connected to the return sensor cable 3b terminals but It is located at the point where it is grounded.

[0009] A third feature of the measurement system 1 according to the present invention is, in addition to the second feature described above, that the current value of the sensor current D is measured by dividing the voltage value generated in the resistor 4' provided between the high-potential current measurement terminal 4Aa and the low-potential current measurement terminal 4Ab inside the measurement unit 4 by the resistance value of the resistor 4'. The measurement system 1 according to the present invention 4 The characteristic is as described in the first above. ~3 In addition to the features mentioned above, the length of the sensor cable 3 is between 20m and 2000m.

[0010] Due to these features, by connecting the shield wire 5b of the sensor cable 3's shield 5 to the current measurement terminal 4A of the measurement unit 4 and grounding the measurement unit 4, as shown in Tables 1 and 2 below, even when the length of the sensor cable 3 is extended to 100m, which is 10 times the approximately 10m at which accuracy was conventionally ensured, the accuracy of the measured values ​​is dramatically improved compared to when the shield wire 5b is directly grounded, and accuracy is ensured ("Cable Extension and Accuracy Assurance"). This "extension and accuracy assurance of the cable" greatly expands the flexibility of where the control panel 10 can be newly installed, even if the location of the grid G ​​and power receiving equipment is fixed, thanks to the sufficiently long sensor cable 3, when installing (connecting) a power generation device 60 or its control panel 10 to a grid connection panel 20 or load 40, or when installing a power control panel or solar power generation device in an existing structure or building. This improves the adaptability to new installations of the control panel 10 and power generation device 60 ("improved adaptability to new installations"). Furthermore, since this type of measurement system 1 allows the sensor cable 3 to be made significantly longer than the conventional length for which accuracy was ensured, it can also be described as a "long cable type measurement system."

[0011] Furthermore, by connecting the shield wire 5b of shield 5 to the low-potential current measurement terminal 4Ab, and grounding it from a terminal at approximately the same potential as the low-potential current measurement terminal 4Ab, further "cable extension and accuracy assurance" can be achieved. The length of the sensor cable 3 is not particularly limited, but it may be, for example, between 20m and 2000m.

[0012] The control panel 10 according to the present invention is the first ~3 A control panel having a measurement system 1 having the following characteristics inside a panel enclosure 10', wherein the control panel also has a power storage unit 11 inside the panel enclosure 10' that supplies power to the measurement system 1, and the measurement system 1 also includes a relay unit 6 that performs relay operations on electrical and electronic equipment outside the panel enclosure 10' according to a measurement value measured by a measurement unit 4 based on the sensor current D, at least, is a first characteristic of the control panel.

[0013] This feature means that the control panel 10 has the measurement system 1 and the energy storage unit 11 inside the panel enclosure 10'. As a result, the heat-sensitive measurement system 1 and the energy storage unit 11, such as the uninterruptible power supply, are less susceptible to heat from outside the panel enclosure 10' because they are surrounded by the enclosure 10'. For example, even above or near a transformer that generates high heat (such as the transformer 63b in the distribution panel 63 of the power generation device 60 described later), the risk of failure due to heat from the transformer is suppressed ("failure suppression of heat-sensitive equipment"), and further "improvement of adaptability to new installations" for the control panel 10 and the power generation device 60. Simultaneously, by also providing the measurement system 1 with a relay unit 6 that performs relay operations on electrical and electronic equipment outside the panel enclosure 10' according to the measured values, it becomes possible to control electrical and electronic equipment outside the panel enclosure 10', such as stopping the converter unit 62 of the power generation device 60. Here, the measurement system 1, which also includes the relay unit 6, can be said to be a control device, and the panel that incorporates the measurement system 1, which is also a control device, can indeed be said to be a control panel. Furthermore, since such a control panel 10 allows the sensor cable 3 extending from the control panel 10 to be significantly longer than conventional lengths, it can also be described as a "long cable type control panel."

[0014] others, The power plant 100 is the first ~3A power plant having a measurement system 1 having the following characteristics, the power plant having a grid connection panel 20 connected to grid G, a load 40 connected to the grid connection panel 20, a power generation device 60 connected to the grid connection panel 20 and load 40, a busbar 70 between grid G ​​and load 40, and a branch circuit 80 branching from the busbar 70 and connected to the power generation device 60, wherein the current sensor 2 is attached to the secondary circuit of an instrument current transformer 25 provided in the busbar 70 inside the grid connection panel 20, so that the measurement unit 4 of the measurement system 1 measures the current value of the current flowing through the busbar 70. The measurement unit 4 of the measurement system 1 is equipped with a voltage measurement terminal 4B to which a predetermined circuit is connected, and measures the voltage value of the current flowing through the circuit based on the current input from the circuit to the voltage measurement terminal 4B, and when the secondary circuit of the instrument transformer 63c provided in the branch circuit 80 of the power generation device 60 is connected to the voltage measurement terminal 4B, the measurement unit 4 of the measurement system 1 measures the voltage value of the current flowing through the branch circuit 80, and the measurement unit 4 of the measurement system 1 measures the power received from the grid G ​​based on the current value of the current flowing through the bus circuit 70 and the voltage value of the current flowing through the branch circuit 80. You can .

[0015] this case By attaching the current sensor 2 of the measurement system 1 to the secondary circuit of the instrument current transformer 25 in the grid interconnection panel 20 and measuring the current value of the current flowing through the busbar 70, and by connecting the secondary circuit of the instrument transformer 63c in the power generation device 60 to the voltage measurement terminal 4B and measuring the voltage value of the current flowing through the branch circuit 80, the measurement system 1 measures the power received from grid G ​​of the power plant 100. As a result, even if the grid interconnection panel 20 is far from the power generation device 60, the current value of the current flowing through the busbar 70 from grid G ​​can be directly measured using a longer sensor cable 3 than before, while the voltage value of the current flowing through the branch circuit 80, which is at approximately the same potential as the busbar 70, can be measured within the nearby power generation device 60, thus ensuring accuracy in the power received from grid G. At the same time, the modification of the circuit in the existing system connection board 20 only requires attaching the current sensor 2 to the secondary circuit of the instrument current transformer 25, simplifying the installation of the control panel 10, the power generation device 60, etc. Also, the measurement system 1 enables the measurement of the received power on the side of the power generation device 60 and the system connection board 20 side, eliminating the need for power reception confirmation work on the system connection board 20 side during the test adjustment and maintenance of the power generation device 60. (If the system connection board 20 is far from the power generation device 60, the merit of eliminating the power reception confirmation work on the system connection board 20 side is significant). In addition, such a power plant 100 can have a sensor cable 3 between the current sensor 2 and the measurement unit 4 in the power plant 100 made much longer than the conventional length, so it can also be said to be a "long cable type power plant".

Advantages of the Invention

[0016] According to the measurement system, control panel, and power plant according to the present invention, by connecting the shield wire of the shield of the sensor cable to the current measurement terminal of the measurement unit and grounding the measurement unit, it is possible to achieve "cable extension and accuracy assurance", etc.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram showing the measurement system according to the present invention. [Figure 2] It is a schematic circuit diagram showing the details of the sensor cable, measurement unit, and shield in the measurement system. The arrow on the left side of the resistor indicated by the reference numeral 4' in FIG. 2 represents the flow of current. [Figure 3] It is a schematic circuit diagram showing the measurement system, control panel, and power plant according to the present invention. The drawing substitute photograph in the upper left of FIG. 3 shows the inside of the actual control panel (control panel housing). [Figure 4] It is a drawing substitute photograph illustrating a current sensor attached to the secondary circuit between the instrument current transformer (on the other side of the partition wall, etc.) provided in the bus circuit and the overcurrent relay inside the cabinet of the system connection board, the sensor cable connected to the current sensor, and the shield. [Figure 5] The diagrams below show the test configurations of the measurement systems in Tests 1-3, with (a) showing Test Configuration 1, (b) showing Test Configuration 2, and (c) showing Test Configuration 3. Details of the sensor cable 3 in (b) and (c) (e.g., forward or return path) and details of the current input terminals and voltage input terminals (e.g., high potential side or low potential side) are the same as in (a). [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. <Measurement System 1> Figures 1 to 5 show the measurement system 1 according to the present invention. Measurement system 1 is a system that measures at least the current value of the current flowing through a predetermined circuit. The measurement system 1 includes a current sensor 2 (described later), a sensor cable 3 (described later), a measurement unit 4 (described later), and a shield 5 (described later). The measurement system 1 may have a relay unit 6, a system housing 7 that houses the relay unit 6 and the measurement unit 4, or the system housing 7 may have a display unit 8 that displays the measured values. Furthermore, there are no particular limitations on the power supply for the measurement system 1, but it may be shared with the voltage of the circuit being measured as described above (i.e., 110V, 220V, 440V at 60Hz or 50Hz, or 100V to 200V), or it may be 100V or 110V DC, or power may be supplied from a power storage unit 11 such as an uninterruptible power supply, as described later.

[0019] Here, the current, voltage, power, and capacity in this invention may be values ​​within the rated range, in which case they can be called rated current, rated voltage, rated power, and rated capacity. These rated currents, etc., can also be said to be limit values ​​of current, etc., compensated by the manufacturer to ensure the safe use of electrical products. Furthermore, ratings can also be said to be usage limits or conditions under which safe and proper operation is guaranteed for equipment (electrical and electronic equipment) or devices. In the present invention, when the current is alternating current, the current value, voltage value, power value, and capacity value may be RMS values. Furthermore, in this invention, "electrical circuit" refers to a device that carries electricity (current), consisting of a conductor such as copper, aluminum, silver, gold, or nichrome covered with an insulating material, and includes general cables and wires. Furthermore, the designated circuit on which the measurement system 1 measures current values, etc., is not particularly limited, but for example, it may be a three-phase three-wire (3φ3W) circuit like the system G that supplies power such as 6600V or 22000V at 60Hz or 50Hz, or it may be a single-phase two-wire (1φ2W) or single-phase three-wire (1φ3W) circuit that supplies power, or for example, the busbar circuit 70 or branch circuit 80 described later.

[0020] <Current Sensor 2> As shown in Figures 1-5, the current sensor 2 is a sensor device that is attached to a predetermined circuit and outputs a sensor current D with a current value corresponding to the current value flowing through that circuit. The sensor current D output from the current sensor 2 can be said to be a current-transformed output current that is smaller in current value (lower current value) than the high-voltage AC current (its current value) flowing through that circuit. The specific configuration of the current sensor 2 is not limited, but it may be a fluxgate type (open-loop or closed-loop type, etc.), a Hall element type (open-loop or closed-loop type, etc.), a CT (Current Transformer) type, or a Rogowski coil type, for example. The current sensor 2 does not have any particular limitations on the current transformation ratio between the primary side (the predetermined circuit side) and the secondary side (the output side from the current sensor 2), but it may be, for example, 10:1 or more and 5000:1 or less, or 100:1 or more and 4000:1 or less, (3000:1, etc.). In other words, if the current transformation ratio between the primary and secondary sides of the current sensor 2 is 3000:1, then even if the current flowing through the circuit being measured is very large, for example, 150A, the current output from the current sensor 2 will be approximately 0.05A (50mA). Furthermore, there are no particular limitations on the detectable range of the current sensor 2; for example, it could be between 0.01A and 5.00A, between 1A and 200A, or between 0A and 20000A.

[0021] Such a current sensor 2 can be attached to any position relative to a given circuit, but for example, it may be attached to the output circuit (so to speak, the secondary circuit) of the instrument current transformer 25 installed in the bus circuit 70 inside the grid interconnection panel 20 (grid interconnection panel enclosure 20') described later, or it may be attached directly to the bus circuit 70 described later. In particular, if the current sensor 2 is attached to the secondary circuit of the instrument current transformer 25, as long as the current transformation ratio between the primary side (bus circuit 70 side or branch circuit 80 side) and the secondary side of the instrument current transformer 25 is known, the current value of the current flowing in the said secondary circuit can be measured, and based on that current value, the current value of the current flowing in the bus circuit 70 or branch circuit 80 can also be measured. Furthermore, if the current sensor 2 is attached to the secondary circuit of the instrument current transformer 25, or if the current sensor 2 is directly attached to the busbar circuit 70, and as long as the current sensor 2 can detect the current value of the busbar circuit 70, then the voltage value (potential) of the busbar circuit 70 is approximately the same potential as that of the system G (6600V or 22000V, etc.). Therefore, it can be said that the product of the current value of the busbar circuit 70 detected by the current sensor 2 and the voltage value of the busbar circuit 70 or branch circuit 80, which is approximately the same potential as that of the system G, is the power received from the system G (received power). Furthermore, the current sensor 2 may be attached to two of the three-phase, three-wire (3φ3W) circuits, including the secondary circuit of the instrument current transformer 25 and the busbar circuit 70.

[0022] Such a current sensor 2 may be an open / close type current sensor 2 that can be attached to a predetermined circuit without interrupting the circuit. In this case, the current sensor 2 can be easily retrofitted by opening and closing itself without interrupting the predetermined circuit that is to be measured. The shape of the housing of the switchable current sensor 2 is not particularly limited, but for example, it may be roughly rectangular, and it may have a hole (electrical circuit hole) that penetrates through the middle of this roughly rectangular shape. In this case, the predetermined electrical circuit to be measured enters the electrical circuit hole in the housing of the open / close type current sensor 2, and the other end of the part surrounding this electrical circuit hole opens and closes around one end as an axis. In other words, the other end of the housing of the open / close type current sensor 2 is opened, a predetermined electrical circuit to be measured is placed in the circuit hole, and then the other end of the housing is closed. Furthermore, the switchable current sensor 2 may have a fixing member such as a stopper to fix a predetermined electrical circuit. Such a current sensor 2 may be present only once in a single measurement system 1, but it may also be present in multiples.

[0023] <Sensor cable 3, forward sensor cable 3a, return sensor cable 3b> As shown in Figures 1 to 5, the sensor cable 3 is a cable that carries at least the sensor current D from the current sensor 2 described above, and can be said to be an electrical circuit that connects the current sensor 2 and the measurement unit 4, which will be described later. The sensor cable 3 is fitted with a shield 5, which will be described later. Furthermore, the sensor cable 3 may include a forward sensor cable 3a and a return sensor cable 3b, which will be described later (that is, the sensor cable 3 may be a pair of forward and return cables). Therefore, since the sensor cable 3 not only carries the sensor current D from the current sensor 2 in the return sensor cable 3b, but also carries the current from the measurement unit 4 in the forward sensor cable 3a, the sensor cable 3 as a whole can be said to be a cable that carries at least the sensor current D from the current sensor 2.

[0024] The forward sensor cable 3a is a cable that carries current from the measurement unit 4 described above to the current sensor 2, and is connected to the high-potential current measurement terminal 4Aa, which will be described later. The return sensor cable 3b is a cable that carries current from the current sensor 2 to the measurement unit 4, and is connected to the low-potential current measurement terminal 4Ab, which will be described later. In particular, if the current measurement terminal 4A described later includes a high-potential current measurement terminal 4Aa and a low-potential current measurement terminal 4Ab, at least the forward sensor cable 3a and the return sensor cable 3b (so to speak, a pair of return sensor cables 3) may be covered by one conductive shield layer 5a (in other words, one shield 5). In addition, two pairs of return sensor cables 3 may be covered by one conductive shield layer 5a, or three or more pairs of return sensor cables 3 may be covered by one conductive shield layer 5a. The length of the sensor cable 3 is not particularly limited, but for example, it may be 20m or more and 2000m or less, preferably 30m or more and 1500m or less, and even more preferably 50m or more and 1200m or less (such as 100m, 500m, or 1000m). In this invention, the "length of the sensor cable 3" is approximately twice the distance between the current sensor 2 and the measurement unit 4, since the sensor cable 3 is basically a pair for reciprocating. However, if the pair or multiple pairs of sensor cables 3 are covered by a single conductive shield layer 5a, the apparent length can be said to be approximately half the actual length of the sensor cable 3.

[0025] The specific configuration of such a sensor cable 3 is not particularly limited, but for example, the value of the current flowing through the sensor cable 3 is related to the current transformation ratio between the primary and secondary sides of the current sensor 2 described above, and may be, for example, 1A or less, and the upper limit of the current flowing through the sensor cable 3 is, for example, 1A (1000mA) or less, preferably 500mA or less, more preferably 100mA or less, and even more preferably 50mA or less (it may be a few mA, or 1mA to 20mA or less, etc.). On the other hand, there are no particular limitations on the lower limit of the current flowing through the sensor cable 3, but for example, it may be 0.001 mA or more, preferably 0.010 mA or more, more preferably 0.100 mA or more, and even more preferably 0.500 mA or more. The upper and lower limits of the current flowing through the sensor cable 3 described above can be combined with each other, for example, between 0.001mA and 1000mA, or between 0.001mA and 500mA. Based on the current value flowing through this sensor cable 3, the measurement unit 4, which will be described later, will calculate the current value flowing through the predetermined circuit that is the target of measurement. Such a sensor cable 3 may exist as a single unit in a measurement system 1, or it may exist in multiple units, and may be the same number as the current sensors 2 described above. In addition, the sensor cable 3 may be a twisted pair cable, and this twisted pair sensor cable 3 may be covered with a shield 5 described later.

[0026] <Measurement Unit 4> As shown in Figures 1-3 and 5, the measurement unit 4 is the part that measures at least the current value of the current flowing through the circuit described above based on the sensor current D input via the sensor cable 3 described above. The measurement unit 4 is equipped with a current measurement terminal 4A to which the sensor cable 3 is connected, and the shield wire 5b of the shield 5, which will be described later, is connected to this current measurement terminal 4A. The measuring unit 4 is grounded. The current measurement terminal 4A of the measurement unit 4 may include a high-potential current measurement terminal 4Aa and a low-potential current measurement terminal 4Ab. The forward sensor cable 3a described above is connected to the high-potential current measurement terminal 4Aa, and at the same time, the shield wire 5b of the shield 5, which will be described later, is also connected to it. Furthermore, the measurement unit 4 is built into the system housing 7 described above.

[0027] In particular, if the current measurement terminal 4A includes a high-potential current measurement terminal 4Aa and a low-potential current measurement terminal 4Ab, the measurement unit 4 may be grounded from a terminal that is approximately the same potential as the low-potential current measurement terminal 4Ab. To illustrate this in detail in Figure 2, inside the measurement unit 4, a resistor (e.g., 20Ω) 4' exists between the high-potential current measurement terminal 4Aa and the low-potential current measurement terminal 4Ab. The sensor current D (e.g., 1.6mA) from the current sensor 2 is input from the high-potential current measurement terminal 4Aa via the forward sensor cable 3a, flows through resistor 4', and then flows back to the current sensor 2 via the return sensor cable 3b from the low-potential current measurement terminal 4Ab. At this time, the voltage value generated across resistor 4' is read by the central processing unit (CPU) via the A / D converter in the measurement unit 4, and the current value of the sensor current D is measured by dividing the read voltage value by the resistance value of resistor 4'. In the sensor cable 3, the forward path is the side from which the current flows from the current sensor 2 to the measurement unit 4, and the return path is the side from the measurement unit 4 back to the current sensor 2. Furthermore, as shown in Figure 2, the measurement unit 4 is grounded from a terminal that is at approximately the same potential as the low-potential current measurement terminal 4Ab (which can also be called the GND of the circuit board in the measurement unit 4).

[0028] In addition, the measurement unit 4 may be configured to measure not only the current value of the current flowing through a predetermined circuit, but also the voltage value of the current flowing through a predetermined circuit. In this case, the measuring unit 4 may also be equipped with a voltage measuring terminal 4B to which a predetermined circuit is connected, and may also measure the voltage value of the current flowing through the circuit based on the current input from the circuit to the voltage measuring terminal 4B. There are no particular limitations on the value of the voltage (voltage of the circuit to be measured) input to the measurement system 1 (especially the measurement unit 4, etc.) via the voltage measurement terminal 4B. For example, if the circuit is a three-phase three-wire or single-phase two-wire, the voltage in the secondary circuit that passes from the busbar 70 or branch circuit 80 through a transformer (for example, the instrument transformer (distribution transformer) 63c in the distribution panel 63 of the power generation device 60 described later, or the instrument transformer (high-voltage transformer) 23 in the grid connection panel 20 described later) may be 110V, 220V, 440V at 60Hz or 50Hz, or if it is a single-phase three-wire, it may be 100V or more and 200V or less at 60Hz or 50Hz. In other words, the voltage values ​​of the currents flowing through the busbar 70 and branch circuits 80 (6600V, 22000V, etc.) are higher than the voltage values ​​flowing through the circuit being measured. However, if the transformation ratio between the primary side (busbar 70 side and branch circuit 80 side) and the secondary side of the distribution transformer 63c and high-voltage transformer 23 is known, then by connecting the secondary side circuit of the distribution transformer 63c and high-voltage transformer 23 to the voltage measurement terminal 4B of the measurement unit 4, the voltage value of the current flowing through that secondary side circuit can be measured, and based on that voltage value, the voltage value of the current flowing through the busbar 70 and branch circuits 80 can also be measured. Furthermore, if the circuit being measured is a three-phase, three-wire circuit, there will be three voltage measurement terminals 4B connecting the three wires. Of these three wires, one (such as the S phase) may be grounded (e.g., Class B grounding or neutral point grounding).

[0029] Furthermore, in Figure 2, regarding the voltage measurement terminal 4B, multiple predetermined resistors 4" are provided between the voltage measurement terminal 4B and a terminal at approximately the same potential as the low-potential current measurement terminal 4Ab in the measurement unit 4 (so to speak, the GND of the circuit board of the measurement unit 4). When current from a predetermined circuit flows through each resistor 4" via the voltage measurement terminal 4B, the voltage value generated at the resistor 4" closest to GND among these multiple resistors 4" is read by the central processing unit (CPU) via the A / D converter in the measurement unit 4, and the voltage value in the predetermined circuit is measured based on the read voltage value.

[0030] Furthermore, the measurement unit 4 may also measure the power value in a predetermined circuit from the product of a current value measured based on a sensor current D input from a current sensor 2 attached to a predetermined circuit via a sensor cable 3 and a current measurement terminal 4A, and a voltage value measured based on a current input from the predetermined circuit via a voltage measurement terminal 4B. The specific configuration of the measurement unit 4 is not particularly limited, but it may be electronic, mechanical, three-phase (a system that measures two phases out of three wires), or single-phase. Hereafter, the measurement unit 4 will be described assuming that it is primarily electronic and three-phase. Furthermore, the current, voltage, and power values ​​measured in the predetermined circuit by the measurement unit 4 may be output to the control device 12 of the power generation device 60 (described later), or they may be output to a remote computer or other terminal via the internet or telephone line. Such a measuring side section 4 may exist as a single unit in a single measuring system 1, or it may exist as a multiple unit.

[0031] <Shield 5> As shown in Figures 1-5, the shield 5 is attached to the sensor cable 3 described above and comprises a conductive shielding layer 5a that covers the sensor cable 3 and a shielding wire 5b that is electrically connected to the conductive shielding layer 5a. The shielded wire 5b is connected to the current measurement terminal 4A of the measurement unit 4 described above. In particular, if the current measurement terminal 4A described above includes a high-potential current measurement terminal 4Aa and a low-potential current measurement terminal 4Ab, then at least the forward sensor cable 3a and the return sensor cable 3b described above may be covered with a single conductive shield layer 5a, and the shield wire 5b may be connected to the low-potential current measurement terminal 4Ab.

[0032] The specific configuration of the conductive shield layer 5a is not particularly limited, but for example, the conductive shield layer 5a is placed between the conductor (core wire) and the sheath of the sensor cable 3 and covers the periphery of the core wire. Its material may be a braided strand of metal such as copper, aluminum, tin, or tin-plated soft copper, or an unbraided spiral winding of metal tape such as copper, aluminum, tin, or tin-plated soft copper, or it may be a layer of conductive polymer. This conductive shield layer 5a may also be further covered by a jacket. There are no particular limitations on the specific configuration of the shield wire 5b. For example, the shield wire 5b may be present at only one end of the conductive shield layer 5a. In this case, the conductive shield layer 5a will be grounded at one end by grounding the shield wire 5b via the measurement unit 4. Alternatively, the shield wire 5b may be present at both ends of the conductive shield layer 5a. In this case, the conductive shield layer 5a will be grounded at both ends by grounding the shield wire 5b. Furthermore, the conductive shielding layer 5a (so to speak, the shield) does not need to cover the end of the sensor cable 3 on the current sensor 2 side; the end of the sensor cable 3 may be exposed (see Figure 4). Such shields 5 may exist as a single unit in a single measurement system 1, or there may be multiple shields, and the number of shields may be the same as the current sensors 2 and sensor cables 3 mentioned above.

[0033] <Relay section 6> As shown in Figures 1-3 and 5, the relay unit 6 is part of the measurement system 1 described above, and performs relay operations on electrical and electronic equipment outside the control panel enclosure 10' of the control panel 10, which will be described later, according to the measured values ​​(current values, voltage values, power values) measured by the measurement unit 4 based on the sensor current D described above. It can also be said that the measurement system 1 has a relay function. Here, in this invention, "according to the measured value measured by the measurement unit 4" means that the following relay operation is performed when the measured value becomes greater than or equal to a predetermined value (threshold) (exceeds the threshold) or when it becomes less than or equal to a predetermined value (threshold) (falls below the threshold). Furthermore, the predetermined threshold may be, for example, if the measured value is a power value (especially reverse power), then 1% to 10% (preferably 1.5% to 5%, or 5%) of the power flowing from grid G ​​to grid interconnection panel 20 (so to speak, received power) in the power plant 100 described later, or the predetermined threshold may be 0kW. More specifically, for example, if the current value of the three-phase three-wire power flowing from system G to the grid interconnection panel 20 (received power) is 50A and the voltage value is 6600V, the received power will be √3 × 50 × 6600 = 571576.766···W ≈ 571.6kW. 5% of this received power is 571.6kW × 0.05 ≈ 28.6kW, and this 28.6kW becomes the predetermined threshold.

[0034] Furthermore, "according to the measured value measured by the measurement unit 4" includes not only cases where the next relay operation is performed immediately after the measured value exceeds a predetermined value (threshold), but also cases where the next relay operation is performed after a predetermined time has elapsed. Furthermore, the predetermined time is defined as, if the measured value is a power value (especially reverse power), then, for example, in the power plant 100 described later, if a reverse power greater than 5% of the received power (e.g., 28.6 kW) is generated, the predetermined time will be 0.1 seconds to 15.0 seconds, 0.5 seconds to 5.0 seconds, 1.0 second or more, or 2.0 seconds or more (e.g., 2.0 seconds) after the occurrence of this value of reverse power (that is, if 2 seconds have passed since the reverse power reached the threshold of 28.6 kW or more, the next relay operation will be performed). In the present invention, "relay operation" means, for example, in the power plant 100 described later, an operation to interrupt any of the circuits from the power generation device 60 to the grid G ​​(to interrupt any of the circuit breakers in the said circuit (for example, the power generation connection circuit breaker 51 described later)), or, if the power generation device 60 has a converter 62 described later, stopping the conversion of the converter 62. Furthermore, the circuit breaker may be configured to trip via a tripping coil or the like in response to a signal from the control device 12 (or measurement system 1), which will be described later.

[0035] The specific configuration of the relay section 6 is not particularly limited, but it may be a contact type (electromagnetic type) using an electromagnet or a contactless type using a semiconductor element. Furthermore, if it is an electromagnetic type, 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 polarized relay type with a permanent magnet in parallel with the electromagnet. Such a relay unit 6 may exist as a single unit (single element) in a single measurement system 1, or it may exist as a multiple unit (multiple elements). Furthermore, the relay unit 6 is also built into the system housing 7 described above, so if there are multiple relay units 6 in a single measurement system 1, then multiple relay units 6 are built into a single system housing 7. Hereafter, the relay section 6 will be described assuming that there are mainly multiple (for example, two elements) of them in one measurement system 1.

[0036] <Control panel 10> As shown in Figure 3, the control panel 10 contains the measurement system 1 described above and the energy storage unit 11, which will be described later, inside its panel casing 10', and can also be called a control box. Other equipment contained within the control panel 10' enclosure 10' is not particularly limited, but may include, for example, the control device 12 (described later), the ground fault overcurrent relay 13, and the energy meter, or it may also include other devices such as overcurrent relays, autotransformers, outlets, undervoltage relays, capacitor tripping power supplies, and monitoring devices (devices that monitor the amount of power generated (energy) by the power generation unit 61 (described later) and the amount of energy converted by the conversion unit 62). The current sensor 2 of the measurement system 1, as described above, is a device installed inside the grid connection panel 20 (described later), but it can also be said to be a device on the control panel 10 side. Such a control panel 10 may be attached to a distribution board 63 (distribution board enclosure 63a) described later, or to a frame that supports a solar power generation unit 61 (panel-shaped solar cell 61a) described later. Furthermore, if the control panel 10 has a measurement system 1 inside the panel enclosure 10', the measurement system 1 is equipped with the relay unit 6 described above, and the measurement system 1 performs relay operations on electrical and electronic equipment outside the panel enclosure 10' (such as any circuit breaker in the circuit from the power generation device 60 to the system G (such as the power generation connection circuit breaker 51) or the converter unit 62 of the power generation device 60) according to the measured value measured by the measurement unit 4 based on the sensor current D, so it can be said that the measurement system 1 is controllable to electrical and electronic equipment outside the panel enclosure 10'. Furthermore, while the control panel 10 can be considered part of the power generation device 60 described later, it may also be installed separately from the power generation device 60, in which case the control panel 10 can be considered not to be part of the power generation device 60. The following provides a detailed explanation of the control panel enclosure 10' of the control panel 10.

[0037] <Control panel enclosure 10' of control panel 10> As shown in Figure 3, the control panel enclosure 10' of the control panel 10 can also be called the control panel enclosure 10' or the panel box 10', and it houses equipment such as the measurement system 1, the energy storage unit 11, and the control device 12 inside. The specific configuration of the control panel enclosure 10' is not particularly limited, but for example, it may have mounting fixtures that are roughly ∠-shaped in side view for mounting equipment such as the control device 12 diagonally to the rear circuit board inside the control panel enclosure 10', or it may have mounting fixtures that are roughly perpendicular to the rear circuit board inside the control panel enclosure 10' for mounting equipment such as the measurement system 1 and the energy storage unit 11. In addition, the control panel enclosure 10' may be equipped with wiring, wiring ducts, wiring fasteners, etc., and through holes for inserting wiring into and out of the control panel enclosure 10' may be provided on the lower surface. The shape of the control panel enclosure 10' may be approximately rectangular or approximately cubic. The control panel enclosure 10' may have a door that can be opened and closed on the front side; that is, in the control panel enclosure 10', the side with the door is the front side, and the opposite side (the back side of the main body 10 of the control panel enclosure 10') is the rear side. Furthermore, the door of the control panel enclosure 10' may be detachable from the main body of the control panel enclosure 10', and the door may open horizontally, but it may also open like double doors (multiple doors on one control panel enclosure 10', with these multiple doors opening to the left and right), or open vertically (the door opens upwards). In addition, the control panel enclosure 10' may have a visor portion that protrudes forward from its top surface.

[0038] <Energy storage unit 11> As shown in Figure 3, the energy storage unit 11 is the part that supplies power to the measurement system 1 described above, and is located inside the panel housing 10' of the control panel 10 described above. The energy storage unit 11 is, so to speak, the part that stores energy, and even in the event of a power outage or voltage fluctuation, it continues to supply power to the measurement system 1 mentioned above, the control device 12 described later, the ground fault overvoltage relay 13, etc. The energy storage unit 11 may be, for example, an uninterruptible power supply (UPS) as described later, or it may be a capacitor (an electronic component that stores electrical energy, also called a capacitor, which can be said to continue supplying power to the measurement system 1, control device 12, ground fault overvoltage relay 13, etc. for several seconds in the event of a power outage). In addition, the energy storage unit 11 may be a battery such as a lead-acid battery, lithium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery, or it may be a device that stores hydrogen produced by electrolysis of water using the power generated from the power generation unit 61 of the power generation device 60 described later, and extracts power using a fuel cell or the like when needed, or it may be a device that stores energy as kinetic energy using a flywheel or the like, or stores energy as potential energy using a water pump. Hereafter, the energy storage unit 11 will be described primarily as an uninterruptible power supply.

[0039] <Control device 12> As shown in Figure 3, the control device 12 is a device that controls the converter 62 of the power generation device 60 and the grid connection panel 20, which will be described later. For example, it controls the output of the converter 62 (by giving the converter 62 an output target value) based on the power received from the grid G ​​to the grid connection panel 20 (received power), the power output from the power generation device 60 (converter 62), the power consumption of the load 40, etc. It is connected to the ground fault overvoltage relay 13 and controls the converter 62 by receiving a stop signal output from the ground fault overvoltage relay 13 to stop the conversion. The control device 12 may also be a smart logger, a sequencer, a computer, etc. In a single power plant 100, there may be one or more control devices 12. The power supply for the control device 12 is connected to the energy storage unit 11, such as the uninterruptible power supply described above, and is input from the uninterruptible power supply. Furthermore, monitoring, setting changes, and operation of the control device 12 may be performed by the user directly, but may also be performed remotely via the internet, telephone lines, etc.

[0040] <Ground fault overcurrent relay 13> As shown in Figure 3, the Over Voltage Ground Relay (OVGR) 13 receives a zero-sequence voltage output current (a lower voltage zero-sequence voltage output current corresponding to the zero-sequence voltage generated on the branch circuit 80 side, etc.) output from the zero-sequence voltage detector 63d of the power generation device 60, which will be described later. When this zero-sequence voltage output current exceeds a certain value (the value of the operating voltage) for a certain period of time (operating time of approximately 1 second, etc.), the OVGR outputs a stop signal, such as stopping the conversion of the converter 62 of the power generation device 60, which will be described later. The output signal from the ground fault overvoltage relay 13 is input to the control device 12 of the conversion unit 62 as described above. Alternatively, it may be input directly to the conversion unit 62 or to a circuit breaker of the low-voltage distribution circuit, as described later, to trip the low-voltage distribution circuit. In one power plant 100, the number of ground fault overvoltage relays 25 is the same as the number of zero-sequence voltage detectors 63d described above, and the number may be one or more. The power supply for the ground fault overvoltage relay 13 is connected to the energy storage unit 11, such as the uninterruptible power supply mentioned above, and is input from the energy storage unit 24.

[0041] <Power Plant 100> As shown in Figure 3, the power plant 100 is a plant equipped with the measurement system 1 described above, and also includes the control panel 10 described above, the grid connection panel 20 (described later), loads 40, power generation equipment 60, busbars 70, branch circuits 80, etc. Furthermore, the power plant 100 may also have a power generation connection panel 50. In the power plant 100, the current sensor 2 described above is attached to the secondary circuit of the instrument current transformer 25 installed in the busbar circuit 70 inside the grid interconnection panel 20, so that the measurement unit 4 of the measurement system 1 measures the current value of the current flowing through the busbar circuit 70. Simultaneously, in the power plant 100, the secondary circuit of the instrument transformer 63c installed in the branch circuit 80 of the power generation device 60 is connected to the voltage measurement terminal 4B of the measurement system 1, so that the measurement unit 4 of the measurement system 1 measures the voltage value of the current flowing through the branch circuit 80. Based on these factors, the measurement unit 4 of the measurement system 1 in the power plant 100 measures the power received from the grid G ​​based on the current value of the current flowing through the busbar 70 and the voltage value of the current flowing through the branch circuit 80. The grid connection panel 20, loads 40, power generation connection panel 50, power generation equipment 60, busbars 70, branch lines 80, etc. that make up such a power plant 100 are described below.

[0042] <Grid connection panel 20> As shown in Figure 3, the grid connection panel 20 is a panel that connects to grid G, and it can be said that there is only one such panel in the aforementioned power plant 100, and the equipment that connects to grid G ​​is installed in the grid connection panel 20. The specific configuration of the equipment installed in the grid connection panel 20 (more precisely, its enclosure 20') is not particularly limited, but examples include a Combined Voltage and Current Transformer (VCT) 21 for trading, a disconnect switch (also called a service entrance switch, different from the power generation connection disconnect switch described later in the power generation connection panel 50) 22, a Voltage Transformer (VT, in other words, a high-voltage transformer) 23, a circuit breaker such as a vacuum circuit breaker (in other words, a grid circuit breaker or high-voltage circuit breaker, different from the power generation connection circuit breaker (vacuum circuit breaker) 51 described later in the power generation connection panel 50) 24, a Current Transformer (also called a high-voltage current transformer, different from the power generation connection current transformer described later in the power generation connection panel 50) 25, an overcurrent relay 26, and a High Voltage AC Load Break Switch (LBS). It may also include switches (27), transformers (if they are transformers for general lighting loads 41 described later, they can be called lighting transformers, and if they are transformers for general power loads 42 described later, they can be called power transformers) (28), molded case circuit breakers (MCCB) (29), and spare circuit breakers (30). Furthermore, the equipment installed in the grid connection panel 20 also includes the current sensor 2 of the measurement system 1 in the control panel 10 of the power generation device 60, which will be described later. In addition, the rated capacity of the high-voltage AC load switch 27 (or a general high-voltage AC load switch) is not particularly limited, but may be, for example, 10 kVA or more and less than 2000 kVA, preferably 100 kVA or more and 1500 kVA or less, and more preferably 500 kVA or more and 1000 kVA or less. Similarly, the weight of the high-voltage AC load switch 27 (or a general high-voltage AC load switch) is not particularly limited, but may be, for example, 1 kg or more and less than 15 kg, preferably 2 kg or more and 12 kg or less, and more preferably 3 kg or more and 10 kg or less. Other equipment installed in the grid interconnection panel 20 may include zero-sequence voltage detectors, zero-sequence current transformers, load switches, undervoltage relays, overcurrent relays, power supply circuit breakers, voltmeters, ammeters, single-phase transformers, single-phase transformer circuit breakers, earthing resistors, circuit protectors, voltage test terminals, current test terminals, etc., or it may include circuits for suppressing inrush current, and it may also include lightning arresters, undervoltage relays, overvoltage relays, underfrequency relays (also called frequency reduction relays), overfrequency relays, and energy meters.

[0043] <System connection panel 20 enclosure (system connection panel enclosure) 20', etc.> As shown in Figure 3, the enclosure 20' of the grid connection panel 20 described above can also be called the grid connection panel enclosure 20', and it can be said that at least some of the equipment installed in the grid connection panel 20 described above is built into this grid connection panel enclosure 20'. However, among the equipment installed in the grid connection panel 20, the transformer 28 does not necessarily have to be built into the grid connection panel enclosure 20'; the transformer 28 may be attached to the grid connection panel enclosure 20' from the outside or installed outside the grid connection panel enclosure 20'. Conversely, the transformer 28 may be built into the grid connection panel enclosure 20'. The specific configuration of the grid connection panel enclosure 20' is not particularly limited, but for example, it may be formed in a roughly rectangular parallelepiped shape overall. If the entire grid connection panel enclosure 20' is roughly rectangular in shape, the grid connection panel enclosure 20' may have openable and closable doors (front door, etc.) on each of its side panels (front panel, rear panel, left panel, right panel, etc.). In addition, the grid connection panel enclosure 20' may have a top panel, a bottom panel, etc., in addition to the side panels. The outer surface of the ceiling material of the grid connection panel enclosure 20' may be equipped with a lifting device that can be used to lift it with a crane or the like, and the entire grid connection panel enclosure 20' lifted via this device may be installed (mounted) on a pre-constructed foundation (base). There are no particular limitations on the specific material of this foundation; for example, it may be made of concrete or steel (H-beams), and its specific configuration may also vary. It may be a raft foundation with a uniform thickness, a riser foundation with a recess to create a space below the bottom surface of the grid connection panel enclosure 20', or it may be a foundation consisting of multiple pile members driven into the installation site. Furthermore, if the foundation of the grid connection panel enclosure 20' consists of multiple pile members, the grid connection panel enclosure 20' will be installed on the upper end surfaces of these multiple pile members, which can reduce construction costs. There are no particular limitations on the location where these foundations or the grid connection panel enclosure 20' (grid connection panel 20) itself are installed (installation location), but it may be outdoors of a building such as a store, or indoors or outdoors of a factory, for example. The installation surface at this location may be approximately horizontal, or it may be slanted, and the surface of the installation surface may be approximately flat or it may have irregularities.

[0044] <Load 40> As shown in Figure 3, load 40 is a load (load equipment) that consumes at least the power received from grid G ​​(hereinafter also referred to as "received power"). In other words, the power consumption (capacity) of load 40 may be greater than the value of the received power received from grid G ​​(only a portion of the power consumption of load 40 may be covered by the received power). Load 40 may include, for example, car dealerships or gas stations, car rental shops (rental car companies), chargers in factories and workshops, electrical and electronic equipment that uses electricity (such as general lighting loads 41 like incandescent lamps, fluorescent lamps, and mercury lamps (lighting fixtures), and general power loads 42 like air conditioners, motors, and pumps), or it may include the factory or workshop itself. Furthermore, load 40 may include electrical and electronic equipment that uses electricity in corporate and organizational buildings, offices of individuals, government offices and unions, residences, shops, warehouses, garages, parking lots, bicycle parking areas, school buildings, auditoriums, gymnasiums, research facilities, hospitals and clinics, inns and hotels, theaters, cinemas, stadiums, baseball fields, etc., as well as the offices of companies, etc., themselves, and may also include combinations of these.

[0045] <Power generation connection panel 50> Figure 3 shows the power generation connection panel 50 according to the present invention. This power generation connection panel 50 is a panel that connects the power generation device 60, which will be described later, to the grid connection panel 20 and the load 40 described above. The panel enclosure 50' of the power generation connection panel 50 contains a branch circuit 80 (described later) and a vacuum circuit breaker 51 (described later). In addition, the panel enclosure 50' of the power generation connection panel 50 may also contain a cable head 52 (described later), as well as other devices such as disconnectors, current transformers, and overcurrent relays.

[0046] <Panel enclosure of power generation connection panel 50 (power generation connection panel enclosure) 50'> As shown in Figure 3, the enclosure 50' of the power generation connection panel 50 can also be called the power generation connection panel enclosure 50', and it is attached externally to the side of the enclosure 20' of the grid connection panel 20 (grid connection panel enclosure) 20', and the lower end of the power generation connection panel enclosure 50' is higher than the lower end of the grid connection panel enclosure 20'. In other words, the difference in height between the lower end of the power generation connection panel housing 50' and the lower end of the grid connection panel housing 20' (difference in lower end height) is greater than 0 cm. There are no particular limitations on the specific value of this difference in lower end height, but for example, it may be 5 cm or more and 100 cm or more, preferably 10 cm or more and 70 cm or less, and even more preferably 15 cm or more and 50 cm or less. When attaching the power generation connection panel enclosure 50' to the side of the grid connection panel enclosure 20', a foundation for the power generation connection panel enclosure 50' is not required, and the bottom material of the power generation connection panel enclosure 50' may be floating (separated) from the foundation or mounting surface of the grid connection panel 20 (grid connection panel enclosure 20'). Furthermore, by attaching the panel casing 50' of the power generation connection panel 50, which incorporates a vacuum circuit breaker 51 installed in the branch circuit 80, to the side of the panel casing 20' of the grid connection panel 20 from the outside, and by making its lower end higher than the lower end of the panel casing 20' of the grid connection panel 20, it is not necessary to create a separate foundation for installing the power generation connection panel 50, which incorporates equipment such as the vacuum circuit breaker 51, or to adjust the level of the created foundation with the existing foundation, even when adding a power generation device 60. This reduces costs, the construction period for adding the power generation device 60, and the period during which customers' electricity use is interrupted. The specific configuration of the power generation connection panel enclosure 50' is not particularly limited, but for example, it may be formed in a roughly rectangular parallelepiped shape overall. The power generation connection panel enclosure 50' may include the upper panel enclosure 50A' and the lower panel enclosure 50B', which will be described later, and may also include other panel enclosures or boxes. The upper panel enclosure 50A' and the lower panel enclosure 50B' will be described in order below.

[0047] <Upper panel enclosure 50A'> As shown in Figure 3, the upper enclosure 50A' is an enclosure that constitutes the upper side of the power generation connection enclosure 50' described above, and can be said to be a part of the power generation connection enclosure 50'. The upper panel enclosure 50A' is also attached externally to the side of the panel enclosure (system connection panel enclosure) 20' of the aforementioned grid connection panel 20, and naturally, the lower end of the upper panel enclosure 50A' is higher than the lower end of the grid connection panel enclosure 20'. The specific configuration of the upper panel enclosure 50A' is not particularly limited, but for example, it may be formed in a roughly rectangular parallelepiped shape overall. If the entire upper panel enclosure 50A' is roughly rectangular in shape, the upper panel enclosure 50A' may have an openable door (such as a front door) on its side members (especially the front member, among the front member, rear member, left member, right member, etc.). The door may also be fitted with a handle (such as a lever handle or flush handle), and for example, the door may be locked and unlocked by moving a three-point fixed latch (such as a rod-shaped latch made of stainless steel (SUS)) using this handle. The upper panel enclosure 50A' may have, in addition to side panels, a top panel (upper panel), a bottom panel (lower panel), and so on. The specific configuration of the means for attaching the upper panel enclosure 50A' to the grid connection panel enclosure 20' is not particularly limited, but for example, the power generation connection panel enclosure 50' may be attached to the grid connection panel enclosure 20' by means of fasteners (bolts, nuts, etc.), welding (such as welding the mounting bracket all around), adhesive, or fitting.

[0048] <Lower panel enclosure 50B'> As shown in Figure 3, the lower enclosure 50B' is an enclosure that constitutes the lower part of the power generation connection enclosure 50' described above, and can be said to be a part of the power generation connection enclosure 50'. The lower enclosure 50B' is also attached externally to the side of the enclosure (system connection enclosure) 20' of the grid connection panel 20 mentioned above, and the lower end of the lower enclosure 50B' is naturally higher than the lower end of the grid connection enclosure 20'. Furthermore, the difference in height between the lower end of the lower enclosure 50B' and the lower end of the grid connection enclosure 20' can be said to be the difference in lower end height, which is the difference in height between the lower end of the power generation connection enclosure 50' and the lower end of the grid connection enclosure 20'. The specific configuration of the lower panel enclosure 50B' is not particularly limited, but for example, it may be formed in a roughly rectangular parallelepiped shape overall. If the entire lower panel enclosure 50B' is in the shape of a rectangular parallelepiped, the lower panel enclosure 50B' may have one of its side members (of which the front, rear, left, and right members are particularly important, the front member) that is detachable, and may or may not have an openable door (such as a front door). The lower enclosure 50B' may have, in addition to side panels, top panels, bottom panels, etc. There are no particular limitations on the specific configuration of the means for attaching the lower enclosure 50B' to the grid connection enclosure 20'. For example, the power generation connection enclosure 50' may be attached to the grid connection enclosure 20' by means of fasteners (bolts, nuts, etc.), welding (such as welding the mounting bracket all around), adhesive, or fitting.

[0049] Furthermore, in the upper enclosure 50A' and the lower enclosure 50B', the branch circuit 80, which will be described later, can be said to be located (provided) inside the upper enclosure 50A' and the lower enclosure 50B'. The vacuum circuit breaker 51 and disconnectors, which will be described later, may be placed inside either the upper enclosure 50A' or the lower enclosure 50B'. In this case, if the vacuum circuit breaker 51 incorporates a current transformer or an overcurrent relay, the current transformer or overcurrent relay will also be placed inside either the upper enclosure 50A' or the lower enclosure 50B' (for example, the upper enclosure 50A'). By arranging the branch circuit 80 inside the upper enclosure 50A' and the lower enclosure 50B', and by arranging the vacuum circuit breaker 51 inside either the upper enclosure 50A' or the lower enclosure 50B', even though the vacuum circuit breaker 51 tends to be heavy due to its high capacity limit, if the enclosure containing the vacuum circuit breaker 51 is transported and installed separately from the other enclosure, the workload and working time can be reduced, resulting in a reduction in costs, construction period, and power outage period. In addition, the cable head 52, which will be described later, may be located inside the other of the upper panel enclosure 50A' and the lower panel enclosure 50B'.

[0050] <Power generator connection circuit breaker (vacuum circuit breaker) 51> As shown in Figure 3, the power generation connection circuit breaker 51 is a vacuum circuit breaker (VCB) installed in the branch circuit 80, which will be described later. It is a device that opens and closes the branch circuit 80 (three phases and three wires at once) when high-voltage AC current is flowing through it, and extinguishes the arc inside the vacuum valve. Note that this vacuum circuit breaker 51 is different from the system circuit breaker 24 installed in the grid connection panel 20 mentioned above. The vacuum circuit breaker 51 may also have a current transformer or an overcurrent relay. Furthermore, the vacuum circuit breaker 51 may be operated by an electric spring (capacitor trip) system. The rated capacity of the vacuum circuit breaker 51 is not particularly limited, but may be, for example, 2000 kVA or more and 100000 kVA or less, preferably 2500 kVA or more and 50000 kVA or less, and even more preferably 3000 kVA or more and 10000 kVA or less (such as 4320 kVA). Furthermore, there are no particular limitations on the weight of the vacuum circuit breaker 51, but for example, it may be 15 kg or more and 1000 kg or less, preferably 20 kg or more and 500 kg or less, and even more preferably 25 kg or more and 100 kg or less (such as 32 kg).

[0051] <Cable head 52, other equipment> As shown in Figure 3, the cable head 52 is installed in the branch circuit 80, which will be described later, and is the part of the branch circuit 80 that has been terminated in order to connect to high-voltage equipment such as the vacuum circuit breaker 51 and disconnectors (power generation connection disconnectors) mentioned above. The specific configuration of the cable head 52 is not particularly limited, but for example, the insulation is stripped from the ends of the cables and wires that make up the branch circuit 80, and insulating tape or semiconducting tape is wrapped around them. A branch pipe is then used to branch the branch circuit 80 into three if it is a three-phase three-wire system, or into two if it is a single-phase two-wire system. The cable head 52 may be grounded, and there are no particular limitations on the type of grounding, but for example, it may be Class A grounding. Other equipment built into the enclosure 50' of the power generation connection panel 50 may include, for example, disconnecting switches (DS), ammeters, insulators, reverse power relays (RPR), and power meters (such as power generation meters and power receiving meters).

[0052] <Power generator 60> As shown in Figure 3, the power generation device 60 is a device connected to the grid connection panel 20 and the load 40 via the power generation connection panel 50, and has a power generation unit 61 and a conversion unit 62, which will be described later. In addition, the power generation device 60 may also have a distribution board 63.

[0053] As shown in Figure 3, the power generation unit 61 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 61 may generate electricity using ocean thermal energy, wave power, ocean currents, or tides. In a single power generation device 60, there are no particular limitations on the number of power generation units 61, for example, there may be one or multiple units. Similarly, there are no particular limitations on the power generation capacity of the power generation units 61, for example, it may be 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 61, which generates solar power. The photovoltaic power generation unit 61 is equipped with solar cells 61a, such as panel-shaped cells. In addition, the photovoltaic power generation unit 61 may also have a pyranometer for measuring solar radiation intensity, and a current collector for collecting DC current from solar cells 61a and junction boxes and sending it to a conversion unit 62, which will be described later. There may be multiple solar cells 61a in the photovoltaic power generation unit 61, and these multiple solar cells 61a may be connected in series to form a solar cell string. The photovoltaic power generation unit 61 may also have a junction box to which multiple solar cell strings are connected in parallel, and there may be multiple such junction boxes.

[0054] As shown in Figure 3, the conversion unit 62 is the part that converts the DC current or AC current from the power generation unit 61 described above into a low-voltage AC current. The conversion unit 62 may include an inverter or the like that converts the DC current from the solar cell 61a into AC current, and may also include a controller that controls the voltage and frequency of the AC current converted by the inverter, as well as an air circuit breaker or the like. The conversion unit 62 is also called a power conditioner. In a single power generation device 60, there are no particular limitations on the number of conversion units 62; for example, there may be multiple units (e.g., four or five) or just one. Similarly, there are no particular limitations on the conversion power (capacity) that the conversion unit 62 can convert; for example, it may be 30kW or more and 10,000kW or less, preferably 50kW or more and 5,000kW or less, and even more preferably 100kW or more and 2,000kW or less (e.g., 250kW or 500kW). Furthermore, the conversion power of the conversion unit 62 may be less than the power generation capacity of the photovoltaic power generation unit 61 (in other words, the power generation capacity may be greater than the conversion power), in which case the solar cell 61a can be said to be overloaded relative to the conversion unit 62. In addition, the conversion unit 62 may have undervoltage relays, overvoltage relays, underfrequency relays, or overfrequency relays, or it may have passive or active islanding protection devices.

[0055] As shown in Figure 3, the switchboard 63 is a panel that distributes the electricity generated from the power generation unit 61 via the conversion unit 62 to the grid connection panel 20. It can be said that there is one or more of these panels in one power plant 100, and the switchboard 63 has components that distribute electricity to the grid connection panel 20. The specific configuration of the components of the distribution board 63 is not particularly limited, but it may include, for example, a panel enclosure 63a that houses equipment for distributing power to the grid connection panel 20, or a transformer 63b, and the control panel 10 described above may be attached to the panel enclosure (so to speak, the distribution board enclosure) 63a of the distribution board 63. The specific configuration of the equipment built into the panel enclosure 63a of the distribution panel 63 is not particularly limited, but for example, it may include an instrument transformer (VT, Voltage Transformer, so to speak, a distribution transformer, which is different from the high-voltage transformer 23 of the grid connection panel 20 mentioned above) 63c, a zero-phase voltage detector (ZPD, Zero Phase Potential Device) 63d, etc., and may also include a voltmeter, a low-voltage circuit breaker, a circuit protector, and it can also be said that it includes (part of) the branch circuit 80 described later. The output from the distribution transformer 63c may be output to the measurement system 1 built into the control panel 10 mentioned above, and the output from the zero-phase voltage detector 63d may be output to the ground fault overvoltage relay 13 built into the control panel 10. The transformer (so to speak, a distribution transformer) 63b of the distribution panel 63 is a device that transforms (steps up) the low-voltage AC current from outside the distribution panel enclosure 63a (from the power generation unit 61 through the conversion unit 62) into a higher voltage AC current, and is a so-called transformer (TR). Note that "transformer" is an abbreviation of "transformer". The distribution panel enclosure 63a may be attached to the distribution transformer 63b from above, meaning that the distribution transformer 63b is installed outside the distribution panel enclosure 63a. This eliminates the need for a ventilation fan and auxiliary power supply for the ventilation fan inside the distribution panel enclosure 63a, makes repair and painting of the distribution transformer 63b (main unit) easy, allows for long-term maintenance (for example, 20 years or more), and eliminates the need for assembly work at the installation site after shipment.

[0056] <Bus line 70> As shown in Figure 3, the busbar circuit 70 is the circuit between the system G and the load 40 described above (such as a three-phase three-wire (3φ3W) circuit). Here, in this invention, "busbar circuit 70 between system G and load 40" includes not only the case where the entire circuit between system G and load 40 is the busbar circuit 70, but also the case where at least a portion of the circuit between system G and load 40 (for example, the circuit from system G to the transformer 28 of the system interconnection panel 20) is the busbar circuit 70. In short, any circuit that exists between system G and load 40 can be said to be the busbar circuit 70. Furthermore, if the circuit from system G to the transformer 28 of the system interconnection panel 20 is the busbar circuit 70, then the remaining circuit from the transformer 28 to load 40 can be said to be the low-voltage circuit of the system. Furthermore, the entire circuit between system G and load 40 being a busbar circuit 70 means, for example, that load 40, which has (or has built in) a transformer (step-down transformer), is directly connected to system G by a busbar circuit 70. The potential in this busbar circuit 70 may be the same as the potential in the system G (6600V or 22000V, etc.), and if a transformer 28 (also called a step-down transformer, specifically such as the lighting transformer or power transformer mentioned above) of the system interconnection panel 20 is installed between each load 40 and the busbar circuit 70, then the circuit connecting this transformer 28 (the high-voltage side) and the system G can be said to be the busbar circuit 70. The busbar circuit 70 is equipped with the equipment of the grid interconnection panel 20 described above. To elaborate on each piece of equipment, the busbar circuit 70 may also be equipped with, in order from grid G ​​to load 40, a transformer / current transformer 21 for trading, a service entrance switch 22, a high-voltage transformer 23 (strictly speaking, it is installed in a circuit branched from the busbar circuit 70), a circuit breaker 24, a high-voltage current transformer 25, an overcurrent relay 26 (strictly speaking, it is installed in the output circuit of the high-voltage current transformer 25), a high-voltage AC load switch 27, a transformer 28, and so on. The busbar circuit 70 described above may also be connected to the equipment built into the power generation connection panel 50 (especially the branch circuit 80).

[0057] <Branch circuit 80> As shown in Figure 3, the branch circuit 80 is a circuit (such as a three-phase three-wire (3φ3W)) that branches off from the busbar circuit 70 described above, and is the circuit that connects the power generation device 60 described above to the grid connection panel 20 and load 40 described above. The branch circuit 80 may be connected to the busbar circuit 70. In this case, the potential in the branch circuit 80 will be the same high voltage as the potential in the busbar circuit 70 and the system G (i.e., the branch circuit 80 will be at approximately the same potential as the busbar circuit 70, such as 6600V or 22000V). Therefore, even if the distance between the grid connection panel 20 or the load 40 and the power generation device 60 is large, the branch circuit 80 will be at a high voltage, which reduces cable loss and allows for greater flexibility in the installation location of the power generation device 60 (increasing the options for installation locations). One end of the branch circuit 80 is connected to the busbar circuit 70 (a circuit at any point between the equipment installed in the grid interconnection panel 20 and the load 40 (for example, between the high-voltage current transformer 25 and the high-voltage AC load switch 27)), and the other end of the branch circuit 80 may be connected to the output side of the power generation device 60 (the output side (high voltage side) of the distribution transformer 63b) (on the other hand, the circuit from the input side of the power generation device 60 (the input side (low voltage side) of the distribution transformer 63b) to the converter 62 and the power generation unit 61 can also be said to be a low-voltage distribution circuit). Therefore, the branch circuit 80 may have not only the portion located inside the aforementioned panel housing (power generation connection panel housing) 50' of the power generation connection panel 50, but also a portion that extends beyond the power generation connection panel housing 50'. This extended portion may be the portion between the power generation connection panel 50 (power generation connection panel housing 50') and the distribution panel 63 of the power generation device 60, or a portion located inside the distribution panel 63. As described above, the branch circuit 80 is equipped with the above-mentioned equipment built into the power generation connection panel 50 and the equipment of the power generation device 60 described above. To explain each piece of equipment in detail, the branch circuit 80 may be equipped with the above-mentioned disconnectors, the above-mentioned vacuum circuit breakers 51 (which may also include the above-mentioned current transformers and overcurrent relays), the above-mentioned cable heads 52, and equipment built into the distribution panel housing 63a of the distribution panel 63 (such as a distribution transformer 63c and a zero-sequence voltage detector 63d) in order from the busbar circuit 70 to the distribution panel 63 of the power generation device 60.

[0058] <Tests 1-3> In tests 1 to 3 of the present invention, a comparative configuration is created for the measurement system 1 described above, with test configurations 1 to 3 and a comparative configuration being used in test 1, test configuration 2 being used in test 2, and test configuration 3 being used in test 3. First, we will explain in detail the test configurations 1-3 and the comparative configuration.

[0059] <Test Configuration 1> As shown in Figure 5(a), in test configuration 1, one measurement system 1 has two current sensors 2, two sensor cables 3 (i.e., two pairs of forward sensor cables 3a and return sensor cables 3b), and one shield 5 that covers the two sensor cables 3 together. The measurement unit 4 has two pairs of high-potential current measurement terminals 4Aa and low-potential current measurement terminals 4Ab (corresponding to the R phase and T phase), and one voltage measurement terminal 4B for three-phase three-wire systems. The shield wire 5b of the shield 5 is connected to the low-potential current measurement terminals 4Ab of each pair, and the measurement unit 4 is grounded. The actual length of the sensor cables 3 and shield 5 is 100m (the apparent length is about half of that, approximately 50m), and one of the voltage measurement terminals 4B for three-phase three-wire systems in the measurement unit 4 is grounded. For this measurement system 1, the test equipment of test configuration 1 included a control power supply X1 that supplied power (DC24V) to the measurement system 1, a three-phase generator (three-phase three-wire (3φ3W), constant 110V, 50 / 60Hz switchable, "RX4763" manufactured by NF Circuit Design Block Co., Ltd.) X2, a digital power meter ("2533" manufactured by Yokogawa Electric Co., Ltd.) X3, an RS-232C / RS-485 converter X4, and a personal computer X5.

[0060] <Test Structure 2> As shown in Figure 5(b), in Test Configuration 1, a steel plate X6 was placed under the system housing 7 of the measurement system 1, and the wires from the steel plate X6 were connected to the ground wire from the measurement unit 4. In addition, the three-phase generator X2 was replaced with another three-phase generator (three-phase three-wire (3φ3W), 110V, 4A constant, 50 / 60Hz switchable, formerly manufactured by Keihin Densokuki Co., Ltd. (now Densoku Techno Co., Ltd.), "VBU-100") X2', and the digital power meter X3 was replaced with a noise simulator (manufactured by Noise Research Institute Co., Ltd., "INS-4020") X3'. The circuit outputting noise from this noise simulator X3' was directly connected to the low-potential side of the input circuit to one of the two current sensors 2, and the noise simulator X3 was grounded. This constituted Test Configuration 2. Note that the input from this three-phase generator X2' has an input fluctuation of ±1%.

[0061] <Exam Structure 3> As shown in Figure 5(c), the circuit that outputs noise from the noise simulator X3' in test configuration 2 was connected to a coupling adapter (CA-805B manufactured by Noise Laboratory Co., Ltd.) X3'', and a portion of the shield 5 of the measurement system 1 was covered with this coupling adapter X3'' to form test configuration 3.

[0062] <Comparative Configuration> In the comparative configuration, the shield wire 5b of the shield 5 of the measurement system 1 in test configuration 1 was not connected to the low-potential current measurement terminals 4Ab of each pair, but was directly grounded.

[0063] <Test 1> In Test 1, when a three-phase, three-wire current with measurement reference values ​​of 8000A (100.0%), 4000A (50.0%), 32A (0.4%), 24A (0.3%), 16A (0.2%), and 0A (0.0%) was input to the measurement systems of Test Configuration 1 and the comparative configuration described above, the actual R-phase and T-phase current values ​​measured by each measurement system are shown in Tables 1 to 3 below. When a three-phase, three-wire current with measurement reference values ​​of 96.00MV (100.0%), 48.00MV (50.0%), 0.384MV (0.4%), 0.288MV (0.3%), 0.192MV (0.2%), and 0.00MV (0.0%) was input to each measurement system, the actual power values ​​measured by each measurement system, the errors relative to those reference values, and their respective allowable errors are shown below. Here, the current value of the input three-phase three-wire current is set to 100% from the measurement reference value of 0A to 8000A. For two cases where the input three-phase three-wire current frequency is 50Hz and 60Hz, the current values, power values, and errors of the R phase and T phase were actually measured. Regarding tolerances, the current values ​​for the R and T phases are ±0.5%, but the power values ​​depend on the operating value of the reverse power. More specifically, when the operating value is ≥ 5%, it is ±5%; when the operating value is 1-5%, it is ±10%; and when the operating value is < 1%, it is ±5mA (the actual power value, not a percentage, because the value itself is small). Therefore, the tolerances in Table 3 are listed as ±5% and the range of actual power values ​​corresponding to ±5mA. Furthermore, for the comparative configuration measurement system, when a three-phase three-wire current with measurement reference values ​​of 8000A (100.0%) and 0A (0.0%) was input, the actual R-phase and T-phase current values ​​measured by the measurement system are shown in Tables 1 and 2. Here, in the comparative configuration in Tables 1 and 2, when the measurement reference value is 8000A (100.0%), the fact that the measured value and error are listed within a predetermined range indicates that the measured value fluctuated between 7500 and 8000A, and the error fluctuated between -6.30 and 0.00%, relative to the reference value of 8000A (100.0%).

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] <Evaluation of Test 1> First, as shown in Tables 1 and 2, when the three-phase three-wire current of each reference value for measurement was input to the measurement system 1 of test configuration 1, the error in the measured value for both the R-phase and T-phase current values ​​was at least 0.00% and at most 0.08%, which is well below the allowable error of ±0.5%. By connecting the shield wire 5b of the shield 5 of the sensor cable 3 to the current measurement terminal 4A of the measurement unit 4 and grounding the measurement unit 4, even when the length of the sensor cable 3 was extended to 100m, which is 10 times the approximately 10m at which accuracy was conventionally ensured, very accurate values ​​could be measured, and accuracy was ensured ("Cable extension and ensuring accuracy"). However, when a three-phase, three-wire current of 8000A (100.0%) and 0A (0.0%), which are the reference values ​​for measurement, is input to a measurement system with a comparative configuration in which the shielded wire is directly grounded, the measured value (and therefore the error) fluctuates within a predetermined range. This indicates that even though the input reference current value is constant, the measured value is not stable and is far from being accurate. Furthermore, in a comparative measurement system with the shielded wire directly grounded, even when inputting a three-phase three-wire current with a measurement reference value of 0A (0.0%), the error was 2.00%, which is four times the allowable error. Moreover, when inputting a three-phase three-wire current with a measurement reference value of 0A (0.0%), the maximum error was 6.3%, which is more than 10 times the allowable error, indicating that accuracy is not ensured at all. Furthermore, as shown in Table 3, if the measurement system 1 is configured such that the shield wire 5b is connected to the current measurement terminal 4A of the measurement unit 4 and the measurement unit 4 is grounded, then not only the current values ​​shown in Tables 1 and 2, but also the power values ​​obtained by multiplying the measured voltage values, are within the allowable error range when the reference value of the three-phase three-wire current for all measurements is input, thus ensuring accuracy for the power values ​​as well. Although Table 3 states that the error when inputting a three-phase three-wire current with a reference value of 0.192 MV (0.2%) is -37.50%, as mentioned above, the allowable error of the power value depends on the operating value of the reverse power. The allowable error when the reference value is 0.192 MV (0.2%) is when the operating value < 1% (operating value is less than 1%), so it is sufficient for the measured value to fall within the range of the actual power value equivalent to ±5 mA, rather than being expressed as a percentage. The measured value when the reference value is 0.192 MV (0.2%) is 0.12 MV for both 50Hz and 60Hz, which falls within the allowable error range of 0.10 to 0.28 MV, and can be said to have ensured sufficient accuracy.

[0068] <Exam 2> In Test 2, when square wave impulsive noise (positive and negative polarity) with noise pulse widths of 1 μS and 100 nS was directly input to the low-potential side of the input circuit to the current sensor 2 as noise from the noise simulator X3', the error in the measured value displayed on the display unit 8 of the measurement system 1 and the error in the measured value communicated from the measurement system 1 to the personal computer X5 via the RS-232C / RS-485 converter X4 and displayed on the personal computer X5 are shown in Table 4 below. In this case, the noise is considered to be common-mode noise of the input current. Furthermore, in Test 2, a voltage of 2kV was applied for 2 minutes, and the permissible error was less than ±10% of the measured value (or reference value).

[0069] [Table 4]

[0070] <Evaluation of Test 2> Table 4 shows that for the measurement system 1 of test configuration 2, even if the noise pulse width is 1 μS or 100 nS, and even if the square wave impulsive noise is positive or negative polarity, the errors in the measured values ​​displayed on the display unit 8 of the measurement system 1, and the measured values ​​communicated from the measurement system 1 to the personal computer X5, are less than ±1%, which is well below the permissible error of less than ±10%. By connecting the shield wire 5b of the shield 5 of the sensor cable 3 to the current measurement terminal 4A of the measurement unit 4 and grounding the measurement unit 4, even when square wave impulsive noise is input to or generated in the sensor cable 3, which has been extended to 100 m, ten times the conventional length of approximately 10 m where accuracy was ensured, very accurate values ​​can be measured, ensuring accuracy ("Cable extension and ensuring accuracy").

[0071] <Exam 3> In Test 3, when square wave impulsive noise (positive and negative polarity) with noise pulse widths of 1 μS and 100 nS was input to the measurement system 1 of the Test Configuration 3 described above via the coupling adapter X3'' from the noise simulator X3', the error in the measured value displayed on the display unit 8 of the measurement system 1 and the error in the measured value communicated from the measurement system 1 to the personal computer X5 via the RS-232C / RS-485 converter X4 and displayed on the personal computer X5 are shown in Table 5 below. In this case, the noise can be considered the input current, and in Test 3, a voltage of 2kV was applied for 2 minutes, with an allowable error of less than ±10% of the measured value (or reference value).

[0072] [Table 5]

[0073] <Evaluation of Exam 3> Table 5 shows that, for the measurement system 1 of test configuration 3, similar to test 2, even if the noise pulse width is 1 μS or 100 nS, and even if the square wave impulsive noise is positive or negative, the errors in the measured values ​​displayed on the display unit 8 of the measurement system 1, and the measured values ​​communicated from the measurement system 1 to the personal computer X5, are less than ±1%, which is well below the permissible error of less than ±10%. By connecting the shield wire 5b of the shield 5 of the sensor cable 3 to the current measurement terminal 4A of the measurement unit 4 and grounding the measurement unit 4, even when square wave impulsive noise is input to or generated in the sensor cable 3, which has been extended to 100 m, ten times the approximately 10 m for which accuracy was conventionally ensured, very accurate values ​​can be measured, and accuracy is ensured ("Cable extension and ensuring accuracy").

[0074] Furthermore, in the aforementioned tests 2 and 3, regarding the error, not only the measured values ​​displayed on the display unit 8 of the measurement system 1 were checked, but also the measured values ​​that were transmitted from the measurement system 1 to the personal computer X5 via the RS-232C / RS-485 converter X4 (in other words, a communication cable) and displayed on the personal computer X5 were checked. Therefore, it can be said that once the measurement values ​​are accurately measured by the measurement system 1, they can be checked with very little error on terminals such as remote computers via communication cables, the internet, telephone lines, etc.

[0075] <Other> The present invention is not limited to the embodiments described above. The individual components, or the overall structure, shape, dimensions, etc., of the measurement system 1, control panel 10, power plant 100, etc., can be modified as appropriate in accordance with the spirit of the present invention. The measurement system 1 does not necessarily have to have a relay unit 6 or a display unit 8. Current sensor 2 does not necessarily have to be a switchable type. The measurement unit 4 does not necessarily need to have a voltage measurement terminal 4B. The control panel 10 does not necessarily have a control device 12 inside its enclosure 10'. The panel enclosure 50' of the power generation connection panel 50 does not necessarily include the upper panel enclosure 50A' and the lower panel enclosure 50B', or any other panel enclosures or boxes. In this case, the power generation connection panel 50 can be said to consist of a single panel enclosure 50'. The panel enclosure 50' of the power generation connection panel 50 does not necessarily have to contain at least one of the following: a disconnector, a cable head 52, a current transformer, or an overcurrent relay. The openable doors of the power generation connection panel 50 (such as the upper panel enclosure 50A' or the lower panel enclosure 50B') may be equipped with door stoppers (made of stainless steel, etc.), and the openable doors of the power generation connection panel 50 and the removable front panels may be equipped with gaskets at their openings. The vacuum circuit breaker 51 and disconnectors may be grounded, and there are no particular restrictions on the type of grounding, but for example, Class A grounding is acceptable. In addition, the power plant 100 may have the branch circuit 80 and the vacuum circuit breaker 51 inside the panel enclosure 20' of the grid interconnection panel 20 (that is, they do not have to be inside the panel enclosure 50' of the power generation connection panel 50, which is separate from the panel enclosure 20' of the grid interconnection panel 20). Furthermore, the power plant 100 may have a pole-mounted air switch 100a, described later, between the grid interconnection panel enclosure 20' and the grid G ​​in the busbar circuit 70, and may also have a transformer for trading, an electricity meter for purchased electricity, an electricity meter for sold electricity, and protective relay devices. The power plant 100 may have an energy storage device (not shown), which will be described below.

[0076] <Energy storage device> The energy storage device is a device that stores power from the grid G ​​(received power) and power from the aforementioned power generation device 60 (generated power), and may be installed outside the enclosure of the grid connection panel 20, the power generation connection panel 50, the distribution panel 63 of the power generation device 60, etc. The energy storage device may be, for example, a battery such as a lead-acid battery, lithium-ion battery, nickel-metal hydride battery, or nickel-cadmium battery. It may also be a device that stores hydrogen produced by electrolysis of water using power generated from the power generation device 60, and extracts power using a fuel cell when needed. In addition, it may be a device that stores energy as kinetic energy using a flywheel, stores energy as potential energy using a water pump, or stores energy directly as electrical energy using a capacitor. Such a power storage device may be connected to the busbar circuit 70, and the power stored from this power storage device will be consumed by the load 40 described above. Furthermore, since the storage of energy in the energy storage device and the discharge from the energy storage device are performed using direct current, a conversion unit that converts alternating current to direct current, or converts the direct current from the energy storage device to alternating current to the bus circuit 70, may be connected between the energy storage device and the bus circuit 70. The measurement system 1, the control panel 10, and the power distribution plant 100 related to system G, which have been described so far, will be explained in detail below.

[0077] <System G> As shown in Figure 3, System G is the system that transmits (receives) electricity to the power generation connection panel 50 and the power plant 100, and refers to the entire system for power companies to supply electricity to consumers, and can also be called the power grid. Specifically, System G is equipped with facilities such as substations, transmission lines, and distribution lines, and may also include power plants. Furthermore, System G may have the aforementioned pole-mounted air switches (PAS) 100a, and may also have other equipment such as transformers for trading, electricity meters for purchased electricity, electricity meters for sold electricity, and protective relay devices. The power handled in such a system G can be either AC or DC, but the following explanation will assume it is AC. In power system G, since most of the transmitted power is alternating current, it is transmitted via a three-phase three-wire (3φ3W) system through 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 grid G ​​undergoes voltage transformation (step-down) in several stages near the point of consumption, and after pole-mounted transformers, distribution is also carried out using single-phase two-wire (1φ2W) systems. System G may be a power grid owned by a power company (commercial power grid), or it may be a system or plant internal grid owned independently by an organization such as a company or local government (independent power grid). [Industrial applicability]

[0078] The measurement system, control panel, and power system of the present invention can be used for grid connection panels, loads, power generation connection panels, power generation equipment, etc., whether existing or newly installed. In particular, the measurement system can be used for any electrical electronic equipment or mechanical device other than existing or newly installed grid connection panels, loads, power generation connection panels, and power generation equipment, at least when measuring current values. Regardless of its power output or scale, the power generation device can be used as a solar power generation device, and in addition to solar power generation devices, it can be used as a device that generates electricity using a generator (AC motor, etc.) rotated by wind, hydro, wave, geothermal, etc., and can be used both outdoors and indoors. [Explanation of symbols]

[0079] 1. Measurement System 2 Current Sensor 3. Sensor cable 3a Forward sensor cable 3b Return path sensor cable 4. Measurement Unit 4A measurement section current measurement terminal 4Aa Current measurement terminal on the high-potential side of the measurement unit 4Ab Current measurement terminal on the low-potential side of the measurement section 4B Voltage measurement terminal of the measurement section 5 Shields 5a Conductive shielding layer of the shield 5 Shielded wire 6. Relay section 10 Control Panel 10' Control panel enclosure 11. Energy Storage Unit 20-system interconnection panel 25 Current transformers for instrumentation in grid interconnection panels 40 load 60 Power generation equipment 63c Instrument transformer for power generation equipment 70 Busbar electrical circuit 80 Branch Circuits 100 Power Plants D Sensor current G system

Claims

1. A measuring system that measures at least the current value of the current flowing through a predetermined circuit, The measurement system includes a current sensor (2) attached to the circuit and outputting a sensor current (D) corresponding to the current value of the current flowing through the circuit, a sensor cable (3) through which at least the sensor current (D) from the current sensor (2) flows, and a measurement unit (4) that measures at least the current value of the current flowing through the circuit based on the sensor current (D) input via the sensor cable (3). The measurement unit (4) is equipped with a current measurement terminal (4A) to which the sensor cable (3) is connected. The sensor cable (3) has a shield (5) attached to it. The shield (5) comprises a conductive shielding layer (5a) that covers the sensor cable (3) and a shielding wire (5b) that is electrically connected to the conductive shielding layer (5a). The shield wire (5b) is connected to the current measurement terminal (4A) of the measurement unit (4), thereby providing electrical conductivity to the sensor cable (3). The measurement system is characterized in that the terminal connected to the sensor cable (3) is grounded.

2. The current measurement terminal (4A) of the measurement unit (4) includes a high-potential current measurement terminal (4Aa) and a low-potential current measurement terminal (4Ab), The sensor cable (3) includes a forward sensor cable (3a) that carries current from the measurement unit (4) to the current sensor (2), and a return sensor cable (3b) that carries current from the current sensor (2) to the measurement unit (4). At least the forward sensor cable (3a) and the return sensor cable (3b) are covered by one of the conductive shielding layers (5a), The forward sensor cable (3a) is connected to the high-potential current measurement terminal (4Aa), and the return sensor cable (3b) is connected to the low-potential current measurement terminal (4Ab). The shield wire (5b) of the shield (5) is connected to the current measurement terminal (4Ab) on the low-potential side, thereby providing electrical conductivity to the return sensor cable (3b). The measurement system according to claim 1, characterized in that the measurement unit (4) is at approximately the same potential as the current measurement terminal (4Ab) on the low potential side and the terminal that is conductive to the return-circuit sensor cable (3b) is grounded.

3. The measurement system according to claim 2, characterized in that the current value of the sensor current (D) is measured by dividing the voltage value generated in a resistor (4') provided between the high-potential side current measurement terminal (4Aa) and the low-potential side current measurement terminal (4Ab) inside the measurement unit (4) by the resistance value of the resistor (4').

4. The measurement system according to any one of claims 1 to 3, characterized in that the length of the sensor cable (3) is 20 m or more and 2000 m or less.

5. A control panel having a measurement system (1) according to any one of claims 1 to 3 inside a panel enclosure (10'), The control panel enclosure (10') also contains a power storage unit (11) that supplies power to the measurement system (1). The control panel is characterized in that the measurement system (1) also includes a relay unit (6) that performs relay operations on electrical and electronic equipment outside the panel enclosure (10') according to the measured value measured by the measurement unit (4) based on at least the sensor current (D).

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