Long cable type measurement system, control panel and electric 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 that measure at least the current value of a current flowing through a predetermined electric path. [Background technology]

[0002] BACKGROUND ART Conventionally, there is known a method for renovating an existing structure, in which a building is provided with a power load to which power is supplied from an existing power source (see Patent Document 1). In this method of renovating an existing structure, when renovating the existing structure, a distributed power source and a secondary battery are installed in the existing structure, and a power control panel that controls power for the distributed power source and the secondary battery is installed, and 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 also connected, and after the renovation of the existing structure is completed, the power control panel controls power for 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] Japanese Patent Application Laid-Open No. 2013-027127 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method of renovating an existing structure 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 source and power load, as well as to a newly installed solar power generation system and secondary batteries. By installing this power control panel during renovation, it becomes possible to accommodate the newly installed solar power generation system and secondary batteries regardless of their capacity or quantity," and paragraph 0064 states that "any shortfall in the power generated by the solar power generation system relative to the power load is covered by power charged in the secondary batteries or power supplied from the commercial power source. Here, zero energy control reduces the supply of power from the commercial power source as much as possible," and Figure 8 etc. discloses the "amount of power supplied from the commercial power source." Therefore, when connecting a newly installed power control panel or solar power generation equipment to an existing commercial power source (i.e., a grid or power-receiving equipment) and a power load, it is necessary to always accurately grasp the power from the grid or power-receiving equipment. To this end, a current sensor is attached to the bus circuit between the grid and the power load, and the output current from the current sensor, whose value corresponds to the high-voltage AC current (its current value) flowing through the bus circuit, is output via an output cable to the measuring device inside the power control panel.

[0005] However, because the output cable between the current sensor and the measuring device is susceptible to electrical noise and electromagnetic waves from wiring in existing structures and buildings, as well as electrical equipment such as home appliances, the accuracy of the current value flowing through the output cable could only be ensured up to a length of approximately 10 m in order to grasp the power from the grid or power receiving equipment. Furthermore, in existing structures and buildings, the locations of the grid and power receiving equipment are fixed, so with an output cable that is approximately 10m long, the locations where new power control panels can be installed are very limited, creating the problem of not being able to accommodate the installation of new power control panels, solar power generation equipment, etc. This problem is not limited to cases where a power control panel or a solar power generation device is newly installed in an existing structure or building, but also applies to other cases, such as when a power generation device and its control panel are newly installed in an existing grid interconnection panel that is connected to the grid, or in an existing load connected to that grid interconnection panel.

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

[0007] A measurement system 1 according to the present invention is a measurement system that measures at least the current value of a current flowing in a predetermined electric circuit, and includes a current sensor 2 attached to the electric circuit and outputting a sensor current D having a current value corresponding to the current value of the current flowing in the electric circuit, a sensor cable 3 that at least passes the sensor current D from the current sensor 2, and a measurement unit 4 that measures at least the current value of the current flowing in the electric circuit based on the sensor current D input via the sensor cable 3, wherein the measurement unit 4 includes a current measurement terminal 4A to which the sensor cable 3 is connected, and the sensor cable 3 is attached with a shield 5, the shield 5 including a conductive shield layer 5a that covers the sensor cable 3 and a shield wire 5b that is conducted to the conductive shield layer 5a, the shield wire 5b being connected to the current measurement terminal 4A of the measurement unit 4, and the measurement unit 4 is grounded.

[0008] A second feature of the measurement system 1 according to the present invention is that, in addition to the first feature, 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 an outgoing sensor cable 3a that passes current from the measurement unit 4 to the current sensor 2 and a return sensor cable 3b that passes current from the current sensor 2 to the measurement unit 4, at least the outgoing sensor cable 3a and the return sensor cable 3b are covered with one conductive shielding layer 5a, the outgoing sensor cable 3a is connected to the high-potential side current measurement terminal 4Aa and the return sensor cable 3b is connected to the low-potential side current measurement terminal 4Ab, the shield wire 5b of the shield 5 is connected to the low-potential side current measurement terminal 4Ab, and the measurement unit 4 is grounded from a terminal having approximately the same potential as the low-potential side current measurement terminal 4Ab.

[0009] A third feature of the measurement system 1 according to the present invention is that, in addition to the first or second feature, the length of the sensor cable 3 is not less than 20 m and not more than 2000 m.

[0010] Due to these characteristics, 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, as shown in Tables 1 and 2 below, even if the length of the sensor cable 3 is extended to 100m, which is 10 times the approximately 10m at which accuracy was previously ensured, the accuracy of the measured values ​​is dramatically improved and accuracy is ensured compared to when the shield wire 5b is directly grounded ("Extending the cable and ensuring accuracy"). This "extension of the cable and ensuring accuracy" allows for the significant expansion of the freedom in choosing where to install the control panel 10, etc., even if the location of the system G and power receiving equipment has been decided, in cases where a new power generation device 60 or its control panel 10 is to be installed (connected) to the grid interconnection panel 20 or load 40, or when a new power control panel or solar power generation device is to be installed in an existing structure or building, etc., by using a sufficiently long sensor cable 3, and this increases the adaptability of the control panel 10, power generation device 60, etc. to be installed ("improved adaptability of new installation"). In addition, such a measurement system 1 can be said to be a "long cable type measurement system" because the sensor cable 3 can be made much longer than the conventional length at which accuracy was ensured.

[0011] Furthermore, by connecting the shield wire 5b of the shield 5 to the low-potential side current measurement terminal 4Ab and grounding it from a terminal having approximately the same potential as the low-potential side current measurement terminal 4Ab, it is possible to further "extend the cable and ensure accuracy." The length of the sensor cable 3 is not particularly limited, but may be, for example, 20 m or more and 2000 m or less.

[0012] The control panel 10 of the present invention is a control panel having a measurement system 1 having the above-mentioned first or second characteristic inside a panel housing 10', and the control panel also has a power storage unit 11 inside the panel housing 10' that supplies power to the measurement system 1, and the measurement system 1 also has a relay unit 6 that performs relay operation on electrical and electronic equipment outside the panel housing 10' in accordance with the measurement value measured by the measurement unit 4 based on at least the sensor current D.

[0013] Due to this feature, by having the measurement system 1 and the storage unit 11 inside the panel housing 10' of the control panel 10, the heat-sensitive electrical and electronic equipment such as the measurement system 1 and the storage unit 11, which is an uninterruptible power supply, are less susceptible to the effects of heat from outside the panel housing 10' since they are surrounded by the panel housing 10'.For example, even if they are located 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 below), the risk of failure due to heat from the transformer is reduced ("reduction of failure of heat-sensitive equipment"), and further "improvement of adaptability to new installations" of the control panel 10, power generation device 60, etc. can be achieved. At the same time, by providing the measurement system 1 with a relay unit 6 that performs relay operations on electrical and electronic equipment outside the panel housing 10' according to the measured values, it becomes possible to perform control such as stopping electrical and electronic equipment outside the panel housing 10', such as the conversion unit 62 of the power generation device 60. Here, the measurement system 1 that 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 be said to be just a control panel. In addition, since the sensor cable 3 extending from the control panel 10 can be made much longer than conventional ones, such a control panel 10 can also be called a "long cable type control panel."

[0014] The power plant 100 according to the present invention is a power plant having a measurement system 1 having the first or second feature described above, and the power plant also has a grid interconnection panel 20 that is connected to a grid G, a load 40 connected to the grid interconnection panel 20, a power generation device 60 connected to the grid interconnection panel 20 and the load 40, a bus electric circuit 70 between the grid G ​​and the load 40, and a branch electric circuit 80 that branches off from the bus electric circuit 70 and is connected to the power generation device 60, and the current sensor 2 is attached to a secondary electric circuit of an instrument current transformer 25 provided on the bus electric circuit 70 inside the grid interconnection panel 20, so that the measurement unit 4 of the measurement system 1 can measure the voltage of a current flowing through the bus electric circuit 70. The first feature is that the measurement unit 4 of the measurement system 1 measures the current value, and the measurement unit 4 of the measurement system 1 has a voltage measurement terminal 4B to which a predetermined electric circuit is connected, and also measures the voltage value of the current flowing in the electric circuit based on the current input from the electric circuit to the voltage measurement terminal 4B, and the secondary side electric circuit of the instrument transformer 63c provided in the branch electric circuit 80 in the power generation device 60 is connected to the voltage measurement terminal 4B, so that the measurement unit 4 of the measurement system 1 measures the voltage value of the current flowing in the branch electric circuit 80, and the measurement unit 4 of the measurement system 1 measures the power received from the system G based on the current value of the current flowing in the bus electric circuit 70 and the voltage value of the current flowing in the branch electric circuit 80.

[0015] Due to this feature, the measurement system 1 measures the power received from the system G of the power plant 100 based on the current value of the current flowing in the bus circuit 70, measured by attaching the current sensor 2 of the measurement system 1 to the secondary circuit of the instrument current transformer 25 in the system interconnection panel 20, and the voltage value of the current flowing in the branch circuit 80, measured by connecting the secondary circuit of the instrument transformer 63c in the power generation device 60 to the voltage measurement terminal 4B.Even if the system interconnection panel 20 is far from the power generation device 60, the current value of the current flowing in the bus circuit 70 from the system G can be measured directly using a sensor cable 3 that is longer than conventional, while the voltage value of the current flowing in the branch circuit 80, which has approximately the same potential as the bus circuit 70, can be measured within the nearby power generation device 60, ensuring accuracy in the power received from the system G. At the same time, modification of the circuit in the existing grid interconnection panel 20 is achieved by simply attaching the current sensor 2 to the secondary circuit of the instrument current transformer 25, which simplifies the installation of new control panels 10, power generation equipment 60, etc. Furthermore, the measurement system 1 makes it possible to measure the received power on the grid interconnection panel 20 side on the power generation equipment 60 side, eliminating the need to check the received power on the grid interconnection panel 20 side during test adjustment and maintenance of the power generation equipment 60 (if the grid interconnection panel 20 is located far from the power generation equipment 60, there is a great advantage in not having to check the received power on the grid interconnection panel 20 side). Furthermore, such a power plant 100 can also be said to be a "long cable type power plant" because the sensor cable 3 between the current sensor 2 and the measurement unit 4 in the power plant 100 can be made much longer than conventional lengths. [Effects of the Invention]

[0016] In the measurement system, control panel, and power plant according to the present invention, by connecting the shield wire of the sensor cable shield to the current measurement terminal of the measurement unit and grounding the measurement unit, it is possible to "extend the cable and ensure accuracy," etc. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing a measurement system according to the present invention. [Figure 2]This is a schematic circuit diagram showing details of the sensor cable, measurement unit, and shield in the measurement system. Note that the arrows to the left of the resistor indicated by reference numeral 4' in Figure 2 indicate the flow of current. [Figure 3] 3 is a schematic circuit diagram showing a measurement system, a control panel, and a power plant according to the present invention.The photograph in the upper left of FIG. 3, which serves as a substitute for a drawing, shows the inside of an actual control panel (control panel housing). [Figure 4] This is a photograph used as a substitute for a drawing, illustrating a current sensor attached to the secondary circuit between an instrument current transformer (beyond a bulkhead, etc.) installed on a bus circuit and an overcurrent relay inside the panel housing of a grid interconnection panel, as well as the sensor cable and shield connected to the current sensor. [Figure 5] 1 is a schematic diagram showing the test configurations of the measurement system in Tests 1 to 3, where (a) shows Test Configuration 1, (b) shows Test Configuration 2, and (c) shows Test Configuration 3. Note that the details of the sensor cable 3 in (b) and (c) (such as whether it is an outgoing or returning path) and the details of the current input terminal and voltage input terminal (such as whether it is a high-potential side or a low-potential side) are the same as in (a). DETAILED DESCRIPTION OF THE INVENTION

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

[0019] Here, the current, voltage, power, and capacity in the present invention may be values ​​within a rated range, in which case they can be referred to as rated current, rated voltage, rated power, and rated capacity. These rated currents, etc. can also be referred to as limit values ​​of current, etc. guaranteed by manufacturers to ensure the safe use of electrical appliances, and further, ratings can also be referred to as usage limits or conditions that guarantee the safe and proper operation of devices (electrical and electronic devices) and equipment. When the current in the present invention is an AC current, the current value (current value), voltage value (voltage value), power value (power value), and capacitance value (capacity value) may be effective values. In addition, the term "electrical circuit" in this invention refers to a circuit that allows electricity (current) to flow, and is made of a conductor such as copper, aluminum, silver, gold, or nichrome covered with an insulating coating, and includes common cables and electric wires. Furthermore, the specified electrical circuit on which the measurement system 1 measures current values, etc. is not particularly limited, but may be, for example, a three-phase three-wire (3φ3W) circuit like system G that supplies power at 60 Hz or 50 Hz, such as 6600 V or 22000 V, or a single-phase two-wire (1φ2W) or single-phase three-wire (1φ3W) circuit that supplies power, or may be, for example, a bus electrical circuit 70 or a branch electrical circuit 80, which will be described later.

[0020] <Current sensor 2> 1 to 5, the current sensor 2 is a sensor device that is attached to a predetermined electrical path and outputs a sensor current D having a current value corresponding to the current value of the current flowing through the electrical path. The sensor current D output from the current sensor 2 can be said to be a current-transformation output current of a smaller current (smaller current value) corresponding to the high-voltage AC current (its current value) flowing through the electrical path. The specific configuration of the current sensor 2 is not particularly limited, but may be, for example, a flux gate type (open loop type, closed loop type, etc.), a Hall element type (open loop type, closed loop type, etc.), a CT (Current Transformer) type, a Rogowski coil type, etc. The current transformation ratio between the primary side (the side of the specified electrical circuit) and the secondary side (the output side from the current sensor 2) of the current sensor 2 is not particularly limited, but may be, for example, 10:1 or more and 5000:1 or less, or 100:1 or more and 4000:1 or less (e.g., 3000:1). In other words, if the current transformation ratio between the primary and secondary sides of current sensor 2 is 3000:1, even if the current value flowing through the circuit to be measured is very large, for example, 150 A, the current value output from current sensor 2 will be approximately 0.05 A (50 mA). The detectable range of the current sensor 2 is not particularly limited, and may be, for example, 0.01 A or more and 5.00 A or less, 1 A or more and 200 A or less, or 0 A or more and 20,000 A or less.

[0021] Such a current sensor 2 may be attached at any position relative to a predetermined electric circuit, but may be attached, for example, to an output electric circuit (so to speak, a secondary electric circuit) of an instrument current transformer 25 provided on a bus electric circuit 70 inside a grid interconnection panel 20 (grid interconnection panel housing 20′) described later, or may be attached directly to the bus electric circuit 70 described later. In particular, when the current sensor 2 is attached to an electric circuit on the secondary side of the instrument current transformer 25, as long as the current transformation ratio between the primary side (bus electric circuit 70 side or branch electric circuit 80 side) and the secondary side of the instrument current transformer 25 is known, it is possible to measure the current value of the current flowing in the secondary electric circuit, and based on that current value, it is also possible to measure the current value of the current flowing in the bus electric circuit 70 or the branch electric circuit 80. Furthermore, if the current sensor 2 can detect the current value of the bus bar circuit 70, etc., by attaching the current sensor 2 to the secondary circuit of the instrument current transformer 25 or by attaching the current sensor 2 directly to the bus bar circuit 70, the voltage value (potential) of the bus bar circuit 70 will be approximately the same potential as that of system G (6600V, 22000V, etc.), and therefore it can be said that the product of the current value of the bus bar circuit 70 detected by the current sensor 2 and the voltage value of the bus bar circuit 70 or branch circuit 80 which have approximately the same potential as system G is the power received from system G (received power). Furthermore, if the secondary side electric circuit of the instrument current transformer 25 and the bus electric circuit 70 are three-phase three-wire (3φ3W), the current sensor 2 may be attached to two of the wires.

[0022] Such a current sensor 2 may be an open / close type current sensor 2 that can be attached to a specified electrical circuit without opening the circuit. In this case, the current sensor 2 can be easily retrofitted by opening and closing itself without opening the specified electrical circuit to be measured. The shape of the housing of the open / close type current sensor 2 is not particularly limited either, and may be, for example, a substantially rectangular parallelepiped shape, and may have a hole (electrical path hole) penetrating the middle of this substantially rectangular parallelepiped. In this case, a specific electrical path to be measured is inserted into an electrical path hole in the housing of the open / close type current sensor 2, and one end of the part surrounding this electrical path hole is used as an axis, while the other end opens and closes. That is, the other end of the housing of the open / close type current sensor 2 is opened, a predetermined electric path to be measured is placed in the electric path hole, and then the other end of the housing is closed. Furthermore, the open / close type current sensor 2 may have a fixing member such as a stopper that fixes a predetermined electric path. There may be only one such current sensor 2 in one measurement system 1, but there may also be a plurality of such current sensors.

[0023] <Sensor cable 3, outgoing sensor cable 3a, returning sensor cable 3b> As shown in FIGS. 1 to 5, the sensor cable 3 is a cable through which at least the sensor current D from the current sensor 2 flows, and can be said to be an electrical path connecting the current sensor 2 with the measuring unit 4 described below. The sensor cable 3 is fitted with a shield 5, which will be described later. Furthermore, the sensor cable 3 may include an outgoing sensor cable 3a and an incoming sensor cable 3b (described later) (i.e., the sensor cable 3 may be a pair consisting of an outgoing and an incoming cable (a round-trip pair)). Therefore, the sensor cable 3 not only passes the sensor current D from the current sensor 2 through the incoming sensor cable 3b, but also passes a current from the measuring unit 4 through the outgoing sensor cable 3a. Therefore, the sensor cable 3 as a whole can be said to be a cable that passes at least the sensor current D from the current sensor 2.

[0024] The outgoing sensor cable 3a is a cable that passes a current from the measuring unit 4 to the current sensor 2, and is connected to a high-potential side current measuring terminal 4Aa, which will be described later. The return sensor cable 3b is a cable that passes current from the current sensor 2 to the measurement unit 4, and is connected to a low-potential side current measurement terminal 4Ab, which will be described later. In particular, when the current measurement terminal 4A described later includes a high-potential side current measurement terminal 4Aa and a low-potential side current measurement terminal 4Ab, at least the outgoing sensor cable 3a and the return sensor cable 3b (i.e., a pair of sensor cables 3 going in both directions) may be covered with a single conductive shield layer 5a (in other words, a single shield 5), or two pairs of sensor cables 3 going in both directions may be covered with a single conductive shield layer 5a, or three or more pairs of sensor cables 3 going in both directions may be covered with a single conductive shield layer 5a. The length of the sensor cable 3 is not particularly limited, but may be, for example, 20 m or more and 2000 m or less, preferably 30 m or more and 1500 m or less, and more preferably 50 m or more and 1200 m or less (100 m, 500 m, 1000 m, etc.). In addition, the "length of the sensor cable 3" in the present invention can be said to be approximately twice the distance between the current sensor 2 and the measurement unit 4, since the sensor cable 3 is basically a pair of back-and-forth cables. However, when a pair or multiple pairs of back-and-forth sensor cables 3 are covered with a single conductive shielding layer 5a, the apparent length can also be said to be approximately 1 / 2 (half) of 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, 1 A or less, and the upper limit of the current flowing through the sensor cable 3 may be, for example, 1 A (1000 mA) or less, preferably 500 mA or less, more preferably 100 mA or less, and even more preferably 50 mA or less (a few mA, or 1 mA to 20 mA, etc.). On the other hand, the lower limit of the current flowing through the sensor cable 3 is not particularly limited either, but may be, for example, 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 may be combined with each other, for example, from 0.001 mA to 1000 mA or from 0.001 mA to 500 mA. Based on the value of the current flowing through this sensor cable 3, the measurement unit 4, which will be described later, calculates the value of the current flowing through a predetermined electrical path that is the measurement target. There may be only one such sensor cable 3 in one measurement system 1, but there may also be multiple sensor cables 3, and the number may be the same as the number of the above-mentioned current sensors 2. Alternatively, a twisted pair cable may be used as the sensor cable 3, and this twisted pair cable sensor cable 3 may be covered with a shield 5, which will be described later.

[0026] <Measurement section 4> As shown in FIGS. 1 to 3 and 5, the measurement unit 4 is a part that measures at least the current value of the current flowing in the above-mentioned electrical path based on the sensor current D input via the above-mentioned sensor cable 3. The measurement unit 4 includes a current measurement terminal 4A to which the sensor cable 3 is connected, and a shield wire 5b of the shield 5, which will be described later, is connected to the current measurement terminal 4A. The measuring unit 4 is grounded. The current measurement terminal 4A of the measurement unit 4 may include a current measurement terminal 4Aa on the high potential side and a current measurement terminal 4Ab on the low potential side. The current measurement terminal 4Aa on the high potential side is connected to the above-mentioned outgoing sensor cable 3a, and also to a shield wire 5b of the shield 5, which will be described later. The measurement unit 4 is built into the system housing 7 described above.

[0027] In particular, when the current measurement terminal 4A includes a high-potential side current measurement terminal 4Aa and a low-potential side current measurement terminal 4Ab, the measurement unit 4 may be grounded from a terminal having approximately the same potential as the low-potential side current measurement terminal 4Ab. 2, a resistor (e.g., 20 Ω) 4' is present inside the measurement unit 4 between the high-potential side current measurement terminal 4Aa and the low-potential side current measurement terminal 4Ab. The sensor current D (e.g., 1.6 mA) from the current sensor 2 is input from the high-potential side current measurement terminal 4Aa via the outgoing sensor cable 3a, flows through the resistor 4', and then flows from the low-potential side current measurement terminal 4Ab via the return sensor cable 3b back to the current sensor 2. At this time, the voltage value generated across the resistor 4' is read by a central processing unit (CPU) or the like via an A / D converter or the like in the measurement unit 4, and the value of the sensor current D is measured by dividing the read voltage value by the resistance of the resistor 4'. Note that the outgoing and return paths of the sensor cable 3 are defined as the side from the current sensor 2 to the measurement unit 4 as the outgoing path, and the side from the measurement unit 4 back to the current sensor 2 as the return path. As shown in FIG. 2, the measurement unit 4 is grounded from a terminal (which can be said to be the GND of the substrate in the measurement unit 4) that has approximately the same potential as the current measurement terminal 4Ab on the low potential side.

[0028] Additionally, the measuring unit 4 may be configured to measure not only the current value of the current flowing in a predetermined electrical path, but also the voltage value of the current flowing in the predetermined electrical path. In this case, the measurement unit 4 may be provided with a voltage measurement terminal 4B to which a predetermined electrical circuit is connected, and may also measure the voltage value of the current flowing in the electrical circuit based on the current input from the electrical circuit to the voltage measurement terminal 4B. There are no particular limitations on the value of the voltage (the 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, but for example, if the circuit is three-phase three-wire or single-phase two-wire, the voltage may be 110V, 220V, 440V, etc. at 60Hz or 50Hz in the secondary circuit that passes from the bus circuit 70 or branch circuit 80 through a transformer (for example, the instrument transformer (distribution transformer) 63c in the distribution board 63 of the power generation device 60 described later, or the instrument transformer (high-voltage transformer) 23 in the system interconnection board 20 described later), or if it is single-phase three-wire, it may be 100V or more and 200V or less at 60Hz or 50Hz. In other words, it can be said that the voltage value (6600V, 22000V, etc.) of the current flowing in the bus bar circuit 70 and the branch circuit 80 is high compared to the voltage value flowing in the circuit being measured, but as long as the transformation ratio between the primary side (bus bar circuit 70 side or branch circuit 80 side) and the secondary side in the above-mentioned distribution transformer 63c or high-voltage transformer 23 is known, the secondary side circuit of the distribution transformer 63c or high-voltage transformer 23 can be connected to the voltage measurement terminal 4B of the measurement unit 4, the voltage value of the current flowing in the secondary side circuit can be measured, and based on that voltage value, the voltage value of the current flowing in the bus bar circuit 70 or the branch circuit 80 can also be measured. Furthermore, if the circuit to be measured is three-phase, three-wire, there will also be three voltage measurement terminals 4B connecting the three-wire circuit, and one of the three wires (such as the S phase) may be grounded (such as type B grounding or neutral grounding).

[0029] Also, referring to the voltage measurement terminal 4B in Figure 2, a plurality of predetermined resistors 4" are provided between the voltage measurement terminal 4B and a terminal at approximately the same potential as the current measurement terminal 4Ab on the low potential side in the measurement unit 4 (i.e., the GND of the substrate of the measurement unit 4), and when a current from a predetermined electrical path flows through each resistor 4" via the voltage measurement terminal 4B, the voltage value generated in the resistor 4" closest to the GND among these plurality of resistors 4" is read by a central processing unit (CPU) or the like via an A / D converter or the like in the measurement unit 4, and the voltage value in the predetermined electrical path is measured based on the read voltage value.

[0030] In addition, the measurement unit 4 may measure the power value in a specified electrical circuit from the product of the current value measured based on the sensor current D input from the current sensor 2 attached to the specified electrical circuit via the sensor cable 3 and the current measurement terminal 4A, and the voltage value measured based on the current input from the specified electrical circuit via the voltage measurement terminal 4B. The specific configuration of such a measuring unit 4 is not particularly limited, but may be, for example, an electronic type, a mechanical type, a three-phase type (a method of measuring two phases out of three phases and three wires), or a single-phase type. Hereinafter, the measurement unit 4 will be described as being mainly electronic and three-phase. The current, voltage, and power values ​​measured by the measuring unit 4 in a specified electrical circuit may be output to the control device 12 of the power generation device 60 described later, or each value may be output to a remote computer or other terminal via the Internet, a telephone line, or the like. There may be only one such measuring unit 4 in one measurement system 1, but there may also be a plurality of such measuring units 4.

[0031] <Shield 5> As shown in FIGS. 1 to 5, the shield 5 is attached to the above-mentioned sensor cable 3 and includes a conductive shield layer 5a that covers the sensor cable 3, and a shield wire 5b that is electrically connected to the conductive shield layer 5a. The shielded wire 5b is connected to the current measurement terminal 4A of the measurement unit 4 described above. In particular, when the above-mentioned current measurement terminal 4A includes a high-potential side current measurement terminal 4Aa and a low-potential side current measurement terminal 4Ab, at least the above-mentioned outgoing sensor cable 3a and return sensor cable 3b may be covered with a single conductive shield layer 5a, and the shield wire 5b may be connected to the low-potential side 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 disposed between the conductor (core wire) and sheath of the sensor cable 3, and covers the periphery of the core wire. The material for the conductive shield layer 5a may be a braided strand of metal such as copper, aluminum, tin, or tin-plated annealed copper, or an unbraided spiral winding of metal tape such as copper, aluminum, tin, or tin-plated annealed copper, or a layer of a conductive polymer, and the conductive shield layer 5a may be further covered with a jacket. The specific configuration of the shield wire 5b is not particularly limited, but for example, the shield wire 5b may be present at only one end (one end) of the conductive shield layer 5a, in which case the conductive shield layer 5a becomes one-end grounded by grounding the shield wire 5b via the measuring unit 4, etc. Alternatively, the shield wire 5b may be present at both ends of the conductive shield layer 5a, in which case the conductive shield layer 5a becomes both-end grounded by grounding the shield wire 5b. The conductive shield layer 5a (a shield, so to speak) does not have to cover the end of the sensor cable 3 on the current sensor 2 side, and the end of the sensor cable 3 may be exposed (see FIG. 4). There may be only one such shield 5 in one measurement system 1, but there may also be a plurality of shields 5, and the number of shields 5 may be the same as the number of current sensors 2 and sensor cables 3 described above.

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

[0034] Furthermore, "according to the measurement value measured by the measuring unit 4" includes not only the case where the next relay operation is performed immediately after the measurement value reaches or exceeds a predetermined value (threshold value), but also the case where the next relay operation is performed after a predetermined time has elapsed. Note that, if the measured value is a power value (particularly, reverse power), for example, in the power plant 100 described below, when reverse power greater than 5% of the received power (e.g., 28.6 kW) occurs, the predetermined time is 0.1 to 15.0 seconds, 0.5 to 5.0 seconds, 1.0 to 2.0 seconds (e.g., 2.0 seconds) after the occurrence of reverse power of this value (in other words, when 2 seconds have passed since the reverse power reached the threshold value of 28.6 kW or more, the next relay operation will be performed). In the present invention, "relay operation" means, for example, in the case of the power plant 100 described later, an operation of cutting off any of the electric circuits from the power generation device 60 described later to the system G (cutting off any of the circuit breakers in the electric circuit (for example, the power generation connection breaker 51 described later)), or, if the power generation device 60 has a conversion unit 62 described later, stopping the conversion of the conversion unit 62. The circuit breaker may be configured to be cut off via a trip coil or the like in response to a signal from the control device 12 (or the measurement system 1) described later.

[0035] The specific configuration of the relay unit 6 is not particularly limited, and may be, for example, 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, for example, 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 (the contact opens and closes each time current is passed through the electromagnet), or any other configuration, such as a polarized relay type in which a permanent magnet is provided in parallel with the electromagnet. There may be only one (one element) or multiple (multiple elements) such relay unit 6 in one measurement system 1. The relay unit 6 is also built into the above-mentioned system casing 7, and if there are multiple relay units 6 in one measurement system 1, then multiple relay units 6 will be built into one system casing 7. Hereinafter, it will be described that a single measurement system 1 mainly has a plurality of relay units 6 (for example, two elements).

[0036] <Control Panel 10> As shown in FIG. 3, the control panel 10 has the above-described measurement system 1 and a power storage unit 11 (described later) inside its panel housing 10', and can also be called a control box. The other devices that the control panel 10 has inside the panel housing 10' are not particularly limited, and may include, for example, a control device 12, a ground fault overcurrent relay 13, and a watt-hour meter, which will be described later, as well as an overcurrent relay, an autotransformer, an outlet, an undervoltage relay, a capacitor tripping power supply device, and a monitoring device (a device that monitors the amount of power generated (amount of power) by a power generation unit 61, which will be described later, and the amount of power converted by a conversion unit 62, etc.).The above-mentioned current sensor 2 of the measurement system 1 is a device that is installed inside the grid interconnection panel 20, which will be described later, but 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 housing 63a) described later, or may be attached to a stand that supports a solar power generation unit 61 (panel-shaped solar cell 61a) described later. Furthermore, when the measurement system 1 is located inside the panel housing 10' of the control panel 10, the measurement system 1 is equipped with the above-mentioned relay unit 6, and the measurement system 1 performs relay operation on electrical and electronic equipment outside the panel housing 10' (such as any circuit breaker (such as the power generation connection circuit breaker 51) in the electrical circuit from the power generation device 60 to the system G, or the conversion unit 62 of the power generation device 60) depending on the measurement value measured by the measurement unit 4 based on at least the sensor current D, and it can also be said that the measurement system 1 is capable of controlling electrical and electronic equipment outside the panel housing 10'. The control panel 10 can be said to be included in the power generation device 60 described below, but it may be installed away from the power generation device 60, in which case the control panel 10 can be said to not be included in the power generation device 60. The panel housing 10' of the control panel 10 will be explained in detail below.

[0037] <Control panel 10 enclosure (control panel enclosure) 10'> As shown in Figure 3, the panel housing 10' of the control panel 10 can also be called a control panel housing 10' or a panel box 10', and houses equipment such as the measurement system 1, the storage unit 11, and the control device 12 inside. The specific configuration of the control panel housing 10' is not particularly limited, but for example, it may have a mounting fixture that is approximately angle-shaped in side view, which mounts equipment such as the control device 12 at an angle to the rear board inside the control panel housing 10', or it may have a mounting fixture that mounts equipment such as the measurement system 1 and the storage unit 11 at an approximately right angle to the rear board inside the control panel housing 10'. In addition, wiring, wiring ducts, wiring fasteners, etc. may be provided inside the control panel housing 10', and insertion holes for passing wiring inside and outside the control panel housing 10' may be provided on the lower surface. The shape of the control panel housing 10' may be a substantially rectangular parallelepiped or a substantially cubic shape. The control panel housing 10' may have a door on the front side that can be opened and closed; in other words, the side of the control panel housing 10' where the door is located is the front side, and the opposite side (the back side of the main body 10 of the control panel housing 10') is the rear side. Furthermore, the doors of the control panel housing 10' may be detachable from the main body of the control panel housing 10', and the doors may open horizontally, or may open like a double door (where there are multiple doors for one control panel housing 10' and these doors open to the left and right), or may open vertically (where the doors open upwards). In addition, the control panel housing 10' may have a canopy portion that protrudes forward on the top surface.

[0038] <Storage unit 11> As shown in FIG. 3, the power storage unit 11 is a part that supplies power to the measurement system 1 described above, and is provided inside the panel housing 10′ of the control panel 10 described above. The storage unit 11 is, so to speak, a part that stores electricity and continues to supply power to the above-mentioned measurement system 1, the control device 12 described below, and the earth fault overvoltage relay 13, even in the event of a power outage or voltage fluctuation. The storage unit 11 may be, for example, an uninterruptible power supply device described below, or may be a capacitor (an electronic component that stores (preserves) electrical energy, also known as a condenser, which can be said to continue supplying power to the measurement system 1, control device 12, earth fault overvoltage relay 13, etc. for several seconds during a power outage, etc.). Alternatively, the power storage unit 11 may be a storage battery such as a lead storage battery, a lithium ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery, or may store hydrogen generated by electrolysis of water using the power generated by the power generation unit 61 of the power generation device 60 described below, and extract electricity when needed using a fuel cell or the like, or may be a device that stores electricity as kinetic energy using a flywheel or the like, or stores electricity as potential energy using pumped water. Hereinafter, the power storage unit 11 will be described mainly as an uninterruptible power supply.

[0039] <Control device 12> As shown in FIG. 3 , the control device 12 is a device that controls the conversion unit 62 of the power generation device 60 (described later) and the grid interconnection panel 20. For example, the control device 12 controls the output of the conversion unit 62 (provides an output target value to the conversion unit 62) based on the power (received power) received from the grid G ​​to the grid interconnection panel 20, the power generated by the power generation device 60 (conversion unit 62), the power consumption of the load 40, etc. The control device 12 is connected to the ground fault overvoltage relay 13 and receives a stop signal output from the ground fault overvoltage relay 13 to stop the conversion of the conversion unit 62. The control device 12 may be a smart logger, a sequencer, a computer, etc. One power generation plant 100 may include one or more control devices 12. The power supply of the control device 12 is connected to the power storage unit 11, such as the uninterruptible power supply described above, and is input from the uninterruptible power supply. Furthermore, the monitoring, setting changes, operation, etc. of the control device 12 may be performed by the user directly, or may be performed remotely via the Internet, telephone lines, etc.

[0040] <Ground fault overcurrent relay 13> As shown in FIG. 3, the overvoltage ground relay (OVGR) 13 is a device that receives the zero-phase-sequence voltage output current (a lower-voltage zero-phase-sequence voltage output current corresponding to the zero-phase-sequence voltage generated on the branch electric circuit 80 side, etc.) output from the zero-phase-sequence voltage detector 63d of the power generation device 60, which will be described later, and outputs a stop signal to stop conversion by a conversion unit 62 of the power generation device 60, which will be described later, when the zero-phase-sequence voltage output current exceeds a certain value (value of operating voltage) for a certain time (such as an operating time of about 1 second). The output signal from the earth fault overvoltage relay 13 is input to the above-mentioned control device 12 of the conversion unit 62, but it may also be input directly to the conversion unit 62 or to a circuit breaker of the distribution low-voltage line described below, thereby cutting off the distribution low-voltage line. In one power plant 100, the number of earth fault overvoltage relays 25 is the same as the number of the above-described zero-phase sequence voltage detectors 63d, and the number may be one or more. The power supply for the earth fault overvoltage relay 13 is connected to the power storage unit 11 such as the uninterruptible power supply device described above, and is input from the power storage unit 24.

[0041] <Power Plant 100> As shown in FIG. 3, the power plant 100 is a plant having the above-described measurement system 1, and also has the above-described control panel 10, the grid interconnection panel 20 described later, a load 40, a power generation device 60, a bus line 70, a branch line 80, etc. The power plant 100 may also include a power generation connection panel 50 . In the power plant 100, the above-mentioned current sensor 2 is attached to the secondary circuit of the instrument current transformer 25 provided on the bus circuit 70 inside the system interconnection panel 20, and the measurement unit 4 of the measurement system 1 measures the current value of the current flowing in the bus circuit 70. At the same time, in the power plant 100, the secondary circuit of the instrument transformer 63c provided in the branch circuit 80 in the power generation device 60 is connected to the voltage measurement terminal 4B of the measurement system 1, and the measurement unit 4 of the measurement system 1 measures the voltage value of the current flowing in the branch circuit 80. As a result, the measurement unit 4 of the measurement system 1 in the power plant 100 measures the power received from the system G based on the current value of the current flowing in the bus electric circuit 70 and the voltage value of the current flowing in the branch electric circuit 80. The grid interconnection panel 20, load 40, power generation connection panel 50, power generation device 60, bus line 70, branch line 80, etc. that constitute such a power plant 100 will be described below.

[0042] <Grid connection panel 20> As shown in FIG. 3, the grid interconnection panel 20 is a panel that is connected to the grid G, and it can be said that there is only one of these in one power plant 100 described above, and the equipment that is connected to the grid G ​​is provided on the grid interconnection panel 20. The specific configuration of the devices provided on the grid interconnection panel 20 (strictly speaking, its panel housing 20′) is not particularly limited, but may include, for example, a combined voltage and current transformer (VCT) 21 for commerce, a disconnecting switch (also called a service breaker, which is different from the power generation connection disconnecting switch of the power generation connection panel 50, which will be described later) 22, a voltage transformer (VT, i.e., a high-voltage transformer) 23, a circuit breaker such as a vacuum circuit breaker (which can be called a system breaker or a high-voltage breaker, which is different from the power generation connection breaker (vacuum breaker) 51 of the power generation connection panel 50, which will be described later) 24, a current transformer (also called a high-voltage current transformer, which is different from the power generation connection current transformer of the power generation connection panel 50, which will be described later) 25, an overcurrent relay 26, a high-voltage AC load break switch (LBS, Load Breaker The power supply may include a power switch 27, a transformer (if it is a transformer for a general lighting load 41 described later, it can be said to be a lighting transformer, and if it is a transformer for a general power load 42 described later, it can be said to be a power transformer) 28, a molded case circuit breaker (MCCB) 29, a standby circuit breaker 30, etc. It can be said that the equipment provided in the grid interconnection panel 20 also includes the above-mentioned current sensor 2 of the measurement system 1 in the control panel 10 of the power generation device 60, which will be described later. 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, and the weight of the high voltage AC load switch 27 (or a general high voltage AC load switch) is also 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 on the system interconnection panel 20 may include a zero-phase voltage detector, a zero-phase current transformer, a load switch, an undervoltage relay, an overcurrent relay, a power supply circuit breaker, a voltmeter, an ammeter, a single-phase transformer, a single-phase transformer circuit breaker, a grounding resistor, a circuit protector, a voltage test terminal, a current test terminal, etc., and may also include a circuit for suppressing inrush current, a lightning arrester, an undervoltage relay, an overvoltage relay, an underfrequency relay (also called an under-frequency relay), an overfrequency relay, an electricity meter, etc.

[0043] <Grid interconnection panel 20 enclosure (grid interconnection panel enclosure) 20', etc.> 3, the panel housing 20' of the above-described grid interconnection panel 20 can also be referred to as the grid interconnection panel housing 20', and it can be said that at least some of the devices provided in the above-described grid interconnection panel 20 are built into this grid interconnection panel housing 20'. Of the devices provided in the grid interconnection panel 20, the transformer 28 does not have to be built into the grid interconnection panel housing 20', and the transformer 28 may be attached externally to the grid interconnection panel housing 20' or installed outside the grid interconnection panel housing 20'. Conversely, the transformer 28 may be built into the grid interconnection panel housing 20'. The specific configuration of the system interconnection panel casing 20' is not particularly limited, but may be formed, for example, in a substantially rectangular parallelepiped shape as a whole. When the entire system interconnection panel housing 20' is substantially rectangular, the system interconnection panel housing 20' may have openable and closable doors (front doors, etc.) on each of its side surfaces (front surface, rear surface, left surface, right surface, etc.). Furthermore, the system interconnection panel housing 20' may have a ceiling surface material, a bottom surface material, etc. in addition to the side surfaces. A lifting device that can be lifted by a crane or the like may be provided on the outer surface of the ceiling surface material of the system interconnection panel housing 20', and the entire system interconnection panel housing 20' lifted via this lifting device may be installed (mounted) on a foundation (base) that has been constructed in advance. The specific material of the foundation is not particularly limited, and may be made of, for example, concrete or steel (H-beam), and the specific configuration may be a mat foundation with a uniform thickness, a girder foundation with a recess or the like to form a space below the bottom material of the grid interconnection panel housing 20', or a foundation consisting of multiple pile members driven into the installation location. Note that if the foundation of the grid interconnection panel housing 20' is made of multiple pile members, the grid interconnection panel housing 20' will be installed on the upper end surfaces of the multiple pile members, which can also be said to reduce construction costs. The location (installation location) where these foundations or the grid interconnection panel housing 20' (grid interconnection panel 20) itself are installed is not particularly limited, and may be, for example, the outdoors of a building such as a store, or the indoors or outdoors of a factory, etc. The installation surface at this installation location may be approximately horizontal or inclined, and the surface of the installation surface may be approximately flat or may have irregularities.

[0044] <Load 40> 3, the load 40 is a load (load equipment) that consumes at least the power received from the grid G ​​(hereinafter also referred to as "received power"). In other words, the value of the power consumption (capacity) of the load 40 may be greater than the value of the received power received from the grid G ​​(only a part of the power consumption of the load 40 may be covered by the received power). The load 40 may be, for example, an automobile dealership or a gas station, a rental car store (rental car shop), a charger in a factory or workshop, or may include electrical equipment and facilities that use electricity such as electrical and electronic devices (general lighting loads 41 such as incandescent lamps, fluorescent lamps, and mercury lamps (lighting fixtures), and general power loads 42 such as air conditioners, motors, and pumps), or may even include the factory or workshop itself. Furthermore, the load 40 may include devices that use electricity, such as electrical and electronic equipment in offices of corporations and organizations such as companies, individuals, government offices and associations, homes, stores, warehouses, garages, parking lots, bicycle parking lots, school buildings, auditoriums, gymnasiums, research facilities, hospitals and clinics, inns and hotels, theaters, movie theaters, stadiums, baseball stadiums, etc., as well as the offices of companies and the like, or may include a combination of these.

[0045] <Power generation connection panel 50> FIG. 3 shows a power generation connection board 50 according to the present invention. The power generation connection board 50 is a board that connects the power generation device 60 (described later) to the grid interconnection board 20 and the load 40 described above. Inside the panel housing 50' of the power generation connection panel 50 are the branch electric circuits 80, which will be described later, and the vacuum circuit breaker 51, which will be described later. In addition, inside the panel housing 50' of the power generation connection panel 50 are the cable heads 52, which will be described later, and other devices such as disconnectors, current transformers, and overcurrent relays.

[0046] <Panel housing of power generation connection panel 50 (power generation connection panel housing) 50'> As shown in Figure 3, the panel housing 50' of the power generation connection panel 50, which can also be referred to as the power generation connection panel housing 50', is attached externally to the side of the panel housing (system interconnection panel housing) 20' of the above-mentioned grid interconnection panel 20, and the lower end of the power generation connection panel housing 50' is located at a higher position than the lower end of the grid interconnection panel housing 20'. In other words, the difference in height (difference in bottom end height) between the bottom end of the power generation connection panel housing 50' and the bottom end of the grid interconnection panel housing 20' is greater than 0 cm, and the specific value of this difference in bottom end height is not particularly limited, but may be, for example, 5 cm or more and 100 cm or less, preferably 10 cm or more and 70 cm or less, and more preferably 15 cm or more and 50 cm or less. When attaching the power generation connection panel housing 50' to the side of the grid interconnection panel housing 20', a foundation for the power generation connection panel housing 50' is not required, and the bottom surface material of the power generation connection panel housing 50' may be floating (separate) from the foundation or installation surface of the grid interconnection panel 20 (grid interconnection panel housing 20'). Furthermore, by attaching the panel housing 50' of the power generation connection panel 50, which incorporates the vacuum circuit breaker 51 provided on the branch circuit 80, from the outside to the side of the panel housing 20' of the grid interconnection panel 20 and making its lower end higher than the lower end of the panel housing 20' of the grid interconnection panel 20, even when adding a power generation device 60, there is no need 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 align the level of the created foundation with the existing foundation, thereby reducing expenses, the construction period for adding the power generation device 60, and the period during which electricity use by consumers is suspended. The specific configuration of the power generation connection panel casing 50' is not particularly limited, but may be formed, for example, in a substantially rectangular parallelepiped shape as a whole. The power generation connection panel housing 50' may include an upper panel housing 50A', which will be described later, and a lower panel housing 50B', which will be described later, and may further include other panel housings and boxes. The upper panel housing 50A' and the lower panel housing 50B' will be described below in order.

[0047] <Upper panel enclosure 50A'> As shown in FIG. 3, the upper panel housing 50A' is a panel housing that constitutes the upper side of the power generation connection panel housing 50' described above, and can be said to be a part of the power generation connection panel housing 50'. The upper panel housing 50A' is also attached externally to the side of the panel housing (system interconnection panel housing) 20' of the above-mentioned system interconnection panel 20, and naturally, the lower end of the upper panel housing 50A' is located higher than the lower end of the system interconnection panel housing 20'. The specific configuration of the upper panel housing 50A' is not particularly limited, and may be formed, for example, in a substantially rectangular parallelepiped shape as a whole. When the entire upper panel housing 50A' is substantially rectangular, the side members (front member, rear member, left member, right member, etc., particularly the front member) of the upper panel housing 50A' may be provided with an openable door (front door, etc.). The door may be fitted with a handle (lever handle, flush handle, etc.), and for example, the door may be locked or unlocked by moving a stopper (rod-shaped (bar-shaped) made of stainless steel (SUS), etc.) fixed at three points by this handle. The upper panel housing 50A' may have a ceiling surface material (top surface material), a bottom surface material (lower surface material), and the like in addition to the side surface material. The specific configuration of the means for attaching the upper panel housing 50A' to the grid interconnection panel housing 20' is not particularly limited, but for example, the power generation connection panel housing 50' may be attached to the grid interconnection panel housing 20' by means of fasteners (bolts, nuts, etc.), welding (such as welding mounting brackets all around), adhesive, fitting, etc.

[0048] <Lower panel chassis 50B'> As shown in FIG. 3, the lower panel casing 50B' is a panel casing that constitutes the lower side of the power generation connection panel casing 50' described above, and can be said to be a part of the power generation connection panel casing 50'. The lower panel housing 50B' is also attached from the outside to the side surface of the panel housing (grid interconnection panel housing) 20' of the above-mentioned grid interconnection panel 20, and the lower end of the lower panel housing 50B' is naturally located higher than the lower end of the grid interconnection panel housing 20'. Note that the difference in height between the lower end of the lower panel housing 50B' and the lower end of the grid interconnection panel housing 20' can also be said to be the difference in bottom height, which is the difference in height between the lower end of the above-mentioned power generation connection panel housing 50' and the lower end of the grid interconnection panel housing 20'. The specific configuration of the lower panel housing 50B' is not particularly limited, and may be formed, for example, in a substantially rectangular parallelepiped shape as a whole. When the entire lower panel housing 50B' is approximately rectangular, the lower panel housing 50B' may have one of its side members (front member, rear member, left member, right member, etc., particularly the front member) removable, and may also be provided with an openable / closable door (front door, etc.), or conversely, may not be provided with an openable / closable door. The lower panel housing 50B' may have a ceiling surface material (upper surface material), a bottom surface material (lower surface material), and the like in addition to the side surface material. The specific configuration of the means for attaching the lower panel housing 50B' to the grid interconnection panel housing 20' is not particularly limited, but for example, the power generation connection panel housing 50' may be attached to the grid interconnection panel housing 20' by means of fasteners (bolts, nuts, etc.), welding (such as welding mounting brackets all around), adhesive, fitting, etc.

[0049] Furthermore, in the upper panel casing 50A' and the lower panel casing 50B', the branch electric circuit 80, which will be described later, can be said to be arranged (provided) inside the upper panel casing 50A' and the lower panel casing 50B'. A vacuum circuit breaker 51 or a circuit breaker, described below, may be placed inside one of the upper panel housing 50A' and the lower panel housing 50B'.In this case, if the vacuum circuit breaker 51 has a built-in current transformer or overcurrent relay, the current transformer or overcurrent relay will also be placed inside one of the upper panel housing 50A' and the lower panel housing 50B' (for example, the upper panel housing 50A'). By arranging the branch circuit 80 inside the upper panel housing 50A' and the lower panel housing 50B' and arranging the vacuum circuit breaker 51 inside the upper panel housing 50A' or the lower panel housing 50B', even though the weight of the vacuum circuit breaker 51 tends to be heavy due to its high upper capacity limit, if one of the upper panel housing 50A' and the lower panel housing 50B' that has the vacuum circuit breaker 51 built in is transported and installed separately from the other panel housing, the workload and work time can be reduced, resulting in a reduction in expenses, construction period, and power outage period. Alternatively, the cable head 52, which will be described later, may be disposed inside the other of the upper and lower panel housings 50A' and 50B'.

[0050] <Generation Connection Circuit Breaker (Vacuum Circuit Breaker) 51> 3, the power generation connection circuit breaker 51 is a vacuum circuit breaker (VCB), which is provided in a branch electric circuit 80 (described later) and is a device that opens and closes the branch electric circuit 80 (three-phase three-wire collectively) when high voltage AC current is flowing, and extinguishes the arc within the vacuum valve. Note that this vacuum circuit breaker 51 is separate from the system circuit breaker 24 provided in the system interconnection panel 20 described above. The vacuum circuit breaker 51 may include a current transformer and an overcurrent relay. The vacuum circuit breaker 51 may also be of an electric spring operation (capacitor trip) type. The rated capacity of the vacuum circuit breaker 51 is not particularly limited, but may be, for example, 2000 kVA or more and 100,000 kVA or less, preferably 2500 kVA or more and 50,000 kVA or less, and more preferably 3000 kVA or more and 10,000 kVA or less (such as 4,320 kVA). The weight of the vacuum circuit breaker 51 is not particularly limited, but may be, for example, 15 kg to 1000 kg, preferably 20 kg to 500 kg, and more preferably 25 kg to 100 kg (eg, 32 kg).

[0051] <Cable head 52, other equipment> As shown in Figure 3, the cable head 52 is provided on a branch electric circuit 80 described later, and is a part that has been subjected to terminal processing to connect the branch electric circuit 80 to high-voltage equipment such as the vacuum circuit breaker 51 and disconnector (power generation connection disconnector) described above. The specific configuration of the cable head 52 is not particularly limited, but for example, the coating of the ends of the cables or wires that make up the branch electric circuit 80 is stripped off, wrapped with insulating tape or semi-conductive tape, and a branch pipe is used to branch the branch electric circuit 80 into three branches if it is a three-phase, three-wire circuit, or if it is a single-phase, two-wire circuit, it is branched into two branches. The cable head 52 may be grounded, and the type of grounding is not particularly limited, but may be, for example, a type A grounding. Other devices built into the panel housing 50' of the power generation connection panel 50 may include, for example, a disconnecting switch (DS), an ammeter, insulators, a reverse power relay (RPR), and a power meter (such as a generating power meter or a receiving power meter).

[0052] <Generator 60> As shown in Figure 3, the power generation device 60 is a device connected to the above-mentioned grid interconnection board 20 and the above-mentioned load 40 via the above-mentioned power generation connection board 50, and has a power generation unit 61 and a conversion unit 62 described below. Additionally, the power generating device 60 may include a switchboard 63 .

[0053] As shown in Figure 3, the power generation unit 61 is the part that generates electricity and may have any configuration, such as solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, solar thermal power generation, power generation using heat in 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). Alternatively, the power generating unit 61 may generate power using ocean temperature difference, wave power, tidal currents (ocean currents), or tides. The number of power generation units 61 in one power generation device 60 is not particularly limited, but may be, for example, one or more, and the power generation power (capacity) of the power generation unit 61 is also not particularly limited, but may be, for example, 100 kW or more and 30,000 kW or less, preferably 300 kW or more and 20,000 kW or less, and more preferably 500 kW or more and 10,000 kW or less. The following will particularly describe the solar power generation unit 61 that generates solar power. The solar power generation unit 61 includes a solar cell 61a in the form of a panel or the like. In addition, the solar power generation unit 61 may include a pyranometer that measures solar radiation intensity, a current collector that collects DC current from the solar cells 61a, a junction box, etc., and sends it to the conversion unit 62 described below, etc. The solar power generation unit 61 may include a plurality of solar cells 61a, and these plurality of solar cells 61a may be connected in series to form a solar cell string. The solar power generation unit 61 may include a junction box to which a plurality of solar cell strings are connected in parallel, and there may be a plurality of such junction boxes.

[0054] As shown in FIG. 3, the conversion unit 62 is a 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 that converts 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 converted by the inverter, an air circuit breaker, etc. The conversion unit 62 is also called a power conditioner (PACON). The number of conversion units 62 in one power generation device 60 is not particularly limited, and may be, for example, multiple (for example, four or five) or just one. The conversion power (capacity) that can be converted by the conversion unit 62 is also not particularly limited, and may be, for example, 30 kW to 10,000 kW, preferably 50 kW to 5,000 kW, and more preferably 100 kW to 2,000 kW (250 kW, 500 kW, etc.). The conversion power of the conversion unit 62 may be smaller than the power generation power of the solar power generation unit 61 described above (in other words, the power generation capacity may be greater than the conversion power). In this case, it can be said that the solar cell 61a is overloaded with respect to the conversion unit 62. Additionally, the conversion unit 62 may have an undervoltage relay, an overvoltage relay, an underfrequency relay, an overfrequency relay, or a passive or active islanding protection device.

[0055] As shown in Figure 3, the distribution board 63 is a board that distributes the electricity generated from the power generation unit 61 via the conversion unit 62 to the grid interconnection board 20, and it can be said that one or more distribution boards exist in one power plant 100, and the distribution board 63 has components that distribute electricity to the grid interconnection board 20. The specific configuration of the components of the distribution board 63 is not particularly limited, but may include, for example, a board housing 63a that incorporates equipment that distributes power to the system interconnection board 20, a transformer 63b, etc., and the above-mentioned control board 10 may be attached to the board housing (in other words, the distribution board housing) 63a of the distribution board 63. The specific configuration of the devices housed in the panel housing 63a of the distribution panel 63 is not particularly limited, but may include, for example, a voltage transformer (VT; in other words, a distribution transformer, different from the high-voltage transformer 23 of the grid interconnection panel 20) 63c and a zero-phase voltage detector (ZPD) 63d, as well as a voltmeter, a low-voltage circuit breaker, a circuit protector, and (a part of) a branch electric circuit 80 described below. Note that the output from the distribution transformer 63c may be output to the measurement system 1 housed in the control panel 10, and the output from the zero-phase voltage detector 63d may be output to the earth fault overvoltage relay 13 housed in the control panel 10. The transformer (i.e., distribution transformer) 63b of the switchboard 63 is a device that transforms (steps up) low-voltage AC current from outside the switchboard housing 63a (from the power generation unit 61 through the conversion unit 62) into higher-voltage AC current, and is a so-called transformer (TR). The word "transformer" is an abbreviation for "transformer." The switchboard housing 63a may be attached to the distribution transformer 63b from above. In other words, the distribution transformer 63b is installed outside the switchboard housing 63a, eliminating the need for a ventilation fan or auxiliary power supply for the ventilation fan inside the switchboard housing 63a. This allows for easy repair and painting of the distribution transformer 63b (main body), allows for long-term maintenance (e.g., 20 years or more), and eliminates the need for assembly work at the installation site by shipping the unit as a whole.

[0056] <Bus line 70> As shown in FIG. 3 , the bus electric circuit 70 is an electric circuit (such as a three-phase three-wire (3φ3W)) between the system G and the above-mentioned load 40. Here, the "bus electric circuit 70 between the system G and the load 40" in the present invention includes not only the case where the entire electric circuit between the system G and the load 40 is the bus electric circuit 70, but also the case where at least a part of the electric circuit between the system G and the load 40 (for example, the electric circuit from the system G to the transformer 28 of the system interconnection panel 20) is the bus electric circuit 70, and it can be said that the electric circuit that exists (is present) between the system G and the load 40 is the bus electric circuit 70. Note that, among the electric circuits between the system G and the load 40, if the electric circuit from the system G to the transformer 28 of the system interconnection panel 20 is the bus electric circuit 70, the remaining electric circuit from the transformer 28 to the load 40 can also be said to be a system low-voltage circuit. Furthermore, the entire electrical circuit between system G and load 40 is a bus electrical circuit 70 when, for example, the load 40, which has (built-in) a transformer (step-down transformer), is directly connected to system G by a bus electrical circuit 70. The potential in this busbar circuit 70 may be the same as the potential in system G (6600V, 22000V, etc.), and if a transformer 28 (which can also be called a step-down transformer, specifically the lighting transformer or power transformer mentioned above) of the system interconnection panel 20 is provided between each load 40 and the busbar circuit 70, the circuit connecting this transformer 28 (its high voltage side) and system G can be said to be the busbar circuit 70. The busbar circuit 70 is provided with the equipment of the system interconnection panel 20 described above, and to explain each piece of equipment in detail, the busbar circuit 70 may be provided with, in order from system G to load 40, a supply transformer current transformer 21, an incoming switchgear 22, a high-voltage transformer 23 (strictly speaking, provided in a circuit branching from the busbar circuit 70), a system circuit breaker 24, a high-voltage current transformer 25, an overcurrent relay 26 (strictly speaking, provided in the output circuit of the high-voltage current transformer 25), a high-voltage AC load switchgear 27, a transformer 28, etc. The bus electric circuit 70 described above may be connected to the devices (particularly the branch electric circuit 80) housed in the above-mentioned power generation connection board 50.

[0057] <Branch Circuit 80> As shown in Figure 3, the branch electric circuit 80 is an electric circuit (such as a three-phase three-wire (3φ3W)) branching off from the bus electric circuit 70 described above, and is an electric circuit that connects the power generation device 60 described above to the grid interconnection panel 20 and the load 40 described above. The branch electric circuit 80 may be connectable to the bus electric circuit 70. In this case, the potential of the branch electric circuit 80 is the same high voltage as the bus electric circuit 70 and the potential of the system G (that is, the branch electric circuit 80 is at approximately the same potential as the bus electric circuit 70, such as 6600V or 22000V). Therefore, even if the distance between the system interconnection panel 20 or the load 40 and the power generation device 60 becomes long (even if the distance becomes long), the branch electric circuit 80 is at a high voltage, which reduces cable loss and allows the power generation device 60 to be installed anywhere (increasing the number of installation location options). One end of the branch electric circuit 80 is connected to the bus electric circuit 70 (an electric circuit at any point between the equipment provided on the system 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 electric 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 electric circuit from the input side of the power generation device 60 (the input side (low-voltage side) of the distribution transformer 63b) to the conversion unit 62 and the power generation unit 61 can also be said to be a distribution low-voltage circuit). Therefore, the branch circuit 80 may have not only a portion provided inside the above-mentioned panel housing (power generation connection panel housing) 50' of the power generation connection panel 50, but also a portion protruding from the power generation connection panel housing 50', and this protruding portion may be the portion between the power generation connection panel 50 (power generation connection panel housing 50') and the distribution panel 63 in the above-mentioned power generation device 60, or a portion provided inside the distribution panel 63. As described above, the branch circuit 80 is provided with the above-mentioned equipment built into the power generation connection panel 50 and the above-mentioned equipment of the power generation device 60. To explain each piece of equipment in detail, the branch circuit 80 may be provided, in order from the bus bar circuit 70 to the distribution panel 63 of the power generation device 60, with the above-mentioned disconnecting switch, the above-mentioned vacuum circuit breaker 51 (which may include the above-mentioned current transformer and overcurrent relay), the above-mentioned cable head 52, and equipment built into the distribution panel housing 63a of the above-mentioned distribution panel 63 (such as the distribution transformer 63c and zero-phase voltage detector 63d).

[0058] <Tests 1-3> In tests 1 to 3 of the present invention, test configurations 1 to 3 and a comparative configuration were created for the measurement system 1 described above, and test configuration 1 and the comparative example were used in test 1, test configuration 2 was used in test 2, and test configuration 3 was used in test 3. First, we will provide a detailed explanation of test configurations 1 to 3 and the comparison configuration.

[0059] <Test Configuration 1> As shown in FIG. 5(a), in test configuration 1, one measurement system 1 includes 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 covering the two sensor cables 3. The measurement unit 4 includes two pairs of high-potential side current measurement terminals 4Aa and low-potential side current measurement terminals 4Ab (corresponding to R phase and T phase), and one three-phase three-wire voltage measurement terminal 4B. The shield wires 5b of the shield 5 are connected to the low-potential side 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 100 m (the apparent length is approximately half that, or 50 m), and one wire of the three-phase three-wire voltage measurement terminals 4B of the measurement unit 4 is grounded. For such a measurement system 1, the test equipment used in test configuration 1 was a control power supply X1 that supplies power (DC 24V) to the measurement system 1, a three-phase generator (three-phase three-wire (3φ3W), 110V constant, 50 / 60Hz switchable, "RX4763" manufactured by NF Corporation) X2, a digital power meter ("2533" manufactured by Yokogawa Measurement Corporation) X3, an RS-232C / RS-485 converter X4, and a personal computer X5.

[0060] <Test Configuration 2> As shown in Figure 5(b), test configuration 2 was created by placing an iron plate X6 under the system housing 7 of the measurement system 1 in test configuration 1 and connecting the wire from the iron plate X6 to the ground wire from the measurement unit 4. The three-phase generator X2 was replaced with another three-phase generator (three-phase, three-wire (3φ3W), 110V, 4A constant, 50 / 60Hz switchable, "VBU-100" manufactured by Keihin Densokuki Co., Ltd. (now Densoku Techno Co., Ltd.)) X2', and the digital power meter X3 was replaced with a noise simulator ("INS-4020" manufactured by Noise Laboratory Co., Ltd.) X3'. The noise output circuit 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. The input from this three-phase generator X2' has an input fluctuation of ±1%.

[0061] <Test Configuration 3> As shown in Figure 5(c), test configuration 3 was created by connecting the circuit that outputs noise from the noise simulator X3' in test configuration 2 to a coupling adapter ("CA-805B" manufactured by Noise Laboratory Co., Ltd.) X3'', and covering part of the shield 5 of the measurement system 1 with this coupling adapter X3''.

[0062] <Comparative configuration> A comparative configuration was prepared in which the shield wire 5b of the shield 5 of the measurement system 1 in the test configuration 1 was not connected to the current measurement terminal 4Ab on the low potential side of each pair but was directly grounded.

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

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] <Evaluation of Test 1> First, from Tables 1 and 2, when the three-phase, three-wire currents of each reference measurement value were input into measurement system 1 of test configuration 1, the error in the measurement value for both the R-phase and T-phase current values ​​was at least 0.00% and at most 0.08%, which was significantly below the allowable error of ±0.5%.By connecting shield wire 5b of shield 5 of sensor cable 3 to current measurement terminal 4A of measurement unit 4 and grounding measurement unit 4, the length of sensor cable 3 was extended to 100m, which is 10 times the approximately 10m at which accuracy was previously ensured, and extremely accurate values ​​could be measured, ensuring accuracy ("Extending the cable and ensuring accuracy"). However, when three-phase, three-wire currents with measurement reference values ​​of 8000 A (100.0%) and 0 A (0.0%) are input into a measurement system with a comparative configuration in which the shielded wire is directly grounded, the measurement value (and therefore the error) fluctuates within a specified range. Therefore, even though the input reference current value is constant, the measurement value obtained by measuring it is not stable, and it can be said that accuracy is far from being ensured. Furthermore, in a measurement system with a comparative configuration in which the shielded wire is directly grounded, even when a three-phase, three-wire current with a measurement reference value of 0A (0.0%) was input, the error was 2.00%, four times the allowable error. Furthermore, when a three-phase, three-wire current with a measurement reference value of 0A (0.0%) was input, the error was a maximum of 6.3%, more than 10 times the allowable error, meaning that accuracy was not ensured at all. Furthermore, Table 3 shows that in a measurement system 1 in which shielded wire 5b is connected to current measurement terminal 4A of measurement unit 4 and measurement unit 4 is grounded, not only the current values ​​shown in Tables 1 and 2 but also the power values ​​multiplied by the measured voltage values ​​are within the allowable error range when the three-phase, three-wire currents of the reference values ​​for all measurements are input, ensuring accuracy in the power values ​​as well. Furthermore, Table 3 lists the error as -37.50% when a three-phase, three-wire current is input with a measurement reference value of 0.192 MV (0.2%). However, as mentioned above, the allowable error in the power value depends on the operating value of the reverse power, and the allowable error when the reference value is 0.192 MV (0.2%) is when the operating value is < 1% (operating value less than 1%). Therefore, it is sufficient that the measured value is within the range of the actual power value equivalent to ±5 mA, rather than being a percentage. The measured value when the reference value is 0.192 MV (0.2%) is 0.12 MV for both 50 Hz and 60 Hz, which is within the allowable error range of 0.10 to 0.28 MV, and it can be said that sufficient accuracy has been ensured.

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

[0069] [Table 4]

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

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

[0072] [Table 5]

[0073] <Evaluation of Test 3> Table 5 shows that for measurement system 1 in test configuration 3, just as in test 2, even if the noise pulse width was 1 μS or 100 nS, or the square-wave impulse noise was positive or negative, the errors in the measurement values ​​displayed on display 8 of measurement system 1 and the measurement values ​​output and communicated from measurement system 1 to personal computer X5 were less than ±1%, well below the allowable error of less than ±10%.By connecting shield wire 5b of shield 5 of sensor cable 3 to current measurement terminal 4A of measurement unit 4 and grounding measurement unit 4, extremely accurate values ​​could be measured and accuracy was ensured, even if square-wave impulse noise was input to or generated from sensor cable 3, which was extended to 100 m, which is 10 times the approximately 10 m at which accuracy was previously ensured ("Cable extension and ensuring accuracy").

[0074] Furthermore, in the above-mentioned tests 2 and 3, the errors were checked not only for the measurement values ​​displayed on the display unit 8 of the measurement system 1, but also for the measurement values ​​communicated and output from the measurement system 1 to the personal computer X5 via the RS-232C / RS-485 converter X4 (which is essentially a communication cable) and displayed on the personal computer X5. Therefore, it can be said that once a measurement value is accurately measured by the measurement system 1, it can be confirmed with very small errors on a terminal such as a remote computer via a communication cable, the Internet, a telephone line, etc.

[0075] <Other> The present invention is not limited to the above-described embodiment. The individual components or the overall structure, shape, dimensions, etc. of the measurement system 1, the control panel 10, the 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 include the relay unit 6 or the display unit 8. The current sensor 2 does not have to be of the open / close type. The measurement unit 4 does not necessarily have to include the voltage measurement terminal 4B. The control panel 10 does not necessarily have to have the control device 12 inside its panel housing 10'. The panel housing 50' of the power generation connection panel 50 may not include an upper panel housing 50A' and a lower panel housing 50B', or any other panel housings or boxes; in this case, the power generation connection panel 50 can be said to be composed of a single panel housing 50'. The panel housing 50' of the power generation connection panel 50 does not necessarily have to include at least one of the disconnector, the cable head 52, the current transformer, and the overcurrent relay. The openable doors of the power generation connection panel 50 (such as the upper panel housing 50A' and the lower panel housing 50B') may be provided with door stoppers (made of stainless steel, for example), and the openable doors of the power generation connection panel 50 and the detachable front members may be provided with gaskets at their opening portions. The vacuum circuit breaker 51 and the disconnecting switch may be grounded, and the type of grounding is not particularly limited, but may be, for example, a type A grounding. In addition, the power plant 100 may have the branch circuit 80 and the vacuum circuit breaker 51 inside the panel housing 20' of the grid interconnection panel 20 (i.e., they do not have to be inside the panel housing 50' of the power generation connection panel 50 which is separate from the panel housing 20' of the grid interconnection panel 20). Furthermore, the power plant 100 may have a pole-mounted air switch 100a (described later) between the system interconnection panel housing 20' and the system G in the busbar circuit 70, and may also have a commercial transformer, a power purchase energy meter, a power sale energy meter, and a protective relay device. The power plant 100 may also include a power storage device (not shown), which will be described below.

[0076] <Electricity storage device> The storage device is a device that stores electricity (received power) from the system G and electricity (generated power) from the above-mentioned power generation device 60, and may be provided outside the panel housing of the above-mentioned system interconnection panel 20, power generation connection panel 50, distribution panel 63 of the power generation device 60, etc. The power storage device may be, for example, a storage battery such as a lead storage battery, a lithium ion storage battery, a nickel-metal hydride storage battery, or a nickel-cadmium storage battery; it may store hydrogen generated by electrolysis of water using the power generated by the power generation device 60, and extract electricity when needed using a fuel cell or the like; it may also be a device that stores electricity as kinetic energy using a flywheel or the like, stores electricity as potential energy using pumped water, or stores electricity directly as electrical energy using a capacitor or the like. Such a power storage device may be connected to the bus line 70, and the stored power from this power storage device will be consumed by the load 40 described above. Furthermore, since the storage of electricity in the storage device and the discharge of electricity from the storage device are performed using direct current, a conversion unit may be connected between the storage device and the bus bar circuit 70 to convert alternating current into direct current or to convert direct current from the storage device into alternating current to be supplied to the bus bar circuit 70. The system G relating to the measurement system 1, control panel 10, and power distribution plant 100 described above will be explained in detail below.

[0077] <System G> As shown in Fig. 3, system G transmits (receives) electricity to a power generation connection panel 50 and a power plant 100, and refers to the entire system through which electric power companies and the like supply electricity to consumers, and can also be called a power system. Specifically, system G includes facilities such as substations, transmission lines, and distribution lines, and may also include power plants. System G may also include the above-mentioned pole air switches (PAS) 100a, as well as a commerce transformer, a power purchase watt-hour meter, a power sale watt-hour meter, and protective relay devices. The power handled by such a system G may be either AC or DC, but the following description will be given assuming that it is AC. In System G, most of the electricity transmitted is AC, so it is transmitted using three-phase, three-wire (3φ3W) transmission lines. In order to reduce transmission losses during this process, the main long-distance transmission sections transmit electricity at as high a voltage as possible (for example, 6600V or 22000V). The electricity transmitted by system G is transformed (stepped down) in several stages near the point of consumption, and after the pole-mounted transformer, it is distributed via single-phase two-wire (1φ2W) or similar. System G may be a system such as a power company system (commercial power system), a system independently owned by an organization such as a company or a local government, or a system within a plant (independent power system). [Industrial Applicability]

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

[0079] 1. Measurement system 2 Current Sensors 3 Sensor Cable 3a Outgoing sensor cable 3b Return sensor cable 4. Measurement section 4A Current measurement terminal of the measurement section 4Aa Current measurement terminal on the high potential side of the measurement section 4Ab Current measurement terminal on the low potential side of the measurement section 4B Voltage measurement terminal of the measurement section 5 Shield 5a Shielding conductive shield layer 5 Shielded wire 6 Relay section 10 Control Panel 10' control panel enclosure 11 Power storage unit 20 Grid connection panel 25 Current transformer for instrument on grid interconnection panel 40 Load 60 Power Generation Equipment 63c Instrument transformers for generating sets 70 Busbar electrical circuit 80 Branch Electrical Circuit 100 Power Plants D Sensor Current G system

Claims

1. A measurement system that measures at least a current value of a current flowing through a predetermined electrical path, The measurement system includes a current sensor (2) attached to the electric circuit and outputting a sensor current (D) having a current value corresponding to the current value of the current flowing through the electric 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 electric circuit based on the sensor current (D) input via the sensor cable (3), The measurement unit (4) includes a current measurement terminal (4A) to which the sensor cable (3) is connected, The sensor cable (3) is fitted with a shield (5), The shield (5) includes a conductive shield layer (5a) that covers the sensor cable (3) and a shield wire (5b) that is electrically connected to the conductive shield layer (5a); The shielded wire (5b) is connected to a current measurement terminal (4A) of the measurement unit (4), The measurement system is characterized in that the measurement unit (4) is grounded.

2. 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 allows a current to flow from the measurement unit (4) to the current sensor (2) and a return sensor cable (3b) that allows a current to flow from the current sensor (2) to the measurement unit (4), At least the outgoing sensor cable (3a) and the return sensor cable (3b) are covered with one of the conductive shield layers (5a), The outgoing sensor cable (3a) is connected to the high-potential side current measurement terminal (4Aa), and the returning sensor cable (3b) is connected to the low-potential side 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, 2. The measurement system according to claim 1, wherein the measurement unit (4) is grounded from a terminal having substantially the same potential as the low-potential side current measurement terminal (4Ab).

3. 3. The measurement system according to claim 1, wherein the length of the sensor cable is between 20 m and 2000 m.

4. A control panel having the measurement system (1) according to claim 1 or 2 inside a panel housing (10'), The control panel also has a power storage unit (11) inside the panel housing (10') 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 operation on electrical and electronic equipment outside the panel housing (10') in accordance with the measurement value measured by the measurement unit (4) based on at least the sensor current (D).

5. A power plant comprising a measurement system (1) according to claim 1 or 2, The power plant also includes a grid interconnection panel (20) connected to a grid (G), a load (40) connected to the grid interconnection panel (20), a power generation device (60) connected to the grid interconnection panel (20) and the load (40), a bus line (70) between the grid (G) and the load (40), and a branch line (80) branching from the bus line (70) and connected to the power generation device (60), The current sensor (2) is attached to a secondary circuit of an instrument current transformer (25) provided in a bus 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 in the bus circuit (70), The measurement unit (4) of the measurement system (1) includes a voltage measurement terminal (4B) to which a predetermined electric circuit is connected, and measures a voltage value of a current flowing through the electric circuit based on a current input from the electric circuit to the voltage measurement terminal (4B); a secondary electric circuit of an instrument transformer (63c) provided in a branch electric circuit (80) of the power generation device (60) is connected to the voltage measurement terminal (4B), whereby the measurement unit (4) of the measurement system (1) measures a voltage value of a current flowing in the branch electric circuit (80); The power plant is characterized in that the measurement unit (4) of the measurement system (1) measures the power received from the system (G) based on the current value of the current flowing in the bus electric circuit (70) and the voltage value of the current flowing in the branch electric circuit (80).

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