JP2015025795A - Insulation inspection method, and insulation inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation inspection device which enables searching of insulation defective point in a solar light power generation unit.SOLUTION: A CPU 101 detects a first current when a first voltage is supplied to a solar light power generation unit 50 from a high voltage generating circuit 140 and a second current when a second voltage is supplied, by using an input/output circuit 160, to acquire as a digital current value. The CPU 101 derives a change gradient of a difference current value between the first current and the second current relative to a difference voltage value between the first voltage and the second voltage, and based on the change gradient, derives a virtual voltage value when a current value of the first current or second current comes to be a zero value from a significant value. By comparing the virtual voltage value with an inter-terminal voltage value of the solar light power generation unit 50, a point of insulation failure is determined.

Description

  The present invention relates to a method and an apparatus for performing an insulation test of a DC power generation unit formed by connecting a plurality of power generation bodies such as a solar power generation unit.

  Recent photovoltaic power generation units are capable of outputting large power of several thousand watts at several hundred volts. Therefore, from the viewpoint of preventing an electric leakage accident, the photovoltaic power generation unit needs to measure the insulation resistance value as appropriate even after installation and periodically inspect whether or not insulation failure has occurred. For measuring the value of insulation resistance, an insulation resistance meter generally called “Megger” is used.

  However, since the photovoltaic power generation unit is insulated from the ground after installation, it is charged including the electric circuit. That is, an electric charge accumulates in the solar cell module or the solar cell constituting the solar power generation unit. The electric charge is not necessarily balanced with respect to the positive electrode terminal and the negative electrode terminal of the photovoltaic power generation unit, and the amount of electric charge stored varies depending on the weather. Therefore, when the insulation test is performed outdoors, there is a problem that a large error occurs in the measurement result of the insulation resistance value during the daytime when sunlight is irradiated.

As a prior art for solving this problem, there is a method and apparatus for measuring insulation resistance of a solar cell module disclosed in Patent Document 1. In this measuring method, a ground wire is connected to the solar cell module via a resistor, the accumulated electric charge is discharged via the ground wire, and the insulation resistance is measured after the discharge is completed.
However, even if the accumulated charge is discharged, when the insulation test is performed during the day, the solar cell module continues to generate power, so that it is difficult to measure a correct insulation resistance value. In order to solve the problem of power generation during measurement of insulation resistance, the solar power generation unit may be covered with a light shielding cloth or the like during the daytime, or the measurement operation may be performed at night. However, when the photovoltaic power generation unit is installed outdoors at a high place, it is very dangerous to perform measurement work at night when it is covered with a light-shielding cloth or the like and the visibility is not sufficient.

The insulation resistance measuring device disclosed in Patent Document 2 is designed to allow the insulation resistance value to be safely inspected at an arbitrary time point in order to eliminate the above danger. That is, in the insulation resistance measuring device disclosed in Patent Document 1, a current (first current value) that flows in a state in which an inspection voltage is applied between the positive electrode terminal of the photovoltaic power generation unit and the ground portion, and application of the inspection voltage And a current (second current value) flowing in a state where the current is stopped. And the insulation resistance value between a positive electrode terminal and a grounding part is calculated based on the electric current (3rd electric current value) which is the difference of both electric current values, and the voltage value of the applied test voltage.
This eliminates the need to cover the solar power generation unit with a light shielding cloth and eliminates the need to carry out measurement work at night by avoiding the irradiation of sunlight. It can be measured.

  Patent Document 2 also discloses a first current value obtained by linearly approximating each current value flowing between the positive electrode terminal and the ground portion in a state in which the changed test voltage is applied while changing the voltage value of the test voltage. Is also described.

JP 2012-146931 A JP 2011-122793 A

The solar power generation unit is normally an ungrounded electric circuit. Therefore, even if insulation failure occurs in the middle of the electric circuit, for example, on the negative electrode terminal side and the insulation resistance value becomes smaller than the standard limit, no direct current (leakage current) flows through the photovoltaic power generation unit. That is, malfunctions such as devices and circuits connected to the photovoltaic power generation unit, such as relays, do not occur only when insulation failure occurs.
On the other hand, in order to measure the insulation resistance of the photovoltaic power generation unit, when the positive terminal of the insulation resistance meter is connected to the positive terminal of the photovoltaic power generation unit and the negative terminal is connected to the grounded part, the current that did not flow before connection is insulated. It begins to flow through the resistance meter. Depending on the magnitude of this current, burnout of the device and malfunction of the circuit may occur. In order to prevent this, the insulation resistance meter must include a large-capacity resistor between the grounding portion and the ground. However, if it does so, the mass of a meter main body must be large and it must be expensive, and the problem of affecting workability | operativity will arise.

The insulation resistance measuring device disclosed in Patent Document 2 measures an insulation resistance value while a photovoltaic power generation unit is generating power. That is, by connecting the insulation resistance measuring device in a state where the application of the inspection voltage is stopped, a direct current (second current) having a magnitude caused by the generated voltage is generated between the output terminal of the photovoltaic power generation unit and the grounding portion. Value) flows (paragraph 0031 of Patent Document 2). For this reason, this insulation resistance measuring device must be equipped with a large-capacity resistor in consideration of the value of the generated voltage and the current value at the time of insulation failure. There is.
In addition, the insulation resistance measuring device disclosed in Patent Document 2 has a problem that it cannot be used in the weather or nighttime when the photovoltaic power generation unit does not generate power.

  In the insulation resistance measuring device disclosed in Patent Document 2, it is said that the insulation resistance value can be obtained by calculation. If an insulation failure has occurred, it is possible to determine where the insulation resistance value has occurred. Cannot explore. This also applies to the measurement apparatus disclosed in Patent Document 1.

The present invention solves the above-mentioned problem, suppresses the leakage current that flows when measuring the insulation resistance of a DC power generation unit, thereby reducing the influence on the power generation equipment side and reducing the size of the instrument body. An object is to enable weight reduction.
Another object of the present invention is to provide an insulation inspection technique that enables searching for a location of insulation failure in a DC power generation unit.

  The insulation inspection method of the present invention is a method executed by a device capable of measuring voltage and current in a DC power generation unit to which a plurality of power generation bodies are connected, and a pair of output terminals of the DC power generation unit The test voltage for reducing the amplitude of the voltage appearing at the terminal is supplied to the electric circuit between any one of the terminals and the grounding part at a predetermined time interval twice or more, and thereby the electric circuit Detecting a difference current value representing a difference between currents flowing in the circuit, and deriving an insulation resistance value of the electric circuit based on the current difference value and a difference voltage value representing a difference between the changed inspection voltages. Is the method.

  The insulation inspection apparatus according to the present invention is configured such that the amplitude of the voltage appearing on the terminal is in an electric circuit between any one of the pair of output terminals of the DC power generation unit to which the plurality of power generation bodies are connected and the ground part. Represents a difference between a voltage supply means for supplying a test voltage having a value for reducing the test voltage at a predetermined time interval at two or more times with a different value, and a current flowing through the electric circuit when the value of the supplied test voltage changes. Current detection means for detecting a difference current value; and insulation resistance value deriving means for deriving an insulation resistance value of the electric circuit based on the current difference value and a difference voltage value representing a difference between the changed inspection voltages. Device.

In the insulation inspection method and the insulation inspection device of the present invention, the DC power generation unit is supplied with at least twice the inspection voltage having a value that reduces (cancels) the amplitude of the voltage appearing at one of the output terminals. The insulation resistance value is derived from the difference between the currents that change due to. Therefore, the leakage current that flows in the DC power generation unit in comparison with the inspection method including the case where the inspection voltage is not supplied during the insulation inspection (for example, when the inspection voltage is zero as in the invention disclosed in Patent Document 2). Therefore, troubles caused by leakage current are prevented. In addition, since the current flowing through the instrument body is reduced, it is not necessary to provide a large-capacity resistor in the instrument body, and the instrument body can be reduced in size and weight.
In addition, since the inspection voltage is supplied to the DC power generation unit at least twice and the difference between the currents flowing at that time is detected, the insulation inspection can be performed even in the weather and nighttime when the generated voltage is not sufficient.
Moreover, in the structure provided with the search means, the relative position of the insulation failure location can be specified by comparing the virtual voltage value and the voltage value between the terminals of the DC power generation unit. Can be explored.

The external view of the insulation test | inspection apparatus by this embodiment. The block diagram of an electronic circuit part. The block diagram of the photovoltaic power generation unit used as an example of a direct-current power generation unit. Explanatory drawing which shows the connection condition of the insulation test | inspection apparatus to a photovoltaic power generation unit. Explanatory drawing which shows the substantial connection state of a photovoltaic power generation unit and insulation test | inspection apparatus when performing insulation monitoring. Explanatory drawing which shows the state in which the insulation defect has arisen in the solar cell module. Explanatory drawing which shows the example of a display of a display device when the insulation defect generate | occur | produces. The measurement result of voltage value V1, V2 and electric current value I1, I2 is a graph. The graph which showed the mode of the said straight line change by the difference in an insulation defect location. The graph which shows the measurement result when an insulation defect is produced in a pseudo manner.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an external view of an insulation inspection apparatus 1 according to the present embodiment. In addition to measuring insulation resistance values, the insulation inspection apparatus 1 has an electronic circuit unit built into the housing 10 that enables the location of insulation failure when a DC power generation unit has insulation failure.

On the operation surface of the housing 10, a display 110, a measurement switch 120, a measurement item / measurement range changeover switch 121, and other switches are provided.
The display device 110 makes it possible to visually grasp the result of the insulation test. For example, in the search for an insulation failure location, an insulation resistance value and an insulation failure monitoring result are displayed. In this embodiment, the insulation failure monitoring result is obtained by emitting light from an LED (light emitting diode) that indicates the relative position of the power generation body causing the insulation failure with respect to the whole of the plurality of power generation bodies constituting the DC power generation unit. And
The measurement switch 120 is a switch for determining measurement contents. Details of the measurement will be described later. The change-over switch 121 is either one of power-off, insulation test (PVH) of high-power DC power generation unit of megawatt class, and insulation test (PVL) of DC power generation unit of relatively low power less than 1000 [W]. This is a switch for selectively switching.

  A P probe 11, an N probe 12, and an E probe 13 are provided at a predetermined portion of the housing 10, for example, at the upper end of the housing 10. The P probe 11 is a probe for abutting the tip portion 501 to one of the pair of output terminals of the DC power generation unit, that is, the positive terminal. The N probe 12 is a probe for clipping the tip portion 502 to the other terminal of the pair of output terminals, that is, the negative terminal. The E probe 13 is a probe for connecting the tip of the E probe 13 to a ground wire (grounding part).

  A configuration example of an electronic circuit unit built in the housing 10 is shown in FIG. The electronic circuit unit includes a CPU (Central Processing Unit) 101 which is a main control circuit. The CPU 101 operates at the timing of the clock output from the oscillator 102. The CPU 101 is connected to a register 103 and a non-volatile memory 104 composed of an EEPROM (Electrically Erasable Programmable Read-Only Memory) or the like.

The memory 104 stores a computer program for searching for defective insulation points that is read and executed by the CPU 101. This computer program defines a control procedure for enabling automatic execution of insulation inspection. Details of the control procedure will be described later. The memory 104 stores a plurality of calculation rules that are read when performing numerical addition / subtraction / division / division and a structure file for storing the structure of the DC power generation unit to be inspected. The memory 104 also stores a measurement file for storing a measurement result described later as digital data, and a reference resistance value R0 for determining that the measured insulation resistance value is normal. The structure file includes, for example, how many DC power generators are connected in series (or in parallel) and how much rated power (or voltage value) is generated.
The register 103 temporarily stores data to be processed by the CPU 101, and functions as a buffer.

  The CPU 101 is connected to the display 110, the measurement switch 120, and the changeover switch 121 shown in FIG. The CPU 101 recognizes the operation contents of the measurement switch 120 and the changeover switch 121 by the user, thereby enabling control for insulation inspection by a sequence procedure. The result of the insulation test is displayed on the display 110.

  The electronic circuit unit also has a driver 130. The driver 130 outputs control signals to the high voltage generation circuit 140 and the input / output circuit 160, respectively, under the control of the CPU 101. The high voltage generation circuit 140 generates a test voltage having a preset value and polarity based on, for example, the voltage supplied from the power supply unit 150 and the control signal, and outputs the test voltage to the input / output circuit 160. Apart from that, it may generate electric power.

  The input / output circuit 160 is electrically connected to the P terminal 12 for connection to the P probe 11, the N terminal 14 for connection to the N probe 12, and the E terminal 16 for connection to the E probe 13. The control signal is used to switch between voltage input and output with the outside or to detect a current. That is, the inspection voltage output from the high voltage generation circuit 140 is supplied to the P probe 11 through the P terminal 12. Further, an analog voltage input via the P terminal 12 and the N terminal 14 or an analog current input via the P terminal 12 / N terminal 14 and the E terminal 16 is detected. Then, these are transmitted to the CPU 101 via a BPF (Band-Pass Filter) and an A / D converter (Analog-to-Digital converter) 180.

Although not shown, an open / close switch for opening / closing an electric circuit between the N terminal 14 and the N probe 12 is inserted and connected to the input / output circuit 160. This open / close switch is an on / off switch that operates in conjunction with the measurement switch 120. For example, when the measurement switch 120 is pressed once (turned on), the open / close switch is turned on, and the electric circuit between the N terminal 14 and the N probe 12 is closed. On the other hand, when the measurement switch 120 is pushed once more (turned off), the open / close switch is turned off and the electric circuit is opened.
As a result, the same effect as when the N probe 12 is removed while the N probe 12 is connected to the N terminal 14 can be obtained, so that the work of connecting and removing the N probe 12 during the insulation test can be reduced.

  The BPF 170 is a band-pass filter for removing noise, and the A / D converter 180 converts an analog signal after noise removal or an analog signal that does not require noise removal into a digital signal that can be processed by the CPU 101.

  The CPU 101 reads and executes a computer program for searching for a defective insulation portion, thereby causing the insulation inspection apparatus 1 to perform control for supplying an inspection voltage, and a differential current value representing a difference between currents flowing through the electric circuit. It functions as current detection means for detecting. Also, it functions as an insulation resistance value deriving means for deriving the insulation resistance value of the electric circuit from the inspection voltage and the differential current value, an inter-terminal voltage value holding means, and an exploration means that makes it possible to determine an insulation failure location. These functions will be described later.

[DC power generation unit]
Here, the DC power generation unit to be inspected of the insulation inspection apparatus 1 will be described. In this embodiment, an example in which the photovoltaic power generation unit shown in FIG. 3 is a DC power generation unit will be given. The solar power generation unit 50 is a unit in which n solar cells 53 each being a power generation body are connected in series and further connected in series in m rows. In other words, the solar cells 53 are arranged in m rows and n columns (n and m are natural numbers of 2 or more), so that it is possible to output large power of several thousand watts or several megawatts at several hundred volts. It is a thing.

Solar cell 53 includes a photoelectric conversion diode as a main element. In addition to having a positive electrode terminal and a negative electrode terminal for each solar cell module, the photovoltaic power generation unit also has a positive electrode terminal 51 and a negative electrode terminal 52 as a whole. Between the solar cell modules, a bypass diode 54 is connected in which the direction of the positive terminal 51 is a cathode and the direction of the negative terminal 52 is an anode. Current flows from the anode toward the cathode. The bypass diode 54 is provided to bypass the solar cell module when the generated voltage in the solar cell module is relatively low due to the influence of the amount of solar radiation.
The DC power generated in the solar power generation unit 50 is converted into AC power by a power conditioner (not shown).

[Insulation inspection method]
Next, an insulation inspection method using the insulation inspection apparatus 1 configured as described above will be described.
It is assumed that the photovoltaic power generation unit 50 to be inspected is installed outdoors and generates a predetermined value of DC power. FIG. 4 is an explanatory diagram showing a connection state of the insulation inspection apparatus 1 to the photovoltaic power generation unit 50 performed outdoors.
At the time of inspection, the user connects the P probe 11, N probe 12, and E probe 13 to the housing 10 as shown in FIG. 1. After cutting off the electric circuit between the photovoltaic power generation unit 50 and the power conditioner 60, the tip 502 of the N probe 12 is clipped to the electric circuit N connected to the negative electrode terminal 52 of the photovoltaic power generation unit 50, and the E probe 13 is Connect to the ground wire (set to ground potential). Then, the tip 501 of the P probe 11 is brought into contact with the electric circuit P connected to the positive electrode terminal 51.

In this state, the user switches the selector switch 121 to search for a defective insulation location (PV). Then, the CPU 101 of the insulation inspection apparatus 1 starts operations as the voltage supply means, the current detection means, the insulation resistance value derivation means, the terminal voltage value holding means, and the exploration means in accordance with the computer program for insulation inspection.
That is, it is assumed that the user presses the measurement switch 120 once (the open / close switch in the input / output circuit 160 is turned on, and the N probe 12 and the N terminal inside the housing 10 are brought into conduction). When recognizing this state, the CPU 101 acquires the voltage value between the positive terminal 51 and the negative terminal 52 of the photovoltaic power generation unit 50. Then, it is stored in the memory 104.
Specifically, the driver 130 and the input / output circuit 160 are controlled to take in the voltage between the electric circuits PN. The captured voltage is denoised by the BPF 170, converted to digital data by the A / D converter 180, and then stored in the measurement file in the memory 104 together with the measurement time output from the timer built in the CPU 101. The voltage value converted into digital data becomes the inter-terminal voltage value V0.

  When the user presses the measurement switch 120 once more, the connection state between the photovoltaic power generation unit 50 and the insulation inspection apparatus 1 is as shown in FIG. The CPU 101 recognizes this connection state (a state where the above open / close switch is turned off and the N probe 12 and the N terminal inside the housing 10 are in a non-conductive state). Then, the high voltage generation circuit 140 and the input / output circuit 160 are controlled through the driver 130 to supply the positive first inspection voltage to the P terminal 12. The voltage value of the first inspection voltage at this time is V1.

  The first inspection voltage supplied to the P terminal 12 is supplied (applied) to the positive electrode terminal 51 of the photovoltaic power generation unit 50 through the tip 501 of the P probe 11 and the electric circuit P. As described above, the photovoltaic power generation unit 50 is an ungrounded electric circuit. Therefore, normally, no current flows through the photovoltaic power generation unit 50 unless a part of the electric circuit is short-circuited. However, by connecting the tip portion 501 of the P probe 11, a current flows between each solar cell module constituting the solar power generation unit 50 and the ground wire E. The CPU 101 causes the input / output circuit 160 to detect this current through the E probe 13 and the E terminal 16, and converts the current into digital data by the A / D converter 180. The current value converted into digital data is I1. The CPU 101 stores the current value I1 in the measurement file in the memory 104 together with the voltage value V1 of the first inspection voltage and the measurement time.

  The reason why the first inspection voltage is supplied to the electric circuit between the positive electrode terminal 51 of the photovoltaic power generation unit 50 and the grounded part is to reduce the amplitude of the voltage appearing at the positive electrode terminal 51 and thereby reduce the leakage current. It is. Another reason is to suppress the influence of the bypass diode 54. That is, in the solar power generation unit 50, the solar cell modules are connected by the bypass diode 54. The bypass diode 54 has its cathode connected to the positive terminal of each solar cell module and its anode connected to the negative terminal. Therefore, when the current flowing through the electric path between the positive electrode terminal and the negative electrode terminal of a certain solar cell module passes through the bypass diode 54, the solar cell 53 in the solar cell module is bypassed. As a result, it becomes impossible to search for an insulation defect point described later. Therefore, in the present embodiment, the first inspection voltage is supplied to the positive terminal 51. The first inspection voltage is a voltage having a value that, when added to the voltage appearing at the positive electrode terminal 51, has an amplitude that exceeds zero and is less than the amplitude of a voltage that can be generated by the photovoltaic power generation unit 50. That is, the voltage is supplied so as to cancel the voltage appearing at the positive terminal 51.

When the storage of the voltage value V1 of the first inspection voltage and the detected current value I1 in the memory 140 is completed, the CPU 101 causes the P terminal 12 to supply a second inspection voltage having a voltage value different from the first inspection voltage. When the second inspection voltage is also added to the voltage appearing at the positive electrode terminal 51, the amplitude of the second inspection voltage exceeds zero and is a voltage having a value less than the amplitude of the voltage that can be generated in the photovoltaic power generation unit 50. The same as in the case of the first inspection voltage.
The voltage value of the second inspection voltage is V2.

  The second inspection voltage supplied to the P terminal 12 is supplied to the positive electrode terminal 51 of the photovoltaic power generation unit 50 through the tip 501 of the P probe 11 and the electric circuit P. Thereby, a current flows between each solar cell module of the photovoltaic power generation unit 50 and the ground wire E. This current is detected by the input / output circuit 160 through the E probe 13 and the E terminal 16 and converted into digital data by the A / D converter 180. The current value converted into digital data is I2. The CPU 101 stores the current value I2 in the measurement file of the memory 104 together with the voltage value V2 of the second inspection voltage and the measurement time.

When the inter-terminal voltage value V0, the voltage values V1 and V2, and the current values I1 and I2 are stored in the measurement file, the CPU 101 performs the following control procedure to derive the insulation resistance value and search for an insulation failure location. Do.
For example, as shown in FIG. 6, in the solar cell modules arranged in 30% of the solar cell modules connected in series in m rows as seen from the positive electrode terminal 51 of the photovoltaic power generation unit 50. It is assumed that an insulation failure occurs and the insulation resistance value becomes Rx. Further, a virtual voltage value from the defective insulation portion 500 to the positive electrode terminal 51 is set to Vx. In this case, the following relational expression holds between the various data.

I1 = (V1-Vx) / Rx (1)
I2 = (V2-Vx) / Rx (2)
From equations (1) and (2)
Vx = V1-I1 · Rx
= V2-I2 ・ Rx (3)
Rx = (V2-V1) / (I2-I1) (4)
Vx = V1-I1. (V2-V1) / (I2-I1)
= V2-I2 · (V2-V1) / (I2-I1) (5)

The CPU 101 derives the insulation resistance value Rx from the above equation (4). Further, the virtual voltage value Vx and the inter-terminal voltage value V0 are compared, and based on the comparison result and the structure file stored in the memory 104, a plurality of solar cell modules are passed from the positive terminal 51 of the photovoltaic power generation unit 50. It is possible to determine the location of insulation failure in the path to the negative terminal 52. If it can be determined, the insulation failure location is displayed on the display 110. In this example, the virtual voltage value Vx is 30% of the inter-terminal voltage value V0. Therefore, it is possible to determine that the solar cell modules arranged in 30 [%] of the whole (m rows) from the positive electrode terminal 51 as defective insulation locations. Thereafter, as shown in FIG. 7, the CPU 101 causes the third LED out of 10 to emit light starting from “P” that is the positive electrode terminal 51.
In addition, if the number of LEDs is increased, the insulation failure location can be displayed more finely. For example, it is possible to determine which insulation failure has occurred in which solar battery cell 53 of which solar battery module among the solar battery cells 53 constituting the solar battery module.

  Insulation failure locations other than the portion shown in FIG. 6 are determined as follows. That is, when the virtual voltage value Vx is zero, the positive terminal 51 is referred to with reference to FIG. 6, and therefore the positive terminal 51 is determined as a location where an insulation failure has occurred. When the virtual voltage value Vx is equal to the inter-terminal voltage value V0, it is determined that an insulation failure has occurred at the negative terminal 52.

  In addition, when it can be determined that the insulation resistance value Rx derived from the above equation (4) does not clearly cause an insulation failure as compared with the reference resistance value R0, the CPU 101 determines whether or not the virtual voltage value Vx is a voltage value. Stop exploring for poor insulation. In this case, no LED on the display 110 emits light.

  FIG. 8 is a graph of the measurement results of the voltage values V1 and V2 and the current values I1 and I2 of each inspection voltage. In FIG. 8, the horizontal axis represents the voltage value V of the inspection voltage (applied voltage) supplied to the positive terminal 51 of the photovoltaic power generation unit 50. The vertical axis represents current values I (I1, I2) of currents flowing between the photovoltaic power generation unit 50 and the ground wire when the applied voltages are V1 and V2. When the measurement point that becomes the current value I1 when the inspection voltage of the voltage value V1 is supplied is Q1, and the measurement point that becomes the current value I2 when the inspection voltage of the voltage value V2 is supplied is Q2, Q1 and Q2 (Hereinafter referred to as “characteristic straight line”) can be expressed by the following equation.

I = (V / Rx) − (Vx / Rx) (6)
The change slope of the characteristic line is the insulation resistance value Rx, and the voltage value when the characteristic value intersects with the horizontal axis, that is, the voltage value when the current value I (I1, I2) changes from a valid value to a zero value is the virtual voltage value Vx. Become. Equation (6) can also be derived by modifying equation (1).
In this way, the virtual voltage value Vx may be calculated from the equation (5), but the voltage value when the current value I changes from a valid value to a zero value based on the gradient of the characteristic line in the equation (6) is calculated. It can also be derived as a virtual voltage value Vx. At this time, if the insulation resistance value derived from the change slope of the characteristic line of equation (6) is equal to or greater than the above-described reference resistance value R0, it is determined that there is no insulation failure at that time, and the insulation at that time The resistance value is displayed on the display 110, and the search for the insulation failure portion can be completed.

FIG. 9 is a graph showing how the characteristic straight line changes due to differences in insulation failure locations. The horizontal axis represents the voltage value (V) of the inspection voltage (applied voltage) supplied to the positive terminal 51, and the vertical axis represents the current value (I). When the positive electrode terminal 51 of the photovoltaic power generation unit 50 has poor insulation, as indicated by the broken line, the current value I is equal to any change gradient as long as the change gradient of the characteristic line is less than the reference resistance value R0. The virtual voltage value Vx when the value changes from zero to zero becomes zero.
Similarly, when the negative electrode terminal 52 is poorly insulated, the virtual voltage value Vx becomes the same value as the inter-terminal voltage value V0 as shown by the alternate long and short dash line, and when any of the solar cell modules is poorly insulated, the solid line As shown, the virtual voltage value Vx becomes the inter-terminal voltage value V0.
In other words, what is important in the search for insulation failure is the change slope of the characteristic line. If this change slope can be specified, the voltage values V1, V2 and current values I1, I2 If it is within a predetermined time, it does not matter whether it is large or small.

  FIG. 10 is a graph showing the results of a demonstration experiment when a pseudo insulation failure is caused. The demonstration experiment is directed to a photovoltaic power generation unit 50 having a DC voltage value to be generated, that is, a terminal voltage value V0 of 386 [V], and sunlight is applied to the entire light receiving surface of the photovoltaic power generation unit 50. I went there. The pseudo insulation failure is caused by selectively connecting the other end of the insulation resistor having a resistance value of 1 [kΩ] and having one end connected to the ground wire to the positive terminal 51 and the negative terminal 52. I am letting. The inspection voltage was supplied only to the positive terminal 51 for the reason described above.

The horizontal axis in FIG. 10 is the voltage value (V) of the inspection voltage supplied to the positive terminal 51, and the vertical axis is the current value (μA) of the leakage current flowing through the photovoltaic power generation unit 50. Note that the current value at this time can also be derived by measuring the voltage [mV] at both ends of the insulation resistor.
The inspection voltage applied to the positive terminal 51 was supplied 10 times or more at different voltage values. However, as shown in FIG. 10, the change slope of the characteristic line representing the change in current is constant regardless of the number of times. It was. The virtual voltage value Vx when the positive terminal 51 is poorly insulated is 0 [V], and the virtual voltage value Vx when the negative terminal 52 is poorly insulated is 386 [V], which is the same as the inter-terminal voltage V0. It was proved. On the other hand, even if the polarity of the inspection voltage supplied when the negative electrode terminal 52 is poorly insulated is negative (minus), it has the same change gradient as in the case of positive (plus), and the virtual voltage value V0 having the same value is obtained. It was. That is, it is not limited to the case where the positive (plus) inspection voltage (voltage values V1, V2) is supplied to the photovoltaic power generation unit 50, and it is understood that a negative (minus) inspection voltage may be supplied. .

  As described above, in this embodiment, the insulation inspection apparatus 1 applies the inspection voltage to the electric circuit between the positive electrode terminal 51 or the negative electrode terminal 52 of the photovoltaic power generation unit 50 and the ground portion at least twice at a predetermined time interval. , Supplied at different values (first inspection voltage, second inspection voltage). Each of these inspection voltages is a voltage that reduces the amplitude of the voltage appearing at the positive terminal 51 or the negative terminal 52. And when the value of the supplied inspection voltage changes, a differential current value representing a difference between leakage currents flowing in the electric circuit is detected, and based on the current difference value and a differential voltage value representing a difference between the changed inspection voltages. The insulation resistance value of the electric circuit is derived.

  For example, referring to FIG. 10, it is assumed that the generated voltage of the photovoltaic power generation unit 50 is 400 [v], an insulation failure occurs on the N terminal 52 side, and the insulation resistance value Rx at that time is 0.1 [MΩ]. . In this case, if the inspection voltage is not supplied (for example, when the inspection voltage is zero in the invention disclosed in Patent Document 2), a leakage current of 4 [mA] flows in the electric circuit and the insulation inspection device 1. On the other hand, as in the present embodiment, the first inspection voltage V1 of 250 [v] and the second inspection voltage V2 of 500 [v] are applied to the positive terminal 51 so that the positive terminal 51 becomes positive, respectively. Leakage current is suppressed when supplied to the grounded part. That is, the leakage current (first current) I1 that flows when the first inspection voltage V1 is supplied is 1.5 (= (400−250) / 100) [mA]. Further, the leakage current (second current I2) that flows when the second inspection voltage V2 is supplied is −1.0 (= (400−500) / 100) [mA].

  In this way, by supplying the inspection voltage, the leakage current flowing inside the electric circuit and the insulation inspection apparatus 1 becomes smaller than when the inspection voltage is not supplied. Therefore, it is possible to suppress the influence on the power generation equipment side caused by the leakage current. Further, since there is no need to incorporate a large-capacity resistor in the insulation inspection apparatus 1, the instrument body can be easily reduced in size and weight, and the workability during insulation inspection can be improved.

  In the insulation inspection apparatus 1 according to the present embodiment, the virtual voltage value Vx and the inter-terminal voltage value V0 are compared, so that in the path from the positive terminal 51 to the negative terminal 52 through a plurality of photovoltaic modules or cells. Made it possible to determine where insulation is defective. Therefore, as shown in FIG. 3, even in the photovoltaic power generation unit 50 that is composed of a huge number of solar cells 53 or in which a plurality of solar cell modules are connected in series, the insulation failure location is almost pinpointed. Can be determined.

  In addition, when there is an insulation failure location in the path, the display 110 has a display 110 that visually indicates the insulation resistance value Rx at that time and the relative position of the insulation failure location, so that the insulation failure state can be grasped intuitively. Can do.

  In addition, in the insulation inspection apparatus 1 according to the present embodiment, in addition to the P probe 11, the N probe 12, and the E probe 13, an open / close switch for opening / closing an electric circuit between the N terminal 14 and the N probe 12 is inserted and connected. Yes. Then, by turning on the open / close switch with the P probe 11 connected to the positive terminal 51, the N probe 12 connected to the negative terminal 512, and the E probe 13 connected to the grounded portion, the voltage value V0 between the terminals is reduced. Allows acquisition. In addition, the value of each current can be obtained by turning off the open / close switch. Thereby, the work which removes each probe 11, 12, 13 can be abbreviate | omitted in the case of an insulation test | inspection, and workability | operativity can be improved significantly.

  Note that the supply of the inspection voltage and the measurement of the current value at that time may be supplied not only twice but also at a different voltage value three times or more, and the current value at that time may be measured. In this way, the change slope of the above characteristic line becomes more accurate.

  The present invention can be similarly applied to DC power generation units other than the solar power generation unit 50.

  DESCRIPTION OF SYMBOLS 1 ... Insulation inspection apparatus, 10 ... Case, 110 ... Display, 120 ... Measurement switch, 121 ... Changeover switch, 11 ... P probe, 12 ... N probe, DESCRIPTION OF SYMBOLS 13 ... E probe, 101 ... CPU, 140 ... High voltage generation circuit, 160 ... Input / output circuit, 180 ... A / D converter.

The insulation inspection method of the present invention is a method for measuring voltage and current in a power generation system having a DC power generation unit to which a plurality of power generation bodies are connected and a load connected to a pair of output terminals of the DC power generation unit. The method is implemented by a device capable of: cutting off the load from the pair of output terminals, obtaining a voltage value between terminals of the pair of output terminals from which the load is cut off, and the load A test voltage for reducing the amplitude of the voltage appearing at the terminal on the electric circuit between any one of the paired output terminals and the grounded portion is set to a different value at least twice at a predetermined time interval. supplied, thereby detects the differential current value representing the difference of the current flowing in said path, said current based on the other change gradient for one of the differential current value and the differential voltage value A step of deriving a virtual voltage value when the value changes from a valid value to a zero value, and comparing the virtual voltage value with the voltage value between the terminals, thereby generating the plurality of power generations from one terminal of the output terminal. And a step of making it possible to determine a location of defective insulation in a path leading to the other terminal of the output terminal through the body .

The insulation inspection apparatus of the present invention obtains a voltage between terminals of a pair of output terminals in a state where a load is cut off from a pair of output terminals included in a DC power generation unit having a plurality of power generators connected thereto. A value holding means and a test voltage having a value for reducing the amplitude of the voltage appearing on the terminal in the electric circuit between any one of the pair of output terminals and the grounded part in a state where the load is cut off are predetermined. A voltage supply means for supplying a different value at least twice at a time interval; and a current detection means for detecting a differential current value representing a difference in current flowing in the electric circuit when the value of the supplied test voltage changes. A virtual voltage value when the current value changes from a valid value to a zero value based on the other change gradient with respect to one of the differential voltage value and the differential current value, and the virtual voltage value and the terminal voltage Compare with value And by a device having a search means for enabling discrimination poor insulation portion in the path to the other terminal of said output terminals from one terminal of the output terminals through said plurality of power generators.

In insulation test method and insulation test apparatus of the present invention, by comparing the virtual voltage value and the inter-terminal voltage value of the DC power generating unit, it is possible to identify the relative position of the insulating defective portion, insulating a simple technique It is possible to search for defective parts.

The insulation inspection method of the present invention is a method for measuring voltage and current in a power generation system having a DC power generation unit to which a plurality of power generation bodies are connected and a load connected to a pair of output terminals of the DC power generation unit. The method is implemented by a device capable of performing the steps of: cutting off the load from the pair of output terminals; obtaining a voltage value between terminals of the pair of output terminals at which the load is cut off; and the load An inspection voltage that reduces a leakage current flowing through the grounding part by reducing the amplitude of the voltage appearing on the terminal on the electric circuit between any one of the pair of output terminals and the grounding part, two or more times at predetermined time intervals, and supplies at different values, thereby differential electrostatic representing the difference voltage of the differential current value and the different values representing the difference of the current flowing in the path Detects the value, and deriving a virtual voltage value when the value of the current falls to zero value from the organic value based on the other of the change gradient for one of the differential current value and the differential voltage value, the By comparing the virtual voltage value and the inter-terminal voltage value, it is possible to determine an insulation failure location in a path from one terminal of the output terminal to the other terminal of the output terminal through the plurality of power generators. The method which has a process to do.

The insulation inspection apparatus of the present invention obtains a voltage between terminals of a pair of output terminals in a state where a load is cut off from a pair of output terminals included in a DC power generation unit having a plurality of power generators connected thereto. Leakage current that flows through the grounding part by reducing the amplitude of the voltage appearing on the terminal between the value holding means and one of the pair of output terminals with the load cut off and the grounding part. A voltage supply means for supplying a test voltage with a different value at least twice at a predetermined time interval, and a differential current representing a difference between currents flowing in the electric circuit when the value of the supplied test voltage changes current detecting means for detecting a differential voltage value representing a difference between the value different from the value of the voltage, the value of the current based on the other change gradient for one of the differential current value and the differential voltage value is Yes Deriving a virtual voltage value when the zero value is obtained from the output voltage, and comparing the virtual voltage value with the voltage value between the terminals, the output terminal from one terminal of the output terminal through the plurality of power generators And an exploration means that makes it possible to determine the location of insulation failure in the path leading to the other terminal.

The insulation inspection method of the present invention is a method for measuring voltage and current in a power generation system having a DC power generation unit to which a plurality of power generation bodies are connected and a load connected to a pair of output terminals of the DC power generation unit. The method is implemented by a device capable of: cutting off the load from the pair of output terminals, obtaining a voltage value between terminals of the pair of output terminals from which the load is cut off, and the load When the sum of the voltage appearing on the terminal is added to the electric circuit between one of the pair of output terminals and the grounded portion , the amplitude exceeds zero, and the DC power generation unit generates power. possible voltage test voltage which is less than the amplitude, more than once in a predetermined time interval, the amplitude of the current flowing through the electrical path is supplied at different values smaller than the previous, to A differential current value representing a difference between currents flowing in the electric circuit and a differential voltage value representing a difference between the different voltage values, and based on the other change gradient with respect to one of the differential voltage value and the differential current value. A step of deriving a virtual voltage value when the current value changes from a valid value to a zero value, and comparing the virtual voltage value with the voltage value between the terminals, from one terminal of the output terminal And a step of making it possible to determine an insulation failure location in a path leading to the other terminal of the output terminal through a plurality of power generators.

The insulation inspection apparatus of the present invention obtains a voltage between terminals of a pair of output terminals in a state where a load is cut off from a pair of output terminals included in a DC power generation unit having a plurality of power generators connected thereto. When the voltage holding means and the voltage appearing on the terminals are added to the electric circuit between one of the pair of output terminals and the grounded part in a state where the load is cut off , the amplitude exceeds zero. In addition, the inspection voltage that is less than the amplitude of the voltage that can be generated in the DC power generation unit is supplied at different values so that the amplitude of the current flowing in the electric circuit is smaller than the previous time at a predetermined time interval twice or more. And a differential current value representing a difference between currents flowing through the electric circuit when a value of the supplied inspection voltage changes and a differential voltage value representing a difference between the different voltage values are detected. Deriving a virtual voltage value when the current value changes from a valid value to a zero value based on the current detection means and the other change gradient with respect to one of the differential voltage value and the differential current value, and the virtual voltage value Exploring means that makes it possible to determine an insulation failure location in a path from one terminal of the output terminal to the other terminal of the output terminal through a plurality of power generators by comparing the voltage value between the terminals; .

Claims (8)

A method executed by a device capable of measuring voltage and current in a DC power generation unit to which a plurality of power generation bodies are connected,
The test voltage for reducing the amplitude of the voltage appearing at the terminal is more than twice at a predetermined time interval on the electric circuit between any one of the pair of output terminals of the DC power generation unit and the grounding portion, at a predetermined time interval, Supplying each with a different value, thereby detecting a difference current value representing a difference in current flowing in the electric circuit;
Deriving an insulation resistance value of the electric circuit based on the current difference value and a difference voltage value representing a difference between the inspection voltages changed.
Insulation inspection method. The inspection voltage supplied twice or more is a voltage whose value exceeds the amplitude of zero when combined with the voltage appearing at the terminal and less than the amplitude of the voltage that can be generated in the DC power generation unit. Each is supplied to cancel the voltage appearing at each of the terminals,
The insulation inspection method according to claim 1. Acquiring the inter-terminal voltage value of the pair of output terminals, and storing the acquired inter-terminal voltage value;
Based on the other change gradient with respect to one of the differential voltage value and the differential current value, a virtual voltage value when the current value changes from a valid value to a zero value is derived, and the virtual voltage value and the stored value are stored. A step of making it possible to determine an insulation failure location in a path from one terminal of the output terminal to the other terminal of the output terminal by comparing the voltage value between the terminals through the plurality of power generators. Including,
The insulation inspection method according to claim 1 or 2. A test voltage having a value that reduces the amplitude of the voltage appearing on the terminal is connected to a ground line between one of the pair of output terminals of the DC power generation unit connected to the plurality of power generators and the ground portion. Voltage supply means for supplying different values at a predetermined time interval twice or more;
Current detection means for detecting a difference current value representing a difference in current flowing in the electric circuit when the value of the supplied inspection voltage changes; and
Insulation resistance value deriving means for deriving an insulation resistance value of the electric circuit based on the current difference value and a difference voltage value representing a difference between the changed inspection voltages,
Insulation inspection device. An inter-terminal voltage value holding means for acquiring an inter-terminal voltage value between the pair of output terminals and storing the acquired inter-terminal voltage value;
Based on the other change gradient with respect to one of the differential voltage value and the differential current value, a virtual voltage value when the current value changes from a valid value to a zero value is derived, and the virtual voltage value and the stored value are stored. By comparing the voltage value between the terminals, the exploration means that makes it possible to determine the location of insulation failure in the path from one terminal of the output terminal through the plurality of power generators to the other terminal of the output terminal;
The insulation inspection apparatus according to claim 4, further comprising: Further having a display that visually represents the relative position of the insulation failure location when there is the insulation failure location in the path;
The insulation inspection apparatus according to claim 5. Displaying the insulation resistance value derived by the insulation resistance value deriving means together with the relative position on the display unit;
The insulation inspection apparatus according to claim 6. A first probe connecting one of the pair of output terminals and the voltage supply means;
A second probe connecting the other of the pair of output terminals and the voltage supply means;
A third probe connecting the grounding part and the current detection means;
An open / close switch inserted and connected between the second probe and the voltage supply means;
Enabling the voltage value between the terminals by turning on the open / close switch,
Enabling the value of the current flowing through the electric circuit by turning off the open / close switch,
The insulation inspection apparatus according to any one of claims 4 to 7.

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