JP6691801B2 - Photovoltaic voltage tester and photovoltaic panel voltage measuring method - Google Patents

Description

  The present invention relates to a photovoltaic power generation system capable of preventing electric shock due to power generation by a photovoltaic panel and a method for measuring a generated voltage of a photovoltaic panel.

  In general solar power generation systems for homes, etc., a solar cell array consisting of solar cell modules connected in series and parallel (hereinafter, this solar cell array is referred to as a solar panel) is installed on the roof of the house. Has been done. Then, the output from the solar panel is connected to a power conditioner via a connection box, and is configured to obtain desired power (see, for example, Patent Document 1).

JP, 2013-110290, A JP, 2005-014709, A Japanese Patent Application No. 2015-131943

National Institute for Occupational Safety and Health Research Institute Safety Data, JNIOSH-SD-No. 25 (2009), "Basics of electric shock and statistics of fatal accidents in the past 30 years"

However, the related art has the following problems.
Such a solar power generation system is said to be maintenance-free and is becoming popular. On the other hand, with the increase in the number of popularized vehicles, the number of fires caused by the photovoltaic power generation system (for example, abnormal heat generation and fires due to defective products of solar cell modules that make up solar panels, deterioration over time, construction defects, etc.) It's a problem.

  Even if the solar cell module has a defect, the solar power generation system generates power when the sun is out, and a voltage and current of several 100V and several 10A are generated. Therefore, if the solar panel is irradiated with light, power is always generated, and a failure in the solar panel may lead to a fire. Therefore, it is important to quickly detect such abnormal heat generation and fire of the solar panel.

  Furthermore, when the insulation of the photovoltaic power generation system is damaged due to the burning of a fire in a state where power generation is continuing, there is a risk of electric shock to surrounding people due to water discharge during fire extinguishing activities. That is, when a fire occurs in the installation environment of the photovoltaic power generation system, there is a problem that the power generation of the photovoltaic panel must be stopped first.

  To address such a problem, the applicant of the present application has proposed an invention in which a light-shielding agent is applied to the surface of a solar panel to block incident light (for example, refer to Patent Document 2). In Patent Document 2, a light-shielding agent having a thixotropic property is radiated to a solar panel which is a target surface in a liquefied state due to a decrease in viscosity, and a light-shielding agent which is changed into a solid state due to an increase in viscosity is targeted. By covering the surface of the object, the light incident on the surface of the target is quickly blocked.

  However, in order to eliminate the risk of electric shock to people in the vicinity due to water discharge during fire fighting activities, it is necessary to further confirm that the power generation voltage of the solar panel has dropped below the allowable voltage level at which there is no risk of electric shock. It is important to detect reliably and easily in the installation environment.

  The present invention has been made to solve the above problems, and easily detects by field work whether or not the power generation voltage of a solar panel has dropped to an acceptable level for electric shock of a human body. An object of the present invention is to obtain a photovoltaic power generation voltage tester and a method for measuring a photovoltaic power generation voltage of a photovoltaic panel that can be used.

The solar power generation voltage tester according to the present invention is a solar power generation voltage tester that measures that the direct current voltage by the solar panel is equal to or lower than the allowable voltage that does not cause electric shock, and corresponds to the electrical resistance of the human body. Measuring the voltage across a series circuit consisting of a resistor and a contact, and a relay circuit that has a resistor with a resistance value and a contact that is connected in series with the resistor and that can switch between open and closed states. When measuring the voltmeter and the voltage at both ends, the relay circuit is controlled so as to switch the contacts to the closed state, and the voltage at both ends measured by the voltmeter is specified by the allowable heat generation amount of the resistor. And a controller that controls the relay circuit so as to switch the contact to an open state when the voltage exceeds the threshold voltage of the second voltage. of A case where the value voltage or lower, in the case of more than the second threshold voltage, shall control the display unit to the different display.

Further, the method for measuring the generated voltage of the solar panel according to the present invention, the DC voltage by the solar panel, by the controller included in the solar power generation voltage tester that measures that the allowable voltage is less than the risk of electric shock A method for measuring the generated voltage of a solar panel, which is a voltage across a series circuit consisting of a resistor having a resistance value corresponding to the electric resistance of the human body and a contact point that can control switching between open and closed states. When measuring the voltage, switch the contact to the closed state to measure the voltage across the voltage, and to switch the contact between the open state and the closed state periodically, the calorific value of the resistor becomes the allowable calorific value. In order to fit it, measurement is performed by a storage step that stores in advance a table that defines the correspondence relationship between the closed state period within one cycle and the voltage across both ends, and the voltage measurement step. Is the ratio extracted from the table according to the magnitude of the voltage across, by switching the contacts periodically by extracted ratio, and the period control step of measuring the repetition voltage across both ends voltage measured by the voltage measurement step Has a display step of controlling the display so as to display differently depending on whether the voltage is equal to or lower than the second threshold voltage defined by the allowable voltage or exceeds the second threshold voltage .

  According to the present invention, the power generation voltage of the solar panel can be quickly measured in consideration of the resistance value of the human body. As a result, it is possible to easily detect by site work whether the voltage generated by the solar panel has fallen to an acceptable level for electric shock to the human body. You can get the way.

It is a block diagram of the general photovoltaic power generation system in which this invention is used. It is explanatory drawing shown about the reaction of a human body with respect to a direct current. It is the figure which showed the terminal voltage at the time of 500-ohm load by the difference of the short circuit current of the solar panel in Embodiment 1 of this invention. It is explanatory drawing which shows the voltage measurement circuit of the solar power generation voltage tester in Embodiment 1 of this invention. It is a functional block diagram of the photovoltaic power generation voltage tester in Embodiment 1 of the present invention. 5 is a flowchart relating to a solar panel power generation voltage measurement process executed by a controller in the solar power generation voltage tester according to the first embodiment of the present invention.

  Hereinafter, preferred embodiments of a photovoltaic power generation voltage tester and a photovoltaic power generation voltage measuring method of the present invention will be described with reference to the drawings.

Embodiment 1.
First, a solar power generation system in which the present invention is used will be described below. FIG. 1 is a configuration diagram of a general photovoltaic power generation system in which the present invention is used. The solar power generation system is configured to include a solar panel 1, a junction box 2, a power conditioner 3, a distribution board 4, and a power selling meter 5.

  The solar panel 1 converts light energy from the sun into electric power and outputs it as DC power. The two solar panels 1 shown in FIG. 1 are connected to the connection box 2 via the respective input electric wires L1 and output the generated power to the connection box 2.

  The junction box 2 collects the DC power generated by the solar panel 1. That is, when a plurality of solar panels 1 are installed as shown in FIG. 1, the junction box 2 collects electric power from each solar panel 1. Further, the junction box 2 is connected to the power conditioner 3 via the output electric wire L2, and outputs the collected DC power to the power conditioner 3.

  The power conditioner 3 is a power conversion device that converts input DC power into AC power. Further, the power conditioner 3 has a function of stably outputting electric power in response to the power generation amount of the solar panel 1 which changes depending on time and weather. And the power conditioner 3 is connected to the distribution board 4 installed indoors via the connection line L3.

  The distribution board 4 is a device that transmits the electric power converted into alternating current by the power conditioner 3 so that it can be used at home. In addition, in a solar power generation system in which a system for buying and selling power is introduced, the distribution board 4 sends power to the home when the power in the home is insufficient, and the power in the home is sufficient. When it is present, the electric power is sent to the electric power company through the power selling meter 5.

  Next, a current flowing through the human body due to electric shock will be described with reference to the drawings. FIG. 2 is an explanatory view showing the reaction of the human body with respect to a direct current, and is based on FIG. 5 described on page 12 of Non-Patent Document 1. More specifically, it represents the reaction when a current flows from the left hand through both legs. Further, the vertical axis in FIG. 2 represents the energization time (ms), and the horizontal axis represents the magnitude of current (mA).

In FIG. 2, the degree of influence of electric shock on the human body is divided into four categories, DC-1 to DC-4, and DC-4 is further subdivided into three categories. Means the content of.
-DC-1: Area where there is usually no reaction and slight stinging pain-DC-2: Area where there are usually no harmful physiological effects-DC-3: Possibility of recoverable and transmission disorders in the heart There is a region-DC-4: a region in which dangerous pathophysiological symptoms, such as severe burns, are expected DC-4-1: A region in which the probability of ventricular fibrillation is about 5% or less DC-4-2: Ventricular fibrillation probability is about 50% or less DC-4-3: Ventricular fibrillation probability is about 50% or more

  From FIG. 2, it can be seen that when the current flowing through the human body is 20 mA or less, it is included in the region where DC-2 does not normally have a harmful physiological effect. On the other hand, the electric resistance of the human body changes depending on the dry state of the skin and the magnitude of the voltage (contact voltage) when the battery contacts the charged part. When the skin is dry, there is a skin resistance, and the electric resistance of the human body is several kΩ or more. On the other hand, when the skin gets completely wet due to perspiration, the electric resistance of the skin approaches 0Ω without limit.

  As a result, although the electrical resistance of the human body varies depending on the current-carrying path, considering the worst case, it is considered that the internal resistance alone is about 500Ω. For example, assuming that a 500 Ω human body contacts a 200 V DC charging part, a current of 400 mA will flow through the body.

  As a result, it becomes difficult to separate from the charged part due to muscle contraction, etc., and if current flows for 0.5 seconds or more, ventricular fibrillation may occur and death may occur. From this viewpoint, it can be understood that the voltage of DC200V is dangerous to the human body.

  Therefore, the solar power generation voltage tester according to the first embodiment accurately measures the generated voltage assuming that the electrical resistance of the human body is 500Ω when measuring the generated voltage of the solar panel. It is characterized by doing.

  Next, the effect of applying the light-shielding agent of Patent Document 2 described above to a solar panel in a situation where it is desired to stop the power generation of the solar panel will be described. FIG. 3 is a diagram showing a terminal voltage when a 500 Ω load is caused by a difference in short-circuit current of the solar panel according to the first embodiment of the present invention.

  It is assumed that the solar panel 1 according to the first embodiment has a performance capable of flowing up to 10 A at the rated output. The maximum value of the open circuit voltage at the rated output is about 250V DC. Then, at this rated output, a current of 0.49 A flows and a voltage of 245 V is applied to a 500Ω load.

  On the other hand, in the case of 1/50 light shielding, the current is suppressed to 0.2 A, which is 1/50 of the rated output, but the open circuit voltage is hardly reduced. However, when the light is shielded at 1/50, the current is suppressed to 0.2A, so that a current of 0.2A flows to a load of 500Ω and a voltage of 100V is applied.

  Further, in the case of 1/500 light shielding, the current is suppressed to 0.02A which is 1/500 of the rated output, but the open circuit voltage is hardly reduced. However, when the light is shielded for 1/500, the current is suppressed to 0.02A, so that a current of 0.02A flows to a load of 500Ω and a voltage of 10V is applied.

Therefore, at the rated output, 1/50 light-shielding, and 1/500 light-shielding shown in FIG. 3, the power due to the 500Ω load is as follows.
・ At rated output: 0.49A × 245V = 120W
・ When shielding 1/50: 0.2A × 100V = 20W
・ When shaded at 1/500: 0.02A × 10V = 2W

  Here, consider heat generation when a resistance of 500Ω is incorporated in the tester. At the rated output, the resistance of 500Ω consumes 120 W of electric power, and the resistance becomes extremely high. On the other hand, when the light is shielded at 1/50 and 1/500, the power consumption can be suppressed to 20 W and 2 W, respectively, so that the resistance can be suppressed from becoming higher than that at the rated output. As a result, a small resistor can be adopted by considering the power consumption.

  FIG. 4 is an explanatory diagram showing a voltage measuring circuit 21 described later of the photovoltaic power generation voltage tester according to Embodiment 1 of the present invention. The voltage measuring circuit shown in FIG. 4 includes terminals 11, 12, a resistor 13, a contact 14, and a voltmeter 15. The terminals 11 and 12 are connected to both ends of the voltage measurement object. The resistor 13 and the contact 14 form a series circuit, and the voltage across the resistor 13 is measured by the voltmeter 15. Here, the contact 14 in FIG. 4 is described as a normally open contact, but it is also possible to adopt a normally closed contact depending on the circuit configuration.

  Note that, although details are omitted, the applicant of the present application makes the needle-shaped measuring terminal bite into the coating of the electric wire (for example, the output wire L2) that transmits the DC power generated by the solar panel, thereby Patent application 3 has already applied for a voltage measuring device that allows an operator to measure the voltage of an electric wire by performing a simple work at the site by contacting the conductor wire with the above-mentioned technique. Can be used for.

  As the resistor 13, a small resistor of 500Ω is used, which assumes the minimum value of the electric resistance of the human body. The contact 14 is a relay contact included in the relay circuit 22 of FIG. 5, which will be described later, and is a relay contact that is opened when the coil of the relay circuit 22 is in a non-excited state and closed when it is in an excited state. is there.

  As described above, the power consumed by the resistor 13 varies depending on the light-shielding state of the solar panel, and when the light-shielding is not sufficient, there is a possibility that heat generation will exceed the allowable heat generation amount of the resistor 13. Therefore, in the present invention, the contact 14 is closed only when it is desired to measure the voltage, and when the measured voltage value exceeds a preset allowable value, the contact 14 is prevented in order to prevent heat generation in the resistor 13. Opening / closing control is performed so as to switch to the open state.

Assuming that the allowable value for judging the switching to the open state is DC30V, a current of 60 mA flows through the 500Ω resistor, and the resistor 13 is
30V x 0.06A = 1.8W
It is possible to use a small resistor that can consume the maximum power specified by.

  Also, when measuring a voltage higher than the allowable value, the ON / OFF state of the relay is periodically switched, and the period in which the contact 14 is not turned on, that is, the period in which heat does not flow through the resistor 13 and heat generation is suppressed, By providing a small resistance of 1.8 W, it becomes possible to measure a voltage exceeding 30 V.

  The voltmeter 15 can measure the voltage applied to the resistor 13 when the contact 14 is closed. As described with reference to FIG. 2 above, if the current flowing through the human body is 20 mA or less, there is usually no harmful physiological effect. Therefore, the measurer can determine that the current flowing through the human body can be suppressed to 20 mA or less if the voltage measurement value of the resistor 13 of 500Ω is 10 V or less, and the generated voltage of the solar panel may cause an electric shock. It can be easily confirmed that the level has dropped below the allowable level.

  If the measured voltage value exceeds the allowable level, the measurer should reduce the maximum current value that the solar panel can output by applying a light-shielding agent, and then measure the voltage again. Is also possible.

  FIG. 5 is a functional block diagram of the photovoltaic power generation voltage tester according to Embodiment 1 of the present invention. The photovoltaic power generation voltage tester according to the first embodiment includes a voltage measurement circuit 21, a relay circuit 22, a display 23, and a controller 24.

  The voltage measurement circuit 21 corresponds to a circuit which outputs the voltage measurement value at a desired location measured by the voltmeter 15 described in FIG. 4 to the controller 24. The relay circuit 22 is a relay circuit including the contact 14 shown in FIG. 4, and the relay coil is switched to either the excited state or the non-excited state according to an output command from the controller 24, so that the contact 14 The open / closed state can be switched.

  The display device 23 is a display device that displays a measurement result of the voltage measurement circuit 21 or a display according to a command from the controller 24. Further, the controller 24 performs overall control of the voltage measuring circuit 21, the relay circuit 22, and the display 23.

  FIG. 6 is a flowchart relating to a photovoltaic panel generated voltage measurement process executed by the controller 24 in the photovoltaic voltage tester according to the first embodiment of the present invention. First, in step S601, the measurer sets the terminals 11 and 12 to the measurement site (electric wire through which a direct current flows), and then in step S602, the controller 24 starts voltage measurement based on the operation of the measurer. To do so, the relay circuit 22 is controlled to switch the contact 14 to the closed state.

Next, in step S603, the controller 24 reads the voltage value Va measured by the voltmeter 15. Then, in step S604, the controller 24 compares the measured voltage value Va with the first allowable value Vth1 (corresponding to the first threshold value). Here, the first permissible value Vth1 corresponds to a preset voltage value because the electric power consumed by the resistor 13 of 500Ω is within the permissible heat generation value, and in the first embodiment, as an example,
Vth1 = 30 (V)
And

Then, the controller 24
Va ≦ Vth1 (1)
If is not satisfied, it is determined that if the contact 14 is continuously turned on as it is, the heat generation of the resistor 13 exceeds the allowable value, and the process proceeds to step S605. Then, in step S605, the controller 24 switches the contact 14 to the OFF state. Further, in step S606, the controller 24 determines that the measured voltage value Va is at a level that affects the human body, displays a warning message on the display 23 as necessary, and ends the series of processes.

On the other hand, if it is determined in the previous step S604 that the relationship of the above equation (1) is established, the process proceeds to step S607, where the controller 24
Va ≦ Vth2 (2)
It is determined whether or not is satisfied. Here, the second allowable value Vth2 (corresponding to a second threshold value) is a resistance 13 of 500Ω and corresponds to a voltage value set in advance to keep the current within 20 mA that does not affect the human body. In the first form, as an example,
Vth2 = 10 (V)
And

  The second permissible value Vth2 may be equal to or lower than the permissible voltage at which there is no risk of electric shock even with the minimum electric resistance of the human body.

  Then, when the above equation (2) is not established, the process proceeds to step S606, where the controller 24 determines that the measured voltage value Va is at a level that affects the human body, and warns the display device 23 as necessary. A message is displayed and the series of processing ends. Note that the controller 24 can display different messages as warning messages depending on whether Va exceeds Vth1 or when Va is below Vth1 but exceeds Vth2.

  Further, the controller 24 can also display a message urging to further apply the light shielding agent as the warning message.

  On the other hand, when the controller 24 determines in the previous step S607 that the relationship of the above equation (2) is established, the controller 24 proceeds to step S608 and determines that the measured voltage value Va is at a level that does not affect the human body, If necessary, a message indicating that it is safe is displayed on the display unit 23, and the series of processing is terminated.

  Although not shown in the flowchart of FIG. 6, the controller 24 can also periodically repeat the opening / closing control of the contact 14 according to the magnitude of the measured voltage value Va by the following method.

(Procedure 1) When the contact 14 is periodically switched between the open state and the closed state, the ratio of the closed state period within one cycle and the measured voltage value Va are set so that the heat generation amount of the resistor 13 falls within the allowable heat generation amount. A table that defines the correspondence relationship with is stored in advance.
(Procedure 2) The controller 24 extracts the ratio according to the magnitude of the measured voltage value Va from the table, and controls the opening / closing of the relay circuit 22 so as to periodically switch the contacts 14 according to the extracted ratio.

  By performing such periodical control, the measured voltage value Va can be continuously measured regardless of its magnitude, and the measurer can accurately grasp the generated voltage of the solar panel. it can.

  As described above, according to the first embodiment, it is determined whether or not the generated voltage of the solar panel is reduced to an acceptable level for electric shock of the human body by using the resistance of 500Ω in consideration of the electric resistance of the human body. Therefore, it is equipped with a configuration that enables accurate quantitative evaluation. As a result, it is possible to avoid the risk of electric shock to surrounding people due to water discharge during fire extinguishing of the solar panel, by a simple measurement operation on site.

  1 solar panel, 2 connection box, 3 power conditioner, 4 distribution board, 5 power selling meter, 11, 12 terminals, 13 resistance, 14 contacts, 15 voltmeter, 21 voltage measuring circuit, 22 relay circuit, 23 display Vessel, 24 controller.

Claims (4)

A solar power generation voltage tester that measures that the DC voltage from the solar panel is below the allowable voltage that does not cause electric shock.
A resistor having a resistance value equivalent to the electric resistance of the human body,
A relay circuit having a contact connected in series with the resistor and capable of controlling switching between an open state and a closed state,
A voltmeter that measures the voltage across the series circuit consisting of the resistor and the contacts,
When measuring the both-end voltage, the relay circuit is controlled so as to switch the contact to a closed state, and the both-end voltage measured by the voltmeter is defined by the allowable heat generation amount of the resistor. And a controller that controls the relay circuit so as to switch the contact to an open state when the threshold voltage of 1 is exceeded ,
The controller displays differently depending on whether the voltage across the voltage measured by the voltmeter is equal to or lower than a second threshold voltage defined by the allowable voltage or exceeds the second threshold voltage. Photovoltaic voltage tester to control the display like . The controller cyclically switches between the open state and the closed state of the contact, and changes the ratio of the closed state period within one cycle according to the magnitude of the voltage across the terminal measured by the voltmeter. The photovoltaic power generation voltage tester according to claim 1, wherein the photovoltaic power generation voltage tester is set and the opening / closing control of the relay circuit is performed so that the heat generation amount of the resistor is within the allowable heat generation amount. The resistor, solar power voltage tester according to claim 1 or 2 having the following resistance 500 [Omega. A method for measuring the generated voltage of a solar panel, which is executed by a controller included in a solar power generation voltage tester that measures that the DC voltage of the solar panel is equal to or lower than an allowable voltage that does not cause electric shock,
When measuring the voltage across a series circuit consisting of a resistor having a resistance value equivalent to the electrical resistance of the human body and a contact that can control switching between open and closed states,
By switching the contact to a closed state, a voltage measuring step of measuring the voltage across the end,
Correspondence between the voltage between both ends and the ratio of the period of the closed state within one cycle so that the heat generation amount of the resistor falls within the allowable heat generation amount when the contact state is periodically switched between the open state and the closed state. A storage step of pre-storing a table defining relationships,
Periodic control for repeatedly measuring the both-end voltage by extracting the ratio according to the magnitude of the both-end voltage measured in the voltage measurement step from the table and periodically switching the contact according to the extracted ratio. Steps ,
Displayed so as to display differently depending on whether the both-end voltage measured in the voltage measuring step is equal to or lower than a second threshold voltage defined from the allowable voltage or exceeds the second threshold voltage. generated voltage measuring method of a solar panel and a display step of controlling the vessel.

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