JP2017184356A - Photographic power generation voltage tester and method for measuring solar panel power generation voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the field tester to easily detect whether or not a solar panel power generation voltage is reduced to an acceptable level with respect to electric shock to a human body.SOLUTION: A photographic power generation voltage tester includes: a resistor (13) having a resistance value corresponding to electric resistance to a human body; a relay circuit having a contact point (14) serially connected to a resistor and capable of performing switching control between an open state and a closed state; a voltmeter (15) for measuring voltages at both ends of a series circuit consisting of the register and the contact point; and a controller (24) which, when the voltages at both ends are measured, switches the contact point to the closed state and, when the voltages at both ends measured by the voltmeter exceed a threshold voltage stipulated from a permissible calorific value of the resistor, controls the relay circuit so as to switch the contact point to the open state.SELECTED DRAWING: Figure 4

Description

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

  In a general solar power generation system for residential use, a solar cell array (hereinafter referred to as a solar panel) consisting of solar cell modules connected in series and parallel is installed on the roof of a house. Has been. And the output from a solar panel is connected to the power conditioner via the connection box, and it is comprised so that desired electric power can be obtained (for example, refer patent document 1).

JP 2013-110290 A Japanese Patent Laying-Open No. 2015-014709 Japanese Patent Application No. 2015-131943

National Institute of Occupational Safety and Health, Safety Materials, JNIOSH-SD-No. 25 (2009), "Electric shock basics and statistics of death accidents over the past 30 years"

However, the prior art has the following problems.
Such a solar power generation system is said to be maintenance-free, and is spreading. On the other hand, with the increase in the number of popularized units, there has been an increase in fires caused by the photovoltaic power generation system (for example, abnormal heat generation and fire due to product defects, aging deterioration, construction defects, etc. of solar cell modules constituting solar panels). It is a problem.

  Even if the solar cell module is deficient, the solar power generation system generates power when the sun comes out, and voltage and current of several hundred volts and several tens of amperes are generated. Therefore, since power is always generated when the solar panel is irradiated with light, 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 impaired due to fire burning in a state where power generation continues, there is a risk that surrounding people may be electrocuted by water discharge during fire extinguishing activities. That is, in the event of a fire in the installation environment of the solar power generation system, there is a problem that power generation of the solar panel must first be stopped.

  In response to 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, see Patent Document 2). This patent document 2 irradiates a sunscreen having thixotropy to a solar panel which is a target surface in a liquefied state due to a decrease in viscosity, and the target is a light-blocking agent that has changed into a solid state due to an increase in viscosity. By covering the object surface, light incident on the target surface is quickly blocked.

  However, in order to eliminate the risk of electric shock to surrounding people due to water discharge during fire extinguishing activities, the power generation voltage of the solar panel has further decreased to an allowable voltage level that does not cause electric shock. In an installation environment, it is important to detect reliably and simply.

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

  The photovoltaic power generation voltage tester according to the present invention is a photovoltaic power generation voltage tester for measuring that the DC voltage by the photovoltaic panel is equal to or lower than an allowable voltage with no risk of electric shock, and corresponds to the electrical resistance of the human body. Measures both-end voltage of a series circuit consisting of a resistor and a contact, and a relay circuit that has a contact connected in series with the resistor and can be switched between an open state and a closed state. When measuring the voltage at both ends and the voltage at both ends, the relay circuit is controlled so as to switch the contact to the closed state, and the voltage at both ends measured by the voltmeter is defined by the allowable heat generation amount of the resistor. And a controller that controls the relay circuit to switch the contact to the open state.

  Moreover, the method for measuring the generated voltage of the solar panel according to the present invention is based on a controller included in the solar generated voltage tester that measures that the DC voltage by the solar panel is equal to or lower than an allowable voltage with no risk of electric shock. A method for measuring a generated voltage of a solar panel to be executed, and a voltage across a series circuit including a resistor having a resistance value corresponding to an electric resistance of a human body and a contact capable of switching control between an open state and a closed state When measuring the voltage, the resistor heating value is changed to the allowable heating value when the voltage measurement step for measuring the voltage at both ends and the contact open / closed state are switched periodically by switching the contact to the closed state. Measured by the voltage measurement step and the voltage measurement step for storing a table that defines the correspondence between the ratio of the closed state within one cycle and the voltage between both ends so as to fit The extracts ratio according to the magnitude of the voltage across the table, by switching the contacts periodically by extracted ratio, and has a period control step of measuring the repeated voltage across.

  According to the present invention, it is possible to quickly measure the power generation voltage of the solar panel in consideration of the resistance value of the human body. As a result, it is possible to easily detect whether or not the generated voltage of the solar panel is lowered to an acceptable level for electric shock of the human body, and the generated voltage measurement of the solar panel and the solar panel. You can get the method.

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 the 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 in 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 photovoltaic 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. It is a flowchart regarding the power generation voltage measurement process of the solar panel performed by the controller in the solar power generation voltage tester in Embodiment 1 of this invention.

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

Embodiment 1 FIG.
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 includes a solar panel 1, a connection box 2, a power conditioner 3, a distribution board 4, and a power sale 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 input electric wires L1 and output the generated power to the connection box 2.

  The junction box 2 collects 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 connection box 2 collects power from each solar panel 1. Furthermore, the connection box 2 is connected to the power conditioner 3 via the output wire L <b> 2, 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. Furthermore, the power conditioner 3 has a function of stably outputting electric power corresponding to the amount of power generated by the solar panel 1 that 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 in the home. In the photovoltaic power generation system in which a power trading system 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, the power is sent to the power company via the power sale meter 5.

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

In FIG. 2, the influence degree of the electric shock on the human body is divided into four categories from DC-1 to DC-4, and DC-4 is further subdivided into three. Means the contents of
DC-1: Areas that are usually unresponsive and have slight stinging pain DC-2: Areas that usually do not have harmful physiological effects DC-3: Possible recovery and disturbance of the heart DC-4: Dangerous pathophysiological symptoms, such as severe burns, etc. DC-4-1: Ventricular fibrillation probability is about 5% or less DC-4-2: Region where the probability of ventricular fibrillation is about 50% or less DC-4-3: Region where the probability of ventricular fibrillation is about 50% or more

  From FIG. 2, it can be seen that if the current flowing through the human body is 20 mA or less, it is included in a region where DC-2 normally has no harmful physiological effects. On the other hand, the electrical resistance of the human body varies depending on the dry state of the skin and the magnitude of the voltage (contact voltage) when in contact with the charged part. And when skin is dry, since there exists skin resistance, the electrical resistance of the human body becomes several kΩ or more. On the other hand, when the skin is completely wet due to sweating or the like, the electrical resistance of the skin approaches 0Ω as much as possible.

  As a result, although the electric resistance of the human body varies depending on the energization path, it is considered that the internal resistance alone is about 500Ω, considering the worst case. For example, assuming that a 500 Ω human body is in contact with a 200 VDC charging part, a current of 400 mA flows through the body.

  As a result, it is difficult to get away from the live part due to muscle contraction, etc., and if current flows for more than 0.5 seconds, it may cause ventricular fibrillation and death. Considering this, it can be understood that the voltage of DC 200 V is a dangerous voltage for the human body.

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

  Next, the effect when the above-described light shielding agent of Patent Document 2 is applied to the 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 at a load of 500Ω due to a difference in the short-circuit current of the solar panel in the first embodiment of the present invention.

  The solar panel 1 in this Embodiment 1 shall have the performance which can be sent to 10A at the time of a rated output. The maximum value of the open circuit voltage at the rated output is about 250 V at DC. 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 1/50 shading, although the current is suppressed to 0.2 A, which is 1/50 of the rated output, the open-circuit voltage hardly decreases. However, since the current is suppressed to 0.2 A at the time of 1/50 light shielding, a current of 0.2 A flows and a voltage of 100 V is applied to a 500Ω load.

  Moreover, in 1/500 light shielding, although an electric current is suppressed to 0.02 A which is 1/500 of a rated output, the open circuit voltage hardly falls. However, since the current is suppressed to 0.02 A at the time of 1/500 light shielding, a current of 0.02 A flows and a voltage of 10 V is applied to a 500Ω load.

Therefore, at the rated output, 1/50 light shielding, and 1/500 light shielding shown in FIG.
・ At rated output: 0.49A × 245V = 120W
-1/50 shading: 0.2 A x 100 V = 20 W
・ At 1/500 shading: 0.02A × 10V = 2W

  Here, heat generation when a resistance of 500Ω is incorporated in the tester is considered. At the rated output, a power of 120 W is consumed with a resistance of 500Ω, and the resistance becomes very high. On the other hand, when the light is shielded by 1/50 and when light is shielded by 1/500, the power consumption can be suppressed by 20 W and 2 W, respectively. As a result, it is possible to adopt a small resistor in consideration of power consumption.

  FIG. 4 is an explanatory diagram showing a voltage measurement circuit 21 described later of the photovoltaic power generation voltage tester according to Embodiment 1 of the present invention. The voltage measurement circuit shown in FIG. 4 includes terminals 11 and 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 at both ends thereof is measured with a voltmeter 15. Here, the contact 14 in FIG. 4 is described as a normally open contact, but a normally closed contact may be employed depending on the circuit configuration.

  Although not described in detail, the applicant of the present application can insert the needle-like measurement terminal into the coating of the electric wire (for example, the output electric wire L2) that transmits the DC power generated by the solar panel. A voltage measuring device that allows an operator to measure the voltage of an electric wire by a simple operation on site has already been filed as Patent Document 3, and this technique is applied to the terminals 11 and 12. It can be used for.

  The resistor 13 is a small 500 Ω resistor that assumes the minimum value of the electrical resistance of the human body. The contact 14 is a relay contact included in the relay circuit 22 of FIG. 5 to be described later, and is a relay contact that is opened when the coil of the relay circuit 22 is de-energized and is closed when the coil is excited. is there.

  As described above, the power consumed by the resistor 13 varies depending on the light shielding state of the solar panel, and if the light shielding is not sufficient, there is a possibility that the heat generation exceeds 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 perform voltage measurement, and when the voltage measurement value exceeds a preset allowable value, in order to prevent the resistor 13 from generating heat, the contact 14 Open / close control is performed to switch to the open state.

If the allowable value for judging the switching to the open state is DC 30 V, a current of 60 mA flows through the 500Ω resistor.
30V × 0.06A = 1.8W
It is possible to employ a small resistor that can consume the maximum power specified in (1).

  In addition, when measuring a voltage higher than the allowable value, the ON / OFF state of the relay is periodically switched, the period in which the contact 14 is not turned on, that is, the period in which heat generation is suppressed without flowing current through the resistor 13, It is possible to measure a voltage exceeding 30 V using a small resistor of 1.8 W.

  The voltmeter 15 can measure the voltage applied to the resistor 13 when the contact 14 is closed. As described above with reference to FIG. 2, 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 fallen below the allowable level.

  In addition, if the measured voltage value exceeds the allowable level, the measurer should measure the voltage again after lowering the maximum current value that the solar panel can output by further applying a light shielding agent. 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 that outputs a 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 an excited state or a non-excited state in accordance with an output command from the controller 24. The open / close state is switched.

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

  FIG. 6 is a flowchart relating to the solar panel power generation voltage measurement process executed by the controller 24 in the solar power generation voltage tester according to the first embodiment of the present invention. First, in step S601, after the terminals 11 and 12 are set at the measurement location (the electric wire through which the direct current flows) by the measurer, in step S602, the controller 24 starts voltage measurement based on the operation of the measurer. For this purpose, the relay circuit 22 is controlled to switch the contact 14 to the closed state.

Next, in step S <b> 603, the controller 24 reads the measured voltage value Va from the voltmeter 15. 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 allowable value Vth1 corresponds to a preset voltage value because the power consumed by the resistor 13 of 500Ω is within the allowable heat generation value. In the first embodiment, as an example,
Vth1 = 30 (V)
And

Then, the controller 24
Va ≦ Vth1 (1)
If not, if the contact 14 is kept on as it is, it is determined that the heat generation of the resistor 13 exceeds the allowable value, and the process proceeds to step S605. In step S605, the controller 24 switches the contact 14 to the OFF state. Furthermore, 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 unit 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)
Whether or not is satisfied is determined. Here, the second allowable value Vth2 (corresponding to the second threshold value) corresponds to a voltage value set in advance so that the current is within 20 mA that does not affect the human body with the resistor 13 of 500Ω. In form 1, as an example,
Vth2 = 10 (V)
And

  Note that the second allowable value Vth2 only needs to be equal to or lower than an allowable voltage at which there is no risk of electric shock even with the minimum electrical resistance of the human body.

  If the above equation (2) does not hold, 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 if necessary. A message is displayed and a series of processing is terminated. Note that the controller 24 can also display different messages as warning messages when Va is determined to exceed Vth1 and when Va is determined to exceed Vth1 but exceed Vth2.

  The controller 24 can also display a message prompting further application of the light shielding agent as this warning message.

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

  Although omitted from the flowchart of FIG. 6, the controller 24 can periodically repeat the switching 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 period of the closed state within one cycle and the measured voltage value Va so that the heat generation amount of the resistor 13 falls within the allowable heat generation amount. Is stored in advance.
(Procedure 2) The controller 24 extracts a ratio according to the magnitude of the measured voltage value Va from the table, and controls the opening and closing of the relay circuit 22 so as to periodically switch the contact 14 according to the extracted ratio.

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

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

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

Claims (5)

A photovoltaic power generation voltage tester that measures that the DC voltage from the solar panel is below an allowable voltage that does not cause an electric shock,
A resistor having a resistance value corresponding to the electrical resistance of the human body;
A relay circuit having a contact connected in series with the resistor and capable of switching control between an open state and a closed state;
A voltmeter for measuring a voltage across a series circuit composed of the resistor and the contact;
When measuring the voltage across the terminal, the relay circuit is controlled to switch the contact to the closed state, and the voltage across the terminal measured by the voltmeter is defined by the allowable heat generation amount of the resistor. And a controller that controls the relay circuit to switch the contact to an open state when the threshold voltage of 1 is exceeded. A photovoltaic power generation voltage tester that measures that the DC voltage from the solar panel is below an allowable voltage that does not cause an electric shock,
A resistor having a resistance value corresponding to the electrical resistance of the human body;
A voltmeter for measuring a voltage across a series circuit composed of the resistor and the contact;
Indicator that displays differently depending on whether the both-ends voltage measured by the voltmeter is equal to or lower than a second threshold voltage defined from the allowable voltage and when the voltage exceeds the second threshold voltage. A photovoltaic voltage tester comprising a controller for controlling The controller periodically switches between the open state and the closed state of the contact, and varies the ratio of the period of the closed state within one cycle according to the magnitude of the both-end voltage measured by the voltmeter. 2. The photovoltaic power generation voltage tester according to claim 1, wherein the switching control of the relay circuit is performed so that the heating value of the resistor falls within the allowable heating value. The photovoltaic power tester according to any one of claims 1 to 3, wherein the resistor has a resistance value of 500Ω or less. A solar panel power generation voltage measurement method executed by a controller included in a solar power generation voltage tester for measuring that a DC voltage by a solar panel is equal to or less than an allowable voltage with no risk of electric shock,
When measuring the voltage across a series circuit consisting of a resistor having a resistance value corresponding to the electrical resistance of the human body and a contact capable of switching control between an open state and a closed state,
By switching the contact to the closed state, a voltage measuring step for measuring the both-end voltage,
Correspondence between the ratio of the period of the closed state within one cycle and the voltage between both ends so that the heat generation amount of the resistor falls within the allowable heat generation amount when periodically switching between the open state and the closed state of the contact A storage step for storing a table defining the relationship in advance;
Periodic control for repeatedly measuring the voltage at both ends by extracting the ratio according to the magnitude of the voltage at both ends measured in the voltage measuring step from the table and periodically switching the contact point according to the extracted ratio. A method for measuring a generated voltage of a solar panel, comprising:

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