JP2017106760A - Method of displaying insulation resistance and insulation resistance meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation resistance meter capable of properly measuring and displaying an insulation resistance value of an object under measurement at appropriate timing.SOLUTION: A method of displaying insulation resistance includes; connecting an insulation resistance meter 1 between a first output terminal 21 and a ground terminal 23 of a solar power generation unit 10 (connection box 20); having current measurement means 6 take two or more measurements of current A1 that flows in a test-voltage-not-applied state, in which a test voltage V is not applied, to derive a current variation rate (ΔI/Δt); storing measurement data D8 acquired when the current variation rate becomes reference current variation rate data D4 or less as previous measurement data D6 in nonvolatile storage means 4; deriving a resistance value from the test voltage V and a test current difference value obtained by subtracting the current value of the previous measurement data D6 from current A1 that flows in a subsequent test-voltage-applied state, in which the test voltage V from power feeding means 7 is applied; and having display means 3 display an insulation resistance value obtained by subtracting a value of an overcurrent protection resistor 5 from the derived resistance, and elapsed time from the start of the measurement.SELECTED DRAWING: Figure 1

Description

  The present invention provides an insulation resistance display method suitable for measuring insulation resistance using a photovoltaic power generation unit or the like disposed in a photovoltaic power generation facility as a measurement object, and the insulation resistance display method. It relates to the applied insulation resistance meter.

  In conventional photovoltaic power generation equipment, periodic insulation resistance measurement is performed for maintenance and management. Insulation resistance value is measured by short-circuiting the positive and negative terminals of the photovoltaic power generation unit and insulating while applying an inspection voltage with an insulation resistance meter connected between both output terminals and the grounded part. A method for measuring a resistance value is widely known. However, during the daytime when sunlight is radiated to the solar cell module, there is a potential difference of several hundred volts between the output terminals of the photovoltaic power generation unit. In such a state, the output terminals are short-circuited. Not only is it very dangerous to do so, but it can lead to damage to the insulation resistance meter.

  In order to avoid such dangers, the photoelectric conversion function is suppressed by shielding the light receiving surface of the solar cell module with a black sheet or the like, or measurement work at night when the sun sets and power generation is not performed in the solar cell module However, the work of shading the solar cell module is complicated, and the measurement work at night with poor visibility is dangerous. Therefore, in order to enable safe measurement of insulation resistance even when the solar cell module is generating power, with the positive and negative terminals of the photovoltaic power unit open, there is an excess between one of the terminals and the grounding part. There has been proposed a method in which an insulation resistance meter having a built-in current protection resistor is connected, and an insulation test is performed while a test voltage is applied between one terminal and a grounded part (see, for example, Patent Document 1).

  According to the insulation inspection method described in Patent Document 1, the current flowing between the output terminal and the grounding part in the state where the inspection voltage is applied between the one output terminal and the grounding part in the photovoltaic power generation unit The current flowing between the output terminal and the grounded part in the state where the application of the test voltage is stopped next is set as the second current value, and the second current value is subtracted from the first current value. The insulation resistance value between the output terminal and the grounding part is obtained by calculation based on the current value and the voltage value of the inspection voltage. The obtained insulation resistance value is smaller than the normal insulation resistance value. If so, it can be determined that an insulation failure has occurred.

Japanese Patent No. 5614410

  However, in the invention described in Patent Document 1, since the influence of a large ground capacitance existing in parallel with the insulation resistance is not considered between the photovoltaic power generation unit and the grounding part, the insulation obtained by calculation is not considered. There may be a considerable amount of error in the resistance value. This is due to the structure and installation method of the photovoltaic power generation unit.

  In general, a solar cell constituting a photovoltaic module is formed by sandwiching a silicon cell arranged in a plane with an ethylene vinyl acetate sealing material, insulating the front side with glass, and making the back side made of resin. The insulation structure (back sheet) is used to insulate the silicon cell, the back sheet, and the ground connecting the grounding part, and an electric double layer is formed. It becomes equal to the state where it is connected to the grounding part with a large ground capacitance in parallel with the ground. Therefore, when the current value is measured by connecting one output terminal of the photovoltaic power generation unit to the grounded portion, charging / discharging of the ground capacitance has a considerable influence on the measured value.

  That is, when the insulation resistance is measured by the inventive method described in Patent Document 1, the first current value and the second current value are measured in a state where the current flowing through the insulation resistance and the ground charging current are flowing simultaneously. Therefore, a current value larger than the current flowing only in the insulation resistance, which is the current flowing between the output terminal that should be the target of calculation and the ground portion, is measured as the first current value and the second current value. It will be done. For this reason, the insulation resistance value between the output terminal and the ground portion calculated based on the current value obtained by subtracting the second current value from the first current value and the voltage value of the inspection voltage is the actual photovoltaic power generation. It becomes a value lower than the insulation resistance value of the unit. As a result, even if the insulation resistance of the actual photovoltaic power generation unit is good, the insulation resistance value obtained by calculation may be lower than the normal range. There is a risk of misjudging the insulation state between the two as defective.

  Due to the influence of the capacitance to the ground, even if the ground resistance is measured by the inventive method described in Patent Document 1, the insulation resistance value will fluctuate for a while. It is dangerous to use the displayed value for equipment inspection, and some device is required to use it for inspection work of solar power generation equipment. For example, while repeatedly measuring the insulation resistance value and separately measuring the elapsed time from the start of measurement with a clock or the like, at a predetermined time such as 1 minute (necessary and sufficient time that the ground capacitance is considered saturated) When this is reached, the insulation resistance value displayed on the insulation resistance meter is recorded. However, it is very complicated to perform the measurement work while measuring the elapsed time from the start of measurement with a separately prepared watch, stopwatch, or the like in a periodic inspection performed on a daily basis.

  Moreover, when measuring the insulation resistance of a photovoltaic power generation unit by the invention method described in Patent Document 1, first, the second current value is measured in a state where the application of the inspection voltage is stopped, and then the inspection If the first current value is repeatedly measured in a state where a voltage is applied, the ground capacitance reaches saturation with time, and the first current value is obtained as an appropriate value. When the necessary and sufficient time elapses, the illusion may be that the insulation resistance value obtained by the calculation becomes an appropriate value.

  However, the second current value used for the calculation of the insulation resistance is a value measured at the beginning of measurement that is affected by the capacitance to the ground, and is not updated thereafter. Therefore, the invention described in Patent Document 1 In the method, since the second current value is a high value including the ground charging current, the insulation resistance value obtained by the calculation is always lower than the original insulation resistance value. As a result, even if the insulation resistance of the actual photovoltaic power generation unit is good, the insulation resistance value obtained by calculation may be lower than the normal range. There is a risk of misjudging the insulation state between the two as defective.

  Then, this invention aims at provision of the insulation resistance display method and insulation resistance meter which can measure and display the insulation resistance value of a measuring object appropriately at an appropriate timing.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to an elapsed time measuring step for measuring the passage of time with reference to the start of the measurement process of insulation resistance, and a pair of outputs in a measuring object having an electromotive force. One of the terminals is a terminal to be measured, and the current flowing between the terminal to be measured and the ground part is measured at a required interval in a state in which no test voltage is applied between the terminal to be measured and the ground part. The current change rate (ΔI), which is a difference between two current values obtained by two or more measurements and the elapsed time (Δt) that is an interval between the two measurements, is measured. ΔI / Δt) for obtaining a current change rate, a saturation achievement condition determining step for judging whether the current change rate obtained in the current change rate obtaining step satisfies a predetermined saturation achievement condition, and the saturation Saturation reached in achievement condition judgment process A test current non-application measurement current acquisition step in which the current flowing between the terminal to be measured and the grounding part when the condition is determined is a measurement current when the test voltage is not applied, and the measurement current when the test voltage is not applied After performing the acquisition process, in the test voltage application state in which the test voltage is applied between the terminal to be measured and the ground part, the measurement current at the time of applying the test voltage flowing between the terminal to be measured and the ground part is obtained. The measurement current acquisition process when applying the test voltage, and the measurement current acquisition process when applying the test voltage in the measurement current acquisition process when applying the test voltage and the measurement current acquisition process when the test voltage is applied. An insulation resistance value between the terminal to be measured and the grounding part is obtained based on the difference current value for inspection obtained by subtracting the measurement current value when the inspection voltage is not applied from the value and the voltage value for inspection. Insulation resistance value and the elapsed time measurement And an insulation resistance display step of simultaneously displaying the elapsed time since the start of timing.

  According to a second aspect of the present invention, in the insulation resistance display method according to the first aspect, in the insulation resistance display step, from the time when the voltage for inspection is applied between the terminal to be measured and a grounded part. The elapsed time is simultaneously displayed.

  Further, the invention according to claim 3 is the insulation resistance display method according to claim 1 or claim 2, wherein in the insulation resistance display step, the inspection first acquired in the measurement current acquisition step when the inspection voltage is applied. The elapsed time from the time when the insulation resistance value obtained based on the measured current at the time of voltage application is displayed is displayed at the same time.

  According to a fourth aspect of the present invention, in the insulation resistance display method according to any one of the first to third aspects, an overcurrent protection resistor is provided between the terminal to be measured and a grounding part. In the state, the current change rate acquisition step, the measurement current acquisition step when the test voltage is not applied, and the measurement current acquisition step when the test voltage is applied are performed. In the insulation resistance display step, an insulation resistance value is calculated. The resistance value corrected by subtracting the overcurrent protection resistance value from the result is displayed as an insulation resistance value.

  In order to solve the above-mentioned problem, the invention according to claim 5 is a pair of a time measuring means capable of measuring the passage of time with reference to the start of the measurement process of insulation resistance, and a pair of measuring objects having electromotive force. One of the output terminals is a measured terminal, a power supply means that can apply a test voltage between the measured terminal and the ground part, and a current that can measure a current flowing between the measured terminal and the ground part An inspection voltage application state in which an inspection voltage is applied between the terminal to be measured and the grounded part by the measuring means and the power feeding means, and an inspection in which no inspection voltage is applied between the terminal to be measured and the grounded part The voltage is not applied, and the insulation resistance value is obtained using the measured current value measured by the current measuring means, and the elapsed time from any reference time using the time measured by the time measuring means. Ask for Measurement control means, and at least display means capable of simultaneously displaying the insulation resistance value obtained by the measurement control means and the elapsed time, and the measurement control means includes the terminal to be measured and the grounding part. In a state in which no inspection voltage is applied between them, the current flowing between the terminal to be measured and the grounded part is measured twice or more at a required interval by the current measuring means, and two consecutive measurements are made. The current change rate (ΔI / Δt) is obtained from the difference current value (ΔI) that is the difference between the two current values obtained in step 2 and the elapsed time (Δt) that is the measurement interval between the two times, and the current change rate is The current flowing between the terminal to be measured and the grounding part when the predetermined saturation achievement condition is satisfied is stored as the measurement current when the test voltage is not applied, and then the test is performed between the terminal to be measured and the grounding part. Voltage mark for inspection with voltage applied Each time the measurement current when the test voltage applied between the terminal to be measured and the grounded part is applied is repeatedly measured by the current measuring means at a required interval. Based on the difference current value for inspection obtained by subtracting the current value measured when no voltage for inspection is applied from the current value measured when voltage for inspection is applied and the voltage value for inspection between the terminal to be measured and the grounded part. An insulation resistance value is obtained, and this insulation resistance value and an elapsed time from the start of the measurement process are simultaneously displayed on the display means.

  The invention according to claim 6 is the insulation resistance meter according to claim 5, wherein the measurement control means applies the test voltage between the terminal to be measured and a grounded portion by the power feeding means. The elapsed time from the time point is simultaneously displayed on the display means.

  The invention according to claim 7 is the insulation resistance meter according to claim 5 or claim 6, wherein the measurement control means obtains the insulation resistance obtained based on the first measured current value obtained when the test voltage is applied. The elapsed time from the time when the value is displayed on the display means is simultaneously displayed on the display means.

  Further, the invention according to claim 8 is the insulation resistance meter according to any one of claims 5 to 7, wherein an overcurrent protection resistor is connected between the terminal to be measured and a grounded part, The measurement control means displays the resistance value corrected by subtracting the overcurrent protection resistance value from the calculation result of the insulation resistance value, on the display means as the insulation resistance value.

  According to the insulation resistance display method and the insulation resistance meter according to the present invention, even if the measurement object having an electromotive force has a large ground capacitance in parallel with the insulation resistance, the influence of the ground capacitance Appropriate insulation resistance can be measured and displayed together with the time from the start of measurement at an appropriate timing. Therefore, it is possible to efficiently and accurately perform the insulation resistance measurement work in the periodic inspection or the like.

It is a schematic block diagram which shows the case where the insulation resistance of a photovoltaic power generation unit is measured with the insulation resistance meter to which the insulation resistance display method which concerns on this invention is applied.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an insulation resistance meter to which an insulation resistance display method according to the present invention is applied will be described in detail with reference to the accompanying drawings.

  The insulation resistance meter 1 shown in FIG. 1 measures the insulation resistance Rg using the photovoltaic power generation unit 10 of the photovoltaic power generation facility as a “measurement object having an electromotive force”, and displays the insulation resistance value and the measurement elapsed time. To do.

  The solar power generation unit 10 is an aggregate in which several to several tens of solar cell modules are connected in series, and is installed on the ground in a state of being fixed to a concrete or aluminum frame. The solar power generation unit 10 is generally connected by wiring via a connection box 20, and the connection box 20 includes a first output terminal 21 and a second output terminal 22 as a pair of output terminals, and grounding. A ground terminal 23 is provided as a grounded portion. Note that, in the photovoltaic power generation unit 10 shown in the figure, when the solar light is radiated to generate power, the plus-side wiring is the first output terminal 21 and the minus-side wiring is the second output terminal 22. The open circuit voltage values of the first output terminal 21 and the second output terminal 22 that are connected to each other are about 600V, for example.

  The insulation resistance meter 1 connected to the photovoltaic power generation unit 10 through the connection box 20 includes a real time clock 2, a display means 3, a nonvolatile storage means 4, an overcurrent protection resistor 5, a current measurement means 6, and a power supply means 7. Measurement control means 8 and connection terminals 9a and 9b.

  The real time clock 2 measures the real time, and always outputs time data D1 to the measurement control means 8. The measurement control means that has received the time data D1 can grasp the elapsed time based on an arbitrary timing such as the measurement start time. In other words, the real-time clock 2 and the measurement control unit 8 cooperate to function as “a time measuring unit that can measure the passage of time based on at least the start of the insulation resistance measurement process”. Note that a timer circuit or the like that starts measuring time at an arbitrary timing may be used as the time measuring means, and the elapsed time may be provided to the measurement control means 8.

  The display means 3 has at least a function of simultaneously displaying the insulation resistance value data D2 and the elapsed time data D3 output from the measurement control means 8. For example, the insulation resistance value can be visually displayed on a pointer-type analog display, and the elapsed time can be visually displayed by the number of lighting of a plurality of LEDs (for example, one LED lights up after 1 minute has passed). In addition, a segment type display or a matrix display in which LEDs are arranged in a matrix may be used, or a high-definition liquid crystal display having a high degree of freedom in display may be used. In addition, you may make it perform auditory alert | reporting together, such as sounding a buzzer sound at the predetermined timing (for example, 1 minute progress time) with progress of time.

  The non-volatile storage means 4 is, for example, a non-volatile memory that stores reference current change rate data D4 set in advance and does not lose the stored contents even after the power is turned off. The nonvolatile storage means 4 stores an operation program for the measurement control means 8, and the measurement control means 8 loads the operation program from the nonvolatile storage means 4 when the insulation resistance meter 1 is started. Thus, the measurement control means 8 can execute a predetermined measurement control function. Further, the nonvolatile storage unit 4 stores the previous measurement time data D5, the previous measurement data D6, the measurement start time data D7, and the like transmitted from the measurement control unit 8, and in response to a request from the measurement control unit 8, These stored data are transmitted to the measurement control means 8. The previous measurement time data D5, the previous measurement data D6, the measurement start time data D7, and the like are data temporarily required in the measurement process, so that they are stored and managed in the volatile memory provided in the measurement control means 8. Also good.

  The overcurrent protection resistor 5 is a protection resistor that prevents the insulation resistance meter 1 from being damaged by an overcurrent, and uses, for example, a 1 MΩ resistor.

  The current measuring means 6 is a current value of a current flowing between one of the first output terminal 21 or the second output terminal 22 of the photovoltaic power generation unit 10 and the ground terminal 23 in accordance with the control signal S2 from the measurement control means 8. A1 is measured, and the measurement result is output to the measurement control means 8 as measurement value data D8.

  In accordance with the control signal S <b> 1 from the measurement control unit 8, the power supply unit 7 applies a test voltage V (V can be set to an arbitrary value) between the first output terminal 21 or the second output terminal 22 and the ground terminal 23. Output. When the power supply means 7 does not apply the inspection voltage V, a closed circuit that short-circuits between the first output terminal 21 or the second output terminal 22 and the ground terminal 23 (shown by a broken line in the power supply means 7 in FIG. 1). Form.

  The connection terminal 9 a is a terminal for connecting to the ground terminal 23, and the connection terminal 9 b is a terminal for connecting to the first output terminal 21 or the second output terminal 22 in the photovoltaic power generation unit 10.

  The measurement control means 8 comprehensively controls the measurement of insulation resistance. Specifically, the start and stop of the output of the test voltage V is controlled by outputting the control signal S1 to the power supply means 7, and the control signal S2 is output to the current measuring means 6 to output the current value. The measurement process of A1 is started. Further, the measurement control means 8 includes time data D1 output from the real-time clock 2 and previous measurement time data D5 stored in the nonvolatile storage means 4, measurement value data D8 output from the current measurement means 6 and nonvolatile information. The current change rate is obtained based on the previous measurement data D6 stored in the storage unit 4, and it is determined whether or not it is equal to or less than the reference current change rate data D4 stored in the nonvolatile storage unit 4 (saturation achievement condition). Then, the insulation resistance value data D2 of the photovoltaic power generation unit 10 is calculated from the measured value data D8 when the saturation achievement condition is satisfied, and the time data D1 output from the real-time clock 2 and stored in the nonvolatile storage means 4 The measured elapsed time data D3 is obtained from the measured measurement start time data D7, and the insulation resistance value data D2 and the elapsed time data are obtained. 3 is displayed on the display unit 3.

  Next, measurement control and display control of the insulation resistance of the photovoltaic power generation unit 10 by the insulation resistance meter 1 will be described.

  First, the insulation ohmmeter 1 is carried in the photovoltaic power generation facility, the connection terminal 9a is connected to the ground terminal 23 of the connection box 20, and the first output terminal 21 of the photovoltaic power generation unit 10 connected to the connection box 20 ( For example, a plus terminal) is used as a terminal to be measured, and a connection terminal 9b is connected thereto. Thereby, the ground terminal 23 is connected to the power feeding means 7 via the connection terminal 9 a, and the first output terminal 21 of the photovoltaic power generation unit 10 is connected to the current measuring means 6 via the connection terminal 9 b and the overcurrent protection resistor 5. Connected.

  After the setting of the insulation resistance meter is completed as described above, a measurement start switch of an operation unit (not shown) is operated. By receiving this measurement start instruction, the measurement control means 8 obtains the insulation resistance value data D2 of the measurement object (in this example, the photovoltaic power generation unit 10) and the elapsed time data D3 from the start of the measurement process to the present. The control process to be displayed is started.

  At the start of the insulation resistance measurement process, for example, an insulation failure has occurred between the ground terminal 23 and the first output terminal 21 of the photovoltaic power generation unit 10, and insulation between the ground terminal 23 and the first output terminal 21 has occurred. When the value of the resistance Rg is smaller than the value of the normal insulation state, the potential difference (solar power generation unit) generated between the ground terminal 23 and the first output terminal 21 of the solar power generation unit 10 10 electromotive force), a large current flows between the ground terminal 23 and the first output terminal 21 from the location where the insulation is defective, and the insulation resistance meter 1 may be damaged. For this reason, in the insulation resistance meter 1, the overcurrent protection resistor 5 (1 MΩ in this example) is connected between the current measuring means 6 and the connection terminal 9 b so as to be between the ground terminal 23 and the first output terminal 21. Even if an insulation failure occurs, the situation where the insulation resistance meter 1 is damaged is avoided.

  First, the measurement control means 8 is the time data from the real-time clock 2 in a state where the application of the inspection voltage V is stopped (the inspection voltage is not applied between the terminal to be measured and the grounded portion). D1 is read and stored in the nonvolatile storage means 4 as measurement start time data D7. It is possible to perform elapsed time measurement that measures the passage of time with reference to the start of the insulation resistance measurement process.

  Along with the start of the elapsed time measurement process, the current value of the current A1 flowing between the ground terminal 23 and the first output terminal 21 is measured. In this case, even if the photovoltaic power generation unit 10 to be inspected is installed in a normally insulated state, an insulation resistance Rg having a large resistance value and a large capacity are provided between the ground terminal 23 and the first output terminal 21. A ground capacitance Cg of a value exists in parallel (indicated by a broken line in FIG. 1).

  Moreover, if sunlight is irradiated to each solar cell module of the photovoltaic power generation unit 10 and the photoelectric conversion function works normally, a direct current of about 600 V is provided between the first output terminal 21 and the second output terminal 22. A potential difference is generated, and a potential difference of about 300 V DC is generated between the ground terminal 23 and the voltage first output terminal 21. In this state, first, a combined current A2 of the current A2r flowing through the insulation resistance Rg and the ground charging current A2c flowing through the ground capacitance Cg begins to flow, but the ground charging current A2c flowing through the ground capacitance Cg Since electric current does not flow as the electric charge is accumulated in the capacitance Cg, only the current A2r that flows through the insulation resistance Rg is finally obtained.

  Therefore, the measurement control means 8 stores the time data D1 from the real-time clock 2 in the nonvolatile storage means 4 as the previous measurement time data D5, and outputs a control signal S2 to the current measurement means 6 to output the ground terminal 23. A1 flowing between the first output terminal 21 and the first output terminal 21 is measured, and the measured value data D8 output from the current measuring means 6 is stored in the nonvolatile storage means 4 as the previous measurement data D6. This series of processing is performed twice or more at a required interval (a time determined appropriately according to the change rate of the ground charging current A2c, for example, at an interval of 1 second).

  Then, two current values obtained by two consecutive measurements, that is, a difference (ΔI) between the measured value data D8 and the previous measured data D6, and an elapsed time that is an interval between the two measurements, that is, time data. The current change rate (ΔI / Δt) is obtained from the time difference (Δt) between D1 and the previous measurement time data D5, and the current change rate becomes equal to or less than the reference current change rate data D4 stored in the nonvolatile storage means 4. At the time (when the saturation achievement condition is satisfied), the measured current value of the current A1 (the measured current value when the test voltage is not applied, for example, 0.3 mA) is the ground charging current flowing through the ground capacitance Cg. The measured value data D8 of the current A2r flowing through the insulation resistance Rg excluding the influence of A2c is stored in the nonvolatile storage means 4.

  Here, the current change rate (ΔI / Δt) indicates a slope in a certain time range of an It curve in which the current A1 detected by the current measuring means 6 changes with time, and the slope is zero. This indicates that the current A1 has become a constant value. Therefore, the slope of the It curve that can be considered that the ground capacitance Cg has reached saturation is set in advance as the reference current change rate, and the current change rate obtained by the calculation is less than the reference current change rate. By making this a saturation achievement condition, it is possible to determine that the influence of the ground charging current A2c is excluded and the current A2r flowing through the insulation resistance Rg can be measured as measured value data D8. Accordingly, the measured value data D8 measured when the saturation achievement condition is satisfied is an appropriate measured current value when no test voltage is applied when the test voltage is not applied, and this is non-volatile as the measured value data D8. It is possible to obtain a highly accurate insulation resistance value by storing it in the storage means 4 and using it for the insulation resistance calculation described later.

  As described above, in a state in which no test voltage is applied between the terminal to be measured and the grounded part, the current flowing between the terminal to be measured and the grounded part is not less than twice at a required interval. The current change rate (ΔI / Δt) is calculated from the difference current value (ΔI), which is the difference between two current values obtained by two measurements, and the elapsed time (Δt), which is the interval between the two measurements. ) Current change rate acquisition step for obtaining "," a saturation achievement condition determination step for determining whether or not the current change rate obtained in the current change rate acquisition step satisfies a predetermined saturation achievement condition ", and There is a measurement current acquisition step when no test voltage is applied, where the current flowing between the terminal to be measured and the grounded part is measured when the test voltage is not applied when the saturation achievement condition is determined in the saturation achievement condition determination step. Performed by the insulation resistance meter 1.

  Next, the measurement control unit 8 outputs a control signal S1 to the power supply unit 7 to output a DC inspection voltage V (for example, 1000 V) and outputs a control signal S2 to the current measurement unit 6. Then, the current value of the current flowing between the ground terminal 23 and the first output terminal 21 (measurement current value when the test voltage is applied, for example, 1.3 mA) is measured, and the new measured value data D8 is nonvolatile. The previous measurement data D6 (measured current value when no test voltage is applied) stored in the characteristic storage means 4 is subtracted. As a result, the current value excluding the influence of the potential difference of about 300 V generated between the ground terminal 23 and the first output terminal 21 due to the power generation of the photovoltaic power generation unit 10 (inspection difference current value, for example, 1 .0 mA).

  Subsequently, the measurement control means 8 is based on the inspection differential current value obtained by the calculation and the voltage value (1000 V) of the inspection voltage V applied by the power supply means 7 when the measured value data D8 is measured. Find the resistance value. By subtracting and correcting the resistance value (1 MΩ) of the overcurrent protection resistor 5 from this resistance value, the resistance value of the insulation resistance Ra between the ground terminal 23 and the first output terminal 21 is obtained, and the insulation resistance value data It transmits to the display means 3 as D2. At the same time, the measurement control means 8 reads the current time data D1 from the real-time clock 2 and subtracts the measurement start time data D7 recorded in the nonvolatile storage means 4 from the time data D1, thereby starting from the measurement start. The elapsed time is calculated and transmitted to the display means 3 as elapsed time data D3. That is, the insulation resistance value and the elapsed time are simultaneously displayed by the display means 3 that has received the insulation resistance value data D2 and the elapsed time data D3 at the same time.

  After that, the measurement control means 8 repeatedly performs the processing from the measurement of the measurement value data D8 performed by outputting the test voltage V at the required interval (for example, every 10 seconds) until the insulation resistance value and the elapsed time are obtained. By transmitting the insulation resistance value data D2 and the elapsed time data D3 to the display means 3 while updating them, the latest resistance value and the elapsed time up to that time are displayed on the display means 3 at the same time.

  As described above, in the test voltage application state in which the test voltage is applied between the terminal to be measured and the grounded part after performing the measurement current acquisition step when the test voltage is not applied, the terminal to be measured `` Measurement current acquisition process at the time of inspection voltage application that repeatedly measures the measurement current at the time of application of the test voltage flowing between the ground and the ground part '' and `` Applying the inspection voltage in the measurement current acquisition process at the time of application of the inspection voltage '' Each time the measured current is obtained, based on the test differential current value obtained by subtracting the test current non-applied measurement current value from the test voltage applied measurement current value and the test voltage value An insulation resistance display step for obtaining an insulation resistance value between the terminal to be measured and the grounded portion and simultaneously displaying the insulation resistance value and an elapsed time after starting the time measurement in the elapsed time measurement step '' Performed by the insulation resistance meter 1.

  The measurement of the latest insulation resistance value Ra is repeatedly performed by the insulation resistance meter 1 of the present embodiment, and when the time elapsed from the start of measurement becomes longer, the measured insulation resistance value changes as the electric charge is stored in the ground capacitance Cg. Will be. And if the inspection process is set to record the insulation resistance value at a predetermined elapsed time such as 1 minute from the start of measurement, a time measuring clock or the like is not prepared separately. However, since it is possible to know the recording timing from the elapsed time displayed on the display means 3, it is possible to easily proceed with inspection work and the like that are very troublesome.

  Moreover, the measured value data D8 of the current A1 measured in a state where the application of the inspection voltage is stopped excludes the value when the saturation achievement condition is satisfied, that is, the influence of the ground charging current A2c flowing through the ground capacitance Cg. Since the measured value data D8 of the current A2r flowing through the insulation resistance Rg is constant until the display value of the insulation resistance value of the display means 3 is set to a constant value (the ground capacitance Cg is saturated by applying the inspection voltage by the power supply means 7). Until the measurement is continued, the accurate insulation resistance Ra can be displayed on the display means 3.

  Thus, whether or not breakage such as disconnection occurs in each solar battery cell constituting the photovoltaic power generation unit 10 by using the information displayed on the display unit 3 of the insulation resistance meter 1 of the present embodiment. And inspection of whether or not the solar cells constituting the photovoltaic power generation unit 10 are normally connected can be efficiently performed. In addition, since the insulation resistance value that can be measured by the insulation resistance meter 1 of the present embodiment is accurate, a slight reduction in resistance value is also reflected in the measurement value, which is useful for determining deterioration with time of the photovoltaic power generation unit 10. It can also be a good indicator.

  In addition, although embodiment mentioned above demonstrated the case where the 1st output terminal 21 connected to the + output terminal of the solar power generation unit 10 was made into a to-be-measured terminal, it is not restricted to this,-of solar power generation unit 10 The insulation resistance may be measured and displayed using the second output terminal 22 connected to the output terminal as the terminal to be measured. Further, the insulation resistance between the ground terminal 23 and the first output terminal 21 and the insulation resistance between the ground terminal 23 and the second output terminal 22 are respectively measured, and the insulation resistance values of the two (if normal, By determining the insulation state between the measurement object and the grounded part from the insulation resistance values of the measurement results that are substantially the same, the inside of the measurement object (between the first output terminal 21 and the second output terminal 22) Even if a disconnection occurs between solar cells, etc.), it is certain that the insulation state in each part of the measurement object (one output terminal side and the other output terminal side) is good or bad. And it can be easily checked.

  Further, the display time displayed on the display means 3 is not limited to the elapsed time from the start of measurement, and the elapsed time based on an arbitrary timing may be displayed. For example, the ground terminal 23 and the first output terminal 21 or the second output are not included without including the current measurement time between the ground terminal 23 and the first output terminal 21 or the second output terminal 22 that is performed in the state where the test voltage is not applied. If the display unit 3 can display the elapsed time from the inspection voltage application state in which the inspection voltage V is applied between the terminals 22, the elapsed time from the application of the inspection voltage V is a reference value ( For example, even if an inspection procedure for recording the insulation resistance value displayed on the Shoji device 3 of the insulation resistance meter 1 at the time when 1 minute) is reached, it can be handled. Or you may make it display the elapsed time from the time of displaying the said insulation resistance value initially.

  Further, in the insulation resistance meter 1 of the present embodiment, the resistance value is measured by connecting the overcurrent protection resistor 5 between the current measuring means 6 and the connection terminal 9b, so the calculation result of the measured resistance value The resistance value obtained by subtracting the known resistance value of the overcurrent protection resistor 5 from the current value needs to be corrected to the insulation resistance value and displayed on the display means 3, but when the insulation failure occurs in the measurement object, The overcurrent protection resistor 5 indicates that a large current A1 flows due to a potential difference (electromotive force of the measurement object) generated between the power generation unit 10 ground terminal 23 and the first output terminal 21 or the second output terminal 22. Therefore, it is possible to avoid a situation in which the insulation resistance meter 1 is damaged.

  Further, in the insulation resistance meter 1 according to this embodiment, the power supply means 7 applies the inspection voltage V based on the control signal S1 from the measurement control means 8 or stops the application of the inspection voltage V. Although the work process of measuring the insulation resistance can be automated, the present invention is not limited to this, and the application of the inspection voltage V and the stop of the application may be switched manually. Similarly, the current measuring means 6 is not limited to automatically instructing the measurement timing of the current value A1 in accordance with the control signal S2 from the measurement control means 8, but the user of the insulation resistance meter 1 is manually operated at an arbitrary timing. By doing so, you may make it perform the measurement process of the electric current value by the electric current measurement means 6. FIG.

  Moreover, although the insulation resistance meter 1 of this embodiment made the photovoltaic power generation unit 10 provided with the some solar cell module the "measurement object which has an electromotive force", it is not limited to this, A wind power generation unit, hydraulic power It is possible to measure and display the insulation resistance of various “measurement objects having electromotive force” such as a power generation unit, a tidal power generation unit, and a geothermal power generation unit at an appropriate timing.

  As mentioned above, although the embodiment of the insulation resistance meter to which the insulation resistance display method according to the present invention is applied has been described based on the accompanying drawings, the present invention is not limited to this embodiment, and is described in the claims. As long as the configuration is not changed, the known equivalent technical means may be diverted.

DESCRIPTION OF SYMBOLS 1 Insulation resistance meter 2 Real-time clock 3 Display means 4 Memory | storage means 5 Overcurrent protection resistance 6 Current measuring means 7 Feeding means 8 Measurement control means 9a Connection terminal 9b Connection terminal 10 Photovoltaic power generation unit 20 Connection box 21 1st connection terminal 22 1st 2 connection terminals 23 Ground terminal

Claims (8)

An elapsed time measuring step for measuring the passage of time based on the start of the measurement process of insulation resistance;
One of a pair of output terminals in a measurement object having an electromotive force is a measured terminal, and the measured terminal and the ground are connected in a state where no testing voltage is applied between the measured terminal and the grounded portion. The current flowing between the two parts is measured at a required interval twice or more, and the difference current value (ΔI) that is the difference between two current values obtained by two consecutive measurements and the two measurement intervals. A current change rate acquisition step for obtaining a current change rate (ΔI / Δt) from the elapsed time (Δt);
A saturation achievement condition determination step for determining whether or not the current change speed obtained in the current change speed acquisition step satisfies a predetermined saturation achievement condition;
A test current non-application voltage measurement current acquisition step in which the current flowing between the terminal to be measured and the grounded part when the saturation achievement condition is determined in the saturation achievement condition determination step is a measurement current when the test voltage is not applied; ,
After performing the measurement current acquisition step when the test voltage is not applied, in the test voltage application state in which the test voltage is applied between the measured terminal and the grounded portion, between the measured terminal and the grounded portion. A measurement current acquisition process when an inspection voltage is applied, which repeatedly measures the measurement current when the flowing inspection voltage is applied at a required interval;
Obtained by subtracting the measurement current value when the test voltage is not applied from the measurement current value when the test voltage is applied, every time the measurement current when the test voltage is applied is obtained in the measurement current acquisition process when the test voltage is applied. The insulation resistance value between the terminal to be measured and the grounded portion is obtained based on the inspection differential current value and the inspection voltage value, and the time measurement is started in the insulation resistance value and the elapsed time measuring step. An insulation resistance display process for simultaneously displaying the elapsed time from
An insulation resistance display method characterized by:   2. The insulation resistance display method according to claim 1, wherein in the insulation resistance display step, an elapsed time from the time when the voltage for inspection is applied is simultaneously displayed between the terminal to be measured and a grounded portion.   In the insulation resistance display step, it is possible to simultaneously display the elapsed time from the time when the insulation resistance value obtained based on the measurement current when the test voltage is applied first obtained in the test voltage application time measurement step is displayed. 3. The insulation resistance display method according to claim 1, wherein the insulation resistance is displayed. With the overcurrent protection resistor provided between the terminal to be measured and the ground part, the current change rate acquisition step, the measurement current acquisition step when the test voltage is not applied, and the measurement current acquisition when the test voltage is applied Shall carry out the process,
4. The insulation resistance display step, wherein the resistance value corrected by subtracting the overcurrent protection resistance value from the calculation result of the insulation resistance value is displayed as an insulation resistance value. The insulation resistance display method according to the item. At least a time measuring means capable of measuring the passage of time with reference to the start of the measurement process of insulation resistance,
One of a pair of output terminals in a measurement object having an electromotive force is a measured terminal, and a power feeding means capable of applying a test voltage between the measured terminal and a grounded part,
Current measuring means capable of measuring a current flowing between the terminal to be measured and a grounded part;
An inspection voltage application state in which an inspection voltage is applied between the terminal to be measured and the ground part by the power supply means, and an inspection voltage not applied between the terminal to be measured and the ground part. Measurement control for switching between states, obtaining an insulation resistance value using the measured current value measured by the current measuring means, and obtaining an elapsed time from any reference time using the time measured by the time measuring means Means,
Display means capable of simultaneously displaying at least the insulation resistance value obtained by the measurement control means and the elapsed time;
With
In the non-inspection voltage application state where the inspection voltage is not applied between the terminal to be measured and the grounded part, the measurement control means causes the current measuring means to pass a current flowing between the terminal to be measured and the grounded part. The current is measured from the difference current value (ΔI) which is a difference between two current values obtained by two or more measurements at a required interval and the elapsed time (Δt) which is the two measurement intervals. A change rate (ΔI / Δt) is obtained, and when the current change rate satisfies a predetermined saturation achievement condition, a current flowing between the terminal to be measured and the grounding part is stored as a measurement current when no test voltage is applied, Thereafter, a test voltage is applied by applying a test voltage between the terminal to be measured and the ground part, and a current measured when the test voltage is applied flowing between the terminal to be measured and the ground part is measured by the current measuring unit. Repeat measurement at required intervals Each time the measurement current when the test voltage is applied is measured, the test difference current value obtained by subtracting the measurement current value when the test voltage is not applied from the measurement current value when the test voltage is applied and the test voltage An insulation resistance value between the terminal to be measured and the grounded part based on the value, and the insulation resistance value and the elapsed time from the start of the measurement process are displayed on the display means at the same time. Total.   The measurement control means causes the display means to simultaneously display an elapsed time from the time when the inspection voltage is applied between the terminal to be measured and a grounded portion by the power supply means. Insulation resistance meter as described.   The measurement control means causes the display means to simultaneously display the elapsed time from the time when the insulation resistance value obtained based on the initially obtained measurement current value when applying the test voltage is displayed on the display means. The insulation resistance meter according to claim 5 or 6. Connect an overcurrent protection resistor between the terminal to be measured and the grounded part,
8. The measurement control means causes the display means to display the resistance value corrected by subtracting the overcurrent protection resistance value from the calculation result of the insulation resistance value as an insulation resistance value. The insulation resistance meter according to any one of the above.

Images