JP2015049216A - Insulation resistance measurement device, insulation resistance measurement method and insulation monitor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation resistance measurement device, an insulation resistance measurement method, and an insulation monitor device that can grasp reduction in insulation resistance without over-evaluating the insulation resistance and missing the reduction therein.SOLUTION: An insulation resistance measurement device 100 measures insulation resistance in a power generation part 11 made up of a solar battery string 18 plurally having a solar battery module 17. In the insulation resistance measurement device 100, in a state where a positive pole of the power generation part 11 is connected to a ground G, a voltage value in first load resistance between the positive pole thereof and the ground is measured, and further, in a state where a negative pole of the power generation part 11 is connected to the ground G, a voltage value in second load resistance between the negative pole thereof and the ground is measured. Furthermore, in a state where the positive pole of the power generation part 11 and the negative pole thereof are connected to each other, a voltage value in third load resistance between the positive pole and the negative pole is measured, where the first, second and third load resistance have resistance 12a commonly used, and are mutually set at the same predetermined resistance value.

Description

  The present invention relates to an insulation resistance measuring device, an insulation resistance measuring method, and an insulation monitoring device.

  In the solar power generation system, for example, a power generation unit is configured by a solar cell string including a plurality of solar cell modules including solar cells or a solar cell array including a plurality of solar cell strings, and sunlight is used by the power generation unit. Power generation is performed. If there is an insulation failure in such a power generation section, for example, when a person or object touches the insulation failure location, or when the insulation failure location and a metal mount contact, the electrical circuit contacts the outside in an unintended manner. A ground fault may occur. Therefore, for example, an insulation resistance measuring device described in Patent Document 1 is known as a device for measuring the insulation resistance related to the ground fault.

  In the insulation resistance measuring device described in Patent Document 1, the voltage value of the resistance (known resistance) on the ground line formed by grounding the positive electrode of the power generation unit (solar cell module circuit), and the grounding formed by grounding the negative electrode of the power generation unit It is intended to measure the voltage value of the resistance on the line and the voltage value (DC bus voltage) between the poles of the power generation unit, and determine the insulation resistance based on these measurement results.

JP-A-7-177646

Here, in the above-described insulation resistance measuring apparatus, for example, as shown in the following equation (a1), for the insulation resistance _RL , the voltage value V ₁ from the ground fault point to the positive electrode in the power generation unit and the ground fault point in the power generation unit A voltage value V ₂ from the negative electrode to the negative electrode, a current value I ₁ that flows through a ground line formed by grounding the positive electrode of the power generation unit, a current value I ₂ that flows through a ground line formed by grounding the negative electrode of the power generation unit, and a known resistance And may be calculated using the value _RD .
R _L = (V ₁ + V ₂ ) / (I ₁ + I ₂ ) −R _D (a1)

At this time, as the voltage value (V ₁ + V ₂ ), an open circuit voltage between the electrodes of the power generation unit is generally used. However, as shown in the following equation (b1), since the open discharge generation V _OC is equal to or higher than the voltage value (V ₁ + V ₂ ), the insulation resistance _RL is overestimated due to this, and the insulation There is a risk that a drop in resistance _RL may be overlooked. In particular, this is because the voltage value (V ₁ + V ₂ ) may be significantly lower than the open circuit voltage V _OC when the series resistance of the power generation unit is increased due to deterioration of the power generation unit or the like. It is not preferable.
(V ₁ + V ₂ ) ≦ V _OC (b1)

  The present invention has been made in view of the above circumstances, and provides an insulation resistance measuring device, an insulation resistance measuring method, and an insulation monitoring device that can be grasped without overestimating the insulation resistance without overlooking the decrease. Let it be an issue.

  In order to solve the above-mentioned problem, an insulation resistance measuring device according to the present invention is an insulation resistance measuring device for measuring an insulation resistance in a power generation unit constituted by at least one solar cell module, and includes a positive electrode of the power generation unit. A first measurement unit for measuring a voltage value or a current value at a first load resistance between the positive electrode and the ground in a state where the negative electrode and the ground are connected to the ground, and a negative electrode of the power generation unit is grounded to the ground. A voltage value at the third load resistance between the positive electrode and the negative electrode in a state where the second measurement unit for measuring the voltage value or the current value at the second load resistance between and the positive electrode and the negative electrode of the power generation unit are connected to each other A third measurement unit that measures a current value, and the resistance value of the third load resistor is equal to or less than the resistance value when the first and second load resistors have the same resistance value. , The first and second load resistances are Have different resistance values to have, that is less than one resistance smaller of the first and the resistance of the second load resistor, and wherein.

In this ground fault detection and measurement device, when the first and second load resistors have the same resistance value, the third load resistance that is the load resistance between the poles of the power generation unit is set to be equal to or less than the resistance value. When the second load resistance has a different resistance value, the resistance value is less than one of the resistance values of the first and second load resistances. following formula (c1) is established for the voltage value _{V a} is a value. Therefore, for example, by using the voltage value V _a as the voltage value (V ₁ + V ₂ ) of the above formula (a1), it becomes possible to monitor without fear of overestimating the insulation resistance, and as a result, the insulation resistance is reduced. It becomes possible to grasp without missing.
V _a ≦ V ₃ ≦ (V ₁ + V ₂ ) ... (c1)
V ₃ : Inter-electrode voltage value when the third load resistance is an insulation resistance and a predetermined resistance value.

Further, as a configuration that preferably exhibits the above-described effects, it is preferable that a calculation unit that calculates an insulation resistance based on the following equation (1-1) is provided.
R _L ≧ (R _D3 × I _a −R _D2 × I ₂ −R _D1 × I ₁ ) / (I ₁ + I ₂ ) (1-1)
Where I ₁ : current value in the first load resistance with the positive electrode of the power generation unit connected to the ground, I ₂ : current value in the second load resistance with the negative electrode of the power generation unit connected to the ground, I _a : current value in the third load resistor in a state where the positive electrode and the negative electrode of the power generation unit are connected to each other, R _D1 : the first load resistor, R _D2 : the second load resistor, R _D3 : the third load Resistance, R _L : Insulation resistance.

Moreover, it is preferable to provide the calculating part which calculates the position of a ground fault point based on the following Formula (1-2). In this case, it is possible to grasp the position of the ground fault point.
V ₁ : V ₂ = I ₁ × (R _D3 × I _a + I ₂ × (R _D1 −R _D2 )):
I ₂ × (R _D3 × I _a + I ₁ × (R _D2 −R _D1 )) (1-2)
However, V ₁ : Voltage value from the ground fault point to the positive electrode of the power generation unit, V ₂ : Voltage value from the ground fault point to the negative electrode of the power generation unit, I ₁ : In a state where the positive electrode of the power generation unit is connected to the ground Current value in the first load resistance, I ₂ : Current value in the second load resistance in a state where the negative electrode of the power generation unit is connected to the ground, R _D1 : First load resistance, R _D2 : Second load resistance, R _D3 : Third load resistance.

  In addition, as a configuration that preferably exhibits the above-described effects, specifically, it is preferable that the first, second, and third load resistors have the same predetermined resistance value.

  The measurement unit has a positive electrode and a negative electrode, and the voltmeter for measuring the voltage value of the resistance between the positive electrode and the negative electrode and the positive electrode of the voltmeter can be switched between the positive electrode and the ground of the power generation unit. A first switching connection portion to be connected; and a second switching connection portion for connecting the negative electrode of the voltmeter between the negative electrode of the power generation unit and the ground in a switchable manner. 3 load resistance is comprised by the resistance between the positive electrode of a voltmeter, and a negative electrode, and the 1st measurement part connects 2nd switching connection, connecting the positive electrode of a voltmeter to the positive electrode of an electric power generation part by a 1st switching connection part. In the state where the negative electrode of the voltmeter is connected to the ground by the unit, the voltage value or current value in the resistor is measured, and the second measuring unit connects the positive electrode of the voltmeter to the ground by the first switching connection unit, 2 Connect the negative electrode of the voltmeter to the negative electrode of the power The third measurement unit measures the voltage value or the current value, and connects the positive electrode of the voltmeter to the positive electrode of the power generation unit through the first switching connection unit, and the negative electrode of the voltmeter through the second switching connection unit. It is preferable to measure a voltage value or a current value in the resistor in a state where the resistor is connected. In this case, it is possible to measure the insulation resistance with only one voltmeter.

  Moreover, the insulation resistance measuring method according to the present invention is characterized in that the insulation resistance in the power generation unit is measured using the insulation resistance measuring device. This insulation resistance measuring method also has the above effect that it is possible to grasp the decrease without overestimating the insulation resistance without overestimating the insulation resistance. The insulation monitoring device according to the present invention is characterized in that the insulation resistance in the power generation unit is measured using the insulation resistance measurement device, and an alarm is issued when the measured insulation resistance is below a predetermined value. . Even in this insulation monitoring device, it is possible to grasp the decrease of the insulation resistance without overestimating it and not to overlook the decrease, and to notify the decrease of the insulation resistance by an alarm.

  According to the present invention, it is possible to grasp the insulation resistance without overestimating and overlooking the decrease.

It is a block diagram which shows the insulation resistance measuring apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the insulation resistance measuring method using the insulation resistance measuring apparatus of FIG. It is a graph which shows IV curve for demonstrating the insulation resistance measuring apparatus of FIG. It is a block diagram which shows the modification of the insulation resistance measuring apparatus of FIG. It is a block diagram which shows the insulation resistance measuring apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the insulation resistance measuring apparatus which concerns on 3rd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

[First Embodiment]
A first embodiment of the present invention will be described. FIG. 1 is a configuration diagram showing an insulation resistance measuring apparatus according to the first embodiment. As shown in FIG. 1, the insulation resistance measuring apparatus 100 of this embodiment is for measuring the insulation resistance of the power generation part 11 in a solar power generation system, and is the voltmeter 12, the 1st switching connection part 13, and the 2nd switching. The connection unit 14 is provided as the measurement unit 10. The insulation resistance measuring apparatus 100 includes a control unit (control unit) 15 and a calculation unit (calculation unit) 16.

  The power generation unit 11 is for generating power using sunlight, and includes a solar cell string 18 in which a plurality (six in the figure) of solar cell modules 17 are connected in series. The solar cell module 17 is configured in a panel shape, for example, and includes a plurality of solar cell units connected in series with each other. The power generation unit 11 may be configured by a solar cell array in which a plurality of solar cell strings 18 are connected in parallel.

  For example, the power generation unit 11 is connected to a power conditioner (not shown) and supplies a DC output to the power conditioner. The power conditioner converts a supplied DC output into an AC output and supplies it to a subsequent power system (for example, a commercial power system). The power conditioner may be a transformer insulation type having an insulation transformer or a transformer-less type. (Non-insulating) type may be used. However, it is preferable that the power generation unit 11 is insulated from the AC system while measuring the insulation resistance. For example, when the power generation unit 11 is not insulated from the AC system, it is difficult to distinguish the grounding of the AC system from an insulation failure, and accurate insulation measurement may not be performed. Therefore, when a transformerless power conditioner is used, it is preferable to measure the insulation resistance after disconnecting the electrical connection between the power generation unit 11 and the power conditioner with a switch device or the like.

The voltmeter 12 has a positive electrode and a negative electrode, and measures a voltage value of a resistor 12a provided between the positive electrode and the negative electrode. The voltmeter 12 outputs the measured voltage value to the arithmetic unit 16. As the voltmeter 12, various types can be used, and here, a unipolar type is used. The resistor 12a has a known predetermined resistance value _RD . Here, the resistor 12a is described separately from the voltmeter 12, but the resistor 12a may be an internal resistance (reception resistor) of the voltmeter 12. Further, when the receiving resistance of the voltmeter 12 is R1 and the resistance connected in parallel with the voltmeter 12 is R2, the resistor 12a has a parallel combined resistance (1 / (1 / R1) + (1 / R2) ).

  The first switching connection unit 13 connects the positive electrode of the voltmeter 12 so as to be switchable between the positive electrode of the power generation unit 11 and the ground G. Specifically, the first changeover connection unit 13 includes a changeover switch 19b and a positive electrode wiring 13x connected to the positive electrode of the power generation unit 11 from the positive electrode of the voltmeter 12 (the positive side of the resistor 12a) via the changeover switch 19a. And a positive electrode wiring 13 y connected to the ground G from the positive electrode of the voltmeter 12.

  The second switching connection unit 14 connects the negative electrode of the voltmeter 12 to be switchable between the negative electrode of the power generation unit 11 and the ground G. Specifically, the second changeover connection unit 14 includes a changeover switch 19d and a negative electrode line 14x connected to the negative electrode of the power generation unit 11 from the negative electrode of the voltmeter 12 (the negative electrode side of the resistor 12a) via the changeover switch 19c. And a negative electrode wiring 14 y connected to the ground G from the negative electrode of the voltmeter 12.

  As the change-over switches 19a to 19d, any configuration can be used as long as it cuts off the current. For example, semiconductor switches such as FET (Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor), mechanical relays, etc. Can be used (the same applies to the following switches).

  The control unit 15 controls switching in the first and second switching connection units 13 and 14. Specifically, the control unit 15 turns on the changeover switch 19a and turns off the changeover switch 19b, connects the positive electrode of the voltmeter 12 to the positive electrode of the power generation unit 11, turns off the changeover switch 19c, and turns off the changeover switch 19d. Turn ON to connect the negative electrode of the voltmeter 12 to the ground G.

  Further, the control unit 15 turns off the changeover switch 19c and turns off the changeover switch 19d when the changeover switch 19a is turned off and the changeover switch 19b is turned on to connect the positive electrode of the voltmeter 12 to the ground G. Are connected to the negative electrode of the power generation unit 11. Furthermore, the control unit 15 turns on the changeover switch 19a and turns off the changeover switch 19b, connects the positive electrode of the voltmeter 12 to the positive electrode of the power generation unit 11, turns on the changeover switch 19c and turns off the changeover switch 19d. The negative electrode of the voltmeter 12 is connected to the negative electrode of the power generation unit 11.

  The arithmetic unit 16 calculates and calculates the insulation resistance based on the voltage value measured by the voltmeter 12. The arithmetic unit 16 may be configured by a dedicated ECU [Electronic Control Unit], or may be configured as an application in a general-purpose computer such as a personal computer. Details of the calculation by the calculation unit 16 will be described later.

In the insulation resistance measuring apparatus 100 configured in this way, the load resistance (hereinafter referred to as “first load”) between the positive electrode of the power generation unit 11 and the ground G in a state where the positive electrode of the power generation unit 11 is connected to the ground G. Resistance ”), the load resistance between the negative electrode of the power generation unit 11 and the ground G in a state where the negative electrode of the power generation unit 11 is grounded to the ground G (hereinafter,“ second load resistance ”), and the positive electrode of the power generation unit 11 The load resistance between the positive electrode and the negative electrode of the power generation unit 11 in a state where the negative electrode and the negative electrode are connected to each other (hereinafter referred to as “third load resistance”) is configured by the resistor 12 a between the positive electrode and the negative electrode of the voltmeter 12. And have the same predetermined resistance value _RD .

Next, measurement of insulation resistance by the insulation resistance measuring apparatus 100 will be described. FIG. 2 is a diagram for explaining an insulation resistance measurement method using the insulation resistance measurement apparatus of FIG. Here, as shown in FIG. 2, a ground fault occurs when a ground fault occurs between certain solar cell modules 17 x and 17 y, and the insulation resistance of the solar cell string 18 decreases to the insulation resistance _RL. To do.

In the insulation resistance measuring method using the insulation resistance measuring apparatus 100, the changeover switches 19a and 19d are turned on and the changeover switch is turned on by the control unit 15 as shown in FIG. 19b and 19c are turned OFF, the positive electrode of the voltmeter 12 is connected to the positive electrode of the power generation unit 11, and the negative electrode of the voltmeter 12 is connected to the ground G. Thereby, the positive electrode side of the power generation unit 11 is grounded to the ground G, that is, a ground wire is formed which is connected in this order from the positive electrode of the power generation unit 11 to the changeover switch 19a, the resistor 12a, the changeover switch 19d, and the ground G. . In this state, the voltmeter 12 measures the voltage value of the resistor 12a as the first voltage value V _D1 that is the voltage value at the first load resistor. Because both have the have ground fault occurs at a point, the potential of that portion is positive or less, the direction of the current I ₁ flowing through the resistor 12a becomes a as shown in FIG. 2 (a), the positive electrode negative electrode fixed It is possible to measure the first voltage value V _D1 with the monopolar voltmeter 12 made.

Further, as shown in FIG. 2B, in a state where the power generation unit 11 is opened, the control unit 15 turns on the changeover switches 19b and 19c and turns off the changeover switches 19a and 19d, thereby Is connected to the ground G, and the negative electrode of the voltmeter 12 is connected to the negative electrode of the power generation unit 11. Thereby, the negative electrode side of the power generation unit 11 is grounded to the ground G, that is, a ground line is formed which is connected in this order from the negative electrode of the power generation unit 11 to the changeover switch 19c, the resistor 12a, the changeover switch 19b, and the ground G. . In this state, the voltmeter 12 measures the voltage value of the resistor 12a as the second voltage value V _D2 that is the voltage value at the second load resistor. Because both are of ground fault at the point has not occurred, the potential of the point is more negative, the direction of the resistor 12a through current I ₂ becomes a as shown in FIG. 2 (b), the positive electrode negative electrode is fixed The second voltage value V _D2 can be measured with a monopolar voltmeter 12.

Furthermore, as shown in FIG. 2 (c), the control unit 15 turns on the changeover switches 19 a and 19 c and turns off the changeover switches 19 b and 19 d to connect the positive electrode of the voltmeter 12 to the positive electrode of the power generation unit 11. In addition, the negative electrode of the voltmeter 12 is connected to the negative electrode of the power generation unit 11. Thereby, the poles of the power generation unit 11 are connected to each other, that is, a closed circuit is formed which is connected in this order from the positive electrode of the power generation unit 11 to the changeover switch 19a, the resistor 12a, the changeover switch 19c, and the negative electrode of the power generation unit 11. To do. In this state, the voltage value of the resistor 12a is measured by the voltmeter 12 as _a third voltage value Va that is a voltage value at the third load resistor. In this case, it is needless to say that can measure the third voltage value V _a voltmeter 12 monopolar the positive electrode negative electrode is fixed.

  As described above, when the positive electrode of the power generation unit 11 is connected to the voltmeter 12, it is always connected to the positive electrode of the voltmeter 12, and when the negative electrode of the power generation unit 11 is connected to the voltmeter 12, it is always connected to the negative electrode of the voltmeter 12. Due to the configuration, a monopolar voltmeter 12 can be used. This is because even if a ground fault occurs at any position in the power generation unit 11, the potential is equal to or lower than the potential of the positive electrode of the solar cell, and thus the resistance 12 a when the positive electrode of the power generation unit 11 is connected to the voltmeter 12. The direction of the current inside is the direction of flowing from the power generation unit 11 to the ground G, and any potential in the power generation unit 11 is caused by the potential being equal to or higher than the potential of the solar cell negative electrode. This is because the direction of the current in the resistor 12 a when the negative electrode of the power generation unit 11 is connected to the voltmeter 12 is the direction of flowing from the ground G into the power generation unit 11.

Subsequently, the arithmetic unit 16 measures the insulation resistance _RL based on the first to third voltage values V _D1 , V _D2 , and V _a . First, the principle of measurement of the insulation resistance _RL will be described.

In a state where the positive electrode side was grounded to the earth G of the power generation unit 11 (see FIG. 2 (a)), the current value I ₁ which flows can be expressed by the following equation (2). Further, in a state where the negative electrode side of the power generation unit 11 is grounded to the ground G (see FIG. 2B), the flowing current value I ₂ can be expressed by the following equation (3).
I ₁ = V ₁ / (R _L + R _D ) (2)
I ₂ = V ₂ / (R _L + R _D ) (3)
V ₁ : voltage value by the solar cell module 17 from the ground fault point to the positive electrode of the power generation unit 11,
V ₂ : voltage value by the solar cell module 17 from the ground fault point to the negative electrode of the power generation unit 11,
R _D : predetermined resistance value.

Therefore, as shown in the following formulas (4) to (6), the insulation resistance _RL can be calculated from the voltage value (V ₁ + V ₂ ) and the current value (I ₁ + I ₂ ).
I ₁ + I ₂ = (V ₁ + V ₂ ) / (R _L + R _D ) (4)
(V ₁ + V ₂ ) / (I ₁ + I ₂ ) = R _L + R _D (5)
R _L = (V ₁ + V ₂ ) / (I ₁ + I ₂ ) −R _D (6)
Further, the position of the ground fault point can be determined based on the following equation.
V ₁ : V ₂ = I ₁ : I ₂

  FIG. 3 is a graph showing an IV curve for explaining the insulation resistance measuring apparatus of FIG. In FIG. 3, an IV curve C <b> 1 indicates a four series IV curve of the solar cell module 17 from the ground fault point to the positive electrode of the power generation unit 11, and an IV curve C <b> 2 indicates a solar cell module 17 from the ground fault point to the negative electrode of the power generation unit 11. The IV curve C3 shows the 6 series IV curve of the solar cell module 17 between the poles of the power generation unit 11. At the same current value, the voltage value of the IV curve C3 is the sum of the voltage value of the IV curve C1 and the voltage value of the IC curve C2. In the drawing, for the convenience of explanation, the low current portion is shown enlarged and emphasized.

In a state where the positive electrode side of the power generation unit 11 is grounded to the ground G and a state where the negative electrode side of the power generation unit 11 is grounded to the ground G, an insulation resistance R _L and a predetermined resistance value R _D are connected in series as a load resistance. It is connected to the. Therefore, as shown in FIG. 3, the voltage values V ₁ and V ₂ that are the operating voltages of the power generation unit 11 in these states are at the intersections of the IV curves C1 and C2 and the straight line I = V (R _L + R _D ). It is a voltage value. Since the open circuit voltage V _{OC of the} entire power generation unit 11 is V _OC = V _OC1 + V _OC2 , V ₁ + V ₂ ≦ V _OC is _satisfied .
V _OC1 : Open-circuit voltage of the solar cell module 17 from the ground fault point to the positive electrode of the power generation unit 11,
V _OC2: open-circuit voltage of the solar cell module 17 from the ground絡点to the negative electrode of the power generation unit 11.

Therefore, if the open circuit voltage V _OC is used as a substitute for the voltage value (V ₁ + V ₂ ) in the above equation (6), the insulation resistance _RL may be overestimated and the insulation resistance _RL may be overlooked. In particular, when the series resistance of the power generation unit 11 is increased, the voltage value (V ₁ + V ₂ ) may be significantly lower than the open circuit voltage V _OC , and thus overestimation of the insulation resistance _RL becomes significant. Moreover, when the electric power generation part 11 has deteriorated, we are anxious about the serial resistance also increasing simultaneously with the fall of insulation resistance.

On the other hand, the inter-electrode voltage V _{3 of the} entire power generation unit 11 at the load resistance (R _L + R _D ) is V ₃ ≦ V ₁ + V ₂ . Therefore, if the inter-electrode voltage V ₃ is used as a substitute for the voltage value (V ₁ + V ₂ ) in the above equation (6), it is possible to avoid overestimating the insulation resistance _RL , but the insulation resistance _RL is unknown. there, it is difficult to determine the inter-electrode voltage V ₃ accurately.

In this regard, the minimum value of the inter-electrode voltage V ₃ may be predicted as follows. That is, if the insulation resistance R _L decreases, the load resistance (R _L + R _D ) decreases to the predetermined resistance value R _D, so the minimum value of the interelectrode voltage V ₃ is the third voltage value V _a (load resistance Is the inter-electrode voltage V ₃ ) of the entire power generation section 11 when the predetermined resistance value _RD . Therefore, since the _{V a ≦ V 3 ≦ V 1} + V 2, as the voltage value in the above formula _{(6) (V 1 + V} 2), the use of the third voltage value _{V a,} overestimating the insulation resistance _{R L} It is found that measurement can be performed while suppressing the fear of

Therefore, the arithmetic unit 16 of this embodiment calculates and measures the insulation resistance _RL based on the following equations (7) and (8). As described above, in the following formulas (7) and (8), V _D1 is a voltage value (first voltage value) at the first load resistor in a state where the positive electrode of the power generation unit 11 is connected to the ground G, V _D2 is the voltage value at the second load resistor in a state of being connected to the negative electrode of the power generation unit 11 to the ground G (second voltage value), V _a is in a state of being connected together to the positive and negative electrodes of the power generation portion 11 A voltage value (third voltage value) at the third load resistance, I ₁ is a current value at the first load resistance in a state where the positive electrode of the power generation unit 11 is connected to the ground G, and I ₂ is a ground value of the negative electrode of the power generation unit 11. The current value at the second load resistance in the state of being connected to G, I _a is the current value of the third load resistance when the positive and negative electrodes of the power generation unit 11 are connected to each other, R _D is the predetermined resistance value, R _L is an insulation resistance.
R _L ≧ (I _a / (I ₁ + I ₂ ) −1) × R _D (7)
_{I a = V a / R D} , I 1 = V D1 / R D, I 2 = V D2 / R D ... (8)

The above equation (7) can be obtained from V ₁ + V ₂ ≧ V _a = I _a × _RD and the above equation (6). That is, the insulation resistance _RL is
(I _a / (I ₁ + I ₂ ) −1) × R _D
Since the true value of the insulation resistance _RL is equal to or higher than the evaluation value, it is possible to grasp without missing the decrease in the insulation resistance _RL .

In the present embodiment, as shown in FIG. 1, the first load resistor, the second load resistor, and the third load resistor are all configured by a resistor 12 a between the positive electrode and the negative electrode of the voltmeter 12. Explained the case. As described above, when the first to third load resistors are configured only by the resistance to be measured by the voltmeter 12, the voltmeter 12 does not calculate the current value, as shown in the following equation (9). Needless to say, the measured values may be used directly.
R _L ≧ (V _a / (V _D1 + V _D2 ) −1) × R _D (9)
In this case, it goes without saying that the value measured by the voltmeter may be directly used for the position of the ground fault point without using the current value (see the following equation).
V ₁ : V ₂ = V _D1 : V _D2

Incidentally, the predetermined resistance value _RD is preferably set to the following value in order to accurately measure the insulation resistance _RL . That is, if the predetermined resistance value _RD is too small, a ground fault occurs. Therefore, it is preferable that the threshold value is equal to or higher than the threshold value for determining a ground fault. If the predetermined resistance value _RD is too large, the time to wait until the ground potential stabilizes when measuring the current values I1 and I2 becomes longer and the measurement time becomes longer. Therefore, the measurement accuracy decreases in the measurement with a short measurement time. To do. The predetermined resistance value _RD is preferably equal to or less than a value obtained by dividing the time allowed for measurement by the ground capacitance and further dividing by a predetermined value (here, 3).

As described above, in the present embodiment, the first voltage value V _D1 is measured with the positive electrode of the power generation unit 11 connected to the ground G, and the second voltage value V _D with the negative electrode of the power generation unit 11 grounded to the ground G. _D2 is measured, and the third voltage value Va is measured in _a state where the positive electrode and the negative electrode of the power generation unit 11 are connected to each other. Here, the first load resistance between the positive electrode and the ground of the power generation unit 11, the second load resistance between the negative electrode and the ground of the power generation unit 11, and the third load resistance between the positive electrode of the power generation unit 11 and the negative electrode are: Since the resistor 12a is also used to have the same predetermined resistance value R _D , V _a ≦ V ₃ ≦ V ₁ + V ₂ is established for the third voltage value V _a .

Therefore, by calculating the insulation resistance _RL with the right side of the above equation (7) using the third voltage value V _a as the voltage value (V ₁ + V ₂ ) of the above equation (6), the insulation resistance _RL is It is possible to monitor without fear of overestimation, and as a result, it becomes possible to grasp without missing a decrease in the insulation resistance _RL . In addition, for example, the software relating to the calculation of the device configuration and the insulation resistance _RL becomes simple, and it is possible to manufacture the insulation resistance measuring device 100 that is reliable and inexpensive in operation.

  Further, in the present embodiment, as described above, the position of the ground fault point can be calculated and determined, so that the position of the ground fault point can also be grasped.

Further, in the present embodiment, as described above, it is possible only by a single voltmeter 12 to measure the insulation resistance R _L, it is possible to measure the insulation resistance R _L with a simple configuration. Further, as described above, the voltmeter 12 does not need a bipolar type (bipolar) that is a voltmeter capable of determining the direction of the voltage, and can be a unipolar type (monopolar). . That is, according to the present embodiment, it is possible to realize three measurements (measurement of voltage values V _D1 , V _D2 , and V _a ) with one voltmeter 12 that can measure only a positive voltage. As a result, not only cost reduction but also maintenance can be facilitated.

In the above, the first and second changeover connection parts 13 and 14, the changeover switches 19a and 19d, the resistor 12a and the voltmeter 12 measure the first voltage value _VD1 by connecting the positive electrode of the power generation part 11 to the ground G. The first measurement unit is configured. The switch 19b switched to the first and second switch connection 13, 14, and 19c and the resistor 12a and the voltmeter 12 measures a second voltage value _{V D2} grounds the negative electrode to the earth G of the power generation portion 11 A second measurement unit is configured. The switch 19a switching the first and second switch connection 13, 14, and 19c and the resistor 12a and the voltmeter 12 measures a third voltage value _{V a} by mutually connecting the positive and negative electrodes of the power generation portion 11 A third measurement unit is configured.

FIG. 4 is a configuration diagram showing a modification of the insulation resistance measuring apparatus of FIG. As shown in FIG. 4, the insulation resistance measuring apparatus 100 includes a C contact 20a in place of the changeover switches 19a and 19b (see FIG. 1) and a C contact in place of the changeover switches 19c and 19d (see FIG. 1). A contact 20b may be provided. As a result, the wiring can be simplified, and as a result, the insulation resistance _RL can be measured with a simpler configuration.

In the present embodiment, the first load resistor, the second load resistor, and the third load resistor are not configured by only the resistor 12a connected in parallel to the voltmeter 12, but may be configured including a protective resistor. . That is, one or a plurality of protective resistors may be arranged in the first switching connection portion 13 and / or the second switching connection portion 14 so that the resistance values of the first to third load resistors are equal to each other. . In this case, the calculation unit 16 can calculate and measure the insulation resistance _RL based on the following equations (10) and (11). In the following formulas (10) and (11), V _D1 is a voltage value in the resistor 12a in a state where the positive electrode of the power generation unit 11 is connected to the ground G, and V _D2 is a negative value of the power generation unit 11 connected to the ground G. voltage value at the resistor 12a in a state of being, V _a is the voltage value, I ₁ is to connect the positive electrode of the power generation unit 11 to the ground G in the resistance 12a in the state of being connected together to the positive and negative electrodes of the power generation portion 11 The current value in the first load resistance in the state, I ₂ is the current value in the second load resistance in a state where the negative electrode of the power generation unit 11 is connected to the ground G, _RD is the resistance value of the resistor 12a, and _RP is each The sum of the protective resistance values in the first to third load resistors, R _L is the insulation resistance value. Here, the predetermined resistance value is (R _D + R _P ).
R _L ≧ (I _a / (I ₁ + I ₂ ) −1) × (R _D + R _P ) (10)
_{I a = V a / R D} , I 1 = V D1 / R D, I 2 = V D2 / R D ... (11)

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the description of the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 5 is a configuration diagram showing an insulation resistance measuring apparatus according to the second embodiment. As shown in FIG. 5, the insulation resistance measuring apparatus 200 of the present embodiment is different from the first embodiment in that the first to third measuring units 211 to 213 are replaced with the measuring unit 10 (see FIG. 1). It is the point provided with the measurement part 210 which has.

First measuring unit 211 includes a first resistor 12a1 having a predetermined resistance value _{R D,} a first voltmeter 12 ₁ for measuring the voltage value of the first resistor 12a1, a first voltage via the changeover switch 219a total of 12 ₁ of the positive electrode positive first wiring 21 ₁ connected to the pole, switching first voltmeter 12 ₁ of the negative electrode via a switch 219b (the negative electrode side of the first resistor 12a1 of the power generation unit 11 (the positive electrode side of the first resistor 12a1) ) and the first wiring 22 ₁ connected to the ground G, contains.

The second measuring unit 212 includes a second resistor 12a2 having a predetermined resistance value _{R D,} a second voltmeter 12 ₂ that measures a voltage value of the second resistor 12a2, the second voltage via the changeover switch 219c meter 12 generating a _second positive electrode (positive electrode side of the second resistor 12a2) and the second wiring 21 ₂ connected to the ground G, through the changeover switch 219d second voltmeter 12 ₂ of the negative electrode (negative electrode side of the second resistor 12a2) the second wiring 22 ₂ connected to the negative electrode parts 11, contains.

Third measuring unit 213 includes a third resistor 12a3 having a predetermined resistance value _{R D,} a third voltmeter 12 ₃ for measuring the voltage value of the third resistor 12a3, the third voltage through the changeover switch 219e meter 12 ₃ of the positive electrode (positive electrode side of the third resistor 12a3) and the third wiring 21 ₃ connected to the positive electrode of the power generation portion 11, via a changeover switch 219f third voltmeter 12 ₃ of the negative electrode (negative electrode side of the third resistor 12a3 ) and the third wiring 22 ₃ connected to the negative electrode of the power generation unit 11 includes a.

In the insulation resistance measuring method using the insulation resistance measuring apparatus 200 of the present embodiment, the control unit 15 turns on the changeover switches 219a and 219b and turns off the changeover switches 219c to 219f so that the positive electrode side of the power generation unit 11 is turned on. Ground to ground G. In this state, the first voltmeter 12 _1, measures the voltage value of the first resistor 12a1 as a first voltage value _{V D1.}

Further, the control unit 15 turns on the changeover switches 219c and 219d and turns off the changeover switches 219a, 219b, 219e, and 219f, and grounds the negative electrode side of the power generation unit 11 to the ground G. In this state, the second voltmeter 12 _2, measures the voltage value of the second resistor 12a2 as the second voltage value _{V D2.}

Furthermore, the control unit 15 turns on the changeover switches 219e and 219f and turns off the changeover switches 219a to 219d to connect the poles of the power generation unit 11 to each other. In this state, the third voltmeter 12 _3, measures the voltage value of the fourth resistor 12a3 as a third voltage value _{V a.}

As described above, also in the present embodiment, the first load resistance, the second load resistance, and the third load resistance have the same predetermined resistance value _RD, and therefore, the insulation resistance _RL can be monitored without overestimating. Thus, the above-described effect is achieved that it is possible to grasp the decrease in the insulation resistance _RL without overlooking it.

In the present embodiment, the first resistor 12a1, the second resistor 12a2, and the third resistor 12a3 are all described as having the same resistance value _RD . However, the first load resistor, the second load resistor, and the third load are described. The resistors need only have the same predetermined resistance value, and the resistors 12a1 to 12a3 to be measured by the voltmeters 12 _{1 to} 12 ₃ need not all have the same value. For example, in FIG. 5, a first protection resistor _{R 1} to the first wiring 21 _1, second protective resistor _{R 2,} the third protection resistor _{R 3} respectively arranged in the third wiring 21 ₃ to the second wiring 22 ₂ a first load resistor (the sum of the first protective resistor _{R 1} and the first resistor 12a1), and a second load resistor (the sum of the second protective resistor _{R 2} and the second resistor 12a2), the third load resistor ( it can be a third protection resistor R ₃ the sum of the third resistor 12a3) is designed to mutually the same predetermined resistance value.

Furthermore, in the present embodiment, the first, second and third load resistors do not have to have the same predetermined resistance value. In short, the resistance value of the third load resistor is the first and second loads. When the resistors have the same resistance value, the resistance value is equal to or less than the resistance value. When the first and second load resistors have different resistance values, the smaller one of the resistance values of the first and second load resistors ( It may be set to be equal to or less than the resistance value of one that is not large. In this case, for example, as illustrated below, it is possible to grasp without missing the decrease in the insulation resistance _RL , and it is possible to grasp the position of the ground fault point (ground fault position).

First, when the positive electrode of the power generation unit 11 is grounded via the first load resistor having the resistance value R _D1 , the voltage generated in the first load resistor is set to the first voltage value V _D1, and the ground fault at this time the voltage of the power generation unit 11 to the positive electrode and the voltage value V ₁ from the point. When the negative electrode of the power generation unit 11 is grounded via the second load resistor having the resistance value R _D2 , the voltage generated in the second load resistor is set to the second voltage value V _D2, and the ground fault point at this time the voltage of the power generation portion 11 to the negative electrode and the voltage value V _2. When the positive electrode and the negative electrode of the power generation unit 11 are connected via a third load resistor having a resistance value R _D3 , a voltage generated in the third load resistor is defined as _a third voltage value Va.

In this case, the following expressions (A) and (B) are established. Further, from R _D3 ≦ R _D1 and R _D3 ≦ R _D2 , the following expression (C) is established.
V _D1 = V ₁ × R _D1 / (R _L + R _D1 ) (A)
V _D2 = V ₂ × R _D2 / (R _L + R _D2 ) (B)
V ₁ + V ₂ ≧ V _a (C)

Then, the following equation can be obtained from the above equations (A), (B), and (C).
R _L ≧ R _D1 × R _D2 × (V _a −V _D1 −V _D2 )
/ (R _D1 × V _D2 + R _D2 × V _D1 )
That is, it is assumed that V ₁ + V ₂ = V _a, and the insulation resistance _RL is R _D1 × R _D2 × (V _a −V _D1 −V _D2 ) / (R _D1 × V _D2 + R _D2 × V _D1 )
Since the true value of the insulation resistance _RL is equal to or higher than the evaluation value, it is possible to grasp without missing the decrease in the insulation resistance _RL .

Furthermore, in this case, it is possible to estimate the ground fault position by the following equation.
V ₁ : V ₂ = V _D1 × (R _D2 × V _a + V _D2 × (R _D1 −R _D2 )):
V _D2 × (R _D1 × V _a + V _D1 × (R _D2 −R _D1 ))
Note that any of the resistance values R _D1 , R _D2 , and R _D3 of the load resistance can be configured by a combination of a plurality of resistors. At this time, the above calculation may be performed by _obtaining the voltage values V _D1 , V _D2 , and V _a from the voltage values of some of the resistors.

Alternatively, the insulation resistance _RL and the ground fault position may be obtained based on currents flowing through the first, second, and third load resistors. For example, in the above example, the current flowing through the first load resistor and a current value I ₁ of the positive electrode of the power generation unit 11 when the grounded via a first load resistor, via a negative electrode second load resistor of the power generation portion 11 the current flowing through the second load resistor and a current value I ₂ upon grounded Te, third load resistor when the via third load resistor having a resistance value R _D3 between the positive electrode and the negative electrode of the power generation unit 11 are connected to each other If the current value _{I a} current flowing to the following formula (D), satisfied (E), _{also, R D3} ≦ _{R D1, and,} from the _{R D3} ≦ _{R D2,} the following equation (F) is satisfied .
I ₁ = V ₁ / (R _L + R _D1 ) (D)
I ₂ = V ₂ / (R _L + R _D2 ) (E)
V ₁ + V ₂ ≧ V _a (F)

Then, the following equation can be obtained from the above equations (D), (E), and (F).
R _L ≧ (V _a −R _D2 × I ₂ −R _D1 × I ₁ ) / (I ₁ + I ₂ )
That is, since V ₁ + V ₂ = V _a and V _a = R _D3 × I _a , the insulation resistance R _L is
(R _D3 × I _a −R _D2 × I ₂ −R _D1 × I ₁ ) / (I ₁ + I ₂ )
Since the true value of the insulation resistance _RL is equal to or higher than the evaluation value, it is possible to grasp without missing the decrease in the insulation resistance _RL .

Furthermore, in this case, it is possible to estimate the ground fault position by the following equation.
V ₁ : V ₂ = I ₁ × (R _D3 × I _a + I ₂ × (R _D1 −R _D2 )):
I ₂ × (R _D3 × I _a + I ₁ × (R _D2 −R _D1 ))

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the description of the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 6 is a configuration diagram illustrating an insulation resistance measuring apparatus according to the third embodiment. As shown in FIG. 6, the insulation resistance measuring apparatus 300 of the present embodiment is different from the first embodiment in that a ground measuring unit 311 and an inter-electrode measuring unit 312 are used instead of the measuring unit 10 (see FIG. 1). It is the point provided with the measurement part 310 which has.

  The ground measurement unit 311 constitutes a first measurement unit and a second measurement unit, and includes a resistor 31, a bipolar voltmeter 32 that measures the voltage value of the resistor 31, and a voltmeter 32 via a changeover switch 319a. A wiring 33x that connects one side of the voltmeter 32 to the positive electrode of the power generation unit 11, a wiring 33y that connects one side of the voltmeter 32 to the positive electrode of the power generation unit 11 via the changeover switch 319b, and a ground G And a wiring 34 connected to the. The wiring 33x is provided with a resistor 35x, and the wiring 33y is provided with a resistor 35y.

  The inter-electrode measuring unit 312 constitutes a third measuring unit, and a resistor 36, a voltmeter 37 for measuring the voltage value of the resistor 36, and a positive electrode of the voltmeter 37 via a changeover switch 319c are generated as a power generation unit. 11, and a wiring 39 that connects the negative electrode of the voltmeter 37 to the negative electrode of the power generation unit 11 via the changeover switch 319 d.

In this embodiment, the sum of the resistance value of the resistor 31 and the resistance value of the resistor 35x, the sum of the resistance value of the resistor 31 and the resistance value of the resistor 35y, and the resistance value of the resistor 36 are the same. Here, the predetermined resistance value _RD is used. As a result, also in the present embodiment, the first load resistance, the second load resistance, and the third load resistance have the same predetermined resistance value R _D, and therefore, the insulation resistance R _L can be monitored without overestimating. In addition, the above-described effect is achieved that it is possible to grasp without missing the decrease in the insulation resistance _RL .

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention is modified without departing from the scope described in the claims or applied to others. It may be.

  For example, the number of solar cell units constituting the solar cell module 17, the number of solar cell modules 17 constituting the solar cell string 18, the number of solar cell strings 18 constituting the solar cell array, and the photovoltaic power generation system are constituted. The number of solar cell arrays to be performed is not limited, and may be one or plural.

In the above embodiment, the first measuring section was measured first voltage value V _D1, may measure the current value I _1. Further, the second measuring section was measured second voltage value V _D2, may measure the current value I _2. In the present invention, the configuration of the measurement unit is not limited, and various configurations may be employed as long as the first load resistance, the second load resistance, and the third load resistance have the same predetermined resistance value. be able to. In addition, the said embodiment can also be grasped | ascertained as a solar cell string provided with the insulation resistance measuring apparatus, a solar cell array, or a solar power generation system.

  Moreover, the insulation resistance measuring apparatus according to any of the first to third embodiments can also be regarded as an insulation monitoring apparatus further provided with an alarm unit. That is, the present invention measures the insulation resistance in the power generation unit 11 using any one of the insulation resistance measuring devices 100, 200, and 300, and issues an alarm when the insulation resistance that is the measurement result is below a predetermined value. It can also be understood as an insulation monitoring device.

In this case, for example, the alarm unit compares the insulation resistance _RL of the power generation unit 11 calculated by the arithmetic unit 16 with a predetermined value stored in advance in the storage device (comparison determination process), and the insulation resistance _RL is predetermined. Raise an alarm when below the value. The alarm unit may emit a sound such as a buzzer, may indicate that there is a ground fault on the monitor, or alarm signal by wireless or wired to a separate monitoring system. May be transmitted, or at least one of these may be included. The comparison determination process of the alarm unit may be executed by the arithmetic unit 16.

  “Connection between positive electrode of power generation unit 11 and ground G”, “Connection between negative electrode of power generation unit 11 and ground G”, “Connection between positive electrode and negative electrode of power generation unit 11”, “Negative electrode of voltmeter 12” "Connection with the ground G", "Connection between the positive electrode of the voltmeter 12 and the positive electrode of the power generation unit 11", "Connection between the positive electrode of the voltmeter 12 and the ground G", "Negative electrode of the voltmeter 12 and the negative electrode of the power generation unit 11" And “connection between the negative electrode of the voltmeter 12 and the ground G”, one or more electronic components (elements) such as resistors and switches are interposed between the two connected. In short, it is only necessary that both are electrically connected to each other.

  DESCRIPTION OF SYMBOLS 10,210,310 ... Measurement part, 11 ... Electric power generation part, 12 ... Voltmeter (1st measurement part, 2nd measurement part, 3rd measurement part), 12a ... Resistance (1st measurement part, 2nd measurement part, 1st 3 measurement unit), 13 ... first switching connection unit (first measurement unit, second measurement unit, third measurement unit), 14 ... second switching connection unit (first measurement unit, second measurement unit, third measurement) Part), 16 ... arithmetic unit (arithmetic part), 17 ... solar cell module, 18 ... solar cell string, 19a ... changeover switch (first measurement part, third measurement part) 19b ... changeover switch (second measurement part), 19c ... changeover switch (second measurement unit, third measurement unit), 19d ... changeover switch (first measurement unit), 100, 200, 300 ... insulation resistance measuring device, 211 ... first measurement unit, 212 ... second measurement , 213... Third measurement unit, 311... Ground measurement unit (first measurement unit, second measurement. ), 312 ... interpolar measuring section (third measuring unit), G ... earth.

Claims (7)

An insulation resistance measuring device for measuring an insulation resistance in a power generation unit constituted by at least one solar cell module,
A first measurement unit for measuring a voltage value or a current value in a first load resistance between the positive electrode and the ground in a state where the positive electrode of the power generation unit is connected to the ground;
A second measuring unit for measuring a voltage value or a current value in a second load resistance between the negative electrode and the ground in a state where the negative electrode of the power generation unit is grounded to the ground;
A third measurement unit that measures a voltage value or a current value at a third load resistance between the positive electrode and the negative electrode in a state where the positive electrode and the negative electrode of the power generation unit are connected to each other;
The resistance value of the third load resistor is
When the first and second load resistors have the same resistance value, the resistance value is equal to or less than the resistance value,
Insulation resistance measurement, wherein when the first and second load resistors have different resistance values, the resistance value is less than one of the resistance values of the first and second load resistors. apparatus. The insulation resistance measuring apparatus according to claim 1, further comprising a calculation unit that calculates the insulation resistance _RL based on the following formula (1-1).
R _L ≧ (R _D3 × I _a −R _D2 × I ₂ −R _D1 × I ₁ ) / (I ₁ + I ₂ ) (1-1)
Where I ₁ is the current value in the first load resistance when the positive electrode of the power generation unit is connected to the ground, and I _{2 is} the second load resistance when the negative electrode of the power generation unit is connected to the ground. Current value at _Ia : current value at the third load resistance in a state where the positive electrode and the negative electrode of the power generation unit are connected to each other, R _D1 : the first load resistance, R _D2 : the second load resistance, R _D3 : the third load resistance, R _L : the insulation resistance. The insulation resistance measuring apparatus according to claim 1, further comprising a calculation unit that calculates the position of the ground fault point based on the following equation (1-2).
V ₁ : V ₂ = I ₁ × (R _D3 × I _a + I ₂ × (R _D1 −R _D2 )):
I ₂ × (R _D3 × I _a + I ₁ × (R _D2 −R _D1 )) (1-2)
Where V _{1 is} the voltage value from the ground fault point to the positive electrode of the power generation unit, V _{2 is} the voltage value from the ground fault point to the negative electrode of the power generation unit, and I _{1 is} the state where the positive electrode of the power generation unit is connected to the ground. Current value in the first load resistance, I ₂ : current value in the _second load resistance with the negative electrode of the power generation unit connected to the ground, R _D1 : the first load resistance, R _D2 : the first 2 load resistance, R _D3 : the third load resistance.   The said 1st, 2nd and 3rd load resistance has the mutually same predetermined resistance value, The insulation resistance measuring apparatus as described in any one of Claims 1-3 characterized by the above-mentioned. The measuring unit is
A voltmeter having a positive electrode and a negative electrode and measuring a voltage value of a resistance between the positive electrode and the negative electrode;
A first switching connection portion that connects the positive electrode of the voltmeter in a switchable manner between the positive electrode of the power generation unit and the ground; and
A second switching connection portion that connects the negative electrode of the voltmeter in a switchable manner between the negative electrode of the power generation unit and the ground, and
The first, second and third load resistors are constituted by the resistance between the positive electrode and the negative electrode of the voltmeter,
The first measurement unit is configured to connect the negative electrode of the voltmeter to the ground by the second switching connection unit while connecting the positive electrode of the voltmeter to the positive electrode of the power generation unit by the first switching connection unit. , Measure the voltage value or current value in the resistor,
The second measurement unit is configured to connect the positive electrode of the voltmeter to the ground through the first switching connection unit and connect the negative electrode of the voltmeter to the negative electrode of the power generation unit through the second switching connection unit. , Measure the voltage value or current value in the resistor,
The third measuring unit connects the positive electrode of the voltmeter to the positive electrode of the power generation unit by the first switching connection unit, and connects the negative electrode of the voltmeter to the negative electrode of the power generation unit by the second switching connection unit. The insulation resistance measuring device according to any one of claims 2 to 4, wherein a voltage value or a current value in the resistor is measured in a state where the resistance is set.   An insulation resistance measuring method, comprising: measuring the insulation resistance in the power generation unit using the insulation resistance measuring device according to any one of claims 1 to 5.   The insulation resistance measuring device according to any one of claims 1 to 6 is used to measure the insulation resistance in the power generation unit, and when the measured insulation resistance is below a predetermined value, an alarm is issued. Characteristic insulation monitoring device.

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