JP2011252827A - Resistance value calculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp a decrease in a resistance value of an insulation resistance of a loading device during an operation of a power supply system.SOLUTION: A resistance value calculation device calculates resistance values of first and second insulation resistances of a loading device having the first insulation resistance between a positive line and an earth, and the second insulation resistance between a negative line and the earth. The resistance value calculation device has: a first potential difference measurement unit that measures a potential difference between both ends of a first ground resistance provided on a first ground line that connects the positive line and the earth; a second potential difference measurement unit that measures a potential difference between both ends of a second ground resistance provided on a second ground line that connects the negative line and the earth; a control unit that calculates resistance values of the first and second insulation resistances using a variable resistor provided on the first or second ground line, a resistance value before and after the variation of the variable resistor, potential difference measured by the first and second potential difference measurement units before and after the variation, and resistance values of the first and second ground resistances; and an output unit that outputs the calculated resistance values for notifying them to the outside.

Description

  The present invention relates to a resistance value calculation device that calculates a resistance value of an insulation resistance of a load device.

  The insulation resistance of the load device to which power is supplied from the power supply via the feeder line needs to have a sufficiently large resistance value (for example, about 1 MΩ) in order to prevent electric shock. The insulation resistance of the load device is a resistance between the power supply line in the load device and the ground.

  As described above, the insulation resistance of the load device needs to have a sufficiently large resistance value. However, if the resistance value decreases due to contamination of the substrate in the load device or accumulation of dust, the load Anyone who touches the device may get an electric shock.

  Therefore, it is necessary to grasp the decrease in the resistance value of the insulation resistance. An example of a method for realizing this will be described below.

  FIG. 2 is a diagram for explaining an example of a method for grasping the decrease in the resistance value of the insulation resistance.

  In FIG. 2, the ground resistor 41 is a resistor provided on the ground wire 71 that connects the positive electrode wire 61 and the ground. The ground resistor 42 is a resistor provided on a ground line 72 that connects the negative electrode line 62 and the ground.

  The load device 30 has insulation resistances 31 and 32. The insulation resistance 31 is a resistance between the positive electrode line 61 and the ground, and the insulation resistance 32 is a resistance between the negative electrode line 62 and the ground. The resistance value of the insulation resistance is, for example, about several tens of kΩ.

  In this method, the voltmeter 12 measures the potential difference across the ground resistor 41, and the voltmeter 13 measures the potential difference across the ground resistor 42. Here, the voltage measured by the voltmeter 13 is the product of the resistance value of the ground resistor 41 and the current flowing through the ground resistor 41. The voltage measured by the voltage 14 is the product of the resistance value of the ground resistor 42 and the current flowing through the ground resistor 42. Usually, since the resistance value of the insulation resistance is larger than that of the ground resistance, the current flowing through the insulation resistance is small, and the current flowing through the ground resistance 41 and the current flowing through the ground resistance 42 are the same. Therefore, the potential difference ratio between the potential difference measured by the voltmeter 12 and the potential difference measured by the voltmeter 13 is the resistance value ratio between the resistance value of the ground resistor 41 and the resistance value of the ground resistor 42.

  Here, for example, when one of the resistance value of the insulation resistance 31 and the resistance value of the insulation resistance 32 decreases, such as when the positive electrode wire 61 or the negative electrode wire 62 is grounded, a current flows through the insulation resistance whose resistance value has decreased. become. The current flowing through the insulation resistance forms a current path flowing through the ground resistance 41 or the ground resistance 42 via the ground line. For this reason, the current flowing through the ground resistor 41 and the current flowing through the ground resistor 42 are different, and the above-described potential difference ratio changes. Therefore, by monitoring the change in the potential difference ratio using the detector 100, it is possible to grasp any decrease in the resistance value of the insulation resistance 31 and the resistance value of the insulation resistance 32.

Japanese Patent No. 4142137

  However, when both the resistance value of the insulation resistance 31 and the resistance value of the insulation resistance 32 are reduced in the same way, the current flowing through the insulation resistance having the reduced resistance value increases, but the insulation resistance 31 and the insulation resistance 32 The same current flows and no current flows through the ground line. For this reason, the current flowing through the ground resistor 41 and the current flowing through the ground resistor 42 are the same. Therefore, since the above-described potential difference ratio does not change, it is impossible to grasp the decrease in the resistance values of the insulation resistors 31 and 32.

  Here, even when both the resistance value of the insulation resistance 31 and the resistance value of the insulation resistance 32 are lowered in the same manner, the resistance value of the insulation resistances 31 and 32 is lowered by removing the ground resistance 41 or the ground resistance 42. Can figure out.

  However, if the grounding resistance is removed, noise may be generated in the power supply system or the power supply potential may become unstable, and there is a problem that it cannot be performed during operation of the power supply system.

  An object of the present invention is to provide a resistance value calculation device that makes it possible to grasp a decrease in the resistance value of an insulation resistance of a load device during operation of a power feeding system.

In order to achieve the above object, a resistance value calculation apparatus according to the present invention includes a first insulation resistance between a positive line constituting a power supply line to which power is supplied and a ground, and a negative line constituting the power supply line. A resistance value calculation device for calculating a resistance value of the first and second insulation resistances of a load device having a second insulation resistance with respect to ground and notifying the calculated resistance value to the outside;
A first potential difference measuring unit for measuring a potential difference between both ends of a first grounding resistor provided on a first grounding line connecting the positive electrode line and the ground;
A second potential difference measuring unit for measuring a potential difference between both ends of a second grounding resistor provided on a second grounding line connecting the negative electrode line and the ground;
A variable resistor provided on the first or second ground line;
The resistance value of the variable resistor is changed, the resistance value before and after the change, the potential difference measured by the first and second potential difference measuring units before and after the change, and the first and second grounds A control unit that calculates a resistance value of the first and second insulation resistances using a resistance value of the resistor;
And an output unit that outputs to notify the resistance value calculated by the control unit to the outside.

  Since the present invention is configured as described above, it is possible to grasp a decrease in the resistance value of the insulation resistance of the load device during operation of the power feeding system.

It is a figure which shows the structure of one Embodiment of the electric power feeding system to which the resistance value calculation apparatus of this invention is applied. It is a figure for demonstrating an example of the method of grasping | ascertaining the fall of the resistance value of an insulation resistance.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an embodiment of a power feeding system to which a resistance value calculating apparatus of the present invention is applied.

  As shown in FIG. 1, the power supply system of the present embodiment includes a resistance value calculating device 10, a power source 20, and a load device 30 to which power is supplied from the power source 20 via a power supply line.

In FIG. 1, a grounding resistor 41, which is a first grounding resistor, is a resistor provided on a grounding wire 71, which is a first grounding wire that connects a positive electrode wire 61 that constitutes a feeder line and the ground. The grounding resistor 42 as the second grounding resistor is a resistor provided on the grounding wire 72 that is the second grounding wire that connects the negative electrode wire 62 that constitutes the feeder line and the ground. Hereinafter, the resistance value of the ground resistor 41 is denoted as R _1, and the resistance value of the ground resistor 42 is denoted as R ₂ .

The load device 30 includes an insulation resistance 31 that is a first insulation resistance and an insulation resistance 32 that is a second insulation resistance. The insulation resistance 31 is a resistance between the positive electrode line 61 and the ground, and the insulation resistance 32 is a resistance between the negative electrode line 62 and the ground. Hereinafter, the resistance value of the insulation resistor 31 is represented as R _3, and the resistance value of the insulation resistor 32 is represented as R ₄ .

  The resistance value calculating device 10 includes a variable resistor 11, a voltmeter 12 that is a first potential difference measuring unit, a voltmeter 13 that is a second potential difference measuring unit, a control unit 14, and an output unit 15. Yes.

  The variable resistor 11 is provided on the ground line 71 or the ground line 72. In the present embodiment, it is assumed that the variable resistor 11 is provided on the ground line 71 as shown in FIG. In FIG. 1, the variable resistor 11 is provided on the ground line 71 between the ground resistor 41 and the ground. However, the variable resistor 11 is disposed on the ground line 71 between the positive electrode 61 and the ground resistor 41. May be provided.

  The voltmeter 12 measures a potential difference between both ends of the ground resistor 41. Further, the voltmeter 13 measures a potential difference between both ends of the ground resistor 42.

The control unit 14 changes the resistance value of the variable resistor 11. Then, the control unit 14 uses the resistance value of the variable resistor 11 before and after the change, the potential difference measured by the voltmeters 12 and 13 before and after the change, and the resistance value of the ground resistors 41 and 42. Then, the resistance values R ₃ and R ₄ of the insulation resistors 31 and 32 are calculated. Details of the operation in which the control unit 14 calculates the resistance values R ₃ and R ₄ of the insulation resistors 31 and 32 will be described later.

The output unit 15 is, for example, an alarm device, and outputs an alarm when the resistance values R ₃ and R ₄ calculated by the control unit 14 are equal to or less than a predetermined resistance value. Note that the output unit 15 is not limited to outputting an alarm, and may have a function of performing output for notifying the resistance values R ₃ and R ₄ calculated by the control unit 14 to the outside. For example, the output unit 15 may include a screen and display the resistance values R ₃ and R ₄ calculated by the control unit 14 on the screen.

Hereinafter, an operation of calculating the resistance values R ₃ and R ₄ of the insulation resistances 31 and 32 in the resistance value calculating apparatus 10 configured as described above will be described.

First, the control unit 14 sets the resistance value of the variable resistor 11 to zero. Hereinafter, the resistance value (0) of the variable resistor 11 at this time is denoted as R ₅₁ .

Next, the control unit 14 acquires a potential difference between both ends of the grounding resistor 41 measured by the voltmeter 12. Hereinafter, the acquired potential difference is denoted as V ₁₁ . In addition, the control unit 14 acquires a potential difference between both ends of the ground resistance 42 measured by the voltmeter 13. Hereinafter, the acquired potential difference is denoted as V ₂₁ .

Next, the control unit 14 sets the resistance value of the variable resistor 11 to a predetermined resistance value other than zero. The predetermined resistance value other than 0 is, for example, a resistance value equal to or greater than that of the ground resistors 41 and 42. Hereinafter, the resistance value (predetermined resistance value other than 0) of the variable resistor 11 at this time is denoted as R ₅₂ .

Next, the control unit 14 acquires a potential difference between both ends of the grounding resistor 41 measured by the voltmeter 12. Hereinafter, the acquired potential difference is denoted as V ₁₂ . In addition, the control unit 14 acquires a potential difference between both ends of the ground resistance 42 measured by the voltmeter 13. Hereinafter, the potential difference acquired here is expressed as V ₂₂ .

Then, the control unit 14 calculates resistance values R ₃ and R ₄ of the insulation resistors 31 and 32.

As described above, the control unit 14 acquires the potential differences V ₁₁ and V ₂₁ measured by the voltmeters 12 and 13 when the resistance value of the variable resistor 11 is R ₅₁ (0). Further, the control unit 14 acquires the potential differences V ₁₂ and V ₂₂ measured by the voltmeters 12 and 13 when the resistance value of the variable resistor 11 is R ₅₂ (a predetermined value other than 0).

  Further, in the power supply system of the present embodiment, a closed circuit is formed by the positive electrode line 61, the negative electrode line 62, the ground resistors 41 and 42, the variable resistor 11, and the insulation resistors 31 and 32. Thus, the following expressions (1) and (2) are derived.

The above-described equations (1) and (2) indicate that the resistance values R ₅₁ and R ₅₂ before and after the change of the variable resistor 11 and the potential differences V ₁₁ and V ₁₂ measured by the voltmeters 12 and 13 before and after the change. This is a relational expression representing the relationship among V ₂₁ and V ₂₂ , the resistance values R ₁ and R _{2 of the} ground resistors 41 and 42, and the resistance values R ₃ and R ₄ of the insulation resistors 31 and 32.

In Equations (1) and (2), the only unknown values are the resistance values R ₃ and R ₄ of the insulation resistors 31 and 32. Therefore, by substituting the resistance values R ₁ , R ₂ , R ₅₁ , R ₅₂ and the potential differences V ₁₁ , V ₁₂ , V ₂₁ , V ₂₂ into the equations (1) and (2), the resistance of the insulation resistances 31 and 32 Values R ₃ and R ₄ can be calculated.

In order to calculate R ₃ and R ₄ more accurately, it is desirable to set the resistance values R ₁ and R ₂ of the ground resistors 41 and 42 to about the prescribed insulation resistance value in the load device 30. Specifically, in consideration of human safety, it is preferable to set R ₁ and R ₂ to about (feed voltage / 10 mA).

  Thus, in the present embodiment, the resistance value of the variable resistor 11 is changed, the resistance value before and after the change, the potential difference measured by the voltmeters 12 and 13 before and after the change, The resistance values of the insulation resistances 31 and 32 are calculated using the resistance value of 42. Then, the calculated resistance value is notified to the outside.

  Thereby, it becomes possible to grasp | ascertain the fall of the resistance value of the insulation resistances 31 and 32 of the load apparatus 30 during operation | movement of an electric power feeding system.

  When the power supply voltage is constant, even if only one of the voltmeter 12 or the voltmeter 13 can be obtained, the other voltage can be obtained, so that only one voltmeter may be used.

  Moreover, in this embodiment, the case where the fall of the resistance value of the insulation resistance of one load apparatus was grasped | ascertained was demonstrated as an example. However, even in a power feeding system in which power is supplied from a power source to a plurality of load devices by a current distribution device or the like, the resistance value of the insulation resistance of the plurality of load devices is reduced by using the method described in this embodiment. I can grasp that. In this case, the above-described two relational expressions may be derived by connecting a ground line to a place connected by the power source and the power supply line and providing a variable resistor on the ground line.

DESCRIPTION OF SYMBOLS 10 Resistance value calculation apparatus 11 Variable resistance 12, 13 Voltmeter 14 Control part 15 Output part 20 Power supply 30 Load apparatus 31, 32 Insulation resistance 41, 42 Ground resistance 61 Positive electrode line 62 Negative electrode line 71, 72 Ground line

Claims (3)

A load device having a first insulation resistance between a positive electrode line constituting a power supply line to which power is supplied and a ground, and a second insulation resistance between a negative electrode line constituting the power supply line and a ground. A resistance value calculating device that calculates resistance values of the first and second insulation resistors and notifies the calculated resistance values to the outside.
A first potential difference measuring unit for measuring a potential difference between both ends of a first grounding resistor provided on a first grounding line connecting the positive electrode line and the ground;
A second potential difference measuring unit for measuring a potential difference between both ends of a second grounding resistor provided on a second grounding line connecting the negative electrode line and the ground;
A variable resistor provided on the first or second ground line;
The resistance value of the variable resistor is changed, the resistance value before and after the change, the potential difference measured by the first and second potential difference measuring units before and after the change, and the first and second grounds A control unit that calculates a resistance value of the first and second insulation resistances using a resistance value of the resistor;
A resistance value calculating device comprising: an output unit configured to output to notify the resistance value calculated by the control unit to the outside. In the resistance value calculation apparatus according to claim 1,
The control unit includes a resistance value before and after the change, a potential difference measured by the first and second potential difference measurement units before and after the change, and a resistance value of the first and second ground resistors. In the two relational expressions representing the relationship between the resistance values of the first and second insulation resistances, the resistance values before and after the change and the first and second potential difference measuring units before and after the change A resistance value calculation device that calculates a resistance value of the first and second insulation resistors by substituting the measured potential difference and the resistance values of the first and second ground resistors. In the resistance value calculation apparatus according to claim 1 or 2,
The said output part is a resistance value calculation apparatus which outputs a warning, when the resistance value calculated in the said control part is below a predetermined resistance value.

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