JP2019105483A - Megohmmeter and measuring method of insulation resistance - Google Patents

Abstract

To provide a megohmmeter which shows the waiting time until completion of charging when a measurement object is a capacitive load, and a measuring method of insulation resistance.SOLUTION: A megohmmeter comprises a power source section which inputs an examination voltage to a measurement object, a voltage detection section which detects a voltage value input to the measurement object as an input voltage, a current detection section which detects current flowing to the measurement object when the examination voltage is input, and a control section which calculates a measurement value of insulation resistance based on the voltage value of the input voltage and a value of the current, and the control section calculates and displays the time until completion of charging from the input voltage being input to the measurement object and the flowing current value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulation resistance meter and a method of measuring the same.

The insulation resistance meter applies a test voltage to the object to be measured, and obtains the resistance value of the object to be measured based on the applied test voltage and the flowing current.
An insulation resistance meter is used to measure the insulation resistance of high voltage cables, transformers and motors. In the measurement, a test voltage is applied to the measurement target, and the resistance value of the measurement target is obtained based on the applied test voltage and the flowing current.
In the measurement, when start of measurement is instructed, a test voltage of direct current is applied to the measurement object from the insulation resistance meter, and the test voltage applied to the measurement object and the current value flowing to the measurement object are measured to calculate resistance value. it's shown.

Japanese Patent Application Publication No. 2006-300717

If the object to be measured is capacitive, it starts from charging the object to be measured with a constant current, and the measurement value is stabilized when charging is completed, so that the measured value is displayed or stored after the measurement value is stabilized. ing.
The capacitance value of the object to be measured varies depending on the object to be measured, and therefore, the time until charging is completed and the measured value is stabilized varies depending on the object of measurement. For example, even if the object to be measured is a high voltage cable, the capacity value changes depending on the thickness, the insulator, and the length, so the charging time is not fixed.
As described above, even if an insulation resistance meter is connected to the object to be measured to measure the insulation resistance, there is a problem that the measurer can not know how long it takes to stabilize the measured value.
There is also a technology in which the insulation resistance value is determined and displayed uniformly by setting a standard of how many minutes elapses uniformly because the time for completion of charging is not known, but this leaves a problem in measurement accuracy.

  The present invention solves the above problems, and an object of the present invention is to provide an insulation resistance meter and a measurement method thereof that display how much it takes to complete charging to a measurer and eliminate frustration during measurement. I assume.

  In order to solve the above problems, according to a first aspect of the present invention, there is provided a power supply unit for applying a test voltage to a measurement target, and a voltage detection unit for detecting a voltage value of the test voltage applied to the measurement target as an applied voltage. And a current detection unit that detects the current flowing to the measurement target when the test voltage is applied, and a calculation unit that calculates the measured value of the insulation resistance based on the voltage value of the applied voltage and the current value of the detected current The calculation unit includes means for calculating the capacity of the object to be measured after the start of application of the test voltage and displaying the time until the charging of the object to be measured is completed.

  Further, according to the present invention, the computing unit further comprises: applying a constant current value, an applied voltage value after a first predetermined time from the start of application of the test voltage, and an applied voltage value after a second predetermined time It is preferable to calculate the capacity of the object to be measured and calculate the time until the charging is completed.

  Further, in the present invention, it is preferable that the operation unit increases the number of times of average processing of the measured value of the insulation resistance after charging is completed.

  According to another aspect of the present invention, a power supply unit applying a test voltage to a measurement target, a voltage detection unit detecting a voltage value of the test voltage applied to the measurement target as an applied voltage, and a test voltage Measurement of an insulation resistance meter including a current detection unit that detects the current flowing to the measurement target, and a calculation unit that calculates the measured value of the insulation resistance based on the voltage value of the applied voltage and the current value of the detected current The method is characterized in that the operation unit executes the step of calculating the capacity of the object to be measured after the start of application of the test voltage and displaying the time until the charging of the object to be measured is completed.

  When the start of measurement is instructed, the time until the completion of charging is displayed, eliminating the trouble of the measurer who does not know the time until the measurement value stabilizes.

It is a figure which shows embodiment of this invention, and is a figure which shows the structure of an insulation resistance meter. It is a figure which shows the relationship between the elapsed time of charge to a measuring object, and an applied voltage. It is a flow chart explaining operation of an insulation resistance meter. 6 illustrates an example of display of insulation resistance value and waiting time displayed on the display unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of measurement of insulation resistance by an insulation resistance meter according to an embodiment of the present invention.
The insulation resistance meter 1 of the present embodiment includes a power supply unit 2, a voltage detection unit 3, a current detection unit 4, an A / D conversion unit 5, a control unit 6, an operation unit 7, a storage unit 8, and a display unit 9. The insulation resistance value R of the measurement object 11 can be measured.

  Under the control of the control unit 6, the power supply unit 2 generates a predetermined test voltage (for example, several kV) V to be applied to the measurement target 11. Further, the power supply unit 2 is configured as a constant voltage source provided with an output current limiting function. Therefore, when the measurement target 11 is a resistive load, the power supply unit 2 continues to apply the applied voltage Vv to the measurement target 11. On the other hand, when the object to be measured 11 is a capacitive load, the power supply unit 2 operates the output current limiting function due to the fact that a large current equal to or more than the specified value does not flow with the predetermined test voltage. Functions as a constant current source and continues a constant current to the object 11 until the voltage across the object 11 reaches a voltage close to the test voltage, ie, the capacitance of the object is fully charged. Supply.

  The voltage detection unit 3 detects and outputs an applied voltage Vv output from the power supply unit 3 and applied to the measurement object 11 as a voltage applied to both ends of the measurement object 11. In this case, although the voltage detection unit 3 can also detect the voltage at both ends of the measurement object 11 and output it to the A / D conversion unit 5, the resistance value of the lead wire is sufficiently lower than the resistance value of the measurement object 11 In this case, the voltage at the output end of the power supply unit 2 can be equivalently detected as the voltage across the object 11 to be measured. Moreover, the measuring method which measures the voltage of the both ends of the measuring object 11 is not specifically limited. Alternatively, a configuration may be employed in which the applied voltage applied by the power supply unit 2 is detected as the voltage Vv applied to both ends of the measurement target 11 and is output to the control unit 6. In addition, the current detection unit 4 has an I / V conversion function, detects a current flowing to the measurement target 11 at the time of application of the test voltage, and converts it into a voltage Vi and outputs it. The A / D conversion unit 5 samples the applied voltage Vv and the voltage Vi at a predetermined cycle, converts it into voltage data Dv and current data Di, and outputs the voltage data Dv and current data Di to the control unit 6.

The control unit 6 controls the respective components of the insulation resistance meter 1 based on the operation contents of the operation unit 7, measures the elapsed time from the start of application of the test voltage, and measures the insulation resistance value R of the measurement object 11. Calculation processing and display processing of the calculated insulation resistance value R are executed. The operation unit 7 is an operation button method, a touch panel method, or the like, and outputs an instruction signal according to the operation content of the insulation resistance meter to the control unit 6.
The storage unit 8 stores the data on the applied voltage V _v for each elapsed time T from the start of application of the test voltage to the measurement target 11. Based on the data stored in the storage unit 8, the calculation means of the control unit 6 calculates the insulation resistance value of the measurement object 11, and calculates the capacity of the measurement object 11 and the time until the charging completion.
The display unit 9 is a display device made of liquid crystal, organic EL or the like, and displays the measured value of insulation resistance, waiting time for completion of charging, information necessary for measurement operation and the like.

Next, with reference to FIG. 2, the calculation of the charge completion time of the measuring object in the present embodiment will be described. Figure 2, along with the start of the measurement by applying a test voltage, the charging is started, and represents a state in which the applied voltage V _v is increased with the lapse of time based on the measured capacitance.
Here, when the measurement is started, a DC voltage is output from the power supply unit 2, and a test voltage is applied to the measurement target 11. When the measurement target 11 is capacitive, the constant voltage is not applied immediately after the start of the measurement, but the constant current is applied, and the applied voltage gradually increases.

Here, after the start of measurement, based on the data of the applied voltage V ₁ when t ₁ time has elapsed while applying a constant current, and the applied voltage V ₂ when t ₂ time has elapsed, 11 Calculate the volume of The capacity of the measurement target 11 can be calculated by the following equation.
t = {C × (V ₂ −V ₁ )} / I
t: time from t ₁ to t ₂ C: capacity V ₁ : charge voltage at ₁ h (test voltage), V ₂ : charge voltage at t ₂ (test voltage) I: constant current value A / D conversion Since the sampling cycle in this section is known, t is known, and the constant current value is also known, and the capacity of the object to be measured can be calculated. It is possible to ask for

Hereinafter, the measurement operation of the insulation resistance will be described with reference to the flowchart of FIG.
When start of measurement is instructed, application of a test voltage is started from the power supply unit 2 (step S11). When the object to be measured 11 is capacitive, a constant current is applied and charged gradually, and the applied voltage to be measured increases. In the control unit 6, the elapsed time measurement is started (step S12), the first, the first elapsed time t ₁ the voltage, elapsed time is measured (step S13). This data is stored in the storage unit 6. Then a second elapsed time t ₂ of the voltage, the elapsed time is measured and stored in the storage unit 8 (step S14). The calculation means of the control unit 6 calculates the capacitance value of the object to be measured from the data of the first elapsed time and the second elapsed time based on the constant current charging equation (step S15). Then, the time taken for charging is calculated based on the capacitance value to be measured and the applied voltage (step S16), and the charge completion time is displayed on the display unit 9 (step S17). Further, voltage measurement and current measurement are performed to calculate the insulation resistance value R (step S 28), and the calculated insulation resistance value R is displayed on the display unit 9. (Step S19).
The charge completion time is counted down with the elapsed time, the insulation resistance value R is calculated based on the measured voltage and current, and the insulation resistance value R is displayed (steps S17 to S29).

Since the insulation resistance value R is displayed while the charge completion time is counted down until the charge completion, the insulation resistance value R is displayed while the charge completion waiting time displayed is counted down with the passage of time. It will change. The measurement of the insulation resistance ends when the end of the measurement is instructed at the end.
FIG. 4 shows an example of the insulation resistance value R displayed on the display unit 9 and the waiting time. Since the voltage changes until the charging is completed, the displayed insulation resistance value changes.

Next, calculation processing of the insulation resistance value after completion of charging will be described.
In the calculation of the insulation resistance in the insulation resistance meter, a moving average of the measured values is taken and the average value is displayed. Because the measured voltage and current have fluctuation and instability, the calculated insulation resistance value is not output as it is, but is not displayed, and a moving average of the measured data is obtained to obtain the average value of the insulation resistance processed. Is displayed.

  In the present embodiment, as the charging is completed, the number of averaging processes, for example, the number of samplings to be averaged is increased. As described above, since the charging completion time is known, the number of data to be averaged is increased as the charging is completed. For example, when the number of data to be averaged is five before charging is completed, the number of data to be averaged is increased to 100 after charging is completed. In this way, the response to display is delayed, but the insulation resistance value displayed is free from fluctuations. Since the applied voltage to be applied and measured increases until charging is completed, the number of data to be averaged is reduced in this increasing process, and the insulation resistance value that changes momentarily is displayed. Do. It may be displayed without averaging. Since the measurer can recognize that the charging is not completed even with the changing insulation resistance value, there is an advantage that it can be recognized that the measurement will not end together with the display of the waiting time.

In the above description, the case of the capacitive load has been described, but in the case of the resistive load, since the test voltage reaches the specified test voltage immediately after the start of measurement, the waiting time is not displayed and the waiting time is 0. The value of the insulation resistance may be displayed. The capacity was calculated from the test voltage, which is the charging voltage when t ₁ time has elapsed from the start of measurement, and the test voltage when t ₂ time has elapsed, but it is further increased by three or four. It can also be determined from the test voltage to be

Reference Signs List 1 insulation resistance meter 2 power supply unit 3 voltage detection unit 4 current detection unit 5 A / D conversion unit 6 control unit 7 operation unit 8 storage unit 9 display unit 11 measurement target

Claims (4)

A power supply unit that applies a test voltage to the measurement target;
A voltage detection unit that detects a voltage value of the test voltage applied to the measurement object as an applied voltage;
A current detection unit that detects a current flowing to the measurement target when the test voltage is applied;
A calculation unit that calculates a measured value of the insulation resistance based on the voltage value of the applied voltage and the current value of the detected current;
The insulation resistance meter characterized in that the calculation unit calculates the capacity of the object to be measured after the start of application of the test voltage and displays the time until the charging of the object to be measured is completed. In the insulation resistance meter according to claim 1,
The calculation unit is based on a constant current value being applied, an applied voltage value after a first predetermined time has elapsed from the start of application of the test voltage, and an applied voltage value after a second predetermined time has elapsed. An insulation resistance meter characterized by calculating a capacity of the object to be measured and calculating a time until charging is completed. In the insulation resistance meter according to claim 1 or 2,
An insulation resistance meter characterized in that the calculation unit increases the average number of times of measurement of insulation resistance after completion of charging. A power supply unit that applies a test voltage to the measurement target;
A voltage detection unit that detects a voltage value of the test voltage applied to the measurement object as an applied voltage;
A current detection unit that detects a current flowing to the measurement target when the test voltage is applied;
A calculation unit that calculates a measured value of the insulation resistance based on the voltage value of the applied voltage and the current value of the detected current.
Performing a step of calculating the capacitance of the object to be measured after the start of the application of the test voltage and displaying the time until the charging of the object is completed; .

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