JP4993727B2 - Leakage current measuring instrument - Google Patents

Description

  The present invention relates to a leakage current measuring instrument used, for example, for insulation inspection of a power line, and more particularly to a leakage current measuring instrument capable of displaying a leakage current of a distribution system as a vector.

A power supply line monitor that analyzes and evaluates the quality of a power distribution system by measuring the fundamental wave effective value, fundamental wave phase angle, leakage current, harmonics, and the like of the power distribution system is described in Patent Document 1, for example.
FIG. 4 is a block diagram in the case where the power line monitor described in Patent Document 1 is used as the leakage current measuring instrument 10A for a single-phase three-wire distribution system.

In FIG. 4, a, b and N are single-phase three-wire electric circuits, R _a and R _b are ground resistances of the electric circuits a and b, C _a and C _b are ground capacitances of the electric circuits a and b, and 11 is , line voltage V _a or the reference voltage (acquired voltage both line voltage V _b leakage during current measurement between the path b and the grounding path _N, between the ground path N by path a and B type grounding is input as a means), a voltage input unit for performing the level adjustment, ZCT synthetic leakage current (effective leakage current is connected to a ground path N, the vector sum of the reactive leakage current) zero-phase detecting an I _g strange Nagareki, 12 leakage current input section for performing the level adjustment is entered synthesized leakage current I _g, 2a, 2b is a / D conversion circuit 3, the calculator for calculating the effective leakage current, disabling leakage current, etc. (CPU) 4 is the input of the arithmetic unit 3 collected via the A / D conversion circuits 2a and 2b Memory for storing a over data and calculation results, 5 sin wave reference waveform data memory for reference waveform data is stored in the cos wave, and 6 a display unit for numerically displaying the calculation result by the calculating section 3.
Here, the reference waveform data has the same period as the input voltage waveform to the voltage input unit 11, and is data created in advance on the table with the same resolution as the A / D conversion circuits 2a and 2b.

Next, FIG. 5 is a vector diagram showing the principle for _{obtaining the} effective leakage current I _gr and the reactive leakage current I _gc with the configuration of FIG. The effective leakage current I _gr is a vector sum of the leakage currents I _gra and I _grb flowing through the ground resistances R _a and R _b in FIG. 4, respectively, and the reactive leakage current I _gc flows through the ground capacitances C _a and C _b , respectively. _{This is} a vector sum of leakage currents I _gca and I _gcb .

Since path a, b of the insulation failure is rarely occur simultaneously, ground resistance R _a, the effective leakage current I _gr by R _b is ground resistance R _a, the leakage current value according to either of R _b That is, it may be considered that I _gr = I _gra or I _gr = I _grb . Since the electric _circuits a and b are in a reverse phase relationship, I _gra and I _grb have opposite polarities, and I _gca and I _gcb also have opposite polarities.
With reference to FIG. 5, a method for measuring the effective leakage current I _gr and the reactive leakage current I _gc according to the prior art will be briefly described below.

Now, assuming that the acquired voltage is V _a , the calculation unit 3 in FIG. 4 first calculates the voltage V _{a for a} predetermined wave number fetched from the voltage input unit 11, sin wave data and cos wave data in the reference waveform data memory 5, and perform product-sum operation using a first integrated value of the voltage V _a, the second cumulative value determined. Similarly, the arithmetic unit 3 performs product-sum calculation using the sin wave data and the synthetic leakage current I _g of predetermined wave number of captured from the leak current input 12, and a cos wave data, the synthetic leakage current I _g A first integrated value and a second integrated value are obtained.
Here, since the calculation method of each integrated value is not the gist of the present invention, the description thereof is omitted.

Next, a first integrated value of these voltages V _a and synthetic leakage current I _g, by using the second integrated value, as shown in FIG. 5, the phase angle of the voltage V _a and synthetic leakage current I _g to the reference waveform θ ₁ and θ ₂ are obtained, respectively. Then, the first integrated value of the combined leakage current I _g, the second integrated value and by using the phase angle theta _2, determine the fundamental component I _g of synthetic leakage current I _{g (1).}
When not only the effective leakage current I _gr and the reactive leakage current I _gc but also the insulation resistance is obtained, in addition to the above, the first integrated value, the second integrated value, and the phase angle θ ₁ of the voltage V _a are set. Using this, the fundamental wave component V _ab (1) of the voltage V _a is obtained.

Further, the phase difference between the theta ₁ and theta _2, that is, determines a phase angle theta synthetic leakage current I _g to the acquisition voltage V _a, determines path a, both from leakage current b is generated. That is, it can be determined that leakage current is generated from the electric circuit a when | θ | <90 ° and from the electric circuit b when | θ |> 90 °.

Therefore, invalid leakage current I _gc by effective leakage current I _gr and earth capacitance by ground resistors are included in the combined leakage current I _g can be determined by Equation 1, Equation 2.
[Formula 1]
I _gr = I _g (1) cos θ
[Formula 2]
I _gc = I _g (1) sin θ

4 obtains the effective leakage current I _gr and the reactive leakage current I _gc by the calculations of the above formulas 1 and 2, and these measured values are numerically displayed on the display unit 6 together with the combined leakage current _Ig and the phase angle θ. it's shown. Further, a leakage current waveform is also displayed on the display unit 6 as necessary.

JP 2006-234402 A (Claims 7 and 8, paragraphs [0058] to [0069], FIG. 4 etc.)

However, for the measuring person, which of the effective leakage current and reactive leakage current and that either dominant among synthesized leakage current I _g, or margin for the specified value of the leakage current (control value) is much like There is a demand for intuitively and visually grasping the above, and the conventional leakage current measuring device cannot meet these demands.

  On the other hand, a display device that displays the current, voltage, phase angle, and the like of the system line as a vector is known as, for example, Japanese Patent Application Laid-Open No. 7-318594 “Measured Value Vector Display Device”. As a function of the measuring instrument, there has not yet been provided an intuitive and visual grasp of the component of the composite leakage current.

  Therefore, a problem to be solved by the present invention is to provide a leakage current measuring instrument that makes it easy to analyze leakage current and thereby grasp the state of a distribution system by displaying each component of the combined leakage current and other measured values as vectors. .

In order to solve the above-mentioned problem, the invention according to claim 1 detects a combined leakage current flowing between the distribution system and the grounding point;
Means for detecting a line voltage of the distribution system as an acquired voltage;
A calculation unit that calculates a component of the combined leakage current using the phase angle between the acquired voltage and the combined leakage current, and the combined leakage current;
Display means for displaying the component of the combined leakage current calculated by the calculation means;
In the leakage current measuring instrument with
The calculation means generates display data for displaying at least the combined leakage current, and effective leakage current and reactive leakage current that are components thereof as vectors,
The display means displays the vector using the display data, and displays a preset value of the effective leakage current in the vector direction of the effective leakage current .

  In addition, as described in claim 2, the calculation unit generates display data for displaying the acquired voltage as a vector, and the display unit displays the acquired voltage together with the combined leakage current, the effective leakage current, and the invalid leakage current. It is desirable to display the vector.

According to a third aspect of the present invention, in the leakage current measuring instrument according to the first or second aspect, various quantities displayed as vectors on the display means are numerically displayed together with vectors .

  According to the present invention, the effective leakage current and the reactive leakage current that are components of the combined leakage current are displayed as vectors, so that the measurer can intuitively and visually grasp the insulation deterioration state of the distribution system. . Moreover, if the specified value of the leakage current is also displayed, it becomes easy to grasp the margin of leakage current, which can be used for grasping the state of the power distribution system and maintenance inspection work.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a leakage current measuring instrument 10 according to the embodiment, and is substantially the same as FIG. 4 except for the functions of the calculation unit 7 and the display unit 8.

In FIG. 1, as described above, a, b, and N are single-phase three-wire electric circuits, R _a and R _b are ground resistances of the electric circuits a and b, and C _a and C _b are electrostatic capacitances of the electric circuits a and b. Capacitance 11 is a voltage input unit for adjusting the level of the line voltage between the electric circuits a and N or between the electric circuits b and N as an acquired voltage, and ZCT is connected to a grounding electric circuit N with B type grounding. zero-phase current transformer for detecting a has been synthesized leakage current I _g, 12 leakage current input section for performing the level adjustment is entered synthesized leakage current I _g, 2a, 2b is a / D conversion circuit, 7 A calculation unit (CPU) for calculating effective leakage current I _gr , reactive leakage current I _{gc and the} like and displaying these measured values in vector as will be described later, 4 is collected via A / D conversion circuits 2a and 2b A memory for storing the input data and calculation results of the calculated calculation unit 7, 5 is a sin wave, co Reference waveform data memory for reference waveform data are stored in the wave, 8 is a liquid crystal display, display unit comprising a plasma display or the like vector representation of the measured values, a numerical display or the like performed on the basis of the output of the arithmetic unit 7.

FIG. 2 is a functional block diagram showing the configuration of the arithmetic unit 7.
The calculation unit 7 is connected to the A / D conversion circuits 2a and 2b, the memory 4, and the reference waveform data memory 5, and the acquired voltage, the combined leakage current I _g , and the effective leakage current I _gr input to the voltage input unit 11 are connected. (I _gra or I _grb ), reactive leakage current I _gc , phase angle θ, etc., a measurement value calculation unit 71, a coordinate calculation unit 72 that calculates coordinates for vector display of these measurement values, and the above measurement The display control unit 73 generates display data on the display unit 8 based on the value and the coordinate calculation value.

The operation of this embodiment will be described below.
Now, the acquisition voltage is assumed to be V _a, the measurement value calculating unit 71 of FIG. 2, according to the methods described in the prior art, the phase angle theta, effective with the acquisition voltage V _a and the synthesis leakage current I _g The leakage current I _gr and the reactive leakage current I _gc are calculated. At this time, as described above, based on the magnitude of θ, it can also be detected whether the effective leakage current I _gr is I _gra by the electric circuit a or I _grb by the electric circuit b. Here, it is assumed that I _gr = I _gra .
Further, the specified value (management value) of the effective leakage current I _gr stored in advance in the memory 4 is input to the measured value calculation unit 71.

These measured values I _g , V _a , V _b (assuming they are opposite in phase to V _a and have the same magnitude), θ, I _gra , I _gc, and the specified values are sent to the display control unit 73 in FIG. And is input to the coordinate calculation unit 72.
The coordinate calculation unit 72 calculates coordinates for displaying I _g , V _a , V _b , I _gra , and I _gc as vectors, and coordinates for displaying the specified value at a position in the same direction as I _gra. These coordinate data are output to the display control unit 73.

In the display control unit 73 of FIG. 2, using the output data of the measurement value calculation unit 71 and the coordinate data from the coordinate calculation unit 72, vector display data and numerical display data of each measurement value and specified value are created, Output to the display unit 8.

FIG. 3 shows a display screen 8 a of the display unit 8, and this display screen 8 a has a vector display unit 81, specified value display units 82 a and 82 b, and a numerical value display unit 83.
In the vector display portion 81, I _g , V _a , V _b , I _gra , and I _gc are displayed as vectors, and the phase angle θ is also displayed, and are defined in the same direction and in the opposite direction to the vector I _gra. In the value display portions 82a and 82b, the position of the specified value (for example, 5 mA) is displayed together with the characters “specified value 5 mA” at the same ratio as the vector I _gra . In addition to or in place of the display of the specified value,% display of the value of I _gra (I _gr ) with respect to the specified value may be performed. Displaying the specified value together in this way makes it easy to grasp the margin of leakage current.

In addition, the measured values I _g , I _gra , I _grb , I _gc , and θ are displayed as numerical values in a numerical value display portion 83 disposed below the vector display portion 81. Although not shown, the measured value of the acquired voltage V _a or V _b may be numerically displayed simultaneously.
Furthermore, the leakage current waveform may be displayed simultaneously as necessary.

According to this embodiment as described above, the effective leakage current I _gr is a component of the composite leakage current I _g, so disabling leakage current I _gc is the vector on the display screen 8a, the measurer of these components It is possible to intuitively and visually grasp the insulation deterioration state of the power distribution system including which is dominant. Further, the display of the specified values by the specified value display units 82a and 82b facilitates the grasp of the leakage current margin, which can be used for grasping the status of the power distribution system and maintenance inspection work.

  In the above embodiment, the leakage current measuring device for the single-phase three-wire distribution system has been described. However, the present invention is a single-phase two-wire system, a three-phase three-wire system, and a three-phase four-wire distribution system. The present invention can also be applied to a leakage current measuring device targeting the above.

It is a block diagram which shows embodiment of this invention. It is a functional block diagram of the calculating part in FIG. It is a figure which shows the display screen of the display part in FIG. It is a block diagram which shows a prior art. It is a vector diagram which shows the principle which calculates | requires a leakage current by a prior art.

Explanation of symbols

10: Leakage current measuring instrument 11: Voltage input unit 12: Leakage current input unit 2a, 2b: A / D conversion circuit 4: Memory 5: Reference waveform data memory 7: Calculation unit 71: Measurement value calculation unit 72: Coordinate calculation unit 73: Display control unit 8: Display unit 8a: Display screen 81: Vector display unit 82a, 82b: Specified value display unit 83: Numerical value display unit ZCT: Zero-phase current transformer

Claims (3)

Means for detecting a composite leakage current flowing between the distribution system and the ground point;
Means for detecting a line voltage of the distribution system as an acquired voltage;
A calculation unit that calculates a component of the combined leakage current using the phase angle between the acquired voltage and the combined leakage current, and the combined leakage current;
Display means for displaying the component of the combined leakage current calculated by the calculation means;
In the leakage current measuring instrument with
The calculation means generates display data for displaying at least the combined leakage current, and effective leakage current and reactive leakage current that are components thereof as vectors,
The display means displays a vector using the display data, and displays a preset value of the effective leakage current in the vector direction of the effective leakage current . In the leakage current measuring instrument according to claim 1,
The calculation means generates display data for displaying the acquired voltage as a vector, and causes the display means to display the acquired voltage together with the combined leakage current, effective leakage current and reactive leakage current as a vector. Leakage current measuring instrument. In the leakage current measuring device according to claim 1 or 2,
A leakage current measuring instrument characterized in that various quantities displayed as vectors on the display means are numerically displayed together with vectors .

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