JP2013195093A - Electric leakage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly accurate electric leakage detector simple in configuration.SOLUTION: In order to obtain a resistance portion leakage current I0r using a zero-phase current sensor in three-phase three cable ways having one phase grounded, the output of the zero-phase current sensor before virtual electric leakage is added is measured, and the output of the zero-phase current sensor when the virtual electric leakage is added is measured. The resistance portion leakage current I0r is calculated from these measured values by a predetermined vector calculation. The vector calculation of the electric leakage detector is carried out by using an insertion parameter, a measurement parameter, and a formula (1). The measured value of the zero-phase current sensor is a value obtained when a measured value a of the zero-phase current sensor, virtual electric leakage b, and virtual electric leakage c are added.

Description

  The present invention relates to a leakage detector having a simple configuration, and more particularly to a leakage detector having a high accuracy and a simple configuration.

Conventionally, an earth leakage detector that is simple and inexpensive is disclosed in, for example, Japanese Patent No. 3405407 (Patent Document 1). According to Patent Document 1, in a three-phase circuit in which one phase is grounded, a zero-phase current sensor that measures a zero-phase current i ₀ , and a phase having a phase difference of 90 ° with a non-grounded two-phase line voltage and means for generating a decision signal i _d, making the vectors i _x and i _y the measured zero-phase current i ₀ and the phase decision signal i _d vectorially adding and subtracting to the zero-phase current sensor, An earth leakage detector is disclosed that performs a predetermined calculation based on this and outputs a value of the resistive ground fault current i _gr .

No. 3405407 (Claim 2 etc.)

  A simple leakage detector having a conventional configuration is configured as described above.

However, in the conventional earth leakage detector device, a phase decision signal i _d having a phase difference of the line voltage of the 2-phase and 90 ° ungrounded had to be generated. There is a problem that it is difficult to accurately generate a phase difference of 90 ° and an error becomes large. In addition, two vector operations of addition and subtraction are required, and it is necessary to individually generate the phase determination signal i _d for the calculation, and there is a problem that an error also occurs at this time.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly accurate leakage detector with a simple configuration.

  The leakage detector according to the present invention is a leakage detector for obtaining a resistance leakage current I0r using a zero-phase current sensor in a three-phase three-wire circuit in which one phase is grounded. The earth leakage detector is a virtual earth leakage adding means for adding virtual earth leakage, the measured value of the zero phase current sensor, the measured value of the zero phase current sensor when the virtual earth leakage is added, and the vector calculation of the virtual earth leakage. Thus, the resistance leakage current I0r is obtained by a predetermined vector calculation.

  Preferably, the vector operation performs only vector addition.

  More preferably, the virtual leakage adding means for adding a virtual leakage adds an apparent virtual leakage to the zero-phase current sensor.

  The vector operation is preferably performed using the following a, b, and c parameters and Equation (1).

  However, a = measured value of the zero phase current sensor, b = measured value of the zero phase current sensor when the virtual leakage is added, and c = the virtual leakage.

  The parameter b is inserted by a predetermined insertion means, and the insertion means may be a resistance connection circuit or a constant current circuit.

  The virtual leakage adding means for adding a virtual leakage may add an apparent virtual leakage on an separately prepared internal circuit.

  In this case, the leakage detector has added a virtual leakage adding means for adding a virtual leakage, a measured value of a zero-phase current sensor when a virtual leakage is not added by the virtual leakage adding means, and a virtual leakage. The measured value of the zero phase current sensor and the virtual leakage may be measured simultaneously.

  Furthermore, the above vector calculation may be performed using the following parameters a, b, and c and equation (2).

  However, a = measured value of the zero-phase current sensor, b = virtual leakage, c = measured value synthesized by the measured value of the zero-phase current sensor and the virtual leakage.

  In another aspect of the present invention, the leakage detector determines a resistance leakage current I0r using a zero-phase current sensor in a three-phase three-wire circuit in which one phase is grounded. The leakage detector includes a measured value of the zero-phase current sensor, a zero-crossing point of the reference voltage, and a frequency thereof, a virtual leakage generation means for generating a virtual leakage based on the measured value, a zero-phase current sensor The resistance leakage current I0r is obtained by a predetermined vector calculation by vector calculation of each value obtained by combining the measured value and the value generated by the virtual leakage generation means.

  Preferably, the vector operation performs only vector addition.

  The above vector calculation may be performed using the following parameters a, b, and c and Equation (3).

  However, a = measured value of the zero-phase current sensor, b = virtual leakage, c = measured value of the zero-phase current sensor and a value generated by the virtual leakage generation means.

  The parameter b may be inserted by predetermined insertion means, the insertion means may be prepared by software, and the parameter c may be synthesized by software.

  In the present invention, the leakage detector adds a resistance leakage current I0r, an apparent virtual leakage current to the zero-phase current sensor, and does not add a virtual leakage current in a three-phase three circuit with one phase grounded. The measured value of the zero-phase current sensor when the virtual leakage is detected, the measured value of the zero-phase current sensor when the virtual leakage is added, and the vector calculation of the vector shift amount due to the addition of the virtual leakage Obtained by calculation.

  Since the resistance leakage current I0r required for leakage detection is obtained by vector calculation without using the phase of each phase, it is possible to prevent the occurrence of errors in phase detection as in the prior art.

  As a result, it is possible to provide a highly accurate leakage detector with a simple configuration.

It is a circuit diagram when the R phase and the T phase leak in the three-phase three-wire Δ connection. It is the figure which represented FIG. 1 by the vector diagram. It is a vector diagram based on Vrs. It is a vector diagram of I0 on the basis of I0r_R. It is a vector diagram of I0 on the basis of I0c_R. It is a leakage circuit diagram at the time of virtual resistance leakage current injection. It is a vector diagram at the time of virtual resistance leakage current injection. It is a vector diagram of I0 and I0_R1 with reference to I0r_R. It is a figure which shows the triangle of I0, I0_R1, and I0r_R1. It is a figure which shows the procedure which calculates | requires phase angle (theta). It is a circuit diagram of the I0r injection system of the first embodiment. It is a block diagram of 2nd Example. It is a block diagram of 3rd Example. It is a figure for demonstrating 4th Example. It is a figure for demonstrating 4th Example. It is a figure for demonstrating 4th Example.

  First, the principle of obtaining the resistance leakage current I0r in the three-phase three-wire Δ connection according to the present invention will be described. Here, it is assumed that the capacitance between each circuit is grounded.

  FIG. 1 shows a circuit 10 in the case where the R phase and the T phase are leaked in a three-phase three-wire Δ connection in which the S phase is grounded. Referring to FIG. 1, resistance leakage current I0r is monitored by I0r leakage monitoring device 10a. FIG. 2 is a summary of the vector diagrams of the leakage current of each voltage, R phase and T phase in FIG.

  Where I0r_R is the R-phase resistance leakage current, I0c_R is the R-phase capacitance leakage current, I0_R is the R-phase leakage current (I0), and I0r_T is the T-phase resistance leakage current. , I0c_T is the T-phase capacitance leakage current, I0_T is the T-phase leakage current (I0), and I0 is the combined R-phase and T-phase leakage current (I0).

  Next, how to obtain I0r will be described. First, a voltage phase that is a reference for calculating I0r is set. I0r is calculated using the combined leakage current I0 of the R phase and the T phase and the phase difference θ from this reference voltage phase. Here, Vrs is used as a reference, but any phase may be used as a reference. For easy understanding, when FIG. 2 is rotated by 240 ° to the vector diagram based on Vrs, FIG. 3 is obtained.

  First, an I0 vector based on I0r_R is obtained. I0 calculated by the ZCT 11 is composed of the vector components shown in FIGS. 4 and 5, and the following equation is established from I0 and the phase difference θ.

  First, when I0r_R is used as a reference, the following formula is established as I0 × sin θ with reference to FIG.

  Note that even if the value of I0r_R is changed, the above value (I0sinθ) does not change.

  Next, a case where I0c_R is used as a reference will be described.

  Referring to FIG. 5, the following equation holds for I0 cos θ.

  Note that the value (I0cos θ) does not change even if the value of I0c_R is changed. In addition, since the electrostatic capacitance between each circuit is considered to be balanced, if I0c_T = I0c_R, from Equation (1) and Equation (2),

となり、式(3)をI0c_Rについて解くと、

And solving equation (3) for I0c_R,

が得られ、式(4)に式(5)を代入すると、

And substituting equation (5) into equation (4),

となり、I0r=I0r_R+I0r_Tなので、

Since I0r = I0r_R + I0r_T,

が成り立つ。

Holds.

  From the above, if the phase angle θ between I0 and I0-Vrs is known, I0r can be calculated.

  Next, the leakage circuit 20 at the time of injecting the virtual resistance leakage current when the device 21 provided with the known I0r_R1 (virtual resistance leakage current) having the same phase as Vrs is injected into the ZCT 11 in the circuit of FIG. As shown in FIG. Here, the device 21 operates as virtual leakage adding means and insertion means.

  Here, the right arrow and the left arrow shown in FIG. 1 are also shown.

  Here, if I0 after injection of I0r_R1 is set to I0_R1, I0_R1 moves in vector from I0 by I0r_R1 in parallel as shown in FIG.

  If FIG. 7 is represented by a vector exploded view as shown in FIGS. 5 and 6 in the previous section for easy understanding, FIG. 8 is obtained. From FIG. 8, a triangle is formed with I0, I0_R1, and I0r_R1, and the angles are set to α, β, and γ, respectively. For simplicity, I0 = a, I0r_R1 = b, and I0_R1 = c. Then, as shown in FIG.

  If the three sides are known from the triangular cosine theorem in FIG.

よって、以下により、角度も求めることかできる。

Therefore, the angle can also be obtained by the following.

  Here, Acos θ is an arc cosine.

  If the phase angle θ shown in FIG. 8 is obtained, I0r can be obtained using the following principle equation (1). Therefore, the phase angle θ is calculated from FIG.

  Next, a specific calculation method will be described. In FIG. 9, a diagram in which a line is drawn in parallel from I0 to Vrs is shown in FIG. Here, I0 = a, I0r_R1 = b, and I0_R1 = c.

  From FIG. 10, θ can be obtained by θ = 180 ° −γ (12).

  Next, a method for measuring I0r without obtaining the phase angle θ will be described.

  When equation (11) is applied to principle equation (1),

となる。

It becomes.

  From the triangle formula (trigonometric function of complementary angle and complementary angle),

のため、式(13)に式(14),(15)を代入すると、

Therefore, when substituting (14) and (15) into (13),

となる。

It becomes.

  Here, according to the triangle formula (trigonometric correlation)

が成り立つため、

Because

が成り立つ。
式(18)を式(16)へ代入すると、

Holds.
Substituting equation (18) into equation (16),

式(19)に式(8)を代入すると、

Substituting equation (8) into equation (19),

  However, I0 = a, I0r_R1 = b, and I0_R1 = c.

  From the above, by injecting known I0r_R1 and measuring I0 and I0_R1, I0r can be calculated without measuring the phase angle θ.

  As described above, since I0r can be calculated without measuring the phase angle θ, a circuit for measuring the phase angle θ becomes unnecessary. Also, the measurement circuit can be shared by measuring I0_R1 into which I0r_R1 has been injected with the same circuit as I0.

  Next, an embodiment of the I0r circuit for injecting the virtual resistance leakage current will be described.

(1) First Embodiment The first embodiment is a resistance connection method. A specific circuit example is shown in FIG. Referring to FIG. 11, device 21 for injecting I0r includes SW1 for switching whether or not to inject and resistor R6. SW1 is turned off when measuring I0, and turned on when measuring I0r_R1.

(2) Second Embodiment The second embodiment is a constant current method. A specific circuit example is shown in FIG. Referring to FIG. 12, device 21 for injecting I0r includes a constant current circuit 22. The constant current circuit 22 is a system that generates and outputs a current having the same phase as the voltage.

(3) Third Embodiment The third embodiment is an internal circuit system. A specific circuit example is shown in FIG. Referring to FIG. 13, device 21 for injecting Ir includes a voltage measurement circuit 23 that measures the voltage from the R phase and the S phase, and a current measurement circuit 24 that measures the current. The voltage measurement circuit 23 includes an input circuit 23a, a filter circuit 23b, a voltage measurement circuit 23c and an I0r generation circuit 23d connected in parallel to the filter circuit 23b, and an addition / non-addition switching control connected to the I0r generation circuit 23d. Circuit 23e. The output from the voltage measurement circuit 23c is input to the CPU 25. A signal from the CPU 25 is input to the addition / non-addition switching control circuit 23e. Here, the addition / non-addition switching control circuit 23e may be omitted.

  On the other hand, the current measuring circuit 24 includes an input circuit 24a, a filter circuit 24b, an amplifier circuit 24c, an adder circuit 24d and an L range amplifier circuit 24e connected in parallel to the amplifier circuit 24c, and an output circuit 24e output from the CPU 25. And an H / L range switching circuit 24f for inputting a signal. The output of the addition / non-addition switching control circuit 23e is input to the addition circuit 24d. Outputs from the adder circuit 24d and the L range amplifier circuit are input to the CPU 25.

  With this configuration, all of the variables a (signal from the amplifier circuit 24c), b (signal from the addition / non-addition switching control circuit 23e), and c (signal from the addition circuit 24d) are obtained. it can.

(4) Fourth Embodiment The fourth embodiment is a software calculation method. A specific calculation method is shown in FIGS. With reference to FIG. 17, the zero crossing point and frequency of the voltage are measured. Specifically, the time of one wave is measured and the frequency is obtained.

  As shown in FIG. 18, Io_R1 can be obtained by creating a pseudo waveform (Ior_R1) of an arbitrary value with software based on the zero cross point and frequency of the voltage, overlaying the measured Io, and performing addition operation.

  As a specific example of the software processing, the combined Io_R1 can be generated by adding instantaneous values based on an AD value by software. FIG. 19 shows three waveforms I0r_R1 (pseudo waveform), I0, and I0_R1 (addition waveform) when the instantaneous values are added as a base.

  As described above, the addition of virtual leakage is not limited to a specific circuit (hardware), and software processing is also possible.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The leakage detector according to the present invention is advantageously used as a leakage detector because it has a simple configuration and high accuracy.

  10 Circuit when R phase and T phase are leaked, 11 ZCT (zero phase current sensor), 20 Leakage circuit when injecting virtual resistance leakage current, 21 device, 25 CPU.

Claims (13)

In a three-phase three-wire circuit in which one phase is grounded, a leakage detector for obtaining a resistance leakage current I0r using a zero-phase current sensor,
A virtual leakage adding means for adding a virtual leakage,
The measured value of the zero-phase current sensor, the measured value of the zero-phase current sensor when a virtual leakage is added, and the vector calculation of the virtual leakage, respectively, the resistance leakage current I0r is calculated by a predetermined vector calculation. What is a leak detector? The leakage detector according to claim 1, wherein the vector calculation performs only vector addition. The leakage detector according to claim 1 or 2, wherein the virtual leakage adding means for adding the virtual leakage adds an apparent virtual leakage to the zero-phase current sensor. The leakage detector according to any one of claims 1 to 3, wherein the vector calculation is performed using the following a, b, and c parameters and equation (1).

However, a = measured value of the zero phase current sensor, b = measured value of the zero phase current sensor when the virtual leakage is added, and c = the virtual leakage. The parameter b is inserted by predetermined insertion means,
The leakage detector according to claim 4, wherein the insertion unit is a resistance connection circuit. The parameter b is inserted by predetermined insertion means,
The leakage detector according to claim 4, wherein the insertion means is a constant current circuit. 3. The leakage detector according to claim 1, wherein the virtual leakage adding unit that adds the virtual leakage adds an apparent virtual leakage on an separately prepared internal circuit. 4. The leakage detector includes a virtual leakage adding means for adding a virtual leakage, a measured value of the zero phase current sensor, a measured value of the zero phase current sensor when a virtual leakage is added, and the virtual leakage. The leakage detector according to claim 7, wherein measurement is performed simultaneously. The leakage detector according to claim 7 or 8, wherein the vector calculation is performed using the following parameters a, b, and c and equation (2).

However, a = measured value of the zero-phase current sensor, b = virtual leakage, c = measured value synthesized by the measured value of the zero-phase current sensor and the virtual leakage. In a three-phase three-wire circuit in which one phase is grounded, a leakage detector for obtaining a resistance leakage current I0r using a zero-phase current sensor,
The measured value of the zero-phase current sensor;
A virtual leakage generating means for measuring a zero-crossing point of the reference voltage and its frequency and generating a virtual leakage based on the measured value;
A leakage detector that obtains a resistance leakage current I0r by a predetermined vector calculation by a vector calculation of a value obtained by combining the measurement value of the zero-phase current sensor and the value generated by the virtual leakage generation unit. The leakage detector according to claim 10, wherein the vector calculation performs only vector addition. The leakage detector according to claim 11, wherein the vector calculation is performed using the following parameters a, b, and c and Equation (3).

However, a = measured value of the zero-phase current sensor, b = virtual leakage, c = measured value of the zero-phase current sensor and a value generated by the virtual leakage generation means. The parameter b is inserted by predetermined insertion means,
The leakage detector according to claim 10, wherein the insertion unit is prepared by software, and the c is synthesized by software.

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