JP2009257870A - Method for detecting phase voltage of three-phase distribution line, zero-phase voltage, line voltage, phase voltage higher harmonic wave of three-phase distribution line, zero-phase voltage higher harmonic wave, and line voltage higher harmonic wave and voltage detecting apparatus used for detection in the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting a phase voltage of a three-phase distribution line, a zero-phase voltage, and a line voltage which is hardly affected by changes in ambient temperature. <P>SOLUTION: A main capacitor and a voltage shunt capacitor are serially connected between each phase of a three-phase distribution line and the ground. A shunt resistor and a temperature-sensing resistor are connected to the voltage shunt capacitor in parallel. The main capacitor is a capacitor having such characteristics that its capacitance may be increased and reduced in inverse proportion to temperature changes and its impedance may proportionally be increased and reduced by this. The temperature-sensing resistor is a resistor of which the resistance value is increased and reduced in proportion to temperature changes. A line-to-ground voltage of each phase is shunted on the basis of the electrostatic capacitance of both capacitors. A phase voltage is detected by the shunt resistor and the temperature-sensing resistor by the voltage shunt capacitor. A detection voltage (phase voltage) of each phase is combined to detect a zero-phase voltage of the three-phase distribution line. On the basis of the voltage difference of detected detection voltages (phase voltages) between an R-phase and an S-phase, a voltage difference of detection voltages (phase voltages) between the S-phase and a T-phase; and a voltage difference of detection voltages (phase voltages) between the R-phase and the T-phase, each line voltage is detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting a phase voltage, a zero phase voltage, a line voltage, a phase voltage harmonic, a zero phase voltage harmonic, and a line voltage harmonic of a three-phase distribution line, and a voltage detection device used for the detection. is there.

  Instrument transformers are used to measure the phase voltage, zero-phase voltage, and line voltage of three-phase distribution lines. However, it is difficult to handle because it is large and heavy. In order to solve this problem, a relatively lightweight capacitor-type transformer utilizing the action of a capacitance voltage divider is used.

  In conventional measurement using a capacitor-type transformer, if the phase voltage, zero phase voltage, and line voltage are to be measured easily, the detected voltage is easily affected by changes in the ambient temperature, and accurate measurement cannot be performed. Therefore, there is a need for a detection method and a detection apparatus that are simple, inexpensive, and have high measurement accuracy. In recent years, due to social needs such as energy conservation and environmental conservation, power generation systems using natural energy such as solar power generation and wind power generation have increased rapidly, and consumer needs such as energy use cost reduction and stable use have been increasing. Cogeneration and waste power generation are steadily increasing due to the rise. Furthermore, recently, new power generation technologies such as fuel cell power generation have been developed, and it is expected that this distributed power source will increase more and more, especially in small-scale ones. On the other hand, such a small-scale distributed power source is rarely operated independently, and is normally operated in conjunction with a power distribution system. For this reason, there are concerns about the occurrence of new problems such as deviation of the standard value of the supply voltage and overload phenomenon at the time of a system fault in the linked distribution system. Along with this, various problems such as line harmonics and voltage imbalance occur in the power distribution system, and the need for a small, lightweight, and inexpensive sensor with high accuracy for measuring these increases. For example, current voltage measurement has a transformer for an electromagnetic type instrument, but it is large in shape and heavy. On the other hand, there is a capacitor type PT that uses a capacitive voltage division between the high voltage circuit and the ground, which is completely different in principle and structure from the electromagnetic type. There are disadvantages. The invention of the present application can solve these problems.

  The method for detecting the phase voltage of the three-phase distribution line of the present application includes a main capacitor and a voltage dividing capacitor connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. In this method, the voltage to ground of each phase is divided based on the difference in capacitance between both capacitors, and the divided voltage is detected by a voltage dividing resistor and a temperature sensitive resistor.

  The zero-phase voltage detection method for the three-phase distribution line of the present application is as described in claim 2, wherein a main capacitor and a voltage dividing capacitor are connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. Then, the voltage to ground of each phase is divided based on the capacitance difference between both capacitors, and the divided voltage is detected by the voltage dividing resistance and the temperature sensitive resistance, and the detected voltage (phase voltage) of each phase detected Is used to detect the zero-phase voltage of the three-phase distribution line.

  In the method for detecting the line voltage of the three-phase distribution line of the present application, a main capacitor and a voltage dividing capacitor are connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. Then, the voltage to ground of each phase is divided based on the capacitance difference between the two capacitors, the divided voltage is detected by the voltage dividing resistance and the temperature sensitive resistance, and the detected voltage between the detected R phase and S phase ( This is a method for detecting each phase voltage from the voltage difference of the phase voltage), the voltage difference of the detection voltage (phase voltage) between the S phase and the T phase, and the voltage difference of the detection voltage (phase voltage) between the R phase and the T phase. .

  In the method for detecting phase voltage harmonics of a three-phase distribution line of the present application, a main capacitor and a voltage dividing capacitor are connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. Then, it is a method of dividing the harmonic voltage to ground of each phase based on the capacitance difference between both capacitors and detecting the harmonic divided voltage by a voltage dividing resistor and a temperature sensitive resistor.

  The zero-phase voltage harmonic detection method for the three-phase distribution line of the present application includes a main capacitor and a voltage dividing capacitor in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. Connected, voltage to ground of each phase is divided based on the capacitance difference of both capacitors, the divided voltage is detected by voltage dividing resistance and temperature sensitive resistance, and the detected voltage of each phase (phase This is a method for detecting zero-phase voltage harmonics of a three-phase distribution line by synthesizing voltage) harmonics.

  In the method for detecting line voltage harmonics in a three-phase distribution line of the present application, a main capacitor and a voltage dividing capacitor are connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground. Connected, and the voltage to ground of each phase is divided based on the capacitance difference between the two capacitors, the divided voltage is detected by the voltage dividing resistance and the temperature sensitive resistance, and the detected harmonics between the R phase and the S phase are detected. From the voltage difference of the wave detection voltage (phase voltage), the voltage difference of the harmonic detection voltage (phase voltage) between the S phase and the T phase, the voltage difference of the harmonic detection voltage (phase voltage) between the R phase and the T phase, This is a method of detecting line voltage harmonics.

  The voltage detection device for a three-phase distribution line according to the present application includes a phase voltage, a zero-phase voltage, a line voltage, a phase voltage harmonic, a zero-phase voltage harmonic, and a line voltage harmonic of the three-phase distribution line. In a voltage detection device used for wave detection, a main capacitor and a voltage dividing capacitor connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and a voltage dividing capacitor connected in parallel It is a device with partial pressure resistance and temperature sensitive resistance.

  The voltage detection device for a three-phase distribution line according to the present application is the voltage detection device for a three-phase distribution line according to claim 7, in which the main capacitor increases and decreases in inverse proportion to the temperature change of the capacity and the impedance is proportional. Thus, a capacitor having a characteristic that increases or decreases and a temperature-sensitive resistor are devices in which the resistance value increases or decreases in proportion to a temperature change.

  The voltage detection device for a three-phase distribution line of the present application is the voltage detection device for a three-phase distribution line according to claim 4, wherein the main capacitor is a capacitor having a characteristic that increases and decreases in inverse proportion to the temperature change of the capacitance, and the impedance increases and decreases in proportion. A temperature-sensitive resistor is a device whose resistance value increases or decreases in proportion to a temperature change.

  The phase voltage detection method, zero-phase voltage detection method, and line voltage detection method of the three-phase distribution line of the present invention all have a capacitance difference between a voltage dividing capacitor connected in series with the main capacitor and the voltage between each phase and ground. The voltage divided by the voltage dividing capacitor is detected by the voltage dividing resistor and the temperature sensitive resistor, so the capacitor with the characteristic that the capacitance increases and decreases inversely with the temperature change and the impedance increases and decreases proportionally as the main capacitor. By using a resistor whose resistance value increases or decreases in proportion to the temperature change as a temperature-sensitive resistor, even if the ambient temperature changes, it is not easily affected, and accurate voltage detection is possible. There is an effect that it can be solved.

  Since the voltage detection device of the present invention is composed of the combination of the capacitor and the temperature sensitive resistor, the voltage detection device has a small output variation with respect to the ambient temperature change. Moreover, it is small and lightweight, and it is easy to handle, and there is an effect that the problems of the prior art can be solved.

(Principle of capacitor type divided voltage)
The principle of the capacitor-type divided voltage will be described with reference to FIG. When a voltage is applied to _two capacitors connected in series as shown in FIG. 1 (capacitances are C ₁ and C ₂ , respectively), a current flows, and the relationship between the voltage across the capacitor and the current is:
Current = 2πf (frequency) × capacitance × voltage,
Since the same current flows through the main capacitor C ₁ and the voltage dividing capacitor C ₂ ,
2πf × C ₁ (V ₁ −V ₂ ) = 2πfC ₂ × V ₂
This
C ₁ × V ₁ = (C ₁ + C ₂ ) × V ₂
Thus, the transformation ratio = V ₁ / V ₂ = (C ₁ + C ₂ ) / C ₁ holds between the primary voltage and the secondary voltage.

(Description of the principle of the voltage detection device)
FIG. 2 shows a circuit for one phase of the phase voltage detection device using the capacitor voltage division of the present invention. In this voltage detector, a main capacitor C ₁ and a voltage dividing capacitor C ₂ are connected in series between one phase of the three-phase distribution line and the ground, and a voltage dividing resistor R ₁ and a temperature sensitive resistor R ₂ are connected in parallel to the voltage dividing capacitor C _2. It is. When an AC voltage V ₁ (AC 2000 V) is applied between the terminals 1 and 2 of this circuit, this voltage is applied to the main capacitor (for example, ceramic capacitor) C ₁ with a voltage V ₂ (1999.25 V) and a voltage dividing capacitor (for example, film capacitor). ) The voltage V ₃ (0.75 V) is apportioned at both ends of C ₂ , and the voltage V ₄ (0.5 V) is output to the terminals 3 to 4 through the voltage dividing resistor R ₁ and the temperature sensitive resistor R _2. The

(Embodiments of phase voltage detection device and phase voltage detection method)
FIG. 3 shows a phase voltage detection apparatus using a capacitor voltage division according to the present invention. In FIG. 3, a main capacitor C ₁ and a voltage dividing capacitor C ₂ are connected in series between the R phase and the ground, and a voltage dividing resistor R ₁ and a temperature sensitive resistor R ₂ are connected in parallel to the voltage dividing capacitor C _2. A main capacitor C ₃ and a voltage dividing capacitor C ₄ are connected in series, a voltage dividing resistor R ₃ and a temperature sensitive resistor R ₄ are connected in parallel to the voltage dividing capacitor C ₄ , and the main capacitor C ₅ is connected between the T phase and the ground. A voltage dividing capacitor C ₆ is connected in series, and a voltage dividing resistor R ₅ and a temperature sensitive resistor R ₆ are connected in parallel to the voltage dividing capacitor C ₆ . In order to detect the phase voltages of the R, S, and T phases in these connection states, the R-to-ground voltage is divided based on the capacitance difference between the capacitors C ₁ and C ₂ , and the voltage dividing capacitor C ₂ is detected as an R-phase output voltage (phase voltage) by the voltage dividing resistor R ₁ and the temperature-sensitive resistor R ₂ . The S-phase voltage to ground is divided based on the capacitance difference between the capacitors C ₃ and C ₄ , and the output voltage of the voltage dividing capacitor C ₄ is output to the S-phase by the voltage dividing resistor R ₃ and the temperature sensitive resistor R _4. Detect as voltage (phase voltage). The T-phase voltage to ground is divided based on the capacitance difference between the capacitors C ₅ and C ₆ , and the output voltage of the voltage dividing capacitor C ₆ is output from the voltage dividing resistor R ₅ and the temperature sensitive resistor R ₆ to the T-phase. Detect as voltage (phase voltage).

(Embodiments of zero-phase voltage detection device and zero-phase voltage detection method)
FIG. 4 shows a circuit of the zero-phase voltage detection device using the capacitor voltage division according to the present invention. In FIG. 4, a main capacitor C ₇ and a voltage dividing capacitor C ₈ are connected in series between the R phase and the ground, and a voltage dividing resistor R ₇ and a temperature sensitive resistor R ₈ are connected in parallel to the voltage dividing capacitor C _8. A main capacitor C ₉ and a voltage dividing capacitor C ₁₀ are connected in series, a voltage dividing resistor R ₉ and a temperature sensitive resistor R ₁₀ are connected in parallel to the voltage dividing capacitor C ₁₀ , and the main capacitor C ₁₁ is connected between the T phase and the ground. the divider capacitor C ₁₂ connected in series, the voltage dividing capacitor C ₁₂ binary resistors R ₁₁ and the temperature sensitive resistor R ₁₂ are connected in parallel. In order to detect the zero-phase voltage of each phase of R, S, and T in these connection states, the voltage between the R-phase grounds is divided based on the capacitance difference between the capacitors C ₇ and C ₈ , The output voltage of the capacitor C ₈ is detected as the R-phase output voltage (phase voltage) by the voltage dividing resistor R ₇ and the temperature-sensitive resistor R ₈ , and the ground-to-ground voltage of the S phase is the capacitance of both capacitors C ₉ and C _10. divided based on the difference, the divided output voltage dividing resistors R ₉ of the capacitor C _10, detected as the output voltage of the S-phase (phase voltage) by the temperature sensitive resistive R _10, T-phase two capacitors to ground voltage of The voltage is divided based on the capacitance difference between C ₁₁ and C ₁₂ , and the output voltage of the voltage dividing capacitor C ₁₂ is detected as a T-phase output voltage (phase voltage) from the voltage dividing resistor R ₁₁ and the temperature sensitive resistor R ₁₂ . The three-phase voltage detected in this way is combined as shown in FIG. 4 to detect the zero-phase voltage of the three-phase distribution line.

(Embodiment of Line Voltage Detection Device and Line Voltage Detection Method)
FIG. 5 shows a circuit of the line voltage detecting device using the capacitor voltage division according to the present invention. In FIG. 5, a main capacitor C ₁₃ and a voltage dividing capacitor C ₁₄ are connected in series between the R phase and the ground, and a voltage dividing resistor R ₁₃ and a temperature sensitive resistor R ₁₄ are connected in parallel to the voltage dividing capacitor C _14. the main capacitor C ₁₅ and voltage dividing capacitor C ₁₆ connected in series between, minute pressure capacitor C ₁₆ binary resistors R ₁₅ and the temperature sensitive resistor R ₁₆ connected in parallel, the main capacitor C ₁₇ between T phase and ground A voltage dividing capacitor C ₁₈ is connected in series, and a voltage dividing resistor R ₁₇ and a temperature sensitive resistor R ₁₈ are connected in parallel to the voltage dividing capacitor C ₁₈ . To detect the voltage between the R phase and the S phase, between the S phase and the T phase, and between the R phase and the T phase in these connection states, the voltage between the R phase and the ground is determined based on the capacitance difference between the capacitors C ₁₃ and C _14. pressure Te partial, partial pressure dividing resistor R ₁₃ to the output voltage of the capacitor C _14, detected as the output voltage of the R-phase (phase voltage) by the temperature-sensitive resistor R _14, ground voltage both capacitor C ₁₅ of the S-phase, divided based on the capacitance difference C _16, detected as a divided voltage dividing resistor R ₁₅ to the output voltage of the capacitor C _16, S-phase of the output voltage by the temperature sensitive resistor R ₁₆ (phase voltage) of the T-phase The voltage to ground is divided based on the capacitance difference between the two capacitors C ₁₇ and C ₁₈ , and the output voltage of the voltage dividing capacitor C ₁₈ is output from the voltage dividing resistor R ₁₇ and the temperature sensitive resistor R ₁₈ to the T-phase output voltage (phase Voltage). From the three-phase phase voltage thus detected, the line voltage between R and S, the line voltage between S and T, and the line voltage between R and T are detected as shown in FIG.

The main capacitor C ₁ in FIGS. 3 to 5 in the present _{invention, C 3, C 5, C} 7, C 9, C 11, C 13, a ceramic capacitor as an example of a C _15, C _17, dividing capacitors C _2, A film capacitor can be used as an example of C ₄ , C ₆ , C ₈ , C ₁₀ , C ₁₂ , C ₁₄ , C ₁₆ , C ₁₈ . The temperature change characteristics of these capacitors are shown in FIG. In FIG. 6, the a line indicates the temperature change characteristic of the ceramic capacitor, and the b line indicates the temperature change characteristic of the film capacitor. As the temperature of the ceramic capacitor increases, the capacitance decreases and the impedance increases. As the temperature decreases, the capacitance increases and the impedance decreases.

In the present invention, as an example of the voltage dividing resistors R ₁ , R ₃ , R ₅ , R ₇ , R ₉ , R ₁₁ , R ₁₃ , R ₁₅ , R ₁₇ , carbon resistance is used, and temperature sensitive resistors R ₂ , R ₄ , R ₁₇ are used. _A thermistor can be used as an example of ₆ , R ₈ , R ₁₀ , R ₁₂ , R ₁₄ , R ₁₆ , R ₁₈ . The temperature change characteristics of these resistors are shown in FIG. In FIG. 7, the a line indicates the temperature change characteristic of the carbon resistance, and the b line indicates the temperature change characteristic of the temperature sensitive resistance. The resistance value of the temperature sensitive resistor (thermistor) increases as the temperature increases, and decreases as the temperature decreases.

(Test example)
Table 1 shows the specifications of a test example of the voltage detection method of the present invention (capacitor voltage dividing method as a voltage acquisition measurement method of the high-voltage acquisition unit).

(Temperature characteristics test)
Under the specifications in Table 1, the main capacitor (C ₀ ), the voltage dividing capacitor (C ₁ ), the fixed resistor (R ₁ ), and the temperature sensitive resistor (R ₂ ) are placed in the thermostat shown in FIG. The temperature was changed from −40 ° C. to + 60 ° C., and the output voltage (V ₂ ) and output voltage (V ₃ ) when V ₀ = 2000V were measured.
The origin of FIG. 8 is as follows.
C ₀ : 250 pF
C ₁ : 0.655 μF
R ₁ : 5 kΩ 100 ppm, fixed resistance R ₂ : 5.1 kΩ 2700 ppm × 2, series connection, temperature sensitive resistance V ₀ : input voltage (high voltage conversion value)
V ₁ : Input voltage (low voltage measurement value)
V ₂ : Output voltage (temperature compensation)
V ₃ : Capacitor output voltage T ₁ : 110V / 6600V
T ₂ : 6600V / 110V

(Test method)
In this test, in the above temperature range, left at + 20 ° C. for 90 minutes → 0 ° C. for 70 minutes → −20 ° C. for 70 minutes → −40 ° C. for 75 minutes → + 40 ° C. for 80 minutes → + 60 ° C. for 60 minutes The measurement was performed after being left for the above time after reaching the respective set temperatures.

(Test results)
The measurement results were as shown in Tables 2 to 8. FIG. 9 is a graph showing the result. From these results, it can be seen that when the ambient temperature changes from −40 ° C. to + 60 ° C., the output voltage V3 varies depending on the ambient temperature, but the output voltage V2 varies little due to the ambient temperature. In the conventional case, the error is about ± 5%, but the error in the present invention is about 1%. That is, according to the present invention, it has been proved that even when the ambient temperature changes, it is possible to measure the output voltage with high accuracy by greatly improving the output voltage error, which is a drawback of the capacitor voltage division.

(Temperature test result)
The ceramic capacitor, the film capacitor, the carbon resistor, and the temperature-sensitive resistor described above are merely examples that can be used in the present invention, and other capacitors can be used as long as the object of the present invention can be achieved. Of course.

(Frequency change temperature characteristics test)
Under the specifications in Table 1, the main capacitor (C ₀ ), the voltage dividing capacitor (C ₁ ), the fixed resistor (R ₁ ), and the temperature sensitive resistor (R ₂ ) are placed in the thermostat shown in FIG. The output voltage (V ₂ ) when V ₁ = 100 V was measured while changing the temperature from −30 ° C. to + 40 ° C.
The origin of FIG. 10 is as follows.
C ₀ : 250 pF
C ₁ : 0.655 μF
C ₂ : 0.01 μF
R ₁ : 1.6 kΩ 100 ppm, fixed resistance R ₂ : 5 kΩ 2700 ppm × 2, series connection, temperature sensitive resistance V ₁ : input voltage 100V
V ₂ : Output voltage 33.3 mV
Input / output ratio dB = 20 Log (V ₂ ÷ (V ₁ × 1000))

(Test method)
In this test, in the above temperature range, it was set to stand at + 20 ° C. for 90 minutes → -30 ° C. for 70 minutes → + 40 ° C. for 60 minutes.

(Test results)
The measurement results are shown in Table 9. The result is graphed as shown in FIG. From these results, it can be seen that when the ambient temperature is changed from −30 ° C. to + 40 ° C., the input / output ratio dB is less changed by the ambient temperature. In the conventional case, the fluctuation range is 3 dB or less, but the fluctuation range in the present invention is 1 dB or less. That is, according to the present invention, it was confirmed that even if the ambient temperature changes, it is possible to measure the frequency characteristics with high accuracy by greatly improving the variation of the fluctuation range, which is a drawback of the capacitor partial pressure.

  The three-phase distribution line phase voltage harmonic detection method, the three-phase distribution line zero-phase voltage harmonic detection method, the three-phase distribution line voltage harmonic detection method, the three-phase distribution line phase voltage detection method, The waveform of the divided voltage detected by the zero-phase voltage detection method of the phase distribution line and the line voltage detection method of the three-phase distribution line can be measured by analyzing with a waveform observation device, for example, a data logger.

The principle explanatory drawing of the existing capacitor voltage dividing circuit. BRIEF DESCRIPTION OF THE DRAWINGS Basic explanatory drawing of the capacitor | condenser type voltage detection apparatus of this invention. Explanatory drawing which shows an example of the phase voltage detection apparatus of this invention. Explanatory drawing which shows an example of the zero phase voltage detection apparatus of this invention. Explanatory drawing which shows an example of the line voltage detection apparatus of this invention. Temperature characteristics of ceramic capacitors and film capacitors. Temperature characteristic diagram of carbon resistance and temperature sensitive resistance. An example of the test circuit diagram of the phase voltage detection method of this invention. Explanatory drawing of the input-output temperature change characteristic which shows the result of the phase voltage detection test of this invention. Explanatory drawing of the input-output temperature change characteristic which shows the result of the phase voltage detection harmonic test of this invention. The input-output temperature change characteristic figure which shows the result of a phase voltage detection harmonic test.

Explanation of symbols

_{C 1, C 3, C 5} , C 7, C 9, C 11, C 13, C 15, C 17: main capacitor _{C 2, C 4, C 6} , C 8, C 10, C 12, C 14, C _16, C _18: dividing capacitors _{R 1, R 3, R 5} , R 7, R 9, R 11, R 13, R 15, R 17: voltage dividing resistors _{R 2, R 4, R 6} , R 8 , R ₁₀ , R ₁₂ , R ₁₄ , R ₁₆ , R ₁₈ : Temperature sensitive resistance

Claims (8)

  A main capacitor and a voltage dividing capacitor are connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and the voltage between each phase is divided based on the capacitance difference between the two capacitors. A method for detecting a phase voltage of a three-phase distribution line, wherein the divided voltage is detected by a voltage dividing resistor and a temperature sensitive resistor.   A main capacitor and a voltage dividing capacitor are connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and the voltage between each phase is divided based on the capacitance difference between the two capacitors. A three-phase distribution line characterized in that the divided voltage is detected by a voltage dividing resistor and a temperature-sensitive resistor, and the detected voltage (phase voltage) of each detected phase is combined to detect the zero-phase voltage of the three-phase distribution line. Zero phase voltage detection method.   A main capacitor and a voltage dividing capacitor are connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and the voltage between each phase is divided based on the capacitance difference between the two capacitors. The divided voltage is detected by a voltage dividing resistor and a temperature sensitive resistor, and the detected voltage difference between the detected phase (phase voltage) of the R phase and the S phase, and the voltage difference of the detected voltage (phase voltage) between the S phase and the T phase. A method for detecting a line voltage of a three-phase distribution line, wherein a voltage between phases is detected from a voltage difference between detection voltages (phase voltages) between an R phase and a T phase.   A main capacitor and a voltage dividing capacitor are connected in series between the R-phase, S-phase, and T-phase of the three-phase distribution line and the ground, and the harmonic voltage between each phase is divided based on the capacitance difference between the two capacitors. A method for detecting a phase voltage harmonic of a three-phase distribution line, wherein the voltage is detected by a voltage dividing resistor and a temperature sensitive resistor.   A main capacitor and a voltage dividing capacitor are connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and the voltage between each phase is divided based on the capacitance difference between the two capacitors. The voltage is detected by voltage dividing resistance and temperature sensitive resistance, and the detected voltage (phase voltage) harmonic of each phase is synthesized to detect the zero-phase voltage harmonic of the three-phase distribution line. To detect zero-phase voltage harmonics in three-phase distribution lines.   A main capacitor and a voltage dividing capacitor are connected in series between the R phase, S phase, and T phase of the three-phase distribution line and the ground, and the voltage between each phase is divided based on the capacitance difference between the two capacitors. The divided voltage is detected by a voltage dividing resistor and a temperature sensitive resistor, and the detected voltage difference between the R phase and the S phase (phase voltage) and the detected voltage between the S phase and the T phase (harmonic phase voltage). ) Line voltage of a three-phase distribution line characterized by detecting each line voltage harmonic from the voltage difference of the harmonics and the harmonic detection voltage (phase voltage) between the R phase and the T phase. Harmonic detection method.   In the voltage detector used to detect the phase voltage, zero phase voltage, line voltage, phase voltage harmonic, zero phase voltage harmonic, line voltage harmonic of the three phase distribution line, the R phase, S of the three phase distribution line A three-phase distribution line voltage comprising a main capacitor and a voltage dividing capacitor connected in series between each of the phase and the T phase, and a voltage dividing resistor and a temperature sensitive resistor connected in parallel to the voltage dividing capacitor Detection device.   8. The voltage detector for a three-phase distribution line according to claim 7, wherein the main capacitor is a capacitor having a characteristic in which the capacitance increases and decreases in inverse proportion to the temperature change and the impedance increases and decreases in proportion. The temperature sensitive resistor has a resistance value that changes in temperature. A voltage detector for a three-phase distribution line, characterized by a resistance that increases and decreases in proportion.

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