JPH11316257A - Method for measuring water tree length at water tree degraded part, method for measuring conductivity and dielectric constant of water tree degraded part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure water tree length and conductivity and dielectric constant of water tree degraded part without slicing an insulator. SOLUTION: A pre-determined parameter required for calculation element for water tree length, conductivity σW and dielectric constant εW at water tree degraded part of an insulator sample 10 is calculated by measuring complex impedance of the insulator sample 10 through measurement of voltage and current at different frequencies applied to the insulator sample 10, at measurement of water tree length of the insulator sample 10 and conductivity σW and dielectric constant εW of water tree degraded part through conversion of the insulator sample 10 where water tree occurring into an equivalent circuit 20 wherein a water tree degraded part 11 where capacitance CW and conductance GW are connected in parallel is connected to a sound part 12 which is capacitance CP in series while the entire of insulator sample 10 into an equivalent circuit 30 wherein capacitance C and conductance G are connected in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for non-destructively measuring the length of a water tree generated in an insulator, the conductivity and the dielectric constant of a water tree deteriorated portion.

[0002]

2. Description of the Related Art Conventionally, to determine the state of occurrence of water trees in an insulator, in particular, the water tree length, the conductivity and the dielectric constant of a water tree deteriorated portion, as shown in FIGS. 3 (a) and 3 (b). Then, a method of thinly slicing the insulator sample 10 in which a water tree is generated, visually observing the water tree length l _W with a microscope, or directly measuring the conductivity and the dielectric constant from the sliced piece 10a has been proposed. ing.

[0003]

However, in such a measuring method, since the insulator sample 10 is sliced, an electrical test cannot be performed thereafter, and
Since the conductivity and the dielectric constant of the water tree deteriorated portion strongly depend on the water content, when the insulator sample 10 is sliced, the water content changes and it is difficult to measure the conductivity and the dielectric constant accurately.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and a method for measuring a water tree length, a conductivity of a water tree deteriorated portion and a dielectric constant without slicing an insulator. The purpose is to provide.

[0005]

In order to achieve the above object, a method for measuring the water tree length of a water tree deterioration section according to the present invention is to provide a water tree deterioration section in which an insulator having water trees is connected in parallel with a capacitance and a conductance. And an equivalent circuit in which a sound part which is a capacitance is connected in series, and the entire insulator sample is converted into an equivalent circuit in which a capacitance and a conductance are connected in series. A measuring method for measuring,
Measure the voltage and current at different frequencies applied to the insulator, calculate the complex impedance of the insulator, calculate the capacitance and conductance for each frequency from the complex impedance, and calculate the capacitance and conductance for each frequency Arithmetic element determined in advance from

[0006]

[Equation 11]

[0007] The capacitance of the sound part is calculated according to the following formula, and a calculation element determined in advance from the capacitance of the sound part.

[0008]

(Equation 12)

(Where S is the area where water trees are generated, ε ₀ is the vacuum dielectric constant, and ε _P is the relative dielectric constant of the insulating material.) The water tree length of the water tree deteriorated portion is measured. In addition, the method for measuring the conductivity of a water tree deteriorated portion of the present invention is an equivalent circuit in which an insulator in which a water tree is generated is connected in series with a water tree deteriorated portion in which capacitance and conductance are connected in parallel, and a sound portion which is capacitance is connected in series. ,
A method of measuring the conductivity of the water tree deteriorated portion of the insulator by converting the entire insulator sample into an equivalent circuit in which the capacitance and the conductance are connected in series. A voltage and a current are measured, a complex impedance of the insulator is calculated, a capacitance and a conductance for each frequency are calculated from the complex impedance, and a calculation element determined in advance from the capacitance and the conductance for each frequency

[0010]

(Equation 13)

[0011]

[Equation 14]

The capacitance of the sound part and the conductance of the water tree deteriorated part are calculated by the above, and a calculation element determined in advance from the capacitance of the sound part.

[0013]

(Equation 15)

(Where S is the area where the water tree is generated, ε ₀ is the vacuum dielectric constant, ε _P is the relative dielectric constant of the insulating material), and the water tree length of the water tree deteriorated portion is calculated. Calculation element predetermined from water tree length of deteriorated part and conductance of water tree deteriorated part

[0015]

(Equation 16)

The conductivity of the water tree deteriorated portion is measured by the above method. Further, the method for measuring the dielectric constant of the water tree deteriorated portion of the present invention is an equivalent circuit in which an insulator in which water tree is generated is connected in series with a water tree deteriorated portion in which capacitance and conductance are connected in parallel, and a sound portion which is capacitance is connected in series. And a method of measuring the dielectric constant of the water tree deteriorated portion of the insulator by converting the entire insulator sample into an equivalent circuit in which the capacitance and the conductance are connected in series, and using different frequencies applied to the insulator. , The complex impedance of the insulator is calculated, the capacitance and conductance of each frequency are calculated from the complex impedance, and the calculation element is determined in advance from the capacitance and conductance of each frequency.

[0017]

[Equation 17]

[0018]

(Equation 18)

By calculating the capacitance of the sound part and the capacitance of the water tree deterioration part, the operation element determined in advance from the capacitance of the sound part

[0020]

(Equation 19)

(Where S is the area where the water tree is generated, ε ₀ is the vacuum dielectric constant, and ε _P is the relative dielectric constant of the insulating material). Calculation element determined in advance from the water tree length of the deteriorated part and the capacitance of the water tree deteriorated part

[0022]

(Equation 20)

Is used to measure the dielectric constant of the water tree deteriorated portion. According to these, by applying voltages of different frequencies and measuring the complex impedance, it is possible to calculate the parameters necessary for the calculation elements for calculating the water tree length, the conductivity and the dielectric constant of the water tree deteriorated part, The water tree length, the conductivity and the dielectric constant of the water tree deteriorated portion can be measured without slicing the sample.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for measuring the water tree length of a water tree deteriorated portion, a method for measuring the conductivity of a water tree deteriorated portion, and a method for measuring a dielectric constant according to the present invention will be described below with reference to the drawings. I do. The measuring apparatus to which the measuring method of the present invention is applied mainly includes, for example, as shown in FIG.
It comprises a detection resistor R1 and an arithmetic processing unit 3.
The AC generator 2 has one terminal connected to a measurement terminal 4 for connection to one surface 10a of the insulator sample 10, and the other terminal connected to one end of a detection resistor R1. The other end of the detection resistor R1 is connected to a measurement terminal 5 for connecting to the other surface 10b of the insulator sample 10. The other terminal of the AC generator 2 is connected to the ground.

The detection resistor R1 is connected to a current ^IejQ (where Q = θ +
φ. Hereinafter, the same applies to this embodiment. ) And is connected to the arithmetic processing unit 3. The arithmetic processing section 3 performs arithmetic processing on the length of the water tree generated in the insulator sample 10 and the conductivity and the dielectric constant of the water tree deteriorated portion. More specifically, as shown in FIG.
The arithmetic processing is performed on the assumption that it can be divided into the sound part 12 and the sound part 12. Assuming this, the conductivity σ of the sound part 12
Since _P is substantially zero, FIG. As shown in 2 (b), water tree degradation unit 11 where the insulator samples 10 are connected in parallel capacitance C _W and conductance G _W, healthy part is the capacitance C _P 12 can be converted to an equivalent circuit 20 in which the capacitors 12 and 12 are connected in series. Further, FIG.
As shown in (c), an equivalent circuit 3 in which the capacitance C and the conductance G are connected in series with the entire insulator sample 10
Convert to 0.

From each of the equivalent circuits 20 and 30,

[0027]

[Equation 21]

The following relational expression holds. From the real and imaginary parts of this relation,

[0029]

[Equation 22]

[0030]

[Equation 23]

[0031] Two complex numbers are obtained.
In order to calculate the capacitance C _P of the sound part 12 and the conductance G _W and the capacitance C _W of the water tree deterioration part 11 based on the two complex equations, different frequencies ω ₁ and ω ₂ applied to the insulator sample 10 are used. Voltage Ve
^jK (where K = θ; hereinafter the same in this embodiment) and current Ie ^jQ are measured, and the insulator sample 1 is measured.
By calculating a complex impedance Z of 0, each frequency ω ₁ ,
By calculating the capacitances C ₁ and C ₂ and the conductances G ₁ and G ₂ for each ω ₂ , the capacitance C _P of the sound part 12 and the conductance G _W and the capacitance C _W of the water tree deterioration part 11 are as follows.

[0032]

[Equation 24]

[0033]

[Equation 25]

[0034]

[Equation 26]

## EQU1 ## Here, when ω = ω ₁ , G = G ₁ , and when ω = ω ₂ , G = G ₂ . Therefore, the equation (4), (5), (6) calculates the capacitance C _W, the conductance G _W capacitance C _P and the water tree degradation portion 11 of the sound unit 12 from the complex impedance Z of the insulator samples 10 Is a predetermined calculation element for the calculation.

As described above, the capacitance C of the sound part 12 of the insulator sample 10 calculated by the predetermined calculation element
_P and the capacitance C _W and the conductance G _W of the water tree deterioration unit 11 are predetermined arithmetic elements.

[0037]

[Equation 27]

[0038]

[Equation 28]

[0039]

[Equation 29]

The water tree length l _W of the water tree deterioration section 11 (FIG. 3B), the conductivity σ _W and the dielectric constant ε _W of the water tree deterioration section 11 are obtained. However, S is the area where the water tree is generated (FIG. 3A) and needs to be obtained in advance by some method. Ε ₀ is the vacuum permittivity,
ε _P is the relative dielectric constant of the insulating material. The arithmetic processing unit 3
Is connected to the AC generator 2 and has a function of changing the frequency of the AC voltage V generated by the AC generator 2.

A method of measuring the water tree length of the insulator sample 10, the conductivity of the water tree deteriorated portion, and the dielectric constant with the measuring apparatus 1 configured as described above will be described. First, the measuring terminal 4 of the measuring device 1 is connected to one surface 10a of the insulator sample 10.
Next, the measuring terminals 5 are connected to the other surface 10b of the insulator sample 10, respectively. Then, different frequencies ω ₁ and ω ₂ are set in the arithmetic processing unit 3, and the insulator sample 1 is set in the AC generator 2.
0 different frequencies omega ₁ is applied to, omega voltage Ve ^jK and current Ie ^jQ measured at _2, each frequency omega _1, omega complex impedance Z and processing of every _two, each frequency omega from the respective complex impedance Z ₁ , the capacitance C ₁ per ω ₂ ,
C ₂ and conductances G ₁ , G ₂ are arithmetically processed, and the capacitances C ₁ , C ₂ and conductances G ₁ , G ₂ for each of the frequencies ω ₁ , ω ₂ are calculated in advance by equation (4). , (5), (6), (7), (8), (9)
, The water tree length l _W , the conductivity σ _W and the dielectric constant ε _W of the water tree deterioration section 11 can be measured.

[0042]

As described above, according to the measuring method of the present invention, by applying voltages of different frequencies and measuring the complex impedance, the water tree length, the conductivity of the water tree deteriorated portion and the dielectric Since the parameters required for the calculation element for calculating the rate can be calculated, the water tree length, the conductivity of the water tree deteriorated portion, and the dielectric constant can be measured without slicing the insulator sample. Therefore, an electrical test can be performed after measuring the insulator sample, and the water content of the water tree deteriorated portion does not change, so that more accurate conductivity and dielectric constant can be obtained. Further, the present invention can be applied to diagnosis of insulation deterioration of a power cable.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a measuring device to which a measuring method of the present invention is applied.

FIG. 2 is an equivalent circuit diagram of an insulator sample having undergone water tree deterioration.

3A and 3B are explanatory diagrams showing a conventional method for measuring a water tree length, where FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along line AA of FIG.

[Explanation of symbols]

10 Insulator sample 11 Water deteriorating part 12 Sound part 20 Equivalent circuit in which water tree deteriorating part and sound part are connected in series 30 ... Equivalent circuit of the whole insulator sample ω ₁ , ω ₂ ... Different frequencies Ve ^jK ... Voltage Ie ^jQ ... Current l _W ... Water tree length σ _W ···· Electrical conductivity of water tree deteriorated part ε _W ···· Dielectric constant of water tree deteriorated part

Claims (3)

[Claims] 1. An equivalent circuit in which a water tree deteriorated portion in which an insulator having water tree generated is connected in parallel with a capacitance (C _W ) and a conductance (G _W ) and a sound portion which is a capacitance (C _P ) are connected in series. And measuring the water tree length of the water tree deteriorated portion of the insulator by converting the entire insulator sample into an equivalent circuit in which a capacitance (C) and a conductance (G) are connected in series. The voltage ( ^VejK (where K = θ)) and current (Ie) at different frequencies (ω ₁ , ω ₂ ) applied to the insulator.
^jQ (where Q = θ + φ)) is measured to calculate the complex impedance (Z) of the insulator, and the capacitance (C ₁ , C ₁ ,
C ₂ ) and conductances (G ₁ , G ₂ ) are calculated, and a calculation element determined in advance from the capacitance and conductance for each frequency is: The capacitance of the sound part is calculated by the following equation, and a calculation element determined in advance from the capacitance of the sound part (However, S is the area where water tree occurs, ε ₀ is the vacuum dielectric constant,
ε _P is the relative dielectric constant of the insulating material. A) measuring the water tree length (l _W ) of the water tree deteriorated section according to (1). 2. An equivalent circuit in which a water tree deteriorated portion in which an insulator having water tree generated is connected in parallel with a capacitance (C _W ) and a conductance (G _W ) and a sound portion which is a capacitance (C _P ) are connected in series. And measuring the conductivity of the water tree deteriorated portion of the insulator by converting the entire insulator sample into an equivalent circuit in which a capacitance (C) and a conductance (G) are connected in series. The voltage ( ^VejK (where K = θ)) and the current (Ie) at different frequencies (ω ₁ , ω ₂ ) applied to the insulator.
^jQ (where Q = θ + φ)) is measured to calculate the complex impedance (Z) of the insulator, and the capacitance (C ₁ , C ₁ ,
C ₂ ) and conductances (G ₁ , G ₂ ) are calculated, and a calculation element determined in advance from the capacitance and conductance for each frequency is (Equation 4) The capacitance of the sound part and the conductance of the water tree deterioration part are calculated by the following formula, and a calculation element predetermined from the capacitance of the sound part is (However, S is the area where water tree occurs, ε ₀ is the vacuum dielectric constant,
ε _P is the relative dielectric constant of the insulating material. ) To calculate the water tree length (l _W ) of the water tree deterioration section, and a calculation element predetermined from the water tree length of the water tree deterioration section and the conductance of the water tree deterioration section. Measuring the conductivity (σ _W ) of the water tree deteriorated portion by using the method. 3. An equivalent circuit in which a water tree deteriorated portion in which an insulator in which water tree is generated is connected in parallel with a capacitance (C _W ) and a conductance (G _W ) and a sound portion which is a capacitance (C _P ) are connected in series. And measuring the dielectric constant of the water-tree-deteriorated portion of the insulator by converting the entire insulator sample into an equivalent circuit in which a capacitance (C) and a conductance (G) are connected in series. The voltage ( ^VejK (where K = θ)) and the current (Ie) at different frequencies (ω ₁ , ω ₂ ) applied to the insulator.
^jQ (where Q = θ + φ)) is measured to calculate the complex impedance (Z) of the insulator, and the capacitance (C ₁ , C ₁ ,
C ₂ ) and conductance (G ₁ , G ₂ ) are calculated, and a calculation element determined in advance from the capacitance and conductance for each frequency is (Equation 8) The capacitance of the sound part and the capacitance of the water tree deterioration part are calculated according to the following formula. (However, S is the area where water tree occurs, ε ₀ is the vacuum dielectric constant,
ε _P is the relative dielectric constant of the insulating material. ) Is used to calculate the water tree length (l _W ) of the water tree deterioration section, and a calculation element determined in advance from the water tree length of the water tree deterioration section and the capacitance of the water tree deterioration section is Measuring the dielectric constant (ε _W ) of the water tree deteriorated portion by using the method.