JPH0511911B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method and apparatus for diagnosing the insulation state of high-voltage electrical equipment that serves as a drive source for a main blower of a blast furnace, as well as various mechanical equipment and electrical devices. In particular, the present invention relates to an insulation diagnostic method for electrical equipment and a diagnostic device for improving insulation diagnostics.

(Prior art) Generally, when high-voltage electrical equipment related to a production line stops functioning due to winding failure such as deterioration of insulation, the production line will be out of operation for a long period of time.
There is a risk of significant damage. Therefore, in the case of high-voltage electrical equipment with advanced insulation deterioration that is nearing the end of its lifespan, it is desirable to replace it with a new equipment as soon as possible, but replacing the equipment costs an enormous amount of money. Therefore, it is necessary to appropriately and accurately diagnose the degree of insulation deterioration and take optimal measures according to the degree of insulation deterioration, such as varnishing, rewinding, or replacing with a new one, to improve economic efficiency. I'm getting old.

Therefore, conventionally, several diagnostic methods have been adopted from this point of view, such as the DC test method, dielectric loss tangent test method, AC current test method, and corona test method. is being diagnosed.

The DC test method calculates the polarization index P{P= from the insulation resistance value measured by a DC high voltage tester.
(Insulation resistance value 10 minutes after starting DC current) /
(Insulation resistance value 1 minute after the start of DC current flow)} is determined, and only moisture absorption deterioration is diagnosed based on this polarization index P. If moisture absorption deterioration occurs, the polarization index P
becomes smaller.

Next, the dielectric loss tangent test method diagnoses moisture absorption deterioration and void deterioration from the relationship between the applied AC voltage and dielectric loss tangent tan δ. When moisture absorption deterioration occurs, tan δ increases when voltage is applied, causing void deterioration. At a predetermined applied voltage, tan δ becomes small.

The AC test method diagnoses insulation from the relationship between the applied AC voltage and the magnitude of the detected current.When void deterioration occurs, the slope of the current increase curve changes due to corona discharge, causing a sudden increase. do.

The corona test method diagnoses insulation from the relationship between the applied AC voltage and the maximum discharge charge Qmax or total charge Qo. When void deterioration occurs, the maximum discharge charge Qmax or total charge Qo decreases. growing.

(Problems to be Solved by the Invention) However, all of the above four test methods require large-scale measurement equipment, require a long time for measurement, and are extremely expensive. Furthermore, there were problems such as lack of simplicity as a measuring device and poor reliability of the diagnostic results.

The present invention has been made in view of the above circumstances, and it is possible to easily and highly accurately diagnose the degree of insulation deterioration of electrical equipment, and to avoid long-term suspension of production line operation due to malfunction of electrical equipment. An object of the present invention is to provide an insulation diagnosis method for electrical equipment and a diagnostic device thereof, which can improve economic efficiency through appropriate maintenance according to the degree of insulation deterioration.

(Means for solving the problem) The insulation diagnosis method for electrical equipment according to the present invention detects leakage current of the electrical equipment with a sensor, and
From the output signal of this sensor, the phase angle of low frequency capacitance, high frequency capacitance, and leakage current is determined using an insulation constant calculation means having a high frequency bridge, and the hygroscopic constant obtained from the capacitance at these different frequencies is calculated as described above. Diagnosing the degree of insulation deterioration using high-frequency capacitance, a void constant obtained from the initial value of this high-frequency capacitance, and insulation deterioration constants such as a comprehensive deterioration constant obtained using this void constant and the leakage current, etc. It is.

Another invention, an insulation diagnostic device for electrical equipment, includes a sensor that detects leakage current in electrical equipment, and a leakage current signal detected by the sensor that determines the capacitance of different frequencies and the phase of the leakage current. Insulation constant calculation means for calculating insulation constants such as angles, etc., and insulation deterioration such as moisture absorption constants, void constants, and comprehensive deterioration constants obtained from these moisture absorption constants, void constants, etc., using at least the insulation constants calculated by the insulation constant calculation means. A pass/fail judgment is made based on a judgment reference value using an insulation deterioration constant calculation means for calculating a constant and at least one of the insulation deterioration constants calculated by the insulation deterioration constant calculation means, or insulation deterioration constant is determined based on insulation breakdown statistical data. The apparatus is equipped with means for obtaining the breakdown risk rate and the like and diagnosing the insulation deterioration state of electrical equipment.

(Function) Therefore, by using the method of the present invention as described above, after detecting the leakage current of an electrical device with a sensor, the capacitance of a different frequency, which is an insulation constant, and the leakage current can be determined from the output of this sensor. Find the phase angle of Then, using these insulation constants, the hygroscopic constant,
After obtaining insulation deterioration constants such as a void constant and a comprehensive deterioration constant, the degree of insulation deterioration is diagnosed by comparing with a determination reference value or dielectric breakdown statistical data.

Furthermore, by using the device of the present invention as described above, the detection signal from the sensor that detects the leakage current of electrical equipment can be insulated by the insulation constant calculation means, such as the capacitance of different frequencies and the phase angle of the leakage current. After calculating the constants, insulation deterioration constants such as a moisture absorption constant, a void constant, and a comprehensive deterioration constant are determined by an insulation deterioration constant calculation means using the insulation constants including the leakage current. Thereafter, the insulation deterioration constant calculated by this insulation deterioration constant calculating means is used to determine pass/fail based on the determination reference value, or the dielectric breakdown risk rate etc. are obtained from the insulation breakdown statistical data, and the insulation of electrical equipment is determined. This is to diagnose the state of deterioration.

(Example) Hereinafter, an example of the method of diagnosing insulation of electrical equipment and the apparatus for diagnosing the same according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing the overall configuration of the present invention. In this figure, reference numeral 11 is a sensor that detects leakage current of the electrical equipment to be diagnosed, and this sensor applies a predetermined voltage between the conductive part of the electrical equipment and the ground, and the insulation state of the electrical equipment at that time. It has a function to detect ₀ leakage current based on . 12 is a different frequency signal generating means,
A signal generating section 13, such as a multivibrator, which generates a plurality of preset frequency signals during insulation measurement, and a waveform shaping circuit 1, which converts a pulse signal from the signal generating section 13 into, for example, a sine wave signal.
From this waveform shaping circuit 14, different frequencies, that is, a high frequency signal and a low frequency signal, are applied to the electrical equipment through the sensor 11.

After the different frequency signal generation means 12 gives the different frequency signals to the electric devices as described above, the sensor 11 detects a leakage current _{of 0} and sends it to the subsequent insulation constant calculation means 15. The insulation constant calculation means 15 has, for example, a reverse shearing bridge, and calculates the different frequency capacitance of the ground insulator of the electrical equipment from the leakage current ₀ detected by the sensor 11, that is, the low frequency capacitance Cf1, and the high frequency capacitance Cf1. Insulation constants such as capacitance Cf2 and phase angle φ of leakage current are calculated. Note that this insulation constant includes ₀ leakage current taken in from the sensor 11, and
It differs depending on which insulation constant is used to calculate the insulation deterioration constant in the subsequent insulation deterioration constant calculation means 16. Note that this insulation deterioration constant calculation means 1
6 contains not only the insulation constant but also the calculation constant from the constant input circuit 17, that is, the initial value of the high frequency capacitance.
Cf2', the measurement temperature for correction t, and a unique constant k reflecting the insulation configuration of the electrical equipment are input. Therefore, if these calculation constants are unknown, empirical values estimated from the rated voltage, rated capacity, number of poles, type, etc. of the electrical equipment are input.

Therefore, the insulation deterioration constant calculation means 16
Calculate the insulation deterioration constant using the insulation constant and calculation constant. In other words, 1 of the insulation deterioration constant
The hygroscopic constant H _c is the low frequency capacitance Cf
1. Using the high-frequency capacitance Cf2 and the correction measurement temperature t, calculate H _c =t(Cf1-Cf2)/Cf2 by the formula (1). In addition, the void constant V _c as an insulation deterioration constant is determined by using the high frequency capacitance Cf2, its initial value Cf2', and the measurement temperature t for correction, V _c = t (Cf2 - Cf2') / Cf2' ... ( Obtained from the formula 2). Furthermore, the overall deterioration constant I _d can be increased as the insulation deterioration constant. This comprehensive deterioration constant I _d is determined not only by the moisture absorption constant H _c and the void constant V _c obtained by the above equation, but also by the leakage current ₀ and its phase angle φ obtained by the insulation constant calculating means 15, the constant k,
Using a etc., I _d =√() ² + ² + ( ₀ ) ² ...
It can be calculated using equation (3). The insulation deterioration constant determined as described above is sent to the dielectric breakdown risk calculation means 18. This dielectric breakdown risk calculation means 18 calculates the relationship between the number of insulation deterioration and the cumulative frequency of dielectric breakdown based on past dielectric breakdown results, that is, F(H _c )=∫ ^Hc f(H _c )dH _c ……(4) F (V _c )=∫ ^Vc f(V _c )dV _c ……(5) F(I _d )=∫ ^Id f(I _d ) dI _d ……(6) Calculate and register, and then perform the actual measurement. A dielectric breakdown risk rate is obtained by comparing the dielectric deterioration constant with the insulation deterioration constant at the time, and is displayed on the display section 19 together with the insulation deterioration constants H _c , V _c , and I _d . Therefore, in addition to the insulation deterioration constant, the display section 19 displays, for example, the potential dielectric breakdown risk factor F (V _c ) due to void deterioration, the current dielectric breakdown risk factor F (I _d ), and the like. Therefore, the degree of insulation deterioration of the electrical equipment is diagnosed based on the level value displayed on the display unit 19.

Next, conventional diagnosis results and diagnosis results according to the present invention will be specifically explained. FIG. 2 is a diagram in which the insulation deterioration status of high-voltage motors A to D was investigated using the conventional Megger method. In the figure, the horizontal axis is time (t),
The vertical axis shows the insulation resistance value MΩ. The resistance value of each of the motors A to D decreased with the passage of time, gradually decreasing from a "good region" to a "caution region" to a "defective region", and finally led to dielectric breakdown. However, as shown in A and B in the figure, the resistance values of motors B and C suddenly decrease over a certain period of time, and comparison with other diagnostic results described later does not accurately indicate the state of insulation deterioration.

On the other hand, for example, by detecting leakage current ₀ that changes based on the insulation state of electrical equipment, we can calculate the change in capacitance increase rate C ₀ shown in Figure 3 and the change in dielectric loss factor T _x shown in Figure 4. In short, the deterioration is relatively constant, and it is estimated that there is a high correlation with the deterioration. However, if insulation deterioration progresses significantly, the C ₀ value is expected to increase as the insulation deteriorates due to the relationship between each phase component in the leakage current, but the T _x value may conversely decrease. Therefore,
The present inventors investigated the relationship between C ₀ value, _T
When the frequency-dielectric loss factor T _x characteristics shown in FIG. 6 were investigated, it was found that when the deterioration progressed significantly as predicted above, C ₀ increased and T _x decreased.

Therefore, in the present invention, the leakage current is measured by applying different frequency signals to the electrical equipment to be diagnosed, and the _capacitance is determined from the leakage current for each frequency. The overall deterioration constant I _d shows the transition as shown in the figure, and the 8th
The trend is shown in the figure. Therefore, even when insulation deterioration has progressed significantly, the diagnosis means according to the above embodiment can more accurately diagnose the degree of insulation deterioration without causing a diagnosis error.

Note that the present invention is not limited to the above embodiments, and can be implemented with various modifications. For example, as shown in FIG. 9, a quality judgment circuit 21 is provided only on the output side of the insulation deterioration constant calculation means 16, or on the output side of the insulation deterioration constant calculation means 16 and the insulation breakdown risk factor calculation means 18.
and a display section 22 may be provided to compare the insulation deterioration constant or dielectric breakdown risk rate with criterion values such as good, caution, and defect, and display the comparison status on the display section 22 to diagnose the degree of insulation deterioration. . Furthermore, in addition to the quality determination result, the insulation constant may also be displayed on the display section 23.

(Effects of the Invention) As explained above, according to the method of the present invention, leakage current is measured by applying different frequency signals to electrical equipment to be diagnosed, and low-frequency capacitance, high-frequency capacitance, and leakage current are measured. Insulation constants such as phase angle are determined, and insulation deterioration constants such as moisture absorption constant, void constant, and total deterioration constant are determined based on the insulation constants obtained using these different frequency signals. environmental conditions (e.g. temperature, humidity, etc.)
Regardless of the situation, it is possible to diagnose with high accuracy without making a diagnosis error, and therefore, based on this diagnosis result, it is possible to avoid long-term shutdowns of the production line, and to improve economic efficiency by appropriately performing maintenance according to the degree of insulation deterioration. A method for diagnosing insulation of electrical equipment can be provided.

Further, according to the device of the present invention, not only can the degree of insulation deterioration of electrical equipment be diagnosed easily and with high accuracy, but also it can be realized in a compact size. Therefore, diagnosis results can be obtained easily and with high accuracy before electrical equipment stops functioning due to insulation deterioration, making it possible to prevent long-term shutdowns of production lines and to take appropriate measures depending on the degree of insulation deterioration. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram illustrating an embodiment of the insulation diagnosis method and its diagnostic device according to the present invention, Fig. 2 is a characteristic diagram showing conventional diagnosis results, and Figs. An experimental characteristic diagram of the realization process, FIGS. 7 and 8 are characteristic diagrams for explaining the effectiveness of the present invention, and FIG. 9 is a schematic configuration diagram for explaining another embodiment of the present invention. . 11...Sensor, 12...Different frequency signal generation means, 15...Insulation constant calculation means, 16...Insulation deterioration constant calculation means, 17...Constant input circuit, 18...
...Dielectric breakdown risk calculation means, 19...Display section, 2
1... Quality judgment circuit, 22, 23... Display unit.

Claims (1)

[Claims] 1. Leakage current of electrical equipment is detected by a sensor, and low-frequency capacitance, high-frequency capacitance, and leakage current are calculated from the output signal of this sensor using insulation constant calculation means having a high-frequency bridge. After determining the insulation constant consisting of the phase angle of the leakage current included, the moisture absorption constant is determined from the capacitance of these different frequencies, and the void constant is determined from the high frequency capacitance and the initial value of this high frequency capacitance. A method for diagnosing insulation of electrical equipment, characterized in that the degree of insulation deterioration is diagnosed by determining a comprehensive deterioration constant using the moisture absorption constant, the void constant, the leakage current, and the phase angle of the leakage current. 2. A sensor for detecting leakage current of electrical equipment; and insulation constant calculation means for calculating an insulation constant consisting of different frequency capacitance and phase angle of the leakage current including the leakage current from the leakage current signal detected by the sensor; Using the insulation constant obtained by this insulation constant calculation means, in addition to the hygroscopic constant and the void constant, the overall deterioration constant is calculated using the hygroscopic constant, the void constant, the leakage current, and the phase angle of the leakage current. A deterioration constant calculation means and the overall deterioration constant obtained by the insulation deterioration constant calculation means are used to make a pass/fail judgment based on the judgment reference value, or past insulation breakdown statistical data and the moisture absorption constant, void constant, and overall and means for diagnosing the insulation deterioration state of the electrical equipment by determining the dielectric breakdown risk rate based on the deterioration constant.