JPH067144B2 - Automatic insulation diagnostic device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulation diagnostic device applied for non-destructive insulation test of various electric devices, power cables, and the like.

[Conventional technology]

Non-destructive insulation test methods for the purpose of analyzing insulation characteristics and determining insulation deterioration are roughly classified into a DC voltage method and an AC voltage method according to the type of probing voltage (applied voltage). The AC voltage method can measure not only the basic information for insulation diagnosis, such as capacitance and dielectric loss tangent, but also the scale of partial discharge that the DC voltage method does not. For this reason, commercial frequency AC voltage was used in the past, but in the case of large rotating machines and power cables, the electrostatic capacity is large, so the power supply capacity and test power supply device become large. It was difficult to operate. This was the reason why the non-destructive insulation test method was not widely used.

On the other hand, research using ultra-low frequency AC voltage such as 0.1 Hz has been promoted. In order for this method to be put into practical use, it is necessary to develop the following problems with power supply devices and the measurement method for parameters that represent the average magnitude of partial discharge.

[Problems to be solved by the invention]

A 0.1Hz modulated high voltage is generated by an electrically driven variable transformer and a step-up transformer for changing the commercial frequency voltage to a sine, which has been proposed as an ultra-low frequency AC high voltage power supply device of 0.1Hz. There is a method to obtain 0.1Hz alternating current for each half wave of this waveform by a changeover switch and a rectifier or by ring demodulation. Since this method uses multiple commercial frequency transformers,
If you want to increase the rated voltage, the weight is inevitably large.
Since it is equipped with an electric motor and crank, it is not small and light enough to be easily carried.

There is also a method of using two sets of a low voltage ultra low frequency voltage generating circuit and a DC high voltage generating circuit. One of them is JP-A-60-21996.
The ultra low frequency alternating current high voltage generator of the publication 5 generates an ultra low frequency alternating current voltage with an electronic circuit, and boosts each half wave by a positive and negative polarity high voltage direct current generating circuit, This is a method of obtaining an ultra-low frequency AC high voltage by alternately deriving the positive voltage and the negative voltage through a high voltage switch that is driven to open and close in synchronization with the high frequency AC low voltage. In this method, the DC high voltage generating circuit that is the main body of the device is 2
In the vicinity of the switching point of positive polarity and negative polarity, it is not possible to respond to the super low frequency alternating current of the input of the DC high voltage generation circuit due to the residual charge due to charging in the vicinity of the switching point of positive polarity and negative polarity. The output voltage waveform is distorted, and as a countermeasure against this, a discharge resistor with a small resistance value is connected in parallel with the DUT. The resistance value of this parallel resistor needs to be reduced in inverse proportion to the capacitance of the sample. The parallel resistance directly determines the rated capacity of the DC high voltage generation circuit, and the output voltage is 10 kV or more,
When the capacitance of the sample becomes 0.2 μF or more, the power supply capacity of the DC high voltage generating circuit becomes considerably large. It is difficult to apply to high voltage and large capacity. From the above, the realization of a small, lightweight, inexpensive, high-voltage, large-capacity power supply has become an important issue for the spread of nondestructive insulation testing.

Next, a problem to be solved by the present invention is a method of measuring a parameter indicating an average scale of partial discharge in the measurement of partial discharge using an extremely low frequency voltage as a probing voltage. In order to obtain parameters comparable to the partial discharge rate and the current increase rate in the case of conventional commercial frequency AC voltage, it is necessary to integrate the partial discharge pulse over time. could not. That is,
A detection resistor is used to extract the partial discharge pulse from the sample, but this detection waveform has a charging current component and a dielectric loss component. As a method of extraction, when integrated by using a high-pass filter as in the conventional case, the output becomes zero and the purpose cannot be achieved. For this reason, it is conceivable to use a microcomputer to measure the total discharge amount based on the discharge charge amount per discharge that is indirectly measured from the positive and negative pulse wave height values and the occurrence frequency. A threshold value is generally determined due to a noise problem of a circuit or the like, and a partial discharge pulse equal to or more than the threshold value is measured, and therefore, it is natural that an error occurs.

[Means for solving problems]

It is difficult to increase the voltage and capacity of the above ultra-low frequency AC power supply device, and it does not solve the widespread use of non-destructive insulation tests for large capacity turbine generators, turbine generators and power cables of 22 kV or more.

It is possible in principle to increase the voltage by developing the high-voltage element by applying the principle of the function wave generator (generally, the output voltage is 10V) that is widely used at present, but it is a special high-voltage element in view of the demand. Is expected to be industrially very difficult to develop.

The above is technically difficult in that the probing voltage is an alternating current waveform in which positive and negative polarities are alternately continuous.
On the other hand, in the measurement of partial discharge, the necessity of using an AC waveform as the probing voltage to solve the difficulty of device development was examined, and as a result, in measuring partial discharge, after discharging all the residual charge of the sample, It was discovered that applying negative polarity unipolar sine wave, unipolar triangular wave, etc. twice each time and measuring the partial discharge of each polarity would be practical for insulation diagnosis. Further, the unipolar waveform needs to be a sine wave or a triangular wave only in the partial discharge occurrence section, and the waveform in the non-partial discharge occurrence section may have distortion. As a result, a power supply device having only one set of a low-voltage function wave generation circuit and a DC high-voltage generation circuit, and a relatively small capacity, can be made compact, lightweight and inexpensive, and can contribute to the spread of nondestructive insulation testing. .

Means for solving the problems of the present invention will be described below. In order to simplify the explanation of the principle, the generation of partial discharge when an extremely low frequency sinusoidal AC voltage is applied in the case where there is one ideal void having a parallel gap in the insulator will be described with reference to FIG. Fig. 5 (A)
Is an explanatory diagram showing the state of occurrence of partial discharge when an extremely low frequency AC voltage (v) having a period (T) (frequency = 1 / T) which is a probing voltage is applied to the insulator, and the insulator is at time t. = 0,
Before v = 0, there is no residual voltage due to voltage application history,
Moreover, there is no delay in discharge. As shown in Fig. 5 (A), a positive wave of voltage (v) is applied to the sample from the origin (O), and when the partial discharge voltage (Vs) is reached, the first discharge occurs, Time (t ₁ ) is Is. Where Vm is the peak value of (v).

Fig. 5 (B) shows the state of partial discharge pulse generation as shown in Fig. 5 (A).
It is shown in relation to (v). A pulse current (▲ i ⁰ _d ▼) is generated at the time t ₁ described above, and is generated at each partial discharge generation interval voltage (Ea) after t ₁ . Ie voltage
When the rise of (v) is larger than Ea, the next discharge occurs. In FIG. 5, the time of occurrence of the second discharge is (t ₂ ). Ea is given by the following equation.

Ea ＝ Vs-Vr …………………… (2) where Vr is the residual voltage in partial discharge.

When the difference (α) between the peak value (Vm) of the voltage and the voltage (v) at the last discharge occurrence is α = Vm− (N ⁰ Ea + Vs) <Ea ……………… (3) Discharge for 1 / 4T is completed. N ^{0 in the} above equation is the number of discharges of the positive first wave.

This time, at the time (t _b ) of the voltage (Eb = Vs + Vr), which is a voltage (Eb) lower than the voltage at the time of the last discharge occurrence, the reverse polarity discharge occurs, and the pulse current (id) is generated. Where ▲ i ⁰ _d ▼ ＝
i. After the time (t _b ), the next discharge occurs each time the voltage (v) change reaches the above Ea, and the next discharge occurs, as shown in FIG. 5 (A).
When the voltage (β) is β = 2Vm− (N ⁻ Ea + Eb + α) <Ea ... (4), the negative discharge ends. N ^{− in the} above equation is a negative polarity, that is, the number of discharge occurrences of 1 / 4T to 3 / 4T. After that, according to the law of partial discharge, as shown in FIG. 5 (A), a positive discharge is generated at the time when the voltage changes by Eb from the voltage at the final discharge of negative polarity, and then the discharge of positive polarity is generated. ), A pulse current (▲ i ⁺ _d ▼) is generated. Where ▲ i
⁺ _d ▼ = i.

If α and β are ignored, N ⁰ , N ⁺ and N ⁻ are under the above conditions. Becomes

The pulse currents ▲ i ⁰ _d ▼, ▲ i ⁺ _d ▼, i in FIG. 5 (B) are exponential waves generally having a small wave tail decay time constant, and the partial discharge electric charge Q is obtained by time integration of these. If the positive polarity is Q ⁺ and the negative polarity is Q ⁻ , then Q ⁺ = Q ⁻ under the above conditions, but one side of the void is not an insulator but asymmetrical partial discharge such as metal. In this case, Q ⁺ ≠ Q ⁻ , and N ⁺ ≠ N ⁻ . In this sense, the probing voltage has conventionally been AC.

The principle of the present invention is shown in FIG.
The probing voltage is not a continuous AC voltage as shown in (A), but is a probing voltage having a positive polarity waveform and a negative polarity waveform as shown in FIG. 4 (a). Fig. 4
This will be described in detail using (a). The positive voltage (v) in the figure has the same waveform as the peak value (Vm) in the case of conventional alternating current, is applied to the sample from the origin (O), and the time (1/2
2T, T: One cycle when AC is applied), and the voltage application is temporarily stopped. The occurrence of partial discharge at this time is shown in Fig. 5 (b).
become that way. If the period of 1/2 cycle from the start of voltage application is the partial discharge measurement section (Tm), the number n ⁺ of positive polarity partial discharges is α = O. And is the same as N ^{0 in} the case of the above alternating current. The pulse current (▲ i ⁺ _d ▼) in FIG. 4 (b) is the same as the positive pulse current in the case of the alternating current. Therefore, the partial discharge electric charge Q ^{+ of} both is also the same.

Next, in order to measure the negative polarity partial discharge, the positive / negative polarity changeover switch is used to operate this to apply the negative polarity voltage (v ') because the power source is unipolar. After confirming that the following applied voltage history effect of voltage (v) has been lost, when the negative voltage (v ') of Fig. 4 (a) is applied for 1/2 cycle from time (o') Fig. 4 shows the occurrence of partial discharge in Fig. 4, and the number of negative partial discharge occurrences n ^- is at α '= 0. Becomes Here, V's and V'r are the partial discharge inception voltage and the residual voltage at the negative voltage.

The pulse current (i) is the same as the negative pulse current in the case of the alternating current. Therefore, the partial discharges of both are also the same.

If partial discharge ^{asymmetric, Vs ≠ V's, n +} ≠ n -,
Since Q ⁺ ≠ Q ⁻ , there is no inconvenience in insulation diagnosis if a voltage is applied for each positive and negative polarities instead of an AC waveform as described above and partial discharges of each polarity are measured. According to the present invention, unlike the case of the AC waveform, Vs and V's can be easily measured.

By setting the measurement time (Tm) between the 1/2 cycles of Fig. 4 (b), the voltage of the final discharge near the peak value of the positive / negative unipolar applied voltage was changed by Eb and E'b, respectively. The discharge pulse currents (i ′d) and (i ″ d) at this time are missing, but since they belong to Q ⁻ and Q ⁺ , respectively, from the above, there is no problem with missing.

Next, there is a problem that Eb and E'b are missing, and Vr and V'r are missing from this, but the partial discharge observed in actual electric equipment and power cables, etc. There is no single partial discharge in which the discharge start voltage and the residual voltage are Vs and Vr, respectively.
It is composed of multiple partial discharges, in addition, because of the irregularity of the discharge, even in the conventional AC method, even if the starting voltage of the reverse polarity discharge after the peak value has elapsed is measured, which partial discharge it belongs to, Since it is not always possible to determine, it was not included in the measurement target.

Since the measurement period (Tm) is 0 to 1/2 cycle, the probing voltage may be a sine wave or a triangular wave only during that period, and other than that, the waveform may be distorted. This is extremely effective in reducing the power supply capacity of the DC high voltage generating circuit (2), and making it small, lightweight and inexpensive, as described in the embodiments described later.

By applying the above-mentioned unipolar waveform probing voltage, the conditions for measuring the positive and negative partial discharges are as follows: before the voltage is applied, the insulation resistance, capacitance, dielectric loss tangent, etc. are measured. There is no history effect of the applied voltage. When a unipolar voltage according to the present invention is applied,
As a result, the history of the applied voltage before that resulted in a deviation in the number of partial discharges. For this purpose, in order to eliminate the hysteresis effect of the applied voltage, it is necessary to discharge the residual charges due to the applied voltage before that, and to apply the probing voltage after confirming that the residual charge is sufficiently discharged. In the present invention, a parallel resistor is provided in the device, the sample is automatically discharged from the time when it is connected, a voltage dividing resistor is provided at the lower end of the parallel resistor, and the residual voltage zero detector is provided. This makes it possible to measure partial discharge using a unipolar waveform probing voltage instead of the conventional AC. In addition, this parallel resistor maintains the waveform of the sine wave or triangular wave in the above measurement section (Tm), in other words, the parallel resistor for improving the output response characteristic to the input of the DC high voltage generation circuit (2) as described later. It also serves as a device, and the structure is simple without using a special high-speed switch or the like.

As a means to solve the following problems, only the partial discharge pulse is extracted from the current of the sample, and the principle of the method of measuring the parameter indicating the average partial discharge scale is described. The current when partial discharge occurs is shown in Fig. 4 (b).
In addition to the partial discharge pulse currents (▲ i ⁺ _d ▼) and (i), there are charging current components and dielectric loss components. These ultra-low frequency components are removed, and only partial discharge pulses are used in the high frequency range as in the past. The invention of extracting without using a filter is a phase inversion type operational amplifier and a low-pass filter provided in parallel with a sustain circuit that converts a current into a voltage using a detection resistor and keeps this detected voltage as it is. The partial discharge pulse can be extracted by synthesizing the output voltages and canceling out the charging current and the dielectric loss component of the ultra-low frequency sample. This enables time integration, and the total discharge electric power ΣQ of partial discharge.
n can be measured faithfully. With this invention, the average partial discharge rate and the partial discharge rate, which represent the average scale of partial discharge, became the basis for easily obtaining the average partial discharge rate.

The measurement of partial discharge is extremely important for insulation diagnosis of high-voltage equipment and power cables, and the invention relating to the solution to the problem has been described above with respect to the conventional technique. Has insulation resistance, capacitance and loss tangent. As long as it is an insulation diagnostic device, comprehensive measurement including these measurements is necessary. In the present invention, since the DC high voltage generating circuit is provided, it is easy to measure the insulation resistance from the low voltage to the high voltage region. Moreover, since the capacitance and the dielectric loss tangent are measured in the high voltage region because the capacitance and the dielectric loss tangent are based on the partial discharge, it is possible to evaluate the partial discharge by applying the probing voltage of the present invention. Only the value in the low pressure region needs to be measured. Since there is almost no voltage change in the low voltage region of capacitance and dielectric loss tangent, the size and weight can be reduced by measuring at a commercial frequency of 0.5 kV or less.

[Action]

According to the present invention, by providing a parallel resistor in parallel with the sample for discharging the residual charge of the sample before the partial discharge measurement, a low-frequency function wave generation circuit for generating an arbitrary waveform is provided. By using a unipolar high-voltage low-frequency power supply device with a DC high-voltage generation circuit, it is possible to measure the partial discharge for each positive polarity and negative polarity, which makes it possible to reduce the size and weight of the power supply device and reduce the price. It has a measuring circuit that faithfully measures the total amount of electric discharge and calculates the average partial discharge rate and partial discharge rate.

〔Example〕

FIG. 1 shows an embodiment of a circuit configuration of an insulation diagnostic device according to the present invention. The low-frequency function generating circuit section (1) for producing an arbitrary waveform is composed of an operating DC power supply (16), an output voltage setting circuit (17), and an arbitrary function wave generating circuit (18). The output voltage setting circuit (17) sets the peak value of the probing voltage of this device. The arbitrary function wave generation circuit (18) generates a waveform of an arbitrary frequency such as a unipolar ultra-low frequency sine wave, a triangular wave and a trapezoidal wave. The DC high voltage generation circuit (2) consists of a booster circuit (19) and a voltage doubler rectifier circuit.
It consists of (20). The polarity changeover switch (3) is a polarity changeover switch for measuring partial discharge of both positive and negative polarities on the sample (9) with the unipolar voltage generated by the DC high voltage generation circuit (2). is there. The parallel resistor (4) is a resistor for discharging the residual charge of the sample (9), and the residual voltage zero detection circuit (10) is provided from the voltage dividing resistor (5). The DUT (9) is connected to the probing voltage output terminals (7) and (8). The detection resistor (6) is a resistor for detecting a current based on partial discharge.

The partial discharge pulse extraction circuit (11) includes a preamplifier (21), an input waveform maintenance circuit (22), a phase inversion circuit (23), and a low-pass filter (2
4), (22) and (24) and is composed of a synthesis circuit (25) for summing the output voltages. The 3-mode integrator (12) is
It is an electronic integrator having three functions of sampling, holding and resetting.

The pulse measuring circuit (13) is for converting the partial discharge electric charge from the peak value of each pulse equal to or more than the threshold value, and measuring the time of occurrence or the applied voltage at the time of occurrence. Calculation result display recorder
(14) is the display / recording of the calculation result of the pulse measuring circuit (13), the partial discharge total discharge amount measured by the three-mode integrator (12), and the capacitance and probing voltage separately measured. The calculation, display and recording of the average partial discharge rate and the partial discharge rate are performed from the peak value. Control circuit
(15) is especially necessary when automating the device.The output of the zero residual voltage detector (10) of the DUT (9) allows positive and negative polarity of the probing voltage under the condition of zero residual voltage. After the determination, the operation of the positive / negative polarity changeover switch (3), the start of the function wave generation circuit (18) for generating the probing voltage, the sampling control of the three-mode integrator (12) are performed, and after one measurement, The reset control of the three-mode integrator (12) and the operation of the polarity changeover switch (3) are performed.

Next, the operation of the embodiment apparatus of the present invention having such a configuration will be described with reference to the operation explanatory diagram of the probing voltage generator of FIG. 2 and the operation explanatory diagram of the partial discharge pulse extraction circuit of FIG. The origin (0) in Figs. 2 and 3 is
The operation start time is shown, and 1 / 2T corresponds to a half cycle in the case of the conventional sinusoidal alternating current. FIG. 2A shows the input voltage of the DC high voltage generating circuit (2), in other words, the output voltage of the function wave generating circuit (18). FIG. 2 (B) shows the output waveforms of the output terminals (7) and (8), that is, the probing voltage of the present invention.
The waveform of (b) is shown. Output waveform of DC high voltage generator (2)
(B) generally responds faithfully up to the peak value of the input waveform (B), but when the capacitance C of the sample (9) is relatively large,
Waveform for waveform (a) from the time (t _c ) slightly after the peak value
As shown in (C), the waveform becomes distorted due to no response. This t _c is given by the following equation.

Where R is the resistance value of the parallel resistor (4).

Since the partial discharge generation section is 0 to 1 / 4T as described above, it is sufficient that the value from 0 to the peak value is a sine wave or a triangular wave. From this point of view, the waveform (b) of FIG. 2 (B) has no problem in insulation diagnosis. As a result of a detailed study, partial discharge may occur even after a little over 1 / 4T due to the discharge delay phenomenon depending on the insulation state. / 4T
+ 1 / 8T = 3 / 8T. Since it is a sine wave during this period, R
Is the capacitance C of the sample And need to.

The waveform (b) shows the decay of the exponential wave after t _c like the waveform (c), and the decay time constant is a maximum of 1.6 seconds from Eq. (10).

After checking the positive voltage probing voltage (b) and (c) with natural attenuation and checking with the residual voltage zero detector (10), switch the positive / negative polarity selector switch (3) to the origin (Fig. 2A) ( 0 ') input (a') with the same waveform as input (a).
By applying to (2), the negative probing voltage of the waveforms (b ') and (c') of FIG. 2 (B) can be obtained by the same operation as described above.

Next, apply the probing voltages (b) and (c) above to the sample (9).
The measurement of the average partial discharge rate and the partial discharge rate will be described with reference to the operation explanatory diagram of the partial discharge pulse extraction circuit in FIG. FIG. 3 (a) is a detection voltage waveform diagram of the detection resistor (6), in which the partial discharge pulse (P) is superimposed on the charging current and the dielectric loss component (F). FIG. 3 (b) shows an output voltage waveform when the above detection voltage is passed through the phase inversion circuit (23) and the low pass filter (24), and the above waveform (F) is a phase inverted waveform ( F ′), and the partial discharge pulse is the low-pass filter (23).
Indicates that it is significantly attenuated by. The output voltage of the waveform maintaining circuit (22), the phase inverting circuit (23), and the low-pass filtering circuit (24) is combined by a combining circuit (25), which is an adder, as shown in FIG. 3 (C). Thus, only the partial discharge pulse can be obtained as an output. In this way, since the pulse component is extracted without using the high-pass filter at all, the result of integrating the output of the synthesis circuit (25) by the three-mode integrator (12) is the total partial discharge electric power ΣQn. . The calculation result recording device (14) calculates the average partial discharge rate γ'and the partial discharge rate γ, respectively, using the following equations.

From the device of the embodiment of the present invention, the power supply device of the probing voltage may be unipolar and may have a sine wave or a triangular wave only between 0 and 3 / 8T.

When a series of sinusoidal alternating current such as 0.1 Hz is performed by a combination method of a function wave generating circuit and a DC high voltage generating circuit as in the past, in order to minimize the waveform distortion over the entire waveform, t _c → 1 / It is necessary to set it to 2T, and specifically, R is made as small as possible according to C. As a result, the rated current of the DC high voltage generating circuit I _R = V _R / R, (V _R = rated voltage)
Are increasing, and there are clear limits to the application of high voltage and high capacity test specimens. In the embodiment of the present invention, the high-speed and high-reliability positive / negative polarity changeover switch which is opened and closed in synchronization with the voltage of the function wave generation circuit is unnecessary. The high-speed positive / negative polarity changeover switch currently on the market has a vacuum switch structure with a maximum rated voltage of 25 kV.

In a comparative example of a power supply device having an output voltage of 10 kV and a maximum capacitance of 0.13 μF of the sample, the device of the embodiment of the present invention has both a price and a weight as compared with the conventional case of ultra-low frequency sine wave alternating current such as 0.1 Hz. It is 1 / 2.5 or less.

Further, in the device of the embodiment of the present invention, it is possible to easily manufacture an output voltage of 50 kV or more and an electrostatic capacity of 1 μF or more.

As a problem in measurement, in the case of a conventional AC, application of a probing voltage of 1.5 cycles, in other words, at 0.1 Hz, a series of partial discharge measurement is completed in 15 seconds, whereas in the embodiment apparatus of the present invention , The total measurement time is 10 seconds, but there is the trouble of temporarily stopping in the middle of the measurement of the positive and negative partial discharges, but by performing the arithmetic processing during this time, the memory capacity of the computer can be rather small. There are also features.

〔The invention's effect〕

As described above, the insulation diagnosis apparatus according to the present invention includes the parallel resistor with the DUT and the positive / negative polarity changeover switch, so that a set of arbitrary function wave generation circuit section and DC high voltage generation can be obtained. With a circuit configuration alone, a probing voltage for measuring partial discharge, which is important for insulation diagnosis, can be easily generated, and the provision of a partial discharge pulse extraction circuit enables faithful measurement of the total discharge electric charge of the partial discharge. It is lightweight, inexpensive and easy to handle, and is effective in popularizing non-destructive insulation tests.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
2 is an exemplary diagram of generation of a probing voltage in the above embodiment, FIG. 3 is an exemplary diagram of operation explanation of the partial discharge pulse extraction circuit in the above embodiment, and FIG. 4 is a unipolar sine according to the present invention. FIG. 5 is an illustrative view of a single partial discharge using a wave as a probing voltage, and FIG. 5 is an illustrative diagram of a conventional single partial discharge using a probing voltage of an ultra-low frequency alternating current. (1) is a low frequency function wave generating circuit, (2) is a DC high voltage generating circuit, (3) is a polarity change switch, (4) is a parallel resistor, (9) is a sample, (10) is Zero residual voltage detection circuit, (11) partial discharge pulse extraction circuit, (14) calculation result recording and display device, (15) control circuit, (22) input waveform maintenance circuit in partial discharge pulse extraction circuit, (23) ) Is also a phase inversion circuit, (24) is a low-pass filter circuit, and (25) is a synthesis circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A low-frequency function wave generation circuit and a DC high-voltage generation circuit for generating a unipolar high-voltage low-frequency, and a high-voltage low-frequency polarity for measuring a positive polarity and a negative polarity partial discharge. Positive / negative polarity changeover switch, parallel resistor for discharging the residual voltage of the sample before applying the voltage, partial discharge pulse extraction circuit for measuring partial discharge pulse, partial discharge And a circuit for calculating the generation scale of the automatic insulation diagnostic device. 2. A detection circuit for detecting that the residual voltage has become zero by also functioning as a parallel resistor for improving the response characteristic of the DC high voltage generating circuit to a low frequency function wave. Claim 1 characterized by having
The automatic insulation diagnosis device according to the item. 3. An input waveform maintaining circuit for inputting a detection voltage based on a partial discharge pulse to the partial discharge pulse extracting circuit, a phase inverting circuit for inverting a phase of an output of the input waveform maintaining circuit, and the phase inverting circuit. A low-pass filter having an output of the circuit as an input, and a synthesizing circuit for adding the output of the input waveform maintaining circuit and the output of the low-pass filter to each other. The automatic insulation diagnosis device according to the item.