JPH0467423B2 - - Google Patents

Description

Detailed Description of the Invention The present invention continuously monitors and measures whether or not an internal abnormality occurs in a high-voltage stationary electric appliance while the appliance is in operation or energized, and issues an alarm when an abnormality is detected. The present invention relates to a monitoring device that can take necessary countermeasures such as stopping operation.

Insulation deterioration due to local insulation breakdown as an internal abnormality in oil-immersed transformers and other high-voltage stationary electric appliances, that is, partial discharge, can progress to full-scale dielectric breakdown if it continues for a long time, causing large-scale damage to the electric appliance. It may lead to an accident. Therefore, it is necessary to continuously monitor the condition of electrical appliances, detect this partial discharge as soon as it occurs, and take necessary measures such as internal inspection of the electrical appliance to prevent accidents involving electrical appliances. In general, when detecting internal discharge in an electrical appliance, a monitoring device must have a function that can clearly distinguish between external discharge generated from power transmission lines, bushings, etc., or external noise such as switching noise and radio noise, and internal discharge in the electrical appliance. In addition to being able to discriminate these things with high accuracy, it is also required to be easy to handle and inexpensive.

Conventional technology for this type of device includes, for example,
No. 52-46431 is known, and this device detects internal partial discharges using two different physical quantities, electric pulses and ultrasonic pulses, and uses a method to distinguish between internal discharge pulses and external noise based on the correlation of their generation times. With this method, discrimination between internal discharge and external noise is incomplete, and what should be external noise may be determined to be internal discharge pulse. That is, all induced noise and external ultrasonic noise that enter when the gate pulse is open are determined to be internal discharges, and malfunctions caused by this become a problem. Japanese Patent Application Laid-Open No. 55-117421 is known as an improved device for this, and this device uses a plurality of ultrasonic detection elements to detect the presence or absence of a detection delay time difference between ultrasonic waves, thereby preventing malfunctions. The time difference between the ultrasonic waves is determined by a time counter and calculation by a microcomputer. However, this device requires an arithmetic circuit to calculate the measurement results of this counter circuit in addition to a counter circuit that counts the delay time of an ultrasonic pulse that operates simultaneously with the detection of an electric pulse. The means for detecting the time difference requires a complicated circuit, and there is a comparison/judgment section, etc., which naturally requires the use of a microcomputer, and as a result, the cost of the apparatus becomes high. In addition, the use of complex circuits and microcomputers not only poses difficulties in terms of maintenance, but also limits the installation location, making it particularly unsuitable for normal installations such as substations and outdoor distribution panels. There are drawbacks to substations, such as malfunction of circuits caused by switching surges generated by substations, and it is extremely difficult to take measures to prevent this.Also, inside outdoor panels, noise and temperature from the power supply that operates the equipment become a problem. This is because the rise, etc. requires more care than in a device equipped with a normal pulse circuit. If the device is installed in a monitoring shed, etc., the detection part and the judgment part are quite far apart, so optical cables must be used to transmit signals between them to prevent noise, which can significantly increase installation costs. There are also drawbacks.

SUMMARY OF THE INVENTION An object of the present invention is to provide an internal partial discharge monitoring device for high-voltage stationary electric appliances that eliminates the above-mentioned conventional drawbacks, has high discrimination accuracy, has fewer restrictions on installation locations, is easy to handle, and is inexpensive.

According to the present invention, the above-mentioned object is to provide a pulse control circuit that operates and outputs an electric pulse detected by an internal discharge electric detector provided in a bushing of a high-voltage stationary electric appliance, and a container wall of the electric appliance. and an ultrasonic detection circuit provided in each of a plurality of acoustic detectors installed at different positions of the acoustic detector for detecting the internal discharge as an ultrasonic pulse, the ultrasonic detection circuit being controlled by the pulse control circuit. A discriminating circuit comprising a pulse generation circuit and a logic circuit detects the relationship between the generation time and the ultrasonic pulse to determine whether the electric pulse is due to internal discharge or other causes. It can be achieved by

Embodiments of the present invention will be described below based on the drawings. FIG. 1 shows one embodiment of the present invention. In the figure, reference numeral 1 denotes a high-voltage stationary electric appliance such as an oil-immersed transformer or a sealed switchgear, and a high-voltage bushing 2 of the stationary electric appliance 1 is connected to a power transmission line 3. When a partial discharge occurs in the stationary electric appliance 1, a current pulse flows through the bushing 2, and an electric pulse appears on a detector (not shown) connected to the PD tap 4 of the bushing 2.
This electrical pulse to be detected is input to the partial discharge measuring device 5 via the cable 21a, where it is amplified and waveform-shaped and transmitted to the pulse control circuit 8 via the cable 21b. When the pulse control circuit 8 detects the input signal from the cable 21b, it immediately switches on the first and second pulse generation circuits 10a and 10.
b, 10c; Cables 31a, 3 send a control signal that makes 12 standby in an operable manner for a certain period tmax.
1b, 31c, and 31d, and the first pulse generating circuits 10a to 10c and the second pulse generating circuit 12 stand by for operation. At this time, the first and second pulse generation circuits 10a
~10c and 12 output circuits 26a, 26b,
26c; 25b are off, off, off and
It is set to on.

On the other hand, a plurality of acoustic detectors 6a, 6b, 6c such as ultrasonic microphones are installed at different positions on the tank wall of the stationary electric appliance 1, and each of the detectors 6a to 6c detects ultrasonic waves generated by partial discharge. The propagation time ta, tb,
are detected with a delay of tc, and each cable 22
The signals are input to pulse amplification/shaping circuits 7a, 7b, and 7c via a, 22b, and 22c. Pulse amplification/
The shaping circuits 7a to 7c transform the detected ultrasonic pulse into a rectangular wave with a pulse width tmin/2 and transmit it to the cable 23.
A, 23b, and 23c are used to output the signals. Here, tmax is the propagation time of the ultrasonic pulse determined by the structure of the tank of the stationary electric device 1 and the mounting position of the detectors 6a to 6c, and is the maximum delay time with respect to the electric pulse, and tmin is set as the minimum delay time. Therefore, the delay times ta, tb, and tc caused by the detectors 6a to 6c are tmin
It is within the range of ta, tb, and tctmax.
Now, pulse amplification by cables 23a to 23c.
When the outputs of the shaping circuits 7a to 7c are input to the first pulse generation circuits 10a to 10c that are waiting for operation,
This output changes from off to on, and the cable 26 is connected to the output side of the first pulse generation circuits 10a to 10c.
The first logic circuit 13 connected through a, 26b, and 26c has an input state of on or off.
Turns from off to on when the state exceeds the specified number of circuits.
The signal is then output to the cable 27. In other words, the ultrasonic pulse is output only when ta, tb, and tctmax are reached.

On the other hand, a second logic circuit 11 is connected to the pulse amplification/shaping circuits 7a to 7c via cables 24a, 24b, and 24c, and this second logic circuit 11 receives input from the pulse amplification/shaping circuits 7a to 7c. It determines whether or not certain ultrasonic pulses overlap (whether or not ultrasonic pulses occur simultaneously).The output changes from off to on only when they are input at the same time, and the second logic circuit In the second pulse generating circuit 12, which is connected to the second pulse generating circuit 11 by a cable 25a, when this input signal turns on, the signal changes from on to off and is output to the cable 25b. In the case of internal partial discharge, the acoustic detector 6
a, 6b, and 6c are provided, the inputs of the second logic circuit 11 are not input simultaneously;
Its output remains off, resulting in cable 25
The output of b remains on.

This can be seen from the output states of the first logic circuit 13 and the second pulse generation circuit 12, which operate in conjunction with the signal of the pulse control circuit 8 that operates in response to the detection of the electric pulse of partial discharge. It is possible to tell whether the cause is due to a partial discharge or something else. This is because the outputs of the first logic circuit 13 and the second pulse generation circuit 12 are both turned on due to the electric pulse detected by the partial discharge measuring device 5. ,
The logic circuit 14 outputs an output only when it is on, and it can be determined that there is an internal partial discharge, and all other states can be determined to be caused by external noise or the like. In other words, if the pulse control circuit 8, the first pulse generation circuits 10a to 10c, and the first logic circuit 13 simply determine whether the propagation times of the detected ultrasonic pulses are ta, tb, and tctmax, the induction cannot be performed. Since signals input at the same time, such as noise, are determined to be internal partial discharges, the second logic circuit 11 and the second pulse generation circuit 12 controlled by the pulse control circuit 8 This determines whether or not ultrasonic pulses occur simultaneously to prevent malfunctions.

Further, a cable 21d for a command signal is connected to the pulse control unit 8 to operate the recorder 18 when an input signal is received therein, and the recorder 18 connects a cable 21c to the partial discharge measuring device 5. The output signal of the pulse peak value holding circuit 9 connected through the cable 21g is taken in via the cable 21g, and the internal partial discharge determined by the logic circuit 14 is determined by the magnitude of the input signal corresponding to the magnitude of the partial discharge. It is designed to record the distinction between noise and the like. Note that the logic circuit 14 is connected to the first logic circuit 13 and the second logic circuit 13.
are connected to the respective output sides of the pulse generating circuit 12 via the cables 27 and 25b, and if the states of the input signals from the respective cables 27 and 25b are both on, this is an internal partial discharge as described above. Since this means that the output is
is turned on, and the recorder 18 is turned on via the cable 28a.
The signal is also input to the logic circuit 16 via the cable 28b. In addition, the logic circuit 16 has a level detection circuit 15 to which the output of the pulse wave height value holding circuit 9 is connected via a cable 21e, and only when the input signal thereof is equal to or higher than a set value, the output is turned on and the cable 21f is connected. input via The logic circuit 16 outputs only when the input from the level detection circuit 15, that is, the magnitude of the partial discharge is greater than a set value, and the input from the logic circuit 14, that is, when it is determined that it is an internal discharge. logic circuit 1
Reference numeral 17 provided at 6 is this output terminal, which is connected to a device for stopping the operation of the electric appliance 1 or issuing various other alarms in response to this signal.

Next, different embodiments of the present invention will be described based on the drawings. In each figure, parts corresponding to the embodiment shown in FIG. 1 are given the same reference numerals and omitted, and different parts will be explained with emphasis on. First, the difference between the embodiment shown in FIG. 2 and the embodiment shown in FIG. 1 is that the first pulse generating circuit 10
Third pulse generation circuit 40 corresponding to a to 10c
In order to delay the operation standby period of a to 40c by a certain period of time from the operation of the pulse control circuit 8, a third pulse generation circuit 40 is provided in place of the second pulse generation circuit 12. 40
is connected to the pulse control circuit 8 via the cable 31a,
Further, the pulse generating circuits 40a to 40c are connected by cables 31b, 31c, and 31d, respectively. The pulse generating circuit 40 is configured to generate a control rectangular wave pulse having a pulse width tmax - tmin after a certain period of time tmin from this input using the control signal from the pulse control circuit 8, and this rectangular wave pulse The signals are outputted to pulse generation circuits 40a to 40c via cables 31b to 31d, and pulse generation circuits 40a to 40c are kept operational and on standby for a time period tmax-tmin.

On the other hand, the ultrasonic pulses due to the partial discharge generated inside the electric appliance 1 go through the same process as the embodiment shown in FIG.
It is input to the pulse amplification/shaping circuits 7a to 7c with a delay of tc, and the pulse amplification/shaping circuits 7a to 7c convert it into a pulse with a pulse width tf (tf<tmin) and send it to the pulse generating circuit 40a via the cables 23a to 23c.
It will be output to ~40c. Here, tmin and tmax are the minimum and maximum delay times of the ultrasonic pulse propagation, which are determined by the structure of the tank of the electric appliance 1 and the mounting positions of the detectors 6a to 6c, as described above, and are the minimum and maximum delay times of the ultrasonic pulse propagation detected by the detectors 6a to 6c. The delay times ta, tb, and tc of the ultrasonic pulses are all tminta, tb,
It is related to tctmax.

With this, the pulse generation circuits 40a to 40c can
If there is an input from the pulse amplification/shaping circuits 7a to 7c during the operation standby period of the pulse generation circuit 40, this will be output and input to the first logic circuit 13, and the logic circuit 13 will be able to control the number of input channels. If there are inputs equal to or more than the preset number of channels n (nN) for N (N=3 in this embodiment), a pulse is output. That is, when the electric pulse detected in this way is an internal partial discharge of the electric appliance 1, a pulse is outputted to the output of the logic circuit 13. And cables 21a, 2
When electromagnetic induction noise of a certain level or higher is induced in this system due to a surge in signal lines such as 2a to 22c, output pulses are generated almost simultaneously in the pulse control circuit 8 and the pulse amplification/shaping circuits 7a to 7c. I will do it. However, this is the pulse generation circuit 40, and since a delay time tmin is taken before the pulse generation circuits 40a to 40c reach their operating time, due to these, the pulses generated in the pulse amplification/shaping circuits 7a to 7c are pulses. Generation circuit 4
It will disappear before the operations of 0a to 40c and will not be output from the logic circuit 13. Also,
Even if an external electric pulse that has entered from the power transmission line 3 is detected by the partial discharge measuring device 5, no ultrasonic pulse is generated within the electric appliance 1 at this time.
Therefore, since there is no input to the pulse amplification/shaping circuits 7a to 7c, the pulse generation circuits 40a to 40c do not generate pulses, and the logic circuit 13 does not output. Furthermore, in this embodiment, when a solid object collides with the electric appliance 1, since there is no electric pulse to be detected, the pulse control circuit 8 does not operate, and therefore the logic circuit 13 does not output.

Note that the pulse control circuit 8, the pulse peak value holding circuit 9 controlled by the pulse control circuit 8, and the logic circuit 1
The operations of the recorder 18 and the alarm circuit which are activated by the output of No. 3 are the same as those of the embodiment shown in FIG. 1, and their explanation will be omitted.

Next, differences between the embodiment shown in FIG. 3 and the embodiment shown in FIG. 1 and the embodiment shown in FIG. 2 will be explained. In FIG. 3, in the embodiment shown in FIG. 2, the pulse generation circuit 40 is used as a means for removing external noise such as electromagnetic induction, but in this embodiment, the output signal of the logic circuit 13 is used for the same function. For this purpose, logic circuits 13 and 14 corresponding to the embodiment of FIG.
A determination unit is constituted by a fifth pulse generation circuit 41, a pulse inversion circuit 42, and a logic circuit 14, which are connected to each other via cables 27a, 27b, and 27c, and the pulse generation circuit 41 therein is a pulse control circuit. 8 via cable 34a. If the electric pulse detected by this is caused by electromagnetic induction, the output pulse almost simultaneously with the operation standby signal sent from the pulse control circuit 8 to the pulse generation circuit 41 constituting the determination section is the first logic. circuit 1
3 to the pulse generation circuit 41. Therefore, if the operation time of the fifth pulse generation circuit 41 is set so that it operates after a delay time tmin after the input signal from the pulse control circuit 8 is received, all input signals within this time width are noises based on electromagnetic induction. , and this is not output from the logic circuit 14.

Furthermore, the embodiment shown in FIG. 4 will be compared with the embodiments shown in FIGS. 1 to 3, and the differences between the embodiment will be explained. First, a gate is provided in each of the ultrasonic detection circuits connected to the acoustic detectors 6a to 6c similar to those in the three embodiments described above, and this gate regulates incoming ultrasonic pulses. That's true. The ultrasonic detection circuit includes these cables 22a to 6c, including the aforementioned detectors 6a to 6c.
22c to pulse amplification circuits 43a, 43b,
43c, the aforementioned gates 45a, 45b, 45c connected to these amplifier circuits 43a-43c via cables 44a, 44b, 44c, and cables 46a, 46b, provided on the output side of these gates 45a-45c. 46c, and the cables 46a to 46c are connected to the sixth pulse generating circuit 47.
a, 47b, and 47c. Further, the gates 45a to 45c are connected to a pulse control circuit 8 and a sixth pulse generation circuit 47a to 47c, respectively, and control cables 36a, 36b, 36c;
They are connected via a, 39b, and 39c. Each of the gates 45a to 45c is opened immediately when an electric pulse is input to the pulse control circuit 8, and in this open state, the pulse generation circuits 47a to 45c are opened.
When an ultrasonic pulse delayed by propagation time ta to tc from the electric pulse from the detectors 6a to 6c is input to 47c, the pulse generation circuits 47a to 47c close at the same time as a rectangular wave pulse with a pulse width tw is generated at the time of detection. It is becoming more and more popular. As a result, only one pulse is input to the pulse generation circuits 47a to 47c, and the ultrasonic pulses are not detected repeatedly. Cables 48a, 48b, 4 are connected to the pulse generation circuits 47a to 47c.
8c to the first TTL circuits 49a, 49b,
49c is connected, and the TTL circuits 49a to 49c are connected to the first
Logic circuit 51 is connected, and TTL circuit 4
When the rectangular wave pulses from the pulse generation circuits 47a to 47c are input, the outputs of the circuits 9a to 49c immediately change from the L (Low) state to the H (High) state, and the logic circuit 51 receives a certain number of inputs. In this case, the output changes from the L state to the H state. On the other hand, a sampling gate 52 connected to the pulse control circuit 8 via the control cable 37 is connected to the output side of the logic circuit 51 via a cable 53a, and the output state of the logic circuit 51 is determined by the pulse control circuit 8.
, the gate 52 is opened twice at delay times t ₁ and t ₂ after the electric pulse due to internal partial discharge is detected, and the gate 52 is inputted to the binary counting circuit 54 connected to this via the cable 53b. Check the condition.
In other words, the logic circuit 51 at both times of delay time t ₁ and t ₂
If the output of the logic circuit 51 is in the H state or the L state, the output of the binary counting circuit 54 is in the L state, and if the output of the logic circuit 51 is between the delay times t ₁ and t ₂ , the output of the binary counting circuit 54 is is in the H state, and the ultrasonic pulses and electric pulses detected when the output state of the binary counting circuit 54 is in the L state are external noise, and the ultrasonic pulses and electric pulses detected when in the H state are It becomes possible to detect concomitant ultrasonic pulses that are likely to be internal partial discharges. The detection of the simultaneity of the ultrasonic pulses is carried out by the sixth pulse generation circuit 4.
Cables 55a, 55b, 55c for 7a to 47c
This becomes possible by inputting the signal to the second logic circuit 56 connected via the .

Note that the detection of incidental properties of ultrasonic pulses is
Generally, when a partial discharge occurs inside an electric appliance, an ultrasonic pulse is generated along with the electric pulse that occurs at the same time as the partial discharge occurs. However, the ultrasonic pulse propagates inside the appliance from the ultrasonic source and takes time to reach the relevant detection point on the appliance tank wall. And if this delay time is td, then
For example, td is the ultrasonic propagation speed in oil in an oil-filled electric appliance.
Since it is 1200 to 1800 m/sec, it depends on the size of the electrical tank, the installation location of the detector, and the geometric position of the partial discharge point.
In many cases, the delay is about 0.1 msec to 5 msec, and this delayed ultrasonic pulse is not detected within the aforementioned delay time t ₁ after the electric pulse is generated, but is detected within t ₂ , that is, t ₁ < td < t ₂ Detection of simultaneity between ultrasonic pulses means detecting whether ultrasonic pulses from each detector are detected at the same time. .

The second logic circuit 56 determines if the ultrasonic pulses are superimposed, i.e.
If induced noise etc. enter c or 44a to 44c at the same time, it will be detected at the same time by the pulse width tw of the rectangular wave pulse of the sixth pulse generating circuit 47a to 47c,
The output of the second logic circuit 56 changes from the L state to the H state only during the time when the respective rectangular wave pulses overlap, and the second TTL circuit 58 is connected to the second logic circuit 56 via a cable 57a. The output of
The state will change from the state to the L state. If ultrasonic pulses associated with internal partial discharges are detected, it is unlikely that they will be detected at the same time depending on the mounting positions of the detectors 6a to 6c and the partial discharge occurrence positions, and there will be a time difference between the ultrasonic pulses. It was hot,
The output of the second AND circuit 56 remains in the L state, and the output of the second TTL circuit 58 remains in the H state. That is, when the output of the binary counting circuit 54 is in the H state, it means that the ultrasonic pulse is detected between the delay times t ₁ and t ₂ from the electric pulse, and the output of the second TTL circuit 58 is When is in the H state, it means that there is no simultaneity of the ultrasonic pulses, and only in such a state, the cable 53c and the The output of the third logic circuit 59 connected through 57b changes from the L state to the H state, and when the output state of the third logic circuit 59 is in the H state, there is internal partial discharge, and when it is in the L state, there is no other discharge. A comprehensive judgment is made regarding the noise caused by
The signal cable 38 from the pulse control circuit 8 connected to the recorder 18 connected to the output side of the third logic circuit 59 via the cable 28a is connected to the output side of the third logic circuit 59 via the cable 28a. ₃
This is for data recording commands issued later. A level detection circuit 15 connected to the pulse wave height value holding circuit 9 via a cable 21e is connected to the partial discharge measuring device 5 controlled by the control cable 30a of the pulse control circuit 8 via a cable 21c.
The operation of the circuit from there to the alarm output terminal 17 via the logic circuit 16 is the same as in each of the above embodiments and will therefore be omitted.

In this embodiment, as described above, all the circuits are automatically reset to the initial state after an elapsed time _t4 after the pulse control circuit 8 detects the electric pulse. A pulse control circuit 8 that outputs a signal to open gates 45a to 45c of the ultrasonic detection circuit when a pulse is detected, and a pulse control circuit 8 that outputs a signal to open gates 45a to 45c of the ultrasonic detection circuit when a pulse is detected, and a pulse control circuit 8 that outputs a signal to open gates 45a to 45c of the ultrasonic detection circuit when a pulse is detected, and
tw square wave pulse is generated, and the gate 45a
The sixth pulse generation circuits 47a to 47c, which issue a signal to close 45c, make it possible to detect only one ultrasonic pulse. Also, the second logic circuit 56
A first logic circuit which detects the simultaneity of ultrasonic pulses with the second TTL circuit 58 and receives the outputs of the first TTL circuits 49a to 49c according to the signal from the pulse control circuit 8. A binary counting circuit 54 is provided which determines whether an ultrasonic pulse is detected within t ₁ to _{t 2 by} sampling the output state of 51 twice at delay times t ₁ and t 2 . Since the third logic circuit 59 is provided with the outputs of the counting circuit 54 and the second TTL circuit 58 as inputs, it is possible to comprehensively determine whether the noise is caused by an internal partial discharge or something else. It becomes possible.

Note that FIGS. 5 and 6 are time charts during the operation of the main circuits in this embodiment, respectively. FIG. 5 shows the case where a partial discharge occurs in the electric appliance 1, and FIG. This shows a case due to noise other than discharge, and since both correspond to the above, the explanation will be omitted, but by looking at the output state of the output signal 28a of the third logic circuit 59 at point P at time _t2 , If it is in the H state, it is an internal partial discharge, and if it is in the L state, it can be determined that it is due to other causes such as external noise.

As described above, according to the present invention, a circuit for determining the correlation between electric pulses and ultrasonic pulses, that is, whether a detected electric pulse is due to internal discharge or other noise, is connected to the pulse generating circuit and logic. Since it is composed only of circuits, the structure is simple, easy to handle, and inexpensive. This also means that installation costs are low because devices with restrictions on the installation environment, such as minicomputers and microcomputers, are not used, and when detecting ultrasonic pulses, it is easy to distinguish from both the concomitantness and simultaneity of the ultrasonic pulses. Therefore, it has high discrimination accuracy. Therefore, it makes a significant contribution in terms of cost and reliability improvement in preventive maintenance of high-voltage stationary electrical appliances.

[Brief explanation of the drawing]

1 to 4 are block wiring diagrams of different embodiments of the internal partial discharge monitoring device for high-voltage stationary electrical appliances according to the present invention, and FIGS. 5 and 6 show main parts of the embodiment of FIG. 4. These are operation time charts. FIG. 5 is a diagram showing the time when internal discharge is detected, and FIG. 6 is a diagram showing the time when noise etc. below the internal discharge is detected. 1... High voltage stationary electrical appliances, 2... Bushings, 4
...Electrical detector, 6a, 6b, 6c...Acoustic detector, 8...Pulse control circuit, 10a, 10
b, 10c; 12; 40a, 40b, 40c; 4
1; 47a, 47b, 47c...Pulse generation circuit, 11, 13...Logic circuit, 45a, 45b,
45c; 52...gate circuit, 49a, 49b,
49c; 58...TTL circuit, 51, 56...logic circuit, 54...binary counting circuit.

Claims (1)

[Claims] 1. A pulse control circuit that operates and outputs electric pulses detected by an internal partial discharge electric detector installed in the bushing of a high-voltage stationary electric appliance, and and an ultrasonic detection circuit provided in each of a plurality of acoustic detectors attached to each of the plurality of acoustic detectors for detecting the internal discharge as an ultrasonic pulse. a first pulse generation circuit provided corresponding to each of the ultrasonic detection circuits that outputs the ultrasonic pulse if inputted during the standby period;
a first logic circuit that outputs only when all of the outputs of the first pulse generation circuit are output during the standby period; and a first logic circuit that is provided so that a propagation time difference between the ultrasonic pulses is equal to or greater than a specified value. A detector is provided on the output side of each ultrasonic detection circuit consisting of an acoustic detector, and detects the presence or absence of simultaneous occurrence of ultrasonic pulse outputs from the detection circuit, and outputs only when they are not input at the same time. a second logic circuit; a second pulse generation circuit that is put on standby for a certain period of time by the output of the pulse control circuit and outputs only when the second logic circuit generates an output; and the first logic circuit; 1. An internal partial discharge monitoring device for a high-voltage stationary electric appliance, comprising a third logic circuit that determines that the electric pulse is an internal discharge only when both outputs from the second pulse generation circuit are received.