JPS6326609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a device for monitoring partial discharges inside sealed high-voltage equipment, particularly for monitoring partial discharges occurring inside the equipment during actual operation of transformers, etc., by detecting electrical and acoustic noise outside the equipment. This invention relates to improvements in discriminating and monitoring devices.

In high-voltage stationary electrical equipment, especially oil-immersed transformers and reactors, if a partial discharge occurs due to a local insulation abnormality during actual operation, this may trigger a serious accident such as insulation breakdown. Therefore, it is desired to develop a preventive maintenance device that can accurately detect the occurrence of this local insulation abnormality at an extremely early stage. In addition, this type of equipment is generally installed outdoors in close proximity to transformers, etc. within the premises of substations and power plants, and as a result, it is possible to prevent airborne corona discharge from high-voltage power transmission lines connected to the equipment, and lightning strikes. Induced voltage or opening/closing surges of circuit breakers, etc. may affect the pulse transmission circuit of the monitoring device as electrical noise, or rain or other damage may occur on the container of the monitored device.
Acoustic noise may be detected by the discharge sound detection element due to foreign object sounds caused by hail, sand, etc. hitting the discharge sound detection element. It is desired that the monitoring device does not malfunction even in the presence of these electrical noises and acoustic noises.

Such a device is known, for example, from Japanese Patent Laid-Open No. 117421/1983. That is, a time counter that starts counting time when a discharge pulse is detected by the electrical detection element is provided corresponding to each of the plurality of discharge sound detection elements. It is set to stop time counting when a sound is detected, reads the time counted by each time counter for each discharge sound detection element, and determines whether all of these times are within a predetermined time. If the number of detected discharge sounds that satisfy the above conditions is less than a predetermined number in the majority condition satisfaction determination section, it is determined to be noise and a printout to that effect is printed out. If the number exceeds a predetermined number, the sound is guided to a sound-to-sound time difference determining section, and if there is no time difference between the sounds, it is determined to be electrically induced noise and a printout to that effect is printed out. When the time difference determination section confirms the time difference, it is determined that it is an internal discharge in the device, and a signal to stop the device is issued via the command center, and the signal is sent to the calculation section to calculate the location of partial discharge occurrence. .

In the above, the predetermined time is the maximum and minimum range of the discharge sound detection delay time determined by the size of the monitored equipment, the mounting position of the discharge sound detection element, the sound propagation speed of the insulating medium and iron plate, etc. If the delay time of the detected acoustic output is out of the above range, it is determined to be electrical or acoustic noise from outside the device, and is identified as partial discharge inside the device.

Further, external airborne corona, opening/closing surge, etc. induced into the signal transmission circuit of the monitoring device generally have no time delay and can therefore be identified by the sound-to-sound time difference discriminator. However, under weather conditions where external air discharge frequently occurs in power transmission lines connected to the device under test, and where the device is frequently exposed to rain, hail, sand, etc., electrical pulses may be detected and There is a high risk that acoustic outputs with time differences will be detected and these electrical and acoustic noises will be mistaken for internal discharges in the device.

On the other hand, when a partial discharge occurs inside oil-filled insulated equipment, the ultrasonic waveform detected by the discharge sound detection element is generally known to exhibit the characteristic pattern shown in Figure 1 (1966 Institute of Electrical Engineers of Japan Tokyo Branch Tournament No.
131). That is, after an electric pulse is detected due to partial discharge inside the device, a sound wave W1 with a small amplitude is detected with a delay of t1 time, and then a sound wave W2 with a large amplitude and reduced vibration is detected with a delay of t2 time, and a sound wave W2 with a large amplitude is detected as a pair with the sound wave W1. Detected without.

Figure 2 illustrates the reason for the above. In the figure, 1 is an oil-immersed transformer winding, 2 is an airtight container, 3 is a discharge sound detection element such as an ultrasonic microphone attached to the outer wall of the airtight container 2 at point A, and now the X point of winding 1. Assume that a partial discharge occurs at point X and discharge sound is radiated around point X. At this time, the discharge sound detection element 3 has a path that propagates through the transformer oil from point X and enters the container wall at point A, and a path that enters the container wall at point B, which is the shortest distance from point It is conceivable that the discharge sound is detected through two types of propagation paths: a path where the discharge sound is transmitted and detected at point A;
Generally, the propagation speed of sound is approximately 1,500 m/s in oil and approximately 5,000 m/s in steel plate, and the arrival time varies depending on the material of the sound propagation path. The W2=X→A path is called direct sound, and the W1=X→B→A path is called container-borne sound.In this case, the propagation distance of container-borne sound is longer than that of direct sound. Due to the influence of the material of the propagation path, the propagation time is t2 hours for direct sound and t1 time for vessel-borne sound, and the delay time of vessel-borne sound is generally shorter. However, if the discharge sound detection element were placed at point B in FIG. 2, only direct sound would be detected. Furthermore, the difference in amplitude between direct sound and vessel-propagated sound can be explained by the large loss of acoustic energy during vessel propagation. In this way, when partial discharge sound inside the equipment is detected by a discharge sound detection element attached to the container wall, it is often detected as a pair of sound waves consisting of the container propagating sound and the direct sound. Since only the vessel propagating sound is detected in the detection waveform when an object hits, internal partial discharge sound and acoustic noise can be discriminated from the difference in waveform. In the case of the above-mentioned known example, the characteristics of the acoustic waveform described above are not considered, and the focus is only on the delay time of the sound wave with respect to the electric pulse. Therefore, for example, the device is set to make a determination based on the delay time of the sound propagating through the container. In this case, it becomes impossible to locate the position where a partial discharge occurs, and there is a risk that a partial discharge may be mistakenly determined to be noise even though it actually occurs.

The present invention eliminates the drawbacks of the prior art mentioned above, and
It is an object of the present invention to provide a partial discharge monitoring device that can more accurately distinguish between acoustic noise caused by rain, hail, sand, etc. hitting a container and internal discharge sound.

According to the present invention, the above object has been achieved by the following configuration. A pulse generation circuit is provided corresponding to each of the plurality of discharge sound detection elements,
At the same time as the electric pulse is detected, the pulse generation circuit enters the standby state for a predetermined period of time, and the direct sound and container propagation sound transmitted from each discharge sound detection element to the pulse generation circuit within this predetermined period reach a predetermined threshold value. The first and second pulse signals each having a predetermined pulse width are emitted at each point in time when the pulse width is exceeded, and the existence of a non-overlapping time of the first and second pulses is detected for each pulse generation circuit. When a plurality of pulse matching circuits generate output signals, and a predetermined number of pulse matching circuits or more output signals from the pulse matching circuits, it is determined that a partial discharge has occurred.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of the present invention, and is an example of an oil-filled electrical appliance. In the figure, 5 is, for example, an oil-immersed transformer, 6 is a grounded closed container, and the high voltage winding of the transformer is grounded by a grounding wire 7. Reference numeral 8 denotes an electric pulse detection element whose one end is grounded to the ground line 7 and magnetically coupled to the ground line. When a partial discharge occurs inside the transformer 5, an electric pulse appears on the electric pulse detection element 8 at the same time. This electric pulse is input to the partial discharge detector 9 via the cable 8a, where it is amplified and shaped.
a to the pulse control circuit 10. Upon receiving an electric pulse, the pulse control circuit 10 immediately controls the pulse generation circuits 41, 42, 43 for a certain period of time.
A control pulse is output to the cable 10a to put the device in a standby state for tmax, and if an electric pulse is detected again during the tmax time, a prohibition circuit is provided that does not generate the control pulse again, and a reset signal is generated after the tmax time. and a reset signal generation circuit. Reference numerals 21, 22, and 23 are discharge sound detection elements installed at different positions on the outer wall of the transformer sealed container 6, which convert the discharge sound into corresponding electrical outputs and connect the cables 21a and 22, respectively.
It is transmitted to amplification circuits 31, 32, and 33 via a and 23a. The amplifying circuit amplifies the output of the discharge sound detection element to a predetermined size necessary for processing by the pulse generating circuit, and transmits the amplified output to the respective pulse generating circuits via cables 31a, 32a, and 33a. Here, the standby time tmax of the pulse generation circuit depends on the dimensions of the transformer sealed container 6 and the discharge sound detection elements 21, 22, 23.
The maximum propagation time is determined by considering the installation position of the transformer and the discharge sound propagation speed inside the transformer and on the vessel wall.
Acoustic output with a delay time exceeding tmax is determined to be acoustic noise and is excluded from the monitoring target because the pulse generation circuit does not operate.

The pulse generating circuit 41, for example, is composed of a pair of comparators and a rectangular wave pulse generating circuit, and the pair of comparators has amplitudes V1 and V of the vessel propagating sound W1 and the direct sound W2 of the discharge sound detection waveform shown in FIG.
Corresponding to 2, each threshold value is set in consideration of the amplification rate of the pulse amplifier, and when an acoustic input exceeding each of the above two thresholds is received, a signal is sent to the rectangular wave pulse generation circuit. Transmit. The square wave pulse generation circuit determines the time the circuit is in standby mode based on the control signal using electric pulses.
When a pair of signals is input from the comparator within tmax, first and second rectangular wave pulses are generated based on the signals, and the first and second rectangular wave pulses are sent to the pulse comparison circuit 51 via cables 41a and 41b. 2
transmits a square wave pulse. Here, the time width tp1 of the first rectangular wave pulse is the maximum value of the difference in propagation time between the vessel propagating sound and the direct sound (usually 0.05 ms to 1 ms).
tmax), or it is set to rise at the same time as the container propagation sound is detected and fall at tmax. Further, the fall time of the second rectangular wave pulse is equal to the fall time of the first rectangular wave pulse, and the second rectangular wave pulse is set to rise simultaneously with the detection of the direct sound. Therefore, when an internal partial discharge as shown in Fig. 1 is detected, the first rectangular wave pulse corresponding to the vessel propagation sound W1 is generated with a delay of t1 after the electric pulse is detected, and then t2
A second rectangular wave pulse corresponding to the direct sound W2 is generated after a time delay, but the time width of the second rectangular wave pulse is (t2
-t1) time becomes shorter.

The first and second rectangular wave pulses generated as described above for each of the plurality of pulse generators 41 to 43 are transmitted to pulse matching circuits 51, 52, and 53, respectively, and It is checked whether there is a non-overlapping portion in the time widths of the two rectangular wave pulses. That is, each of the pulse matching circuits 51 to 53 is composed of an exclusive logic circuit and a monostable multi-circuit, and when the pulse widths of the first and second rectangular wave pulses have a non-overlapping time due to a difference in propagation time, The exclusive logic circuit outputs a rectangular wave pulse with a time width corresponding to the non-overlapping time, and the monostable multi-circuit generates a rectangular wave pulse with a time width tp2 unrelated to the non-overlapping time, and the cables 51a, 52a,
The signal is input to the determination circuit 60 via 53a. The determination circuit 60 includes one AND circuit into which all the output signals of the collation circuits 51 to 53 are input, and this AND circuit.
It consists of a monostable multi-circuit that outputs an output signal for a predetermined time tp3 from the time when the output of the AND circuit is output regardless of the time width of the output pulse of the circuit, and each of the matching circuits 51 to 53 has a first and second It detects the rectangular wave pulse of transmit signals to. Reference numeral 71 is an output terminal of the output circuit, and this output signal is used to stop the operation of the transformer 5, etc., and to which various other alarm devices and recording devices are connected.

Note that in the above explanation, the determination circuit 60 assumes that the outputs of the pulse comparison circuits 51 to 53 are both the first and second
An example is shown in which the first and second rectangular wave pulses are composed of a rectangular wave pulse, and only when there is a non-overlapping time between the first and second rectangular wave pulses, this is determined to be an internal discharge of the device and an output signal is transmitted to the output circuit 70. However, if the internal discharge occurrence position of the device and the installation position of the discharge sound detection element meet certain conditions, it is assumed that the container propagated sound may not be detected.
0 is composed of multiple circuits and monostable multi-circuits, and the output of a predetermined number or more of pulse matching circuits is the first
and a second rectangular wave pulse and have a non-overlapping time, the configuration may be such that this is determined to be a partial discharge inside the device.

Further, the determination circuit 10 puts the pulse generation circuits 41 to 43 into a standby state by a control pulse with a time width tmax that is generated simultaneously with the detection of the electric pulse, so that the detection sound of the discharge sound detection elements 21 to 23 has a delay exceeding the above tmax time. An example has been described in which if a noise is detected, it is determined to be acoustic noise, and the pulse generation circuit does not operate so that it is excluded from the monitoring target. It is also possible.

FIG. 4 is a time chart in an embodiment of the present invention, and is an example when an internal discharge of the device is detected. In the figure, 9a is the electric pulse detection waveform of the partial discharge detector 9, and 31a, 32a, 33a are the discharge sound output waveforms of the amplifier circuits 31 to 33, and the electric pulse 9a is
Ultrasonic sound consists of vessel propagation sound that is detected with a delay of ta1, tb1, and tc1 hours, and direct sound that is detected with a delay of ta2, tb2, and tc2 hours after the detection of For example,
The internal discharge condition of tmax>ta2>ta1 is satisfied. 41a to 43b are pulse generation circuits 41 to 4
This is a time chart of the output pulse of 3, and 41
a, 42a, 43a are the first rectangular wave pulses generated in response to the vessel propagation sounds of the discharge sounds 31a to 33a, and 41b, 42b, 43b are the second rectangular wave pulses generated in response to the direct sound. be. 51a-5
3a is the output pulse of the pulse matching circuit, for example, the first
square wave pulse 41a and second square wave pulse 41
The non-overlapping time (ta2-ta1) of b is detected and a rectangular wave pulse 51a having a predetermined pulse width tp2 is output. The pulse 60 is the AND of the judgment circuit 60
This is the output waveform of the circuit, and its pulse width corresponds to the overlapping time of the rectangular wave pulses 51a to 53a. Therefore, the pulse width of the pulses 51a to 53a is assumed to be long enough to ensure that their mutual overlapping time does not disappear. It can be decided. 60a is the output pulse waveform of the determination circuit 60.

The operation of the monitoring device according to the embodiment of the present invention and its time chart when an internal discharge of the device is detected has been explained above. In the case of acoustic noise, these acoustic noises propagate through the wall of the container and reach the discharge sound detection element, so that the container propagated sound is detected alone. FIG. 5 is a time chart for such acoustic noise, and is an example of a case where acoustic noise is detected as a loud sound that exceeds the two-step threshold of the pulse generation circuit. Assume that an electrical noise 9a is detected now, and acoustic noises 31a, 32a, and 33a are detected after a delay of time t11, t12, and t13. Since the amplitude of the pulse exceeds the two-step threshold, each pulse generating circuit has 41a and 41.
As shown by b, first and second rectangular wave pulses with a delay time t11 and a pulse width tp1 are generated simultaneously.
These square wave pulses are checked for non-overlapping time in a pulse matching circuit, but since the delay times of the first and second square wave pulses are both equal to t1, there is no non-overlapping time, so the pulse The verification circuit identifies it as acoustic noise and excludes it from monitoring.

Next, if the acoustic noise is at a level that exceeds the lower threshold of the two thresholds and is below the higher threshold, the pulse generator generates a single rectangular pulse. However, at this time, the exclusive logic circuit incorrectly judges that there is a non-overlapping time. Although this point was not mentioned in the explanation of the embodiment shown in FIG. 3, a switching circuit is added that makes the output circuit conductive only when a pair of discharge sounds is input to the pulse comparison circuit, and this eliminates the above-mentioned error. It is configured so that there is no judgment. Furthermore, when the aforementioned electrical noise enters the discharge sound detection element and its signal transmission circuit, the noise appearing in the pulse generation circuit is determined to be noise by the pulse matching circuit because there is no time difference.

As described above, according to the present invention, when a partial discharge generated inside an electrical equipment to be monitored is detected by a plurality of discharge sound detection elements installed at different positions in a sealed container of the electrical equipment, the amplitude and propagation are Focusing on the fact that a pair of detection waveforms consisting of container propagation sound and direct sound that differ in time are often obtained, each discharge sound detection element has a predetermined pulse width when two thresholds are exceeded. a plurality of pulse matching circuits that detect the presence of a non-overlapping time between the first and second rectangular wave pulses and generate an output signal; and a determination circuit that determines that a partial discharge has occurred within the monitored device when the output signal from the pulse verification circuit is received from a predetermined number or more of the pulse verification circuits, and the monitoring operation is performed when an electrical pulse is detected. The configuration includes a determination circuit that generates a control pulse that repeatedly operates every time an electric pulse is detected for a predetermined period of time tmax, so that the acoustic detection waveform of partial discharge inside the monitored equipment can be As a result, various noise levels such as aerial discharge noise of power transmission lines, lightning discharge noise, switching noise, and foreign object noise due to flying hail and sand dust have been improved. We have been able to provide a partial discharge monitoring device that can accurately detect internal discharges in electrical equipment without causing malfunctions due to the above-mentioned external noise in power plants and substations with high levels of noise. Furthermore, since the device of the present invention is constructed using a relatively simple circuit without using special circuits, microcomputers, minicomputers, etc. that are susceptible to external noise, it is resistant to abnormal voltages such as induced lightning surges and switching surges. It has the advantage of being less likely to malfunction or break down, has excellent long-term reliability, and can be manufactured at low cost.

The present invention applies not only to oil-filled transformers as explained in the above-mentioned embodiments, but also to parts of high-voltage stationary electrical equipment such as oil-filled actors, oil-filled instrument transformers, gas-insulated sealed switchgear, gas-insulated conduit aerial cables, etc. Applicable to discharge monitoring equipment.

[Brief explanation of the drawing]

Figure 1 is a mock diagram of a known internal discharge sound detection waveform.
Figure 2 is a diagram of the discharge sound propagation path inside a sealed electrical appliance, Figure 3
FIG. 4 is a block diagram showing an embodiment of the present invention, FIG. 4 is a time chart of various pulses in the embodiment of the present invention, and FIG. 5 is a time chart of various pulses with respect to noise in the embodiment of the present invention. In the figure, 1...Transformer winding, 2, 6...Airtight container, 7...Grounding wire, 8...Electric pulse detection element, 9...Partial discharge detector, 10...Control circuit,
3, 21, 22, 23...discharge sound detection element, 3
1, 32, 33... Amplifying circuit, 41, 42, 43
... Pulse generation circuit, 51, 52, 53 ... Pulse verification circuit, 60 ... Judgment circuit, 70 ... Output circuit, 71 ... Output terminal.

Claims (1)

[Claims] 1. An electric pulse detection element that detects an electric pulse appearing at an external terminal of an electric device due to a partial discharge generated in the electric device, and an electric pulse detection element that is attached to a wall of a container housing the electric device at different positions to detect a partial discharge. a plurality of discharge sound detection elements for detecting accompanying acoustic pulses, a control circuit for generating a control pulse when an electric pulse is detected by the electric pulse detection element, and a control circuit provided corresponding to the discharge sound detection element, respectively. In response to the control pulse, the controller enters a standby state for a predetermined period of time, receives a discharge sound signal from the discharge sound detection element, and at each point in time when this signal exceeds two different thresholds, a second pulse having a predetermined pulse width, respectively. a plurality of pulse generation circuits that emit first and second pulses, and a plurality of pulses that detect the existence of a non-overlapping time of the first and second pulses for each pulse generation circuit and generate an output signal. a verification circuit; a determination circuit that determines that a partial discharge has occurred when an output signal from the pulse verification circuit is present from a predetermined number or more of the pulse verification circuits; and control of the operation of the electrical equipment based on the output signal of the determination circuit. A partial discharge monitoring device characterized by comprising an output circuit that performs the following.