JPS6349453B2 - - Google Patents

Description

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

If internal partial discharge continues for a long period of time in high-voltage stationary electrical equipment such as oil-immersed transformers and reactors, there is a risk that it will progress to full-scale insulation breakdown and lead to electrical insulation accidents. Therefore, it is desired to constantly monitor this internal partial discharge and detect its occurrence at an early stage to prevent electrical appliance accidents. However, when a stationary electric appliance is in operation or is being energized, an external nozzle that is difficult to distinguish from internal partial discharges such as external corona generated by power lines or bushings, opening/closing surges, and radio noise enters, causing internal partial discharges. What is needed is an internal partial discharge monitoring device that is easy to handle and has the ability to clearly distinguish between nozzles and external nozzles.

Such a device is known, for example, from Japanese Patent Application 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 checks whether all of these times are within a predetermined time. judge,
If the number of detected discharge sounds that satisfy the above conditions exceeds a predetermined number in the multiple condition satisfaction determination unit, the time difference between sounds is confirmed in the sound-to-sound time difference determination unit, and if there is a time difference, it is determined that it is an internal discharge, and it is notified and calculated. The system is configured to calculate the partial discharge occurrence position in the section. However, since this device is configured to start counting time from the point at which an electrical pulse is detected, if the monitored electrical equipment is installed in a location where external noise occurs frequently, such as a substation, In many cases, the probability that a time count will be started by an electric pulse corresponding to an external noise is far greater than the probability that a time count will be started by a discharge pulse corresponding to an internal discharge. The disadvantage is that it is extremely difficult to reliably detect.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a partial discharge monitoring device that eliminates the above-mentioned conventional drawbacks, has high accuracy in distinguishing between external noise and internal partial discharge, and is capable of reliably detecting the occurrence of internal discharge.

According to the present invention, the above-mentioned object is achieved by focusing on the fact that the frequency of occurrence of acoustic noise in substations, etc. is much lower than the frequency of occurrence of external electrical noise, First, it is confirmed that the detection time difference between the ultrasonic pulses is within a predetermined time range, and then the above conditions are satisfied. If the ultrasonic pulse is detected, it is confirmed whether or not an electric pulse is detected by a partial discharge detector connected to an external terminal of the stationary electric appliance within a predetermined time range before the ultrasonic pulse is detected; This was achieved by configuring the device based on the idea that detected ultrasonic pulses and electric pulses are determined to be caused by partial discharge inside the stationary electric appliance only when two conditions are satisfied. That is, according to the above idea, it is necessary to go back to a predetermined time before the sound detection time difference is confirmed and know the status of the ultrasonic pulses and electric pulses detected during that time. The apparatus includes a waveform recorder having a memory function to constantly record the electric pulses and the amplified ultrasonic pulses, and a pulse conversion circuit that converts the ultrasonic pulses into rectangular wave pulses at predetermined time intervals; A verification circuit detects the overlapping time of the rectangular wave pulses and confirms the detection time difference between the ultrasonic pulses, and the output of the verification circuit provides a command pulse to temporarily stop the recording operation of the waveform recorder and output the recorded contents. A pulse control circuit to output and the memory contents of the waveform recorder are input, and after confirming that an electric pulse is detected within a predetermined time before the ultrasonic pulse is detected, a partial discharge is generated in the stationary electric device. The present invention is configured to include a determination unit that notifies the user of the occurrence of the event.

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

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a high-voltage stationary electric appliance such as an oil-immersed transformer or a sealed switchgear, and 2 is a high-voltage bushing connected to a power transmission line 3, etc., so that high-voltage current is guided to the high-voltage conductor inside the stationary electric appliance 3. This also serves as a path for electrical external noise to enter stationary appliances. Reference numeral 4 denotes a voltage measuring terminal of the bushing 2, and a portion of the current pulse flowing through the high voltage conductor due to partial discharge inside the stationary electric device and the external noise appear at the voltage measuring terminal via the capacitance of the bushing 2. Reference numeral 5 denotes a partial discharge detector that is connected to the voltage measurement terminal 4 and detects the current pulse (hereinafter referred to as an electric pulse), and the output pulse of this partial discharge detector is transmitted via a cable 22 to a partial discharge measuring device 6.
The signal is input to a digital waveform recorder 12 via a cable 23, where it is amplified and waveform-shaped.
The detected waveform within a predetermined period of time is always stored. On the other hand, a plurality of discharge sound detection elements 7a to 7c, such as ultrasonic microphones, are attached to the container wall of the stationary electric appliance 1 at different positions.
~7c, the ultrasonic pulse accompanying the occurrence of partial discharge has a propagation time ta, respectively with respect to the electric pulse.
tb and tc are detected with a delay of tb and tc, respectively, and cable 2
4a to 24c to pulse amplifiers 8a to 8c, where it is amplified and sent to cables 25a to 25.
5c, the ultrasonic pulse waveform detected within a predetermined time is constantly recorded together with the electric pulse. The outputs of the pulse amplifiers 8a to 8c are input to pulse conversion circuits 9a to 9c via cables 26a to 26c, where they are waveform-shaped and if the peak value exceeds a predetermined threshold value, a rectangular wave with a pulse width TW is generated. The pulses are converted into pulses and input to the pulse verification circuit 10 via cables 27a to 27c.

Here, the pulse width TW is the maximum value of the propagation time difference between ultrasonic pulses determined by the dimensions of the container of the stationary electric appliance 1, the mounting positions of the discharge sound detection elements 7a to 7c, the sound speed of the insulating medium in the container, etc. If the detected ultrasonic pulse is due to internal partial discharge of a stationary electric device, the time difference between the individual ultrasonic pulses is |ta−tb|, |ta−tc|, |
There is a relationship of tb−tc|≦TW.

Now, the pulse matching circuit 10 is the pulse converting circuit 9
The detection time difference between the plurality of ultrasonic pulses emitted by a to 9c is |ta−tb|, |ta−tc|, |tb−tc|≦
When TW is satisfied, that is, the rectangular wave pulses of time width TW overlap each other and it takes time.
If confirmed by the circuit, the output changes from off to on and is sent to the pulse control circuit 11 via the cable 28.
is input. The pulse control circuit 11 transmits, via the cable 29, a signal to stop the waveform capture of the waveform recorder 12 when the signal input via the cable 28 changes from off to on. The recorded contents are transmitted to the determination section 14 via the interface 13. The determination unit 14 determines the generation time of the electric pulse captured within a predetermined time before the waveform recorder 12 stops capturing.
TO and the time of occurrence of each ultrasonic pulse
Ta, Tb, and Tc are detected by an arithmetic circuit composed of, for example, a microcomputer, and the detection delay time ta for each ultrasonic pulse with respect to the electric pulse is
Find Ta−To, tb=Tb−To, tc=Tc−To,
whether each satisfies the conditions of the formula,
Also, check whether the detection time difference between ultrasonic pulses satisfies the formula.

T _nio ≦ta, tb, tc≦T _nax ... |ta−tb|, |tb−tc|, |ta−tc|≧tw ...Here, T _nio and T _nax are the size of the container of the stationary electric appliance 1 and These are the minimum and maximum values of the detection delay time of the ultrasonic pulse with respect to the electric pulse, which are determined by the mounting position of the discharge sound detection elements 7a to 7c and the speed of sound in the insulating medium of the stationary electric appliance. This is the minimum detection time difference. When the arithmetic circuit determines that both of the above conditions are satisfied, it determines that the series of electric pulses and ultrasonic pulses recorded on the waveform recorder are due to internal partial discharge of the stationary electric appliance 1, and the condition is satisfied. If not, it is determined to be external noise or acoustic noise caused by gravel, hail, etc. hitting the container of the stationary electrical appliance 1, and is distinguished from the internal discharge. The size of the internal discharge can be determined by determining the peak value of the electric pulse. The calculation results in the above calculation circuit, the determination results of internal discharge and external noise, the magnitude of internal discharge, etc. are transmitted to the recorder 16 via the cable 33 and recorded, and are also sent to the alarm output circuit via the cable 32. 15, and is configured to operate an alarm device or a trip circuit of a stationary electric appliance (not shown).

On the other hand, when the calculation and judgment in the judgment section 14 are completed, a signal is transmitted to the pulse control circuit 11 via the cable 34, and the pulse control circuit 11 immediately resets all the circuits to the initial state. By constantly repeating the above-mentioned partial discharge monitoring operation, it is devised to continuously monitor whether or not an internal partial discharge has occurred in the stationary electric appliance 1. Furthermore, since internal partial discharges in stationary electrical appliances generally occur repeatedly and gradually progress to dielectric breakdown, alarms can be configured to be issued when the frequency or number of occurrences of partial discharges exceeds a predetermined level. The reliability of alarms can be increased.

FIG. 2 is a time chart of the recorded waveform of the waveform recorder 12 in this embodiment, and shows the recorded contents when the waveform recorder stops writing by the pulse control circuit 11. In the figure, 29 is a write stop signal of the pulse control circuit 11, and the record of the T _S time before this point remains in the waveform recorder 12, and each time is ta to tc based on the generation time TO of the electric pulse 23. Delayed ultrasonic pulse 25
a to 25c are recorded. In addition, T _nax in the figure,
T _nio is the detection delay time ta, tb of the ultrasonic pulse with respect to the electric pulse, which is determined by the size of the container of the stationary electric appliance 1 and the mounting position of the discharge sound detection element, etc.
The maximum and minimum values of tc and T _nio ≦ta, tb,
When the condition of tc≦T _nax is satisfied, the series of pulses shown in the figure is determined to be caused by internal partial discharge of the stationary electric appliance 1.

FIG. 3 shows a time chart of output pulses of each main part in the circuit configuration of FIG. 1, and each pulse is indicated by the reference symbol of each part in FIG. 1. In the figure, 6 is an electric pulse detected at time T _p , 8a to 8c are ultrasonic pulses detected at time Ta to Tc, and 9a to 9c are pulse conversion circuits 9.
a to 9c are rectangular wave pulses with a pulse width TW generated corresponding to the ultrasonic pulses 8a to 8c, and 10 is a pulse matching circuit 10 which generates the rectangular wave pulses 9a to 9.
29 is a signal pulse generated by the control circuit 11 of the waveform recorder 12 which is generated when the control circuit 11 receives this signal when the pulse verification circuit changes from off to on. Signal for commanding stop of writing and transfer of recorded contents, 1
2 is a write operation of the waveform recorder, 31 is a transfer operation of the interface 13, 14 is a calculation and judgment operation of the judgment unit 14, and 34 is a device reset command signal that the waveform recorder 12 issues to the control circuit when the judgment is completed. It is.

4 and 5 are time charts when noise is detected in the embodiment of the present invention.
FIG. 4 is a time chart when acoustic noise is detected. In this case, since no electric pulse is detected, the determination section 14 determines that it is noise. Fig. 5 is a time chart when abnormal voltage such as switching surge or lightning surge affects the discharge sound detection circuit and its signal transmission circuit. In this case, electric pulse 23 and ultrasonic pulses 25a to 25c are detected at the same time. Therefore, the determination unit 14 determines that the noise is noise because the conditional expression is not satisfied.

FIG. 6 is a time chart when an internal partial discharge of the stationary electric appliance 1 and an electric pulse due to external noise are detected in a mixed manner in the embodiment of the present invention. In this case, the pulse comparison circuit 10 confirms that the detection time difference between the ultrasonic pulses 25a to 25c is less than the maximum time difference TW, and the recorded contents of the waveform recorder 12 shown in FIG. 6 are transferred to the determination section 14. In the determination section, first, three electric pulses V1, V
0, V2 occurrence times T01, T0, T02 are searched,
Next, the detection delay times ta to tc of the ultrasonic pulses 25a to 25c with respect to the respective electric pulse generation times are determined.
is required. Then, a calculation is performed to determine whether the above conditional expression is satisfied. In the figure, since (Tb-T01)>T _nax , the electric pulse V1 does not satisfy the conditional expression and is determined to be external noise, and the electric pulse V2 is detected later than the ultrasonic pulses 25a and 25c, so the conditional expression Since the electric pulse V0 satisfies the conditional expression, it is determined to be an internal partial discharge of the stationary electric appliance 1. Whether the detection time difference between the ultrasonic pulses 25a to 25c satisfies the conditional expression or not After the determination, the calculation result and the determination result are output.

In general, in stationary electrical equipment located in substations etc. where the external noise level is high, electrical pulses due to internal partial discharge of the stationary electrical equipment and electrical pulses due to external noise are often detected as being mixed, as shown in Figure 6. In a device configured to start time counting with an electric pulse as in the prior art, time counting starts with the electric pulse V1, and as a result, the electric pulse V0 and Sound wave pulse 25a~
25c had a high risk of being incorrectly judged as noise. According to the description of the above embodiment, the pulse conversion circuit emits one rectangular wave pulse when the ultrasonic pulses detected by the plurality of discharge sound detection elements exceed a predetermined threshold;
A control circuit is provided to stop recording of the waveform recorder when a predetermined time difference occurs between the generation times of the rectangular wave pulses, and a determining section determines whether an electric pulse due to internal discharge corresponding to the ultrasonic pulse is recorded. Since the above conditional expressions are used to calculate each condition one by one, and whether or not it is an internal discharge is determined based on the result, it is possible to avoid misidentifying internal discharge as noise as in the prior art, or to cause the device to malfunction due to external noise. It is possible to eliminate disadvantages such as interruption of internal discharge monitoring due to frequent repetition of monitoring operations.

Next, other embodiments of the invention will be described.
The configuration of the monitoring device is the same as that shown in FIG. 3, and the time charts of each part are also the same as those shown in FIGS. 2 to 6. However, the conditional expression for the internal partial discharge of the stationary electric appliance in the determination unit 14 is different from the above embodiment as described below. That is, the recorded contents transferred from the waveform recorder 12 via the interface 13 are examined by an arithmetic circuit composed of, for example, a microcomputer, and the ultrasonic pulse detection delay times ta, tb, tc with respect to the electric pulse detection time are determined. seek. Next, it is calculated whether the detection delay times ta to tc satisfy the conditional expressions and.

0<x<X 0<y<Y 0<z<Z Where, (xc,
yc, zc) are the mounting coordinates of the discharge sound detection element in the stationary electrical appliance container, (x ₀ , y ₀ , z ₀ ) are the coordinates of the internal partial discharge occurrence position of the stationary electrical appliance, and υ ₀ is the coordinate of the stationary electrical appliance container. The speed of sound in the insulating medium, k, is a correction coefficient that takes into account the estimation error of the partial discharge occurrence position.

If the coordinates (x ₀ , y ₀ , z ₀ ) of the ultrasonic source determined by the conditional expression are the coordinates inside the electric appliance, it is determined that there is an internal partial discharge in the stationary electric appliance 1, and the recorder 16
The calculation results are recorded in the output circuit 15.
The occurrence of internal discharge is notified via the .

The solution to the conditional expression may be found at two points depending on the mounting position of the discharge sound detection element, but if four or more discharge sound detection elements are used, only one point can be found uniquely. However, since the solution to the conditional expression is symmetrical with respect to the plane passing through the three mounting points of the three discharge sound detection elements, if the mounting position is set so that one of the three points is off the container, it will be practical. In short, the purpose can be achieved with three discharge sound detection elements.
In reality, the coordinates (x ₀ , y ₀ ,
z ₀ ) cannot be narrowed down to one point in many cases. In the conditional expression, a correction coefficient k is used to correct these errors, and the value of k for which there is a solution to the conditional expression is found, and this value of k is within the allowable range. If so, it can be determined that it is an internal discharge of a stationary appliance.

As described above, according to the present invention, ultrasonic pulses that are detected by a plurality of discharge sound detection elements and exceed a predetermined threshold value are detected by a plurality of discharge sound detection elements by using ultrasonic pulses with a relatively low noise generation frequency as a trigger source in a substation, etc. If the detection time difference is below, stop the continuous recording of the waveform recorder, calculate the time difference between the recorded electric pulses and ultrasonic pulses, and when the time difference satisfies a predetermined conditional expression. By configuring the system so that only a partial discharge occurs inside a stationary electrical appliance and notifies the determination result, it is possible to avoid the conventional drawback of determining an internal discharge as noise when the device is triggered by an electric pulse caused by external noise. Errors can be prevented, and unnecessary judgment operations can be prevented from being repeated due to electrical noise that occurs frequently.With these improvements, it is possible to detect any partial discharge that occurs inside a stationary electrical appliance. Therefore, we were able to provide a partial discharge monitoring device with higher internal partial discharge detection accuracy than conventional devices.

The present invention can be widely used as an internal partial discharge monitoring device for not only oil-filled electrical appliances such as oil-filled transformers and oil-filled reactors, but also gas-insulated transformers, gas-insulated switchgears, gas-insulated cables, and the like.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a time chart showing recorded waveforms of a waveform recorder, and Fig. 3 is a main point when an internal partial discharge is detected in the block diagram of Fig. 1. Figure 4 is a time chart for acoustic noise, Figure 5 is a time chart for when electrical induction occurs in the discharge sound transmission circuit, and Figure 6 is for internal discharge and electrical external noise intersecting. This is a time chart for when a device is detected. In the figure, 1... Stationary electric appliance, 2... Bushing, 3... Power transmission line, 4... PD terminal, 5... Partial discharge detector, 6... Partial discharge measuring device, 7a to 7c.
...Discharge sound detection element, 8a to 8c...Amplifier, 9
a to 9c... Pulse conversion circuit, 10... Pulse matching circuit, 11... Pulse control circuit, 12... Waveform recorder, 13... Interface, 14... Judgment unit, 15... Output circuit, 16... ...It is a recorder.

Claims (1)

[Claims] 1. Electrical pulses detected by a partial discharge measuring device connected to an external terminal of a high-voltage stationary electric appliance and a plurality of discharge sound detection elements attached to different positions of the container of the stationary electric appliance. In a partial discharge monitoring device equipped with a waveform recorder that continuously records detected ultrasonic pulses, when the plurality of discharge sound detection elements detect an ultrasonic pulse exceeding a certain level, each ultrasonic pulse a pulse conversion circuit that converts the pulse into a pulse with a time width corresponding to the maximum propagation time of the ultrasonic pulse in the high-voltage stationary electric device; A pulse control circuit that issues a command signal to stop and output recorded contents, and a pulse control circuit that calculates a detection time difference between the electric pulse and the ultrasonic pulse from the recorded waveform of the waveform recorder, and the detection time difference satisfies a predetermined condition. 1. A partial discharge monitoring device for a high-voltage stationary electric appliance, comprising: a determining unit that determines that there is an internal partial discharge in the stationary electric appliance and outputs a notification signal and a calculation result when the stationary electric appliance does so. 2. In the device according to claim 1,
The determination unit examines the recorded content transferred from the waveform recorder and determines that it is an internal partial discharge of a stationary electric appliance only when the detection delay times ta, tb, and tc of the ultrasonic pulse with respect to the electric pulse satisfy the conditional expression. 1. A partial discharge monitoring device for high-voltage stationary electrical appliances, characterized in that it outputs calculation results and judgment results. 0 < xo < zb),
(xc, yc, zc) are the coordinates of the discharge sound detection element attached to the container of the stationary appliance, (xo, yo, zo) are the coordinates of the internal partial discharge occurrence position of the stationary appliance, and vo is the insulating medium in the stationary appliance. The sound velocity in the equation, k, is a correction coefficient that takes into consideration the estimation error of the partial discharge occurrence position.