JPH10142286A - Insulation diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of erroneous determination by performing noise check before the start of diagnosis for every insulation diagnosis even after an optimum frequency point is set, and measuring electromagnetic wave level with use of an abnormal detection antenna if the noise level exceeds a specified value. SOLUTION: A determination unit 10 switches a switch 6 to the side of a noise antenna 3 and the frequency point where noise is not detected is set as the optimum frequency preliminarily set by a tuner 8. After the setting of optimum frequency the measurement of level of electromagnetic wave is carried out. Even after the setting of the optimum frequency point, noise check is conducted before the insulation diagnosis by switching the switch 6 to the side of noise antenna 3, and switching the tuner 8 to several optimum frequency points for the checking of measurement level. Data of the frequency point exceeding a specified level is made invalid and the other is made valid to carry out the measurement of electromagnetic wave. A determinating unit 10 switches a switch 6 to the side of abnormal detection antenna 2 to thereby obtain data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation diagnostic apparatus for diagnosing the insulation performance of electric equipment such as a gas insulated switchgear, and more particularly, to detecting an electromagnetic wave due to a partial discharge generated inside the electric equipment. The present invention relates to an insulation diagnosis device that performs insulation diagnosis.

[0002]

2. Description of the Related Art In electrical equipment such as a gas insulated switchgear, a partial discharge occurs when insulation is abnormal, and the partial discharge generates an electromagnetic wave secondarily. In order to prevent serious accidents due to insulation breakdown of electrical equipment, an insulation diagnostic device that detects whether or not insulation abnormality has occurred inside operating electrical equipment by detecting electromagnetic waves at the stage of partial discharge has been developed. Proposed.

In this insulation diagnostic apparatus, an electromagnetic wave generated by partial discharge is detected by an abnormality detection antenna. Further, since the frequency of the electromagnetic wave due to the partial discharge is not specified, the electromagnetic wave is monitored at a plurality of frequency points. Since the abnormality detection antenna picks up not only electromagnetic waves from inside the electric device but also external noise, it is necessary to eliminate erroneous determinations due to this noise. Therefore, when the insulation monitoring device 1 is started, noise is detected using a noise antenna. Then, based on the detection result, a plurality of frequency points where no noise exists are selected as optimal frequency points. Then, the level of the electromagnetic wave detected by the abnormality detection antenna is measured at each optimum frequency point, and insulation diagnosis is performed based on the measured data.

[0004]

In the above-mentioned conventional insulation monitoring device, the setting of the optimum frequency point is performed only when the insulation monitoring device is started. For this reason, even if a noise-free frequency is set as the optimal frequency point,
If external noise is generated after the setting, the noise may be erroneously recognized as an electromagnetic wave due to partial discharge at the time of insulation diagnosis, and erroneous diagnosis may be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent an erroneous determination due to noise from occurring in an insulation diagnosis apparatus for diagnosing insulation performance of electric equipment.

[0006]

According to the present invention, in order to achieve the above object, a noise check is performed before the start of each insulation diagnosis even after the optimum frequency point is set. First, when starting up the insulation diagnostic apparatus, a plurality of frequency points without external noise are determined as optimal frequency points using a noise antenna.

Next, immediately before or simultaneously with the start of insulation diagnosis, a noise level is detected for each optimum frequency point by a noise antenna. When the detection level exceeds a predetermined value, the frequency data at the frequency point is invalidated, and the data at the frequency point cannot be used during the insulation diagnosis. After the noise check,
An electromagnetic wave level is measured at each optimum frequency point using an abnormality detection antenna. Then, insulation diagnosis is performed using only valid data among the obtained data.

Thus, even if noise occurs after setting the optimum frequency point, the effect can be eliminated, and erroneous diagnosis can be prevented. Further, noise may be generated during a very short period from the noise check to the insulation diagnosis. In order to prevent the erroneous diagnosis due to the noise, the noise check and the insulation diagnosis can be repeated a plurality of times, and the insulation diagnosis can be performed based on a plurality of detection data obtained thereby. In this case, adverse effects due to noise can be reduced by taking a plurality of data.
At this time, noise can be more effectively removed by calculating an average value, a minimum value, a maximum value, or the like of a plurality of data.

[0009]

FIG. 1 shows a configuration of an insulation monitoring device. Reference numeral 1 denotes an insulation monitoring device, to which an abnormality detection antenna 2 for detecting an electromagnetic wave generated due to an insulation abnormality and a noise antenna 3 for detecting external noise are connected. Reference numeral 4 denotes an electric device. When a slight insulation abnormality occurs in the electric device, a partial discharge 5 occurs in a corresponding portion.

The detection outputs of both antennas 2 and 3 are supplied to switch 6
, One is amplified by the amplifier 7, the signal is selected for each optimum frequency point by the tuner 8, converted into a digital signal by the A / D converter 9, and input to the decision unit 10. This determiner 10 can be constituted by a CPU. Further, the switching device 5 is provided with a decision device 10.
The tuner 8 selects a tuning frequency under the control of the determiner 10.

FIG. 2 shows a first example of the diagnostic operation by the determiner 10.
4 shows an example flowchart. In step S1, when starting up the insulation monitoring apparatus 1, a plurality of frequency points at which noise is not detected are selected and set as the optimum frequency. For this reason, the determination unit 10 switches the switch 6 to the noise antenna 3 side. Then, the tuner 8 measures the level of the electromagnetic wave detected by the noise antenna 3 at a plurality of preset frequency points. FIG. 3 (a)
This measurement result is shown. In FIG. 3, BGNL
Represents the background noise level.

The determination unit 10 rechecks the frequency point of the tuner 8 at the frequency point where the measured level exceeds the background noise level BGNL by shifting the frequency of the tuner 8 by ΔF. This is repeated until the measurement level becomes lower than the background noise level BGNL, and finally, the monitoring frequency points are set so that most of the frequency points have lower detection levels. FIG. 3B shows a state in which the optimum frequency point is set in this way.

In step S2, after setting the optimum frequency, the measurement of the electromagnetic wave is performed. This step S2 can be repeated periodically or at an arbitrary interval. In step S2, first, a noise check is performed in step S21. The determiner 10 switches the switch 6 to the noise antenna 3 side, switches the tuner 8 to a plurality of optimum frequency points, and checks the measurement level. Here, if there is no newly generated noise, as shown in FIG. 4A, at any frequency point, the background noise level BGNL is lower than the level (BGN + α) obtained by adding the margin (α). However, when the accidental noise occurs, as shown in FIG. 4B, the detection level becomes the level BGNL + α at some frequency points.
Exceeds.

In step S22, validity / invalidity of data is determined for each optimum frequency point. As shown in FIG. 4B, data at a frequency point exceeding the level BGNL + α is invalidated, and other data is validated. As a result, the data at this frequency point is not used for a subsequent diagnostic operation. In step S23, the electromagnetic wave due to the partial discharge is measured. The determiner 10 switches the switch 6 to the abnormality detection antenna 2 side, switches the tuner 8 to a plurality of optimum frequency points, and obtains data for each frequency point. The determination unit 10 determines the presence or absence of a partial discharge using valid data excluding the data invalidated in step S22 from these data.
Note that the tuner 8 may be configured not to select invalid frequency points.

Since the data used for this determination excludes data affected by noise, the insulation diagnosis
Accurate diagnosis without the influence of noise can be performed. Since a method for determining the presence or absence of a partial discharge is known, a description thereof will be omitted. Note that there is a method of evaluating the difference between the level of the noise antenna and the level of the abnormality detection antenna. However, since the characteristics of the abnormality detection antenna differ depending on the device, adjustment is required each time.
In the present invention, such adjustment is not required.

The noise check and the measurement of the electromagnetic wave can be performed simultaneously. In this example, the processing is performed in a time-sharing manner to reduce the cost of the system. FIG. 5 shows a modification of the diagnostic operation of FIG. In the first example described with reference to FIG.
Since the electromagnetic wave due to the partial discharge is measured after performing the noise check once, there is a time difference between the noise check and the measurement. If noise happens to occur during this time, erroneous diagnosis due to the noise may occur. In this example,
This is further prevented.

In FIG. 5, step S1 is the same operation as in FIG. Also, in the measurement operation of step S3 following step S1, from step S21 to step S2
The operations up to 3 are the same as those in FIG. That is, step S
After setting the optimal frequency point, a series of operations including noise check in step S21, determination of validity / invalidity of the frequency point in step S22, and measurement in step S23 are performed. When these operations are completed, the number of measurements is determined in step S24. Here, it is determined whether or not the measurement has been performed a predetermined number of times N, and if the number has not reached N, the process returns to step S21 to perform the noise check again and then perform the measurement. If it is determined in step S24 that the number of measurements has reached N, the process proceeds to step S25.

In step S25, calculation using the measured data is performed. Here, as the electromagnetic wave data, an average value, a minimum value, a maximum value, or χ ⁻ -3σ of the electromagnetic wave level measured N times is calculated for each frequency point. Thereafter, the determination unit 10 determines whether or not there is a partial discharge based on the calculated value. When the average value is adopted, even if noise occurs during the short time from noise check to measurement, if measurement is performed multiple times,
The influence of a single noise is reduced. When the minimum value is adopted, diagnosis can be performed using data free from noise. If continuous noise occurs after the noise check, the data at that frequency point will be invalidated by the second and subsequent noise checks.
Also in this case, erroneous determination due to noise can be prevented.

There are various methods for calculating data in the case where the measurement is performed a plurality of times. For example, when taking the average value, instead of taking the average of all data at each frequency point, cut the data on the maximum value side and the minimum value side, which are likely to contain errors, and take the average value with the remaining data. And more accurate data can be obtained. Further, the minimum value for determination can be obtained from the data obtained by cutting the data on the maximum value side and the minimum value side. The average value may be a square mean or an average based on a normal distribution.

Further, after calculating the average value or the minimum value for each frequency point, the data on the maximum value side and the data on the minimum value side may be cut from the data (the average value or the minimum value) of all the frequency points. . The insulation diagnostic device of the present invention is effective when used at different locations, times, etc., such as a portable type.

According to the present invention, it is possible to prevent an erroneous diagnosis due to noise from occurring in an insulation diagnosis apparatus for diagnosing the insulation performance of electric equipment. Furthermore, a more accurate insulation diagnosis can be performed by stabilizing the measurement result of the electromagnetic wave level.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an insulation monitoring device of the present invention.

FIG. 2 is a flowchart showing the operation of the apparatus of FIG.

FIG. 3 is a diagram illustrating a method for determining an optimum frequency in the insulation monitoring device.

FIG. 4 is a view for explaining an operation of a noise check in the apparatus of FIG. 1;

FIG. 5 is a flowchart showing a modification of the operation in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulation monitoring device 2 ... Abnormality detection antenna 3 ... Noise antenna 4 ... Electric equipment 5 ... Partial discharge 6 ... Switching device 7 ... Amplifier 8 ... Tuner 9 ... AD converter 10 ... Judgment device

Claims (2)

[Claims] 1. An insulation diagnostic apparatus using an electromagnetic wave detection method, wherein an abnormality detection antenna for detecting an electromagnetic wave due to partial discharge generated due to insulation abnormality, a noise antenna for detecting external noise, and the abnormality detection antenna are used. A determination unit that performs insulation diagnosis by measuring the levels of the electromagnetic waves at a plurality of frequency points, and measures the electromagnetic wave level at each of the plurality of frequency points with the noise antenna immediately before or simultaneously with the insulation diagnosis. An insulation diagnostic device comprising: a noise detector that performs a noise check to invalidate measured data at a frequency point when the measured level exceeds a predetermined value. 2. The insulation diagnosis apparatus according to claim 1, wherein the determination unit performs the noise check and the insulation diagnosis a plurality of times, and performs the insulation diagnosis based on the measurement data of the plurality of times.