JP2003207536A - Pulse generation circuit for calibration of partial discharge measuring circuit and operation confirmation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse signal generation circuit capable of facilitating specification of a partial discharge start voltage and a generated charge quantity by generating a pulse equivalent to a discharge pulse by using a test voltage of a high voltage generation device and by superimposing the equivalent pulse with a test voltage signal, concerning a dispersion problem of measurement in a partial discharge test caused by difficulty of specification of a calibration charge quantity and a discharge start voltage value, and an operation confirmation method of a measuring circuit using the circuit. <P>SOLUTION: A capacitor 1 and a capacitor 2 connected in series are provided, and a switch 5 is connected in parallel to both ends of the capacitor 2, and a voltage between both ends of the capacitor 2 is used as a comparison voltage of a comparator 4. At the moment the comparison voltage becomes higher than a reference voltage, both ends of the capacitor 2 are short circuited to acquire a pulse signal, and the pulse signal is superimposed with the test voltage of the high voltage generation device through the capacitor 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge test apparatus, and more particularly to a calibration pulse generation circuit for a partial discharge measurement circuit and a method for confirming the operation of the partial discharge measurement circuit.

[0002]

2. Description of the Related Art Calibration of a partial discharge amount measuring circuit (hereinafter referred to as "measuring circuit") is performed in 4.1 and 4.2 in "JEC-0401 (The Institute of Electrical Engineers of Japan, Electrical Standards Research Committee)".
Before measuring the partial discharge of a sample by applying a high voltage, that is, at the start-up inspection, measure with all the components such as the power supply, sample and measurement circuit connected as specified in The circuit must be calibrated and must be recalibrated each time the sample and measurement circuit change.
Then, the calibration method of the measurement circuit is performed by injecting a known charge qo between the electrodes of the sample using the calibration charge generation circuit, and obtaining the conversion coefficient between this charge amount and the indicated value of the measurement circuit (hereinafter This method is called "charge injection method".) In this case, the output Uo of the pulse voltage generator (PG) in FIG. 4 (a) illustrated in the section 4.2 “Calibration of magnitude of discharge pulse” in the standard is passed through the capacitor Co to the electrode of the sample Ca. When injected in between, the calibration charge qo Therefore, if each value is selected so that Ca >> Co, the calibration charge qo injected into the sample will be become.

In addition, the standard of 7. It is pointed out that the existence of noise level has a great influence on the measurement sensitivity of partial discharge, and C.4 in Annex C of "IEC60664-1 (Insulation coordination of devices in low voltage system)" is pointed out.
“Calibration” describes how to confirm the partial discharge amount and noise level generated by test leads and jigs. In addition, since it is stated in any of the standards that the noise level must be 50% or less of the discharge pulse to be measured, at the time of start-up inspection, in addition to the calibration of the measurement circuit, It is desirable to confirm the operation of the measurement circuit including the confirmation of the noise level while applying a predetermined high voltage.

In the charge injection method, usually, the output of the signal generator is differentiated to obtain a pseudo discharge pulse signal waveform, and the measurement circuit is calibrated by this, or the output signal of the pulse generator is used to calibrate the measurement circuit. Is being calibrated. However, since it is very difficult to generate a high voltage with a general pulse generator or signal generator, it is impossible to confirm the noise level using these. Therefore, the confirmation of the noise level and the specification of the voltage at which the partial discharge phenomenon occurs, that is, the partial discharge inception voltage and the generated charge amount are performed by using an AC high voltage generator such as a partial discharge measuring device or a withstand voltage test device. This is done by directly applying a high voltage to the test sample and measuring these values.However, the partial discharge phenomenon occurs randomly at random, and the appearance of the discharge phenomenon and the discharge level depend on the measurement environment. Is not uniform, it is not easy to specify the partial discharge inception voltage and the generated charge amount.

As a countermeasure against this, a method of using a sample whose partial discharge starting voltage and generated charge amount are measured in advance (hereinafter referred to as "standard sample method") is generally used. This standard sample method is specifically prepared by preparing a sample that looks like a sample or arbitrarily selecting from the sample, and performing a predetermined partial discharge test on it. The partial discharge inception voltage and the generated charge amount of the sample are measured, and the measured value is regarded as the standard value of the discharge charge amount, and the operation of the measurement circuit is confirmed by the standard sample.

However, the standard sample cannot be freely selected to have a desired electrostatic capacity, and is significantly deteriorated by repeated high voltage application history, so that the standard sample is affected by aging and moisture adhesion. Since it is also difficult to prevent the influence, the standard sample method tends to cause variations in the measurement, and the confirmation of the occurrence of the disconnection accident between the connection paths of the respective components must be unreliable.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a pulse signal generation circuit for superimposing a pulse equivalent to a discharge phenomenon on a partial discharge test voltage. It is to provide a method of confirming the operation of a measurement circuit using the same.

[0008]

In order to solve the above problems, the invention according to claim 1 comprises a comparator 4, a capacitor 1 and a capacitor 2 connected in series, and a comparator is provided at both ends of the capacitor 2. A switch 5 whose ON / OFF is controlled by 4 is connected in parallel, and the voltage across the capacitor 2 is used as the comparison voltage of the comparator. When the comparison voltage becomes higher than the reference voltage, the switch 5 short-circuits both ends of the capacitor 2. And pulse signal is obtained.

A second aspect of the present invention is a method of confirming the operation of a partial discharge measuring circuit using the calibration pulse generating circuit according to the first aspect, which comprises a step of calibrating the partial discharge measuring circuit and noise. It is characterized by the step of confirming the level.

DETAILED DESCRIPTION OF THE INVENTION

The inventor of the present invention has found that the shortcomings of the standard sample method are caused by the unreliability of the standard charge amount, and that an AC high voltage generator such as a partial discharge device or a withstand voltage test device (hereinafter "High voltage generator") is also a kind of signal generator, using the test voltage of the high voltage generator to generate a pulse signal equivalent to the discharge pulse, and then generate this pulse signal. By superimposing on the test voltage signal, not only the partial discharge inception voltage and the generated charge amount can be easily specified, but also it is possible to confirm and measure the noise level with high reproducibility, and to create the present invention. I arrived. less than,
The invention according to claim 1 will be described with reference to FIGS. 1 and 2. 1 shows an embodiment of the present invention, and FIG. 2 shows its operation waveform.

The positive terminal of the comparator 4 is connected to the capacitor 2, and the negative terminal of the comparator 4 is connected to the reference voltage 3. When terminals A and B shown in FIG. 1 are respectively connected to the test voltage application terminals of the high voltage generator and the test voltage is applied from the high voltage generator, the capacitors 1 and 2 are in a charged state. Here, the voltage across the capacitor 1 is Vc1, the capacitance is C1, the voltage across the capacitor 2 is Vc2, the capacitance is C2, and the test voltage is Va.
Then, the voltage across each capacitor is And Vc2 is input to the comparator 4 as a comparison voltage. The capacitance relationship between the capacitors 1 and 2 in this embodiment is C1 << C2.

Assuming that the reference voltage 3 is Vr, the voltage Vc2 across the capacitor 2 becomes V when the test voltage Va is applied.
At the moment when it becomes higher than r, the comparator 4 turns on the switch 5. Then, the switch 5 short-circuits both ends of the capacitor 2 to discharge the electric charge stored in the capacitor 2, and Vc
2 instantly goes to zero volts. Further, since the comparator 4 turns off the switch 5 at the moment when Vc2 becomes lower than Vr, Vc2 instantly becomes zero volt, and at the same time, the capacitor 2 starts charging. Then, at the moment when Vc2 becomes higher than Vr, the switch 5 is turned on again, and Vc2 instantly becomes zero volt. By repeating such a series of operations, as shown by 11 in FIG.
A sawtooth waveform with an amplitude of Vr appears. However, as is well known, the period when the capacitor is in the charging state is the period from when the output waveform starts to rise until it reaches the maximum value, so when the test voltage waveform of the high voltage generator is in the falling state. No serrated waveform appears. Although the positive input of the comparator 4 is on the Vc2 side and the negative input is on the Vr side in this embodiment, the switch 5 can be operated so as to short-circuit both ends of the capacitor 2 when Vc2 becomes higher than Vr. In that case, the input polarity of the comparator 4 may be reversed.

On the other hand, the capacitor 1 is instantly in a fully charged state because the capacities of the capacitor 1 and the capacitor 2 are C1 << C2. As a result, the capacitor 1 functions to generate a pulse-shaped signal having an amplitude of Vr as indicated by 12 in FIG. 2 in response to the ON / OFF operation of the switch 5, and as shown in FIG. It acts to superimpose the signal on the test voltage. At this time, if the charge amount of the pulsed signal is qp, then qp is qp = C1 × Vr [C]. Therefore, the capacitor 1 is not limited to the function of superimposing the pulsed signal on the test voltage, and is constant. It also has the effect of injecting the amount of electric charge. Since this effect is equivalent to the principle of the charge injection method, the qp corresponds to the calibration charge amount qo in the above equation, the amplitude Vr of the pulsed signal corresponds to the partial discharge starting voltage Uo, and C1 corresponds to Co. To do. Therefore,
The calibration charge amount qo can be obtained from the following formula.

As described above, the present invention realizes a high-voltage type charge injection method by using it together with a high-voltage generator, and further sets the reference voltages Vr and C1 appropriately to obtain a desired calibration charge amount. It is possible not only to freely obtain the above, but also to easily specify the partial discharge inception voltage. Further, as is apparent from the following equation, the desired test voltage Va can be freely obtained by appropriately setting the value of C2.

A second aspect of the present invention relates to a method of confirming the operation of a partial discharge measuring circuit using the pulse signal generating circuit, and more particularly to a method of calibrating the measuring circuit and a method of confirming a noise level. The calibration step (step a) and the noise level confirmation step (step b) of the measurement circuit of the present invention will be described below with reference to the embodiment shown in FIG. 3 and the flowchart shown in FIG. Although FIG. 3 shows an embodiment using a partial discharge measuring device (hereinafter referred to as “measuring device”) equipped with both a high voltage generator and a measuring circuit, the present invention is not limited to the high voltage generator. Even when the test is performed independently of the partial discharge measurement circuit, the measurement circuit can be calibrated and the noise level can be confirmed.

In addition to the measuring device 20, the test lead 21, the pulse signal generating circuit 22, the sample 23, a power source, a jig, etc.
Connect all components required for measurement. At this time, the A terminal and the B terminal of the generating circuit 22 are connected to the corresponding terminals, that is, the test voltage output terminals A ′ and B ′ of the measuring device 20, and the A ′ electrode and the B ′ electrode of the sample 23. Then, C1 is set so that the calibration charge quantity qo becomes a desired value by the above equation.
And Vr are set, and the desired test voltage value V is obtained from the above equation.
Set C2 to be a. However, in the calibration of the measurement circuit, it is not possible to apply a high voltage because it is necessary to remove the generation of unnecessary noise. Therefore, the Va value is set first, and C1, C2, and Vr satisfying this value are set. , The calibration charge quantity qo is calculated, or the partial discharge start voltage Vr is first determined.
However, it is possible to set the values of C1 and C2 so as to obtain the desired test voltage Va. However, when setting the respective values, it is better to calculate the optimum values in advance before starting this step. desirable. After completing the predetermined settings, the measuring device 2
When the test voltage Va is output from 0, Va superimposes a pulse signal equivalent to the discharge phenomenon and the calibration charge quantity qo changes to injected Va '. Then, the measuring circuit is calibrated at Va ', and this step is completed.

Next, the noise level confirmation step (step b)
Will be described. Similar to step a, first, all the components necessary for checking the noise level are connected. Then, using the same procedure and calculation formula as in step a, the calibration charge amount q
o, partial discharge starting voltage Vr, test voltage Va, C1, C
Set a value required for this process, such as 2. However, if the test voltage is specified by a standard, etc., it must first be adapted to that value.Therefore, it is better to calculate the optimum value in advance in consideration of the test or measurement conditions in each standard. desirable. When the test voltage Va is applied from the measuring device 20 after setting these values, Va changes to Va 'into which the pulse signal equivalent to the discharge phenomenon is superimposed and the calibration charge amount qo is injected. Therefore, the noise level is confirmed by the Va '. At this time, if the measured value of the noise level is qo ′, the noise qos of all components is Becomes Therefore, if qo = qo, no abnormal partial discharge phenomenon appears, and if qo ′ ≧ 1.5qo, it is determined that the noise level is 50% or more, and the abnormal noise is detected. The cause of occurrence of is removed, and when it is confirmed that the noise level is 50% or less, the present process is terminated. In addition,
Further, since this process can be independently performed regardless of step a, the order of step a and step b shown in the flowchart of FIG. 4 may be reversed and this step b may be executed first.

[0018]

As described above, the invention of claim 1 realizes the charge injection method by superimposing a pulse equivalent to the discharge pulse on the test voltage signal of the high voltage generator, though it is an extremely simple circuit. The invention of claim 2 using this generation circuit has the drawback of the standard sampling method, that is, the calibration charge and the partial discharge inception voltage cannot be freely set, and the abnormal charge due to a disconnection accident between the connection paths of the respective components. In addition to eliminating the uncertainties in the discovery of, the application of a high voltage using the charge injection method has also been realized, so it is possible to confirm a noise level with extremely high reproducibility. Furthermore, in these inventions, the start-up inspection can be executed in a short time, and since the signal generator and the standard sample are not required, the cost and man-hours can be remarkably improved. Can play.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the invention of claim 1;

FIG. 2 is a diagram showing a signal waveform generated by the invention of claim 1.

FIG. 3 is a diagram showing an embodiment of a calibration method using the invention of claim 1.

FIG. 4 is a flowchart showing a procedure of calibration and confirmation of a noise level.

[Explanation of symbols]

1 capacitor 2 capacitors 3 Reference voltage 4 comparator 5 switches 10 High voltage waveform 11 Voltage waveform across capacitor 2 12 pulse signals 20 Partial discharge measuring device 21 Test lead 22 pulse signal generator 23 sample

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Nagao             Toyohashi Technical Department 1-1 Hibarigaoka, Tenhaku-cho, Toyohashi City             Inside university F-term (reference) 2G015 AA00 BA04 CA01

Claims (2)

[Claims] 1. A comparator, and a first capacitor and a second capacitor connected in series, wherein switching means are connected in parallel across the second capacitor, and the voltage across the second capacitor A calibration pulse generating circuit for a partial discharge measuring circuit, wherein the switching means short-circuits both ends of the second capacitor at a moment when the comparison voltage becomes a comparison voltage of a comparator and becomes higher than a reference voltage. 2. A method for confirming the operation of a partial discharge measuring circuit using the invention described in claim 1, comprising a step of calibrating the partial discharge measuring circuit and a step of confirming a noise level. How to check the operation.