JPH0810243B2 - Dielectric breakdown detection method in surge voltage test - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a surge withstand voltage test for electric equipment and electric / electronic equipment, when a surge voltage is applied to a test object,
The present invention relates to a method of detecting whether or not dielectric breakdown occurs.

[Conventional technology]

Generally, a surge voltage withstanding test is performed as one of the tests for confirming the safety of electric equipment and electric / electronic devices.

As a test method that has been widely adopted in the past, a high voltage probe was used for the storage oscilloscope, and the contact at the tip of this probe was EUT / DUT (EUT is the device under test, DUT is the device under test). When simultaneously detecting the breakdown of the EUT / DUT by connecting the output from the surge voltage generator and the output from the surge voltage generator at the same time, gradually increase the applied surge voltage while constantly monitoring the EUT / DUT terminal voltage waveform. While
Alternatively, after fixing a certain surge voltage, repeatedly applying surge voltage until dielectric breakdown occurs, and detecting whether dielectric breakdown has occurred or not by detecting the presence or absence of a waveform break in the voltage waveform, or a dielectric breakdown There is a method of detecting a transient abnormal current that sometimes occurs.

[Problems to be Solved by the Invention]

However, in the former method, first, when connecting the output from the surge voltage generator to the EUT / DUT, it is necessary to consider sufficient insulation against high voltage and maintain reliable conduction to the object to be connected. However, it is extremely difficult to simultaneously connect the contact of the high-voltage probe to the connection point that connects the output from the EUT / DUT and the surge voltage generator, and to satisfy both reliable insulation and conductivity. Usually, the surge voltage used in the test is several KV to several KV.
This is used for general indoor equipment, household appliances, communication equipment, computer systems, devices used for them, and other equipment that receives power from 100 to 240 VAC and is used. When targeting power transmission and distribution facilities and equipment, high voltage of several hundred KV or more is used, but the physical and mental conditions experienced by the tester during the test work dealing with such high surge voltage. In this work situation, unless the waveform of the oscilloscope is constantly monitored for a long time in this work situation, the phenomenon of dielectric breakdown cannot be recognized and understood, and therefore highly accurate test results can be expected. It is extremely difficult to do so.

Further, in the latter method, good results are obtained when the transient abnormal current is extremely larger than the steady current, but when the abnormal current does not differ much from the steady current, only current observation is performed. Even if it is carried out, there is a problem that it may not be possible to detect all of the dielectric breakdown without omission.

Therefore, the problem to be solved by the present invention is to provide a dielectric breakdown detecting method which does not have the above-mentioned problems in the prior art.

[Means for solving the problem]

The present invention has been made for the purpose of solving the above-mentioned problems, and its configuration is such that, when a surge voltage generating circuit is connected to a test object and a surge voltage is applied, the surge voltage and the current at the connection point are The surge voltage and the current are indicated by constantly detecting and differentiating the indicated signal by the voltage value, differentially amplifying both differentiated signals, and comparing the amplified signal with the signal indicating the reference voltage indicating dielectric breakdown. It is characterized by detecting that a dielectric breakdown in which a signal sharply changes occurs in the object.

That is, the inventor of the present invention has conducted extensive research on the dielectric breakdown of a substance, and as a result, the applied voltage and its time are related to the dielectric breakdown of a substance. Therefore, the surge voltage waveform is important in the dielectric breakdown test. It has meaning, and generally dielectric breakdown has a delay time with respect to voltage, but this delay time becomes shorter as the voltage peak value becomes higher. 2 Spatial region (distance in air or liquid It is concluded that, regardless of the solid state, the region where the current density is large) has a large conductivity, and as a result, the voltage between the electrodes decreases, and the time factor of the surge voltage, that is, the voltage waveform The current generated by the breakdown and its time factor are shown in the table as shown in FIG.

Here, the description of FIG. 1 is as follows.

The upper part of Fig. 1 shows the waveform standardized in the standard waveform (JEC-212 of the Institute of Electrical Engineers), which is often used as the surge voltage waveform, in thin lines, with the horizontal axis representing time and the vertical axis representing voltage. There is. In FIG. 1, the maximum peak value P of the voltage is the value at the time when the time t ₁ has elapsed after applying the surge voltage.

Commonly used insulators and gas-sealed discharge tubes,
Alternatively, the dielectric breakdown regarding various discharge gaps occurs at time t ₂ after elapse of delay time td from time t ₁ until the applied surge voltage waveform reaches its maximum peak value. This delay time td is not always a fixed time,
In most cases, there is a certain statistical fluctuation, and the tendency is that the higher the applied surge voltage peak value, the higher the td.
The value becomes smaller and the fluctuation also becomes smaller.

Now, when the breakdown occurs at time t _2, the conductivity of the machining gap becomes rapidly increased, for example, gas or sealed type arrester, also such as in the gap in the air, become almost close to short-circuit the conductivity At the same time, the voltage between the electrodes drops rapidly, and at the same time, a current as shown in the lower part of FIG. 1 is generated between the electrodes. The current value is determined by the ratio of the voltage value and the circuit impedance at time t ₂ .

What is important here is the relationship between the direction of the voltage change and the direction of the waveform showing the current change starting from time t ₂ and reaching the maximum value of the current at time t _3. That is, they completely coincide with each other in time and the directions of the waveforms are opposite to each other. It is conceivable that such a relationship in the direction of the waveform in a transient state is caused only by dielectric breakdown. The thick line portion in FIG. 1 indicates that the waveforms are in the opposite direction.

The present invention utilizes the above principle, when the waveforms indicating the voltage and the current in the above are expressed in opposite directions, it is detected and only that signal is separated and discriminated from other signals, noise, etc., By detecting as a dielectric breakdown detection signal via a differential amplifier circuit or the like, the dielectric breakdown of the test object can be detected extremely easily and reliably.

〔Example〕

 Next, an example of implementation of the present invention will be described with reference to the drawings.

In FIG. 2, 1 is a surge voltage generating circuit, 2 is a circuit under test, 3 is a non-inverting amplifier, 4 is an inverting amplifier, 5 and 6 are differentiating circuits, 7 is a differential amplifying circuit, and 8 is a level comparator. The surge voltage generating circuit 1 and the circuit under test 2 are connected by interposing resistors R ₀ , Rp, Ri between the two circuits, and a signal indicating the detection voltage V and the current I is supplied from this connection portion. It is designed to be retrieved by value.

The signal of the voltage value indicating the voltage V taken out passes through the voltage dividing resistors Rd ₁ and Rd ₂ and then passes through the non-inverting amplifier 3 and the differentiating circuit 5.
The signal of the voltage value indicating the current I that is input to the differential amplifier circuit 7 is also input to the differential amplifier circuit 7 through the inverting amplifier 4 and the differential circuit 6.

The resistance values of the resistors R ₀ , Rp, Ri, Rd ₁ and Rd ₂ indicate the detection voltage V and the detection current I in the differential amplifier circuit 7 before the dielectric breakdown occurs. Make sure that the voltage inputs are equal. As a result, when dielectric breakdown does not occur, no output is output to the point A of the differential amplifier circuit 7.

However, from the surge voltage generation circuit 1 to the test target circuit 2
When a surge voltage is applied to the target circuit 2 and dielectric breakdown occurs in the target circuit 2, the detection voltage indicating the voltage V detected through the voltage dividing resistors Rd ₁ and Rd ₂ and the detection voltage indicating the current I are detected. Are opposite to each other. The signal indicating the voltage V is passed through the non-inverting amplifier 3 and the differentiating circuit 5, and the signal indicating the current I is passed through the inverting amplifier 4 and the differentiating circuit 6, so that only the signals whose waveform directions are different from each other. Are separated and discriminated from the signals and noises and are input to the differential amplifier circuit 7.

The differential amplifier circuit 7 is formed so that there is an output from the point A when the dielectric breakdown of the insulator of the test object 2 occurs, and the output of the point A is compared with the reference voltage ref.V in the level comparator 8. , Is calculated, and is output as a detection signal from the point C.

The surge voltage waveform (original waveform) and the voltage waveforms at each of ,,, and in FIG. 2 are as shown in FIG.

Then, the output at the point C is input to the latch circuit 9 so that the occurrence of the dielectric breakdown is held for an arbitrary time, and the driver 10 connected to the latch circuit 9 is held.
If a warning is issued by the buzzer 11 and / or the light emitting diode 12 or the like via the, the dielectric breakdown can be clearly known.

Incidentally, if a reset switch 13 is connected to the latch circuit 9 and the latch is released by its operation, it is extremely convenient in use. In the above embodiment,
Although the differential amplifier 7 is used, the present invention is not limited to this, and other appropriate means may be adopted.

For example, the same effect can be obtained by using a differential input type oscilloscope, but in this case, the oscilloscope CRT
In order to prevent the tester from reading the screen, it is necessary to add a signal processing function to the oscilloscope that automatically recognizes and discriminates only the antiphase waveform.

〔The invention's effect〕

The present invention is as described above, and paying attention to the fact that when dielectric breakdown occurs, the waveforms showing the voltage drop and the current rise that are peculiar thereto rise (fall) in a completely opposite relationship,
By separating and extracting only that phenomenon from other phenomena, it has become possible to automatically detect the dielectric breakdown phenomenon.As a method for detecting dielectric breakdown in surge withstand voltage tests of electrical equipment and electric / electronic equipment, It is suitable.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the method of the present invention, FIG. 2 is a diagram showing an example of a detection circuit for carrying out the method of the present invention, and FIG.
FIG. 4 is a diagram showing the original waveform of the surge voltage and the waveforms appearing in the part of the detection circuit of FIG. 2, and FIG. 4 is a diagram showing an example of the alarm generation circuit. 1 ... Surge voltage generation circuit, 2 ... Test target circuit, 3 ...
… Non-inverting amplifier, 4 …… Inverting amplifier, 5,6 …… Differentiation circuit, 7 …… Differential amplification circuit, 8 …… Level comparator

Claims (1)

[Claims] 1. When a surge voltage generating circuit is connected to a test object and a surge voltage is applied, the signals indicating the surge voltage and current at the connection point are always detected by a voltage value and differentiated, and both signals are differentiated. Is differentially amplified, and the amplified signal is compared with a signal indicating a reference voltage indicating a dielectric breakdown, thereby confirming that the dielectric breakdown in which the signals indicating the surge voltage and the current change sharply occurs in the object. A method for detecting dielectric breakdown in a surge voltage test, which is characterized by detecting.