JPS59122964A - Method and apparatus for automatically detecting dc leak current kick - Google Patents

Abstract

PURPOSE:To automatically perform the kick judgement of a DC leak current, by judging DC leak current kick on the basis of the code change of the change portion in the minute time of the DC leak current converted to voltage and the lasting time thereof. CONSTITUTION:A DC leak current is treated with a logarithm converter 2 and a differentiation circuit 4 while converted to voltage by a current-voltage converter 1 and the code of the change portion in a minute time is generated from a code converter 5. Clocks passing AND circuits 7A, 7B respectively responding to the output of the converter 5 and the output through an inverter 8 are counted by counters 9A, 9B to measure the change of the code and the lasting time thereof. On the other hand, the resettings of the counters 9A, 9B are controlled through a monostable multivibrator 10A responding to the output of the converter 5 and a figure-up signal at the time of definite number counting outputted by the counters 9A, 9B when the rising and falling of voltage succeeds over a time of the time constant or more of the multiplier 10A is outputted as a kick judging signal through an AND circuit 11 to perform the automatic kick judgement of the DC leak current. In this case, the judgement of a kick level is similarily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for measuring DC leakage current in DC energization insulation diagnostic testing of high-voltage cables and the like.

When a constant DC voltage is applied between the cable conductor and sheath, the current flowing in the circuit is a displacement current that flows for a short time immediately after the voltage is applied, an absorption current that flows while attenuating for a relatively long time, and changes over time. It is a combination of leakage currents that do not occur. Displacement current is of short duration and is not a problem, but absorption current and leakage current are important, and their measurement is extremely important in determining cable quality. In particular, when there is a sudden change in the sum of the absorbed current and leakage current that approaches the leakage current as described above, the so-called kick phenomenon, this is often due to a large discharge due to a local defect in the cable insulation. Measuring kicks is extremely important.

Conventionally, such kick measurements have been made by directly reading and recording a meter using a DC ammeter, or by recording on an X-Y recorder or the like. Therefore, the presence or absence of a kick and its magnitude are highly dependent on human judgment and the response speed of the recorder, resulting in reliability problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for automatically determining the kick of DC leakage current, and an apparatus for carrying out the method.

According to the present invention, DC leakage current is converted into voltage, and the
To measure the change in the sign of the voltage change over a minute time and the duration, and when the voltage rises for a certain period of time and then falls for a certain period of time, it is determined to be a kick, and the peak level of the kick at that time is held. This will achieve the above objectives.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below based on a circuit for implementing the method of the present invention shown in the drawings.

The extracted leakage current is input to the terminals 12 and 12 and is converted into a voltage by the current-voltage converter 1, and the voltage thus obtained is logarithmically converted by the logarithmic converter 2.

The output of the logarithmic converter 2 is applied to an upper limit peak detection circuit 3A and a lower limit peak detection circuit 3B having an output terminal 14, and is differentiated by a differentiation circuit 4, and its sign is determined by a sign determination circuit 5, and the leakage current is detected. Information regarding whether the increase or decrease is given to one input of the AND circuit 7A, and the information is inverted by the input signal 8 to the AND circuit 7A.
Give it to B's input.

On the other hand, the clock signal from clock generation circuit 6 is applied to the other input of AND circuits 7A and 7B, and the logical product between the clock signal and the output of the determination circuit is applied to counters 9A and 9B, respectively. By doing this, the counter 9A counts the clocks while the leakage current is increasing.
While the clock is decreasing, the counter 9B divides the clock.

Each of the counters 9A and 9B outputs a carry output when a certain number or more is divided, and these outputs are output to the AND circuit 1.
Added to 1.

On the other hand, the output of determination circuit 5 is applied to one-shot multivibrators IOA and IOB. The output of multinomial ibrator IOA is applied to the reset terminals of counters 9A and 9B. Therefore, when the sign determination circuit 5 outputs an output indicating an increase in leakage current, the counters 9A and 9B
is cleared and the upper limit peak detection circuit 3A is reset.

With this configuration, when the return current monotonically decreases as usual, only the counter 9B operates, and no output is generated at the output terminal 15 of the AND circuit 11.

When the leakage current starts to rise rapidly due to the kick, the counters 9A and 9B are reset by the output of the determination circuit 5, and the upper limit peak detection hold circuit 3A is also reset. Subsequently, the number of clocks is counted by the counter 9A during the rise, and the one-shot multivibrator IOA
If the increase continues for a certain period of time determined by the time constant of , a carry is sent to the AND circuit 11.

Next, when the leakage current starts to decrease, the counter 9A stops counting, the circuit 3A enters a hold state, and outputs its peak value to the output terminal 13. At the same time, the counter 9B starts counting, and when the decrease continues for a certain period of time determined by the time constant of the multivibrator circuit 10A, the counter 9B outputs a carry i to the N,D circuit 11. At this time, if there is a carry output from the counter 9A, an output is output to the output terminal 15 of the AND circuit 11.

That is, when the carry output of the counters 9A and 9B occurs, in other words, when the leakage current continues to rise and fall for a time longer than the time constant of the multi-pibrator circuit 10A, it is determined as a kick. This is instructed to the output terminal 15 of the AND circuit 11, and the kick level is given to the output of the hold circuit M3A.

Terminal 13,1. Such kick judgment information in i, 15 can be automatically displayed digitally by adding a display device consisting of a counter and an A/Df converter, and furthermore, it can be automatically recorded by providing an appropriate recording means. It is clearly possible.

As described above, the circuit of the present invention automatically determines and measures the kick phenomenon, which was conventionally left to the judgment of the measurer, and the number and level of kicks, which were limited by the response speed of the X-Y recorder. It becomes possible. Therefore, the present invention is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram for implementing the method of the invention. ■... Current-voltage converter, 2... Logarithmic converter, 3A
. 3B...Peak detection hold circuit, 4...Differential circuit, 5...Sign determination circuit, 6...Clock generation circuit, 7
A. 7B, 11...-A, ND circuit, 8... Inverter, 9A. 9B... Counter, IOA, IOB... One-shot multi-noise break circuit. T l Drawing procedure amendment (spontaneous) 1. Indication of the incident 1982 Patent Application No. 232355Z Name of the invention Direct current leakage current kick automatic detection method and device Address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo No. 4, Agent Address: 100 Address: 2-1-2 Marunouchi, Chiyoda-ku, Tokyo 11111° Contents of the amendment to the detailed description of the invention in the specification subject to the amendment (1) Page 6, line 10 of the specification Correct the word ``to achieve'' to ``to achieve.''that's all

Claims (1)

[Claims] 1. A certain period of time after the voltage has increased for a certain period of time, which is obtained by converting DC leakage current into voltage and measuring the change in sign of the change in voltage over a minute time and the duration of that sign. A direct current leakage current kick automatic detection method comprising determining a drop in voltage as a kick and holding the peak level of the kick. 2. A current-voltage converter that converts DC leakage current into voltage, a holding device that holds the peak value of the converted voltage, a differentiating circuit that differentiates the voltage, and determining the output sign of the differentiating circuit. 1. An automatic direct current leakage current kick detection device comprising: a sign determining device for detecting a sign determining device; a device for limiting the duration of a specific output of the sign determining device; and a device for detecting the output for a period longer than the limited duration.