JPH0237994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormal increase detection device for DC leakage current, which is particularly suitable for detecting an abnormal increase in DC leakage current during DC tests of high-voltage cables, high-voltage rotating machines, etc. The present invention relates to an apparatus, and its purpose is to provide an abnormal increase detection apparatus for DC leakage current that can automatically detect an abnormal increase in DC leakage current during a DC test of a test object.

The features of the present invention include a minimum value storage circuit that stores a predetermined minimum value of DC leakage current, and a measurement signal that compares a signal from this minimum value storage circuit with a measurement signal corresponding to the current value of DC leakage current. A comparator that outputs an abnormal DC leakage current increase signal when the signal is large, and a comparator that outputs an abnormal DC leakage current increase signal when the signal is large, and a DC leakage current that starts to decrease when the above voltage is applied to prevent detecting an increase in DC leakage current immediately after voltage is applied to the device under test. The present invention also includes an erroneous detection prevention means for preventing the comparator from outputting an abnormal DC leakage current increase signal.

The present invention will be explained in detail below using examples shown in the drawings.

The figure is a block diagram showing an embodiment of the DC leakage current abnormal increase detection device of the present invention. In the figure,
The DC leakage current a is converted into a voltage by a current-voltage converter 1, and further logarithmically converted by a logarithmic converter 2 to become a voltage signal b. The voltage signal b is first amplified by the degree of amplification K
A maximum storage circuit 4 stores the signal c and the maximum value of the DC leakage current, which is amplified by the operational amplifier 3.
The comparator 5 compares the maximum value signal d from the maximum value signal d, and the comparator 5 outputs a signal e when the signal c becomes smaller than the maximum value signal d.

6 is a minimum value storage circuit in which the minimum value of DC leakage current is stored in advance;
Normally, when signal b is input, it outputs a signal corresponding to signal b, but when signal e is input from comparator 5, it operates and outputs the lowest value signal. The signal from the lowest value storage circuit 6 is amplified by an operational amplifier 7 with an amplification factor n to become a signal f. This signal f and signal b are compared by comparator 8, and when comparator 5 is not outputting signal e, signal f and signal b are the same, so the DC leakage current abnormally increases. Although the signal g is not output, when the DC leakage current, that is, the voltage signal b, starts to decrease after the voltage is applied and the signal e is output from the comparator 5, the lowest value storage circuit 6 is activated, so the lowest value storage circuit The comparator 8 compares the signal f from the operational amplifier 7 corresponding to the lowest value signal output from the operational amplifier 7 with the voltage signal b at that point, and when the signal b becomes larger than the signal f, the DC leakage current is increased at that point. An abnormal increase signal g is output.

Therefore, in a DC test of a test object such as a high voltage cable or a high voltage rotating machine, if the DC leakage current increases abnormally, it can be automatically detected.

As described above, according to the present invention, there is an effect that an abnormal increase in DC leakage current during a DC test of a test object can be automatically detected.

[Brief explanation of drawings]

The figure is a block diagram showing an embodiment of the DC leakage current abnormal increase detection device of the present invention. 1: Current voltage converter, 2: Logarithmic converter, 3,
7: Operational amplifier, 4: Maximum value storage circuit, 5, 8:
Comparator, 6: lowest value storage circuit.

Claims (1)

[Claims] 1. A minimum value storage circuit that stores a predetermined minimum value of DC leakage current, and a signal from the minimum value storage circuit that is compared with a measurement signal corresponding to the current DC leakage current value. a comparator that outputs a DC leakage current abnormal increase signal when the measurement signal is larger;
In order to avoid detecting an increase in DC leakage current immediately after voltage is applied to the test object, an error is made in which the comparator does not output an abnormal DC leakage current increase signal until the DC leakage current starts to decrease when the voltage is applied. A DC leakage current abnormal increase detection device comprising detection prevention means. 2. The erroneous detection prevention means includes a maximum value storage circuit that records the maximum value of the DC leakage current, and compares a signal from the maximum value storage circuit with a measurement signal corresponding to the current DC leakage current value to prevent erroneous measurement. 2. The abnormal increase detection device for direct current leakage current according to claim 1, further comprising a comparator that outputs a signal that stops the operation of the minimum value storage circuit when the signal is smaller.