Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
1999-08-25
2001-11-27
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S547000, C324S553000, C324S726000, C340S646000
Reexamination Certificate
active
06323655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for detecting partial discharges in an electrical apparatus placed in a tank filled with oil, wherein the tank wall is provided with at least one drain tap.
Belonging to the category of such apparatus are inter alia generator, coupling and distribution transformers of large capacity. These are placed in a tank filled with oil.
Other categories of apparatus which are placed in a tank filled with oil, such as compensating coils, are however by no means excluded.
2. Description of the Related Art
In order to determine the quality of operation of such an apparatus, particularly in respect of the quality of the applied insulation materials and deriving therefrom the anticipated operating time until a subsequent failure and the remaining life expectancy, the detection of partial discharges is of the greatest importance. Partial discharges often represent the prelude to destructive processes in such an apparatus.
According to presently known electrical measuring techniques, use is made of an apparatus wherein the transformer is taken out of operation, the transformer is placed in a measuring arrangement and a measurement is then performed. It is possible herein for such a measurement also to be carried out during operation. In order to arrange the measuring equipment and remove it after the measurement has been performed, the transformer must however be taken out of operation. It will be apparent that this is less than desirable on account of the economic consequences of taking a transformer out of operation, particularly when it is a generator transformer.
SUMMARY OF THE INVENTION
The object of the present invention is however to provide a device with which it is possible to detect possible partial discharges in such an apparatus without the apparatus having to be taken out of operation.
It is also an object of the present invention to provide a method for detecting partial discharges in an electrical apparatus placed in a tank filled with oil, the tank wall of which is provided with at least one drain tap, wherein the apparatus likewise does not have to be taken out of operation.
This object is achieved with such a device, wherein the measuring device comprises a probe which is mounted on a carrier which is movable through the opened drain tap into the tank.
This object is further achieved with such a method, wherein a sleeve is initially placed on the flange of the drain tap and a carrier which is movable in the sleeve and on which a probe is placed is subsequently moved through the opened tap until the measuring surface of the probe at least coincides with the inner surface of the tank wall, and the measurement is then performed.
As a result of these two measures it is possible to test a transformer or other electrical apparatus for partial discharges, without the apparatus having to be taken out of operation.
It is pointed out herein that in the majority of such apparatuses drain taps are provided for drawing off the oil, which drain tap can be easily used for introducing the probe according to the invention.
It is further pointed out that performing measurements for partial discharges in a closed tank inside which an electrical apparatus is situated is per se known from the field of closed switching gear. Herein however, the probe is already arranged fixedly in the tank during manufacture of such equipment and provided with connecting means which are guided to the outside, so that such a measurement can be performed using such a probe. This relates however to closed switching gear filled with SF
6
gas.
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Fu Yan Hong
Rutgers Wijnand Reijer
Banner & Witcoff , Ltd.
Brown Glenn W.
Hamdan Wasseem H.
N.V. Kema
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