Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Patent
1997-12-08
1999-05-11
Ballato, Josie
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
324536, 324520, G01R31/327
Patent
active
059031573
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to a measuring system that measures electromagnetic noise signals in enclosed high-voltage switchgear having at least two phase-segregated poles, and in particular, to a measuring system that has at least one sensor for each phase in order to detect such noise signals and a detector device connected to the sensors for producing an output signal in the event that noise is detected.
BACKGROUND INFORMATION
An enclosed high-voltage switchgear having phase-segregated poles and an electromagnetic noise measuring system is described, for example, in the article "Operation and Diagnosis Assisting System for Substations," Hitachi Review, vol. 40, no. 5 (1991) pages 359-366. In the measuring system described in this article, a spectral analysis technique is performed on the detected noise signal in order to obtain more information about the nature of the noise inside the enclosed high-voltage switchgear. This type of measuring system, however, presents many sources of error, and the probability of an error occurring increases with the number of sensors.
European Patent A 342,597 describes a measuring system for enclosed high-voltage switchgear, in which various sensors, some of which are the same as each other and some of which are not, detect partial discharge processes, the measured values of which are analyzed with regard to the intensity and duration of their occurrence. When a large enough difference exists between two measured values that are under comparison with each other, it is concluded that there is a fault in the system. Such a large difference can also occur when only a single measured value is recorded, in which case a second value is therefore assumed to be equal to zero. This could also occur if two measured values are recorded by different sensors with a great time difference. Superfluous error messages could possibly be generated in this way.
The article entitled "Proceedings of 1991 IEEE Power Engineering Society, Transmission and Distribution Conference," pages 467-472 (1991), states that irregularities in electric lengths between the sensors and the processing device can be compensated in differential measurements on high-voltage switchgear.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a measuring system that is largely free of interference and that is constructed in accordance with an economical design for an enclosed high-voltage switchgear.
This object is achieved according to the present invention by including in this system a time comparator that measures the difference between the respective times at which each noise signal arrives at a respective sensor of a different phase. The time comparator is also programmed with an adjustable time interval to which the measured arrival time difference between noise signals is compared. If the measured arrival time difference of the noise signals is less than the adjustable time interval, then the time comparator does not generate an output signal for activating other analysis stations, with the result that the system does not generate a warning indication of the presence of noise in the switchgear.
The present invention is based on the observation that many noise signals in the form of electromagnetic waves do not occur inside the enclosed switchgear due to partial discharges or switching operations or moving particles; instead, the radiation may enter from outside the enclosure, e.g., due to radar transmitters. Such external influences produce noise signals, which are not, due to actual faults in the system, however, and therefore they should be segregated in noise monitoring. Such noise signals usually enter at singular points on the switchgear enclosure, e.g., outdoor bushings with large insulator bodies. It has been found that in most cases such noise enters multiple enclosures of different poles, so that noise is detected almost simultaneously at multiple poles. Conversely, the almost simultaneous presence of noise in at least two different phases of a
REFERENCES:
patent: 5107447 (1992-04-01), Ozawa
patent: 5214595 (1993-05-01), Ozawa
patent: 5253180 (1993-10-01), Yamagiwa
T. Fujikawa et al., "Operation and Diagnosis Assisting System for Substations," Hitachi Review, vol. 40, No. 5, pp. 359-366 (1991).
J.M. Braun et al., "Reliability Of GIS EHV Epoxy Insulators: The Need And Prospects For More Stringent Acceptance Criteria," Proceedings of the 1991 IEEE Power Engineering Society, Transmission and Distribution Conference, pp. 467-472 (1991).
Achatz Norbert
Gorablenkow Jorg
Ballato Josie
Siemens Aktiengesellschaft
Solis Jose M.
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