Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Patent
1987-02-13
1988-10-18
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
324158MG, G01R 3132
Patent
active
047790512
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a coupling unit for the operative monitoring of the high-voltage windings and the connected electric output leads in electric high-voltage machines and apparatus, according to the preamble of claim 1.
2. Description of the Related Art
Such a coupling unit is known in principle, as will be explained in greater detail further on referring to FIG. 1. The stator winding of the turbo-generator comprises here a transformer connected between the common Y-point of the winding and ground potential, a low impedance winding of the transformer or an additional high frequency transformer being connected as a measuring impedance. This known coupling unit and the corresponding measuring method are not sensitive enough; it is impossible to discriminate between the individual phases of the high-voltage winding. Although partial discharges in the high voltage insulation of the winding as well as breaking spark currents in the case of possible conductor interruptions or between winding bars and lamination stacks are surge currents of short duration and pulse-like shape, which are easy to determine by high frequency measuring methods the known coupling unit is not yet satisfactory as far as its sensitivity, in particular with respect to partial discharges on the side of the generator output leads.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a coupling unit improved over this, of which the partial discharge measuring signals called TE measuring signals for short in the following, can be correlated with certainty to the individual phases of the stator winding and which reacts more sensitively also to TE measuring signals which have their origin on the side of the generator output leads, so that in certain cases also fault signals from the connected machine transformer can be received. The coupling unit should be usable for different test objects such as model samples, portions of windings or running turbo generators and be independent of the existence of a Y-point of the stator winding.
According to the invention, the stated problem is solved with a coupling unit for operational monitoring of the high-voltage windings and their thereto-connected output leads in electric high-voltage machines and apparatus, especially of the three-phase stator winding in the turbo-generators including their generator output leads and/or in transformers and converters by means of determining partial discharges and breakdown spark measurement, wherein the above-mentioned machine and apparatus are connected together via generator output leads and are connected to ground via network protection capacitors, wherein the coupling unit is coupled selectively to one each of the three legs of the generator output lead, wherein for said purpose the network protection capacitors for each phase are connected via a respective measuring impedence to ground potential, and wherein the shielded measuring lines leading from the measuring voltage terminal of the measuring impedance to the partial discharge measuring device are conducted through a filter.
The advantages attainable with the invention are in particular that the determination of winding defects is made possible for each individual phase of the stator winding of an electric high-voltage machine in general and of a turbo-generator in particular, and also the sensitivity, i.e. the signal to noise ratio is improved. The coupling unit is well suited for installation as a retrofit unit in existing power generation plants as well as in the context of new manufacture. Due to the high sensitivity it contributes substantially to an early damage or fault detection in large electrical machines because, for instance, winding defects generate through the interruption of partial conductors, a discontinuation of potential controls or discharges due to the motion of the conductors in the slot, high-frequency sparks or partial discharges. By continuously monitoring the TE measurement signals during operation, the g
REFERENCES:
Wilson et al.; IEE Proceedings, vol. 132, Pt. B, No. 5, Sep. 1985, "Discharge Detection Techniques for Stator Windings," pp. 234-244.
Nieschwietz et al.; "Teilentladungsmessungen an Hochspannungstransformatoren als Mittel der Qualitaks Kontrolle", Qualitakskontrolle on Hochspannungs Transformatoren, etz-a Bd. 97 (1976) Hill, pp. 657-663.
IEEE Transactions on Power Apparatus and Systems; vol. PAS-98, No. 5, Sep./Oct. 1979, IEEE, New York (U.S.) M. Kurtz et al.: "Generator Insulation Diagnostic Testing", pp. 1596-1603; bottom of p. 1596, left col., line 38--p. 1596, right col., line 4; Figure 2.
Patents Abstracts of Japan, vol. 7, No. 282 (P-243) (1427) Dec. 16, 1983, & JP-A-58-158569 (Tokyo Shibaura Denki K.K.) Sep. 20, 1983.
Patents Abstracts of Japan vol. 7, No. 247 (E-208) (1392) Nov. 2, 1983 & JP-A-58-133143 (Tokyo Shibaura Denki K.K.) Aug. 8, 1983.
Siemens-Energietechnik 6 (1984) Issue 6, pp. 286-289 "Wicklungsuberwachung von elektrischen Maschinen durch Hochfrequenz-Messverfahren.
Grunewald Peter
Koziel Reinhold
Eisenzopf Reinhard J.
Greenberg Laurence A.
Kraftwerk Union Aktiengesellschaft
Lerner Herbert L.
Miele Anthony L.
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