Maschinenfabrik Reinhausen Gmbh

Junliang Wu

Karsten Viereck

Ulrich Sundermann

Udo Hertel

A method monitors capacitor bushings for an AC mains. The mains has first-third phases, associated with first-third mains lines, capacitor bushings, and mains voltages. Each capacitor bushing has a conductor, surrounded by foil, connecting its mains line. The method includes: at a first instant, for each phase: a first reference voltage phasor is determined; and a foil voltage present between the respective foil and ground potential is detected and a corresponding first foil voltage phasor is determined; at a second instant, for each of the phases: a second reference voltage phasor is determined; the foil voltage is detected and a second foil voltage phasor is determined; for each capacitor bushing: a loss factor change is calculated based on the respective reference voltages and foil phasors and those of the adjacent capacitive bushing; and a monitoring signal is generated based on a comparison of the loss factor and a tolerance value.

Method and apparatus for monitoring the loss factor of capacitor bushings

A method monitors capacitor bushings of a three-phase AC mains, which has first, second, and third mains lines respectively associated with first, second, and third: phases, capacitor bushings, and mains voltages. Each of the capacitor bushings has: a conductor connected with the associated mains line, and an electrically conductive foil enclosing the conductor. The method includes, for each of the phases: determining, at a predetermined initial instant for a characteristic variable, which is characteristic for the respective capacitor bushing, a corresponding characteristic value; determining, at a predetermined later instant after the initial instant for the characteristic variable, a corresponding normalised characteristic value in dependence on the respective characteristic value and/or on at least one of remaining characteristic values; and checking whether the normalised characteristic value has impermissibly changed.

Method and device for monitoring capacitor bushings for an alternating-current grid

A three-phase alternating current mains has capacitor bushings that each have a conductor connected with one of the mains lines of the alternating current mains and an electrically conductive lining surrounding the conductor. These bushings are monitored by first determining an upper capacitance and a lower capacitance for each bushing and then detecting a measured voltage between the respective lining and a ground potential at each capacitor bushing. An actual capacitance for each capacitor bushing is calculated that depends on the respective measured voltage and the respective lower capacitance as well as on the measured voltage, the lower capacitance, and the upper capacitance of one of the other capacitor bushings. For each capacitor bushing the respective upper capacitance is compared with the respective actual capacitance and a monitoring signal is generated that is dependent on the results of the capacitance comparison.

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Wuppertal, Germany

Junliang Wu