| 摘要 |
FIELD: electric measurement technology; testing high-voltage potential transformers. SUBSTANCE: device for testing potential transformers has capacitive voltage divider in the form of measuring circuit set up of capacitors series-connected through coaxial connectors, each capacitor being provided with two working electrodes in the form of shells of different height mounted on capacitor case and electrically connected to capacitor leads so that first of them is arranged around one of capacitoir leads and plates and other sleeve is around other capacitor lead, and also it has two pairs of shielding electrodes in the form of shells of different height arranged around working electrodes of capacitor and isolated from each other and from working electrodes by means of insulators; ends of working and shielding electrodes are separated by means of insulating ring. Device also has two equipotential shielding circuits of which the first is set up of capacitors series-connected through coaxial connectors, each provided with two working and two shielding electrodes similar in design to those of measuring circuit, each capacitor of first shielding circuit being connected to first pairs of measuring-circuit shielding electrodes so that shielding and working electrodes are placed at equal potentials. Second shielding circuit is built up of series-connected capacitors with trimming capacitors connected in parallel to them; each capacitor of second shielding circuit is connected to second pairs of measuring-circuit shielding electrodes and to shielding electrodes of first shielding circuit so that working and shielding electrodes are placed at equal potentials. Null-indicator with high input resistance is used to determine equality of potentials across working and shielding circuits; null-indicator input is connected during device verification in turn to all capacitors of measuring and second shielding circuits and its case, to respective capacitors of first shielding circuit; capacitors of second shielding circuit are selected by means of trimming capacitors considering the effect of stray capacitance on ground so that balance null-indicator reads zero. EFFECT: improved accuracy in measuring transformation ratio of instrument transformers due to metrological verification of device on site of operation by using two independent methods; step-by-step shorting-out of part of divider capacitors and off-line testing. |
