STATIC VOLTAGE SOURCE USE TO SUPPLY PARTIAL DISCHARGE MEASURING CIRCUITS AT INSTRUMENT TRANSFORMERS
Journal Title: ANALELE UNIVERSITATII DIN CRAIOVA - Seria Inginerie electrica - Year 2010, Vol 34, Issue 34
Abstract
The paper presents the implications of static voltage source use in the partial discharge (PD) measuring circuit at instrument transformers. The economic advantages deriving from the use of such sources must be correlated with the technical requirements dealing especially with the sensitivity of PD measuring circuit. So, the paper presents the evaluation of the common mode disturbances introduced by the said sources and the solution adopted for their attenuation. The authors evaluated the common mode disturbances in the PD measuring circuit, including the static voltage source, both by their direct measurement using a disturbance measuring instrument and by the way they were quantified by the PD measuring system. So, it could be rendered evident that at the same voltage level (5kV) and different frequencies (50Hz, 100Hz), disturbance presence influenced the PD measuring system sensitivity not allowing the measuring of a PD level lower than 8pC. The solution for common mode disturbance attenuation consisted in using an insulating transformer at the output of the voltage source, that represents an efficient way to interrupt the grounding loops especially in the case of low and medium frequency disturbances. The PD measuring circuit which integrates the solution for common mode disturbance attenuation was experimented for the complete sequence testing of two 24 kV instrument transformers, current and voltage. Besides the problems related to the correlation of the parameters: high voltage, low voltage, current absorbed at different testing frequencies (50Hz,100Hz) defining the limits determined by the source power, a circuit background noise lower than 1.2pC was rendered evident indicating its very good sensitivity.
Authors and Affiliations
Tania NICOARĂ, Dorin POPA, George MIHAI
Keywords
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