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Transilvania Sud Power Distribution Company , Sibiu , Romania
Department of Electrical Engineering, Technical University Cluj Napoca , Cluj-Napoca , Romania
Working methods for on site testing of insulations:
Gas chromatography (using the TFGA-P200 chromatographer);
Electrical measurements of partial discharge levels using the digital detection, recording, analysis and partial discharge acquisition system, MPD600.
First performed, between 2000–2015, were the chromatographic analyses concerning electrical insulating environments of:
102 current transformers, 110kV. Items in operation, functioning in 110/20kV substations.
38 voltage transformers, 110kV also in operation, functioning in 110/20kV substations.
Then, electrical measurements of partial discharge inside instrument transformers, on site (power substations) were made (starting in the year 2009, over a 7-year period, collecting data until the year 2015) according to the provisions of standard EN 61869-1:2007 "Instrument transformers. General requirements", applying, assimilated to it, type A partial discharge test procedure, using as test voltage the very rated 110kV distribution grid voltage.
Given the results of two parallel measurements, containing:
to this type of failure specific gas amount (H 2) and the quantitative partial discharge' level,
establishing a clear dependence between the quantity of partial discharges and the type and amount of in oil dissolved gases inside equipments affected by this type of defect: partial discharges, was expected.
Of the "population" of instrument transformers subject of the two parallel measurements, the dependency between Q IEC (apparent charge) and (H 2) (hydrogen, gas amount dissolved within their insulating environment) represents a finite assemblage situated between the two limits developed on an empirical basis.
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