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The test is administered by taking an oil sample from

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The test is administered by taking an oil sample from the tank anddetermining the levels of different dissolved gases, which include acetylene, methane, hydrogen,carbon dioxide, and ethylene [3].This test indicates the presence of PDs as well as providesadditional diagnostic information because different levels of each of the gases can be correlatedto a specific type of fault within the HVT using extensively developed tables.Although this testis widely used, there is some debate as to whether or not the levels of dissolved gas reallycorrelate to a specific type of fault.Some experts argue that the rate of increase of these gases ismore important than the absolute measure of their concentration [5].Another test, HPLC, measures the byproducts of transformer wall insulation breakdown.Because the insulation on the wall of the transformer is made of paper, the breakdown productsare glucose and degraded forms of glucose.The test is administered by evaluating oil samplesfrom the transformer in an offsite lab.However, there are problems with this test as well.Theglucose levels in the oil are very small because glucose is not highly soluble in mineral oil andthe degraded forms of glucose are not very stable.In addition, this test suffers the sameuncertainty as DGA because there are no standard values for glucose concentration and theircorrelation to HVT faults [3].Chemical testing has some limitations that prevent it from being the only method used forPD detection.First, chemical testing does not provide any information about the position of thePD or the extent of the insulation damage.However, further research is being conducted to addchemical “tags” to transformer insulation that would be released and dissolved into the oil in theevent of a PD.If these tags could be manufactured and implemented into new transformerinsulations, then HPLC could provide valuable information about the type of PD fault that hasoccurred within the transformer.However, this does not satisfy the need to elicit positioninformation from chemical PD detection.The second problem is that chemical testing cannot beperformed online.In most cases, the transformers must be taken out of operation to obtain the
8oil sample.In the case of HPLC, the oil sample must be sent outside of the HVT site in order tobe analyzed and results can take a long time to obtain.These problems limit the usefulness ofchemical detection and rule it out as a singular solution to PD detection and positioning.Section 2.2.2: Electrical DetectionElectrical detection focuses on capturing the electrical pulse created by the currentstreamer in the void.These pulses last on the order of single nanoseconds and have measurablefrequency components in excess of 1 MHz [1].The pulse shape, its relative phase locationwithin the AC cycle of the HVT, and the signal intensity all lead to information about the type ofPD fault and the severity of the insulation damage.Electrical measurements are grouped into

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Term
Winter
Professor
prof Nyoman
Tags
Electrical Engineering, Frequency, Signal Processing, hvt, Acoustic Detection Systems

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