| Online monitoring of transformer insulation performance can reflect its internal insulation degradation condition in real time, continuous. And it’s one of the important methods to acquire the condition of power transformer insulation condition. Online monitoring of transformer partial discharge in real-time can judge the insulation state of transformer, and it’s also the reliable means of transformer state maintenance, and can guide the effective maintenance plan. The online monitoring can avoid serious accident of transformer. The online monitoring of partial discharge has very important significance for the whole power system safe, reliable, economic and stable operation.In this paper, we analysis and calculate the over-voltage of transformer by time domain and frequency domain, and we also analysis and calculate the current flow through bushing tap grounding wire which caused by serious partial discharge in transformer. By calculation we get the power frequency leakage current flow through bushing tap grounding wire in different voltage class. Transformer partial discharge on-line monitoring current sensor of wide band has been designed. We researched the frequency characteristic of the capacitance of transformer bushing. We also developed a multi-functional current sensor which can be installed in transformer bushing tap. A telescoping sensor installed in the root of transformer bushing which is based on the principle of Rogowski coil has been designed. We tested and analyzed three kinds of sensor’s performance.Put the developed sensor in the platform of 220kV single-phase transformer. Installation site is high voltage bushing tap grounding wire, low voltage bushing, neutral point grounding wire, iron core grounding wire We install suspended discharge model in transformer internal, through monitor suspended discharge signal produced by model under rated voltage grade, By Analysis the discharge signals we verified the performance and reliability of sensors. |
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