Research On XLPE Power Cable Main Insulation Conditioning Monitoring And Measuring Methods

Part One Research on Measuring of Resistive Current Passing Through XLPE Cable With Applying AC Voltage: By many tests,It is found that mains frequency is not sensitive to the mechanical fault of power cable main insulation.Accordingly,a new method that the fault of power cable main insulation is measured by measuring the resistance component of leakage current is put forward. The capacitance current compensation is a common method to measure the resistance current.Based on capacitance current compensation method,We have desighed the breadboard circuit by which to measure resistance current through power cable main insulation.And we get a great deal of available data by many tests.By researching these data it is concluded that resistance current has very diffrence which is measured under various power cable insulation flaws.We can conclude that power cable various flaws can be availably detected by measuring resistance current through power cable main insulation. The resistance component of leakage current through XLPE power cable main insulation is measured by the resistance current testing instrument.By the resistance component,We can monitor performance of XLPE power cable main insulation. Accordingly we can estimate operating condition of the power cable by the resistance component. The principle of XLPE power cable resistance current testing instrument is precise.And it can compensate different harmonic components,get the waveform and the peak value of resistance current,and get total power generated different harmonic voltages. Part Two The Application of AC Voltage Superposition Method in Cable On-line Insulation Monitoring and Measuring: Based on AC voltage superposition method,We have designed XLPE power cable main insulation on-line monitoring instrument which includes hardware and software.The technique key of hardware is on how measuring 1Hz minute deteriorate signal which is disturbed by line-frequency signal,high-frequency signal and line stray capacitance.The whole software monitoring system includes main insulation monitoring system and metal sheathing insulation monitoring system. It can on-line measure the condition of the cable insulation by which the cable can be judged whether to continue to operate or not.Also it can realize on-line monitoring to the condition of the power cable main insulation.In this way,The amount of cut-off reparing is greatly reduced. Relative to other on-line measuring methods,The AC voltage superposition method has obvious predominance.Mainly,its merits include simple measuring,on-line monitoring and measuring,strong anti-interference ability,and high precise and so on.