| Metal oxide arrester(MOA)is the electrical equipment to suppress the overvoltage of the power network and to protect other equipment from the attack of excessive voltage.MOA valve slices has excellent nonlinear characteristics,so there is no internal series clearance,but under the action of power frequency voltage,the continuous leakage current flows through MOA valve slices.The resistive component of this current causes heating and loss of the MOA and is also a reflection of dampness and deterioration of its valve.Therefore,the measurement of resistance current monitoring is very important to reflect the insulation state of MOA.Measuring the MOA resistive current requires synchronous measurement of the grid voltage and the MOA full leakage current.At present,the voltage signal is usually obtained through the secondary side of the voltage transformer.When the MOA resistive current is online or the live detection device is connected to the secondary terminal of the transformer,it will cause a short circuit at the secondary side,which will affect the operation safety of the power grid.Based on the shortcomings of current voltage acquisition methods,this paper studies a method to reconstruct the grid voltage based on the leakage current of capacitive equipment and extract the MOA resistive current.This method can overcome the shortcomings of safety and stability when MOA resistive current is used to measure the sampling grid voltage.This paper mainly does the following work:(1)The correlation between MOA valve slices aging and resistive current was studied.The accelerated aging experiments of MOA valve slices were carried out.The relationship between MOA resistive current and the aging degree was studied from the changing trend of the Frequency domain dielectric spectrum(FDS)and the DC volt-ampere characteristic curve.(2)The simplified high-frequency model of capacitive equipment and the voltage reconfiguration algorithm based on leakage current are carried out.Based on the preventive test and FDS test data of the capacitive equipment,the power frequency models and simplified high frequency models of the capacitive equipment were established.This paper studies power grid voltage reconstruction algorithm based on capacitive equivalence model and leakage current.(3)Build the voltage reconstruction simulation based on the leakage current of capacitive equipment,study the voltage reconstruction of multiple harmonic voltage superposition simulation,and carry out error analysis;A test platform for leakage current under arbitrary high voltage waveform of true capacitive electrical equipment was built,and the reconstructed voltage and the tested voltage were compared and analyzed.(4)The MOA resistive current experiment platform was built based on the leakage current of capacitive equipment to reconstruct the voltage.Based on the measurement of leakage current of capacitive equipment,the MOA resistive current without voltage transformer voltage reference can be accurately measured,and the error analysis is carried out.Write MOA resistance current detection software based on voltage algorithm. |
