Research On Error Analysis And Impact Factors Of 10kV Metering Current Transformer

The current transformer plays a very important role in the energy measurement and electrical protection of the 10 kV distribution network.The current transformers for measurement are widely used,and are closely connected with both the power supply and the power consumption.In actual operation,due to the influence of factors such as the temperature of the conductor heat and environmental changes,the electromagnetic field caused by the surrounding flow conductors,inaccurate measurement of the current transformer for 10 kV measurement often occurs.If the unreasonable measurement continues,it will bring inestimable economic losses to both the power supply and the power consumption.Therefore,studying the error principle of the current transformer for 10 kV measurement and analyzing the influence mechanism of external factors on the error are of great significance to ensure the accuracy of current transformer measurement.At present,domestic and foreign scholars have conducted a series of studies on the error principle of 10 kV measurement current transformers and the analysis of external influence factors.Studies have shown that in actual operation,single-phase grounding,DC bias,humid rain,extreme temperatures,and electromagnetic fields will all affect the error of the current transformer for measurement.Extreme temperature and electromagnetic environment are more common influencing factors.The degree of influence is still unclear,and quantitative research is still lacking.This paper takes the widely used 10 kV metering current transformer as the research object,and carries out theoretical,simulation and experimental research on its error principle,external factor influence mechanism,and external factor’s quantitative influence on error.First,this article systematically analyzes the working principle of the current transformer for measurement,and calculates the measurement error during normal operation.Further,when there are external factors such as temperature,magnetic field,and electric field,error calculation formulas are derived based on different external factors.It can be known from the formula that the increase in temperature makes the total impedance and permeability of the secondary circuit increase.However,the total impedance and permeability of the secondary circuit have positive and negative correlations with the errors,respectively.Therefore,it is impossible to qualitatively judge the trend of change.The strength of the magnetic field is related to the current of the external current-carrying conductor.The larger the magnetic field and the interlinking magnetic flux of the winding,the greater the error.The strength and frequency of the electric field determine the strength of the induced magnetic field,and the position of the current transformer determines whether the induced magnetic flux can interlink with the winding and affect the error.According to this,the larger the magnetic field strength and the degree of flux linkage,the larger the qualitative trend of the error.Secondly,in order to quantitatively analyze the error,this paper conducted a simulation analysis of the influence of external factors such as temperature and active power frequency magnetic field on the error of 10 kV measurement current transformer.A simulation model is established for the current transformer.Factors such as the temperature of the winding and the iron core,the magnetic induction strength of the space where the current transformer is located,and the current transformer primary current,load,placement and other factors are simulated variables.The secondary current is obtained through simulation calculation,and the error is obtained after the post-processing,and the variation rule is analyzed.Simulation analysis shows that the higher the temperature of the core and the winding within-40 ～ 80 ℃,the smaller the error.In an active magnetic field,the greater the magnetic induction intensity,the greater the mutual inductance between the external current-carrying conductor and the winding coil,and the greater the error.In severe cases,it may cause out-of-tolerance.The simulation results are consistent with the trend of theoretical analysis.Finally,this paper simulates the experiment of the influence of temperature,magnetic field and electric field on the error of 10 kV measuring current transformer,and tests the quantitative change of the error of 10 kV measuring current transformer.The test results show that temperature and magnetic field will reduce the metering performance,but the effect of the electric field on the metering performance is minimal.In extreme temperatures or complex electromagnetic field environments,temperature compensation or electromagnetic shielding measures must be taken.