Research On The Measurement Accuracy Of Voltage Sensors Based On The Principle Of Capacitive Coupling

The accuracy and reliability of voltage measurement are the primary means to ensure the safety and reliability of the grid.At present,electromagnetic transformers(PT)or capacitive voltage dividers(CVT)are commonly used in distribution networks to achieve high-precision transmission of high-voltage electrical to low-voltage signal quantities.However,problems include large size,complex insulation,and limited installation location.Voltage sensors based on capacitive coupling use precisely designed structural capacitors as sampling capacitors and perform voltage reconstruction through capacitive coupling relationships to obtain the measured information characteristics,which have the potential for low-cost,easy installation,and multi-point distributed measurement.However,the presence of coupling capacitance makes such sensors susceptible to interference from external conductors and highly susceptible to the influence of measurement objects and scenarios during practical installation and application,resulting in unstable gain and,thus,measurement errors.In addition,the intricacies of the sensor equivalent theoretical model make it difficult to pinpoint the main factors affecting measurement accuracy during the research process.Therefore,the basic principle and voltage transmission characteristics of capacitively coupled voltage sensors are first analyzed and studied in this paper,and the key factors affecting measurement accuracy are also proposed in this paper;combined with the highprecision measurement requirements of sensors in practical installation applications,the sensing characteristics of two types of voltage sensors,floating-ground and nonintrusive,are thoroughly studied,the mechanism of the influence of coupling capacitance on sensor measurement is exhaustively analyzed,and The optimization methods for the improvement of measurement accuracy of each are proposed.The details of this paper are as follows:1)The variation characteristics of the coupling capacitance of capacitively coupled voltage sensors under the action of various external factors are studied and analyzed,and the mechanism of the influence of the coupling capacitance on the voltage transmission relationship is analyzed by steady-state modeling.Based on this,a new capacitive equivalent theoretical model is established.2)Methods to improve the measurement accuracy of floating-ground and nonintrusive voltage sensors are proposed based on circuit equivalent transmission characteristics and finite element structural parameter analysis.The best sensor installation plan for the floating ground voltage sensor for transmission line voltage measurement is proposed.That is,the installation height of the sensing probe is better than 3m when the variation of coupling capacitance does not exceed 0.58%;if there is an insulated pole tower near the sensor,the installation is best from the insulated If there is an insulated tower near the sensor,the best installation is more than 1m from the insulated tower,and the change rate of the voltage division ratio does not exceed 2.5%at this time.In addition,impedance transformation is proposed to improve the measurement accuracy of floating-ground and non-intrusive voltage sensors.3)Designed and built the floating ground voltage sensor and the experimental platform.The maximum relative error was 0.89%,and the phase difference was 0.68°in the(100V-300V)industrial frequency voltage test.The maximum relative error is4.68% in the(600V-10 k V)industrial frequency voltage test.Meanwhile,the accuracy error of this method after reaching a specific height is only 0.88%,and the maximum difference is 0.52% for the multi-wire diameter conductor test.Moreover,the maximum relative error of the voltage reconstructed using the self-calibration method on the measurement platform within 3m is 1.66%.In addition,the non-intrusive voltage sensor was designed and fabricated.The experimental platform was built,and the maximum relative error in the(100V-300V)industrial frequency voltage test was 0.89%,the phase difference was 0.38°,and the maximum difference was 1.7% for the multi-wire diameter wire test.