Research On Characteristics Of High Frequency Current Sensor For Partial Discharge Detection

Power cable is an important part of China’s electric power industry,which has a decisive impact on the transmission and supply of electric energy.In the long-term operation of the system,the power cable is prone to aging and poor insulation effect due to the influence of the external environment and partial discharge of the cable itself,which leads to the failure of the power system.In order to eliminate potential power safety hazards in advance,improve the protection detection efficiency and reduce the number of power failure,it is very important to timely and accurately detect the partial discharge of cables.High frequency current method is one of the most widely used and promising pd detection methods in the cable industry.High frequency current sensor is the main equipment used in high frequency current method,and its performance directly affects the effect of partial discharge detection.Therefore,in order to accurately and efficiently detect pd,it is of great significance to develop a sensor with high sensitivity and wide working frequency band.With the rapid development of power system and continuous improvement,and adopt the traditional permalloy,amorphous alloy and mn-zn ferrite and sensor because of its low frequency,has been unable to meet the job requirements of the current electric power industry,and ni-zn ferrite magnetic permeability is the main characteristic of this material is high,low coercive force and the working frequency band,This sensor satisfies the high frequency current sensor with high sensitivity and wide band partial discharge detection.At the same time,due to the operation of the power system,there will be relatively weak power-frequency current,and the magnetic core made of nickel-zinc ferrite is not sensitive to the power-frequency current,so it is more suitable for the production of high-frequency current sensor magnetic core material.In order to meet the installation requirements and facilitate the installation test,the inner diameter of the sensor core should be at least 50 mm.Some sensors also need to be installed in the form of open CT.In this paper,after the demonstration and research,select nickel-zinc ferrite to make the sensor core,on this basis,through the neural network to learn the experimental data,so as to form the high frequency current sensor transmission impedance influence factors mathematical model;Through the study of each influencing factor,the influence of each parameter on the transmission impedance is known,and the optimal parameters of the sensor are further determined,which provides the theoretical basis and data support for the next sensor design.According to the "Technical Specification for Electric Power Equipment Charged Detection Instruments part 5: Technical Specification for High-frequency Partial discharge charged Detection Instruments" issued by the State Grid,the experimental tests of highfrequency current sensors were carried out,including ratio test,transmission characteristic test,amplitude-frequency characteristic test and frequency band width test.The test results are compared with the performance parameters of the mainstream sensors manufactured by foreign manufacturers.By comparison,the performance of the high-frequency current sensor developed by the mathematical model conforms to the national standard and has excellent performance.