Research And Design Of New Small Resistance Grounding System In 220kV Substation

Substations are important nodes in the entire transmission and distribution sector.Substation neutral grounding design directly affects the stability of substation operation.As the size of cities continues to expand,the load capacity of substations is constantly changing.In order to ensure the reliable operation of substations,substation neutral grounding methods also need constant changes.At present,the electrical system design proposes a grounding method based on small electricity.It can reduce the frequency of neutral faults due to gap grounding.Therefore,it can effectively improve the stability and safety of distribution lines,and create more social and economic benefits.This article mainly discusses the design of a new small-resistance grounding system for 220 kV substations.This design scheme can provide reference for small resistance grounding design of other 220 k substations.The paper first discussed the related factors that affect the grounding method.Analyzed the system insulation level,the reliability of the relay protection device,the reliability of the power supply,the system operating environment and the future development direction of the power grid.Based on this,several neutral grounding methods are compared and analyzed.Several methods for neutral grounding,neutral grounding,neutral arc suppression coil grounding and neutral resistance grounding are discussed.Applicable scene.It then discusses the basic situation of the 220 kV substation in the town of Gezhengbao.It analyzes the general situation of the power system of the substation to be built,the basic status of the electrical wiring and the current status of the operation protection setting plan.The thesis focuses on the analysis of the choice of the neutral point grounding method and the design of the scheme in the Cizhenpu substation.According to the specific conditions of the substation and its future development direction,the transformation of the town to the maximum capacity of the arc suppression coil has been achieved in the town of Gezheng.Therefore,the neutral point grounding mode of this substation is changed to grounding via a small resistance method.After a comparative analysis of the final use of arc suppression coil and small resistance grounding.The scheme architecture design of the arc suppression coil and small resistance grounding method was discussed.On the basis of determining the final scheme,the parameter calculation and equipment selection of 220 kV substation low resistance grounding system are analyzed.The paper focuses on the design of the neutral point grounding line selection system.Based on the overall design of the neutral grounding line selection system,the overall structure of the neutral point grounding line selection system and the basic structure of the signal processing unit are discussed.The circuit design of multi-channel voltage and current sampling is analyzed.The circuit design of the ADC conversion unit is mainly studied,and the characteristics of different ADC conversion schemes are compared and analyzed.It is finally determined that the special ADC sampling scheme based on ADS8364 can be obtained.The controller selection and circuit design are analyzed,and the STM32F103 microcontroller is selected as the controller of the line selection unit.The communication circuit design is analyzed,and the RS-485 communication interface and Ethernet communication interface are provided to meet the requirements of different substations.The AC power supply circuit design and time synchronization unit design are analyzed.The dedicated dual-mode time-synchronization module supporting Beidou and GPS is selected to provide synchronization time for the system.Finally,through the unit test and functional test of the system,it is determined that the line selection system designed by this subject can meet the requirements of use in terms of accuracy and sensitivity.