10kV Distribution Network Single Phase Short-circuit Current Calculation And Step Voltage Finite Element Analysis

Neutral grounding without impedance, neutral grounding through suppression coil and neutral grounding through low resistor are the most common neutral grounding in the lOkV distribution network. There are different characteristics and application advantages with different neutral grounding. When the single phase short-circuit fault occur in the lOkV distribution network, zero sequence voltage, short-circuit current are calculated in detail and transient characteristics are analyzed for the three main neutral grounding in this paper. Then, Electric field distribution and step voltage are also calculated with Finite element analysis software for grounding through low resistor. The study of this paper is helpful to the choice of neutral grounding and power system relay protection for the lOkV distribution network.The study of this paper focuses on the following aspects:The development and application trends of neutral grounding in lOkV distribute network are introduced in this thesis, then the structure and work principle of grounding transformer is analyzed in detail. The advantages and disadvantages of three main neutral grounding are summarized and compared with each other.For the three main neutral grounding distribute network, Firstly, the steady-state equivalent circuit is proposed through careful analysis when the single phase short-circuit fault occur and the short circuit current formula is derived in detail on the basis of the steady-state equivalent circuit. The distribution figure of capacitive current is given. Secondly, the transient-state equivalent circuit is presented through careful analysis and the transient short-circuit current is solved based on the transient-state equivalent circuit. Finally, a single phase short-circuit fault model is established in the MATLAB software, the simulation results and data are consistent with the theoretical analysis results.The concept of grounding resistance, step voltage and touch voltage are expounded, and the theoretical formula is also deduced. The step voltage when the single phase short-circuit fault occur is calculated quantitatively with the finite element analysis software ANSYS. The simulation results are consistent with the theoretical calculation results.Two common short-circuit experimental program are designed and the experimental procedures and some notes are given in detail. It is demonstrated that the theoretical analysis about the short-circuit current and the step voltage in the paper is correct.