Abstract
The Floating nuclear power plant grid is composed of power generation, in-station power supply and external power delivery. To ensure the safety of the nuclear island, the in-station system adopts a special power supply mode, while the external power supply needs to be adapted to different types of external systems. Because of frequent single phase-ground faults and various fault forms, the fault line selection protection should be accurate, sensitive and adaptive. This paper presents a fault line selection method in cooperation with multi-mode grounding control. Based on the maximum united energy entropy ratio (MUEER), the optimal wavelet basis function and decomposition scale are adaptively chosen, while the fault line is selected by wavelet transform modulus maxima (WTMM). For high-impedance faults (HIFs), to enlarge the fault feature, the system grounding mode can be switched by the multi-mode grounding control. Based on the characteristic of HIFs, the fault line can be selected by comparing phase differences of zero-sequence current mutation and fault phase voltage mutation before and after the fault. Simulation results using MATLAB/Simulink show the effectiveness of the proposed method in solving the protection problems.
Highlights
The floating nuclear power plant is a moving nuclear power station, and is the combination of marine and nuclear engineering [1]
3.3 Fault line selection method based on wavelet transform modulus maxima (WTMM) The wavelet transform coefficient represents the frequency component of the fault signal at a certain decomposition scale
It can accurately distinguish between bus and feeder faults, has a higher resistant ability to high transition ground fault impedance, and improves the sensitivity of line selection protection in the case of high-impedance faults (HIFs) in floating nuclear power plant power systems
Summary
The floating nuclear power plant is a moving nuclear power station, and is the combination of marine and nuclear engineering [1] It can provide safe and effective energy supply for remote islands, offshore oil exploitation, and seawater desalination etc. The floating nuclear power plant system adopts the ineffectively grounding mode, the magnitude of the steady-state fault current is low [16], but there is plenty of fault information in the transient signals when ground faults occur. When HIFs occur, the fault characteristics of the feeders are not obvious because of the signal noise and the limited precision of zero-sequence CT Under such conditions, multi-mode grounding control is adopted and the system is switched into low-resistance grounding mode to enlarge the fault characteristic. The performance of the proposed scheme is verified by simulation
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