Research On Detection Technology Of Low Current Earthing Fault And Device Abnormal Operation Mechanism

With the development of economy and technology,the scale of distribution network has been expanding year by year.As the hub of electric energy from substation to power users,the reliability of its power supply directly affects the satisfaction of power users.According to the relevant data records,80% of the known failure types of power outage accidents are caused by small current grounding faults.When a single-phase grounding fault occurs in the distribution network,the fault current is weak,especially when the neutral point is grounded through the arc suppression coil,the amplitude of the fault line current may be less than that of the sound line,and the reliability of the existing fault detection methods is low.The influence of external factors in practical engineering application may lead to the inapplicability of effective detection methods in simulation test in the actual device,resulting in certain abnormal rate.In this paper,an equivalent model of low current grounding fault mode network is established.Through the analysis of the mode network,it can be seen that the transient zero-sequence current waveforms of the fault lines and the sound lines are quite different,and the transient zero-sequence current waveforms between the sound lines are similar.This fault feature can be used as the theoretical basis for the detection of small current grounding faults.In this paper,a fault detection method based on grey synthetical correlation degree is proposed,which takes the neutral arc suppression coil grounding system as the main research object.In this method,the waveforms are decomposed by variational modal decomposition,and the difference of the transient zero-sequence current waveforms between the fault lines and the sound lines is compared by the grey comprehensive correlation degree fault detection method.The fault model of neutral arc-suppression coil grounding system was built on EMTP-ATP platform,and the effectiveness of the proposed method was verified by simulation.The simulation results show that the proposed algorithm is not affected by the fault initial phase Angle,fault point position and fault time,and has strong robustness to noise interference and arc grounding fault.For fault indicator,such as grounding line selection device fault detection equipment move problems in the practical engineering application,in this paper,starting from its composition and working principle,analyzes the static and electrical transient bursts,surge,fog and other interference factors on the influence of the equipment normal operation,the study showed that caused by surge voltage signal mutations can lead to fault line selection device start by mistake;The electric fast transient pulse group can reduce the amplitude of the telesignal level,which leads to the fault indicator locking failure and false start.Weather conditions such as rain and fog will affect the distribution of electric field,resulting in abnormal(increased)measurement current of fault indicator,and the device will be misstarted.The research results have certain reference value for the subsequent anti-interference design of fault detection equipment such as fault indicator and line selection device.