Research On The Method Of Short-circuit Fault Prediction Of The Ship Transmission System Based On The Markov Chain

Because the ship power system was a very independent system of coupling,the environmental humidity of the environment where the transmission line was in was great,and the environment have salt spray,mold,oil etc,the transmission line was more susceptible to corrosion,the insulation layer was easily deteriorated,the insulation capacity was reduced.And then further deterioration of the insulation layer was produced by partial discharge,flash over,etc.The transmission line will enter the short-circuit fault prone period.A very serious impact and even paralyzed of the ship's power system security and stable operation were caused by short-circuit fault.Early failure was the early embodiment of the deterioration of the transmission line insulation and was the premise of short circuit failure.Therefore,it was necessary to detect the early fault to prevent the short circuit fault.Thus,the measures were toke to prevent the short circuit and to ensure the stability of the ship,a power system and safe operation.However the early fault to the short-circuit fault time was difficult to determine,in order to make better maintenance or replacement time.This paper does the following works:First,according to the process of the insulation deterioration of the ship transmission line,the failure mechanism of the short circuit fault was studied,and the fault characteristics of the early fault were analyzed.The ship power system of the dry fed hybrid transmission network was studied in this paper and the running status of the transmission line was analyzed and compared.Secondly,based on the early fault model of the ship transmission line and the running state signals of the transmission line,the KF was dynamically estimated on the line current signal to obtain the estimated current signal.The difference between the current signal and the current estimation signal was acted the first standard signal of the system state change to compare with the current state threshold to make a preliminary diagnosis.At the same time,the KF rapid dynamic estimation of the voltage signal was obtained by estimating the voltage signal.Then the square wave of the estimated voltage signal was fitted.The ratio of the difference between the absolute value of the fitted square wave and the current residual signal was as a second standard signal to compare with the voltage state threshold to confirm or deny the initial diagnosis.The feasibility of the program was verified by the status of each branch line in the ship transmission line system and the accuracy of the program was verified by comparing with other three other voltage-based early fault schemes.Finally,according to the basic theory of Markov chain and the state change of ship transmission line,the normal state,early fault state and short circuit fault state of the running state were established,and the Markov model of the corresponding ship transmission line was established.Based on the operating data of the power system(or the simulated data samples),the Markov state transition probability matrix of the equivalent operation of the power system was obtained.Based on this and the current state of the system a certain period of time in the transmission line state of the probability of change,the steady state probability and the average time before first failure can be quickly resolved and obtained.And compared with the Monte Carlo simulation method,the comparison results show that the stochastic process of the transmission line state of the ship's power system had the feasibility of Markovian and the use of Markov chain prediction.At the same time the transmission line of the early fault and short-circuit fault prone were predict to determine the time to replace the transmission line.