| The insulator of ship power distribution system cable is easy to be damaged and eroded by electric effect,thermal effect,chemical effect,mechanical effect and biological effect,which results in the decrease of its insulation performance,causing ship power distribution system single phase or multiphase grounding fault and phase fault even the insulation electrical fire and other accidents,which seriously threatens the safety and vitality of ships.Especially for the new style all-electric ship,the damage caused by the decrease of cable insulation performance will be more serious.There are some defects such as low detection accuracy,poor in time effectiveness,compulsive power failure detection difficult to satisfy the intelligent development of the ship power distribution system for the conventional method applying handheld megohm meter instruments to proceed the insulation detection of ship power distribution cables.The existing AC/DC superposition method and partial discharge method and other online insulation monitoring technology are with some disadvantages such as difficulty in signal extraction.low detection accuracy and high cost etc.This paper will combine the characteristics of the ship AC power distribution system in China,study the theorical method of on-line monitoring of cable insulation under different distribution wires as AC single phase,three-phase floating ground,effective ground etc and the engineering realization technology of the theoretical method of on-line monitoring of cable insulation under AC single-phase distribution wire system,this technology is integrated with ship PMS technology to effectively control the occurrence of insulating electrical fire accidents while realizing the Omni-directional monitoring of electrical parameter of ship distribution system.The main research work and contents are as follows:This paper studies the characteristics of the existing ship distribution system in China and the necessity of On-line monitoring technology of ship distribution cable insulation.and summarizes the research status and development trend of the existing ship distribution cable insulation on-line monitoring technology.The overall scheme of on-line monitoring technology for ship distribution cable insulation is studied.The topology of the intelligent ship distribution cable on-line insulation monitoring system under the new ship power system is designed,and the functions and characteristics of each layer in the system are analyzed.The related theories and methods of on-line monitoring technology of ship distribution cable insulation are studied.Based on the analysis of the characteristics and actual situation of AC single-phase,three-phase floating ground and effective grounding three-phase ship power distribution system,The resistive residual current separation method,zero sequence current voltage method and residual current decomposition method are proposed to realize the on-line monitoring of cable insulation of the above three distribution systems.Among them:The resistive residual current separation method mainly makes use of the characteristic that the resistive residual current is in the same phase as the system voltage,so as to realize the effective separation of the resistive components of the lumped residual current and finally obtain the cable insulation resistance.Complete the on-line monitoring of cable insulation performance;The zero-sequence current-voltage rule mainly makes use of the zero-sequence current of the fault loop to lag a certain angle of the zero-sequence voltage when there is a single-phase or multi-phase short circuit to the ground in the three-phase floating ground system,the zero sequence current of the non-fault loop will be ahead of the zero sequence voltage by a certain angle,so as to realize the accurate determination of the fault loop;The residual current decomposition method mainly makes use of the characteristics that each phase resistive residual current and each phase voltage in the three-phase four-wire system are in the same phase.when a single-phase or multi-phase short circuit to the ground occurs,the one-phase voltage phase is used as the reference phase.The phase vector diagram between the lumped residual current and the voltage of each phase is obtained.the lumped residual current is restored to each phase by vector triangle,and the resistive leakage current of each phase is obtained,and the insulation on-line monitoring of the effective grounding three-phase system is realized.Finally,the simulation and experimental verification of the above three monitoring methods are carried out by building a model in the simulink module of MATLAB.Combined the thoughts of engineering and practical application,the technical realization of on-line insulation monitoring system for intellectualized ship power distribution cables is studied in this paper,the hardware of single-phase insulated on-line fire control device is designed and the corresponding software is written,by using the existing networking technology and the Internet of things technology,the various measurement information of the single-phase insulated online electrical fire prevention control device is uploaded to the electrical fire monitoring equipment,the local monitoring background and the cloud platform in real time,so as to realize the cross-platform monitoring of the data of the ship power distribution system.The laboratory test results show that:the single-phase insulated electrical fire prevention and control device designed in this paper can accurately and reliably measure the insulation resistance of cables and other electrical energy parameters of single-phase power distribution system.The measurement error of insulation resistance is no more than 5%,and the measurement error of other electrical energy parameters is no more than 0.5%,the electromagnetic compatibility can be achieved to grade ?.The electrical fire monitoring equipment designed in this paper has verified by the type test of the national fire electronic product quality supervision and inspection center. |
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