Research On Key Technologies Of Protective Relays In Medium Voltage Power System For Engineering Ships And Power Generation Ships

With the development of ship power systems,the power of equipment is bigger and bigger,and the network structure is more and more complex.The system voltage level is developed from low to medium,forming the medium voltage power system of ships.It is different from traditional low voltage power system in that it has a high demand for safety and a variety of power supply modes.Therefore,it is urgent to build protective relays with complete structure and excellent performance to ensure the safe and stable operation of the system.However,there is a lack of systematic research on protective relays for medium voltage power system of ships,and there is no protection countermeasure against the operating characteristics of medium voltage power systems.In this regard,the thesis mainly focuses on the two typical medium voltage power system of engineering ships and power generation ships,studies the improvement technologies of protective relays,constructs a perfect system protection configuration scheme,and conducts setting calculations on key protections for the main equipment and lines.The operation of medium voltage power system for ships has its own characteristics,which has a significant impact on the operation performance of traditional protective relays.In view of the problem of transformer inrush current,based on the analysis of the pre-magnetizing transformer to suppress the inrush current,the relation of transformer capacity ratio and the main transformer differential protection safe operation measures are proposed.In this regard,verification is performed by simulation.For the problem of fault line selection in medium voltage systems,the characteristics of high-resistance grounding at the neutral point are analyzed,and a fault line selection scheme for short-term switching of high and low resistances is given.In order to solve the problem of frequency switching in medium voltage power system for power generation ships,the influence of different frequencies on the protection performance of the system is studied and the simulation verification is carried out.The medium voltage power system of ships has a complex network structure,various operating modes,and lack of complete protective relays.Taking the more complex medium voltage power system of engineering ships as the research object,firstly,the structure characteristics of the multiloop network and its typical operation modes are analyzed.In addition,in order to study the operating and fault characteristics of the system in different ways,more complete system transient simulation models are established by using the PSCAD platform.On this basis,according to the safety specification of the medium voltage power system of ships,the protection demand and configuration principle of the main equipment of the system are clarified,and a set of perfect protection configuration scheme based on differential protection is put forward.The protective relays of medium voltage power system for ships are lack of the setting calculation criteria,its setting is mainly based on human experience,and the protection performance is poor.In this regard,based on the constructed transient simulation models,different types of faults under different operation modes are calculated.On this basis,according to the system protection configuration scheme,a complete setting calculation of the typical equipments and lines such as generators,transformers,feeders,incoming lines and buses are carried out,and protection settings lists are formulated.