Research On Spare Transformer Planning At 110kV Distribution Substations Considering Mobile Substation

With the rapid development of economy and the improvement of people's living standard,customers' demand for reliability performance of power supply is increasing step by step.Main transformers at 110 kV substation distribute electricity to the load points,and their failures cause the outage of distribution system load points and huge ecomonic outage losses.Scientific and reasonable transformer spare planning is becoming an important measure to improve the reliability performance of power supply.As an emergency spare equipment,Mobile substation(MS)can be used to shorten the outage time caused by transformer failues and improve the reliability performance and economic efficiency of power supply,especially for the cases of shortage of land resources and difficulty of substation expansion.This thesis concentrates on the spare tranformer planning at 110 kV substations considering the use of transportable substations.The main contributions of this thesis are as follow:To fully take the influence of different failure class and different spare mode on the reliability of transformer groups into consideration,built spare transformer group Markov reliability model considering class 1 failure and class 2 failure,based on that,transformer group spare planning model considering random failure is built with the objective of minimizing the system total cost.Considering two different spare mode: mobile substation and regular transformer,built spare transformer group Markov reliability model direct at transformer's class 1 failure and class 2 failure,using state space method to calculate the reliability index of transformer group.Further,construct transformer group spare planning model with the objective of minimizing the sum of system outage loss,spare investigate cost and spare maintenance cost,comparing the cost of different planning schedule to choose the optimal spare schedule.Take a transformer group including 60 transformers as exemplify to analyze,giving the optimal spare schedule configuring with 4 regular transformers and a mobile substation under class 2 failure.The existing transformer group spare planning literature hardly considering the impact of planned maintenance on spare configuration,build spare transformer group reliability model including planned maintenance and two failure class,based on that,transformer group spare planning model considering random failure and planned maintenance is built with the objective of minimizing the system total cost.This work constructs transformer group reliability model including planned maintenance,class 1 failure and class 2 failure,and proposes sequential monte-carlo method of transformer group's reliability assessment.Base on that,built transformer group spare planning model on the objective of minimizing the system total cost including outrage loss.Comparing the optimal spare schedule of two different regions via exemplify,analyze the impact of substation load rate,failure time and unit outrage loss on the optimal schedule.Take two system including 40 substations as exemplify to analyze,giving the optimal spare schedule configuring with 4 regular transformers and 2 mobile substations when overall considering planned maintenance and forced outrage.Store locations of transportable substations have significant effects on the economy and reliability performance of distribution systems.There has been relatively little research on optimal store location of transportable substations.A reliability assessment model for transformer group is built considering the geography distribution and actual trafic conditions of 110 kV substations in urban areas.Considering outage cost of load points and failue rate of transformers,optimal location planning model for transportable substations is bulit with the objective of minimizing the system total cost,which can be used to decide the optimal number of transportable substation and optimal store locations.Case studies show that outage losses of load points and load density have significant effects on the the optimal store locations of transportable substations,and the proposed technique can be used to significantly improve the system reliability performance and total costs.