Research On Assessment Of Weak Links In Medium Voltage Distribution Network And Its Transformation Method

The distribution network is the part directly connected with the power users in the power system.The distribution network directly faces the users and plays a key role in the distribution of electric energy.A good distribution network is the key to ensure the safe and reliable power supply.With the rapid increase of power load,the original distribution network can not meet the demand well,so the transformation and upgrading of distribution network is particularly important.In view of how to upgrade the distribution network scientifically and reasonably,ensure accurate and efficient investment,this paper finds out the weak links of distribution network,and guides the upgrading decision-making direction of distribution network according to the assessment results of weak links of distribution network.Considering the different scene environment of the distribution network and the different influence factors that the upgrading of the distribution network focuses on,this paper divides the distribution network into rural power grid and urban power grid to study respectively,fully considering the characteristies and differences between urban power grid and rural power grid.In view of how to realize the efficient transformation of rural power grid through precise investment,and considering the characteristics of rural power grid network structure,this paper proposes a lean transformation method of rural power grid based on cascade combination scoring.First of all,through the analysis of the current situation of the rural power grid,sort out problems in rural power grid,aiming at the main problems,set up evaluation indicators that reflect these problems,and give the calculation formula to match each evaluation indicator,and also deal with the severity of the corresponding problems of different evaluation indicators in different levels,set up the step evaluation standards of each evaluation indicator,then the evaluation index system which can fully reflect the weak link and the severity of rural power grid is constructed;Then,according to the calculation results of each evaluation index,determine the equipment that needs to be modified,and take these equipment that needs to be modified as the evaluation object,score the evaluation object according to the scoring standard of the evaluation index,determine the weight of each evaluation index by using CRITIC method,calculate the comprehensive score of the evaluation object and complete the cascade combination score of the evaluation object;Finally,the evaluation objects are ranked in descending order according to the size of the comprehensive score.The larger the comprehensive score is,the more serious the existing problems are,and the more urgent the transformation needs are.The equipment In the top ranking of the score is optimized and advanced,so as to realize the lean transformation of the rural power grid.TTWith the exparrsion of urban power grid and the access of various distributed generation,the network structure and operation mode become more and more complex,and the uncertainty factors increase,which increases the operation risk of urban power grid.Considering the characteristics of urban power grid,this paper proposes a decision-making method based on risk assessment for urban power grid lean transformation,and uses risk theory to assess the weak links of urban power grid.First of all,by analyzing the risk of urban power grid,three risk indicators are set up to represent the weak link of urban power grid;Then,the main problems existing in the weak link of urban power grid are sorted out,five potential risk factors that may cause risk are put forward,the risk hierarchy structure of urban power grid is established,the probability and consequences of risk occurrence are calculated by fuzzy comprehensive evaluation method,the risk assessment model of urban power grid is constructed,guide the decision-making direction of urban power grid transformation with the results of risk assessment.Finally,considering the characteristics of complex structure and flexible operation mode of urban power grid,there is an interaction between equipment,so on the basis of solving the risk problem,considering the economy of lean transformation of urban power grid,formulating an economic optimal precise investment scheme to solve the existing risk problems.