Risk assessment and management system of transmission line equipment above 220 kV

In this paper, a transmission line operation and maintenance mode based on equipment risk and state is proposed. According to the importance and health degree, the transmission line is divided into two dimensions, which are divided into four levels. By dividing the transmission line risk, which is the consequence after failure, the importance of the transmission line is divided into critical, important, concerned, and general. At the same time, the information management of the above research is realized. It is conducive to the formulation of different levels of line management and control measures. It is also conducive to the optimization of operation and maintenance resources and can improve the efficiency of operation and maintenance.


Introduction
For a long time, transmission line equipment risk assessment has been carried out by means of manual assessment, which inevitably leads to omissions and a weak sense of responsibility of personnel in the evaluation process.As a result, the evaluation results often deviate from the actual operation.With the smooth development of the construction of a safety production risk management system in Southern Power Grid Company, the requirement of integrated lean management is put forward.It is important to make efficient use of the limited maintenance and technical renovation funds so as to achieve cost reduction and efficiency.In order to further improve the construction quality of the production safety risk system, it is of great significance to carry out in-depth equipment risk assessment and improve the assessment quality in an all-rounded way.The study establishes an intelligent risk assessment system based on the technical guidelines for equipment condition evaluation and risk assessment.It effectively eliminates deficiencies and omissions in the process of manual assessment, greatly reducing personnel labor intensity and improving personnel work efficiency.It aims to achieve fine maintenance and technical reform management process, real-time grasp of equipment operation status and risk assessment level, efficient management of equipment risk, and effective prevention and control of equipment accidents.

Importance of transmission lines
The power supply bureaus of all prefectures and cities should evaluate the importance of transmission lines according to the requirements of power grid risk prevention and control of dispatching departments.
According to the following methods, the importance of the transmission line is evaluated from three aspects: the possible event consequences caused by the transmission line fault, the value of the transmission line, and the power supply to the important users.The evaluation results are divided into four levels: "critical, important, concerned, and general" from high to low, and the highest level of the evaluation results from three aspects is taken as the importance level of the transmission line.
(1) According to the consequences of transmission line failure: According to the rules for the investigation of Power Accidents (events) of China Southern Power Grid Co., Ltd., the severity of power safety accidents (events) that may be caused by transmission line failures are analyzed: 1) If a fault may cause general or more power safety accidents, the importance of the transmission line shall be determined as the key.
2) If a fault may cause a first-level power security event, the importance of the transmission line is determined to be important.
3) If a fault may cause secondary or tertiary power security events, the importance of the transmission line should be paid attention to.
4) The importance of transmission lines other than the above cases is set as general.
(2) According to the value of the equipment: According to the equipment purchase guidance price issued by China Southern Power Grid Company, the importance of transmission lines is set as general.
(3) The influence of basis on the power supply of important users: 1) The importance of Hong Kong-related, Macao-related, and nuclear-related transmission lines is identified as the key.
2) According to the annual important user catalog approved by the relevant government departments: If the transmission line fault directly causes the power supply interruption of the super important users, the importance of the transmission line will be regarded as the key; if the transmission line fault directly causes the power supply interruption of the first important users, the importance of the transmission line will be regarded as important; if the transmission line fault directly causes the power supply interruption of the secondary important users, the importance of the transmission line shall be regarded as general.
The situations that directly cause power interruption for important users include under various operation modes, a single transmission line (including multi-circuit lines installed in the same tower, multi-circuit cables laid in the same channel) failure or tripping, etc.; other situations that directly cause power supply interruptions for important users.

Condition evaluation of transmission line equipment
According to the influence of equipment state on the health status of overhead lines, it can be divided into four grades: 1, 2, 3 and 4, corresponding to different weight coefficients.Weight 1 and weight 2 correspond to general state quantities, while weights 3 and 4 correspond to important state quantities.According to the deterioration degree of the state quantity, it can be divided into four grades from mild to severe, which are Ⅰ, Ⅱ, Ⅲ and Ⅳ respectively.The corresponding basic deduction points are 2, 4, 8 and 10 points.The deduction score of the state quantity should be determined by the deterioration degree and weight of the state quantity, that is, the deduction score of the state quantity should be equal to the real deduction value of the state quantity multiplied by the weight coefficient (see Table 1).Points will not be deducted when the state quantity is normal.The main factors causing the transmission line failure are the defect factors and external environmental factors of the transmission line itself, so the above two factors should also be considered in the state of the transmission line.At present, the state evaluation of transmission lines has been widely carried out.The transmission lines are subdivided into eight parts: towers, ground conductors, foundations, insulators, fittings, cables, ancillary facilities, and special sections.It can be seen that the state evaluation work is more concerned with the defects of the transmission line itself.The problems existing in the transmission line itself can be determined according to the state evaluation of the transmission line.The specific evaluation determines the deterioration degree and the corresponding weight according to the appearance of the defect and finally determines the deduction score.According to the results of the evaluation of the tower, the line is evaluated.The evaluation of overhead lines should consider the deduction of individual state quantity and the total deduction of each part at the same time.The state evaluation standard of each part is shown in Table 2.
When the individual deduction of any state quantity and the total deduction of each part are within the normal state range specified in Table2 at the same time, it shall be regarded as a normal state.When the single deduction of any state quantity or the total deduction of all state quantities in each part reaches the attention state specified in The overall evaluation of overhead lines should synthesize the evaluation results of each part.When each part of the evaluation is normal, the overall evaluation is normal; when any part of the state is attention state, abnormal state or serious state, the overall evaluation should be the most serious state.The overall evaluation is divided into the sum of the total deduction points of each part.

Transmission line risk assessment
According to the risk of transmission lines, the importance of transmission lines can be determined, and the importance of transmission lines can be divided into critical, important, concerned, and general.The health degree of transmission lines can be determined according to the state evaluation of transmission lines.The operation and maintenance personnel should determine the management and control level of the transmission line according to the evaluation results of the health and importance of the transmission line and according to the transmission line risk matrix (Figure 1).The management and control level of the transmission line is divided into "level I, II, III and IV" from high to low.

Introduction of the main functions of the system
The software is a three-tier ASP.Net application: interface layer, business layer, and database layer.The interface layer is responsible for handling the input and output to the user.The business layer is the key and core of the system, and it is also the link between the upper and lower layers.According to different business requests, it invokes the relevant interfaces of each class and establishes the actual database connection through the database layer.It generates SQL statements to retrieve or update the database according to the business requested by users and returns the results to the interface layer.The database layer is responsible for the actual data storage and retrieval.Using the current mainstream software development platform Microsoft.Net technology and commercial database system, MSSQL can achieve all functions.The software adopts the powerful function of Microsoft's IIS/ASP.Net, which maintains consistency with other Microsoft products and has good expansibility and compatibility.At the same time, it also adapts to the development of Microsoft's future operating system and database products.It has good expansibility and backward compatibility and fully protects the investment of user software and hardware.
All the functions of the system adopt the advanced Browser/Server (browser/server) structure, which uses WWW browser technology and adopts the latest .netsoftware architecture.It combines multiple script languages of browsers (VBScript, JavaScript...) and ActiveX technology through the browser to achieve the original need for complex special software to achieve the evaluation function.

Equipment defect information management
The equipment defect management module can view the equipment defect information, including power supply bureau, voltage level, function location, power supply station, traffic light, defect order number, defect level, line, status, state date, defect phenomenon, defect category, discovery department, discovery person, discovery time, reason, result, treatment method and so on.The defect data can be queried and managed according to the power supply bureau, voltage level, defect level and function location.And can be statistical analysis of defects have been eliminated, not eliminated, vacancy rate and other indicators.

Equipment condition evaluation
The equipment condition evaluation refers to the single and comprehensive deduction of the defect appearance of the actual defect according to the evaluation standard of "Southern Power Grid Corporation 35kV~500kV overhead line condition evaluation guidelines (trial)" and "Southern Power Grid Transmission equipment defect grading Standard (Operation fascicle 2020 Edition)".The equipment condition is evaluated according to the rules in Table 1, and the health degree of tower and line is obtained by analysis.And carries on the statistics to each kind of evaluation index, obtains the single item maximum deduction score, the total deduction score and the status grading, finally obtains the overall evaluation grading.The system can query the evaluation results according to the power supply bureau, evaluation level, line name and so on.

Equipment risk assessment
Equipment risk assessment refers to the determination of its grade according to figure 1 by the importance and health of the equipment.First of all, the risk grade of the tower is evaluated according to the importance and health degree of the tower, and then the maximum value is selected as the risk assessment result of the line according to the evaluation result of the tower, which is divided into "grade Ⅰ, grade Ⅱ, grade Ⅲ and grade Ⅳ" from high to low.The system can query the evaluation results according to the power supply bureau, evaluation level, line name and so on.

Conclusion
Through the above research and system development, the equipment condition evaluation is realized according to the defect information, and the equipment risk assessment is realized combined with the degree of importance.At the same time, unified information management is realized for the above research to ensure that the evaluation criteria are scientific and reasonable.The evaluation results are accurate and credible.

Table 1 weight
, deterioration degree and corresponding deduction table of state quantity

Table 2 ,
it shall be regarded as the attention state.When the individual deduction of any state quantity reaches the abnormal state or serious state specified in Table2, it shall be regarded as an abnormal state or a serious state.Table2.Corresponding table of overhead line status and evaluation deduction points