Leakage control of urban water supply network and mathematical analysis and location of leakage points based on machine learning

In recent years, the new generation technology in the 21st century represented by mobile Internet, Internet of things and AI is bringing another information revolution that has a deep impact on people's intelligent life [1]. In terms of urban infrastructure, urban operation and maintenance, intelligent transportation and other aspects, information technology is deeply combined with it, showing a new form in a different way. Among them, the construction of smart water platform is also one of the important components of Smart City mountain construction. In recent years, it has also been highly valued by the state, and its development strategy has also been put on the agenda. The government is also actively promoting the development of smart water, increasing R & D investment and accelerating the construction of water informatization through cooperation with enterprises. The “wisdom” of smart water is reflected in three aspects. From the perception level, the system collects information about water through wireless networks, such as online monitoring equipment for pressure, flow and water quality, and senses the real-time operation status of the whole urban water supply and drainage pipe network system; From the presentation layer, friendly visual interface and organic integration of all water supply and drainage facilities in water affairs for dynamic image display to form a dynamic and intelligent “urban water Internet of things” platform, as shown in Figure 1; In terms of big data, the system timely and effectively analyzes and processes a large amount of water affairs information, and models it in combination with the corresponding mathematical model, so as to provide decision-making help for the better allocation of resources in the city, save energy, reduce the output of redundant labor force, increase the use efficiency of human and material resources, and contribute to urban green environmental protection [2]. Alibaba's main project in recent years is the brain of smart city, realizing the intelligent management of the city, increasing the efficiency of various services in the city and better coordinating various work. Smart water is also a part of it. Smart water system is mainly divided into four parts: SCADA system, GIS geographic information system, revenue system, water quality management, water sample detection and other production management systems. SCADA is referred to as data acquisition and monitoring control system for short. The data acquisition system, which is mainly based on computer technology and integrates communication technology and control technology, can control the instructions issued by the monitoring equipment on the production site and monitor the on-site environment. The administrator can customize the alarm rules, realize the different step alarm mechanism and enhance the monitoring efficiency. The concept of SCADA was formed in the 1960s and took shape in the 1970s. After the 1980s, the rapid development of microcomputer technology also promoted the realization of SCADA system. In fact, the real rapid realization of SCADA system was at the end of the 20th century. With the rapid development of Internet, the demand of enterprises for management automation and monitoring automation promoted the rapid development of SCADA system [3].

Figure 1

He R and others make reasonable planning in advance, promote the implementation by sections, formulate the work objectives in the leakage control stage, explore the optimal management measures and gradually implement them in combination with technical means according to the scale of water supply pipe network and water supply facilities, the asset status and leakage of pipe network and ancillary facilities [4]. Literature shows that Britain is one of the countries with early urban modernization. The construction of centralized water supply facilities has a history of 200 years. In the 1980s, the leakage of water supply system was also very serious. Therefore, they strengthened the frequency and density of leak detection, promoted the renewal and transformation of pipe network, and carried out DMA zoning construction. After 20 years of efforts, the leakage rate of centralized water supply network has been reduced from 29.5% to 18.7%. Yiran L and others found that in the early 1980s, in the practice of pipe network management, in order to monitor the pipe network leakage for a long time, find the macro distribution of pipe network leakage, balance the service pressure of pipe network, and then reduce the leakage rate, the British water management organization put forward the concept of district metered areas (DMA) management [5]. Ulusoy A J and others believe that DMA refers to the construction of an independent area in which the inlet and outlet flow can be recorded in a certain area of the water supply and distribution system by closing some valves and installing flow meters at the inlet and outlet of the independent area [6]. Northwest water has established 3000 DMA management areas in its water supply network; London's water supply network is divided into 16 districts. With the help of DMA, British water company has comprehensively evaluated the water leakage of the pipe network by checking the basic data, leakage level test, “zero pressure” test and other steps. When it is determined that there is water leakage in a water supply area, the location of the water leakage point shall be further determined through appropriate technical means. Although there are many methods to determine the water leakage point of the pipe network, including passive leak detection method, listening leak detection method, regional meter installation method, regional leak detection method, leak detection compound method and pressure adjustment method, none of them is omnipotent, but it is more effective to combine multiple methods to give full play to their respective advantages. The establishment of DMA leak detection area can adopt different modes for different pipe network forms, i.e. tree water supply network and ring water supply network. Due to many factors such as urban planning and water supply planning, the construction of DMA needs to be carried out with the practice of pipe network zoning management and with the means of pipe network modeling. There are many factors affecting DMA leakage rate, such as the accuracy of meter reading, pipeline decompression and flushing, water for pipe network maintenance and emergency repair, etc. Therefore, Xu J and others can effectively carry out regional leakage control with the help of DMA, which requires the organic cooperation of all departments of the water supply enterprise. If a DMA area has reached the leakage control target after evaluation, it can start to prepare the leakage control report of the area, analyze the investment benefit ratio of leakage control, analyze the problems found in the leakage control process, put forward improvement methods, and guide the main direction of leakage control in the future [7]. Developed countries attach great importance to the research and development of pipe network leakage detection equipment. The leak detector developed by the United States, Britain, France, Germany and Japan has been continuously updated with the development of science and technology. Digital leak detector, multi probe correlation instrument and regional leak monitor have been launched one after another, which greatly improves the reliability and accuracy of leak detection.

For most water supply enterprises, the level of non profitable water volume (NRW) is a very important performance indicator”. However, due to institutional and political pressure and lack of knowledge to strictly determine the level of NRW, many water supply enterprises tend to underestimate NRW. Senior managers are eager to see the report of low-level NRW. However, these reports are either based on deliberately provided wrong information or lack of accurate information, which can not help water supply enterprises reduce costs or improve benefits. On the contrary, it will cover up the truth of the problem and affect the operation efficiency of water supply enterprises. Only by quantifying NRW and its constituent elements, calculating reasonable performance indicators, and changing the leakage water to monetary value, can water supply enterprises accurately understand the situation of NRW and take necessary measures. The establishment process of water balance table can help the managers of water supply enterprises understand the size, source and cost of NRW. The International Water Association (IWA) has formulated the elements and technical terms of a standard international water balance (as shown in Table 1) [8].

The total amount of water flowing into the water supply network from the water plant (referred to as “system supply water”) minus the total amount of charged legal industrial and residential water (referred to as “charged legal water”), i.e. non revenue water (NRW), see formula (1).

The assumptions of this equation are as follows:

The system water supply has corrected some known errors;

At present, some water departments in China have also begun to try to carry out water balance test, which usually adopts the “table filling” method, that is, fill the corresponding water volume data item by item in the “water balance table”, and calculate the “leakage water volume” and “non revenue water volume” by recursive decline. This case uses wb-easycalcv300 (free software) synchronously recommended by the International Water Association. Z water division was founded in 1953. There are 7 main water supply plants, including 5 surface water plants, which mainly use the water source of South-to-North Water Transfer, the water source of the Yellow River is standby, and 2 groundwater plants use the Yellow River to measure seepage. The daily water supply capacity is 1.77 million m³ / D, the water supply population is 4.5 million, the water supply area is 600 square kilometers, the pipe network above dn75 is 3600 kilometers long, and the registered users are 1.3 million. The statistical cycle of water balance in this case is 181 days in half a year (January 1, 2014 – June 30, 2014). The water balance analysis process is shown in Figure 1 [9].

Step 1: First determine the water supply volume of the water supply system ① The system has 4 water supply systems, 1 pressure make-up water system and 19 pressure make-up wells, all of which have suitable water meters and have been regularly checked;

The city's non-revenue water ratio (production-sales difference rate) is 16%, and the leakage rate is 13.80%. According to the above analysis, first of all, the important factors affecting the non-revenue water ratio (production and sales difference rate) of the water supply system in Z city are 5, 1. Background leakage 2. Various fire hydrants steal water; 3. Light leakage 4. Illegal water use in urban villages; 5. Water loss caused by various measurement errors and data processing errors. Enterprise managers can accurately evaluate the economic benefits of corresponding technical solutions, and decide on investment and management ranking.

In the process of balance analysis, deception in the management stage can be found through reverse guidance. For example, during the calculation period, if it is converted into 36,902 households in Z city for household meter renovation (managed by the household meter renovation department) and 41525 households for new households (managed by the customer service department), the total construction cleaning water volume of the two projects is 7933m' (Operating expenses department management), 0.10m³/household, it can be seen that there is a management loophole in the calculation of construction cleaning water volume. Many components that affect the non-revenue quantity cannot be measured, and different departments of the enterprise need to use certain methods to estimate. Among them, the data reporting department deliberately modified the estimation results based on its own performance interests, resulting in a serious imbalance in the analysis process. Therefore, various statistical methods for estimating water volume must be objective. Perform sample testing or method validation. The water balance table recommended by the International Water Association (IWA) is a horizontal, macro, and system-wide leakage component analysis unit. For water supply enterprises that have achieved classified measurement, they can inherit deeper and different measurement classifications.

Therefore, all kinds of statistical methods for estimating water volume must be objective and verified by sample test or method.

The water balance table recommended by the International Water Association (IWA) is a horizontal, macro and system wide analysis method of water leakage components. For water supply enterprises that have achieved zoning measurement, we can continue to carry out longitudinal water balance analysis for different metering zones. The purpose of constructing the performance evaluation system of water supply industry is to promote the benign objectives of water supply enterprises, such as safe water supply, high-quality service, cost transparency and efficiency improvement, through the vertical comparison of their own business performance and the horizontal comparison of business performance between industries. In view of the relevant performance evaluation indexes of water supply system leakage management, the national industry standard “urban water supply leakage control and evaluation standard” (cjj92-2002) puts forward the basic countermeasures and evaluation standards for strengthening leakage control in China, and determines the benchmark evaluation standards for leakage control, such as “leakage rate” and “unmeasured water rate”. With the improvement of the leakage management level of urban water supply system in the domestic water supply industry, the limitations of indicators such as “leakage rate” and “unmeasured water rate” expressed in percentage in practical application have gradually been exposed, and domestic peers have gradually realized the rationality of the water balance calculation method and water supply service performance indicators recommended by the International Water Association (IWA).

Firstly, HPSO algorithm generates a random particle swarm (random solution). Each particle flies (optimizes) in its multi-dimensional solution space, and the flight speed is dynamically adjusted according to its own and other particle flight conditions and experience. There are N particles in d-dimensional space, and the best position in history is p_best.

The position and velocity vectors of offspring particles are shown in formula (2) (3): (2) x→1(t+1)=p→⋅x→1(t)+(1.0−p→)⋅x→1(t) {\vec x_1}\left( {t + 1} \right) = \vec p \cdot {\vec x_1}\left( t \right) + \left( {1.0 - \vec p} \right) \cdot {\vec x_1}\left( t \right) (3) x→2(t+1)=p→⋅x→2(t)+(1.0−p→)⋅x→2(t) {\vec x_2}\left( {t + 1} \right) = \vec p \cdot {\vec x_2}\left( t \right) + \left( {1.0 - \vec p} \right) \cdot {\vec x_2}\left( t \right) Where x→1(t) {\vec x_1}\left( t \right) and x→2(t) {\vec x_2}\left( t \right) are the position vectors of the two parents of D-Dimension respectively; x→1(t+1) {\vec x_1}\left( {t + 1} \right) and x→2(t+1) {\vec x_2}\left( {t + 1} \right) are two children of d-Dimension respectively, and p→ \vec p is a random number vector uniformly distributed in d-Dimension. Each component of p→ \vec p takes value in [0,1], as shown in formula (4) (5). (4) v→1(t+1)=v→1(t)+v→2(t)|v→1(t)+v→2(t)|⋅|v→1(t)| {\vec v_1}\left( {t + 1} \right) = {{{{\vec v}_1}\left( t \right) + {{\vec v}_2}\left( t \right)} \over {\left| {{{\vec v}_1}\left( t \right) + {{\vec v}_2}\left( t \right)} \right|}} \cdot \left| {{{\vec v}_1}\left( t \right)} \right| (5) v→2(t+1)=v→1(t)+v→2(t)|v→1(t)+v→2(t)|⋅|v→2(t)| {\vec v_2}\left( {t + 1} \right) = {{{{\vec v}_1}\left( t \right) + {{\vec v}_2}\left( t \right)} \over {\left| {{{\vec v}_1}\left( t \right) + {{\vec v}_2}\left( t \right)} \right|}} \cdot \left| {{{\vec v}_2}\left( t \right)} \right| Where v→1(t) {\vec v_1}\left( t \right) and v→2(t) {\vec v_2}\left( t \right) are the position vectors of the two parents of d-Dimension respectively; v→1(t+1) {\vec v_1}\left( {t + 1} \right) and v→2(t+1) {\vec v_2}\left( {t + 1} \right) are velocity vectors of two generations of d-Dimension respectively.

Before data modeling, we must first clarify the purpose of modeling and the effect to be achieved [11]. Data modeling is a series of operation sets that do some customization, logicalization, model matching and other work on the data template. The final result of modeling still serves people. How to enable users to clearly get the knowledge they need from the data model is a necessary function of the model.

There are two points to summarize the modeling requirements of this system:

The leakage control of urban water supply network is a long-term and arduous task. This paper deeply and systematically studies and analyzes the current situation of non profitable water volume (NRW) of water supply network, and puts forward and gradually implements the non profitable water volume control strategy based on the scientific system of International Water Association (IWA). On this basis, actively explore economic and effective management means to make the leakage level of water supply enterprises adapt to and meet relevant national and industrial standards. This paper systematically studies and discusses the key technical problems of non-profit water volume control commonly existing in the water supply industry, introduces advanced non-profit water volume control technologies and methods, and studies the non-profit water volume management system, main countermeasures and technical scheme of water supply network. The leakage control of water supply network is studied and discussed as a complete system engineering from basic water quantity analysis to management means, from target determination to technical measure selection. Taking the water supply network of KT City, LZ city and Z City as the main objects of analysis and research and the application of specific engineering measures, this paper puts forward a set of relatively complete and flexible pipe network leakage control countermeasures, implements the theoretical research into practice, not only expands and enriches the research content, but also verifies the theoretical research to a certain extent, and determines its feasibility.