Method for fluid measurement for a discrete area of a fluid supply network

A method for fluid flow measurement for a discrete area of a fluid supply network, where the fluid supply network includes a network of pipes that includes a main pipe for transporting fluid from a source into the fluid supply network for delivery to consumers, wherein the main pipe crosses a boundary between the discrete area and a further area of the fluid supply network, which is outside of the discrete area, and a plurality of distribution pipes each transport fluid from the main pipe to a consumer, where fluid pressure and the fluid consumption on at least two selected key metering points located inside and outside of the discrete area are measured, and where the fluid pressure and the fluid consumption measured on these selected key metering points the fluid flow in the main pipe that crosses the boundary of the discrete area is calculated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/RU2016/000370 filed Jun. 20, 2016.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for fluid flow measurement for discrete areas inside a fluid supply network.

2. Description of the Related Art

Pipeline networks are the most economic and safest mode of transportation for fluids like water, oil, gases and other fluid products. As a way to provide long-distance transport, pipelines have to fulfill high demands of safety, reliability and efficiency. If properly maintained, pipelines can last indefinitely without leaks. The leaks in the pipeline network can be caused by various reasons, e.g., damage from nearby excavation equipment, corrosion of pipes, accidents or earth movement.

Such a system of interconnected pipes that carries a pressurized fluid, such as water, oil, gases and other fluid products, is called hydraulic supply network. When monitoring hydraulic supply networks, one often faces the task of leakage detection and leakage localization. If there is a problem in the network, then it is very important to troubleshoot the defect in short time. Timely localization of the problem allows a reduced cost of repair and possible liquid losses on the network. Consequences of the leakage can be very destructive.

Any fluid supply network, including a water supply system, typically includes fluid sources or fluid storage facilities such as reservoirs, tanks, pressurizing components, such as pumping stations or pumps, etc., and a pipe network for distribution of fluid to the consumers.

Further the fluid supply network is considered on an example of a water supply network.

A water supply system or water supply network also belongs to the hydraulic supply networks that provide water supply to different types of consumers.

The water in the supply network is maintained at a positive pressure to ensure that water reaches all parts of the network, that a sufficient flow is available at every take-off point, i.e. at every consumer, and to ensure that untreated water in the ground cannot enter the network. The water is typically pressurized by the pressurizing components.

Different types of pipes are used in the pipe network of the water supply network. In general, the pipes can be classified in two categories depending on purpose (i) main pipes or transportation pipes, which are mainly long pipes located underground with large diameters of, for example, 300-700 mm, but can be of giant diameters of more than 3 m, moving pressurized water from the water storage facilities into the town or district of the town, and (ii) distribution pipes, which are pipes with small diameters of, for example, 80-300 mm, used to take the water from the main pipes to the consumers, which may be private houses as whole or each apartment individually, or industrial, commercial or institution establishments, and other usage points such as fire hydrants.

The topology of the water supply network is well known by the utilities companies who service the network. This means that further characteristics of the water supply network are well known, e.g., structure and arrangements of pipes, diameters of pipes, pipes lengths, or location of sensors of different types.

By now, water has become one of the most important goods in the 21st century. However, sometimes considerable water losses occur in water supply networks.

The term “water loss” is generally adopted to indicate the difference between the overall amount of water supplied into the network and the sum of the water volumes corresponding to the consumers' consumption recorded by flow meters installed on consumers' nodes.

These water losses can be divided into two groups (i) the apparent losses, e.g., unrecorded water volumes used for public functions, such as cleaning of roads and urban areas, irrigation of green spaces, operation of public fountains, fire-extinguishing service, which consist of water volumes actually consumed but not accounted for, and (ii) the real losses, which are caused by damages that may have occurred to the network pipes or by the deterioration of the pipe junctions or the hydraulic devices. Real losses are the physical losses of water from the water supply system, also referred as “water leakages”.

These losses put a strain on water supply and inflate the management cost for the water utilities because they represent water that is extracted and treated but never reaches the consumers.

In many cases, minor water leakages deriving from the inefficient hydraulic seal of junctions or from small cracks on pipes may lie hidden for a long time, sometimes for months or even years. Major leakages can be easily observed when significant damages to the pipes occur, because they usually result in large amounts of water erupting from ground or flowing in the consumer properties.

The proven method around the world to reduce leakage from the water supply system is to proactively find the leaks before they appear at the surface. This can be achieved by monitoring the network and has the benefits of reducing the time the leaks are running, and wasting water.

According to international and national standards, the best practice method for monitoring a water supply network is to sectorize it into district metered areas (DMA). A DMA is an area with strict boundaries within the water supply network with measured inflow into this discrete area. This technique was first introduced at the beginning of the 90s.

A DMA represents an area of a water supply network in which the quantities of water entering and leaving the district are metered.

In a traditional way, when subdividing the water supply network into areas and DMAs, respectively, an attempt was always conventionally made to form the areas such that only one inflow or inflow main pipe resulted that can be monitored using a single flow meter.

FIG. 1illustrates a prior art water supply network1with a water source (not shown inFIG. 1), pumping station3, main pipes4and distribution pipes5. The water supply network1comprises a District Metered Area2. Valves6and flow meters7are located at boundaries8between the DMA2and further areas9of the supply network1. Main pipes4crosses the boundary8to provide water for consumers10in the DMA2. Distribution pipes5are used to connect the consumers10with the main pipes4in the DMA2. All main pipes4of the DMA2are equipped with flow meters7for measuring all inflow and outflow of the DMA2and/or valves6that allows shut off of the flow inside the main pipe4. Therefore, as soon as flow meters7and valves6are installed into all main pipes4that cross the DMA2boundary8, all inflow and/or outflow of water into and out of DMA2can be measured. This information might be further used for leakage detection, water balance calculation in the DMA2, etc.

The prior art DMA's approach, however, has its disadvantages. Firstly, dividing the water supply network into smaller areas comes with a cost—the cost of an area survey, installation design, flow meter and chamber installation etc., is substantial, particularly if small areas (e.g., less than 1000 consumers) are chosen. The main pipe diameters are big (typically more than 300 mm). Consequently, flow meters and valves to be installed on this main pipes are big and therefore also expensive.

Moreover, creating DMAs by traditional ways requires the ‘permanent’ closure of many boundary valves—and, because of area supply arrangements and network characteristics (such as topography and low system pressures) some networks are hydraulically difficult to divide into single-feed DMAs without disadvantaging consumers.

The key to DMA management is the correct measurement and analysis of the flow in and out of the DMA and the flow consumed by the end-users, i.e., consumers. The water consumed by the consumers inside the DMA can be easily calculated, because in most cases consumers have water gauges installed. However the measurement of inflow into the DMA and outflow from the DMA is not an easy task.

In general, the existing ways of measuring fluid flow into and out of a discrete area, e.g., a district metered area, of a supply network require very sophisticated and expensive flow meters, the installation of which is complex, costly and time consuming.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the invention to provide a method for easily and conveniently achieving fluid flow measurement in a discrete area, especially for the district metered areas, of the fluid supply network.

This and other objects and advantages are achieved in accordance with the invention by a system for fluid flow measurement for a discrete area of the fluid supply network and a method for fluid flow measurement for a discrete area of a fluid supply network, where the fluid supply network comprises a network of pipes for delivering a fluid to consumers. The network of pipes comprises at least one main pipe to transport fluid from a source into the fluid supply network, wherein the main pipe crosses a boundary between the discrete area and a further area of the fluid supply network, that is outside of the discrete area, and a plurality of distribution pipes, wherein each distribution pipe is adapted to transport fluid from the main pipe to a consumer fluidly connected to the distribution pipe.

The junctions of at least two pipes, main and/or distribution pipes, establish nodes. Thus, two nodes that are located on the same pipe, preferably on the main pipe, from the different sides of the discrete area boundary are boundary nodes. There are no other nodes between the boundary nodes.

The distribution pipes are equipped with a plurality of key metering points. Each key metering point is fitted with a pressure sensor and a consumption gauge. Therein, each pressure sensor is adapted to perform a measurement of fluid pressure P1, P2in the distribution pipe (5,13) where the pressure sensor is installed. In addition, each consumption gauge is configured to measure fluid consumption q1, q2by consumers that are fluidly connected by the distribution pipe.

In accordance with the method, during the steps a) and b) the fluid pressure P1, P2and the fluid consumption q1, q2on at least two selected key metering points that are located inside and outside of the discrete area are measured, where the fluid pressure P1, P2and the fluid consumption q1, q2measured on these selected key metering points the fluid flow Qiin the main pipe that crosses the boundary of the discrete area is calculated during the step c of the method.

The same method should be applied to calculate the fluid flow Qifor every further pipe that crosses the boundary of the discrete area. Afterwards, by summing up the fluid flows Qiof the individual main pipes the total fluid flow into/out of the discrete area can be calculated.

It is also an object of the present invention to provide a system for fluid flow measurement for a discrete area of a fluid supply network. In accordance with the present invention, the system comprises a plurality of key metering points where each key metering point is configured to be located on a distribution pipe and is equipped with a pressure sensor and a consumption gauge. Furthermore, at least one key metering point is located within the discrete area and at least one key metering point is located in the further area that is outside of the discrete area. The key metering points provides fluid pressure P1, P2in the distribution pipes measured by the pressure sensors installed on these distribution pipes, and fluid consumption q1, q2by consumers that are fluidly connected by the distribution pipe measured by consumption gauge.

Moreover, the system comprises a control unit that is configured to calculate the fluid flow Qiusing the measured fluid pressure P1, P2and the measured fluid consumption q1, q2on the key metering points (14,15) in accordance with the method of the invention.

Therefore, there is a fluid supply network with the system for fluid flow measurement for a discrete area of a fluid supply network.

The present invention is based on the insight that the inflow and outflow of the discrete area can be measured using pressure sensors and consumption gauges installed on distribution pipes that fluidly connect consumers to the main pipes instead of the traditional prior art approach based on measuring inflow and outflow by flow meters installed directly in the main pipes.

As mentioned above, the distribution pipes are pipes with small diameter (e.g., less than 300 mm) to carry the pressurized fluid from the main pipe to the consumers. The pressure sensors that are installed on the distribution pipes are relatively cheap in comparison with the flow meters. In addition, the installation process of the pressure sensors is not connected with the interruption of fluid supply to the consumers of the entire discrete area.

The consumers that are supplied through the distribution pipes might be a private house, as a whole one or each apartment, or industrial, commercial or institution establishments, and other usage points such as fire hydrants. The distribution pipes can provide the fluid to one consumer or to a conglomerate of consumers.

In most cases, it is assumed that the fluid consumption by the consumers on every distribution pipe is known due to the fact that there is a legal requirement to install consumption gauges, in other words individual flow meters, to measure individual consumption and to pay for the consumed liquid, in case of water supply network, to pay for the consumed water. The service companies trace that the consumption gauges installed on the consumers' nodes are replaced regularly in order for the consumption measurements to be reliable and accurate. Therefore, the consumption by the consumers is well known.

Consequently, as soon as the fluid pressure on the two distribution pipes that are located from both sides of discrete area boundary is measured by pressure sensors and the fluid consumptions by consumers on both distribution pipes are known, the fluid flow in the main pipe that crosses the discrete area boundary can be calculated.

This approach can be easily extended for more than two distribution pipes.

Thus, the present invention is proposed to provide a new method and a system for fluid flow measurement for the discrete area of the fluid supply network.

In a possible embodiment of the method at the step c the fluid flow Qiis calculated based on the following relationship:

Qiy=Δ⁢⁢PPR=(P1+q1γ⁢R1)-P2+q2γ⁢R2R,whereEq.⁢1
Qiis a fluid flow on the main pipe that crosses the boundary of the discrete area, i.e. between the two boundary nodes, ΔPPis a pressure drop between the boundary nodes, R is an equivalent hydraulic resistance of the main pipe that crosses the boundary of the discrete area, R1, R2are an equivalent hydraulic resistances of the distribution pipes on which the selected key metering points are installed, P1, P2are the fluid pressure in the distribution pipes measured by the pressure sensors that are installed on the selected key metering point, q1, q2are the fluid consumptions on the selected key metering points measured by the consumption gauges, and γ is a flow exponential parameter, where the γ depends on the mode of fluid current, such as laminar, or turbulent, inside the pipe and used hydraulic approach. For example, in the Darcy-Weisbach equation γ=2. The Darcy-Weisbach equation is used for the water supply networks and turbulent mode of fluid current.

The equivalent hydraulic resistance R, R1, R2, of a pipe, the main pipe or distribution pipe, can be calculated by using the characteristics of the pipe, such as length of the pipe between nodes, pipe roughness, or inside pipe diameter, which are known to experts.

The above Eq. 1 of the fluid flow Qiallows the calculation of the fluid flow Qiin the main pipe through the boundary of the discrete area without having a costly flow meter installed on the main pipe.

In another possible embodiment of the method, criteria to select appropriate key metering points for the measurements at the steps a) and b) to be taken are defined.

At step a) the fluid pressure Piand the fluid consumption qishould be measured on the at least one selected first key metering point that is located inside of the discrete area. Moreover, this selected first key metering point is located on distribution pipes that are fluidly connected to the boundary node that is inside of the discrete area.

At the step b), the fluid pressure Piand the fluid consumption qishould be measured on the at least one selected second key metering point that is located outside of the discrete area, i.e., inside the further area. Moreover, this selected key metering point is located on distribution pipes that are fluidly connected to the boundary node that is outside of the discrete area.

Furthermore, for the measurement at the steps a and b, all and only such key metering points should be selected and used for further measurement, which are located on their distribution pipe such that no further first key metering point is located between the respective selected key metering point and the respective boundary node inside or outside the discrete area.

The above criteria of selection of the key metering points for the further measurement makes the calculation of the fluid flow in and/or out of the discrete area more accurate and precise.

The fluid flow Qithrough the main pipe that crosses the boundary into or out of the discrete area can be calculated by using the Kirchhoff's system of equations, that are well known, applied to the water supply network.

The system of equations should include equations for every selected key metering point to calculate the fluid pressure in the node of accession of a distribution pipe where the respective selected key metering point is installed on:
Pnode i=Pi+qiγ*R1Eq. 2
where Pnode iis a fluid pressure in the i-node of accession of a distribution pipe where the respective selected key metering point is installed on, Piis the fluid pressure in the distribution pipe measured by the pressure sensor that is installed at the selected key metering point, Riis an equivalent hydraulic resistances of the distribution pipe on which the selected key metering points is installed, qiis the fluid consumptions at the selected key metering points measured by the consumption gauges, and γ is a flow exponential parameter, as described above.

Also for every two nodes i and j that are next to each other inside, the area limited by the selected key metering points the fluid transport equations should be created:

Qi-jγ=Pi-PjRi-jEq.⁢3
where
Qi-jis the fluid flow through the pipe between two nodes i and j, Pi, Pjis the fluid pressure in the respective nodes i and j, and Ri-jis an equivalent hydraulic resistance of the pipe between the respective nodes i and j.

Moreover, for every node on the main pipe that is located between the boundary of the discrete area and the respective key metering point, the equation in accordance with the Kirchhoff's junction rule should be created. The Kirchhoff's junction rule means that the algebraic sum of fluid flows meeting at a node is zero.

Such system of equations can be solved because the number of the unknown parameters equals the number of equations created. Therefore, the fluid flow Qithrough the main pipe that crosses the boundary into or out of the discrete area can be derived from this system.

In a possible embodiment of the method, the selected key metering point equipped with the pressure sensor and the consumption gauge can have the pressure sensor and the consumption gauge located in different places on the distribution pipe, such that the consumption gauge is located downstream the pressure sensor. This feature allows more flexibility in equipment installation in the fluid supply network.

In a possible embodiment, the method can be applied for the case when the selected key metering point is equipped with the plurality of the consumption gauges that are located downstream of the pressure sensor. In accordance with this embodiment, at the steps a) and b) of the method, the fluid consumption on the respective key metering point taken for further calculations of the fluid flow is calculated as a total fluid consumption measured via the plurality of consumption gauges.

This feature allows the use of an already existing system of consumption gauges without additional installations and optimizing the number of the pressure sensors to be installed.

In a possible embodiment, the method for fluid flow measurement for a discrete area of a fluid supply network is applied to a water supply network, where the discrete area is a district metered area DMA.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Various embodiments are described with reference to the drawings, where like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

The invention relates to a system36for fluid flow measurement for a discrete area2of a fluid supply network1.

FIG. 2shows a block diagram of a part of the fluid supply network1with the discrete area2isolated in accordance with the present invention and illustrates the insight of what the invention is based on. The main pipe4of the fluid supply network1crosses the boundary8of the discrete area2of the fluid supply network1, where the boundary8separates the discrete area2and a further area9of the fluid supply network1. Distribution pipes13of the fluid supply network1fluidly connect the main pipe4with consumers18.

In contrast to the prior art system shown inFIG. 1, there are no flow meters installed on the main pipe4. Therefore there is no possibility to measure the flow through the main pipe4into or out of the discrete area2by traditional measures.

However there are junctions of at least two pipes, main pipe4and/or distribution pipes13, which establish nodes11,12,26,30. Here, two such nodes11,12that are located on the same main pipe4on different sides of the boundary8without any further nodes located between them are boundary nodes11,12.

These two boundary nodes11,12are pipe junctions, in this particular case, the junctions of the main pipe4with the distribution pipes5,13. These two boundary nodes11,12are located on the same main pipe4, but from different sides of the boundary10of the discrete area2: the boundary node12is located inside the discrete area2and the boundary node11is located outside of the discrete area2, i.e., inside the further area9.

Key metering points14,15are installed between the boundary nodes11,12and the consumers18on each of these distribution pipes5,13. Each of key metering points14,15is equipped with a pressure sensor16and a consumption gauge17, where each pressure sensor16is adapted to make a measurement of fluid pressure Piin the distribution pipe5,13where the pressure sensor16is installed, and each consumption gauge17is configured to measure fluid flow qithrough the distribution pipe5,13where the consumption gauge17is installed, therewith measuring fluid consumption by consumer18that is fluidly connected to the main pipe4by the concerned distribution pipe5,13.

FIG. 3shows a flow diagram of an embodiment of a method for fluid flow measurement for a discrete area2of the fluid supply network1according to the present invention.

At step19the measurement of the fluid pressure Pi and the fluid consumption qi on at least one selected first key metering point14that is located inside the discrete area2is performed.

At step20the measurement of the fluid pressure P2and the fluid consumption q2on at least one selected second key metering point15that is located outside the discrete area2, i.e., in the further area9, is performed.

At steps19and20the measurement of the fluid consumptions q1, q2on each key metering point14,15that are fluid flow q through the distribution pipes5,13measured by the consumption gauge17are performed within a given time frame. The time frame can be 15 minutes, or 1 hour. The fluid pressure P1, P2is the average of the fluid pressure within the time frame when the fluid consumption q1, q2is measured. The less the time frame of measuring the fluid consumption, the more accurate the fluid flow Qi is calculated.

In the ideal case, measurements at steps19and20on different key metering points14,15must be performed at the same time. However, performing such measurements on different key metering points14,15with a time difference is possible. The time difference should be less that the time frame of measuring the fluid consumption q1, q2on the respective key metering points14,15.

At step21, the fluid flow Qi through the boundary8by the main pipe4is calculated using the measured fluid pressure P1, P2and fluid consumption q1, q2on the selected key metering points14,15that are located inside and outside of the discrete area2.

The flow Qi might be derived from the fluid transport equations:

Qiy=Δ⁢⁢PPR=(P1+q1γ⁢R1)-P2+q2γ⁢R2REq.⁢1
where Qiis a fluid flow in the main pipe4that crosses the boundary8of the discrete area2, i.e., between the two boundary nodes11,12, ΔPPis a pressure drop between the boundary nodes11,12, R is an equivalent hydraulic resistance of the main pipe4between the boundary nodes11,12, R1, R2are an equivalent hydraulic resistances of the distribution pipes17,5on which the selected key metering points14,15are installed, P1, P2are the fluid pressure in the respective distribution pipe17,5measured by the pressure sensors16that are installed on the key metering point14,15, q1, q2are consumptions of the fluid on the key metering points14,15measured by the consumption gauges17, and γ is a flow exponential parameter.

As a result, an installation of a costly flow meter7on the main pipe4is not needed to measure the flow of the fluid Qiby using this approach.

The same method should be applied to calculate the fluid flow Qifor every further pipe that crosses the boundary8of the discrete area2. Afterwards, by summing up the fluid flows Qiof the individual main pipes the total fluid flow into/out of the discrete area2can be calculated.

Within an enhanced embodiment of the method, the criteria to select appropriate key metering points are defined to further improve accuracy of the fluid flow calculation.FIG. 4illustrates how these criteria might be applied.FIG. 4shows a part of the supply network1. At least one main pipe4crosses the boundary8of the discrete area2. Two boundary nodes11,12are located on different sides of the boundary8.

On one side of the boundary8, inside of the discrete area2, the boundary node12is a junction of the main pipe4and the distribution pipe13with the key metering point14equipped. There are also other nodes30in the discrete area2that are fluidly connected to the consumers18via distribution pipes13with key metering points31installed on them.

However, on the other side of the boundary8that is in the further area9, outside of the discrete area2, there is a complicated pipe structure with junctions that form nodes11,22,23,24,26,27. Some nodes23,24,26,27are junctions of the main pipes4,37,38,39with the distribution pipes5, where the distribution pipes5are equipped with the key metering points15,28,29. Other junctions11,22are junctions of main pipes4,37,38,39of the further area9.

Every key metering point14,31,15,28,29is equipped with a pressure sensor16(not shown on thisFIG. 4) and a consumption gauge17(not shown on thisFIG. 4) and is adopted to measure the fluid pressure Piin the distribution pipes5on which they are installed and the fluid consumption quof the consumers18that are supplied with the fluid by the distribution pipes5.

To provide accurate calculation of the fluid flow Q11-12through the boundary8on the main pipe4between two boundary nodes11,12, within the step19of the method, at least one selected first key metering point14in the discrete area2for taking measurement should be defined. The measurement of the fluid pressure214and the fluid consumption q14should be taken from the selected first key metering point14that is inside of the discrete area2. To be selected for further measurements, the at least one selected key metering point should fit a requirement to be located next to the boundary node inside the discrete area2. In other words, all and only such key metering points should be selected as first key metering points14, which are located on their distribution pipe13such that no further key metering point is located between the selected key metering point14and the respective boundary node12inside the discrete area2.

Other key metering points31in the discrete area2, while located on the distribution pipes13that are fluidly connected to the boundary node12, do not satisfy the requirement of being the next to the boundary node12. Correspondingly, those remaining key metering points31should be excluded from the calculation of the fluid flow Q because the requirement of being the next to the boundary node12is not met and because the boundary node12itself includes the distribution pipe13with the key metering point14installed on it.

Furthermore, within step20at least one selected second key-metering point15for taking measurement for further fluid flow calculation should be defined and selected in the further area9.

The key metering points15located in the further area9should be taken for further measurement. All of them are located on distribution pipes5that are fluidly connected to the boundary node11in the further area9, and each selected second key metering point15is a next one to the boundary node11, i.e., there are no further key metering points located between the respective selected second key metering points15and the boundary node11outside the discrete area2, i.e., inside the further area9. Lastly, all and only such key metering points15are selected as second key metering points15, which are located on their distribution pipe5such that no further key metering point is located between the selected key metering point15and the boundary node11inside the discrete area2.

In contrast, the remaining key metering points29,28should be excluded from the calculation because the requirement of being the next to the boundary node11is not met. For example, between the boundary node11and the key metering point29there is another node24to which the distribution pipe5with one of the selected second key metering points15equipped on it is attached.

The key metering point32is not taken for further measurement because it is located on a distribution pipe40that is not fluidly connected to the boundary node11. This key metering point32is located on another main pipe33that is fluidly connected to a boundary node34. Therefore, the fluid flow on the main pipe33might be calculated separately using the steps19-21.

After definition and selection of the first and second key metering points14,15as described above, the fluid flow Q11-12through the main pipe4that crosses the boundary8between the boundary nodes11,12into or out of the discrete area2can be calculated by using the Kirchhoff's system of equations, which are well known, applied to the water supply network1.

The system of equations should include equations for every selected key metering point15,14to calculate the fluid pressure in the nodes12,23,24of accession of a distribution pipe5where the respective selected key metering point14,15is installed on as it was described above.

Also for every two nodes23and22,11and24,11and23,11and12that are next to each other the fluid transport equations should be created:

Qi-jγ=Pi-PjRi-jEq.⁢3
where Qi-jis the fluid flow through the pipe between two nodes i and j, P1, Piis the fluid pressure in the respective nodes i and j, and Ri-jis an equivalent hydraulic resistance of the pipe between the respective nodes i and j.

Moreover, for every node22,11that is a junction of a plurality of main pipes4,37,38,39that is located between the boundary8and the respective key metering point15the equation in accordance with the Kirchhoff's junction rule should be created. The Kirchhoff's junction rule means that the algebraic sum of fluid flows meeting at a node11,22is zero.

Such a system of equations can be solved because the number of the unknown parameters equals the number of equations created. Therefore, the fluid flow Q11-12through the main pipe4that crosses the boundary8between two boundary nodes11,12into or out of the discrete area2can be derived from this system.

After the calculation of the fluid flow Qiis performed for every main pipe4,33that crosses the boundary8of the discrete area2, the total fluid flow can be derived by summing up the fluid flow Qifor every main pipe4,33.

FIG. 5shows a preferred embodiment of a key metering point14where the pressure sensor16and the consumption gauge17of the key metering point14are located in different places. The consumption gauge17is located downstream of the pressure sensor16, where the direction of flow is from the node12to the consumer18and the consumption gauge17is located between the pressure sensor16and the consumer18.

FIG. 6illustrates a key metering point14with a plurality of the consumption gauges17. The consumption gauges17are installed downstream the pressure sensor16. It might happen when the pressure sensor16is installed on the distribution pipe13that provides fluid to the conglomerate of consumers18, e.g., a house with a plurality of apartments, while the consumption gauges17are installed in every apartment. Here, the total consumption of all consumers18that are located downstream the key metering point should be taken for further calculation the fluid flow Qi.

In a possible embodiment, the fluid supply network is a water supply network and the discrete area is a district metered area DMA.

FIG. 7shows a system36for fluid flow measurement for a discrete area2of a fluid supply network in accordance with the present invention. The system36as described above in theFIG. 2comprises a plurality of key metering points, i.e., at least two,14,15, where each key metering point14,15is located on a distribution pipe5,13respectively and equipped with a pressure sensor16and a consumption gauge17.

Each pressure sensor16is configured to perform a measurement of fluid pressure Piin the distribution pipe5,13at which the pressure sensor16is installed. Each consumption gauge17is configured to measure fluid consumption qiby consumers18that are fluidly connected by the distribution pipe5,13. Moreover, at least one key metering point14is located inside the discrete area2and at least one key metering point15is located in the further area9, i.e., outside of the discrete area2. The key metering points14,15are configured to provide measured data.

The system also comprises a control unit35configured to perform calculation of the fluid flow by using the measured data in accordance with the method of the disclosed embodiments.

While the invention has been illustrated and described in detail with the help of preferred embodiment, the invention is not limited to the disclosed examples. Other variations can be deducted by those skilled in the art without leaving the scope of protection of the claimed invention.