WO2019220013A1

WO2019220013A1 - Detecting hidden faults in distribution networks

Info

Publication number: WO2019220013A1
Application number: PCT/FI2019/050380
Authority: WO
Inventors: Heikki SEPPÄ
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2018-05-16
Filing date: 2019-05-15
Publication date: 2019-11-21

Abstract

According to an example aspect of the present invention, There is provided detecting hidden faults in distribution networks. When input flow and output flow of the distribution network indicate a hidden fault, location of the hidden fault is determined by determining one or more pressure distributions based on the hidden fault being located at a proposed location of the distribution network. Then differences of the determined pressure distributions are determined with respect to a reference pressure distribution and the location of the hidden fault is determined in the proposed location, where the difference between the pressure distribution corresponding to the proposed location and the reference pressure distribution is the smallest.

Description

DETECTING HIDDEN FAULTS IN DISTRIBUTION NETWORKS

FIELD

[0001] The present invention relates to detecting hidden faults in distribution networks and more particularly detecting locations of hidden faults.

BACKGROUND

[0002] Distribution networks convey resources such as electricity and various fluids from supplies to end users for satisfying basic needs of today’s dwellings and industry. The distribution networks typically involve large investments by private businesses, municipalities and nations for providing a country or a smaller geographical region with distribution services of electricity and fluids for facilitating economic growth, industrialization and a desired living standard. The electricity and fluid such as gas, oil and water conveyed by the distribution networks, are typically considered necessities in a modem society. However, supplies of electricity and/or fluid are many times scarce and therefore efficiency of the distribution network should be high to provide that as large share as possible of the scarce resources are conveyed to the end users.

[0003] Poor condition of the distribution network and/or theft of the conveyed resources can be significant regarding the efficiency of the distribution network. The poor condition can be remedied by repairing faulty parts of the distribution network. However, typically the distribution network is located in a densely inhabited area and close to other infrastructure such as roads and railways. Accordingly, repairing the network can cause damage to the other infrastructure, for example if excavation is needed, or at least the other infrastructure may slow down the repairs and make detection of the faults more difficult.

[0004] In a water distribution network, locations of large leakages can be detected, when the amount of water leaking from the network is large enough such that the water surfaces on the ground. Locations of such leakages can be easily detected provided that the water has surfaced in an area that is inhabited and people can observe and report the leakage. However, smaller leakages may be left undetected since if the amount of leaked water is absorbed by the soil and the leaked water is not surfaced on the ground. [0005] Current methods for maintenance of distribution networks rely on renewing the networks based on expected lifetime of the networks and a large part of the faults and theft are left undetected.

SUMMARY OF THE INVENTION

[0006] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0007] According to a first aspect of the present invention, there is provided a method for detecting a hidden fault in distribution networks comprising - obtaining, by measurement instruments, input flow, output flow and pressure values, wherein the measurement instruments are connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network;

- determining, by a processor connected to the measurement instruments, a reference pressure distribution of the distribution network or said portion of the distribution network;

- comparing, by the processor, the input flow to the output flow and if a result of the comparison indicates a hidden fault:

- determining one or more proposed locations of hidden faults in the distribution network or said portion of the distribution network;

- determining, by the processor, one or more further pressure distributions of the distribution network on the basis of pressure caused by the hidden fault at proposed locations of hidden faults, wherein each further pressure distribution is determined based on one or more proposed locations of hidden faults;

- determining, by the processor, differences between the further pressure distributions and the reference pressure distribution;

- determining, by the processor, a location of the hidden fault in the proposed location corresponding to the further pressure distribution having the smallest difference to the reference pressure distribution. [0008] According to a second aspect of the present invention, there is provided a system for detecting hidden faults in distribution networks, comprising at least one processor, at least one communications interface connected to the processor and to measurement instruments connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network, at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor and communications interface, cause the system at least to perform:

- obtaining input flow, output flow and pressure values;

- determining a reference pressure distribution of the distribution network or said portion of the distribution network;

- comparing the input flow to the output flow and if a result of the comparison indicates a hidden fault:

- determining one or more further pressure distributions of the distribution network on the basis of pressure caused by the hidden fault at proposed locations of hidden faults, wherein each further pressure distribution is determined based on one or more proposed locations of hidden faults;

- determining differences between the further pressure distributions and the reference pressure distribution;

- determining a location of the hidden fault in the proposed location corresponding to the further pressure distribution having the smallest difference to the reference pressure distribution.

[0009] According to a third aspect of the present invention, there is provided a non- transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:

- detecting hidden faults in distribution networks; - obtaining, by measurement instruments, input flow, output flow and pressure values, wherein the measurement instruments are connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network; - determining, by a processor connected to the measurement instruments, a reference pressure distribution of the distribution network or said portion of the distribution network;

- determining one or more proposed locations of hidden fault in the distribution network or said portion of the distribution network;

- determining, by the processor, one or more further pressure distributions of the distribution network on the basis of pressure caused by the hidden fault at proposed locations of hidden fault, wherein each further pressure distribution is determined based on one or more proposed locations of hidden faults;

- determining, by the processor, a location of the hidden fault in the proposed location corresponding to the further pressure distribution having the smallest difference to the reference pressure distribution.

[0010] According to a fourth aspect of the present invention, there is provided a computer program configured to cause a method in accordance with an aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGURE 1 illustrates a distribution network in accordance with at least some embodiments of the present invention. [0012] FIGURE 2 illustrates a system in accordance with at least some embodiments of the present invention.

[0013] FIGURE 3 illustrates a method in accordance with at least some embodiments of the present invention.

EMBODIMENTS [0014] There is provided detecting hidden faults in distribution networks. When input flow and output flow of the distribution network indicate a hidden fault, location of the hidden fault is determined by determining one or more pressure distributions based on the hidden fault being located at a proposed location of the distribution network. Then differences of the determined pressure distributions are determined with respect to a reference pressure distribution and the location of the hidden fault is determined in the proposed location, where the difference between the pressure distribution corresponding to the proposed location and the reference pressure distribution is the smallest.

[0015] FIGURE 1 illustrates a distribution network 100 in accordance with at least some embodiments of the present invention. The distribution network or at least a portion of the distribution network may be internal to a building or other structure, or the distribution network covers a geographical area between a supply 102 of a flow and end users. The geographical area may be a settled area, for example a village, town or a city, or a part of the village, town or a city. The infrastructure network provides distribution service of the flow, such a flow as flow of electric current or flow of fluid such as oil, gas or water, within the geographical area. The distribution network may be connected to the supply and end users. The distribution network may comprise one or more parts that are connected to either the supply or the end user or the parts may be intermediate parts of the distribution network. The intermediate parts of the distribution network are connected together such that the flow may be supplied from the supply to the end users. [0016] The distribution network comprises means 101 for carrying electric current or fluid from the supply 102 through the distribution network towards the end users connected to the distribution network at one or more outputs 104, 105, 106, 107 of the distribution network. The distribution network may carry electric current by means of lines or cables that conduct electricity. The distribution network may carry fluid by means of piping or channels. The distribution network may be a gas distribution network, an electrical energy distribution network, an oil distribution network or a water distribution network. Examples of the electrical energy distribution network, i.e. a power grid, may comprise an electric power distribution network or an electric power transmission network. Examples of the supplies comprise an electrical power plant and storages of water, oils and gas.

[0017] At the outputs 104, 105, 106, 107, the distribution network may be connected to end user terminal devices or to intermediary devices that serve for connecting the distribution network to another network or a sub-portion of the distribution network. In the latter case, the end users may be connected to outputs of said another network or sub- portion of the distribution network.

[0018] Examples of end user terminal devices comprise end user appliances capable of utilizing the electric current or fluid carried by the distribution network. Examples of end user appliances for utilizing the electric current comprise fuse panels and electrical house hold appliances. Examples of end user appliances for utilizing water comprise water taps, shower heads and central heating systems.

[0019] Examples of the intermediary devices for electrical energy distribution networks comprise distribution substations and transformers. Examples of the intermediary devices for water distribution networks comprise water towers and storage tanks.

[0020] Examples of end user and intermediary devices for oil and gas distribution networks comprise industrial appliances which are considered well-known to the skilled person.

[0021] An electric power transmission network carries electrical energy from a power supply, for example a power plant, to distribution substations connecting the power transmission network to electric power distribution networks. At the distribution substations, transformers are used to lower down the voltage of the transmission network to distribution lines of the electric power distribution network.

[0022] An electric power distribution network is the final stage in the delivery of electric power from an electrical power supply such as an electrical power plant to an end user. The electric power distribution network carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging e.g. between 2 kV and 35 kV with the use of transformers. Primary distribution lines carry this medium voltage power to distribution transformers located near the end user’s premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment or household appliances. Often several end users are supplied from one transformer through secondary distribution lines. Commercial and residential end users are connected to the secondary distribution lines through service drops. End users demanding a much larger amount of power may be connected directly to the primary distribution level or the sub-transmission level.

[0023] Measurement instruments 103, 108 for measuring input flow, output flow and pressure of the flow carried by the distribution network may be connected to the distribution network. Preferably, each measurement instruments is configured to measure both flow and pressure such that both flow values and pressure values may be obtained at the location, where measurement instrument is installed. The measurement instruments may generate values of the input flow, output flow and the pressure such that a total flow carried by the distribution network or said at least a portion of the distribution network and pressure of the distribution network may be measured. The total flow may be a flow that is input to the distribution network and carried by the distribution network to one or more outputs of the distribution network. However, if the distribution network has hidden faults, it should be appreciated that only a part of the total flow is carried to the outputs.

[0024] The input flow and pressure may be measured by one or more measurement instruments 103 connected to the distribution network to a location at the input of the distribution network or substantially at input of the distribution network or at least very close to the input of the distribution network such that locations of hidden faults may be determined downstream of the input. The output flow and pressure may be measured by one or more measurement instruments 108 connected to the distribution network to a location at outputs, preferably at all outputs, of the distribution network or substantially at the outputs of the distribution network or at least very close to the outputs of the distribution network such that locations of hidden faults may be determined upstream of the outputs. It should be appreciated that an input of the distribution network may be an input to the whole distribution network or a part of the distribution network. Similarly, an output of the distribution network may be an output to the whole distribution network or a part of the distribution network.

[0025] At least in some embodiments the measurement instruments comprise at least part of fluid flow meters, electrical current meters, pressure meters and voltage meters. The measurement instruments may be chosen according to the distribution network, for example an electrical energy distribution network or a fluid distribution network such as oil, gas or water network.

[0026] The distribution network may comprise one or more hidden faults 109. The hidden faults in a fluid distribution network may comprise a leakage of the fluid carried by the distribution network. The hidden faults in an electrical energy distribution network may comprise an electrical load causing a voltage drop or an electrical current drain in the electrical energy distribution network. Accordingly, in general, the hidden fault is a fault of the distribution network to distribute at least partly or a total failure to distribute a flow, such as flow of electric current or fluid, the latter comprising for example oil, gas or water. Since the distribution of the flow is faulty, at least part of the flow or all of the flow may be considered a loss and a challenge regarding the efficiency of the distribution network.

[0027] The hidden faults are caused by aging of the distribution network, aging of individual components of the distribution network, external effects to the distribution network and/or manufacturing faults of the components of the distribution network after the distribution network has been deployed and taken into use. When the distribution network is deployed and taken into use, access to the distribution network may be limited or not possible at all, since access to the distribution network may be blocked by other infrastructure. Access to the distribution network may be blocked for example, when the distribution network is underground and when the distribution network is under a road. Accordingly, locations of the hidden faults may be unknown and at least difficult to find out. [0028] FIGURE 2 illustrates a system 200 in accordance with at least some embodiments of the present invention. At least one communications interface 202 connected to one or more processors 204 and to measurement instruments 203. The measurement instruments 203 may be measurement instruments connected to a distribution network described with FIGURE 1, for example. At least one memory 201 including computer program code may be connected to the processor to cause with the at least one processor and communications interface one or more functionalities described with an embodiment. The communications interface provides at least that the processor may obtain input flow, output flow and pressure values from the measurement instruments.

[0029] It should be appreciated that the processor may be connected to one or more further communications interfaces 206 such that the information may be received by the processors from a user communications equipment 208 connected to at least one of the further communications interfaces and/or transmitted by the processors to a user communications equipment 208 connected to at least one of the further communications interfaces.

[0030] In an example a user communications equipment 208, for example a smart phone, a handheld communications device, a handheld computing device or a computing device may be connected to the processor via the further communications interfaces 206. The communications equipment may comprise a user interface for input of information by the user and for output of information to the user. The user interface may comprise one or more buttons, a keypad or a computer mouse for allowing the user to input information. The user interface may comprise one or more displays, speakers, and a haptic device for allowing output of information to the user. In an example the user interface is a touch screen such that both input and output of information may be provided.

[0031] In an embodiment, the system 200 is a cloud computing system. The cloud computing system provides that the system may be connected to one or more distribution networks for detecting hidden faults. The distribution networks may be geographically at different locations, whereby the cloud computing system provides that the separate distribution networks may be managed by a single system. Moreover, the distribution networks may be of different types, whereby different types of distribution networks may be managed. The cloud computing system may obtain information of configuration, maintenance and faults of each distribution network connected to the cloud computing system, whereby the obtained information may be analyzed and utilized in detecting hidden faults of any of the distribution networks.

[0032] Information of the locations of the hidden faults determined by the system may be accessed by the user communications equipment 208 connected to the cloud computing system. In an example, one or more locations of the hidden faults determined by the system may be displayed on a user interface of the user communications equipment 208 connected to the cloud computing system. The cloud computing system may provide a web-based user interface that the user communications equipment may access for displaying locations of the hidden faults on the user communications equipment and/or select which information available at the system is used for detecting hidden faults.

[0033] FIGURE 3 illustrates a method in accordance with at least some embodiments of the present invention. The method may be performed by a system in accordance with the system described in FIGURE 2. The method may provide detecting hidden faults in distribution networks.

[0034] The method comprises phase 302 of obtaining, by measurement instruments, input flow, output flow and pressure values, wherein the measurement instruments are connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network. The pressure values may be values of pressure that is an electric pressure i.e. voltage or a fluid pressure. Accordingly, method may be applied to electrical energy distribution networks and fluid distribution networks.

[0035] Phase 304 comprises determining, by a processor connected to the measurement instruments, a reference pressure distribution of the distribution network or said portion of the distribution network. The pressure distribution provides information of pressure values measured at a plurality of locations in the distribution network. The pressure values correspond to pressures associated with flows at specific time instants at locations, where the measurement instruments are installed to the distribution network.

[0036] Phase 306 comprises comparing, by the processor, the input flow to the output flow and if a result of the comparison indicates a hidden fault, the phases 308 to 314 are performed. If a result of the comparison does not indicate a hidden fault, the phase 302 may be executed for obtaining further measurements.

[0037] Phase 308 comprises determining one or more proposed locations of hidden fault in the distribution network or said portion of the distribution network.

[0038] Phase 310 comprises determining, by the processor, one or more further pressure distributions of the distribution network on the basis of pressure caused by the hidden fault at proposed locations of hidden fault, wherein each further pressure distribution is determined based on the proposed locations of hidden fault. The further pressure distributions take into account pressures caused by the flows of the hidden faults, whereby effect of the hidden faults to the pressure distribution may be evaluated. The pressure values of each of the further pressure distributions correspond to pressures associated with flows at specific time instants at locations, where the measurement instruments are installed to the distribution network and the hidden fault is at one of the proposed locations.

[0039] Phase 312 comprises determining, by the processor, differences between the further pressure distributions and the reference pressure distribution. The evaluation provides that the effect of detecting the hidden fault at the proposed locations may be evaluated against the undetected situation using pressure distributions.

[0040] Phase 314 comprises determining, by the processor, a location of the hidden fault in the proposed location corresponding to the further pressure distribution having the smallest difference to the reference pressure distribution. In this way the hidden fault may be detected at one of the proposed locations.

[0041] Examples of the reference pressure distribution comprise a pressure distribution of the distribution network or a part of the distribution network, where the hidden fault is present but not detected. When the hidden fault is not detected, its effect on the pressure distribution is ambiguous in the sense that a pressure drop or other pressure changes due to the hidden fault cannot be fixed to a location in the distribution network. The pressure distribution comprises pressure values measured at a plurality of locations of the distribution network. The locations may comprise at least one or more input and output locations. [0042] In an example, phase 306 comprises that the hidden fault is determined, when the input flow and output flow of the distribution network or a part of the distribution network are not substantially the same. The output flow may be smaller due to loss of flow caused by the hidden fault.

[0043] In an example, phase 308 comprises that the proposed locations of the hidden faults are chosen randomly. On the other hand the proposed locations may be chosen to be locations of construction work in the geographical area of the distribution network. In this way locations of the hidden faults caused particularly by construction work may be detected. It should be appreciated that also other information, alternatively or additionally to locations of construction work, that is associated with locations of the distribution network and associated with actions that are capable of causing hidden faults of the distribution network may be chosen as proposed locations of hidden faults. Examples of such information comprise maintenance work of the distribution network, construction work of the distribution network, and fault information of infrastructure that is nearby or co-located with the distribution network.

[0044] In an embodiment, phase 306 may comprise that the output flow is obtained from end user measurement instruments or measurement instruments deployed in the distribution network between a supply and the end users. The location of the measurement instruments provides that locations of hidden faults may be detected upstream from the measurement instruments. Accordingly, it should be appreciated that also other locations upstream from the end users are viable. The upstream direction may be considered the direction towards a source of the flow, e.g. a supply such as a supply station or a power plant.

[0045] In an embodiment, the input flow is obtained from a supply, for example a water supply plant, electric power plant or a transformer station. Other examples include various reservoirs of fluid. In this way locations of hidden faults may be detected downstream from the measurement instruments. Accordingly, it should be appreciated that the input flow may be obtained also further downstream from the supply.

[0046] In an embodiment, phase 310 comprises that the further pressure distributions are determined based on pressure values determined during use of the distribution network or said portion of the distribution network during different times of day and a plurality of configurations of input flows and output flows. In this way sufficient amounts of values of input flow, output flow and pressures may be obtained such that variances to the measured values caused by different usages of parts of the distribution network at different times of day may be evened out.

[0047] In an embodiment, phase 314 comprises that the location of the hidden fault is adjusted for minimizing differences between the further pressure distributions and the reference pressure distribution. In this way the location of the hidden fault may be determined at the location, where the difference to the reference distribution is the smallest.

[0048] In an example, the hidden location may be first determined coarsely to be in a specific portion of the distribution network from a plurality of portions of the distribution network. In this way, once a sufficient certainty has been achieved that a hidden fault is in a specific portion of the network, a computational model of the specific portion of the distribution network may be used to adjust the location of the hidden fault and determine a more exact location of the hidden fault.

[0049] More particularly, the coarse location of the hidden location may be adjusted by using the computational model to determine an updated pressure distribution, where the hidden fault is positioned at a location x, y, i.e. a proposed location, between an input and output to the specific portion. The computational model may define characteristic of the distribution network between the input and the output via the location x,y such that a pressure value measured upstream or downstream the location may be converted to a pressure value at the location x, y. Then, measurement pressure and flow at the input and output together with the computational model may be used to determine an updated pressure distribution e.g. in accordance with Eq. (2) below, when the hidden fault is positioned at the proposed location x,y between the input and output. The computational model may be for example a linear model of the portion of the distribution network. The computational model may be adapted to take into account non-linearities caused by variances of the distribution network, e.g. variances of pipe diameters in the section. The non-linearities may be calculated from input and output flows.

[0050] It should be appreciated that the method may utilize a principle that the sum of the output flows of the distribution network equals to the input flow to the distribution network. Moreover, the method may be applied to distribution networks having more than one input flows, but the principle is described herein using only one input flow for the sake of illustration of the general principle.

[0051] In at least some embodiments, a pressure distribution may be determined on the basis of pressure and flow values measured at a plurality of locations of the distribution network and the measurements follow the equation:

P(t) -P₀(t)Y=R(T)I(t)+£(T,t) (1),

, where P is time dependent pressure vector of pressure values measured at outputs and may serve as a reference pressure distribution for example in phase 304 in FIGURE 3, Y is a unit vector, R is loss matrix dependent on length of the piping and topology of the distribution network, I is time dependent output flow vector and e(T,ί) is error vector and Po is a reference pressure that indicates a total flow input to the distribution network. Accordingly, the left side of the Eq. (1) indicates a pressure difference between the input and outputs of the distribution network. The vectors P, Y and I are N-dimensional vectors and R is NxN dimensional matrix, where N is the number of the output flows from the distribution network receiving the input flow. It should be noted that Equation (1) does not concern all the aspects but only those necessary for utilizing the principle in at least some embodiments. For example, one skilled in the art may understand that the Equation (1) may need modifications, if pressure differences caused by elevation levels are to be taken into consideration. The error vector e includes effects of hidden faults of the distribution network and the error vector is both slowly, T, and fast, t, time variant. Initially, the loss matrix R of the distribution network may be known or calculated based on characteristics of the distribution network such as length of the distribution network and topology of the distribution network. Additionally or alternatively, the loss matrix or information for defining the loss matrix may be determined on the basis of measurements of input flow, output flow and pressure obtained from measurement instruments installed to the distribution network, when there are no hidden faults. The information for defining the loss matrix may comprise, measurements of pressure P, flow I and information of lost flow due to hidden faults e, whereby the R may be solved from Eq. (1).

[0052] It should be appreciated that the loss matrix or information for defining the loss matrix may also be determined to existing distribution networks having hidden faults, whereby the initial situation represented by the loss matrix R includes the current hidden faults in the network. Moreover, it should be appreciated that with time measurements of flow and pressure from the distribution network accumulate and the loss matrix may be determined more accurately.

[0053] Once the loss matrix or the information for defining the loss matrix has been determined, a computational model, for example a linear model, may be generated for a section of the distribution network, where input flow, output flow and corresponding pressure values the section are measured. The computational model may be adapted to take into account non-linearities caused by variances of the distribution network, e.g. variances of pipe diameters in the section. The non-linearities may be calculated from input and output flows.

[0054] Using the computational model and the loss matrix or the information for defining the loss matrix, a location of the hidden fault may be determined by determining one or more proposed locations of the hidden faults. The proposed locations of the hidden faults may be chosen randomly. On the other hand the proposed locations may be chosen to be locations of construction work in the geographical area of the distribution network. In this way locations of the hidden faults caused particularly by construction work may be detected.

[0055] It should be appreciated that also other information, alternatively or additionally to locations of construction work, that is associated with locations of the distribution network and associated with actions that are capable of causing hidden faults of the distribution network may be chosen as proposed locations of hidden faults. Examples of such information comprise maintenance work of the distribution network, construction work of the distribution network, and fault information of infrastructure that is nearby or co-located with the distribution network.

[0056] The proposed locations of hidden faults may be used to obtain an updated loss matrix R_u that is fixed to the proposed location of the leakage. The updated loss matrix R_u and/or information for defining the updated loss matrix may be obtained based on estimates of pressure and flow at the proposed locations and the measurements of pressure and flow obtained from the distribution network. The updated loss matrix and measurements of pressure and input and output flows may follow the equation: P_u(t) -P₀(t)Y=R_u(T)I_u(t)+c(T,t) (2),

where P_u, P₀, Y and I„ and correspond to R are P, Y and I and R described with with Eq. (1) but P_u, Y and I„ are N+l dimensional and R_u is (N+l)x(N+l) dimensional matrix, where N+l is the number of output flows including the number of locations of hidden faults in the distribution network or part of the distribution network receiving the input flow. P_u may serve as a further pressure distribution determined on the basis of pressure caused by the hidden fault at a proposed location of hidden faults, for example in phase 310 in FIGURE 3. It should be appreciated that hidden faults may be determined to be detected to be located at the proposed locations, when the length of the vector e is minimized. The length of the vector e may be determined to be minimized, when the length of the vector e is smaller than a threshold and/or when the length of the vector is minimized for a set of proposed locations of hidden faults. The e may represent a difference to a reference pressure distribution. The reference pressure distribution may be a pressure distribution, where the hidden fault is present but not detected. In an example the reference pressure distribution may be P in Eq. (1).

[0057] It should be appreciated that the determining the location of the hidden fault may comprise receiving measurements of pressure, input flow and output flow for a time period, where flow and pressure in any given measurement location may vary based on usage of the distribution network by end users. It should be appreciated that at each proposed location may be evaluated separately.

[0058] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0059] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0060] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0061] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0062] While the foregoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0063] The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0064] The present invention is at least applicable in maintenance of distribution networks.

REFERENCE SIGNS LIST 100 Distribution network

101 Means for carrying electricity or fluid

102 Supply

103, 108 Measurement instruments

104-107 Outputs of the distribution network 109 Hidden fault

200 System

201 Memory

202, 206 Communications interface

203 Measurement instruments

204 Processor

208 User communications equipment

302 to 314 Phases of the method of FIGURE 3

Claims

CLAIMS:

1. A method for detecting a hidden fault in distribution networks:

- obtaining, by measurement instruments, input flow, output flow and pressure values, wherein the measurement instruments are connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network;

2. The method according to claim 1, wherein the further pressure distributions are determined based on pressure values determined during use of the distribution network or said portion of the distribution network during different times of day and a plurality of configurations of input flows and output flows.

3. The method according to claim 1 or 2, wherein the location of the hidden fault is adjusted for minimizing differences between the further pressure distributions and the reference pressure distribution.

4. The method according to any of the preceding claims, wherein the output flow is obtained from end user measurement instruments or measurement instruments deployed in the distribution network between a supply and the end users.

5. The method according to any of the preceding claims, wherein the input flow is obtained from a supply, for example a water supply plant, electric power plant or a transformer station.

6. The method according to any of the preceding claims, wherein the measurement instruments comprise at least part of fluid flow meters, electrical current meters, pressure meters and voltage meters.

7. The method according to any of the preceding claims, wherein the distribution network or at least a portion of the distribution network is internal to a building or covers a geographical area between a supply and end users.

8. The method according to any of the preceding claims, wherein the pressure is electric pressure i.e. voltage or a fluid pressure.

9. The method according to claim 1 or 2, wherein the distribution network is a gas distribution network, an electrical energy distribution network, an oil distribution network or a water distribution network.

10. A system for detecting hidden faults in distribution networks, comprising

at least one processor,

at least one communications interface connected to the processor and to measurement instruments connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network, at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor and communications interface, cause the system at least to perform:

- obtaining input flow, output flow and pressure values;

- determining one or more further pressure distributions of the distribution network on the basis of pressure caused by the hidden fault at proposed locations of hidden faults, wherein each further pressure distribution is determined based on one or more proposed locations of hidden faults; - determining differences between the further pressure distributions and the reference pressure distribution;

11. The system according to claim 10, wherein the system is a cloud computing system.

12. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:

detecting hidden faults in distribution networks;

obtaining, by measurement instruments, input flow, output flow and pressure values, wherein the measurement instruments are connected to a distribution network or at least a portion of the distribution network for measuring a total flow carried by the distribution network or said at least a portion of the distribution network and for measuring pressure of the distribution network;

determining, by a processor connected to the measurement instruments, a reference pressure distribution of the distribution network or said portion of the distribution network;

comparing, by the processor, the input flow to the output flow and if a result of the comparison indicates a hidden fault:

13. A computer program configured to cause a method in accordance with at least one of claims 1 to 9 to be performed.