Device for detecting power grid faults, power grid or equipment comprising such a device, and method for detecting faults

Abstract

The invention relates to a device (D) for detecting a fault in an electric network (1), the electric network (1) comprising at least one electrical device (E), the at least one electrical device (E) being electrically connected to a first power conductor (C1) and a second power conductor (C2), the electric network (1) being provided with a common conductor (Cc). The device comprises: a first measuring member (O1) for measuring a common mode voltage present on the power conductors (C1, C2); and a second measuring member (O2) for measuring a current flowing in the power conductors (C1, C2). The device also comprises a calculator (UP) configured to calculate, within a determined observation period, a value of a common mode voltage according to a first variable (V res ) and the second variable (I net ) determines the mixed energy (E) transmitted in the measurement area mix ). The invention also relates to a device, a positioning system and a method for detecting faults in an electrical network.

Description

Technical Field

[0001] The present invention relates to a device and a method for detecting a fault in an electric energy distribution network. The present invention also relates to an electric energy distribution network or an installation equipped with such a detection device. Background Art

[0002] The need to reduce the carbon footprint of human activity and optimize energy efficiency has led to the use of electrical energy. This effort requires the transmission of electrical energy in the form of direct current (DC) or alternating current (AC) between one or more sources (e.g., batteries, generators, photovoltaic panels) and one or more loads (e.g., motors, inverters) through distribution lines and protection systems (circuit breakers, disconnectors, and other disconnecting components). The collection of sources, loads, lines, and protection systems constitutes the electrical grid.

[0003] Sometimes, power grids are required to transmit large amounts of power, potentially exceeding tens of kilowatts, hundreds of kilowatts, or even megawatts. For example, power grids may be installed in vehicles such as land vehicles (cars or tanks), railways, surface ships or submarines, or aircraft. Consequently, power grids may operate in harsh environments, characterized by significant fluctuations in temperature, pressure, vibration, electromagnetic fields, or humidity. In these applications, power grid failures can have serious consequences, making them essential for safety and protection.

[0004] More generally, regardless of the application area, it is important to be able to detect and advantageously localize faults occurring in power grids. Power grids are typically protected by protective devices, and the detection of a fault causes these devices to switch, electrically isolating at least a portion of the grid. These protective devices can be, for example, circuit breakers, contactors, solid-state switches, fuses, or current limiters, which activate when an excessive current occurs. Localizing the fault makes it possible to isolate only the faulty portion of the grid. This feature has the advantage of maintaining a minimum level of grid operation and enabling targeted intervention by maintenance teams.

[0005] Faults that can occur in power grids can have various characteristics: insulation defects, losses caused by excessive switching at load levels, excessive energy consumption, short circuits, and so on. Faults can also occur as arcs within or between the conductors and electronic devices that make up the distribution lines. Arcing corresponds to unintentional electrical discharges that propagate through the gas (air) between two conductive segments of the power grid. When such discharges occur in the electrical insulation surrounding a conductor but do not completely destroy it, they are called partial discharges. These discharges can be caused by many factors, such as improper conductor connections, degraded electrical insulation surrounding these conductors, the presence of foreign matter, or poor insulation quality. These factors are common in power grids and can lead to fires, explosions, significant local temperature increases exceeding 10,000°C, high overpressure, and the emission of significant ultraviolet radiation. Ambient humidity, low air pressure, and temperature contribute to the occurrence of these arcs, making early detection of arcs particularly important when power grids operate in harsh environments, such as those described above.

[0006] Conventional protection devices (such as circuit breakers) trigger based on excessive current or power consumption and often fail to detect arcs early enough. Some arcs develop over a long period of time, without causing overcurrent or overpower in the power grid, making early detection impossible using conventional methods. This is particularly true for "series" arcs, which can form in power conductors or connectors. The power consumed during the initiation of a series arc is much lower than that of a parallel arc or the nominal power of the power grid.

[0007] Detection of arcs in power grids is typically performed by monitoring the time and / or frequency evolution of grid signals (current and / or voltage), knowing that the occurrence of this phenomenon results in the formation of signals with strong spectral components, even in the case of DC grids. An example of such a detection solution is described, in particular, in document US10078105. However, these methods based on time or spectral analysis of signals (current and / or voltage) are particularly difficult to implement and result in many false alarms, which can be caused by loads or active (i.e., switched) sources present on the grid. In particular, these methods are not effective in detecting the occurrence of series arcs in DC grids.

[0008] Purpose of the Invention

[0009] The object of the present invention is to remedy the aforementioned disadvantages. One object of the present invention is, in particular, to provide a device and a method for detecting faults in an electrical network, which are particularly reliable and suitable for detecting the occurrence and advantageously locating various faults, including arcs, in particular series arcs, in particular in DC power networks. Summary of the Invention

[0010] To achieve this object, the present invention proposes a device for detecting a fault in an electrical network, in particular a DC network, the fault in particular a series arc, the electrical network comprising at least one electrical device electrically connected to a first power conductor and a second power conductor.

[0011] According to the invention, the power grid is equipped with common conductors. The device is intended to be connected to the power conductors and the common conductors of the power grid at the level of the measurement area and comprises:

[0012] - first measurement means capable of establishing a first quantity representative of the common mode voltage present on the power conductor;

[0013] - second measurement means capable of establishing a second quantity representative of the grid current flowing in the power conductor;

[0014] - a calculator connected to the first and second measuring members, the calculator being configured to determine, within a determined observation period, a quantity representative of energy called "mixed energy", "mixed energy" being defined as the integration of the product of the common mode voltage and the grid current over a determined observation period and transmitted in the measurement area, the quantity representative of the mixed energy being determined as a function of the first and second quantities.

[0015] According to other advantageous and non-limiting features of the invention, these features may be taken individually or in any technically feasible combination:

[0016] - the computer is further configured to generate a signal indicating a fault of the electrical network using the amount representing the determined mixed energy;

[0017] - the first measuring means and the second measuring means are configured to respectively determine a first quantity representative of a direct current component of the common mode voltage and a second quantity representative of a direct current component of the grid current;

[0018] - the first measuring means is further capable of establishing a third quantity representative of the differential mode voltage present between the two power conductors, and the calculator is further configured to determine, during a determined observation period, from the third quantity and the second quantity a quantity representative of grid energy transmitted in the measurement area;

[0019] - the second measuring member is further capable of determining a fourth quantity representative of the common mode current flowing in the two power conductors, and the calculator is further configured to determine, during a determined observation period, from the fourth quantity and the first quantity a quantity representative of the residual energy transmitted in the measurement area;

[0020] - The detection device further comprises a network controller, the network controller being used to connect the computer to the communication bus;

[0021] - The communication bus (BUS) is a common conductor (Cc), and the network controller (NET) is connected to the common conductor (Cc).

[0022] The present invention further provides an electrical device, such as a power supply or a load, which includes the detection device as described above.

[0023] According to another aspect, the present invention provides a system for locating a fault in an electrical network, the electrical network comprising at least a first power conductor and a second power conductor. According to the present invention, the locating system comprises:

[0024] - common conductor;

[0025] - two detection devices as described above, connected to the power conductor and the common conductor at the level of the respective measurement areas;

[0026] a monitoring device connected to the two detection devices via a communication bus, the monitoring device comprising calculation means configured to use information provided by the detection devices on the communication bus to locate a fault occurring in the electrical network comprised in a portion of the conductor between the two detection devices.

[0027] According to another aspect, the present invention provides a power grid, which is a DC or AC power grid, comprising at least two electrical devices connected via at least one first power conductor and a second power conductor, and equipped with:

[0028] - common conductor;

[0029] - a plurality of detection devices as described above, connected to the power conductors and the common conductor at the level of the respective measurement areas;

[0030] - A monitoring device connected to the detection device via a communication bus.

[0031] According to other advantageous and non-limiting features of this aspect of the invention, these features may be taken individually or in any technically feasible combination:

[0032] - The geometric shape of the power conductors is the same;

[0033] - at least one electrical device is a source, the common conductor being connected to a midpoint of the source;

[0034] - The power conductors and common conductors are assembled together in parallel to form a single cable or harness.

[0035] According to a further aspect, the present invention provides a method for detecting a fault in an electrical network, in particular a series arc fault, the electrical network comprising at least one electrical device electrically connected to two power conductors, the electrical network being provided with a common conductor. The detection method comprises the following steps:

[0036] - determining a first quantity, the first quantity (representative of a common mode voltage of the power conductor), at the level of the measurement area;

[0037] - determining a second quantity at the level of the measurement area, the second quantity being representative of a grid current flowing in a power conductor of the grid;

[0038] - Using the first quantity and the second quantity to detect the occurrence of a series arc in the electrical network.

[0039] According to other advantageous and non-limiting features of this aspect of the invention, these features may be taken individually or in any technically feasible combination:

[0040] - the detection method further comprises the steps of: determining, during a determined observation period, a quantity representing an energy called "mixed energy", "mixed energy" being defined as the integral of the product of the common mode voltage and the grid current during the determined observation period and transmitted in the measurement area, the mixed energy being determined as a function of the product of the first quantity and the second quantity;

[0041] - the detection method further comprises the steps of: processing the quantity representing the mixed energy determined during different observation periods, in particular determining the variation of this mixed energy;

[0042] The detection method comprises determining, during a determined observation period, a quantity representative of mixed energy transmitted in a plurality of measurement areas, and using the determined mixed energy to locate the occurrence of a series arc in the power grid, in particular by calculating a difference in the mixed energy.

[0043] Finally, according to another aspect, the present invention proposes a method for deploying a system for detecting faults in an electrical network, in particular series arc faults, the electrical network comprising at least a first power conductor and a second power conductor. The method comprises the following steps:

[0044] - Equip the grid with a common conductor (Cc);

[0045] - electrically connecting at least one detection device as described above to the power conductor and the common conductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other features and advantages of the present invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings, in which:

[0047] [ Figure 1a ]

[0048] [ Figure 1b ] Figure 1a and Figure 1b An example of a power grid according to an embodiment of the present invention is shown;

[0049] [ Figure 2 ] Figure 2 shows the state of the grid over time during an observation period j created by the monitoring device;

[0050] [ Figure 3 ] Figure 3 shows a portion of an electrical network according to the invention;

[0051] [ Figure 4a ]

[0052] [ Figure 4b ]

[0053] [ Figure 4c ] Figure 4a 、 Figure 4b and Figure 4c shows the grid sections during the occurrence of a parallel fault, an insulation defect fault, and a series fault respectively;

[0054] [ Figure 5 ] Figure 5 A detection device according to an embodiment of the present invention is shown.

[0055] [ Figure 6 ] Figure 6 A schematic circuit showing another embodiment of a first measuring member forming a detection device.

[0056] [ Figure 7 ] Figure 7 An example of an embodiment of a first measuring member of a detection device is shown;

[0057] [ Figure 8a ]

[0058] [ Figure 8b ]

[0059] Figure 8a and Figure 8b Another example of embodiment of the first measuring member of the detection device is shown;

[0060] [ Figure 9 ] Figure 9 A system for detecting and locating faults according to the present invention is shown.

[0061] [ Figure 10 ]

[0062] [ Figure 11 ]

[0063] Figure 10 and Figure 11 An example of a preferred embodiment of a sensor for a measuring member compatible with the detection device of the invention is shown. DETAILED DESCRIPTION

[0064] For simplicity of writing, in this specification, we will use a measured value (representing the measured or estimated amount of energy, voltage or current) of a quantity (eg, energy, voltage, current) to understand the quantity.

[0065] Power grid

[0066] Figure 1a and Figure 1b Two examples are shown of an electrical network 1, the correct operation of which is monitored by detecting the occurrence of faults in the electrical network 1 and advantageously by locating the faults. As described in the introduction to this application, these faults can have very different characteristics, be they series or parallel arcs, excessive consumption, short circuits or any other insulation defects.

[0067] In a conventional manner, the power grid 1 comprises at least two power conductors that allow the required power to be transmitted. The power grid 1 may be a direct current (DC) power grid, and the grid frequency of the power grid 1 will then be considered to be between 0 and 5 Hz, for the purpose of maintaining all generality with respect to this specification. The power grid 1 may be a conventional single-phase AC power grid with a fixed frequency of 50 Hz, 60 Hz, or 400 Hz ± 5 Hz. Alternatively, the power grid 1 may be a variable frequency AC power grid, typically between 360 Hz and 800 Hz. More generally, however, the power grid 1 may operate within any suitable frequency range. The present invention is also applicable to multiphase power grids, such as three-phase power grids.

[0068] The present invention is particularly applicable when the purpose of the power grid 1 is to transmit relatively large amounts of power between the various electrical devices, sources, or loads that make up the power grid 1. Therefore, preferably, the voltage and current values ​​developed on the power grid 1 are generally higher than 50 V, 330 V, 600 V, 1000 V, 3000 V, or 10000 V and 100 A, respectively. However, the application of the principles of the present invention to power grids that transmit relatively small amounts of power is not excluded.

[0069] As can be seen in FIG1 , a power grid 1 includes a plurality of electrical devices E (more typically, at least one electrical device E), a source or load, and wires L connecting the devices E to one another, here in the form of a mesh network, to power the loads using energy provided by the source. The electrical devices E are connected to the wires L via terminals B. Protective components (e.g., circuit breakers, disconnectors, or any other disconnecting components) are part of the power grid 1 and its electrical devices E, even though they are not shown in the drawing.

[0070] The electrical device E can be any type of device suitable for the application field of the power grid. Some of these devices E can alternately form a source and a load (generator / motor). The device can be a power distribution device. The device can be an active device (such as an inverter) or a passive device. When the electrical device E forms a source, the electrical device E can be, for example, a battery or a generator or a photovoltaic panel or a wind turbine. A combination of several sources and several loads can exist in the same power grid. Figure 1b In , we denote the distribution equipment E1 which is arranged at the level of the grid node between the source Es and the two loads which are arranged at the ends of the line L.

[0071] In order to achieve protection of the power grid 1, the power grid 1 is equipped with common conductors (the common conductors will be described in more detail later in this description) and comprises at least one detection device D, advantageously a plurality of such devices D, distributed in the power grid 1 at the level of a plurality of measurement areas. The detection device D has connection terminals that enable the detection device D to be connected to the conductors of the line L or the electrical equipment E, so as to effectively place the detection device D in the power grid. Preferably, the detection device D is non-invasive, i.e. the detection device D is connected in parallel with the power conductors of the line L and the equipment E forming the power grid 1 (for example to perform voltage measurements), or the detection device D implements a non-invasive sensor (for example a sensor of the air coil type, a Hall effect or Neel effect for measuring current). type of sensor). This reduces the number of interconnections on the conductors, thereby reducing the risk of arc-type faults.

[0072] The present invention provides for a differentiation of all the energies transmitted by the grid, and therefore, at the level of each measurement area, a distinction is made between an energy called "grid energy", an energy called "residual energy" and an energy called "mixed energy". The grid energy corresponds to the energy transmitted in the measurement area when the grid is perfectly balanced and without any faults. The residual energy and the mixed energy reflect the imbalance in the grid 1 caused by the occurrence of grid faults. However, in a healthy grid, the residual energy and the mixed energy are not completely zero due to certain natural imbalances. For this reason, according to some embodiments of the present invention, it is foreseen to measure point-to-point differences or differences between multiple energies at different moments in time in order to detect certain faults and also to locate them, but without generating false alarms related to natural imbalances.

[0073] As will be described in detail later in this specification, the detection device D according to one embodiment of the present invention is adapted to measure the grid energy E during a continuous observation period. net , residual energy E res and mixed energy E mix, these energies are transmitted at the level of the measurement area of ​​the network 1 where the detection device D is located. The measurement of these energies makes it possible to detect and sometimes locate faults occurring in the network 1 or in a part of the network 1. At least such a detection device D is suitable for measuring mixed energies E mix , in order to be able to detect series arcs. For the sake of clarity, let us clarify that by "locating the fault" we mean the ability to identify the portion of the network 1 where the fault occurs or to identify the device E where the fault occurs. This portion can be defined by the portion of the network included between the two detection devices D, or by the source type devices E arranged upstream of the devices D, or by the load type devices E arranged downstream of the detection devices D.

[0074] The electrical network 1 may also include a protection device P or a plurality of such devices P, making it possible to isolate a portion of the electrical network 1 (e.g. a line L or an electrical device E). The protection device P may be, for example, a conventional circuit breaker. Typically, such devices P are placed at the level of the source, at the level of the load, or most commonly, at the level of the grid node via the distribution equipment E1, such as Figure 1b shown.

[0075] The detection device D and the protection device P can be freely distributed within the power grid 1, depending on their characteristics and topology, to ensure protection of the power grid 1. One or both of these devices D and P can be located at the end of a line L, on a portion of a line L, or integrated into an electrical device E. The detection device D and the protection device P do not necessarily need to be associated with each other, but in some cases (e.g., in the same situation), it may be advantageous to associate the detection device D and the protection device P so that a single module can perform both detection and protection functions. In this case, the detection terminal of the detection device D can be connected to the trigger terminal of the protection device P. When a fault is detected, a detection signal S is generated at the detection terminal.

[0076] Some sections of the grid 1, line L, or equipment E may not be equipped with detection devices D and / or protection devices P. In this case, a fault occurring in this section of the grid 1 may not be detected or located, and / or disconnecting this section of the grid 1 may not be possible. However, the occurrence of a fault can be detected by means of detection devices D arranged outside the section where the fault occurred, and the entire grid 1 can be protected, for example, by disconnecting the grid 1 from the equipment E forming the energy source. To this end, as will be explained in detail in the remainder of this specification, energy changes can be measured directly at the output of the source or directly at the input of the load. When detection devices D are placed at the source output and the load input, respectively, they are preferably placed as far upstream and as far downstream as possible, respectively, so that defects in the protection device P or the connection terminal B can also be detected.

[0077] As will become apparent in the remainder of this description, according to the grid energy E net , residual energy E res and / or mixed energy E mix The unique measurement of the power supply voltage (V) allows for the local detection of certain types of faults in that area. This is particularly true in the case of series arcs, insulation defects, or excessive consumption. The detection device D is then adapted to generate an electrical signal S at its detection terminals, indicating the presence of a fault in the grid 1. When the detection device D is locally associated with a protection device P, this signal S can be used locally by the protection device P to immediately isolate the faulty grid section, line L, or equipment E from the rest of the grid 1.

[0078] In order to detect other types of faults, such as an arc between two parallel conductors, to locate the fault more precisely in the network 1, or to quantify the fault in terms of the consumed energy, it may sometimes be necessary to use the energy measurements E provided by a plurality of detection devices D. net 、E res 、E mix . To this end, according to a particular embodiment of the invention, provision is made for the power grid 1 to be associated with a monitoring device V. This device V is generally implemented by digital computing means, connected to at least some detection devices D of the power grid 1 via a communication bus BUS, as indicated by the dotted line in FIG1 . Any type of bus may be suitable for implementing the communication bus BUS, the communication bus BUS including in particular a serial bus or a parallel bus operating in any possible protocol form, whether or not it complies with established standards. It should be noted that the monitoring device V may be integrated into one detection device D. In this case, provision may be made for these devices D to include computing means such that these devices D are suitable for implementing monitoring processes, and then at least one of these detection devices may be activated to operate as a monitoring device V of the power grid 1.

[0079] The power grid 1 is equipped with a plurality of detection devices D coupled to a monitoring device V, these devices being configured to place data on the communication bus BUS indicating the occurrence of a fault and / or representing the energy E measured during a given observation period. net 、E res 、E mix On the computer network formed by the communication bus BUS, the detection device D is identified by a unique identifier. The communication bus BUS includes clock information assigned to each detection device D so that each detection device D shares a common time base. Data E j net,i 、E j res,i 、E j mix,irepresents the energy measured by the identification device i and placed on the communication bus BUS during a determined observation period j, and thus the data E can be monitored by the monitoring device V j net,i 、E j res,i 、E j mix,i Sorting and processing are performed to determine the grid state at a given moment, i.e. the grid energy delivered, the residual energy, the mixed energy in each measurement area within a given observation period.

[0080] Figure 2 1 at the instant of an observation period j, when the observation period j can be created by the monitoring device V. Here, each detector D1, D2, D3, D4 of the network is identified by an index corresponding in a simplified manner to the identifier of the detector on the computer network. Each detector measures its mixed energy E j mix,i (and its absence Figure 2 Other measured values ​​E shown in j net,i 、E j res,i ) is placed on the communication bus BUS so that the monitoring device V can send the data structure of the power grid status. Figure 2 The data structure is represented by the energy level table T transmitted in each measurement area. The data structure can record the grid energy, residual energy and mixed energy of each measurement area in a table indexed by observation period j. Figure 2 ) can be advantageously placed at the level of a distribution "node", for example in a distribution device of the network 1, such as Figure 1b shown.

[0081] The monitoring device V is configured to use data provided by the detection device D of the network 1 and transmitted by the communication bus BUS. The purpose of this use is to detect faults in the network and / or to localize the fault in the network 1 and / or to quantify the detected fault in terms of energy.

[0082] The monitoring device V can emit a signal indicating a fault in the power grid 1, and this signal can be used to disconnect a portion of the power grid. To this end, the monitoring device V can be connected to at least some of the protection devices P in the power grid 1 to activate them where appropriate. This can be a point-to-point connection, or a connection via a communication bus (BUS) or another dedicated bus, to which the protection devices P are then connected. In another embodiment, particularly when the monitoring device is integrated into a detector D in the power grid, the monitoring device can communicate with a third-party device responsible for controlling the protection devices P in the power grid.

[0083] Therefore, it should be understood that according to Figure 1a and Figure 1b In the embodiment of the invention shown, at the level of the measurement area there is an electrical network 1 and a plurality of detection devices D distributed on the electrical network 1, which transmit data E to a monitoring device V. j net,i 、E j res,i 、E j mix,i , data E j net,i 、E j res,i 、E j mix,i represents the energy transferred in these measurement areas i during a determined observation period j. The monitoring device V can use this data to represent the state of the power grid, ie the energy transferred in each measurement area during consecutive observation periods.

[0084] Energy data or data representing energy variations above a certain threshold can detect a fault, but not necessarily locate the fault (except at the level of the end of the grid, where energy variations can locate defects). On the other hand, analyzing the difference in energy transmitted between two (or more) detection devices D can not only improve the quality of detection, but also locate the fault between the two detection devices (D). To this end, the monitoring device V can be configured to use the information provided by the detection devices D on the communication bus BUS to locate a fault occurring in the grid 1, including a portion of the conductors C1, C2, Cc between the two devices, or a fault occurring in an equipment E of the grid. Thus, if Figure 9 As shown, a system for locating faults in an electrical network is made usable by equipping the system for locating faults in an electrical network with at least two detection devices D.

[0085] Thus, the monitoring device V is suitable for detecting and / or localizing and / or quantifying faults occurring on the electrical network 1 in order to protect the electrical network 1 , for example by disconnecting the localized faulted portion of the electrical network 1 .

[0086] Common conductor

[0087] To distinguish between different forms of energy transmitted by the power grid 1 formed by power conductors (over which energy is transmitted), the present invention provides for the power grid 1 to be equipped with a common conductor. This common conductor forms a reference voltage for all electrical devices E in the power grid electrically connected to the common conductor. The common conductor can be a mechanical mass of the power grid or it can be neutral, but this is not necessarily the case. The common conductor is not intended to carry high currents, but it can be at a higher potential relative to the mechanical mass. The common conductor can be a simple telecommunications cable, such as a cable that at least partially constitutes the aforementioned communication bus BUS. Alternatively, the common conductor can be a conductor similar to that forming the power conductor. When the "source" or "load" type device E is symmetrical, the common conductor can be connected to the midpoint connection terminal of the "source" or "load" type device E (for example, the midpoint of two midpoint batteries or inverters, or the midpoint of a photovoltaic panel). The common conductor can be connected to the existing midpoint of the device, source or load, or to a midpoint "created" from a resistive divider on the source and / or load side. This dividing bridge allowing the connection of the common conductor can be integrated into the detection device D.

[0088] In a bipolar configuration (single-phase converted AC grid or DC grid), line L is thus composed of a first power conductor and a second power conductor, to which a common conductor is added. In a three-phase configuration, line L includes a third power conductor, which can be connected to the neutral point. For the sake of simplicity, we will hereinafter consider grid 1 to be a bipolar grid comprising two power conductors, to which a common conductor is added, but the principles described are generally applicable to grids comprising any number of power conductors.

[0089] Definitions of grid energy, surplus energy, and mixed energy

[0090] To illustrate the benefits of common conductors in the detection of faults in the grid, Figure 3 By way of illustration a portion of an electrical network is shown, this portion comprising a line L arranged between a source S and a load C. The line L is constituted by a first power conductor C1 , a second power conductor C2 and a common conductor Cc.

[0091] As can be seen from these figures, the current I 1s , I 2s , I 1c , I 2c It is defined as the current flowing in the first power conductor C1 and the second power conductor C2 on the source S side and the load C side respectively. In the same way, we define the voltage V 1s 、V 2s 、V 1c 、V 2cThe potential differences exist between the common conductor Cc and the first power conductor C1 and the second power conductor C2 on the source S side and the load C side, respectively.

[0092] It should be noted that the voltages and currents mentioned in the rest of this specification are essentially time-varying, i.e., voltages and currents are expressed in the form of V(t) and I(t). However, to simplify writing, we will designate these variable currents and voltages as V and I.

[0093] refer to Figure 3 , the grid voltage V on the source side and the load side net,s 、V net,c As the differential mode voltage between the two power conductors C1 and C2: V net,s =V 1s -V 2s and V net,c =V 1c -V 2c Similarly, we take the grid current I on the source side and the load side net,s , I net,c Defined as the differential mode current flowing on the two power conductors C1 and C2: I net,s =1 / 2*(I 1s -I 2s ) and I net,c =1 / 2*(I 1c -I 2c ). Naturally, the grid energy E in a certain observation period net Corresponding to the product I net *V net The grid energy can create E on the source side. net,s and create E on the load side net,c .

[0094] when Figure 3 When the grid part in the circuit is in normal operation and completely balanced, the grid voltage V on both sides of line L is net,s 、V net,c Same as the grid current I net,s , I net,c Therefore, in addition to the losses dissipated in the line, the grid energy E on the source side net,s and the grid energy E on the load side net,c Also identical to each other.

[0095] The occurrence of a grid fault causes grid imbalance, which can be measured by measuring the residual voltage V res,s 、V res,c To determine this imbalance, the residual voltage V res,s 、V res,c On the source side, the common-mode voltage V res,s=1 / 2*(V 1s +V 2s ) and on the load side by the common-mode voltage V res,c =1 / 2*(V 1c +V 2c ) is defined. Similarly, we can measure the residual current I res,s , I res,c , residual current I res,s , I res,c On the source side, the common mode current I res,s =I 1s +I 2s is defined by the common mode current I res,c =I 1c +I 2c Of course, the remaining energy E in a certain observation period res Corresponding to the product I res *V res The remaining energy can be used to create E res,s and create E on the load side res,c .

[0096] Finally, we will also mix the energy E within a certain observation period mix Defined as the product I net *V res The integration over this period. This mixed energy can create E on the source side mix,s and create E on the load side mix,c .

[0097] As mentioned above, when Figure 3 When the grid is completely balanced, the residual voltage and residual current are zero. The residual energy E on the source side res,s and mixed energy E mix,s And the remaining energy E on the load side res,c and mixed energy E mix,c Also zero.

[0098] Parallel type faults between power conductors (parallel arcs)

[0099] refer to Figure 4a , Figure 3 A fault of parallel type between two power conductors C1 , C2 of a line of the grid shown can be modeled as a dipole DP1 placed between these two conductors C1 , C2. The grid voltage V on the source side net,s and the grid voltage V on the load side net,c The difference between them is not affected by the presence of the dipole, but the current circulates in the dipole DP1 between the power conductors C1 and C2, which will cause the grid current I on both sides of the line net,s , I net,cAn imbalance occurs, that is, the grid current I net,s , I net,c No longer the same.

[0100] In the event of a fault of this parallel type occurring between the two power conductors C1 , C2 , there is no residual current or residual voltage.

[0101] A fault of the parallel type (for example a parallel arc) between two power conductors C1, C2 manifests itself as a current I on both sides of the line during a certain observation period. net,s , I net,c and / or grid energy E net,s 、E net,c We note that in the case of this parallel arc, the energy dissipated in the dipole DP1 that models this parallel arc is much higher than the nominal power of the grid, so that the current I net,s , I net,c and / or grid energy E net,s 、E net,c The difference in ∆ can clearly detect the fault.

[0102] In fact, in Figure 2 In the power grid, the power grid energy E j net,i 、E j net,i+1 The difference between the power grid energy threshold S i,i+1 Compare to detect that in time period j, when two detection devices D are connected i 、D i+1 A parallel fault occurs between two power conductors C1 and C2 (whose identifiers are i and i+1 respectively), and the grid energy E j net,i 、E j net,i+1 By the detection device D i 、D i+1 Provided via the communication bus BUS. Current I j net,i and I j net,i+1 The difference between the current I j net,i and I j net,i+1 By the detection device D i 、D i+1This is provided via the communication bus BUS. Provision can be made for the monitoring device V to be configured to perform other types of processing on the supplied grid energy to detect the occurrence of this type of fault. For example, the energy supplied over several consecutive observation periods can be summed, the difference then compared with a threshold value to extend the observation period. This allows the triggering time to be adjusted according to the power of the fault: a very high-power fault will cause the monitoring device V to react much faster than a low-power defect. This also ensures that protection is not triggered in the event of a non-persistent transient fault.

[0103] Generally speaking, the trigger threshold S i,i+1 Associated with two detectors with indexes i and i+1, the trigger threshold S i,i+1 According to the characteristics of the equipment E of the power grid 1, the equipment E can be located in two detection devices D i 、D i+1 to take into account, for example, losses in lines or connectors, or even the consumption of a device E with a parallel characteristic and a known maximum power that is lower than the characteristic power of the fault.

[0104] A parallel type fault (insulation defect) between a power conductor and an external component.

[0105] refer to Figure 4b A fault of the parallel type between one of the power conductors C1, C2 and an element external to the grid can be modeled as a dipole DP2 placed between this conductor and the external element. The external element can be the common conductor Cc, the mechanical mass of the grid or any other potential.

[0106] The grid voltage V that appears on the source side net,s and the grid voltage V that appears on the load side net,c The occurrence of this type of fault is not necessarily affected, as it depends on the grounding scheme maintained for the grid. In the case of a primary fault, known as the "IT state"—that is, when the grid is isolated from ground or mechanical mass—there is little impact on grid energy, residual energy, and mixed energy. However, to identify the occurrence of this type of fault in this type of grid, a permanent insulation controller can be used, as described in more detail below. On the other hand, if an insulation defect occurs in a non-isolated grid or a secondary fault occurs in an isolated grid, significant differences in grid energy, residual energy, and mixed energy can occur.

[0107] Then, the current flows in the dipole DP2 between the power conductor and the external element. Therefore, on the source S side and / or the load C side, the current flowing on the power conductor is different from the current flowing on the other conductor. This difference causes a residual current I on the source side. res,s and / or cause residual current I on the load side res,cThe current flowing through the dipole DP2 forms a potential difference, which also affects the voltage of the power conductor and causes a residual voltage V on the source side. res,s and causes a residual voltage V on the load side res,c .

[0108] Therefore, during a determined observation period, the occurrence of an insulation defect will cause a residual energy E on one side or the other of the line. res,s or E res,c In the case of non-real defects, the variation of residual energy will be more sensitive than the variation of grid energy.

[0109] During a period j, the residual energy E is measured in a measuring area of ​​the grid and by means of a detection device D (identifier i) arranged in this area. j res,i , so, for example, by dividing the measured residual energy E j res,i Comparison with a defined threshold value Si allows the occurrence of such a fault to be detected. This detection can be performed locally, without having to call the network monitoring device V and without having to transmit the energy measurement values ​​to it. As explained above, this local detection enables the activation of a local protection device P in order to isolate a portion of the network 1.

[0110] This insulation fault can result in residual energy that is significantly lower than the nominal energy of the grid. Furthermore, natural asymmetries can generate deviations in the local calculation of the residual energy (for example, if the voltage of the common conductor Cc is not exactly half the grid voltage). The detection and location of this fault is then facilitated by using two detection devices D to obtain the difference between these energies measured upstream and downstream of the line. The residual energy measurement is then transmitted to the monitoring device V, utilizing its processing capabilities, as described in the previous case.

[0111] In other cases, the residual energy may be relatively small, and it may then be advantageous to sum the residual energies measured over several consecutive observation periods and then compare with the threshold value in order to extend the observation period.

[0112] In the case of an insulated grid (IT state type), if a first insulation defect occurs, the grid will be able to continue to operate fully, and a permanent insulation controller (PIC) must be present to detect the first defect. This PIC measures the impedance between the grid and a mechanical mass or ground. To this end, the PIC usually injects a common-mode voltage (residual voltage) into the grid at a very low frequency (typically 1 Hz). When the grid is healthy, there is no common-mode current (residual current) and therefore no residual energy. If a first insulation defect occurs, the PIC will cause residual current and residual energy to occur, in particular at the excitation frequency of the PIC. Therefore, it is advantageous to measure the residual energy only at the excitation frequency of the PIC in order to facilitate the location of the insulation defect. To this end, the PIC and the detection device D must be synchronized, for example by sending a synchronous clock on the communication bus BUS.

[0113] Series type faults (series arcs)

[0114] refer to Figure 4c , a series type fault, such as a series arc occurring on a line L, most often occurs on the connection terminal B, and sometimes occurs in the power conductors C1, C2. The series type fault can be modeled as a dipole DP3 placed in series on the conductor.

[0115] Grid current I on the source side net,s and the grid current I on the load side net,c It is almost unaffected by the presence of the dipole DP3. However, the current flowing in the dipole DP3 will cause the voltage V d , voltage V d This causes the voltage on one power conductor to be unbalanced, while the other conductor is unaffected. This dispersion will cause a residual voltage V on the source side. res,s and causes a residual voltage V on the load side res,c .

[0116] Therefore, within a certain observation period, the occurrence of a series defect will cause a mixing energy E on one side and / or the other side of the line. mix,s or E mix,c Series defects also cause changes in grid energy, but these changes are much lower than the nominal energy, so it is not possible to reliably detect series defects at an early stage by analyzing grid energy. On the other hand, series defects do not cause any changes in residual energy.

[0117] During a period j, the mixed energy E is measured in a measuring area of ​​the grid and by means of a detection device D (identifier i) arranged in this area. j mix,i , so, for example, by converting the measured energy E j max,iThe occurrence of such a fault can be detected by comparison with a defined threshold value Si. This detection can be performed locally, without having to call the monitoring device V of the power grid and without having to transmit the measured values ​​to it. As explained above, this local detection can activate a local protection device P in order to isolate a portion of the power grid. It is also possible to use the residual voltage V provided by the detection devices Di, Di+1 via the communication bus BUS. j res,i and V j res,i+1 to detect and locate series type defects.

[0118] We note that the mixing energy E mix The asymmetry between the first and second power conductors is caused by the presence of series dipole DP3, which models a series-type fault. Therefore, to fully exploit the mixed energy detection capabilities, intentional asymmetry of the power conductors C1 and C2 should be avoided. For this reason, one of the two power conductors should not be confused with the mechanical mass of the grid. It is also important to avoid inserting a connector or any other component into only one of the power conductors in line L.

[0119] In the case of "natural" asymmetries in the electrical network, which generate mixed energies in some measurement areas, even during normal operation of the electrical network, this mixed balance energy can be determined and taken into account for fault detection, for example by adjusting the level of a comparison threshold Si or by identifying temporal variations in the mixed energy. Thus, a calibration phase can be provided for the detection device D (or monitoring device V) of the electrical network 1, the purpose of which is to enter a threshold level, the exceeding of which by the measured value of the mixed energy or residual voltage indicates the occurrence of a series type fault. Typically, as an example, a series arc generates a residual voltage between 20 V and 50 V. We can then choose a threshold value for detecting the residual voltage difference close to 2 V, while the threshold value for detecting the mixed energy difference is 2 V multiplied by the current I net Therefore, advantageously, the detection threshold Si can be made according to the grid current I net varies with the average value.

[0120] As with the two types of faults described above, the measured values ​​of the mixed energy prepared by each detection device D can also be provided to the monitoring device V, and then by analyzing the difference in the mixed energy between the two detection devices Di and Di+1, series type defects can be detected and located more accurately. The consecutive energy measurements can also be processed by summing or differencing, in particular to enable the detection of low-power defects over a longer observation period. The detection thresholds applied to the measurement of grid energy, residual energy and mixed energy, respectively, can be different from each other, or the detection thresholds applied to the difference of these energies between the two devices can be different from each other. According to convention and the characteristics of the defect (for example, a series arc on the first power conductor C1 or a series arc on the second power conductor C2), it is clear that these thresholds can be negative and the concept of energy "above" a threshold is understood as an absolute value.

[0121] To summarize the description of this section, we note that the grid energy E is measured in a certain grid area during a certain observation period. net , residual energy E res and mixed energy E mix , it is possible to detect and localize the occurrence of various faults. This detection can be performed locally within a measurement area by simply observing whether the grid energy, residual energy, and mixed energy exceed certain thresholds. More precise localization of these faults, as well as detection of a wider range of faults, may require the use of measured values ​​of these energies between two measurement areas of the grid 1.

[0122] In particular, the measurement of mixed energy at the level of a single measurement area can be used to detect the occurrence of series faults, such as arcs in conductors of a device (e.g., a source) or a line of a power grid, which is not easily achievable using the techniques known in the prior art. This aspect is therefore an important advantage of the solution described herein.

[0123] To facilitate this detection, the lines L of the power grid 1 are advantageously designed to be as symmetrical as possible. In this regard, it is advantageous to select the power conductors connecting the electrical devices E to one another so that they are identical or have the same geometry (diameter and properties of the conductors and insulation). It can also be provided that the power conductors and the common conductor are assembled parallel to one another, for example to form a cable bundle by bundling them, or even to form a single cable, for example by embedding the conductors in insulating material. This limits asymmetries in the interaction of the conductors with the environment.

[0124] For the same reason of seeking balance, and in order to make the residual voltage zero in the absence of defects, the common conductor can be connected to the midpoint of the electrical device forming the source or load. We can equip an electrical device E forming the source or load without a midpoint, equip it with a resistance bridge between the two power conductors, and connect the common conductor to the midpoint of this resistance bridge.

[0125] To enable the measurement of grid energy, residual energy, and mixed energy, the fault detector D is equipped with voltage and current sensors, which can form an image of the voltage carried by the conductor in the measurement area, or the voltage flowing in the conductor connected to these sensors. Advantageously, these sensors have good linearity and are less affected by environmental factors (temperature, mechanical constraints, etc.), so as not to bias the energy calculation between two remote points in the grid. They are also less sensitive to aging. These sensors also have a wide measurement passband, allowing the measured energy to take into account spectral differences in the signals (grid voltage and current), especially during fault conditions.

[0126] Generally speaking, these sensors are suitable for implementing reliable measurements in the frequency range between 0 Hz and 1 kHz, or even between 0 Hz and 10 kHz or 100 kHz, or even between 0 Hz and 1 MHz or 10 MHz or 100 MHz. Each of the measuring members O1 and O2 may comprise one or more such sensors. In particular, they may comprise sensors operating in different frequency ranges. Thus, it is conceivable that the measuring members O1 and O2 may comprise sensors capable of measuring the DC component of a signal and / or sensors capable of measuring certain non-DC spectral components of a signal.

[0127] Advantageously, the sensors are adapted to provide measurements of the DC component of the current or voltage of the power grid 1, whether the power grid 1 is an AC or DC power grid, with a response time compatible with the required detection delay (e.g., less than or equal to one millisecond). Consequently, the measurement passband of these sensors is typically between 0 Hz and 1 kHz, or between 0 Hz and several kHz. The energy measured within this frequency range is sufficient to detect most faults, particularly series or parallel arcs, with the required response capability.

[0128] In the case of an AC power grid with active electrical equipment, sources, or loads, the energy determined by measuring the DC components of the current and voltage can demonstrate a fault in the operation of the equipment. It can also protect power transformers from magnetic saturation caused by these DC components. In the case of an AC power grid with an IT-type (isolated) grounding scheme, the measurement of the DC component can also locate the first defect as described above.

[0129] The sensor can also be used to provide precise measurements of voltage and current at grid frequency to detect over-consumption faults or insulation defects. The sensor can also operate at higher frequencies, in the very high frequency range exceeding 100 MHz. This makes it particularly useful for detecting partial discharge-type defects in the insulation of grid conductors.

[0130] Detection device

[0131] Having stated the basic principle of the present invention, the detection device D according to the present invention is now described in detail. Figure 5 As already described with reference to FIG1 , this detection device D is suitable for connection to the power conductors C1, C2 and common conductor Cc of the power grid 1, and is connected at the level of the measurement area of ​​this power grid 1. These power conductors can be those forming the lines L of the power grid 1, or preferably, those within the electrical equipment E of the power grid. In this case, the measuring members O1, O2 of the detection device D are preferably placed upstream of the terminals B of the distribution lines L connecting sources to the power grid, and preferably downstream of the terminals B connecting loads to these lines L. In this way, defects in these terminals B can be detected and located.

[0132] In the simplest version of the detection device, the detection device D is designed to detect at least series type faults and is therefore configured to describe in detail the amount of mixed energy transmitted in the measurement area and during a given observation period.

[0133] To this end, the detection device D comprises a first measuring member O1 coupled to at least some of the conductors so as to be able to establish a first quantity V representative of the common mode voltage (ie the residual voltage) of the power conductors C1, C2. res Thus, the first member O1 may comprise a sensor of the voltage present on each of the power conductors C1 , C2 , with respect to the common conductor Cc. In the following part of this description, several preferred embodiments of this first member O1 will be given.

[0134] The detection device D also comprises second measuring means O2 coupled to at least some of the conductors so as to be able to establish a second quantity I representative of the grid current. net As an example, the second component O2 may include a first current sensor for measuring the current flowing on the first power conductor C1 and a second current sensor for measuring the current flowing on the second power conductor C2, the difference between the measured values ​​provided by these sensors representing the second quantity I net In some cases, a single current sensor may be provided to measure a quantity on only one of these conductors, which quantity is understood to be the grid current and thus the second quantity I net A first approximation of .

[0135] Advantageously, the one or more current sensors of the second measuring member are Hall effect sensors, Neel effect sensors A sensor, or a sensor including a resistive shunt, is used to extract the DC component of the measured current. Provision can be made for the one or more current sensors of the second component to include a Rogowski-type sensor or an air transformer. These types of sensors offer extended passbands, linearity, and stability, and can be used to measure non-DC spectral components. This is particularly true when investigating partial discharge defects.

[0136] Whatever the nature of the components used to implement the first and second measuring means O1 and O2, they are capable of determining, directly or indirectly (i.e. with the aid of a calculator UP to be described hereinafter), a quantity I representative of the grid current. net and the residual voltage V res In the measurement area of ​​the detection device D, defined by its location in the grid, these two quantities are able to create a mixed energy E transmitted within a determined observation period mix To this end, the detection device D further comprises a calculator UP connected to the first and second measuring members O1 and O2. The calculator UP may take any suitable form, but preferably, the calculator UP is a digital calculator whose inputs are capable of digitizing the analog measurement values ​​provided by the measuring members O1 and O2 at a high frequency. The calculator may be implemented by a microcontroller, an FPGA, a DSP, an ASIC, or any other suitable digital or analog computing device.

[0137] Alternatively, the detection device D may comprise a converter CON, such as Figure 5 As shown by the dashed lines in FIG, the converter CON is suitable for drawing energy from the power connectors C1, C2 and / or the common connector Cc to power the calculator UP and all other active components constituting the device D. It will be understood that this reduces the power required. When the detection device D is designed to be connected to a communication bus BUS, as shown in FIG1 , the detection device D can alternatively be powered by a dedicated port of this bus.

[0138] For the sake of completeness, but not as an essential feature, the detection device may also comprise a network controller NET, which may be implemented by a computer UP and which is capable of connecting the device D to the communication bus BUS. The device D is associated with an identifier (for example a network address) which makes it possible to identify the device D on the network. The bus BUS allows clock information to be transmitted to the computer UP, or the device D may have a dedicated clock terminal capable of receiving this information. In this way, the computer UP can time-stamp the data specified, which are then placed on the communication bus BUS. In this way, as we have seen, Figure 5Several detection devices D similar to the one shown are connected to a monitoring device V which can sort the data received from these devices D and use them in a temporally coherent sequence.

[0139] The calculator UP of the detection device D is configured by hardware or software to acquire the measurement values ​​provided by the first measuring member O1 and the second measuring member O2 and to determine the mixed energy E transmitted in the measurement area during a given time period j. j mix The frequency with which the computer acquires the measurements is typically less than one millisecond, for example, it may be approximately 100 microseconds or 10 microseconds, or even 100 ns or less, depending on the passband of the measuring members O1, O2. The observation period may be between 100 ns and 10 s. It is provided that the computer UP may be configured to digitally process the measurements provided by the measuring members O1, O2, or that the computer UP may be configured to combine a plurality of measurements provided by each of these members O1, O2 in order to determine the mixed energy E j mix For example, when the sensors of components O1 and O2 provide information proportional to the time derivative, the calculator can be configured to integrate the provided measurements. When one of the two measuring components O1 and / or O2 independently provides a DC current / voltage measurement and a measurement of the change in this current / voltage, the calculator can be configured to add these two measurements (after integrating them).

[0140] The calculator UP can also be configured to use the determined mixing energy E j mix , to detect series type faults in the power grid, as discussed in the previous part of this specification. Specifically, the determined mixed energy E j mix Or whether the energy varies between two different observation periods by more than a predetermined threshold. As we have seen, the calculator can be configured to calculate the determined mixed energy E in successive observation periods j, j+1, ..., j+n. j mix 、E j+1 mix ...、E j+n mix The accumulated mixed energy is then compared with a threshold to determine the occurrence of a fault.

[0141] When such a fault is identified, the calculator uses one or more mixed energy measurements E in any way. j mix, the calculator UP can generate a signal S indicating the fault, which can be transmitted to the detection terminal of the device D. In the case of using the detection device D, it should be understood that the communication bus BUS is not necessarily present. Alternatively, the signal S can be placed on the communication bus BUS. Alternatively, the calculator UP can simply calculate to formulate a value representing the mixed energy E j mix and places the data on the communication bus BUS. In this last alternative, the detection of the fault in the power grid is completely realized by the monitoring device V as described above.

[0142] In a more complete embodiment of the detection device D, the detection device D may comprise other measuring members, or more completely, may comprise a first measuring member O1 and a second measuring member O2, so that the calculator UP is able to determine the mixing energy E in addition to the mixing energy E j mix In addition to the image of , it is also possible to determine the grid energy E transmitted in the measurement area within a certain observation period j j net The image and the remaining energy E j res In addition to the second quantity I representing the grid current net and a first quantity representing the residual voltage V res In addition, these components can create a third quantity V representing the grid voltage net and a fourth quantity I representing the residual current res This more complete embodiment can be obtained by Figure 5 The dotted arrow V in net and I res represent.

[0143] Detection device integrated in active equipment

[0144] The detection device D can be integrated into an electrical device E that includes a load or an active source, such as an inverter or generator, whose correct operation is to be monitored. In this case, to detect series arcs, the detection device D is positioned as close as possible to the active parts of the device E, namely, just before the power switch, downstream of the device's connection terminal B, and, if the device E is a load, downstream of any protective device P. Preferably, a resistive voltage divider bridge is placed between the power conductors C1 and C2, with its midpoint connected to the common conductor closest to the active load. This allows for the measurement of mixed energy, i.e., the presence of a series defect in the internal conductors of the monitored device E.

[0145] In the same way that we try to differentiate the energy in the grid, we can try to differentiate the energy consumed by the loads. To do this, we can define 4 types of energy:

[0146] The energy called “useful energy” is characterized by the current-voltage spectrum, which is between 0 and 10 Hz for a DC grid and ±5 Hz for an AC grid, at the grid frequency.

[0147] Harmonic distortion energy, which is characterized by a current-voltage spectrum that lies within a frequency band of multiples of the grid frequency ±5 Hz (for AC grids). This energy is reactive in nature.

[0148] The switching energy is characterized by the current-voltage spectrum, which has frequencies that are multiples of the chopping frequency FHACH of the active load. This energy is limited to a frequency band of these multiples of n*FHACH ± 5 Hz.

[0149] Additional energy that does not lie within any of the above mentioned frequency bands. In case of an arc (series arc or parallel arc) or a short circuit, only a priori noise or energy is found in this frequency band.

[0150] As described in the previous part of this description, the detection device D integrated in the device E will create the grid energy E net , residual energy E res and mixed energy E mix , in order to transmit this information, for example, to the monitoring device V. Furthermore, the detection device D is capable of decomposing these energies according to the four categories mentioned above in order to identify the contributing terms. To this end, the detection device D can apply a filter to the quantities provided by the measuring members O1, O2 in order to separate these quantities according to the various frequency bands described, and then calculate the energy in each frequency band with the aid of a calculator UP.

[0151] This filtering can be implemented as a comb filter implemented by the calculator UP, so that the frequency of the comb filter can be constrained in particular by the chopping frequency. For this purpose, it can be provided that the chopping frequency is provided in the form of a chopping clock FHACH generated by the active load and displayed on a dedicated connection terminal of the detection device (e.g. Figure 5 shown).

[0152] Therefore, we can create with the calculator UP:

[0153] -Grid energy "useful E net ” as useful energy in a load or source. This energy can manifest as an overload or parallel arc.

[0154] -Grid Energy "Switch E net ” as the energy lost in the switching structure of the electrical device E. This energy may indicate a switching fault, such as a short circuit in an arm (not taking into account dead time) or switch fatigue.

[0155] -Grid Energy "Additional E net " as additional energy due, for example, to parallel or series arcs or short circuits.

[0156] - Hybrid Energy "Switch E mix ", which is more efficient than using only the mixed energy E mix The switching fault can be represented in a more refined way. Specifically, the switching fault can be represented by the mixing energy E mix The existence of a series arc in device E is identified by eliminating the switching mixing energy.

[0157] This energy can be placed on the communication bus BUS and transmitted to the monitoring device V in order to be used.

[0158] Preferred embodiments of the first measuring member

[0159] In order to ensure the detection and location of faults, in particular series arcs in AC or DC grids, as we have seen, the residual voltage V is measured. res and grid current I net These measurements are performed by the first measuring member O1 and the second measuring member O2 of the detection device D, respectively.

[0160] To measure the DC component of the common-mode voltage, that is, the residual voltage V res The first measuring member O1 may be equipped with a resistive voltage divider bridge, with a first electrode T1 electrically connected to the first power conductor C1, a second electrode T2 electrically connected to the second power conductor C2, and a third electrode T3 electrically connected to the bridge's midpoint. The common-mode voltage is provided by a voltage formed by a measuring dipole SH between this midpoint associated with the third electrode T3 and the common conductor CC. Typically, this dipole is formed by a resistor. Figure 10 The schematic diagram of such a bridge is shown, in which the resistors R1, R2 forming the bridge are precisely chosen to have the same value (within 1%, or even within 0.1%, or even within 0.01%) and the drift of the resistors R1, R2 over time and temperature is limited to a minimum. In this solution, the quantity V representing the common-mode voltage res = is equal to the common-mode voltage present on the two power conductors multiplied by a gain equal to SH / [R1 / 2+SH]. This gain makes it possible to reduce the dynamic range of the measured value to adapt it to the dynamic range of the electronics of the measuring means. As an illustration, by choosing R1=1MΩ and SH=50kΩ, a gain equal to 1 / 11 makes it possible to reduce a common-mode voltage of 50V on the power conductors to a value representing approximately 5V, V res The values ​​of resistors R1, R2 and SH should be chosen to adapt to the number of grids and the dynamics of the measurement electronics.

[0161] As already mentioned, the detection device D is equipped with connection terminals B for associating the device with the conductors C1 , C2 , CC. These terminals B are therefore also electrically connected to the electrodes of the resistance bridge.

[0162] For example, a resistor divider bridge can be composed of thin-layer (or thin-film) resistors or thick-layer (or thick-film) resistors, ensuring sufficient voltage tolerance and controlling the transformation ratio without causing thermal or time drift. To ensure perfect symmetry between the two resistor elements R1 and R2, thereby reducing drift over time and temperature, these resistor elements are formed using a resistor divider called a "three-terminal unit" voltage divider.

[0163] When choosing to measure the non-DC component of the residual voltage, it is preferred that the sensor performing this measurement is insensitive to possible DC components, is completely linear, has a controlled gain and does not drift with temperature or time. This is especially true for partial discharge type defect detection. Figure 6 In the preferred embodiment shown in the schematic diagram, two capacitive elements EC1 and EC2 are arranged in a bridge between two power conductors C1 and C2. The capacitance values ​​of these two capacitive elements EC1 and EC2 are substantially identical, with a deviation within 1%, or even within 0.1%, or even within 0.01%. These elements are connected at a midpoint M. The midpoint M is electrically connected to the common conductor Cc via a common-mode voltage measurement dipole SH.

[0164] The currents I1 and I2 flowing in the capacitor elements EC1 and EC2 are respectively related to the potential V carried by the power conductors C1 and C2. c1 、V c2 The capacitance elements EC1 and EC2 have the same capacitance value, and the differential current I1-I2 is proportional to V c1 +V c2 (i.e., common-mode voltage V res ) is proportional to the derivative of the current. Thus, it is sufficient to measure this differential current I1-I2, for example by means of a current sensor arranged in the branch of the circuit connecting the midpoint M between the capacitive elements and the common conductor Cc, and then to integrate this differential current I1-I2 as a function of time to obtain the residual voltage V res For this purpose, the measuring dipole SH placed between the midpoint M and the common conductor Cc is part of a current sensor having a low impedance of less than 1 kΩ or even less than 1Ω. Figure 6 As shown, the integration does not necessarily have to be performed similarly in the first measuring member, the calculator UP can be configured to perform this operation.

[0165] Alternatively, the common mode voltage V between the midpoint M and the common conductor Ccres The non-DC component of the current can be directly measured by selecting a high-impedance measuring dipole SH, greater than 1 kΩ or even greater than 1 MΩ. Component O1 then comprises a capacitive voltage divider that transfers the remaining voltage relative to the common conductor Cc. This second solution is less suitable for harsh electromagnetic environments (e.g., in aircraft), but it can be used in photovoltaic power plants to supplement the DC component.

[0166] In order to ensure perfect symmetry between the two capacitive elements EC1 , EC2 , and thus reduce drifts over time and temperature, capacitors known as “three-terminal unit capacitors” are used to form these capacitive elements.

[0167] This type of capacitor includes A-type electrodes, B-type electrodes and G-type electrodes ( Figure 7 ), each type of electrode is electrically associated with a terminal unit, and each type of electrode is stacked on top of each other and insulated from each other by a dielectric, following an alternating pattern of A, G, B, G, A, G, B, and so on. The capacitor's electrode G is directly connected to the midpoint M, which is connected to the common conductor Cc via the measuring dipole SH. The A-type electrode and the B-type electrode are connected to the power conductors C1 and C2, respectively, via the capacitor's three terminal units. The advantage of this structure is that the capacitance elements EC1 and EC2 are almost identical. On the one hand, the capacitance elements EC1 and EC2 between the G-type terminal unit and the A-type terminal unit are time-invariant and temperature-stable, and on the other hand, the capacitance elements EC1 and EC2 between the G-type terminal unit and the B-type terminal unit are time-invariant and temperature-stable. The three-terminal unit capacitor also has very low parasitic inductance, which enables measurements at very high frequencies.

[0168] The dielectric of the capacitor can be of C0G type or NPO type. Capacitors can also use a paper-based dielectric, possibly filled with oil or mica or other insulators, which allows for excellent performance at high frequencies, is stable over time, and is suitable for medium or very high voltages.

[0169] The capacitor may be a film capacitor, in which each type of conductor and dielectric is in the form of a thin film and stacked on top of each other. The stack may be rolled up to form a cylindrical or parallelepiped three-terminal unit capacitor.

[0170] Of course, these concepts can be extended to form capacities with more than three terminal units, which may be useful, for example, when the grid is a three-phase grid.

[0171] Advantageously, provision can be made that, in addition to creating the residual voltage V res In addition to the common mode voltage (ie the common mode voltage), the first measuring member O1 is also able to create a grid voltage V net (ie, differential mode voltage). For example, according to the grid voltage V we want to measurenet To characterize the spectral components, resistive and / or capacitive voltage dividers may be used.

[0172] Figure 11 A resistive voltage divider bridge is shown with four resistors R1, R1', R2, R2' and five electrodes T1 to T5. We find that two electrodes T1, T2 are able to connect the bridge to the conductors C1, C2 and that the third electrode T3 is able to draw and measure the midpoint voltage corresponding to the common-mode voltage between the two power conductors. Therefore, the series resistance R1+R1' formed by the resistors R1, R1' arranged on one side of the midpoint is equal to the series resistance R2+R2' formed by the resistors R2, R2' arranged on the other side of the bridge relative to the midpoint. Complementary electrodes T4, T5 are arranged at the level of the midpoint that connects the resistors in each bridge branch in series, making it possible to provide the grid voltage V by controlling the gain (defined by the relationship (R1+R1') / (R1+R1'+R2'+R2)). net The voltage image of . Therefore, the voltage extracted between the complementary electrodes T4, T5 is compatible with the rest of the processing performed by the electronic acquisition chain. For example, if the grid voltage V net is about 800V, we can choose the bridge resistors so that the gain is about 1 / 100.

[0173] For example, the two resistor elements R1 and R2 can be selected to be equal to one another, for example, between 10 kΩ and 1 MΩ, and equal to 99 times the value of the first resistor R1' connected to the midpoint T3. The other resistor R'2 connected to the midpoint on the other side of this point is also selected so that the other resistor R'2 has the same value as the first resistor R1'. The control gain applied to the differential-mode voltage present between the two power conductors is equal to (R1+R1') / (R1+R1'+R2'+R2), which in this case is equal to R'1 / (R1+R'1).

[0174] Thus, the resistance bridge is preferably implemented as a single component of the paired resistor divider type, i.e., in which the values ​​of some resistors are fixed in advance according to a predetermined ratio relative to the other resistors and in which all resistors are carried on the same support ("thick film" or "thin film") to reduce thermal drift. The result is a resistor divider having three or five terminal units, depending on the embodiment chosen.

[0175] In order to improve the performance in harsh environments when measuring non-DC components, it is important to realize that Figure 6 The common mode current I1+I2 flowing in the two capacitive elements EC1 and EC2 of the capacitive voltage divider shown forms a differential mode voltage V net By means of a first measuring member O1 equipped with a common-mode current sensor, it is possible to create this differential-mode voltage Vnet The common-mode current sensor may be formed by two air coils (eg, two Rogowski probes) arranged near capacitive elements EC1 and EC2, respectively.

[0176] Then, Figure 7 An example of implementing these principles is shown. A cylindrical three-terminal unit capacitor has been formed by winding the type A film, the type B film, and the type G film as described previously, and the three terminal units T1, T2, and T3 of the capacitor are electrically connected to the first power conductor C1, the common conductor, and the second power conductor C2 via a dipole SH, respectively. By measuring the resistance of the dipole SH between the terminal unit T2 (forming the midpoint M between the two capacitive elements EC1 and EC2 in the capacitor) and the common conductor C, it is possible to extract a quantity representing the common mode voltage V res , as previously described. Two Rogowski type current sensors RG1, RG2 are arranged in the winding around the cylindrical capacitor to image the currents I1, I2 flowing in the capacitor. The quantities provided by these sensors can be combined to give a differential mode voltage V net image.

[0177] In an advantageous embodiment, the differential mode voltage V net and / or common mode voltage V res The current sensor of the image implements planar coil technology. In this case, two types of coils are arranged in parallel but different planes to be able to measure the common mode current (differential mode voltage V net The image of the derivative of the differential mode current (common mode voltage V res The two planes may be located in different layers of a multilayer printed circuit board, wherein the planar coil is located in the multilayer printed circuit board.

[0178] like Figure 8a 、 Figure 8b As shown, the printed circuit board may include on a first layer two tracks P1, P2 electrically connected to power conductors C1, C2, respectively. These tracks are also connected to a three-terminal unit capacitor C3, the point M of which is electrically connected to a common conductor Cc via a measuring dipole SH (here, formed by a single conductor) to form a differential current. A planar coil for measuring the differential current Bcd, for example four such coils consisting of two pairs of coils mounted in anti-series, is used. Figure 8a ), can be placed on the second layer of the circuit board, and the planar coil (or four coils) for measuring the common current Bcc can be placed on the third layer of the circuit board ( Figure 8b ).

[0179] The advantage of this variant is that it eliminates the influence of the current flowing in the common conductor, regardless of its frequency. The electromotive force transmitted by the planar coil is proportional to the second derivative of the measured voltage with respect to time, so the electromotive force must be integrated twice before the energy calculation can be performed. The assembly is preferably carried out according to printed circuit board technology applied to power, so that the geometry of the coil can be controlled and a known transformation ratio can be obtained without calibration, with extremely low drift over temperature and time. It should be noted that this method can usually be implemented as a measurement of the differential mode voltage V net Or common mode voltage V res .

[0180] Typically, the measuring member O1 may be equipped with a common mode voltage V res The measuring member O1 may also be equipped with a sensor for the DC component and the variable component of the differential mode voltage V net Sensors for DC and variable components.

[0181] Of course, the invention is not limited to the embodiments described and alternative embodiments can be implemented without departing from the scope of the invention as defined by the claims.

[0182] Therefore, a device D according to the invention is provided for formulating a value representing the mixed energy E obtained from the common mode voltage and the grid current and transmitted in the measurement area. mix This quantity is processed and compared with a threshold value in order to identify a fault. It is perfectly understandable that the quantity representing the mixed energy may correspond to a common mode voltage which is compared with a threshold value modulated according to the intensity of the grid current. In all cases, the mixed energy E is used mix The first quantity and the second quantity are used to generate a signal S indicating a grid fault. Therefore, although a formal energy calculation constitutes a particular embodiment, the detection method according to the invention does not necessarily perform a formal energy calculation.

Claims

1. A detection device (D) for detecting a fault in an electrical network (1), the electrical network (1) comprising at least one electrical device (E), the at least one electrical device (E) being electrically connected to a first power conductor (C1) and a second power conductor (C2), the electrical network (1) being equipped with a common conductor (Cc), the detection device (D) being intended to be connected to the first power conductor (C1) and the second power conductor (C2) and the common conductor (Cc) of the electrical network (1) at the level of a measurement area, and comprising: - a first measuring member (O1) capable of determining a first quantity (V res ), the first amount (V res ) represents a common mode voltage present on the first power conductor (C1) and the second power conductor (C2); - a second measuring member (O2) capable of determining a second quantity (I net ), the second amount (I net ) represents the grid current flowing in the first power conductor (C1) and the second power conductor (C2); a calculator (UP) connected to said first measuring member (O1) and said second measuring member (O2), said calculator (UP) being configured to determine, within a determined observation period, a quantity representative of energy, said energy being called the mixed energy (E mix ), the mixing energy (E mix ) is defined as the product of the common mode voltage and the grid current integrated within the determined observation period and transmitted in the measurement area, according to the first quantity (V res ) and the second amount (I net ) determines the mixing energy (E mix ) of the amount.

2. The detection device (D) according to claim 1, wherein The power grid (1) is a direct current (DC) power grid.

3. The detection device (D) according to claim 1, wherein The fault is a series arc.

4. Detection device (D) according to one of claims 1 to 3, wherein The calculator (UP) is further configured to use a value representing the determined mixing energy (E mix ), generating a signal (S) indicating the fault of the power grid.

5. Detection device (D) according to one of claims 1 to 3, wherein The first measuring means (O1) and the second measuring means (O2) are configured to respectively determine the first quantity (V res ) and the second quantity (I net ).

6. Detection device (D) according to one of claims 1 to 3, wherein The first measuring member (O1) is also capable of determining a third quantity (V net ), the third quantity (V net ) represents the differential mode voltage existing between the first power conductor (C1) and the second power conductor (C2), and the calculator (UP) is further configured to calculate, within the determined observation period, the differential mode voltage according to the third quantity (V net ) and the second amount (I net ) determines the grid energy (E) transmitted in the measurement area net ) amount.

7. Detection device (D) according to one of claims 1 to 3, wherein The second measuring member (O2) is also capable of determining a fourth quantity (I res ), the fourth amount (I res ) represents the common mode current flowing in the first power conductor (C1) and the second power conductor (C2), and the calculator (UP) is further configured to calculate, within the determined observation period, the fourth quantity (I res ) and the first amount (V res ) determines the residual energy (E) transmitted in the measurement area res ) amount.

8. The detection device (D) according to any one of claims 1 to 3, further comprising a network controller (NET), wherein the network controller (NET) is used to connect the calculator (UP) to a communication bus (BUS).

9. The detection device (D) according to claim 8, wherein The communication bus (BUS) is the common conductor (Cc), and the network controller (NET) is connected to the common conductor (Cc).

10. An electrical device comprising the detection device (D) according to any one of claims 1 to 9.

11. The electrical device according to claim 10, wherein The electrical equipment is a power source or a load.

12. A system for locating a fault in an electrical network (1), the electrical network (1) comprising at least a first power conductor (C1) and a second power conductor (C2), the locating system comprising: - Common conductor (Cc); - two detection devices (D) according to one of claims 1 to 9, connected to the first (C1) and second (C2) power conductors and the common conductor (Cc) at the level of the respective measurement areas; a monitoring device (V) connected to the two detection devices (D) via a communication bus (BUS), the monitoring device (V) comprising calculation means configured to use information provided by the two detection devices (D) on the communication bus (BUS) to locate a fault occurring in the power grid (1) in a portion of the first power conductor (C1), the second power conductor (C2) and the common conductor (Cc) between the two detection devices (D).

13. An electric network (1), said electric network (1) being a direct current or alternating current electric network, said electric network (1) comprising at least two electric devices (E), said at least two electric devices (E) being connected via at least one first power conductor (C1) and a second power conductor (C2), said electric network being equipped with: - Common conductor (Cc); - a plurality of detection devices (D) according to one of claims 8 and 9, connected to the first (C1) and second (C2) power conductors and the common conductor (Cc) at the level of the respective measurement areas; - a monitoring device (V) connected to a plurality of said detection devices (D) via said communication bus (BUS).

14. The power grid (1) according to claim 13, wherein The communication bus (BUS) includes clock information.

15. The power grid (1) according to claim 13 or 14, wherein: The monitoring device (V) comprises calculation means configured to detect a fault occurring in the electrical network (1) using information provided by a plurality of the detection devices (D) on the communication bus (BUS).

16. The power grid (1) according to claim 13 or 14, wherein: The first power conductor (C1) and the second power conductor (C2) have the same geometric shape.

17. The power grid (1) according to claim 13 or 14, wherein: At least one of the electrical devices (E) is a source, the common conductor (Cc) being connected to a midpoint of the source.

18. The power grid (1) according to claim 13 or 14, wherein: The first power conductor (C1), the second power conductor (C2) and the common conductor (Cc) are assembled together in parallel to form a single cable or harness.

19. A method for detecting a fault in an electrical network (1), said electrical network (1) comprising at least one electrical device (E), said at least one electrical device (E) being electrically connected to two power conductors (C1, C2), said electrical network (1) being provided with a common conductor (Cc), said method comprising the following steps: - determining a first quantity (V res ), the first amount (V res ) represents the common mode voltage of the two power conductors (C1, C2); - determining a second quantity (I net ), the second amount (I net ) represents the grid current flowing in the two power conductors (C1, C2) of the grid (1); - Using the first amount (V res ) and the second amount (I net ), to detect the occurrence of a series arc in the power grid (1); The detection method further comprises: A quantity representing energy is determined within a certain observation period, said energy being referred to as the mixing energy (E mix ), the mixing energy (E mix ) is defined as the product of the common mode voltage and the grid current integrated within the determined observation period and transmitted in the measurement area, according to the first quantity (V res ) and the second amount (I net ) is multiplied to determine the mixing energy; During the determined observation period, a mixed energy (E mix ) and the mixing energy (E mix ) to locate the occurrence of the series arc in the power grid (1).

20. The detection method according to claim 19, wherein The fault is a series arc.

21. The detection method according to claim 19, further comprising the step of processing the mixed energy (E mix ) amount.

22. The detection method according to claim 21, wherein Processing represents the mixed energy (E mix ) includes determining the change in the mixing energy.

23. The detection method according to any one of claims 19 to 22, wherein Using the determined mixing energy (E mix ) to locate the occurrence of the series arc in the power grid (1), including: locating the occurrence of the series arc in the power grid (1) by calculating the difference in the mixed energy.

24. A method of deploying a system for detecting a fault in an electrical network (1), the electrical network (1) comprising at least one first electrical power conductor (C1) and a second electrical power conductor (C2), the method comprising the steps of: - equipping the electrical network (1) with a common conductor (Cc); - electrically connecting at least one detection device (D) according to one of claims 1 to 9 to the first (C1) and second (C2) power conductors and the common conductor (Cc).

25. The method according to claim 24, wherein The fault is a series arc.

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