Arrangement for measuring common-mode voltage in an electrical network and device for detecting a fault using such an arrangement

Abstract

The invention relates to a component (01) for measuring a variable representative of a common-mode voltage (Vres), the component (01) being located in an electrical network (1) or in an installation (E) comprising at least a first electrical power conductor (C1) and a second electrical power conductor (C2), the measuring component (01) comprising two capacitive elements (EC1, EC2) intended to be arranged in a bridge between the two electrical power conductors (C1, C2) and having the same capacitance value as one another, in which the two capacitive elements (EC1, EC2) are connected at a midpoint (M). The measuring component (01) also comprises a two-terminal measurement circuit (SH) connected on the one hand to the midpoint (M) and on the other hand to a connection terminal intended to be electrically connected to a common conductor (Cc) provided in the electrical network (1) or in the installation (E).

Description

TECHNICAL FIELD

[0001] The present invention relates to a device and a method for detecting a fault in an electrical energy distribution network. The invention also relates to an electrical energy distribution network or equipment equipped with such a detection device. BACKGROUND

[0002] The need to reduce the carbon footprint of human activities, as well as the need to optimize energy efficiency, leads to the use of electrical energy. This work requires the transmission of electrical energy in the form of direct current (DC) or alternating current (AC) between one or more sources (for example batteries, generators, photovoltaic panels) and one or more loads (electric motors, inverters, etc.) through distribution lines, protection systems (circuit breakers, blocking switches and other cut-off means). The collection of sources, loads, lines and protection systems constitutes an electrical network.

[0003] Sometimes, it is necessary for the electrical network to transmit a large amount of power that can exceed several tens of kilowatts, or even several hundreds of kilowatts, or even megawatts. For example, the electrical network can be loaded in a vehicle such as a land vehicle (car or tank) or a railway, a surface ship or a submarine or an aircraft. Thus, the electrical network can work in a harsh environment, i.e. an environment in which large temperature, pressure, vibration, electromagnetic field or humidity variations can occur. In these applications, the failure of the electrical network can have serious consequences, and it is therefore necessary to secure the electrical network.

[0004] More generally, independently of the field of application, it is important to be able to detect and advantageously locate a fault occurring in an electrical network. The detection of a fault generally causes the switching of protection devices, which electrically isolate at least one part of the electrical network. These protection devices can be, for example, circuit breakers, contactors, solid-state switches, fuses or current limiters, which open when an excessive current occurs. The location of the fault makes it possible to isolate only the faulty part of the electrical network, the advantage of this function being that it makes it possible to maintain a minimum level of operation of the electrical network, as well as targeted interventions by a repair team.

[0005] Faults that can occur in an electrical network have various characteristics: insulation defects, losses due to excessive switching at the level of the loads, excessive energy consumption, short circuits, etc. A fault can also be the formation of an electric arc in or between the conductors and electronic devices that make up the electrical distribution line. An electric arc corresponds to an unintentional discharge that propagates in a gas (air) between two electrically conductive segments of the electrical network. When such a discharge occurs in the electrical insulation that surrounds the conductors, but without completely damaging the conductors, this discharge is called a "partial discharge". These discharges can be caused by many factors, such as improper connection of the conductors, degradation of the electrical insulation surrounding these conductors, the presence of foreign bodies or poor quality of the insulation. These factors are common phenomena in electrical networks that can lead to fires, explosions, a significant increase in local temperature of more than 10,000°C, high overpressure and the emission of a large amount of ultraviolet radiation. The humidity, low air pressure and temperature of the environment contribute to the appearance of these electric arcs, so early detection of electric arcs is particularly important when the electrical network is operating in harsh environments as described above.

[0006] The usual protection devices, such as circuit breakers, which are triggered based on excessive current consumption or power consumption, generally do not detect electric arcs early enough. Some electric arcs take a long time to form and do not cause an overcurrent or overpower to appear in the electrical network, so that early detection of electric arcs by usual means is not possible. This is particularly the case for "series" electric arcs that can form in the electrical conductors or connectors. The power consumed during the start-up of a series electric arc is much lower than the power consumed by a parallel electric arc or the nominal power of the electrical network.

[0007] The detection of electric arcs in an electrical network is generally carried out by monitoring the temporal and / or frequency evolution of the electrical network signals (current and / or voltage), knowing that the occurrence of this phenomenon leads to the formation of a signal with strong spectral components, even in the case of a direct current electrical network. An example of such a detection solution is presented in particular in document US10078105. However, these methods based on temporal or spectral analysis of the signals (current and / or voltage) are particularly difficult to implement and lead to many false positives, which can be caused by the loads or active sources (i.e. switched on) present on the electrical network. In particular, these methods do not effectively detect the occurrence of series electric arcs in a direct current electrical network (DC).

[0008] Object of the invention

[0009] The object of the present invention is to remedy the aforementioned drawbacks. One object of the present invention is in particular to propose a device and a method for detecting faults in an electrical network that are particularly reliable and suitable for detecting the occurrence of various faults, advantageously locating various faults, such faults including in particular electric arcs, and in particular series electric arcs, in a direct current electrical network. Summary of the invention

[0010] To achieve this aim, the purpose of the present application proposes a means for measuring a quantity representative of a common-mode voltage, the measuring means being located in an electrical network or in a device, the electrical network or the device comprising at least a first power conductor and a second power conductor, the measuring means comprising two capacitive elements intended to be arranged in a bridge between the two power conductors and having the same capacitance value as each other, the two capacitive elements being connected at a midpoint. The measuring means further comprise a measuring dipole connected on the one hand to the midpoint and on the other hand to a connection terminal intended to be electrically connected to a common conductor equipped to the electrical network or to the device.

[0011] According to other advantageous and non-limiting characteristics of the application, these characteristics are taken separately or in any technically feasible combination:

[0012] - the impedance of the measuring dipole is less than 1 kOhm, the dipole being able to generate a voltage proportional to the time derivative of the common-mode voltage present between the two power conductors;

[0013] - the impedance of the measuring dipole is greater than 1 kOhm, the dipole generating a voltage proportional to the common-mode voltage present between the two power conductors;

[0014] - the capacitive elements are formed from three-terminal capacitors, a first terminal being intended to be electrically connected to one of the power conductors, a second terminal being intended to be electrically connected to the other of the power conductors, a third terminal being intended to be connected to the common conductor;

[0015] - the three-terminal capacitors are made from only 3 electrodes;

[0016] - the three-terminal capacitors are made from a stack of sheets, then rolled up to form a cylinder or a three-terminal parallelepiped;

[0017] - the measuring means further comprise a three-electrode resistor having a midpoint, a first electrode being intended to be electrically connected to the first power conductor, a second electrode being intended to be electrically connected to the second power conductor, the common-mode voltage being present between the midpoint of the three-electrode resistor and the common conductor.

[0018] - the measuring means comprise a current sensor able to measure a differential-mode current flowing in the two capacitive elements to create a quantity representative of the common-mode voltage, and the current sensor is formed from at least four air coils arranged respectively in the vicinity of the capacitive elements;

[0019] - the measuring means further comprise a current sensor able to measure a common-mode current flowing in the two capacitive elements to create a quantity representative of the differential-mode voltage;

[0020] - the current sensor for measuring the common-mode current is formed from at least two air coils arranged respectively in the vicinity of the capacitive elements;

[0021] - The measuring component further includes a common-mode voltage (V) measurement element. res A sensor for the DC component of a sensor;

[0022] The measuring component further includes a sensor for the DC component of the differential-mode voltage.

[0023] According to another aspect, the present invention provides an apparatus for detecting faults in a power grid, the power grid including at least one electrical device electrically connected to a first power conductor and a second power conductor. According to the invention, the power grid also includes a common conductor, and the apparatus is designed to connect to the power conductor and the common conductor at a measurement area, and the apparatus includes:

[0024] -The first measuring component as described above;

[0025] - A second measuring component is used to generate a second quantity, which represents the grid current flowing through the power conductor;

[0026] - A calculator, connected to a first measuring component and a second measuring component, is configured to determine a quantity representing so-called "mixed" energy within a defined observation period. "Mixed" energy is defined as the integral of the product of common-mode voltage and grid current over the defined observation period and transmitted within the measurement area. The quantity representing mixed energy is determined based on the first quantity and the second quantity.

[0027] Further advantageous and non-limiting features of this aspect of the invention, which may be employed individually or in any technically feasible combination:

[0028] - The second measuring component includes an air coil, such as a Rogowski type air coil;

[0029] - The second measuring component also includes a DC sensor, such as Neel sensor. Attached Figure Description

[0030] Other features and advantages of the invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings, in which:

[0031] [ Figure 1a ]

[0032] [ Figure 1b ] Figure 1a and Figure 1b An example of a power grid according to an embodiment of the present invention is shown;

[0033] [ Figure 2 ] Figure 2 This shows the power grid status during observation period j created by the monitoring device;

[0034] [ Figure 3] Figure 3 A part of the electrical network according to the application is shown;

[0035] [ Figure 4a ]

[0036] [ Figure 4b ]

[0037] [ Figure 4c ] Figure 4a 、 Figure 4b and Figure 4c show a part of the electrical network during the occurrence of a parallel fault, an insulation defect fault and a series fault, respectively;

[0038] [ Figure 5 ] Figure 5 A detection device according to an embodiment of the application is shown.

[0039] [ Figure 6 ] Figure 6 A schematic circuit representing another embodiment of a first measuring member forming the detection device is shown.

[0040] [ Figure 7 ] Figure 7 An example of an embodiment of a first measuring member of the detection device is shown;

[0041] [ Figure 8a ]

[0042] [ Figure 8b ]

[0043] Figure 8a and Figure 8b Another example of an embodiment of a first measuring member of the detection device is shown;

[0044] [ Figure 9 ] Figure 9 A system for detecting and locating a fault according to the application is shown.

[0045] [ Figure 10 ]

[0046] [ Figure 11 ]

[0047] 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 application is shown. DETAILED DESCRIPTION

[0048] For the sake of conciseness of writing, in this description we will use the measure of a quantity (e.g. energy, voltage, current) (indicative of the quantity of energy, voltage or current measured or estimated) to understand the quantity.

[0049] Power grid

[0050] Figure 1a and Figure 1b Two examples of an electrical network 1 are shown, which is monitored for proper operation by detecting the occurrence of faults of the electrical network 1 and advantageously by locating the faults. As introduced in the introductory part of the present application, these faults can have very different characteristics, series arcs or parallel arcs, overconsumption, short circuits or any other insulation defect.

[0051] In a conventional manner, the electrical network 1 comprises at least two electrical conductors allowing the transmission of the required electrical power. The electrical network 1 can be a direct current network (DC), it will then be considered that the network frequency of the electrical network 1 is comprised between 0 and 5 Hz to maintain all the generality of the present description with respect to it. The electrical network 1 can be a fixed frequency conventional single-phase alternating current network with a network frequency of 50 Hz or 60 Hz or 400 Hz ± 5 Hz, alternatively, the electrical network 1 can be a variable frequency alternating current network, usually comprised between 360 Hz and 800 Hz. But more generally, the electrical network 1 can operate in any suitable frequency range. The present application can also be applicable to multi-phase electrical networks, for example three-phase electrical networks.

[0052] The present application is particularly applicable when the purpose of the electrical network 1 is to transmit a relatively large amount of electrical power between the various electrical devices, sources or loads that make up the electrical network 1. Thus, it is preferred that the values of the voltage and current formed on the electrical network 1 are generally higher than 50 V, 330 V, 600 V, 1000 V, 3000 V or 10000 V and 100 A, respectively. However, it is not excluded that the principles of the present application are applied to electrical networks that transmit a relatively small amount of power.

[0053] As can be seen in figure 1, the electrical network 1 comprises a plurality of electrical devices E (more generally, at least one electrical device E), sources or loads, and conductive lines L connecting some of the devices E to each other, here in the form of a mesh network, to power the loads with the energy provided by the sources. The electrical devices E are connected to the lines L by binding terminals B. Protection means, such as circuit breakers, disconnectors or any other cutting means, are part of the electrical network 1 and of its electrical devices E, even if they are not shown in the figures.

[0054] The electrical devices E can be any type of device suitable for the field of electrical network applications. Some of these devices E can alternately form sources and loads (generators / motors). The devices can be power distribution devices. The devices can be active devices, such as inverters, or passive devices. When the electrical devices E form sources, the electrical devices E can be, for example, batteries or generators or photovoltaic panels or wind turbines, etc. There can be a combination of several sources and several loads in the same electrical network. The electrical devices E can be connected to each other in series or in parallel. Figure 1bIn the example of figure 1, we denote by E1 a power distribution device, E1 being arranged at the level of a network node between a source Es and two loads arranged at the extremities of a line L.

[0055] To implement the protection of the electrical network 1, the electrical network 1 is equipped with a common conductor (which will be described in more detail later in the present description) and comprises at least one detection device D, advantageously a plurality of such devices D, distributed in the electrical network 1 at the level of a plurality of measurement zones. The detection device D has connection terminals enabling it to be connected to the conductors of the line L or of the electrical devices E, so as to be effectively placed in the electrical network. Preferably, the detection device D is non-intrusive, i.e. it is connected in parallel to the power conductors of the line L and to the devices E forming the electrical network 1 (for example to make voltage measurements), or it implements non-intrusive sensors (for example air coil type sensors, Hall effect or Neel effect type sensors for measuring currents). This reduces the number of interconnections on the conductors, thus reducing the risk of arc type faults.

[0056] The present invention provides a distinction between all the energies transmitted by the electrical network, thus, at the level of each measurement zone, between an energy called "network energy", an energy called "surplus energy" and an energy called "mixed energy". The network energy corresponds to the energy transmitted in the measurement zone when the electrical network is perfectly balanced and without any fault. The surplus energy and the mixed energy reflect the imbalances in the electrical network 1 due to the occurrence of an electrical network fault. However, in a healthy electrical network, the surplus energy and the mixed energy are not completely zero due to certain natural imbalances. To this end, according to some embodiments of the present invention, the point-to-point differences or differences between the measurable energies at different instants are expected to detect certain faults and also to locate certain faults, but not to generate false positives related to natural imbalances.

[0057] As will be described in more detail later in the present description, the detection device D according to one embodiment of the present invention is adapted to measure, during successive observation periods, the network energy E net , the surplus energy E res and the mixed energy E mix , these energies being transmitted at the level of the measurement zone of the electrical network 1 in which the detection device D is located. The measurement of these energies makes it possible to detect, sometimes to locate, a fault occurring in the electrical network 1 or in a part of the electrical network 1. At least, such a detection device D is adapted to measure the mixed energy E mix ​, in order to be able to detect series arcs. For the sake of clarity, we explicitly state that by "localizing a fault" we mean the ability to identify the part of the electrical network 1 in which the fault has occurred or the ability to identify the device E in which the fault has occurred. This part can be defined by the part of the electrical network comprised between two detection means D, or by a device E of the source type arranged upstream of the means D, or by a device E of the load type arranged downstream of the detection means D.

[0058] The electrical network 1 can also comprise a protection means P or a plurality of such means P, making it possible to isolate a part of the electrical network 1 (for example a line L or an electrical device E). For example, the protection means P can be a conventional circuit breaker. Generally, such means P are placed at the level of the sources, at the level of the loads, or most often, at the level of the nodes of the electrical network, via the electrical distribution devices E1, as shown in Figure 1b .

[0059] The detection means D and the protection means P can be distributed very freely in the electrical network 1, according to their characteristics and topology, to ensure protection of the electrical network 1. One and / or the other of these means D, P can be placed at the end of a line L, on a part of a line L, or integrated in an electrical device E. The detection means D and the protection means P are not necessarily associated with each other, but in some cases (for example in the same case) it can be advantageous to associate the detection means D and the protection means P in order to facilitate the implementation of a single module to implement both the detection and protection functions. In this case, the detection terminals of the detection means D can be connected to the triggering terminals of the protection means P, on which a detection signal S is generated when a fault is detected.

[0060] Some parts of the electrical network 1, of the line L or of the device E can not be equipped with detection means D and / or protection means P. In this case, it can not be possible to detect or localize a fault occurring in this part of the electrical network 1, and / or it can not be possible to disconnect this part of the electrical network 1. However, the occurrence of a fault can be detected by a detection means D arranged outside the part in which the fault occurs, and the entire electrical network 1 can be protected, for example by disconnecting the electrical network 1 from the devices E forming the energy sources. To this end, as will be detailed in the remainder of the present description, we can measure the energy variation directly at the output of the source or directly at the input of the load. When the detection means D are placed respectively at the output of the source and at the input of the load, it is preferable to place the detection means D respectively as far upstream and as far downstream as possible, so as to also detect defects in the protection means P or in the connection terminals B.

[0061] As will become apparent in the remainder of the present description, depending on the electrical network energy E net , the residual energy E res and / or the hybrid energy E mixThe detection means D are adapted to generate an electrical signal S on the detection terminals of the device D, indicating the occurrence of a fault in the electrical network 1. When the detection means D are locally associated with the protection means P, the signal S can be used locally by the protection means P to immediately isolate the faulty electrical network section, line L or equipment E from the rest of the electrical network 1.

[0062] In order to detect other categories of faults, such as arcs occurring between two parallel conductors, to more precisely locate faults in the electrical network 1, or to quantify faults according to the energy consumed, it can sometimes be necessary to use the energy measurements E net , E res , E mix provided by a plurality of detection means D. To this end, according to a particular embodiment of the application, the electrical network 1 is associated with a monitoring device V. This device V is generally implemented by digital computing means, connected to at least some of the detection means D of the electrical network 1 by means of a communication bus BUS, represented by a dashed line in Figure 1. Any type of bus can be suitable for implementing the communication bus BUS, including in particular serial or parallel buses operating under any possible protocol, whether or not they comply with established standards. It should be noted that the monitoring device V can be integrated into one of the detection means D. In this case, it can be provided that the detection means D comprise computing means, so that they are adapted to implement a monitoring process, then at least one of the detection means can be activated to operate as a monitoring device V of the electrical network 1.

[0063] In the configuration in which the electrical network 1 is equipped with a plurality of detection means D coupled to a monitoring device V, the devices are configured to place on the communication bus BUS data indicating the occurrence of a fault, and / or data representing the energy E net , E res , E mix measured over a given observation period. On the computer network formed by the communication bus BUS, the detection means D are identified by a unique identifier. The communication bus BUS comprises clock information assigned to each detection means D, so that each detection means D shares a common time base. The data E j net,i , E j res,i , E j mix,i represent the energy measured by the identification device i over a determined observation period j and placed on the communication bus BUS, so that the data E j net,i , E j res,i , E jmix,i The data is sorted and processed to determine the state of the power grid at a given moment, i.e., the amount of grid energy, surplus energy, and mixed energy transmitted in each measurement area during a given observation period.

[0064] Figure 2 The diagram shows the state of power grid 1 in Figure 1 at the instant of observation period j, when observation period j can be created by monitoring device V. Here, each detector D1, D2, D3, D4 of the power grid is identified by an index corresponding in a simplified manner to the detector's identifier on the computer network. Each detector displays its mixed energy measurement value E. j mix,i (and its absence) Figure 2 Other measurements E shown j net,i E j res,i This is placed on the communication bus BUS, enabling the monitoring device V to send data structures related to the power grid status. Figure 2 The data structure is represented by the energy level table T transmitted in each measurement area. This data structure can record the grid energy, surplus energy, and mixed energy of each measurement area in a table indexed by the observation period j. Detection device D( Figure 2 (Not shown) can be advantageously placed at the level of allocating "nodes", for example, in the power distribution equipment of power grid 1, such as... Figure 1b As shown.

[0065] The monitoring device V is configured to use data provided by the detection device D of the power grid 1 and transmitted via the communication bus BUS. The purpose of this use is to detect faults in the power grid, and / or locate the faults in the power grid 1, and / or quantify the detected faults in terms of energy.

[0066] The monitoring device V can issue a signal indicating a fault in the power grid 1, and can use this signal to disconnect a portion of the power grid. For this purpose, the monitoring device V can be connected to at least some of the protection devices P of the power grid 1 to activate these protection devices P when appropriate. This can be a point-to-point connection, or a connection to a communication bus BUS or another dedicated bus, with the protection devices P connected to the dedicated bus. In another embodiment, particularly when the monitoring device is integrated into a detector D of the power grid, the monitoring device can communicate with a third-party device responsible for controlling the protection devices P of the power grid.

[0067] Therefore, it should be understood that, according to Figure 1a and Figure 1b The embodiment of the present invention shown includes a power grid 1 and multiple detection devices D distributed on the power grid 1 at the level of the measurement area. These devices D transmit data E to the monitoring device V. j net,i E jres,i j mix,i j net,i j res,i j mix,i represents the energy transmitted in these measurement zones i within a determined observation period j. The monitoring device V can use this data to represent the state of the electrical network, i.e. the energy transmitted in each measurement zone within successive observation periods.

[0068] The energy data or data representing the variation in energy above a certain threshold enables the detection of a fault, but not necessarily the location of the fault (except at the level of the end of the electrical network, where the variation in energy enables the location of the defect). On the other hand, the analysis of the difference in energy transmitted between two (or more) detection devices D not only enables the detection quality to be improved, but also enables the location of the fault between these two detection devices (D). To do this, 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 electrical network 1, in a part of the conductors Ci, C2, Cc comprised between these two devices, or a fault occurring in the equipment E of the electrical network. Thus, as shown in Figure 9

[0069] Thus, the monitoring device V is suitable for detecting and / or locating and / or quantifying a fault occurring on the electrical network 1, in order to protect the electrical network 1, for example by disconnecting the part of the electrical network 1 in which the fault has been located.

[0070] Common conductor

[0071] ​​​​​In order to be able to distinguish between the different forms of energy transmitted by the electrical network 1 formed by the electrical power conductors on which the energy is transmitted, the application provides that the electrical network 1 is equipped with a common conductor. This common conductor forms a reference voltage for all the electrical equipment E in the electrical network that is electrically connected to the common conductor. The common conductor can be a mechanical mass of the electrical network or can be neutral, but this is not necessarily the case. The common conductor is not used to carry strong currents, but can be at a high electrical potential with respect to the mechanical mass. The common conductor can be a simple electrical cable, for example the cable that at least partially constitutes the communication bus BUS mentioned above. Alternatively, the common conductor can be a conductor similar to the conductors that form the electrical power conductors. When the equipment E of the "source" or "load" type is symmetrical, the common conductor can be connected to the midpoint connection terminals of the equipment E of the "source" or "load" type (for example, the midpoint of two midpoint batteries or inverters or the midpoint of a photovoltaic panel). The common conductor can be connected to an existing midpoint of the equipment, source or load, or to a midpoint "manufactured" from a resistive divider on the source side and / or on the load side. Such a dividing bridge that allows the connection of the common conductor can be integrated in the detection device D.

[0072] In the case of a bipolar configuration (single-phase variable current AC electrical network or direct current DC electrical network), the line L thus consists of a first electrical power conductor and a second electrical power conductor, to which the common conductor is added. In the case of a three-phase configuration, the line L comprises a third electrical power conductor, to which the common conductor can be connected. For the sake of brevity, we will consider hereinafter that the electrical network 1 is a bipolar electrical network comprising two electrical power conductors, to which the common conductor is added, but the principles described are generally applicable to an electrical network comprising any number of electrical power conductors.

[0073] Definitions of grid energy, residual energy and hybrid energy

[0074] In order to illustrate the benefit of the common conductor in the detection of a fault in the electrical network, Figure 3 A part of the electrical network is shown by way of illustration, this part comprising a line L arranged between a source S and a load C. The line L consists of a first electrical power conductor Cl, a second electrical power conductor C2 and a common conductor Cc.

[0075] As can be seen from these figures, the current I 1s , I 2s , I 1c , I 2c is defined as the current flowing on the first electrical power conductor Cl and on the second electrical power conductor C2, respectively, on the source S side and on the load C side. We define the voltage V 1s , V 2s , V 1c , V 2c, the common conductor Cc and the potential difference existing between the first power conductor C1 and the second power conductor C2 on the source side S and the load side C, respectively.

[0076] It should be noted that the voltages and currents referred to in the remainder of this description vary in nature over time, i.e. the voltages and currents are represented in the form V(t) and I(t). However, for simplicity of writing, we will designate these variable currents and voltages as V and I.

[0077] Reference is made to Figure 3 , the source side and the load side of the grid voltage V net,s , V net,c as the differential mode voltage existing between the two power conductors C1, C2: V net,s = V 1s - V 2s and V net,c = V 1c - V 2c . Similarly, we define the source side and the load side of the grid current I net,s , I net,c as the differential mode current flowing over the two power conductors C1, 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 net corresponds to the integral of the product I net * V net over a certain observation period. This grid energy can be created on the source side E net,s and on the load side E net,c .

[0078] When the grid part in Figure 3 is in normal operation and fully balanced, the grid voltages V net,s , V net,c on both sides of the line L are identical and the grid currents I net,s , I net,c are identical. Thus, apart from losses dissipated in the line, the grid energy E net,s on the source side and the grid energy E net,c on the load side are likewise identical to each other.

[0079] The occurrence of a grid fault leads to a grid imbalance, which can be determined by measuring the residual voltages V res,s , V res,c , the residual voltages V res,s , V res,c on the source side by 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 ). Similarly, we can measure the residual currents I res,s , I res,c , the residual currents I res,s , I res,c are defined on the source side by the common-mode current I res,s = I 1s + I 2s and on the load side by the common-mode current I res,c = I 1c + I 2c . Naturally, the residual energy E res corresponds to the integral of the product I res * V res over a determined observation period. This residual energy can be created on the source side E res,s and on the load side E res,c .

[0080] Finally, we will also define the hybrid energy E mix as the integral of the product I net * V res over a determined observation period. This hybrid energy can be created on the source side E mix,s and on the load side E mix,c .

[0081] As mentioned previously, when the grid in Figure 3 is perfectly balanced, the residual voltage and the residual current are zero. The residual energy E res,s and the hybrid energy E mix,s on the source side and the residual energy E res,c and the hybrid energy E mix,c on the load side are also zero.

[0082] Fault of parallel type between power conductors (parallel arc)

[0083] A parallel type fault between the two power conductors C1, C2 of the lines of the grid shown in Figure 4a , Figure 3 can be modeled as a dipole DP1 placed between these two conductors C1, C2. The difference between the grid voltage V net,s on the source side and the grid voltage V net,c on the load side is not affected by the presence of this dipole, but the current circulating in the dipole DP1 between the power conductors C1, C2 will cause the grid currents I net,s , I net,can imbalance occurs, i.e. the grid current I net,s , net,c is no longer identical.

[0084] In the case of a fault of this parallel type between the two power conductors C1, C2, there is no residual current or residual voltage.

[0085] A fault of this parallel type (for example a parallel arc) between the two power conductors C1, C2 manifests itself in that the difference in the currents I net,s , net,c and / or in the grid energy E net,s , net,c on both sides of the line over a determined observation period. We note that in the case of such a parallel arc, the energy dissipated in the dipole DP1 modelling this parallel arc is much higher than the nominal power of the grid, making the difference in the currents I net,s , net,c and / or in the grid energy E net,s , net,c on both sides of the line able to clearly detect this fault.

[0086] In practice, in a grid of Figure 2 , the difference in the grid energy E j net,i , j net,i+1 can be compared with a grid energy threshold S i,i+1 to detect a fault of this parallel type between the two power conductors C1, C2 connecting the two detection devices D i , i+1 , whose identifiers are respectively i, i+1, in the period j, the grid energy E j net,i , j net,i+1 being provided respectively by the detection devices D i , i+1 by means of a communication bus BUS. The difference between the currents I j net,i and I j net,i+1 can also be used to detect and locate a defect of this parallel type, the currents I j net,i and I j net,i+1 being provided respectively by the detection devices D i , i+1This is provided by the communication bus BUS. It can be provided that the monitoring device V is configurable to perform other types of processing on the provided grid energy to detect the occurrence of this type of fault. For example, the energy provided over several successive observation periods can be summed, then the difference is taken and compared to a threshold value, to extend the observation period. This makes it possible to adjust the triggering time as a function of the power of the fault: a very high-power fault will cause the monitoring device V to react much more quickly than a defect of low power. This also makes it possible to ensure that the protection is not triggered in the event of a non-persistent transient fault.

[0087] In general, the trigger threshold S i,i+1 associated with the two detectors indexed i, i+1, the trigger threshold S i,i+1 is adjusted as a function of the characteristics of the equipment E of the grid 1, which can be located between the two detection devices D i , D i+1 , to take into account, for example, losses in the line or the connector, or even the consumption of equipment E having parallel characteristics and a known maximum power and lower than the characteristic power of the fault.

[0088] Fault of parallel type between power conductors and external elements (insulation defect).

[0089] With reference to Figure 4b , a fault of 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 this external element. The external element can be a common conductor Cc, a mechanical mass of the grid or any other electrical potential.

[0090] The grid voltage V net,s appearing on the source side and the grid voltage V net,c appearing on the load side are not necessarily affected by the occurrence of this type of fault, which depends on the earthing connection scheme reserved for the grid. In the case of a first fault, called "IT state", i.e. when the grid is isolated from the ground or from a mechanical mass, there is almost no impact on the grid energy, the residual energy and the hybrid energy. However, in order to identify the occurrence of this type of fault in the grid, a permanent insulation controller can be used, as described in more detail hereinafter. On the other hand, if an insulation defect occurs in a non-isolated grid or a second fault occurs in an isolated grid, the grid energy, the residual energy and the hybrid energy appear significantly different.

[0091] The current then flows in the dipole DP2 between the power conductor and the external element. Consequently, on the source S side and / or on the load C side, the current flowing on this power conductor is different from the current flowing on the other conductor. This difference gives rise to a residual current I res,s on the source side and / or a residual current I res,cThe current flowing through the dipole DP2 forms a potential difference which also influences the voltage of the power conductor and causes a residual voltage V res,s and on the load side a residual voltage V res,c .

[0092] Thus, within a certain observation period, the occurrence of an insulation defect causes a residual energy E res,s or E res,c on one side or the other of the line. In the case of a non-true defect, the change in residual energy will be more sensitive than the change in grid energy.

[0093] During the period j, the residual energy E j res,i is measured in the measurement region of the grid and by means of a detection device D (whose identifier is i) arranged in this region. Thus, for example, by comparing the measured residual energy E j res,i with a certain threshold value S i , the occurrence of such a fault can be detected. This detection can be carried out locally without having to call on the monitoring device V of the grid and without having to transmit the energy measurement to this device. As explained previously, this local detection can activate a local protection device P in order to isolate a part of the grid 1.

[0094] Such an insulation fault can cause a residual energy to occur which is far below 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 localization of this fault is then facilitated by taking the difference of these energies measured upstream and downstream of the line by using two detection devices D. The residual energy measurement is then transmitted to the monitoring device V with the processing capacity of this device, as introduced previously.

[0095] In other cases, the residual energy can be relatively small, it can then be advantageous to sum the residual energy measured over several successive observation periods and then to compare this with a threshold value in order to lengthen the observation period.

[0096] In the case of an insulated network (IT state type), if a first insulation defect occurs, the network will be able to continue to function completely, a permanent insulation controller (PIC) must be present to detect the first defect. This PIC measures the impedance between the network and the mechanical mass or the ground, for which the PIC injects a common-mode voltage (residual voltage) into the network at a very low frequency, generally 1 Hz. When the network 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 the occurrence of a residual current and a residual energy, in particular at the excitation frequency of the PIC. It is therefore 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 do this, the PIC and the detection device D must be synchronized, for example by sending a synchronization clock on the communication bus BUS.

[0097] Fault of series type (series arc)

[0098] Reference is made to Figure 4c , a series type of fault, for example a series arc occurring on a line L, most often on the connection terminal B, sometimes inside the power conductor C1, C2, a series type of fault can be modeled as a dipole DP3 placed in series on the conductor.

[0099] The network current I on the source side net,s and the network current I on the load side net,c are hardly affected by the presence of this dipole DP3. However, the flow of current in this dipole DP3 causes a voltage V d , a voltage V d such that the voltage carried by one power conductor is unbalanced, while the other conductor is not affected. This dispersion causes a residual voltage V res,s on the source side and a residual voltage V res,c on the load side.

[0100] Thus, the occurrence of a series defect causes a hybrid energy E mix,s or E mix,c on one side and / or the other of the line during a determined observation period. A series type of defect also causes a variation in network energy, but the variation in network energy is much lower than the nominal energy, so that it is not possible to reliably detect the occurrence of a series defect at an early stage by analyzing the network energy. On the other hand, a series defect does not cause any variation in residual energy.

[0101] During the period j, the hybrid energy E j is measured by means of a detection device D (whose identifier is i) arranged in a measurement zone of the network. mix,i Thus, for example, the energy E j is measured by means of a detection device D (whose identifier is i) arranged in a measurement zone of the network. mix,iwith a determined threshold S i The comparison makes it possible to detect the occurrence of such a fault. This detection can be made locally, without having to call on the monitoring device V of the electrical network and without having to transmit the measurements to this device. As explained previously, this local detection makes it possible to activate the local protection device P in order to isolate a part of the electrical network. It is also possible to use the measurements of the hybrid energy E i , D i+1 provided by the communication bus BUS to detect and locate a fault of the series type. j res,i and V j res,i+1 The difference between the measurements of the hybrid energy E

[0102] We note that the hybrid energy E mix arises from the asymmetry between the first power conductor and the second power conductor caused by the presence of a series dipole DP3 which models a fault of the series type. Thus, in order to make the most of the detection capabilities of the hybrid energy, we will try to avoid deliberately making the power conductors C1, C2 asymmetrical. For this reason, it is not appropriate to confuse one of the two power conductors with a mechanical mass of the electrical network. It is also important to avoid inserting a connector or any other element on only one of the power conductors in the line L.

[0103] In the case where the "natural" asymmetry of the electrical network produces a hybrid balancing energy in some measurement zones, even when the electrical network is operating normally, it is possible to determine and take into account this hybrid balancing energy in order to make a fault detection, for example by adjusting the level of the comparison threshold S i , or by identifying the temporal variations of the hybrid energy. Thus, it is possible to provide a calibration phase of the detection device D (or of the monitoring device V) of the electrical network 1, the aim of which is to input the level of the threshold which is exceeded by the measurements of the hybrid energy or of the residual voltage, which proves the occurrence of a fault of the series type. In general, as an example, a series arc produces a residual voltage of between 20 V and 50 V. We can then choose a threshold for detecting the difference in residual voltage close to 2 V, and a threshold for detecting the difference in hybrid energy which is 2 V multiplied by the value of the current I net . Thus, advantageously, it is possible to make the detection threshold S i vary as a function of the average value of the current I net of the electrical network.

[0104] As for the two types of fault described previously, it is also possible to provide the measurements of the hybrid energy prepared by each detection device D to the monitoring device V, then to analyse the two measurements of the hybrid energy D i and D i+1The mixed energy difference between the two measurements enables a more precise detection and localization of series type defects. The successive energy measurements can also be processed by summation or difference, which enables, in particular, the detection of low power defects over a longer observation period. The detection thresholds applied to the measurements of network energy, residual energy and mixed energy can be different from one another, or the detection thresholds applied to the difference of these energies between the two devices can be different from one another. As a matter of convention and depending on the nature of the defect (for example, series arc on the first power conductor CI or series arc on the second power conductor C2), it is specified that these thresholds can be negative and that the concept of energy "above" the threshold is understood as an absolute value.

[0105] To summarize the description of this section, we note that the measurement of network energy E net , residual energy E res and mixed energy E mix over a determined observation period in a determined network region enables the detection and localization of the occurrence of various faults. This detection can be performed locally in the measurement region by simply observing that the network energy, residual energy and mixed energy exceed a determined threshold. A more precise localization of these faults and the detection of a wider variety of faults can require the use of the measurements of these energies between two measurement regions of the network 1.

[0106] In particular, the measurement of mixed energy at the level of a single measurement region can be used to detect the occurrence of series type faults, such as arcs in the conductors of a device (for example, a source) or a line of the network, which is not easily achieved using the techniques known in the prior art. This aspect is therefore an important advantage of the solution described herein.

[0107] To facilitate this detection, the line L of the network 1 is advantageously designed to be as symmetrical as possible. In this respect, it is advantageous to choose the power conductors connecting the electrical devices E to one another so that the power conductors are identical, or so that they have identical geometrical shapes (diameters and properties of the conductors and insulators). 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 cable binding, or even a single cable, for example by embedding the conductors in an insulating material. This limits the asymmetry of the interaction of the conductors with the environment.

[0108] For the same reason of seeking balance, and in order to make the residual voltage zero in the absence of defect, the common conductor can be connected to the midpoint of an electrical device forming a source or a load. We can equip an electrical device E forming a source or a load without a midpoint with a resistance bridge between the two power conductors to connect the common conductor to the midpoint of this resistance bridge.

[0109] In order to be able to implement the measurements of the energy of the electrical network, of the residual energy and of the hybrid energy, the fault detector D is equipped with voltage and current sensors, making it possible to form, in the measurement zone, an image of the voltage carried by the conductor or of the voltage flowing in the conductor to which these sensors are connected. Advantageously, these sensors have a good linearity, are less affected by the environment (temperature, mechanical constraints, etc.) so as not to introduce a bias in the calculation of the energy between two remote points of the electrical network, and are less sensitive to ageing. These sensors also have a wide measurement passband, making it possible to take into account the spectral differences of the signals (voltage and current of the electrical network), in particular during a fault.

[0110] Generally, these sensors are suitable for implementing reliable measurements in a 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. The measurement means Oi, O2may each comprise one or more such sensors. They can in particular comprise sensors operating in different frequency ranges. Thus, it is conceivable for the measurement means Oi, O2to have sensors capable of measuring the direct current component of the signal and / or sensors capable of measuring certain non-direct current spectral components of the signal.

[0111] Advantageously, the sensors are suitable for providing a measurement of the direct current component of the current or of the voltage of the electrical network 1, whether the electrical network 1 is an AC electrical network or a DC electrical network, the response time of the sensors being compatible with the required detection delay (for example, less than or equal to one millisecond). Thus, the measurement passband of these sensors is generally between 0 Hz and 1 kHz, or between 0 Hz and a few kHz. The measurement of the energy in this frequency range is sufficient to detect most of the faults, in particular series arcs or parallel arcs, with the required response capacity.

[0112] In the case of an alternating AC electrical network with active electrical equipment, source or load, the energy determined by the measurement of the direct current component of the current and of the voltage can prove that there is a fault in the operation of this equipment. It is also possible to protect the power transformer from the magnetic saturation caused by these direct current components. In the case of an alternating AC electrical network with IT type (insulated) grounding, the measurement of the direct current component also makes it possible to locate the first defects as described above.

[0113] The sensors can also be suitable for providing an accurate measurement of the voltage and of the current in the frequency of the electrical network, in order to detect faults of the overconsumption type or insulation defects. The sensors can also operate beyond the frequency, in a very high frequency range beyond 100 MHz. This is particularly suitable for detecting defects of the partial discharge type in the insulation of the electrical network conductor.

[0114] Detection device

[0115] Having stated the basic principles of the present application, now, a detection device D according to the present application will be described in detail, as shown in Figure 5 Fig. 1. As already stated with reference to the description of Fig. 1, such a detection device D is suitable for being connected to the power conductors C1, C2 and to the common conductor Cc of an electrical network 1 and at the level of a measurement zone of this electrical network 1. These power conductors can be those forming the lines L of the electrical network 1 or, preferably, those inside an electrical equipment E of the electrical network. In this case, the measurement members O1, O2 of the detection device D are preferably placed upstream of the terminals B of the distribution lines L connecting the sources to the electrical network and preferably downstream of the terminals B connecting the loads to these lines L. In this way, it is possible to detect and locate defects in these terminals B.

[0116] In the simplest version of the detection device, the detection device D is designed to detect at least faults of the series type, thus configured to elaborate a first quantity V representative of the mixed energy transmitted in the measurement zone and during a given observation period.

[0117] To this end, the detection device D comprises a first measurement member O1 coupled to at least some of the conductors, so as to be able to elaborate a first quantity V res representative of the common-mode voltage, i.e. the residual voltage, of the power conductors C1, C2. Thus, the first member O1 can comprise a sensor of the voltage present on each power conductor C1, C2 with respect to the common conductor Cc. In a later part of the present description, several preferred embodiments of this first member O1 will be given.

[0118] The detection device D also comprises a second measurement member O2 coupled to at least some of the conductors, so as to be able to elaborate a second quantity I net representative of the network current. As an example, this second member O2 can comprise 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 measurements provided by these sensors representing the second quantity I net . In some cases, a single current sensor can be provided to measure only one quantity on one of these conductors, this quantity being understood as the network current and thus as a first approximation of the second quantity I net .

[0119] Advantageously, the current sensor(s) of the second measurement member are Hall effect sensors, Neel a sensor, or a sensor comprising a resistive shunt, to extract the direct current component of the measured current. It can be provided that one or more current sensors of the second member comprise a Rogowski type sensor or an air transformer. These types of sensors have an extended passband, linearity and stability, which can be used during the measurement of non-direct current spectral components. This is especially true in the case of studying defects of the partial discharge type.

[0120] Regardless of the nature of the components used to implement the first measuring member Ol and the second measuring member 02, the first measuring member Ol and the second measuring member 02 are able to directly or indirectly, i.e. by means of a calculator UP which will be presented hereinafter, formulate quantities I net and V representing the residual voltage res In the measuring area of the detection device D defined by the position of the detection device D in the electrical network, these two quantities are able to create an image of the hybrid energy E mix transmitted in a determined observation period. To this end, the detection device D also comprises a calculator UP connected to the first measuring member Ol and to the second measuring member 02. This calculator UP can take any suitable form, but preferably, the calculator UP is a digital calculator, the inputs of which are able to digitize the analog measurements provided by the measuring members Ol, 02 at a high frequency. This calculator can be implemented by a microcontroller, an FPGA, a DSP, an ASIC or any other form of suitable digital or analog calculator.

[0121] Optionally, the detection device D can comprise a converter CON, as shown by the dotted line in Figure 5 adapted to draw energy from the power connectors Cl, C2 and / or the common connector Cc, to power the calculator UP and all the other active elements constituting the device D, it being understood that the power required is reduced, in particular. When the detection device D is designed to be connected to a communication bus BUS, as shown in figure 1, the detection device D can alternatively be powered by a dedicated port of this bus.

[0122] For completeness, but not as an essential feature, the detection device can also comprise a network controller NET, which can be implemented by the calculator UP, and which is able to connect the device D to a 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 electrical network. The bus BUS allows the transmission of clock information to the calculator UP, or the device D can have a dedicated clock terminal able to receive this information. In this way, the calculator UP can time-stamp the formulated data, which is then placed on the communication bus BUS. In this way, as we have seen, the quantities I Figure 5The detection devices D shown are connected to a monitoring device V which can order the data received from these devices D and use them in a chronologically coherent sequence.

[0123] The calculator UP of the detection device D is configured, by hardware or software, to acquire the measurements provided by the first and second measuring members Ol and 02 and to determine the image of the hybrid energy E j mix transmitted in the measurement region during a given period of observation j. The frequency at which the calculator acquires the measurements is generally less than one millisecond, for example, it can be of the order of 100 microseconds or 10 microseconds, or even 100 ns or less, depending on the passband of the measuring members Ol, 02. The period of observation can be between 100 ns and 10 s. It is provided that the calculator UP can be configured to process the measurements provided by the measuring members Ol, 02 digitally, or that the calculator UP can be configured to combine a plurality of measurements provided by each of these members Ol, 02 to determine the image of the hybrid energy E j mix . For example, when the sensors of the members Ol, 02 provide information proportional to the time derivative, the calculator can be configured to integrate the measurements provided. When one of the two measuring members Ol and / or 02 provides a direct current / voltage measurement and a variation measurement of this current / voltage alone, the calculator can be configured to add these two measurements (after integrating them).

[0124] The calculator UP can also be configured to use the determined hybrid energy E j mix to detect a fault of series type in the electrical network, as discussed in the previous part of the description. In particular, it can be determined whether this determined hybrid energy E j mix or the variation of this energy between two different periods of observation exceeds a predetermined threshold. As we have seen, the calculator can be configured to sum the determined hybrid energies E j mix , E j+1 mix ..., E j+n mix over successive periods of observation j, j+1,..., j+n. The accumulated hybrid energy is then compared with a threshold to determine the occurrence of a fault.

[0125] When such a fault is confirmed, the calculator uses one or more hybrid energy measurements E j mix, the calculator UP can generate a signal S indicating this fault, which can be transmitted to the detection terminal of the device D. In this case of using a detection device D, it is understood that there is not necessarily a communication bus BUS. Alternatively, the signal S can be placed on the communication bus BUS. Alternatively, the calculator UP can simply, by calculation, make data representative of the hybrid energy E j mix and place this data on the communication bus BUS. In this last alternative, the detection of the fault in the electrical network is entirely implemented by the monitoring device V as introduced previously.

[0126] In a more complete embodiment of the detection device D, the detection device D can comprise other measurement means, or more completely, a first measurement means O1 and a second measurement means O2, so that the calculator UP can determine, in addition to the image of the hybrid energy E j mix , the image of the electrical network energy E j net transmitted in the measurement zone and the image of the residual energy E j res in the determined observation period j. In addition to the second quantity I net representative of the electrical network current and the first quantity V res representative of the residual voltage, these means can create a third quantity V net representative of the electrical network voltage and a fourth quantity I res representative of the residual current. This more complete embodiment can be represented by the dotted arrows V net and I res in Figure 5 .

[0127] Detection device integrated in an active device

[0128] The detection device D can be integrated in an electrical installation E comprising a load or an active source, for example an inverter, or a generator whose correct operation is to be monitored. In this case, in order to be able to detect a series arc, the detection device D will be placed as close as possible to the active part of the installation E, i.e. just before the power switch, downstream of the connection terminals B of this installation, and downstream of the possible protection device P when this installation E is a load. Preferably, a resistive voltage divider bridge is placed between the power conductors C1, C2, the midpoint of which is connected to the common conductor closest to the active load. The hybrid energy can be measured, i.e. the image of the presence of a series type defect in the internal conductors of the installation E being monitored.

[0129] In the same way as we try to distinguish the energy in the electrical network, we can try to distinguish the energy consumed by the load. To do this, we can define 4 types of energy:

[0130] • the energy called "useful energy" which is characterized by the current-voltage spectrum at the grid frequency, between 0 and 10 Hz for a DC grid, and the grid frequency ± 5 Hz for an AC grid.

[0131] • the harmonic distortion energy which is characterized by the current-voltage spectrum in the frequency band at several times the grid frequency ± 5 Hz (for an AC grid). This energy is essentially reactive.

[0132] • the switching energy which is characterized by the current-voltage spectrum at several times the chopping frequency FHACH of the active load. This energy is limited in the frequency band at several times the chopping frequency n*FHACH ± 5 Hz.

[0133] • additional energy not located in any of the above frequency bands. In the case of an arc (series arc or parallel arc) or short circuit, only a priori noise or energy is found in this frequency band.

[0134] As introduced in the previous part of the description, the detection device D integrated in the electrical equipment E will create the grid energy E net , the residual energy E res and the hybrid energy E mix , for example to transmit this information to the monitoring device V. In addition, the detection device D is able to decompose these energies according to the four categories described above, to identify the terms that contribute. To do this, the detection device D can apply filtering to the quantities provided by the measurement members Ol, 02, to separate these quantities according to the various frequency bands described, then calculate the energy in each frequency band by means of the calculator UP.

[0135] This filtering can implement a comb filter implemented by the calculator UP, to be able to constrain the frequency of the comb filter, notably by the chopping frequency. To do this, it can be provided that this chopping frequency is provided in the form of a chopping clock FHACH produced by the active load, and displayed on a dedicated connection terminal of the detection device (as shown in Figure 5 .

[0136] Thus, we can create, by means of the calculator UP:

[0137] - the grid energy "useful E net " as the useful energy in the load or source. This energy can exhibit an overload or a parallel arc.

[0138] - the grid energy "switching E net " as the energy lost in the switching structure of the electrical equipment E. This energy can exhibit a switching fault, for example a short circuit in the arm (without taking into account the dead time) or a switch fatigue.

[0139] - the grid energy "additional E net " as additional energy due, for example, to a parallel arc or a series arc or a short circuit.

[0140] - the hybrid energy "switching E mix " which represents the switching fault in a more refined manner than using only the hybrid energy E mix . In particular, the presence of a series arc in the device E can be identified by eliminating the switching hybrid energy from the hybrid energy E mix .

[0141] These energies can be placed on the communication bus BUS and transmitted to the monitoring device V to be used.

[0142] Preferred embodiment of the first measuring means

[0143] To ensure detection and localization of faults, in particular of series arcs in an alternating current grid or a direct current grid, as we have seen, it can be sufficient to measure the residual voltage V res and the direct current component of the grid current I net . These measurements are performed by the first measuring member Ol and the second measuring member 02 of the detection device D, respectively.

[0144] To measure the direct current component of the common mode voltage, i.e. the residual voltage V res , the first measuring member Ol can be equipped with a resistive voltage divider bridge, whose first electrode Tl is electrically connected to the first power conductor Cl, whose second electrode T2 is electrically connected to the second power conductor C2, and whose third electrode T3 is electrically connected to the midpoint of the bridge. Between this midpoint, related to the third electrode T3, and the common conductor CC, the voltage formed by the measuring dipole SH provides the common mode voltage. Typically, this dipole is formed by resistors. Figure 10 A schematic of this bridge is shown, in which the resistors Rl, R2 forming the bridge are chosen precisely to have the same value (deviation of the value within 1%, or even within 0.1%, or even within 0.01%), and to limit the drift of the resistors Rl, R2 over time and temperature to a minimum. In this solution, the quantity V res representing the common mode voltage is equal to the common mode voltage present on the two power conductors multiplied by a gain equal to SH / [Rl / 2 + SH]. This gain is able to reduce the dynamic range of the measured value to adapt it to the dynamic range of the electronics of the measuring member. By way of illustration, by choosing Rl = 1 MΩ and SH = 50 kΩ, a gain equal to 1 / 11 is able to reduce a common mode voltage of 50 V on the power conductors to a quantity V res representing approximately 5 V, so that it can be processed by the remaining electronics of the measuring member. The values of the resistors Rl, R2 and SH should be chosen to adapt to the number of grids and to the dynamic variations of the measuring electronics.

[0145] 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.

[0146] The resistance voltage divider, for example, can consist of thin-layer (or thin-film) resistors or thick-layer (or thick-film) resistors, thus being able to ensure sufficient voltage resistance and control the voltage transformation ratio, without generating thermal or time drifts. In order to ensure perfect symmetry between the two resistance elements R1, R2, thus reducing the drifts over time and temperature, resistance dividers known as "three-terminal unit" dividers are used to form these resistance elements.

[0147] When the non-DC component of the residual voltage is selected to be measured, it is preferable that the sensor that implements this measurement is not sensitive to possible DC components, is perfectly linear, has a gain that is controlled and does not drift over time or temperature. This is particularly true for the detection of defects of the partial discharge type. To this end, in the preferred embodiment shown in Figure 6 schematically in Fig. 1, it is proposed to use two capacitive elements EC1, EC2 arranged in the bridge between the two power conductors C1, C2, which have substantially the same capacitance value, with a deviation of 1 %, or even 0.1 %, or even 0.01 %. These elements are connected at the midpoint M, respectively. The midpoint M is electrically connected to the common conductor Cc by means of the measurement dipole SH of the common-mode voltage.

[0148] The currents I1, I2 flowing in the capacitive elements EC1, EC2 are proportional, respectively, to the derivative (as a function of time) of the potentials V c1 , V c2 carried by the power conductors C1, C2. The capacitive elements EC1, EC2 have the same capacitance value, and the differential current I1 - I2 is proportional to the derivative of V c1 + V c2 , i.e. of the common-mode voltage V res . It is therefore sufficient, for example, to measure this differential current I1 - I2 by means of a current sensor arranged in the circuit branch that connects 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, in order to obtain the residual voltage V res . To this end, the measurement dipole SH placed between the midpoint M and the common conductor Cc is part of the current sensor, with a low impedance of less than 1 kΩ, or even less than 1 Ω. As shown in Figure 6 , the integration does not necessarily take place analogously in the first measurement member, the calculator UP being configurable to perform this operation.

[0149] Alternatively, the common-mode voltage Vres The non-direct current component of the non-direct current component of the residual voltage V

[0150] To ensure perfect symmetry between the two capacitive elements EC1, EC2, and thus to reduce the drift over time and temperature, these capacitive elements are formed using capacitors called "three-terminal unit capacitors".

[0151] Such a capacitor comprises an A-type electrode, a B-type electrode and a G-type electrode ( Figure 7 ), each type of electrode being associated with one terminal unit, each type of electrode being stacked with each other and insulated from each other by a dielectric, following an alternating manner A, G, B, G, A, G, B, etc. The electrode G of the capacitor is directly the midpoint M, which is connected to the common conductor Cc by the measurement dipole SH, the A-type electrode and the B-type electrode being connected to the power conductors C1, C2 respectively by the three terminal units of the capacitor. The advantage of this structure is to have almost identical capacitive elements EC1, EC2, on the one hand between the G-type terminal unit and the A-type terminal unit, which do not vary over time and are temperature stable, and on the other hand between the G-type terminal unit and the B-type terminal unit, which do not vary over time and are temperature stable. The three-terminal unit capacitor also has a very low parasitic inductance, which makes it possible to make measurements at very high frequencies.

[0152] The dielectric of the capacitor can be a C0G type or NPO type dielectric. The capacitor can also use a paper-based dielectric, possibly filled with oil or mica or other insulator, thus making it possible to obtain excellent performance at high frequencies, stable over time, suitable for medium or very high voltages.

[0153] The capacitor can be a thin film capacitor, in which each type of conductor and dielectric is in the form of a thin film and is stacked with each other. This stack can be rolled up to form a cylindrical or parallelepiped three-terminal unit capacity.

[0154] Of course, these concepts can be extended to form a capacity with more than three terminal units, which can be useful for example when the electrical network is a three-phase electrical network.

[0155] Advantageously, it can be provided that, in addition to creating the residual voltage V res (i.e. common mode voltage), the first measurement means O1 are also able to create the electrical network voltage V net (i.e. differential mode voltage). For example, depending on the electrical network voltage Vnet The characteristics of the spectral components of the voltage V

[0156] Figure 11 A resistive voltage divider bridge is shown with 4 resistors R1, R1 ', R2, R2' and 5 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 a midpoint voltage corresponding to the common-mode voltage between the two power conductors. Thus, 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 with respect to the midpoint. The complementary electrodes T4, T5 are arranged at the level of the intermediate points that make the series connection of the resistors in each bridge branch, thus making it possible to provide an image of the network voltage V net by controlling the gain (defined by the relationship (R1 +R1 ') / (R1 +R1 '+R2'+R2)). Thus, the voltage drawn between the complementary electrodes T4, T5 is compatible with the rest of the processing operated by the electronic acquisition chain. For example, if the network voltage V net is approximately 800 V, we can choose the resistances of the bridge so that the gain is approximately 1 / 100.

[0157] For example, the two resistive elements R1, R2 can be chosen equal to each other, for example between 10 kΩ and 1 MΩ, and equal to 99 times the first resistance R1'connected to the midpoint T3. Another resistance R'2 is also chosen connected to the midpoint on the other side of this point, so that the other resistance R'2 has the same value as the first resistance 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 ).

[0158] Thus, by way of preference, the resistive bridge is implemented by a single component of the paired resistive divider type, i.e. in which the values of certain resistors are fixed a priori according to a predetermined ratio with respect to the other resistors, and in which all the resistors are carried on the same support ("thick film" or "thin film") in order to reduce thermal drift. The result is that the resistive divider has 3-terminal units or 5-terminal units depending on the embodiment chosen.

[0159] In the case of measurement of non-DC components, in order to improve performance in harsh environments, it is sufficient to be aware of the image of the derivative (as a function of time) of the common-mode current I1 +I2 flowing in the two capacitive elements EC1, EC2 of the capacitive divider shown in Figure 6 , which forms the differential-mode voltage V net . This differential-mode voltage V is able to be created by a first measuring member O1 equipped with a common-mode current sensor.net This common-mode current sensor can be formed by two air coils, for example two Rogowski probes, arranged respectively in the vicinity of the capacitive elements EC1, EC2.

[0160] Then, Figure 7 An implementation example of these principles is shown. A cylindrical three-terminal unit capacitor has been formed from A-type film, B-type film, G-type film wound as previously described, and the three terminal units T1, T2, T3 of the capacitor are electrically connected respectively to the first power conductor C1, to the common conductor and to the second power conductor C2 by means of a dipole SH. The electrical resistance of the measuring dipole SH between the terminal unit T2 (forming the midpoint M between the two capacitive elements EC1, EC2 in the capacitor) and the common conductor C is able to extract the quantity V res As previously described. Two Rogowski-type current sensors RG1, RG2 are arranged in the winding around the cylindrical capacitor to draw an image of the currents I1, I2 flowing in the capacitor. The quantities provided by these sensors can be combined to give an image of the differential-mode voltage V net .

[0161] In an advantageous embodiment, the current sensors able to make an image of the differential-mode voltage V net and / or of the common-mode voltage V res implement the planar coil technique. In this case, two types of coil can be implemented arranged in parallel but in different planes, to be able to measure respectively the common-mode current (image of the derivative of the differential-mode voltage V net ) and the differential-mode current (image of the derivative of the common-mode voltage V res ). These two planes can be positioned in different layers of a multilayer printed circuit board, in which the planar coils are positioned.

[0162] As Figure 8a , Figure 8b indicated, this printed circuit board can comprise on a first layer two tracks P1, P2 electrically connected respectively to the power conductors C1, C2. These tracks are also connected to the three-terminal unit capacitor C3, the point M of the capacitor C3 being electrically connected to the common conductor Cc by means of a measuring dipole SH (here formed by a single conductor) to form a differential current. The planar coils for measuring the differential current Bcd, for example four such coils consisting of two pairs of coils mounted in anti-series ( Figure 8a ), can be placed on a second layer of the circuit board, and the planar coils for measuring the common current Bcc (which can also be four coils) can be placed on a third layer of the circuit board ( Figure 8b ).

[0163] This variant has the advantage of being able to eliminate the effect of the current flowing in the common conductor, whatever the frequency of the current. 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 is performed. This assembly is preferably performed according to printed circuit board technology applied to electrical power, in order to control the geometry of the coil and to obtain a known transformation ratio without calibration, with very low drifts over time and temperature. It should be noted that this method can generally be implemented as a measurement of the differential voltage V net or of the common-mode voltage V res .

[0164] In general, the measuring member O1 can be equipped with sensors for the direct and variable components of the common-mode voltage V res and of the differential voltage V net .

[0165] Of course, the application is not limited to the described embodiments and alternative embodiments can be implemented without departing from the scope of the application as defined by the claims.

[0166] Thus, a device D according to the application is provided, in order to formulate a quantity representative of the hybrid energy E mix obtained from the common-mode voltage and the network current and transmitted in the measuring zone. This quantity is processed and compared with a threshold in order to identify a fault. It is entirely conceivable that the quantity representative of the hybrid energy can correspond to the common-mode voltage, which is compared with a threshold modulated according to the intensity of the network current. In all cases, the first and second quantities constituting the hybrid energy E mix are used to generate a signal S indicating a network fault. Thus, while the formal energy calculation constitutes a particular embodiment, the detection method according to the application does not necessarily perform a formal energy calculation.

Claims

1. A device for measuring and representing common-mode voltage (V) res A measuring component (O1) for measuring the quantity of a power grid (1) or a device (E), the power grid (1) or the device (E) comprising at least a first power conductor (C1) and a second power conductor (C2), the measuring component (O1) comprising two capacitive elements (EC1, EC2) arranged in a bridge between the first power conductor (C1) and the second power conductor (C2) and having the same capacitance value, the two capacitive elements (EC1, EC2) connected at a midpoint (M), the measuring component (O1) further comprising a measuring dipole (SH) connected on one side to the midpoint (M) and on the other side to a connection terminal intended to be electrically connected to a common conductor (Cc) provided to the power grid (1) or the device (E).

2. The measuring component (O1) according to claim 1, wherein, The measuring dipole (SH) has an impedance of less than 1 kΩ and is capable of generating a common-mode voltage (V) between the first power conductor (C1) and the second power conductor (C2). res The voltage is proportional to the time derivative of the voltage.

3. The measuring component (O1) according to claim 1, wherein, The measuring dipole (SH) has an impedance greater than 1 kΩ, and the measuring dipole (SH) generates a common-mode voltage (V) between the first electric conductor (C1) and the second electric conductor (C2). res A voltage that is proportional to the voltage.

4. The measuring component (O1) according to any one of claims 1 to 3, wherein, The two capacitor elements (EC1, EC2) are formed by three-terminal capacitors, with the first terminal intended to be electrically connected to one of the first power conductor (C1) and the second power conductor (C2), the second terminal intended to be electrically connected to the other of the first power conductor (C1) and the second power conductor (C2), and the third terminal intended to be connected to the common conductor (Cc).

5. The measuring component (O1) according to claim 4, wherein, The three-terminal capacitor is made of only three electrodes.

6. The measuring component (O1) according to claim 4, wherein, The three-terminal capacitor is made by stacking sheets and then rolling them up to form a cylinder or a three-terminal parallelepiped.

7. The measuring element (O1) according to any one of claims 1 to 3, further comprising a three-electrode resistor having a midpoint, the first electrode being intended to be electrically connected to the first power conductor (C1), the second electrode being intended to be electrically connected to the second power conductor (C2), the common-mode voltage (V res It exists between the midpoint of the three-electrode resistor and the common conductor (Cc).

8. The measuring element (O1) according to any one of claims 1 to 3, comprising a current sensor capable of measuring the differential-mode current flowing in the two capacitive elements (EC1, EC2) to create an expression representing the common-mode voltage (V). res The current sensor is formed by at least four air coils respectively arranged near the two capacitive elements (EC1, EC2).

9. The measuring element (O1) according to any one of claims 1 to 3, further comprising a current sensor capable of measuring the common-mode current flowing in the two capacitive elements (EC1, EC2) to create an expression representing the differential-mode voltage (V). net ) amount.

10. The measuring component (O1) according to claim 9, wherein, The current sensor capable of measuring the common-mode current is formed by at least two air coils respectively arranged near the two capacitive elements (EC1, EC2).

11. The measuring element (O1) according to any one of claims 1 to 3, further comprising a method for measuring the common-mode voltage (V). res A sensor for the DC component of a sensor.

12. The measuring component (O1) according to claim 9, further comprising a method for the differential mode voltage (V) net A sensor for the DC component of a sensor.

13. An apparatus (D) for detecting faults in a power grid (1), the power grid (1) comprising at least one electrical device (E) electrically connected to a first power conductor (C1) and a second power conductor (C2), the power grid further comprising a common conductor (Cc), the apparatus (D) being intended to connect to the first power conductor (C1), the second power conductor (C2), and the common conductor (Cc) at a measurement area, and the apparatus (D) comprising: - A first measuring element, wherein the first measuring element is a measuring element (O1) according to any one of claims 1 to 12; - Second measuring component (O2), used to generate a second quantity (I) net ), the second quantity (I) net ) represents the grid current flowing through the first power conductor (C1) and the second power conductor (C2); A calculator, connected to the first and second measuring components, is configured to determine, within a defined observation period, a representation of the mixed energy (E). mix The amount of the mixed energy (E) mix ) is defined as the integral of the product of the common-mode voltage and the grid current over the defined observation period and transmitted within the measurement region, according to a first quantity (V res ) and the second quantity (I) net ) determines the mixed energy (E) mix The quantity mentioned above.

14. The apparatus (D) according to claim 13, wherein, The second measuring component (O2) includes an air coil.

15. The apparatus (D) according to claim 14, wherein, The air coil is a Rogowski type air coil.

16. The apparatus (D) according to claim 14 or 15, wherein, The second measuring component (O2) also includes a DC sensor.

17. The apparatus (D) according to claim 16, wherein, The DC sensor is Neel sensor.

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