METHOD AND SYSTEM FOR DETECTING RESISTANCE IN AN ELECTRICAL CONNECTION

Abstract

System and method for monitoring an electrical connection and detecting a failure condition of said electrical connection defined by an electrical resistance value exceeding a predetermined threshold. The electrical system comprises means for determining the temperature (TC) of the electrical connection and means for determining the current (IC) flowing through the electrical connection. The method comprises: acquiring, over time, successive values ​​of the temperature of the electrical connection and successive values ​​of the current (IC); calculating the Joule heating contribution as the average of [IC(t)]²; calculating a temperature gradient (GTC) of the connection; calculating a relative temperature gradient, defined as the ratio of the temperature gradient of the connection to the Joule heating contribution; and triggering an alert if the relative temperature gradient exceeds a threshold value. Figure 4

Description

Title of the invention: METHOD AND SYSTEM FOR DETECTING RESISTANCE IN AN ELECTRICAL CONNECTION

[0001] The invention relates to a method and a system for monitoring an electrical connection and detecting a fault condition consisting of excessively high resistance in this electrical connection.

[0002] Here, electrical connection means a physical interface between two conductive elements, namely either a connection surface allowing two members to be electrically connected directly, or a connection element allowing two members to be electrically connected indirectly, the connection element being interposed between the two members.

[0003] Too high a resistance for an electrical connection through which significant electrical currents pass leads to significant local heating. This leads to the creation of a hot spot, or even a very hot one, which can locally cause material damage, even leading to the start of combustion.

[0004] Therefore, it is important to monitor that the electrical resistance of each electrical connection, supporting significant electrical currents, complies with the expected values ​​recommended by the design and validation tests.

[0005] For entities manufactured in large series, such as motor vehicles, it may happen that due to a manufacturing defect, or an assembly defect, or due to degradation in service of an electrical connection, on a particular example of vehicle, the resistance observed is (or becomes) higher, or even much higher, than the electrical resistance expected for the nominal electrical connection, which creates an undesirable hot spot as soon as a significant current flows through the electrical connection.

[0006] It is known to estimate the resistance of an electrical connection by measuring the voltage drop across its terminals and knowing the current flowing there, by applying Ohm's law R=(U1-U2) / I.

[0007] However, we are interested in electrical connections having a very low nominal electrical resistance. Therefore, the voltage drop across its terminals is small and difficult to measure in practice, being a few tens of millivolts in typical service.

[0008] Furthermore, in some electrical connections, the current flows at one time in one direction and at another time in the opposite direction, which complicates much the voltage measurement at the terminals which can be positive or negative from the reading point of view.

[0009] Furthermore, it has already been proposed in document FR3051558 to measure the temperature in the vicinity of the electrical connection, using a thermoelectric model. However, it turns out that this solution may lack reactivity with respect to a fault that occurs quite suddenly.

[0010] The aim of the invention is to overcome at least certain drawbacks of the prior art by proposing a method for monitoring an electrical connection, in particular its electrical resistance.

[0011] To do this, the invention thus relates, in its broadest sense, to a method implemented in an electrical system, for monitoring at least one electrical connection and detecting a failure condition of said electrical connection, the failure condition being defined by an electrical resistance value of the electrical connection being greater than a predetermined threshold, the electrical system comprising means for determining a temperature of the electrical connection, the electrical system comprising means for determining a current IC flowing through the electrical connection, characterized in that the method comprises the steps: - a step of acquisition (a), over time, of successive values ​​of the temperature of the electrical connection, and of successive values ​​of current IC, - a calculation step (b), from the successive values ​​of the current, of a Joule effect contribution as the average of [IC(t)]2 over a first monitoring time window, consequence of the passage of the current, in absolute value, having crossed the electrical connection during the first monitoring time window, - a calculation step (c), from the successive temperature values, of a time gradient of the temperature of the electrical connection, over a second monitoring time window, - a step (d) of calculating a relative time gradient, defined as the ratio of the time gradient of the temperature of the electrical connection to the contribution of Joule effect, steps (b) to (d) being iterated and the first and second time windows being sliding time windows, - a step of triggering (e) an alert if the relative temporal gradient is or becomes greater than a predetermined threshold value.

[0012] Thanks to these provisions, in the event of a drift in the electrical resistance of the electrical connection, an alert can be triggered very early, without waiting for the area of ​​the electrical connection to reach a very high temperature. An action to reduce the current flowing in the connection can then be undertaken to avoid excessive heating.

[0013] The inventors noted that it was more relevant to focus on the temperature time gradient rather than the temperature value itself. Indeed, the temperature value can be affected by external conditions, whereas a rapid increase in temperature is necessarily linked to a thermal input by Joule effect due to the current flowing through the electrical connection.

[0014] Advantageously, the consequence of the Joule effect is cleverly used to detect abnormally high electrical resistance through temperature measurement and monitoring, reliably and without having to measure extremely small voltage differences.

[0015] Note that the joule effect contribution AEJ is a quantity expressed in Joule per ohm (J / Q).

[0016] It is noted that the current can flow through the electrical connection in both directions, but by taking the absolute value of the current, we faithfully take into account the heating of the electrical connection.

[0017] The method therefore seeks to determine an abnormal increase in temperature beyond the increase expected due to the inevitable existence of the Joule effect.

[0018] The electrical connection releases calories to its environment due to convective, conductive and radiative exchanges, which allows for equilibrium or cooling. In the absence of current or under low current, cooling causes a negative temperature gradient which does not interfere with the progress of the process stated above.

[0019] In alternating current, we work on the effective value of the current.

[0020] The first and second time windows can be chosen according to the desired precision on the sampling of the current value and the thermal inertia of the electrical connection as will be seen later.

[0021] It should be noted that the term “electrical system” means an electrical and / or electronic system.

[0022] Advantageously, according to one option, the means for determining the temperature are formed by a thermal camera. Image processing of the images captured by the thermal camera is carried out by a computer. On an area of ​​the image, a color (i.e. wavelength) is representative of a temperature captured at this location (e.g. at the location of the electrical connection). The variations in color (i.e. wavelength) from one image to another are noted and denote a temporal gradient.

[0023] It is noted that the use of a thermal camera operating remotely proves to be non-intrusive; it is not necessary to install an element in contact with the electrical connection to be monitored.

[0024] According to one option, the method can monitor several electrical connections, monitored simultaneously.

[0025] Several areas of interest are selected in the images captured by the thermal camera, each area corresponding to an electrical connection to be monitored. Thus, with a single device, the method makes it possible to monitor several electrical connections simultaneously.

[0026] Advantageously, the means for determining a temperature are formed by a thermistor or a thermocouple in intimate thermal coupling with the electrical connection.

[0027] The thermistor or thermocouple may be in direct contact with the electrical connection or a thermal adhesive may be provided between the thermistor or thermocouple and the electrical connection itself.

[0028] The thermistor or thermocouple can be glued to the connection element (lug, nut, tab, or other, whatever the form taken by the connection element of interest). The thermistor can be of the NTC (negative coefficient) or PTC (positive coefficient) type. The electrical diagram necessary for a proper reading of such a resistance with positive or negative coefficient is simple and reliable. For example, a Wheatstone bridge can be used in the calculator for each input connected to a thermistor.

[0029] In this configuration, each electrical connection to be monitored can be equipped with a thermistor or a thermocouple and a computer can monitor a plurality of electrical connections, simultaneously and independently. The installation of the thermistor at the appropriate location on the electrical connection requires only a pair of wires or even a single wire and a single location for the thermistor, whereas conversely, to measure a potential difference as in the prior art, it is necessary to install a potential tap at a first location upstream and a potential tap at a second location downstream, and a more complex wire route.

[0030] Advantageously, it is provided that the second monitoring time window is identical to the first monitoring time window. Whereby the solution implemented is simple from an algorithmic point of view.

[0031] According to one option, the second time window has the same duration as the first time window, but is shifted slightly in time to take into account thermal inertia of the component in which the Joule effect occurs.

[0032] These two time windows are sliding and evolve / advance in the same way with time. Their length can be between 200ms and 2s. The length can be adjusted depending on the nature of the electrical component to be monitored forming the electrical connection.

[0033] The second time window can be shifted, here delayed, relative to the first time window by a configurable duration of, for example, a few tens of milliseconds or even a few hundreds of milliseconds.

[0034] The invention also relates to a control system in an electrical system of a motor vehicle, the electrical system comprising an on-board computer configured to monitor at least one electrical connection and detect a failure condition of said electrical connection, the electrical system comprising means for determining a temperature of the electrical connection and means for determining a current IC flowing through the electrical connection, the on-board computer being configured to implement the method as described above.

[0035] According to one option, the means for determining the temperature are formed by a thermal camera. It is noted that the use of a thermal camera operating remotely proves to be non-intrusive, it is not necessary to install an element in contact with the electrical connection to be monitored.

[0036] Image processing of the images captured by the thermal camera is carried out by a computer. On an area of ​​the image, a color (i.e. wavelength) is representative of a temperature captured at this location (e.g. at the location of the electrical connection).

[0037] According to one option, the means for determining a temperature are formed by a thermistor or a thermocouple in intimate thermal coupling with the electrical connection.

[0038] The thermistor or thermocouple may be in direct contact with the electrical connection or a thermal adhesive may be provided between the thermistor or thermocouple and the electrical connection itself.

[0039] The thermistor or thermocouple can be glued to the connection element (lug, nut, tab, or other, whatever the form taken by the connection element of interest). The thermistor can be of the NTC (negative coefficient) or PTC (positive coefficient) type. The electrical diagram necessary for a proper reading of such a resistance with positive or negative coefficient is simple and reliable. For example, a Wheatstone bridge can be used in the calculator for each input connected to a thermistor.

[0040] According to one option, the on-board computer monitors several electrical connections, monitored simultaneously. This is true for both the thermal camera solution and the contact thermistor or thermocouple solution.

[0041] The invention also relates to an electrically powered vehicle comprising at least one electric traction motor and a main battery, the monitored electrical connection forming part of an electrical circuit interposed between the main battery and the traction motor, the vehicle comprising at least one control system as described above.

[0042] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates an electrical system in which the present invention is implemented, in a version with a capture element in contact with the connection; - [Fig.2] schematically illustrates an electrical system in which the present invention is implemented, in a version with a thermal camera; - [Fig.3] schematically illustrates a battery module with cells interconnected by jumpers; - [Fig.4] illustrates a timing diagram showing the evolution of certain parameters representative of the behavior of an electrical connection and the calculation of time gradient; - [Fig.5] schematically illustrates a soldered connection; - [Fig.6] schematically illustrates a screwed connection; - [Fig.7] schematically illustrates a double jumper connection; - [Fig.8] schematically illustrates a decision graph with the current on the abscissa and the temperature gradient on the ordinate; - [Fig.9] schematically illustrates the steps of the process; - [Fig. 10] schematically illustrates an electric traction system in an electric or hybrid vehicle; - [Fig.l 1] schematically illustrates sliding time windows of calculation.

[0043] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the description, certain elements are not necessarily represented to scale.

[0044] In the following presentation, two solutions are proposed for monitoring the evolution of the temperature at the level of the electrical connection, a first so-called “contact” solution illustrated in [Fig.l] and an imaging-based solution, therefore without contact, illustrated in [Fig.2].

[0045] With reference to [Fig.l], three identical electrical connections 1 are shown. Each electrical connection in question is symbolically represented by a male / female coupling, but we will see other configurations later. Each electrical connection is equipped with a thermistor 2. More generally, any element whose resistive characteristic varies with its temperature may be suitable. In particular, a thermocouple, a variable resistor with a positive coefficient (PTC) or a variable resistor with a negative coefficient (NTC) may be chosen.

[0046] It is noted that the electrical connections discussed here may be electrical connections installed on board a motor vehicle. However, the present invention may also apply to electrical connections that are not installed on board a motor vehicle.

[0047] Each thermistor is connected to a computer 5, by a pair of conductors. Alternatively, a single wire may be sufficient to connect a thermistor to the computer if the other pole of the thermistor can be connected locally to the vehicle ground.

[0048] With reference to [Fig.2], three identical electrical connections 1 are also shown. The electrical connections 1 are here of the same type as those shown in [Fig.l], but without a thermistor or thermocouple.

[0049] An imaging camera 3 is installed with a field of view that encompasses the three electrical connections of interest. Said imaging camera 3 can be installed on board a motor vehicle, and be part of the normal equipment of this vehicle.

[0050] However, this camera configuration may be of particular interest when the imaging camera is installed in the factory at the end of the motor vehicle assembly line to participate in testing and verification operations before declaring each motor vehicle fit for service. In this case, the camera is used as a means external to the vehicle during the testing operations; it is not part of the delivered vehicle.

[0051] The camera configuration can also be used to perform a connection check on a subset of battery cells, or to perform a connection check on a complete battery module.

[0052] Camera verification can also be done through a translucent cover.

[0053] The imaging camera here is a thermal camera, each pixel of the captured image having a color, namely a wavelength, representative of the radiative emission temperature of the component in which the pixel of interest is located.

[0054] The camera is connected to a computer 5 which processes the images captured by the camera. The computer determines the temperature for each pixel, in particular for the pixels in the areas of interest of the image, around each electrical connection to be monitored.

[0055] The computer 5 may be an on-board computer forming part of the normal equipment of the vehicle. In the configuration of end-of-assembly line tests, the computer may be part of test equipment without being part of the vehicle itself.

[0056] [Fig. 10] illustrates an electric traction system in an electric vehicle or hybrid. There are a plurality of electrical power connections, a subset of which can be monitored by the method promoted here. The traction system comprises a battery 61, an electrical distribution box 62 which includes fuses 68 and power contactors 69.

[0057] At the output of the electrical distribution box 62, there are a certain number of electrical connections 63 for connecting said electrical connection box 62 respectively to: a front traction motor 64, a rear traction motor 65, an electrical sub-network 66 supplying a plurality of diverse and varied equipment of the vehicle, if necessary via a DC / DC converter, and a battery charging socket 67.

[0058] In [Fig. 3], a battery pack 7 is shown with six cells arranged next to each other and marked respectively 71, 72, 73, 74, 75 and 76.

[0059] A positive bus bar 80 is shown on the left, it is connected to the positive pole of the first cell by a connection element 81. The first cell is connected to the second cell by a connection element 82. The second cell is connected to the third cell by a connection element 83.

[0060] The third cell is connected to the fourth cell by a connection element 84. The fourth cell is connected to the fifth cell by a connection element 85. The fifth cell is connected to the sixth cell by a connection element 86.

[0061] A negative bus bar 88 is provided. The sixth cell is connected to the negative bus bar 88 by a connection element 87.

[0062] [Fig. 5] represents a soldered electrical connection in which two conductive elements are connected to each other by a solder 90. In the case of the presence of a thermistor, this can be glued to one or other of the conductive elements of the connection.

[0063] [Fig. 6] shows a screwed electrical connection 91. Two conductive elements are connected together by bolting. In the example illustrated, a screw 95 receives a screwed nut 98, this assembly here tightens the two conductive elements to be electrically connected. In another example, the screw comes directly from the vehicle body and forms a conventional ground point receiving a terminal and a screwed nut.

[0064] [Fig.7] represents a jumper 97 allowing two neighboring cells to be electrically connected in an electric accumulator module, the electrical connection 92 here is a double electrical connection. The jumper can be generalized to any connection element allowing two members to be indirectly electrically connected, the connection element being interposed between the two members.

[0065] We therefore see that the term electrical connection in this document covers a wide range of solutions, from a clip / tab pair, to screwed power terminals, including welded connections, screwed connections or prestressed connections.

[0066] One of the characteristics of interest of such a connection is the electrical resistance that it opposes to the passage of a significant current or even a high current. A perfect electrical connection would have zero electrical resistance, but in reality there is always a value, albeit small, of resistance to the passage of current in an electrical connection.

[0067] We are talking here about resistance values ​​between 1 micro-ohm and 1 milli-ohm (mQ). The type of electrical connection considered must not introduce a drop in significant voltage across its terminals even when a significant current flows through it. When we talk about significant current, we are talking about a current greater than 100 amps, which can go up to several hundred amps in a hybrid or electric vehicle application, without excluding currents exceeding 1000 amps.

[0068] It is therefore very important to ensure that the resistance of the electrical connection remains around its nominal value and does not increase for any reason.

[0069] The method promoted here is particularly interested in the temporal temperature gradient recorded on the electrical connection either by a camera or by a thermistor as explained above.

[0070] If we assimilate the electrical connection to a discrete physical element, then the following differential equation makes it possible to model the behavior of this physical element. M*CP* = r es^C 2 + BB tr \TE - TC)

[0071] In this equation, M is the mass of the electrical component, CP is the thermal capacity of the electrical component, TC is the current temperature of the electrical component, RES is the electrical resistance of the electrical component, and IC is the instantaneous current flowing through it.

[0072] In this equation, TE is an equivalent surrounding temperature, and BBlr is a transfer function indicative of a thermal convection and / or thermal conduction factor with respect to the environment. It is noted that there may be an additional component to account for radiative heat transfers.

[0073] [Fig.4] illustrates an example of a timing diagram of the behavior of a connection electrical depending on the current passing through it.

[0074] The bottom curve represents the current flowing through the electrical connection, the middle curve represents the temperature prevailing at the electrical connection, and the top curve represents the temperature time gradient, namely substantially the slope of the temperature curve TC.

[0075] Between times tl and t2, the current IC takes the value ICI. The curve of the estimated temperature TC, marked 44, shows an increase between said times tl and t2. The calculation of the time gradient gives a positive value, slightly decreasing between tl and t2 due to the slight inflection of the temperature curve.

[0076] Between times t2 and t3, the current IC is zero. During this phase, the temperature TC of the electrical connection decreases thanks to convective, conductive and radiative exchanges with the environment.

[0077] Between times t3 and t4, the current IC takes the value IC2, greater than ICI. During this phase, the temperature TC of the electrical connection increases more significantly, with a steeper slope.

[0078] Between times t4 and t5, the current IC takes the value IC3. The temperature TC of the electrical connection increases more slowly.

[0079] Beyond t5, the current IC is zero. During this phase, the temperature TC of the electrical connection decreases.

[0080] [Fig.4] also illustrates in phantom a case of failure of the same electrical connection. For the same current load conditions, it can be seen from curve 45 in phantom that the temperature of the connection increases much more quickly just after time t1. Concomitantly, the GTC temperature time gradient identified by line 47 is approximately twice as high as that of the normal case shown in curve 46.

[0081] To calculate the temperature time gradient, we start from the formula for the temperature derivative expressed as follows: GTC = [TC(t+dt)-TC(t)] / dt.

[0082] Moving into the digital domain, this gives GTC = [TC(tb)-TC(ta)] / [tb-ta] where ta is a first sampling instant and tb a second sampling instant, as illustrated in [Fig. 11]. This is step (c) of the method.

[0083] The calculator 5 iterates this calculation periodically.

[0084] For the calculation of the energy input, we are particularly interested in a quantity called "joule effect input" AEJ expressed in Joule per ohm (J / Q). In other words, it is a unit energy for an electrical resistance by convention of 1 ohm.

[0085] The current measurement is not necessarily sampled at the same time as the temperature measurement.

[0086] For the IC current, a measurement time window between two instants is also used.

[0087] The calculator performs a calculation of the average of the square of the current IC which can be formalized as follows: AEJ = 2 •

[0088] This is step (b) of the method. The number of samples can be chosen depending on the sampling period.

[0089] According to a first implementation, the same instants ta and tb are used for the calculation of the temperature time gradient as for the calculation of the Joule effect contribution.

[0090] As visible in [Fig. 11], according to another implementation, illustrated on the right part of the figure, the instants ta and tb are used for the evaluation of the contribution in Joule effect induced by the passage of the current, but for the calculation of the temporal temperature gradient a window is used which starts at the instant tm and ends at the instant tn, these instants being delayed by a value ôt with respect to the instants ta and tb.

[0091] This solution makes it possible to temporally match the contribution in Joule effect with the increase in temperature by taking into account the thermal inertia of the component forming the electrical connection.

[0092] From the GTC time gradient values ​​and the AEJ Joule effect contribution values, the relative time gradient can then be calculated, namely the ratio of the GTC1 time gradient of the connection temperature to the AEJ1 Joule effect contribution. This is step (d) of the method.

[0093] In other words, the calculator performs the following calculation: GTCR = GTC / AEJ, this ratio being representative of the electrical resistance that the electrical connection opposes to the passage of the current IC.

[0094] With reference to [Fig.8], the obtained value GTCR is compared to a normality threshold GTCvAEJO. If the result of the calculation of the relative time gradient is below the curve represented by a dashed line, GTCR is lower than GTCvAEJO. Otherwise, if the result of the calculation of the relative time gradient is above the curve represented by a dashed line, GTCR is higher than GTCvAEJO, and in this case an alert is triggered characterizing an abnormality of the electrical resistance of the electrical connection. This is step (e) of the method.

[0095] The GTCvAEJO normality threshold is a parameter that can be chosen depending on the type of electrical connection. In other words, the threshold is not the same for each electrical connection of interest.

[0096] When the relative time gradient is greater than the GTCvAEJO normality threshold then an alert is triggered, this produces at least a fault message stored in the computer memory. Optionally, an action to reduce the current flowing in the electrical connection can then be undertaken to avoid excessive heating of the electrical connection.

[0097] As visible in [Fig.8], to avoid false alerts, the system is designed not to trigger an alert when the temperature temporal gradients are small. For example, an abacus in the form of straight lines starting from a point GTC0 which represents a tolerance can be used. For example, a threshold value of positive temporal gradient GTC1 can be used below which, even if the GTC / AEJ ratio is large, an alert is avoided. Above GTC1, as soon as the GTC / AEJ ratio is larger than GTCvAEJO then an alert is triggered.

[0098] With reference to [Fig. 11], the first time window FT1 is represented on the bottom line, regarding the calculation of the Joule effect contribution AEJ, and the second time window FT2 is represented on the top line regarding the temperature TC.

[0099] In the example shown on the left of the graph, the second time window is identical to the first time window and extends temporally from a first terminal ta to a second terminal tb.

[0100] In the example shown to the right of the graph, the second time window is shifted to the right. The second window extends temporally from a first terminal tm to second terminal tn. The second time window is delayed, relative to the first time window, by a configurable duration, for example a few tens of milliseconds or even a few hundred milliseconds.

[0101] The length of the time windows can be between 200ms and 2s. The length can be adjusted depending on the nature of the electrical component to be monitored forming the electrical connection.

[0102] The offset δ between the two time windows can be between 100ms and 500ms, for example.

[0103] In the calculations, one can take into account the fact that the parameter TC evolves relatively slowly with time while the current IC can vary very quickly over time. It is therefore necessary to sample the current IC fairly quickly, unlike sampling on the temperature.

Claims

Claims

1. Method implemented in an electrical system, for monitoring at least one electrical connection (1) and detecting a failure condition of said electrical connection, the failure condition being defined by an electrical resistance value of the electrical connection being greater than a predetermined threshold, the electrical system comprising means for determining a temperature (TC) of the electrical connection, the electrical system comprising means for determining a current IC flowing through the electrical connection, characterized in that the method comprises the steps: - a step of acquiring (a), over time, successive values ​​of the temperature (TC) of the electrical connection, and successive values ​​of current IC, - a step of calculating (b), from the successive values ​​of the current, a Joule effect contribution (AEJ1) as the average of [IC(t)]2 over a first monitoring time window (FT1),consequence of the passage of the current, in absolute value, having crossed the electrical connection during the first monitoring time window, - a step of calculation (c), from the successive values ​​of the temperature, of a time gradient (GTC1) of the temperature of the electrical connection, over a second monitoring time window (FT2), - a step of calculation (d) of a relative time gradient, defined as the ratio of the time gradient (GTC1) of the temperature of the electrical connection to the Joule effect contribution (AEJ1), steps (b) to (d) being iterated and the first and second time windows being sliding time windows, - a step of triggering (e) an alert if the relative time gradient is or becomes greater than a predetermined threshold value (GTCvAEJO) of relative time gradient.,

2. Method according to claim 1, characterized in that the temperature determination means are formed by a thermal camera.

3. Method according to claim 2, characterized in that the method carries out monitoring of several electrical connections, monitored simultaneously.

4. Method according to claim 1, characterized in that the means of determination of a temperature are formed by a thermistor or a thermocouple in intimate thermal coupling with the electrical connection.

5. Method according to any one of claims 1 to 4, characterized in that the second monitoring time window (FT2) is identical to the first monitoring time window (FT1).

6. Electrical system comprising an on-board computer (5) configured to monitor at least one electrical connection (1) and detect a failure condition of said electrical connection, the electrical system comprising means for determining a temperature (TC) of the electrical connection and means for determining a current (IC) flowing through the electrical connection, characterized in that the on-board computer (5) is configured to implement the method according to any one of claims 1 to 5.

7. Electrical system according to claim 6, in which the temperature determining means are formed by a thermal camera.

8. An electrical system according to claim 6, wherein the means for determining a temperature is formed by a thermistor or a thermocouple in intimate thermal coupling with the electrical connection.

9. Electrical system according to one of claims 6 to 8, characterized in that the on-board computer monitors several electrical connections, monitored simultaneously.

10. An electrically powered vehicle, comprising at least one electric traction motor and a main battery, and a monitored electrical connection forming part of an electrical circuit interposed between the main battery and the traction motor, the vehicle comprising at least one electrical system according to one of claims 6 to 9.

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