Early detection of arc flash

Abstract

This invention relates to a method for early detection of electric arc flash. A system for detecting discharges in electrical equipment is disclosed, comprising a first metal conductor and a second metal conductor, spaced apart from each other and configured to have an electric potential between them. The system also includes a third metal conductor placed between the first and second conductors. A current-current connection electrically connects the third conductor to the first conductor via a resistor. The system further includes a detection unit for detecting current flow through the current-current connection caused by a discharge through the gap between the second and third conductors.

Description

Technical Field

[0001] This invention relates to the detection of discharges in electrical equipment, particularly in high-current electrical systems such as electric vehicle power supply equipment (EVSE) used for charging electric vehicle batteries. Background Technology

[0002] DC chargers have been developed for high-current charging of traction batteries with high operating voltages. One reason for this is that, especially for high-current charging, it is uneconomical to equip every vehicle with a high-power inverter. As the rated power increases, such inverters become expensive, large, and heavy, and require increased cooling. Therefore, AC chargers are currently limited to low charging power, typically 11 to 22 kW from a wall box, and in some cases up to around 45 kW. This is generally insufficient for fast-charging batteries in trucks or other large vehicles.

[0003] To achieve rapid charging of truck traction batteries, the MCS (Megawatt Charging System) was developed. Employing a new MCS plug specification, the MCS can allow DC charging power up to 3.75MW. For example, it can operate at voltages up to 1250V with a maximum charging current of 3000A.

[0004] MCS charging equipment is designed to charge large batteries, such as those used in trucks, buses, or potentially aircraft in the future, to ensure short charging times and thus reduce potential vehicle downtime.

[0005] These enormous charging capabilities present numerous challenges. Repeated charging processes and battery replacements put stress on the metal connections that carry the charging current. For example, insufficient metal connections in the charging plug cable can cause overheating due to power loss caused by the transition resistance between the cable connection and conductors, resulting in contact resistance.

[0006] Overheating at the junction area (and possibly at other points) can now lead to the generation of flue gas. This flue gas may reduce the dielectric strength of the gas surrounding the high-voltage components (typically the ambient atmosphere).

[0007] This example illustrates that, under adverse conditions, arcing can occur between high-voltage components, such as conductors carrying charging current in an EVSE. Uncontrolled discharges or arcs can cause serious damage. Therefore, a reliable method is needed to detect potential discharges early and shut down the system in a timely manner.

[0008] Current solutions include temperature sensors near the conductor. However, this only detects potential sources of interference at the sensor's location. Other potential sources of smoke can only be detected after dielectric discharge has occurred. However, installing sensors at every possible smoke-generating location within the charging unit is highly impractical. Current solutions may also include optical or radiation sensors to detect smoke particles in the air. However, these methods are more expensive and have inherently limited lifespans, and therefore may be impractical in some products.

[0009] Therefore, the purpose of this disclosure is to provide an improved, reliable and economical detection mechanism that can detect the risk of potential electric arc (dielectric discharge) within electrical equipment. Summary of the Invention

[0010] To address the above and other potential problems, embodiments of this disclosure propose the following: In a first aspect of this application, a system for detecting discharges in electrical equipment is disclosed. The system includes a first metallic conductor and a second metallic conductor. The conductors are spaced apart from each other and configured to have an electrical potential between them. The system also includes a third metallic conductor that can be placed between the first and second conductors. The system further includes a current connection electrically connecting the third conductor to the first conductor. This current connection can be provided by a current limiter (e.g., a resistor) and a detection unit for detecting current flow through the current connection caused by discharge through the gap between the second and third conductors, particularly current flow through the current limiter.

[0011] In a second aspect, an electric vehicle power supply device (EVSE) is disclosed. The power supply device includes the system described herein.

[0012] In a third aspect, a method is disclosed for operating a system as described herein for detecting discharges in electrical equipment. The method can operate the system and includes: detecting current flow through a current-current connection (e.g., a current limiter) caused by a discharge through a gap between second and third conductors; and generating a dielectric breakdown signal when a discharge is detected. Attached Figure Description

[0013] The embodiments disclosed herein will be presented by way of example, and their advantages will be explained in more detail below with reference to the accompanying drawings, in which: Figure 1 An illustration showing the current situation; Figure 2 Illustrations of embodiments according to this application are shown; and Figure 3 Another embodiment according to this application is shown. Detailed Implementation

[0014] In the following description, illustrative embodiments will be presented. It should be understood that these embodiments are given only to enable those skilled in the art to better understand and further practice this disclosure, and are not intended to limit the scope of this disclosure. Furthermore, features shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. In addition, for clarity, not all features actually implemented are described in this specification.

[0015] Figure 1 The conditions, as previously known from prior art charging systems, are schematically illustrated. Two current-carrying conductors are arranged at a distance from each other. Conductors 1 and 2 are typically mounted in a housing (not shown), which may be cooled and / or ventilated or hermetically sealed. The housing is filled with a dielectric gas, such as ambient atmosphere. In a non-limiting example, the conductors belong to an EVSE for DC charging of a vehicle.

[0016] Conductors 1 and 2 can form current connections to corresponding phases of a charging cable (not shown). These current connections can be designed as threaded, crimped, welded, or similar connections. These current connections can be heat sources during operation. For example, during vehicle charging, conductors 1 and 2 carry high DC voltages. Under certain adverse conditions, the high voltage potential between them could cause a discharge (represented by a symbolic lightning bolt) between the two conductors.

[0017] Figure 2 A system for detecting discharges in electrical equipment according to this disclosure is shown. The system includes a first metallic conductor 1 and a second metallic conductor 2. These conductors are spaced apart from each other. Furthermore, they can be configured to have an electrical potential between them. Even though the primary application may be DC charging, in principle, the application could also be applied to AC chargers.

[0018] The third conductor 3 is disposed between the first conductor 1 and the second conductor 2. The third conductor 3 can be arranged such that it (dielectric ground) is closer to the second conductor 2 than the first conductor 1. In particular, the third metallic conductor 3 can be placed and positioned relative to the second conductor with a gap having a dielectric breakdown voltage lower than that between the first conductor 1 and the second conductor 2.

[0019] The third conductor 3 is electrically connected to the first conductor 1 via a current-current connection (e.g., resistor 4). Due to the current-current connection, the first conductor 1 and the third conductor 3 have approximately the same potential (before breakdown).

[0020] Dielectric breakdown in the system typically results in an electric arc in the spark gap between conductors (corresponding "capacitor plates") 2 and 3, such as Figure 2 The arc symbol is shown in the diagram. This arc generates current through a current-limiting connection, such as through a current limiter like resistor 4.

[0021] The current flowing through the current-current connection can be measured by a detection unit. The detection unit can be arranged within the system. The detection unit can be configured to detect the current flow through the current-current connection caused by a discharge through the gap between the second and third conductors. The discharge may be caused, in particular, by the potential between the second conductor 2 and the third conductor 3.

[0022] The detection strategy according to the embodiment can be described as being based on (limited) current discharge detection (e.g., partial discharge detection). This limited current discharge detection indicates that dielectric breakdown is imminent between the second and third conductors. In particular, limited current discharge detection involves monitoring for small discharges occurring in the insulating material (in this case, air). Such discharges may be early indicators of impending insulation weakness or impending voltage flashover. These discharges can generate high-frequency signals or electromagnetic emissions and can be detected by the detection unit 6.

[0023] These discharges can be detected with the aid of detection unit 6—for example, by sensors such as high-frequency current measuring devices, acoustic emission sensors, or electrical pulse sensors. The measured signals can then be used by detection unit 6 to assess whether a breakdown has occurred.

[0024] Therefore, the capacitor-like arrangement between conductors 2 and 3 utilizes the understanding that an insulating capacitor (here: a capacitor formed by the second conductor 2 and the third conductor 3) exhibits a small, incomplete breakdown (pre-discharge) as it approaches its breakdown level due to the change in the insulating capacity of the air (similar to a capacitor plate) between conductors 2 and 3, which can serve as a warning signal.

[0025] In a clean environment, as can be assumed within the casing of a trouble-free charging device, air possesses sufficiently good dielectric strength. Nevertheless, the residual conductivity of air may allow a small number of charged particles (such as ions or electrons) to pass through the air under a high electric field (even below breakdown)—this is known as leakage current. For example, the dielectric strength of dry air at direct current (DC) and atmospheric pressure is approximately 3000 V / mm. Factors such as humidity, impurities or dust, or potentially generated fumes, can significantly increase the conductivity of the atmosphere surrounding a conductor, potentially reducing dielectric strength and increasing leakage current. Figure 2 The system of this embodiment allows for the detection of dielectric breakdown long before it may occur between other and potentially safety-related components, by inducing and detecting a diagnostic dielectric breakdown between conductors 2 and 3. According to this embodiment, the system is configured to shut off the high-voltage power supply or disconnect the electric vehicle (EV) when the detection unit 6 detects a dielectric breakdown between conductors 2 and 3.

[0026] Figure 3 The illustrated embodiments generally correspond to Figure 2 The embodiments in, and Figure 2 The description also applies to Figure 3 Furthermore, in Figure 3 In this configuration, an insulating element 5 is arranged between the first conductor 1 and the third conductor 3. The insulating element can delay breakdown between the first conductor 1 and the second conductor 2. Therefore, the threshold time for detecting impending breakdown between the third conductor 3 and the second conductor 2 is increased. In other words, the insulating element delays breakdown to such an extent that breakdown between the second and third conductors is likely to occur some time before an arc could form between the first and second connectors.

[0027] Other aspects of the invention are described. Next, other possible aspects of the invention will be described. Each of these aspects may be combined with any other aspect of this disclosure. Although the following description includes reference numerals, these are for illustrative purposes only, and any aspect may be combined with any other aspect, regardless of the other details shown in the figures.

[0028] In an embodiment of this application, a system for detecting discharges in electrical equipment is disclosed. The system includes a first metal conductor 1 and a second metal conductor 2. These conductors 1 and 2 may be spaced apart from each other. Figure 2 Furthermore, conductors 1 and 2 can be configured to have an electric potential between them. This potential may be due to different DC voltages or different AC phases carried by conductors 1 and 2.

[0029] Even though the invention is not limited to electric vehicle charging, in embodiments, at least one of conductors 1 and 2 can form a current connection with the corresponding polarity of the charging cable. The current connection can be a threaded connection, crimped connection, welded connection, or similar connection.

[0030] The system also includes a third metal conductor 3 placed between the first conductor 1 and the second conductor 2. In one aspect, the third metal conductor 3 can be positioned and positioned relative to the second conductor with a gap having a lower dielectric breakdown voltage than that between the first conductor 1 and the second conductor 2. Specifically, the lower breakdown voltage may be due to the shorter distance between the second conductor 2 and the third metal conductor 3 relative to the distance between the first conductor 1 and the second conductor 2.

[0031] According to one aspect, the arrangement of conductors 2 and 3 can be described as a spark gap arrangement, i.e., two metal surfaces with a fixed distance and a dielectric (e.g., ambient air) between them. According to one aspect, insufficient dielectric strength and / or dielectric breakdown can be determined by detecting finite current discharges in this spark gap, i.e., by monitoring small, possibly incomplete discharges (pre-discharges) in the dielectric between conductors 2 and 3. Such finite current discharges may be an early indicator of impending insulation weakness or impending voltage flashover (potentially before complete breakdown occurs). These discharges generate high-frequency signals or electromagnetic emissions that can be detected by detection unit 6.

[0032] According to one aspect, the detection unit 6 may include at least one sensor configured to measure (partial) discharge events between conductors 2 and 3—for example, a high-frequency measuring device, an acoustic emission sensor, or an electrical pulse measurement. The measured signal can then be used to assess whether a fault may have occurred. In particular, the detection unit 6 may include a current sensor adapted to detect the current flowing through resistor 4, thereby indirectly measuring voltage changes in conductor 3. Thus, by monitoring the current through resistor 4, even a discharge can be detected.

[0033] In a clean environment, as can be assumed within the casing of a fault-free charging device, air possesses sufficiently good dielectric strength. Nevertheless, the residual conductivity of air may allow a small number of charged particles (such as ions or electrons) to pass through the air under high electric fields (even below breakdown)—this is known as leakage current. For example, the dielectric strength of dry air at direct current (DC) and atmospheric pressure is approximately 3000 V / mm. Factors such as humidity, impurities or dust, or potentially generated fumes, can significantly increase the conductivity of the atmosphere surrounding the conductor, potentially reducing the dielectric strength and increasing leakage current. In this regard, the threshold used to determine (pre)discharge is set above the non-critical leakage current.

[0034] According to one aspect, the capacitor-like arrangement between conductors 2 and 3 utilizes the effect of an insulating capacitor exhibiting a small, incomplete breakdown (pre-discharge) as it approaches its breakdown level. This is due to the change in the insulating capacity of the air between conductors 2 and 3 (similar to a capacitor plate), which can serve as a warning signal. According to another aspect, dielectric breakdown between conductors 2 and 3 is detected.

[0035] According to one aspect, a current-current connection can be arranged in the system and configured to electrically connect the third conductor 3 to the first conductor 1 via a current limiter 4 (e.g., in the form of a resistor). Due to the current-current connection, the first conductor 1 and the third conductor 3 have the same potential before breakdown. This ensures that dielectric breakdown occurs between conductor 2 and the diagnostic conductor 3 (dielectric ground), which is arranged closer to conductor 2 than conductor 1, before dielectric breakdown occurs between conductors 1 and 2. This dielectric breakdown can be detected before any damage occurs to other parts of the device.

[0036] According to one aspect, the aforementioned dielectric breakdown may result in a current flowing through the current-connected junction. Charge migration between conductors (correspondingly "capacitor plates") 2 and 3 causes conductor 3 to discharge. This migrated charge is compensated by a low but detectable current flowing through the current-connected junction of current limiter 4 (e.g., a resistor).

[0037] According to one aspect, the current is measured by detection unit 6. Detection unit 6 can be arranged in the system and, for example, can be integrated with resistor 4. Detection unit 6 can be configured to detect the current flow through the current-current connection caused by a discharge in the gap between the second and third conductors. The discharge may be caused, in particular, by the potential between the second conductor 2 and the third conductor 3.

[0038] The detection unit 6 can be configured to send a wireless or wired signal to the service station or maintenance personnel when a discharge is detected.

[0039] The detection unit 6 can also be configured to adapt to different conditions within the housing. As mentioned earlier, air is a good insulator, and its breakdown voltage is 3 kV / mm under normal conditions of dry air. However, even under these conditions, even with a very low current, some charge can migrate between conductors 2 and 3, generating a measurable current.

[0040] In humid air, since charging stations can also be set up in public places, even if a thermal accident does not produce smoke, charge migration may be stronger and trigger false alarms.

[0041] Therefore, the detection unit 6 can be configured to periodically determine a limit value based on environmental conditions (such as humid air due to rain, very dry air in summer or a very cold winter, etc.), above which a possible breakdown is detected. This calibration can be performed automatically at a set time or when a change in environmental conditions is detected. This may reduce the risk of false alarms.

[0042] In principle, the detection device can be designed to detect the current caused by the migration of charged particles, which can be triggered in particular by smoke particles.

[0043] On the other hand, an electrical insulating element can be placed between the first and third conductors. The insulating element can be arranged in the system to improve discharge behavior. Additional insulating elements can ensure that an initial (or first) discharge occurs between the third and second conductors.

[0044] This arrangement ensures a time delay in breakdown between the first and second conductors. Therefore, the breakdown path between the second and third conductors has more time to react in advance, thus more safely preventing dangerous breakdown between the first and second conductors.

[0045] On the other hand, electrical equipment can be an electric vehicle power supply device (EVSE). In particular, vehicle power supply devices may be suitable for installing batteries in electric vehicles with high power demand, such as trucks or other electric vehicles with high power demand.

[0046] In another aspect, the detection unit 6 can be configured to generate a dielectric breakdown signal to deactivate the power supply when a current flow through the resistor is detected, the current flow indicating a discharge between the second and third conductors.

[0047] The detection unit 6 can also be designed such that when a possible breakdown is detected, it reduces or cuts off the power supplied to conductors 1 and / or 2.

[0048] Furthermore, the charging process or energy transfer can be terminated, rather than being deactivated.

[0049] In yet another embodiment that can be combined with other embodiments, the third metal conductor 3 may be sheet-like. The third metal conductor may be arranged parallel to the first conductor. Preferably, the third conductor may have a smaller surface area than the first conductor, and the surface area of ​​the third conductor is preferably at most 50% of the surface area of ​​the first conductor. The surface of the third conductor may have an effect on the discharge behavior, and it can be predetermined when the conductor arrangement of conductors 2 and 3 (or better yet, detection unit 6) determines breakdown or, within a certain range.

[0050] In some embodiments, the third conductor may be in the form of a tip, thereby influencing the form of the electric field between the third and second conductors. For example, the shape of the third conductor can be used to generate a tip effect, which can be used to shift the timing of discharges to an appropriate range (e.g., before diagnostic values ​​and / or other discharges occur in more critical parts of the device).

[0051] In another embodiment, which can be combined with other embodiments, the system may further include a sealed compartment. The first, second, and third conductors may be arranged within the sealed compartment and protected from moisture. The compartment may be airtight.

[0052] In some embodiments, the housing may be ventilated to dissipate heat from the housing during charging. If the detection unit 6 detects that a breakdown is about to occur or has already occurred between conductors 2 and 3, ventilation measures (such as a fan) may be used to ventilate the housing to remove particulate contamination (such as smoke) and reduce the risk of breakdown.

[0053] The detection unit 6 can also be configured to send a message or alarm to the maintenance department with service personnel in this situation.

[0054] In yet another embodiment that can be combined with other embodiments, the rated voltage difference between the first and second conductors is at least 800V, preferably at least 1200V.

[0055] In another embodiment, an electric vehicle power supply device (EVSE) is disclosed, which may include a system according to one of the foregoing embodiments.

[0056] In another embodiment, the EVSE according to another embodiment of the present disclosure may include electrical arrangements or systems that may be arranged within the housing of the EVSE.

[0057] In another embodiment of this disclosure, the EVSE, according to other embodiments, can be configured to provide at least 1 MW of charging power to the charging connector. In particular, the EVSE may be suitable for charging batteries in trucks or other vehicles.

[0058] In another embodiment, which may be combined with other embodiments, a method for detecting discharges in electrical equipment is disclosed.

[0059] In a method for detecting discharges in electrical equipment, the corresponding electrical equipment may include: a first metal conductor and a second metal conductor, the first and second metal conductors being spaced apart from each other and having an electrical potential between them, a third metal conductor placed between the first and second conductors, and a current-current connection electrically connecting the third conductor to the first conductor via a current limiter. The current limiter may be provided in the form of a resistor.

[0060] A method for detecting discharge may include the following steps: detecting current flow through a current-current connection caused by a discharge through a gap between a second and a third conductor, and generating a dielectric breakdown signal when a discharge is detected.

[0061] The detection of the current flow through the current connection and the resistor can be performed by the detection unit 6, which can be a discharge indication. The detection unit 6 can also generate a dielectric breakdown signal.

[0062] In another embodiment, which can be combined with other embodiments, the method may further include shutting off the power supply or disconnecting the electric vehicle (EV) upon detection of a discharge. The shutdown can be performed via the detection unit 6. According to an embodiment, the system is configured to shut off the high-voltage power supply or disconnect the electric vehicle (EV) when the detection unit 6 detects dielectric breakdown between conductors 2 and 3.

[0063] In yet another embodiment that may be combined with other embodiments, the method may include an electrical device, namely an electric vehicle power supply device (EVSE).

[0064] In summary, the application disclosed herein facilitates early detection of faults in high-current charging systems, particularly MCS charging systems, that may be caused by heat-generated fumes or conductive particles. The proposed system can operate in parallel with other fault detection systems, such as temperature sensor control systems. The proposed system can also be used as a simple, inexpensive standalone solution.

Claims

1. A system for detecting discharges in electrical equipment, the system comprising: A first metal conductor (1) and a second metal conductor (2), the first metal conductor (1) and the second metal conductor (2) being spaced apart from each other and configured to have an electric potential between them; A third metal conductor (3) is placed between the first conductor and the second conductor; A current-limiting device (4) is used to electrically connect the third conductor to the first conductor. as well as The detection unit (6) is used to detect the current flow through the current connection caused by the discharge through the gap between the second metal conductor (2) and the third metal conductor (3).

2. The system according to claim 1, wherein, The electrical equipment mentioned is the electric vehicle power supply equipment EVSE.

3. The system according to claim 1 or 2, wherein, An electrical insulating element (5) is disposed between the first conductor (1) and the third conductor (3).

4. The system according to any one of the preceding claims, wherein, The detection unit is configured to generate a dielectric breakdown signal to shut down the power supply when the current flow is detected.

5. The system according to any one of the preceding claims, wherein, The third metal conductor (3) is sheet-shaped and arranged parallel to the first conductor, and preferably, the third conductor has a smaller surface area than the first conductor, the surface area of ​​the third conductor being at most 50% of the surface area of ​​the first conductor.

6. The system according to any one of the preceding claims further includes a closed compartment, wherein, The first conductor, the second conductor, and the third conductor are arranged within the enclosed compartment and / or within the compartment wall of the enclosed compartment.

7. The system according to any one of the preceding claims, wherein, The rated voltage difference between the first conductor and the second conductor is at least 800V, preferably at least 1200V.

8. An electric vehicle power supply device (EVSE) comprising the system according to any one of the preceding claims.

9. The EVSE according to claim 8, wherein, The electrical equipment is housed within the enclosure of the EVSE.

10. The EVSE according to claim 8 or 9, wherein, The EVSE is configured to provide at least 1MW of charging power to the charging connector.

11. A method for operating a system for detecting discharges in electrical equipment, wherein the system comprises: A first metal conductor and a second metal conductor, spaced apart from each other and having an electric potential with each other. A third metallic conductor is placed between the first conductor and the second conductor, and A current connection is established by electrically connecting the third conductor to the first conductor via a resistor. The method includes: The current flow through the current-current connection caused by the discharge through the gap between the second conductor and the third conductor is detected, and When the flow of the current indicating the discharge is detected, a dielectric breakdown signal is generated.

12. The method of claim 11, further comprising: Power is shut off when a discharge is detected.

13. The method according to any one of claims 11 to 12, wherein, The electrical equipment mentioned is the electric vehicle power supply equipment EVSE.

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