Leak detection in cable assemblies

Abstract

A cable assembly includes a cable having a first end and a second end. The cable has an electrical conductor and a cooling conduit, wherein each of the electrical conductor and the cooling conduit extends from the first end to the second end. The cooling conduit is adapted to convey a fluid for cooling the electrical conductor. The cable assembly includes a leak detection module for detecting leakage of the fluid from the cooling conduit. The leak detection module includes a power supply for generating an input voltage signal applied to a first node in contact with the fluid. The leak detection module includes a controller for monitoring an output voltage signal at the first node and detecting leakage of the fluid from the cooling conduit based on the output voltage signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 936,254, filed on November 15, 2019, entitled “Leak Detection in Cable Assemblies,” which is hereby incorporated by reference in its entirety. Background Art

[0003] The advancement of electric vehicles has increased the demand for charging equipment that delivers power to the vehicle's rechargeable batteries. Some such applications, such as high-current fast-charging vehicle chargers, are designed to operate at continuous currents of 350 amps or greater. To deliver energy faster and reduce charging times, cable assemblies (including the cable and charging connector) must be able to withstand high current loads. Generally, the higher the current passing through the charging equipment, the more heat is generated.

[0004] To alleviate the problem of excessive heat generation, the cross-section of the current-carrying conductors can be increased to reduce losses. However, increasing this cross-section requires increasing the cable cross-section, which makes the cable difficult to handle. Alternatively, the cable assembly can include a cooling duct arranged near the conductors. The cooling duct can carry a coolant fluid, which can carry away some or all of the heat generated in the conductors. However, the presence of the coolant fluid in the cable assembly creates new problems. For example, the coolant fluid can leak from the cooling duct and can come into contact with the electrical conductors or shielding of the cable assembly. This can cause damage to the cable as well as to the charging device and the vehicle. Summary of the Invention

[0005] The present invention relates to a cable assembly. In one embodiment, the cable assembly includes a cable having a first end and a second end. The cable has an electrical conductor and a cooling conduit, wherein each of the electrical conductor and the cooling conduit extends from the first end of the cable to the second end. The cooling conduit is adapted to convey a fluid for cooling the electrical conductor. In this embodiment, the cable assembly includes a leakage detection module to detect leakage of the fluid from the cooling conduit. The leakage detection module may include a power supply to generate an input voltage signal applied to a first node in contact with the fluid. The leakage detection module includes a controller to monitor an output voltage signal at the node and detect leakage of the fluid from the cooling conduit based on changes in the detected output voltage signal.

[0006] In some embodiments of the present invention, a cable assembly having a fluid-cooled cable is provided. The cable has a first end and a second end. The cable includes one or more electrical conductors and a cooling conduit, wherein each of the electrical conductors and the cooling conduit extends from the first end to the second end. The cooling conduit is suitable for conveying a fluid that cools the electrical conductors. The cable assembly includes a connector attached to the second end of the cable. The cooling conduit forms a fluid channel around the interior of the handle of the connector and is suitable for cooling the connector. The cable assembly includes a leakage detection module connected to the cable and the connector. The leakage detection module includes a power supply to generate an input voltage signal, wherein the input voltage signal is applied to a first node in contact with the fluid. The leakage detection module includes a controller to monitor an output voltage signal at the first node and detect leakage of the fluid from the cooling conduit based on changes in the detected output voltage signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 Illustrated are exemplary connectors and cables as part of a cable assembly according to certain embodiments of the present disclosure.

[0008] Figure 2 An example of a leakage detection module for a cable assembly according to certain embodiments of the present disclosure is schematically illustrated.

[0009] Figure 3 Illustrated are exemplary voltage waveforms at various nodes of a leakage detection module according to certain embodiments of the present disclosure.

[0010] Figure 4 Illustrated are exemplary cross-sections of cable assemblies according to certain embodiments of the present disclosure.

[0011] Figure 5 Illustrated is a perspective view of a connector according to certain embodiments of the present disclosure.

[0012] The embodiments of the present disclosure and their advantages may be best understood by reference to the following detailed description. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the accompanying drawings, which are shown to illustrate embodiments of the present disclosure and not to limit the present disclosure. DETAILED DESCRIPTION

[0013] The following detailed description of embodiments presents various descriptions of specific embodiments of the present invention. However, the present invention can be implemented in many different ways. In this specification, reference is made to the accompanying drawings in which the same reference numerals represent identical or functionally similar elements. It should be understood that the elements shown in the drawings are not necessarily drawn to scale. Moreover, it should be understood that certain embodiments may include more elements and / or a subset of the elements shown in the drawings. Further, some embodiments may incorporate any suitable combination of features from two or more of the accompanying drawings.

[0014] In summary, one or more aspects of the present invention relate to a cable assembly that includes a leak detection module. Illustratively, the leak detection module can allow for the detection of leaks of coolant fluid in a cable assembly used to charge an electric vehicle. Upon detecting a leak, the leak detection module can alert a user, causing the user to stop using the cable to charge the vehicle. In some configurations, the leak detection module can automatically stop a power source connected to the cable assembly from supplying power to the cable. Thus, leak detection can help avoid failures in the cable assembly due to contact between the coolant fluid and the electrical conductors and improve the safety of using such a cable assembly. Although various aspects of the cable assembly have been described in the context of charging an electric or hybrid vehicle, the cable assembly can also be used in any other application area that can allow for the use of such a fluid-cooled cable.

[0015] Figure 1 An example of a charger assembly 100 is shown having a cable 102 extending transversely therethrough. Cable 102 may have at least one electrical conductor 104 configured to transmit electrical power. In some embodiments, cable 102 may terminate in a connector tip 106 connected to a connector housing 108 (a portion of which is removed herein for clarity). Connector tip 106 may be designed to be compatible with a power inlet and, therefore, may be configured according to one or more standards for electrical connectors. Cable 102 may form a connection between connector tip 106 and a power source (e.g., a generator or power grid). Cable 102 may have a first end and a second end, such that the first end of cable 102 is coupled to the power source and the second end is coupled to connector tip 106. In some embodiments, connector tip 106 and connector housing 108 may be manufactured as a single piece. In other embodiments, connector tip 106 and connector housing 108 may be manufactured as separate pieces.

[0016] A handle (not shown) may partially or completely enclose the connector tip 106 and / or the connector housing 108. The handle may also partially enclose the cable 102. The handle may be designed to be held by a person, such as when inserting the connector tip 106 into a power inlet and when removing the connector tip 106 from the power inlet.

[0017] In certain embodiments, the charger assembly 100 can be used to charge an electric vehicle or a hybrid electric vehicle. The electric vehicle may include an electric drive train (not shown) for propelling the vehicle on the ground. The electric vehicle may include an energy storage device (not shown) for supplying energy to the electric drive train for propelling the electric vehicle. The energy storage device may be a collection of one or more battery cells. In some embodiments, the energy storage device may be any other energy storage device that may be applicable to various aspects of the present disclosure. The electric vehicle may include a charging inlet configured to receive the connector tip 106 in an inlet or socket for charging the energy storage device. The charging inlet may be internally connected to the energy storage device so that electrical energy can be supplied to the energy storage device through the charging inlet. In some embodiments, the charging inlet may be interlocked with the connector tip 106 so that the cable 102 can be secured without support from personnel.

[0018] The cable 102 may include a cooling conduit 110. The cooling conduit 110 may be used to convey a fluid (e.g., a coolant) along the length of the conductor 104 to remove some or all of the heat generated by the electrical energy flowing within the conductor 104. Examples of such fluids or other heat transfer media may include, but are not limited to, water, air, oil, phase change materials, and other chemicals. For example, a non-degrading fluid with sufficient heat capacity may be selected to cool the conductor 104. The material used for the cooling conduit 110 may be selected based on its thermal conductivity, flexibility, and durability.

[0019] In some embodiments, the cooling conduit 110 can begin at the first end of the cable 102 at or near the power source and loop back at or near the connector tip 106 to return to the first end of the cable 102. In such embodiments, the cooling conduit 110 can be a single tube, so that the fluid travels along the same path in both directions. The fluid can be pumped from the first end of the cable 102 toward the connector tip 106, stored in an internal receptacle at or near the connector tip 106 until all the fluid is in the receptacle, and then pumped back from the connector tip 106 toward the first end of the cable 102. In other embodiments, the cooling conduit 110 can have a U-turn at or near the connector tip 106 to reverse the direction of the fluid flow. Through this and similar implementations, the cooling conduit 110 can provide continuous circulation cooling along substantially the entire length of the cable 102 and within the connector tip 106. In this way, the fluid can be returned to the system that provides the fluid, such as a reservoir in the cooling system. Thus, the fluid path can be circular, flowing toward the connector tip 106 on one side of the cable 102 and toward the reservoir on a different side of the cable 102. In some embodiments, the U-turn can occur outside the connector tip 106. For example, in an implementation where fluid is fed into an electric vehicle during charging to provide cooling during the charging operation, the fluid can exit the vehicle via the U-turn through the same connector tip 106. In other implementations, a one-way flow of fluid can be provided. For example, a connector tip 106 attached to the charging inlet of an electric vehicle (or other device) can also have a fluid inlet coupled to a fluid reservoir of the vehicle. In this way, the arrangement can be used to replenish the fluid in the vehicle's fluid reservoir. In other embodiments, the fluid can flow from the cable 102 into the vehicle and then return from the vehicle to the starting point of the cable.

[0020] Figure 2 A leakage detection system for a cable assembly 200 according to certain embodiments of the present disclosure is schematically illustrated. The cable assembly 200 may include a cable 202 having a cooling conduit 204 (shown in cross-section). The cable 202 may be covered by a grounded shield 206. The cable assembly 200 may include an electronic leak detection module 208 that is programmed and configured to detect leakage of fluid from the cooling conduit 204. The leak detection module 208 may monitor changes in one or more electrical properties of the fluid circulating in the cooling conduit 204 to detect leaks. For example, if the leaking fluid comes into contact with a low-pressure source (e.g., a grounded conductor or shield 206) or a high-pressure source (e.g., a high-voltage conductor), the fluid electrical properties may change.

[0021] Continue to refer Figure 2The leak detection module 208 may include a power supply 210 that generates an input voltage signal to be applied to the fluid. In some embodiments, the power supply 210 may generate an alternating current (AC) voltage signal that alternates between a maximum voltage (Vcc) and a minimum voltage (Vss). In other embodiments, the power supply 210 may generate a direct current (DC) voltage signal of a predetermined voltage. The input voltage signal may be generated by, for example, Figure 2 The resistor R1 shown is applied to the fluid. In some embodiments, the resistor R1 can be the impedance from a resistor. In other embodiments, the resistor R1 can be the impedance from other electrical components. To monitor the electrical properties of the fluid, one or more monitoring nodes 212, 214 can be defined at predetermined locations within the cooling conduit 204. When an input voltage signal is applied to the nodes 212, 214, the one or more monitoring nodes 212, 214 can contact the fluid and polarize the fluid. In contrast to using only a single monitoring node, using two nodes can improve redundancy and provide greater contact to polarize the fluid. However, it should be appreciated that within the scope of the present invention, only one node can be used, and two nodes are not required to monitor the electrical properties of the fluid. The positions of the monitoring nodes 212, 214 can be selected to create an optimal geometry for monitoring the electrical properties of the fluid while minimizing the distance between the nodes 212, 214. In some embodiments, only one of the monitoring nodes 212, 214 can be used to polarize the fluid and monitor the electrical properties of the fluid.

[0022] In some embodiments, a test node 216 ( Figure 2 ) to simulate the leakage of fluid via resistor R2. In some embodiments, resistor R2 can be the impedance from a resistor. In other embodiments, resistor R2 can be the impedance from other electrical components. Resistor R2 can be connected to one or more switches 218, 220, which allow resistor R2 to be alternately connected to leakage detection module 208 and ground. As described in detail herein, changing the resistor R2 connection can cause leakage detection module 208 to alternate between self-test mode and normal operation mode.

[0023] refer to Figure 2 The leakage detection module 208 may include a buffer 222 connected to the monitoring nodes 212, 214 and ground. The buffer 222 may monitor the output voltage signals at the nodes 212, 214. The impedance of the fluid may act as a voltage divider between the power supply 210 and the ground.

[0024] The leak detection module 208 may include a controller 224 to detect leakage of fluid from the cooling conduit 204. The controller 224 may receive an input voltage signal from the power supply 210. Furthermore, the controller 224 may receive an output voltage signal from a buffer 222. In some embodiments, the buffer 222 may be implemented within the controller 224. The controller 224 may determine a voltage associated with the output voltage signal, such as a peak-to-peak output voltage or a maximum output voltage. To detect a leak, the controller 224 may monitor the decay of the output voltage, the peak-to-peak output voltage, or the maximum output voltage of the output voltage signal. In some embodiments, the controller 224 may repeatedly calculate changes in the amplitude of the output voltage signal by calculating the difference between amplitudes measured after a fixed time interval (e.g., 5 seconds). When the measured amplitude (e.g., the peak-to-peak output voltage or the maximum output voltage) drops by more than a predetermined threshold voltage drop, the controller 224 may identify a leak. In one embodiment, the threshold may be selected to be sufficiently high so that even slight changes in the peak-to-peak voltage or the maximum voltage are not detected as fluid leaks.

[0025] The controller 224 can generate an indication of a leak for the user or operator of the cable assembly 200. The indication can be a visual indication, an audio indication, or a tactile indication. Upon receiving the indication, the user can stop transmitting power through the cable assembly 200 to avoid any failure and minimize the associated risks. In some embodiments, the controller 224 can automatically take action (e.g., stop charging the electric vehicle) when a leak is detected.

[0026] In some embodiments, the leak detection module 208 can operate in one of a self-test mode and a normal operation mode. Figure 2 As shown, switches 218 and 220 can be provided to switch between the self-test mode and the normal operating mode by changing the connection of the resistor R2. In the self-test operating mode, the controller 224 can open the switch 218 connecting the resistor R2 to the leakage detection module 208 and close the switch 220 connecting the resistor R2 to the ground line. Therefore, the test node 216 can be connected to the ground line via the resistor R2 to simulate a leak that causes the fluid to come into contact with the shield 206. Specifically, the resistor R2 can be connected in series with the impedance of the fluid, thereby causing the impedance perceived by the buffer 222 to increase. Due to the increase in impedance, the amplitude of the output voltage signal may be reduced compared to the amplitude in the normal operating mode. In another embodiment, the system can perform a self-test by closing the two switches 218 and 220. In this embodiment, the input of the buffer can be connected to the ground line, and the system can be allowed to confirm that the switches 218 and 220 are operating normally.

[0027] In normal operating mode, controller 224 can close switch 218 connecting resistor R2 to leak detection module 208 and open switch 220 connecting resistor R2 to ground. In normal operating mode, and when no fluid leaks are present, resistor R2 can be connected in parallel with the impedance of the fluid, and the impedance sensed by buffer 222 does not substantially change. As a result, the peak-to-peak voltage or maximum voltage associated with the output voltage signal can maintain a substantially constant level. Test node 216 can be removed from cable assembly 200 by opening both switches 218 and 220.

[0028] Figure 3 1 illustrates voltage signal waveforms in an exemplary embodiment of the present disclosure. Waveform 302 depicts the input voltage signal generated by power supply 210. Waveform 302 can alternate between a maximum voltage (Vcc) and a minimum voltage (Vss). Waveform 304 illustrates the output voltage signal at monitoring nodes 212, 214 in normal operating mode of leak detection module 208 when there is no fluid leakage. Waveform 306 illustrates the output voltage signal at monitoring nodes 212, 214 in the event of a leak. As described herein, the amplitude of the output voltage in a leak scenario may be less than the amplitude of the output voltage in a non-leak scenario. When the measured amplitude drops by more than a predetermined threshold voltage drop, leak detection module 208 can identify a leak. The threshold can be selected high enough so that subtle changes in the peak-to-peak voltage are not detected as fluid leaks.

[0029] Figure 4 An exemplary cross-sectional view of a cable assembly 400 showing multiple sets of conductors 402-404 and a cooling conduit 110 is illustrated in accordance with certain embodiments of the present disclosure. The cable assembly 400 may include a high voltage conductor 402, a low voltage conductor 404, and a cooling conduit 110 within a shield 206.

[0030] The high-voltage conductor 402 and the low-voltage conductor 404 can have one or more insulating materials that surround each other to provide electrical insulation. The cooling conduit 110 specifically has one or more channels inside to allow fluid to flow in at least one direction. Typically, the cooling provided by the cooling conduit 110 can allow the cable 102 to be made into an outer jacket 406 with a diameter smaller than otherwise possible. Further, the cable assembly 400 can include a ground conductor 408 and one or more additional components, such as signal cables and / or filler materials. For clarity, the cable components are shown as having a certain spacing from each other, wherein it should be understood that in some implementations, the components can completely fill the interior of the outer jacket 406.

[0031] like Figure 4As shown, the cooling conduit 110 can be placed proximate to the conductors 402, 404. Thus, the cooling conduit 110 can provide cooling to each of the conductors 402, 404.

[0032] Figure 5 An example of a leakage detection module 208 residing within connector 500 is shown. Leakage detection module 208 may include a printed circuit board assembly (PCBA) 502 thermally coupled to a high-voltage receptacle 508. In some embodiments, PCBA 502 is a two-part structure. A first portion 504 of the PCBA may be coupled to the high-voltage receptacle 508, such that the first portion 504 of the PCBA sits atop the electrical receptacle of the high-voltage receptacle 508. A second portion 506 of the PCBA may be connected to the first portion 504 of the PCBA via a rigid-flex PCB structure or other similar interconnect. The second portion 506 of the PCBA may accommodate auxiliary components, such as, but not limited to, a thermistor for temperature sensing applications. The two-part structure of PCBA 502 allows for more efficient routing of electrical wiring to each high-voltage receptacle 508. PCBA 502 may include various components of leakage detection module 208, such as power supply 210, buffer 222, and controller 224. In some embodiments, PCBA 502 may include one or more temperature sensors (not shown) for collecting temperature data associated with cable assembly 200. In some embodiments, wings 510 may be present around the manifold. Wings 510 may be made of a conductive material and increase the ground connection area for leak detection. Wings 510 may be part of PCBA 502, but are not required. The location of wings 510 may be selected based at least in part on where coolant is most likely to leak or collect in a faulty charger component.

[0033] The foregoing disclosure is not intended to limit the present disclosure to the precise forms or specific fields of use disclosed. Therefore, in view of the present disclosure, various alternative embodiments and / or modifications of the present disclosure are possible, whether or not explicitly described or implied herein. Having thus described the embodiments of the present disclosure, it will be appreciated by those skilled in the art that changes may be made in form and detail without departing from the scope of the present disclosure. Therefore, the present disclosure is limited only by the claims.

[0034] In the foregoing description, the present disclosure has been described with reference to specific embodiments. However, as will be appreciated by those skilled in the art, the various embodiments disclosed herein may be modified or otherwise implemented in various other ways without the spirit and scope of the present invention. Thus, this description should be considered illustrative and intended to teach those skilled in the art how to make and use the various embodiments of the disclosed cable assembly. It should be understood that the forms of disclosure shown and described herein should be considered representative embodiments. Equivalent elements, materials, processes, or steps may replace the elements, materials, processes, or steps representatively shown and described herein. Moreover, certain features of the present disclosure may be utilized without regard to the use of other features, all of which will be apparent to those skilled in the art after having benefited from this description of the present disclosure. Expressions such as "including," "comprising," "incorporating," "consisting of," "having," and "is" used to describe and claim the present disclosure are intended to be interpreted in a non-exclusive manner (i.e., allowing for the presence of items, components, or elements that are not explicitly described). References to the singular are also interpreted as relating to the plural.

[0035] Further, the various embodiments disclosed herein are to be understood in an illustrative and explanatory sense and should in no way be construed as limiting the present invention. All references in conjunction with (e.g., attaching, adhering, coupling, connecting, etc.) are intended only to help the reader understand the present disclosure and do not create limitations, particularly with respect to the position, orientation, or use of the systems and / or methods disclosed herein. Therefore, references in conjunction with (if any) are to be interpreted in a broad sense. Moreover, such references in conjunction with do not necessarily imply that two elements are directly connected to each other.

[0036] Additionally, all numerical terms such as, but not limited to, “first,” “second,” “third,” “primary,” “secondary,” “primary” or any other general and / or numerical terms should also be considered merely as identifiers to assist the reader in understanding the various elements, embodiments, variations and / or modifications of the present disclosure and shall not create any limitations, especially as to the order or preference of any element, embodiment, variation and / or modification with respect to or due to another element, embodiment, variation and / or modification.

[0037] It should also be appreciated that one or more of the elements depicted in the drawings may also be implemented in a more separate or integrated manner, or even removed or rendered inoperable in some cases, as may be useful depending on the particular application. Additionally, unless specifically stated otherwise, any signal hatching in the drawings should be considered as merely exemplary and not limiting.

Claims

1. A cable assembly comprising: an electrical cable having a first end and a second end, the electrical cable comprising an electrical conductor and a cooling conduit, wherein each of the electrical conductor and the cooling conduit extends from the first end to the second end, wherein the cooling conduit is adapted to convey a fluid that cools the electrical conductor; as well as a leakage detection module coupled to the cable, the leakage detection module comprising: a power supply generating an input voltage signal, wherein the input voltage signal is applied to the fluid at a first node within the cooling conduit and in contact with the fluid; as well as A controller is configured to monitor an output voltage signal at the first node and detect leakage of the fluid from the cooling conduit based on the output voltage signal.

2. The cable assembly of claim 1, wherein the fluid is electrically conductive. 3 . The cable assembly of claim 1 , wherein the cooling conduit is configured to transport the fluid from a first end to the second end and then from the second end to the first end. The cable assembly of claim 1 , wherein the input voltage signal is an alternating current (AC) voltage signal. 5 . The cable assembly of claim 1 , wherein the input voltage signal is also applied at a second node in contact with the fluid. 6 . The cable assembly of claim 1 , wherein the controller detects the leakage of the fluid when a peak-to-peak voltage drop of the output voltage signal exceeds a predetermined threshold voltage drop value. 7 . The cable assembly of claim 1 , wherein the controller detects the leakage of the fluid when a maximum voltage drop of the output voltage signal exceeds a predetermined threshold maximum voltage value.

8. The cable assembly of claim 1, wherein the controller further provides at least one of: a visual indication, an audio indication, or a tactile indication upon detecting the leakage of the fluid.

9. The cable assembly of claim 1, further comprising a connector attached to the second end of the cable, wherein the cooling conduit forms a fluid passage around an interior of a handle of the connector.

10. The cable assembly of claim 1, wherein the cable assembly is used to charge an electric vehicle from a power source. 11 . The cable assembly of claim 10 , wherein the controller automatically stops charging the electric vehicle upon detecting the leakage of the fluid.

12. A cable assembly comprising: an electrical cable having a first end and a second end, the electrical cable comprising an electrical conductor and a cooling conduit, wherein each of the electrical conductor and the cooling conduit extends from the first end to the second end, wherein the cooling conduit is adapted to convey a fluid that cools the electrical conductor; as well as a connector attached to the second end of the cable, wherein the cooling conduit forms a fluid passage around an interior of a handle of the connector and is adapted to cool the connector; as well as a leakage detection module coupled to the cable and the connector, the leakage detection module comprising: a power supply for generating an input voltage signal, wherein the input voltage signal is applied to the fluid at a first node within the cooling conduit and in contact with the fluid; as well as A controller is configured to monitor an output voltage signal at the first node and detect leakage of the fluid from the cooling conduit based on the output voltage signal.

13. The cable assembly of claim 12, wherein the cable assembly is used to charge an electric vehicle from a power source.

14. The cable assembly of claim 13, wherein the controller automatically stops charging the electric vehicle upon detecting the leakage of the fluid.

15. The cable assembly of claim 12, further comprising a switch connected to a second node, wherein the second node is in contact with the fluid, and wherein the switch is configurable to simulate the leakage of the fluid.

16. The cable assembly of claim 12, wherein the fluid is electrically conductive. 17 . The cable assembly of claim 12 , wherein the cooling conduit is configured to transport the fluid from the first end to the second end and then from the second end to the first end.

18. The cable assembly of claim 12, wherein the controller further provides at least one of: a visual indication, an audio indication, or a tactile indication upon detecting the leakage of the fluid.

19. The cable assembly of claim 12, wherein the controller detects the leakage of the fluid when a peak-to-peak voltage drop of the output voltage signal exceeds a predetermined threshold voltage drop value.

20. The cable assembly of claim 12, wherein the controller detects the leakage of the fluid when a maximum voltage drop of the output voltage signal exceeds a predetermined threshold maximum voltage value.

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