Overload protection method and device for energy storage system

Abstract

The present disclosure provides an overload protection method and device of an energy storage system, and relates to the technical field of energy storage, which comprises the following steps: monitoring the current value of an energy storage device; obtaining the first integral of the square of the current value with respect to time corresponding to any time period and the second integral of the first parameter value with respect to time corresponding to the any time period; determining that the any time period is an overload protection time in response to determining that the difference between the first integral and the second integral corresponding to the any time period meets a preset threshold value; and starting overload protection at the end moment corresponding to the overload protection time. Thus, the moment requiring overload protection can be accurately found through the integral of the current with respect to time and the preset threshold value, the overload condition of the inverter can be represented in real time and continuously, and thus the energy storage device can timely send an overload protection action when the user load exceeds the load capacity of the energy storage device in the off-grid load condition.

Description

Technical Field

[0001] This disclosure relates to the field of energy storage technology, and in particular to an overload protection method and device for an energy storage system. Background Technology

[0002] In recent years, energy storage devices have been widely used in energy storage-related industries. When the user load exceeds the load capacity of the energy storage device while it is off-grid and under load, the energy storage system needs to issue an overload protection action.

[0003] Typical energy storage device overload protection logic often involves setting several overload levels, such as: protection after 150 seconds at 120% load; protection after 20 seconds at 150% to 200% load; and protection after 350 milliseconds at 200% load. This is a discrete overload protection measure. Such a protection measure means that, for example, at a 199% overload rate, the protection time will still be 20 seconds. Because it is highly discrete, it is difficult to characterize the inverter's overload condition. Summary of the Invention

[0004] This disclosure aims to at least partially address one of the technical problems in the related art.

[0005] The first aspect of this disclosure provides an overload protection method for an energy storage system, comprising:

[0006] Monitor the current value of the energy storage device; Obtain the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to the any time period with respect to time; In response to determining that the difference between the first integral and the second integral corresponding to any time period meets a preset threshold, the any time period is determined to be an overload protection time. Overload protection is activated at the end of the overload protection period.

[0007] A second aspect of this disclosure provides an overload protection device for an energy storage system, comprising: The monitoring module is used to monitor the current value of the energy storage device; The acquisition module is used to acquire the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to the any time period with respect to time. The first determining module is configured to determine that any time period is an overload protection time period in response to determining that the difference between the first integral and the second integral corresponding to any time period satisfies a preset threshold. The startup module is used to activate the overload protection at the end time corresponding to the overload protection time.

[0008] A third aspect of this disclosure provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements an overload protection method for an energy storage system as proposed in a first aspect of this disclosure.

[0009] The fourth aspect of this disclosure provides a non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements an overload protection method for an energy storage system as proposed in the first aspect of this disclosure.

[0010] The overload protection method and device for the energy storage system disclosed herein have the following beneficial effects: In this embodiment, the current value of the energy storage device is first monitored. Then, the first integral of the square of the current value over time corresponding to any given time period, and the second integral of the first parameter value over time corresponding to that time period, are obtained. Subsequently, in response to determining that the difference between the first and second integrals for any given time period satisfies a preset threshold, the given time period is determined to be an overload protection time. Then, overload protection is initiated at the end of the overload protection time. Therefore, by using the integral of current over time and the preset threshold, the moment requiring overload protection can be accurately identified. This allows for real-time and continuous characterization of the inverter's overload status, enabling the energy storage device to promptly issue overload protection when the user load exceeds the energy storage device's load capacity under off-grid load conditions.

[0011] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0012] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, in which: Figure 1 A schematic flowchart illustrating an overload protection method for an energy storage system provided in an embodiment of this disclosure; Figure 2 A schematic flowchart illustrating an overload protection method for an energy storage system provided in an embodiment of this disclosure; Figure 3 A structural block diagram of an overload protection device for an energy storage system provided in an embodiment of this disclosure; Figure 4 A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. Detailed Implementation

[0013] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0014] The following description, with reference to the accompanying drawings, outlines an overload protection method, apparatus, computer device, and storage medium for an energy storage system according to embodiments of the present disclosure.

[0015] It should be noted that the execution subject of the overload protection method for the energy storage system in this embodiment is the overload protection device of the energy storage system. This device can be implemented by software and / or hardware. The overload protection method for the energy storage system proposed in this embodiment will be described below with the "overload protection device of the energy storage system" as the execution subject, and no limitation is made here.

[0016] Figure 1 This is a flowchart illustrating the overload protection method for an energy storage system provided in an embodiment of this disclosure.

[0017] like Figure 1 As shown, the overload protection method for this energy storage system may include the following steps: Step 101: Monitor the current value of the energy storage device.

[0018] Energy storage devices are the core component of an energy storage system. Their function is to convert energy, such as fuel, wind power, and solar energy, into a form that can be stored to meet the needs of the power system and alleviate sudden supply and demand disruptions. Common energy storage devices include batteries, hydrogen fuel cells, and hybrid hydrogen systems.

[0019] When the energy storage device is off-grid and under load, it supplies part of the electricity to the load and uses the rest to charge the battery. The current value can be the current value of the energy storage inverter to which the energy storage device is connected.

[0020] Optionally, the current overload rate of the energy storage device can be determined based on the ratio between the current current value and the rated current in the energy storage device, and then an alarm message can be issued when the current overload rate of the energy storage device reaches a first threshold.

[0021] For example, if the ratio of the current current to the rated current is 1.4, then 140% can be taken as the current overload rate of the energy storage device.

[0022] The first threshold can be 95%, so an alarm message can be issued directly when the current overload rate of the energy storage device reaches 95%, without blocking the detection. In other words, the energy storage device continues to work normally at this time, but an alarm is issued.

[0023] Alternatively, if the current overload rate of the energy storage device reaches the second threshold, the energy storage device can be controlled to stop output and perform fault protection. The second threshold is greater than the first threshold.

[0024] The second threshold can be 230%. That is, when the overload rate reaches the second threshold, for example, when it reaches 230%, the fault protection will detect it directly and the equipment will stop outputting.

[0025] Step 102: Obtain the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to any time period with respect to time.

[0026] It should be noted that the current value of the energy storage device can be continuously monitored, and the first integral of the square of the current value with respect to time can be obtained.

[0027] The first parameter value can be the overload rate corresponding to the long-term operating point under stable hardware temperature rise.

[0028] In this embodiment of the disclosure, the first parameter value can be 1.05, or 105%.

[0029] Step 103: In response to determining that the difference between the first integral and the second integral corresponding to any time period meets a preset threshold, determine any time period as the overload protection time.

[0030] Optionally, the difference Q between the first and second integrals for any given time period can be calculated using the following formula: Q= )dt Where x is the current value at any moment within any time period, and 1.05 is the first parameter value (as an example).

[0031] In this embodiment of the disclosure, the preset threshold can be 40.5, that is, if the difference Q between the first integral and the second integral corresponding to any time period is 40.5, then any time period can be determined as the overload protection time.

[0032] The preset threshold is 40.5, which is determined by actual temperature rise testing to be the maximum allowable energy of the inverter under a specific environment.

[0033] Step 104: At the end of the overload protection time, activate the overload protection.

[0034] It is understandable that if the difference between the first and second integrals for any given time period satisfies the maximum allowable energy, then overload protection needs to be triggered. Therefore, this given time period can be used as the overload protection time, and overload protection can be initiated at the end of the corresponding overload protection time.

[0035] In this embodiment, the current value of the energy storage device is first monitored. Then, the first integral of the square of the current value over time corresponding to any given time period, and the second integral of the first parameter value over time corresponding to that time period, are obtained. Subsequently, in response to determining that the difference between the first and second integrals for any given time period satisfies a preset threshold, the given time period is determined to be an overload protection time. Then, overload protection is initiated at the end of the overload protection time. Therefore, by using the integral of current over time and the preset threshold, the moment requiring overload protection can be accurately identified. This allows for real-time and continuous characterization of the inverter's overload status, enabling the energy storage device to promptly issue overload protection when the user load exceeds the energy storage device's load capacity under off-grid load conditions.

[0036] Figure 2 This is a flowchart illustrating the overload protection method for an energy storage system provided in an embodiment of this disclosure.

[0037] like Figure 2 As shown, the overload protection method for this energy storage system may include the following steps: Step 201: Monitor the current value of the energy storage device.

[0038] Step 202: Determine the current overload rate of the energy storage device based on the ratio between the current current value and the rated current in the energy storage device.

[0039] It should be noted that the specific implementation methods of steps 201 and 202 can refer to the above embodiments, and will not be repeated here.

[0040] Step 203: Based on a preset mathematical model, obtain the target mapping relationship curve between the overload rate of the energy storage device and the overload protection time.

[0041] The pre-defined mathematical model can be: t= / ( ) Where Q is the maximum allowable energy of the inverter under a specific environment, determined through actual temperature rise testing, which is 40.5; x is the overload rate; and t is the overload protection time.

[0042] The target mapping curve can be a mapping curve corresponding to the target overload rate range, that is, the overload rate in the target mapping curve is the overload rate between the first threshold and the second threshold, such as (95%, 230%). The overload protection time is the overload protection time corresponding to each overload rate in this range.

[0043] Step 204: Based on the target mapping curve, determine the overload protection time corresponding to each overload rate.

[0044] It should be noted that the target mapping curve contains the mapping relationship between each overload rate and the overload protection time. Therefore, the overload protection time corresponding to each overload rate can be determined based on the target mapping curve.

[0045] Step 205: In response to determining that the current value of the energy storage device remains unchanged during the overload protection time corresponding to any overload rate, overload protection is activated at the end of the overload protection time.

[0046] Understandably, if the current overload rate is 160%, and the corresponding overload protection time is 27.787s, then the overload protection can be activated after 27.787s.

[0047] In this embodiment, the current value of the energy storage device is first monitored. Based on the ratio between the current current value and the rated current of the energy storage device, the current overload rate of the energy storage device is determined. Then, based on a preset mathematical model, a target mapping relationship curve between the overload rate of the energy storage device and the overload protection time is obtained. Next, based on the target mapping relationship curve, the overload protection time corresponding to each overload rate is determined. Finally, in response to the determination that the current value of the energy storage device remains unchanged within the overload protection time corresponding to any overload rate, overload protection is initiated at the end of the overload protection time. Therefore, based on the target mapping relationship curve between the overload rate of the energy storage device and the overload protection time, the overload protection time corresponding to each overload rate can be accurately found, allowing for real-time and continuous characterization of the inverter's overload status.

[0048] To achieve the above embodiments, this disclosure also proposes an overload protection device for an energy storage system.

[0049] Figure 3 A structural block diagram of an overload protection device for an energy storage system provided in the third embodiment of this disclosure.

[0050] like Figure 3 As shown, the overload protection device 400 of the energy storage system may include: Monitoring module 310 is used to monitor the current value of the energy storage device; The acquisition module 320 is used to acquire the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to the any time period with respect to time. The first determining module 330 is configured to determine the any time period as an overload protection time in response to determining that the difference between the first integral and the second integral corresponding to any time period meets a preset threshold. The startup module 340 is used to start the overload protection at the end time corresponding to the overload protection time.

[0051] Optionally, the monitoring module further includes: The first determining unit is used to determine the current overload rate of the energy storage device based on the ratio between the current current value and the rated current in the energy storage device. The warning unit is used to issue an alarm message when the current overload rate of the energy storage device reaches a first threshold.

[0052] Optionally, the first determining unit is further configured to: If the current overload rate of the energy storage device reaches a second threshold, the energy storage device is controlled to stop output and fault protection is performed, wherein the second threshold is greater than the first threshold.

[0053] Optionally, the device may also include: The second acquisition module is used to acquire the target mapping relationship curve between the overload rate of the energy storage device and the overload protection time based on a preset mathematical model. The second determining module is used to determine the overload protection time corresponding to each overload rate based on the target mapping relationship curve.

[0054] Optionally, the second determining module is further configured to: In response to determining that the current value of the energy storage device remains unchanged during the overload protection time corresponding to any overload rate, overload protection is activated at the end of the overload protection time.

[0055] In this embodiment, the current value of the energy storage device is first monitored. Then, the first integral of the square of the current value over time corresponding to any given time period, and the second integral of the first parameter value over time corresponding to that time period, are obtained. Subsequently, in response to determining that the difference between the first and second integrals for any given time period satisfies a preset threshold, the given time period is determined to be an overload protection time. Then, overload protection is initiated at the end of the overload protection time. Therefore, by using the integral of current over time and the preset threshold, the moment requiring overload protection can be accurately identified. This allows for real-time and continuous characterization of the inverter's overload status, enabling the energy storage device to promptly issue overload protection when the user load exceeds the energy storage device's load capacity under off-grid load conditions.

[0056] To implement the above embodiments, this disclosure also proposes a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the overload protection method for the energy storage system proposed in the foregoing embodiments of this disclosure.

[0057] To implement the above embodiments, this disclosure also proposes a non-transitory computer-readable storage medium storing a computer program, which, when executed by a processor, implements the overload protection method for the energy storage system as proposed in the foregoing embodiments of this disclosure.

[0058] Figure 4 A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. Figure 4 The computer device 12 shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments disclosed herein.

[0059] like Figure 4 As shown, the computer device 12 is represented in the form of a general-purpose computing device. The components of the computer device 12 may include, but are not limited to: one or more processors or processing units 16, system memory 28, and bus 18 connecting different system components (including system memory 28 and processing unit 16).

[0060] Bus 18 represents one or more of several bus architectures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus using any of the various bus architectures. Examples of these architectures include, but are not limited to, the Industry Standard Architecture (ISA) bus, the Micro Channel Architecture (MAC) bus, the Enhanced ISA bus, the Video Electronics Standards Association (VESA) local bus, and the Peripheral Component Interconnect (PCI) bus.

[0061] Computer device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by computer device 12, including volatile and non-volatile media, removable and non-removable media.

[0062] Memory 28 may include computer system readable media in the form of volatile memory, such as Random Access Memory (RAM) 30 and / or cache memory 32. Computer device 12 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, storage system 34 may be used to read and write non-removable, non-volatile magnetic media (…). Figure 4Not shown; usually referred to as a "hard drive"). Although Figure 4 As not shown, a disk drive for reading and writing to a removable non-volatile disk (e.g., a "floppy disk") and an optical disc drive for reading and writing to a removable non-volatile optical disc (e.g., a compact disc read-only memory (CD-ROM), a digital video disc read-only memory (DVD-ROM), or other optical media) may be provided. In these cases, each drive may be connected to bus 18 via one or more data media interfaces. Memory 28 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of this disclosure.

[0063] A program / utility 40 having a set (at least one) of program modules 42 may be stored, for example, in memory 28. Such program modules 42 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data. Each or some combination of these examples may include an implementation of a network environment. Program modules 42 typically perform the functions and / or methods described in the embodiments of this disclosure.

[0064] Computer device 12 can also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), and with one or more devices that enable a user to interact with the computer device 12, and / or with any device that enables the computer device 12 to communicate with one or more other computing devices (e.g., network card, modem, etc.). This communication can be performed via input / output (I / O) interface 22. Furthermore, computer device 12 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public networks, such as the Internet) via network adapter 20. As shown, network adapter 20 communicates with other modules of computer device 12 via bus 18. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with computer device 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0065] The processing unit 16 executes various functional applications and data processing by running programs stored in the system memory 28, such as implementing the methods mentioned in the foregoing embodiments.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of this disclosure includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of this disclosure pertain.

[0069] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0070] It should be understood that various parts of this disclosure can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0071] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0072] Furthermore, the functional units in the various embodiments of this disclosure can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0073] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present disclosure.

Claims

1. An overload protection method for an energy storage system, characterized in that, include: Monitor the current value of the energy storage device; Obtain the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to the any time period with respect to time, wherein the first parameter value is the overload rate corresponding to the long-term operating point under stable hardware temperature rise. In response to determining that the difference between the first integral and the second integral corresponding to any time period meets a preset threshold, the any time period is determined to be an overload protection time. Overload protection is activated at the end of the overload protection period.

2. The method according to claim 1, characterized in that, After monitoring the current value of the energy storage device, the method further includes: The current overload rate of the energy storage device is determined based on the ratio between the current value and the rated current in the energy storage device. An alarm message will be issued if the current overload rate of the energy storage device reaches a first threshold.

3. The method according to claim 2, characterized in that, After determining the current overload rate of the energy storage device, the method further includes: If the current overload rate of the energy storage device reaches a second threshold, the energy storage device is controlled to stop output and fault protection is performed, wherein the second threshold is greater than the first threshold.

4. The method according to claim 2, characterized in that, Also includes: Based on a preset mathematical model, a target mapping relationship curve between the overload rate of the energy storage device and the overload protection time is obtained. The preset mathematical model is as follows: t= / ( ) Where Q is the maximum allowable energy of the inverter under a specific environment, determined through actual temperature rise testing, x is the overload rate, and t is the overload protection time; Based on the target mapping curve, the overload protection time corresponding to each overload rate is determined.

5. The method according to claim 4, characterized in that, After determining the overload protection time corresponding to each overload rate, the method further includes: In response to determining that the current value of the energy storage device remains unchanged during the overload protection time corresponding to any overload rate, overload protection is activated at the end of the overload protection time.

6. An overload protection device for an energy storage system, characterized in that, include: The monitoring module is used to monitor the current value of the energy storage device; The acquisition module is used to acquire the first integral of the square of the current value corresponding to any time period with respect to time, and the second integral of the first parameter value corresponding to the any time period with respect to time, wherein the first parameter value is the overload rate corresponding to the long-term operating point under stable hardware temperature rise. The first determining module is configured to determine that any time period is an overload protection time period in response to determining that the difference between the first integral and the second integral corresponding to any time period satisfies a preset threshold. The startup module is used to activate the overload protection at the end time corresponding to the overload protection time.

7. The apparatus according to claim 6, characterized in that, The monitoring module also includes: The first determining unit is used to determine the current overload rate of the energy storage device based on the ratio between the current current value and the rated current in the energy storage device. The warning unit is used to issue an alarm message when the current overload rate of the energy storage device reaches a first threshold.

8. The apparatus according to claim 7, characterized in that, The first determining unit is further configured to: If the current overload rate of the energy storage device reaches a second threshold, the energy storage device is controlled to stop output and fault protection is performed, wherein the second threshold is greater than the first threshold.

9. The apparatus according to claim 7, characterized in that, Also includes: The second acquisition module is used to acquire, based on a preset mathematical model, a target mapping relationship curve between the overload rate of the energy storage device and the overload protection time. The preset mathematical model is as follows: t= / ( ) Where Q is the maximum allowable energy of the inverter under a specific environment, determined through actual temperature rise testing, x is the overload rate, and t is the overload protection time; The second determining module is used to determine the overload protection time corresponding to each overload rate based on the target mapping relationship curve.

10. The apparatus according to claim 9, characterized in that, The second determining module is further configured to: In response to determining that the current value of the energy storage device remains unchanged during the overload protection time corresponding to any overload rate, overload protection is activated at the end of the overload protection time.

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