Low-voltage side zero-sequence voltage protection configuration method of photovoltaic project box transformer substation

Abstract

The invention provides a low-voltage-side zero-sequence voltage protection configuration method for a photovoltaic project box transformer substation, and relates to the technical field of power system relay protection, and the method comprises the steps: additionally arranging a 800V voltage transformer on a low-voltage-side bus of the photovoltaic project box transformer substation, and detecting the zero-sequence voltage of the low-voltage side; a resonance eliminator with impedance greater than 100 megohm is configured at a neutral point of the 800V voltage transformer, so that high-resistance grounding is realized, and single-phase grounding fault current is limited; the zero-sequence voltage is connected to a microcomputer relay protection device, protection of the zero-sequence voltage on the low-voltage side is achieved according to the zero-sequence voltage value, and the protection is divided into two sections, one section is alarming, and the other section is tripping. Based on the scheme provided by the invention, the defect that an existing photovoltaic box transformer substation low-voltage side ungrounded system lacks zero-sequence voltage protection is effectively made up, and the functions of timely detection, alarm and tripping of single-phase grounding faults are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of relay protection for power systems, and in particular to a method for configuring zero-sequence voltage protection on the low-voltage side of a photovoltaic project transformer. Background Art

[0002] With the rapid growth of installed capacity of photovoltaic power stations, the single-unit capacity of inverters has been increased to more than 300kW, and the rated voltage has reached 800V. However, limited by the current level of thyristor technology, the inverter has put forward higher requirements on the system, especially on the low-voltage side of the box-type transformer, which usually needs to operate in an ungrounded state. At the same time, in order to reduce costs, box-type transformer suppliers generally do not configure voltage transformers on the low-voltage side, and the relay protection function is limited to zero-sequence current protection.

[0003] However, since the low-voltage side of the box-type transformer is actually an ungrounded system, the zero-sequence current protection cannot effectively detect single-phase grounding faults, resulting in the low-voltage side of the box-type transformer being in a state without zero-sequence protection during operation. This defect has caused many equipment damage accidents in actual operation, posing a serious threat to the safety and stability of photovoltaic power stations. Therefore, a protection configuration scheme that can make up for this deficiency is urgently needed to improve the operational reliability of the system. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the first objective of the present application is to propose a method for configuring zero-sequence voltage protection on the low-voltage side of a photovoltaic project transformer.

[0006] The second objective of the present application is to provide an electronic device.

[0007] The third object of the present application is to provide a computer-readable storage medium.

[0008] A fourth object of the present application is to provide a computer program product.

[0009] To achieve the above-mentioned purpose, the first embodiment of the present application proposes a method for configuring zero-sequence voltage protection on the low-voltage side of a photovoltaic project box transformer, comprising:

[0010] An 800V voltage transformer is added to the low-voltage busbar of the photovoltaic project box transformer to detect the zero-sequence voltage on the low-voltage side;

[0011] A detuning device with an impedance greater than 100 megohms is configured at the neutral point of the 800V voltage transformer to achieve high-resistance grounding and limit single-phase grounding fault current;

[0012] The zero-sequence voltage is connected to a microcomputer relay protection device, and segmented protection of the zero-sequence voltage on the low-voltage side is achieved according to the zero-sequence voltage value.

[0013] Optionally, the step of implementing segmented protection of the zero-sequence voltage on the low-voltage side according to the zero-sequence voltage value includes:

[0014] When the zero-sequence voltage value exceeds the first stage trip setting value and the delay is greater than 5 seconds, the low-voltage side bus main circuit breaker of the photovoltaic project box transformer is triggered to trip;

[0015] When the zero-sequence voltage value exceeds the second-stage alarm setting value and the delay is greater than 7 seconds, an alarm signal is issued.

[0016] Optionally, the first stage tripping setting value of the tripping protection and the second stage alarm setting value of the alarm protection are both determined in combination with the measured zero-sequence voltage value.

[0017] Optionally, after the low-voltage side bus main circuit breaker of the photovoltaic project box transformer trips, the single-phase grounding fault branch is located by reclosing the low-voltage side molded case circuit breakers one by one, and the fault duration is limited to no more than 3 seconds.

[0018] To achieve the above-mentioned purpose, a second aspect of the present application provides an electronic device, including: a processor, and a memory communicatively connected to the processor;

[0019] The memory stores computer-executable instructions;

[0020] The processor executes the computer-executable instructions stored in the memory to implement the method as described in any one of the first aspects.

[0021] To achieve the above-mentioned purpose, the third aspect embodiment of the present application proposes a computer-readable storage medium, in which computer-readable storage medium is stored computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method as described in any one of the first aspects.

[0022] To achieve the above-mentioned purpose, the fourth aspect of the present application provides a computer program product, which implements any method in the first aspect when executed by a processor.

[0023] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0024] The low-voltage side zero-sequence voltage protection configuration method of the present application effectively compensates for the lack of zero-sequence protection in the existing photovoltaic box transformer system, realizes the timely detection, alarm and tripping functions of single-phase grounding faults, significantly improves the safety, stability and operation efficiency of the system, and reduces the complexity and cost of fault handling.

[0025] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0027] Figure 1 A flowchart of a method for configuring zero-sequence voltage protection on the low-voltage side of a photovoltaic project box transformer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0029] In view of the technical problem that the low-voltage side of the box-type transformer is actually an ungrounded system, the zero-sequence current protection cannot effectively detect the single-phase grounding fault, resulting in the low-voltage side of the box-type transformer being in a state without zero-sequence protection during operation, the embodiment of the present application provides a method for configuring the zero-sequence voltage protection on the low-voltage side of the box-type transformer of a photovoltaic project. Figure 1 The present invention provides a flowchart of a method for configuring a low-voltage side zero-sequence voltage protection for a photovoltaic project transformer box. Figure 1 As shown, the method comprises the following steps:

[0030] Step 101, add an 800V voltage transformer on the low-voltage side busbar of the photovoltaic project box transformer to detect the zero-sequence voltage on the low-voltage side.

[0031] First, an 800V voltage transformer is added to the low-voltage side bus of the photovoltaic project box transformer to detect the zero-sequence voltage on the low-voltage side.

[0032] It should be noted that the voltage transformer can sense the zero-sequence voltage changes of the low-voltage side bus in real time, providing the necessary electrical parameter input for the subsequent protection logic. The zero-sequence voltage is an important parameter for identifying single-phase grounding faults. The addition of voltage transformers makes up for the defect that the ungrounded system cannot monitor the zero-sequence voltage.

[0033] Through this step, the problem of lack of zero-sequence voltage monitoring means on the low-voltage side of the traditional box-type transformer is solved, laying the foundation for the realization of subsequent protection functions.

[0034] Step 102, configuring a detuning device with an impedance greater than 100 megohms at the neutral point of the 800V voltage transformer to achieve high-resistance grounding and limit the single-phase grounding fault current.

[0035] In the embodiment of the present application, a detuning device with an impedance greater than 100 megohms is configured at the neutral point of the 800V voltage transformer to achieve high-resistance grounding and limit the single-phase grounding fault current.

[0036] It should be noted that configuring a harmonic elimination device with an impedance greater than 100 megohms can effectively limit the single-phase grounding fault current through high-resistance grounding, avoiding equipment damage caused by the flow of large current. In addition, the high-resistance grounding method reduces the shunt effect of the grounding fault current, making the zero-sequence voltage signal more obvious, and enhancing the relay protection device's detection capability for single-phase grounding faults.

[0037] It can be understood that limiting the single-phase grounding fault current not only prevents the equipment from being damaged due to overcurrent, but also reduces the impact of the fault on other equipment in the system and extends the service life of the equipment.

[0038] Through this step, a stable high-resistance grounding system is established, which provides a good basic guarantee for the accurate acquisition of zero-sequence voltage signals and the implementation of subsequent protection logic.

[0039] Step 103, connecting the zero-sequence voltage to the microcomputer relay protection device, and implementing segmented protection of the zero-sequence voltage on the low-voltage side according to the zero-sequence voltage value.

[0040] In an embodiment of the present application, after completing the low-voltage side zero-sequence voltage protection configuration of the photovoltaic project box transformer according to the steps shown in step 101 and step 102, the zero-sequence voltage signal detected by the 800V voltage transformer is transmitted to the microcomputer relay protection device, and is set in combination with the measured zero-sequence voltage value. This can ensure that the action values ​​of the tripping protection and the alarm protection meet the on-site operating conditions, thereby avoiding false operation or refusal of protection due to setting value deviation.

[0041] Specifically, the zero-sequence voltage protection action on the low-voltage side is set in two stages, including:

[0042] (1) First stage tripping protection: When the zero-sequence voltage value exceeds the first stage tripping setting value and the delay of the microcomputer relay protection device is greater than 5 seconds, the main circuit breaker on the low-voltage side of the box-type transformer will be triggered to trip, quickly isolate the fault and protect the safety of the equipment.

[0043] (2) Second stage alarm function: When the zero-sequence voltage exceeds the second stage alarm setting value, the microcomputer relay protection device delays for more than 7 seconds and sends an alarm signal to the operation monitoring system. At the same time, the fault information is displayed locally on the protection device to remind the operating personnel to promptly check the fault.

[0044] It is understandable that the segmented protection design ensures the safety of the equipment while minimizing the impact on the system. For example, the alarm function can alert the operation and maintenance personnel at the early stage of the fault, while the tripping function can quickly isolate the fault branch when necessary to ensure system stability.

[0045] In addition, the first stage trip setting value of the trip protection and the second stage alarm setting value of the alarm protection are determined in combination with the measured zero-sequence voltage value. Since the zero-sequence voltage characteristics of each photovoltaic power station may vary due to different equipment and system configurations, by adjusting the setting value based on the measured data in this application, it can adapt to a variety of application scenarios and enhance the versatility of the protection scheme.

[0046] In addition, the low-voltage side zero-sequence voltage protection configuration method of the photovoltaic project box transformer proposed in the embodiment of the present application is applicable to the ungrounded or high-resistance grounded system on the low-voltage side of the box transformer, and can continue to operate for no more than 2 hours after a single-phase grounding fault occurs, meeting the requirements of industry operating regulations.

[0047] In addition, in order to handle faults accurately and quickly, after the busbar main circuit breaker on the low-voltage side of the photovoltaic project box transformer trips, the embodiment of the present application manually disconnects all branch circuit breakers on the low-voltage side of the box transformer to ensure that all branch circuit breakers are in the open state, and then manually recloses the low-voltage side branch circuit breakers one by one, and checks the faulty branch through the "fault reappearance" method. Once the faulty branch is found, the branch circuit breaker is immediately disconnected to ensure that the fault reappearance time does not exceed 3 seconds. Finally, after the investigation is completed, the normal operation of the non-faulty branch is restored. Through this method, the branch that tripped by mistake is prevented from being in a state of suspension for a long time, reducing the loss of power outage.

[0048] In order to implement the above embodiments, the present application also proposes an electronic device, comprising: a processor, and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the method provided by the above embodiments.

[0049] In order to implement the above embodiments, the present application also proposes a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the methods provided by the above embodiments.

[0050] In order to implement the above embodiments, the present application also proposes a computer program product, including a computer program, which implements the methods provided by the above embodiments when executed by a processor.

[0051] The collection, storage, use, processing, transmission, provision and disclosure of user personal information involved in this application are in compliance with relevant laws and regulations and do not violate public order and good morals.

[0052] It should be noted that personal information from users should be collected for legitimate and reasonable purposes and should not be shared or sold outside of these legitimate uses. In addition, such collection / sharing should be carried out after receiving the user's informed consent, including but not limited to notifying the user to read the user agreement / user notice and sign the agreement / authorization including authorization of relevant user information before the user uses the function. In addition, any necessary steps should be taken to protect and safeguard access to such personal information data and ensure that others who have access to personal information data comply with its privacy policy and procedures.

[0053] The present application is expected to provide an implementation scheme for users to selectively block the use or access of personal information data. That is, the present disclosure is expected to provide hardware and / or software to prevent or block access to such personal information data. Once the personal information data is no longer needed, the risk can be minimized by limiting data collection and deleting the data. In addition, when applicable, such personal information is de-identified to protect the privacy of the user.

[0054] In the description of the aforementioned embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0055] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0056] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0057] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute the instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0058] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0059] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0060] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0061] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

[0062] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution of this application can be achieved, and this document is not limited here.

[0063] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for configuring zero-sequence voltage protection on the low-voltage side of a photovoltaic project box transformer, characterized in that: The following steps are involved: An 800V voltage transformer is added to the low-voltage busbar of the photovoltaic project box transformer to detect the zero-sequence voltage on the low-voltage side; A detuning device with an impedance greater than 100 megohms is configured at the neutral point of the 800V voltage transformer to achieve high-resistance grounding and limit single-phase grounding fault current; The zero-sequence voltage is connected to a microcomputer relay protection device, and segmented protection of the zero-sequence voltage on the low-voltage side is achieved according to the zero-sequence voltage value.

2. The method according to claim 1, characterized in that The step of realizing the segmented protection of the zero-sequence voltage on the low-voltage side according to the zero-sequence voltage value includes: When the zero-sequence voltage value exceeds the first stage trip setting value and the delay is greater than 5 seconds, the low-voltage side bus main circuit breaker of the photovoltaic project box transformer is triggered to trip; When the zero-sequence voltage value exceeds the second-stage alarm setting value and the delay is greater than 7 seconds, an alarm signal is issued.

3. The method for configuring low-voltage side zero-sequence voltage protection of a photovoltaic project box transformer according to claim 2 is characterized in that: The first stage tripping setting value of the tripping protection and the second stage alarm setting value of the alarm protection are determined in combination with the measured zero-sequence voltage value.

4. The method for configuring low-voltage side zero-sequence voltage protection of a photovoltaic project box transformer according to claim 2 is characterized in that: After the low-voltage side busbar main circuit breaker of the photovoltaic project box transformer trips, the single-phase grounding fault branch is located by reclosing the low-voltage side molded case circuit breakers one by one, and the fault duration is limited to no more than 3 seconds.

5. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 4.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 4 when executed by a processor.

7. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 4 when being executed by a processor.

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