Transformer protection method and device based on zero sequence compensation, electronic equipment and storage medium

Abstract

The embodiment of the invention discloses a transformer protection method and device based on zero sequence compensation, electronic equipment and a computer readable storage medium, and relates to the technical field of transformer protection, and the method comprises the steps: collecting the three-phase current of a high-voltage side switch, the three-phase current of a medium-voltage side switch, the three-phase current of a low-voltage side switch and the three-phase current of a low-voltage side sleeve of a transformer; calculating the zero-sequence current of the low-voltage side bushing according to the three-phase current of the low-voltage side bushing; compensating the three-phase current of the low-voltage side switch and calculating the compensated three-phase current of the low-voltage side switch; differential current is calculated based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch and the compensated three-phase current of the low-voltage side switch; and judging whether the transformer fails or not according to the calculated differential current. The problems that differential current inrush current distortion and protection action sensitivity reduction are caused by the fact that current longitudinal differential protection is used for guaranteeing differential current balance of the star-delta side and zero filtering processing is carried out on the star-delta side are solved.

Description

Technical Field

[0001] This disclosure relates to the field of transformer protection technology, specifically to a transformer protection method, apparatus, electronic device, and computer-readable storage medium based on zero-sequence compensation. Background Technology

[0002] Transformers are one of the core pieces of equipment in a power system, and their safe and stable operation directly affects the reliability of the power grid. Traditional transformer differential protection is usually based on differential calculations of the current on each side. However, when the high-voltage side of the transformer uses a star connection and the low-voltage side uses a delta connection, zero filtering on the high-voltage side can lead to increased errors in the differential current calculation, which in turn can cause the protection to malfunction or fail to operate.

[0003] 500kV transformers are typically equipped with longitudinal differential protection, phase-specific differential protection, and low-voltage side differential protection as main protection. The longitudinal differential protection is composed of the differential currents from the high-voltage, medium-voltage, and low-voltage sides of the transformer. For transformers with star connections on the high and medium voltage sides and delta connections on the low-voltage side, zero-sequence current will appear on the star side during a ground fault, while the zero-sequence current in the delta-connected windings only flows internally as a circulating current, and the zero-sequence current on the switch side is zero. To prevent the longitudinal differential protection from operating due to an imbalance of zero-sequence current on the star and delta sides during external ground faults, existing protection schemes all perform zero-sequence filtering on the star side during differential current calculations. One zero-sequence filtering method is to filter the zero-sequence current during the phase transition calculation from star to delta, and another method is to subtract the zero-sequence current separately from the star side during the phase transition from delta to star. Regardless of the zero-sequence filtering method, the inrush current characteristics of the differential current will be distorted due to zero-sequence filtering, and zero-sequence filtering will also reduce the sensitivity to high-resistance ground faults, affecting its operating behavior. Summary of the Invention

[0004] This disclosure provides a transformer protection method, device, electronic device, and computer-readable storage medium based on zero-sequence compensation, which solves the problem that current longitudinal differential protection performs zero-filtering to ensure the balance of differential current on the star-delta side, resulting in differential current inrush distortion and reduced protection action sensitivity.

[0005] In a first aspect, embodiments of this disclosure provide a transformer protection method based on zero-sequence compensation, including: Collect the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, the three-phase current of the low-voltage side switch, and the three-phase current of the low-voltage side bushing of the transformer; Calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing: Based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing, calculate the compensated three-phase current of the low-voltage side switch. The differential current is calculated based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch. The transformer is determined to be faulty based on the calculated differential current.

[0006] Secondly, embodiments of this disclosure also provide a transformer protection device based on zero-sequence compensation, comprising: The data acquisition module is used to acquire the three-phase current of the high-voltage side switch, the medium-voltage side switch, the low-voltage side switch, and the low-voltage side bushing. The first calculation module is used to calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing. The second calculation module is used to calculate the compensated three-phase current of the low-voltage side switch based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing. The third calculation module is used to calculate the differential current based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch. The transformer is determined to be faulty based on the calculated differential current.

[0007] Thirdly, this disclosure also provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps in the above-described transformer protection method based on zero-sequence compensation.

[0008] Fourthly, embodiments of this disclosure also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps in the above-described transformer protection method based on zero-sequence compensation.

[0009] Fifthly, embodiments of this disclosure also provide a computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the methods provided in various optional implementations of embodiments of this disclosure.

[0010] In this embodiment, the three-phase currents of the high-voltage side switch, medium-voltage side switch, low-voltage side switch, and low-voltage side bushing are first collected. Then, based on the low-voltage side bushing three-phase current, the zero-sequence current of the low-voltage side bushing is calculated. Next, based on the low-voltage side switch three-phase current and the low-voltage side bushing zero-sequence current, the low-voltage side switch three-phase current is compensated, and the compensated low-voltage side switch three-phase current is calculated. Then, based on the high-voltage side switch three-phase current, medium-voltage side switch three-phase current, and the compensated low-voltage side switch three-phase current, the differential current is calculated. Finally, the transformer fault is determined based on the calculated differential current. This allows for reliable identification of various types of transformer faults, solving the problems of differential distortion caused by zero-filtering in conventional differential protection and insufficient sensitivity to high-resistance grounding faults on the star side, greatly improving the safety and stability of transformer operation.

[0011] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic flowchart of a transformer protection method based on zero-sequence compensation provided in an embodiment of this disclosure; Figure 2 The overall architecture diagram of the transformer protection method based on zero-sequence compensation is shown; Figure 3 This is a schematic diagram of the structure of a transformer protection device based on zero-sequence compensation provided in an embodiment of this disclosure; Figure 4 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this disclosure. Detailed Implementation

[0014] Some embodiments of this disclosure will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. Various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but can be changed as will become apparent upon understanding this disclosure, except for operations that must be performed in a particular order. Furthermore, for clarity and brevity, descriptions of features known in the art may be omitted.

[0015] The embodiments described in the following examples of this disclosure are not representative of all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0016] It should be noted that the order of description of the following embodiments is not intended to limit the priority of the embodiments.

[0017] Figure 1 This is a flowchart illustrating a transformer protection method based on zero-sequence compensation provided according to an embodiment of this disclosure.

[0018] It should be noted that the implementing entity of the transformer protection method based on zero-sequence compensation in this embodiment can be a transformer protection device based on zero-sequence compensation, hereinafter referred to as "device". This device can be configured in any type of electronic device, and this application embodiment does not limit it.

[0019] See Figure 1 This is a flowchart illustrating the transformer protection method based on zero-sequence compensation provided in an embodiment of this application. Figure 1 As shown, the method includes: Step 101: Collect the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, the three-phase current of the low-voltage side switch, and the three-phase current of the low-voltage side bushing.

[0020] Zero-sequence compensation refers to the correction of relevant currents in power system protection using specific calculation methods to address the impact of zero-sequence current on protection operation characteristics, thereby eliminating or reducing the adverse effects of zero-sequence current and improving the accuracy and reliability of protection device operation.

[0021] Transformer protection methods refer to methods that, in order to ensure the safe operation of transformers, can quickly and accurately detect and isolate faults when transformers malfunction or experience abnormal operating conditions, thereby preventing the faults from escalating and reducing equipment damage and the scope of power outages.

[0022] Among them, the three-phase currents of the high-voltage side switch, the medium-voltage side switch, and the low-voltage side switch refer to the three-phase (A, B, and C phases) currents flowing through the switches on the high-voltage side, medium-voltage side, and low-voltage side of the transformer, respectively. These currents reflect the load conditions and operating status of each side of the transformer and are important raw data in transformer protection calculations.

[0023] The three-phase current of the low-voltage side bushing refers to the three-phase current flowing through the low-voltage side bushing of the transformer. The bushing is an insulating device between the transformer leads and the tank, and its current status reflects the operating condition of the low-voltage side leads and related equipment.

[0024] Specifically, current transformers (CTs) need to be installed on the high-voltage side, medium-voltage side, low-voltage side switches, and low-voltage side bushings of the transformer. The current transformers proportionally transform the large primary current into a smaller secondary current, facilitating measurement and data acquisition by the protection device. Optionally, AC sampling technology can be used, converting the analog current signal output from the secondary side of the current transformer into a digital signal via an analog-to-digital converter (ADC). The sampling frequency needs to meet the requirements of the protection algorithm and is generally high to ensure that the acquired current waveform accurately reflects the actual current changes. The acquired digital current signal is transmitted to the microprocessor of the protection device for processing via a communication interface.

[0025] Step 102: Calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing.

[0026] Specifically, after collecting the three-phase current of the low-voltage side bushing, the zero-sequence current of the low-voltage side bushing can be calculated using the following formula:

[0027] in, The zero-sequence current is three times that of the low-voltage side bushing. , , These are the three-phase currents of the low-voltage side bushing. It is the single zero-sequence current of the low-voltage side bushing.

[0028] The zero-sequence current of the low-voltage side bushing refers to the zero-sequence component current that appears in a three-phase system when the three-phase currents are unbalanced. The magnitude and phase of the zero-sequence current are related to the degree of imbalance of the three-phase currents. In this method, the zero-sequence current of the low-voltage side bushing is calculated based on the three-phase current of the low-voltage side bushing and used for subsequent zero-sequence compensation calculations.

[0029] Step 103: Based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing, compensate the three-phase current of the low-voltage side switch and calculate the compensated three-phase current of the low-voltage side switch.

[0030] The compensated three-phase current of the low-voltage side switch refers to the three-phase current of the low-voltage side switch obtained after zero-sequence compensation calculation. After zero-sequence compensation, this current can more accurately reflect the actual current situation of the transformer's low-voltage side switch after considering the influence of zero-sequence current, providing more accurate data for subsequent differential current calculation and improving the accuracy of fault diagnosis.

[0031] Optionally, a zero-sequence compensation formula can be derived based on the phase relationship between the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing. Based on this formula, zero-sequence compensation can be performed on the three-phase current of the low-voltage side switch, and the compensated three-phase current of the low-voltage side switch can be calculated. The zero-sequence compensation formula is as follows:

[0032]

[0033]

[0034] in, , , For the three-phase current of the low-voltage side switch, This refers to the zero-sequence current of the low-voltage side bushing. , , The three-phase current of the low-voltage side switch after compensation.

[0035] Specifically, after collecting the three-phase current of the low-voltage side switch, when the transformer is operating normally, the three-phase current of the low-voltage side switch and the three-phase current of the low-voltage side bushing have the following current relationship:

[0036]

[0037]

[0038] in, , , These are the three-phase currents of the low-voltage side switch. , , These are the three-phase currents of the low-voltage side bushing.

[0039] Furthermore, the following formula can be derived:

[0040]

[0041]

[0042] in, , , These are the three-phase currents of the low-voltage side switch. , , These are the three-phase currents of the low-voltage side bushing. The zero-sequence current is three times that of the low-voltage side bushing.

[0043] Furthermore, the zero-sequence compensation formula for the low-pressure side is derived as follows:

[0044]

[0045]

[0046] It should be noted that for transformers with low-voltage side delta connection, the low-voltage side switch cannot collect zero-sequence current. However, since the low-voltage side bushing collects the current before the delta connection, which includes a zero-sequence current component, the zero-sequence current characteristics of the low-voltage side bushing can be used, combined with the relationship between the current of the low-voltage side bushing and the low-voltage side switch, to achieve compensation for the low-voltage side zero-sequence current.

[0047] The novel transformer protection method based on zero-sequence compensation of the present invention allows the low-voltage side switching current to reflect the zero-sequence component through the low-voltage side bushing zero-sequence current after zero-sequence compensation. This not only balances the zero-sequence current of the high-voltage side star connection, but also effectively avoids the distortion of differential current calculation caused by high-voltage side zero filtering.

[0048] Step 104: Calculate the differential current based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch.

[0049] Optionally, the differential current is calculated using a preset differential current calculation formula, the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, the compensated three-phase current of the low-voltage side switch, the medium-voltage side current conversion factor, and the low-voltage side current conversion factor. The preset differential current calculation formula is as follows:

[0050]

[0051]

[0052] Among them, K M and K L These are the current reduction factors for the medium-voltage side and the low-voltage side, respectively. , , For the three-phase current of the high-voltage side switch, , , For the three-phase current of the medium-voltage side switch, , , This is the differential current.

[0053] It should be noted that the current on the medium-voltage side and low-voltage side is converted to the high-voltage side using a current conversion factor, eliminating the current amplitude mismatch problem caused by voltage level differences. By incorporating the zero-sequence current of the low-voltage side bushing, the zero-sequence current of the star connection on the high-voltage side is balanced, avoiding the differential distortion caused by the traditional high-voltage side zero-filter.

[0054] In this embodiment, the differential current calculation integrates the acquired data from four types of current transformers (CTs), specifically including: Current signal acquired by the high-voltage side current transformer (high-voltage side CT); Current signal acquired by the medium-voltage side current transformer (medium-voltage side CT); Current signal acquired by the low-voltage side winding current transformer (low-voltage winding CT); Current signal acquired by the low-voltage side switch current transformer (low-voltage switch CT).

[0055] The differential protection range of this calculation method is consistent with that of conventional longitudinal differential protection, and compared with phase-by-phase differential protection and local differential protection, it has a wider coverage, enabling comprehensive protection of the entire transformer winding and related circuits. Through the zero-sequence compensation design of the low-voltage side switch, the interference of zero-sequence current on the differential current calculation is offset, eliminating the need for additional zero-sequence filtering circuits or algorithms on the high-voltage and medium-voltage sides. Zero-sequence compensation accurately eliminates the influence of unbalanced zero-sequence components, allowing the differential current calculation to more accurately reflect the current changes during ground faults on the high- and medium-voltage sides, significantly improving the sensitivity of ground fault detection and avoiding missed fault detection. It avoids signal distortion caused by zero-sequence filtering algorithms, ensuring that the differential current data truly restores the actual state of the current on each side of the transformer, providing a more reliable basis for fault judgment and reducing the risk of protection maloperation.

[0056] Optionally, when the low-voltage side of the transformer is delta-connected and the fault occurs on the low-voltage switch side, the preset differential current calculation formula is as follows:

[0057]

[0058]

[0059] It is understandable that the differential current calculation formula is the same as the differential current calculation formula for phase correction of angular-to-star conversion, which is equivalent to the longitudinal differential protection of angular-to-star conversion.

[0060] In transformer protection, differential current refers to the vector sum of the currents flowing into the transformer protection device (after appropriate conversion). Under normal circumstances, the vector sum of the currents on all sides of the transformer is theoretically zero (ignoring unbalanced current). When a fault occurs inside the transformer, the vector sum of the currents on all sides will no longer be zero; this non-zero current is the differential current. By calculating the differential current and comparing it with the set operating value, it can be determined whether a transformer fault has occurred.

[0061] It should be noted that because the voltage levels on each side of the transformer are different, the magnitudes of the currents on each side also differ. In order to accurately compare the currents on each side in differential current calculations, it is necessary to convert the currents on each side to the same voltage level (usually the high-voltage side). The medium-voltage side current conversion factor and the low-voltage side current conversion factor are coefficients used to convert the currents on the medium-voltage side and the low-voltage side to the high-voltage side.

[0062] Optionally, the method of this application embodiment is applicable to transformers with voltage levels of 500kV and above, as well as transformers configured with low-winding current transformers; the method can be switched to any of the following protection modes according to the actual configuration of the transformer's current transformer: Longitudinal differential protection mode with zero-sequence compensation; Phase-separated differential protection mode; Conventional longitudinal differential protection mode.

[0063] Transformers with voltage levels of 500kV and above refer to power transformers with a rated voltage of 500 kV and above. These transformers are typically used in high-voltage and ultra-high-voltage transmission systems, undertaking important tasks of power transmission and transformation. Due to their high voltage level and large capacity, a fault in these transformers can have a wide impact and cause significant losses, thus requiring higher reliability and accuracy from protection devices. This method is applicable to these transformers and helps improve their protection performance.

[0064] Among them, the transformer derived from the low-voltage winding current transformer refers to the transformer that extracts the current signal through the low-voltage winding current transformer. The function of the current transformer is to transform the large current on the primary side into a small current on the secondary side according to a certain ratio, for use by protection devices, measuring instruments, etc.

[0065] Among them, the longitudinal differential protection mode with zero-sequence compensation refers to introducing zero-sequence compensation on the basis of longitudinal differential protection. Longitudinal differential protection is a protection method that compares the vector sum of the currents on each side of the transformer to determine the fault. The longitudinal differential protection mode with zero-sequence compensation, by considering the influence of zero-sequence current on differential current, performs compensation calculations on the relevant currents before performing differential comparison, which can more accurately detect internal faults in the transformer.

[0066] Among them, the phase-differential protection mode refers to a protection mode that provides differential protection for each of the three phases of the transformer. This involves calculating the differential current for each of phases A, B, and C separately, and setting separate operating criteria for each. When a phase meets the fault characteristics, the phase-differential protection mode can more accurately locate the faulty phase, exhibiting high sensitivity for detecting single-phase faults within the transformer, and preventing false tripping of other phase protections due to a fault in one phase.

[0067] Among them, the conventional longitudinal differential protection mode refers to the traditional transformer longitudinal differential protection method, which does not consider zero-sequence compensation factors. It performs zero filtering through the high-voltage side (star side), and then calculates the differential current after phase conversion and amplitude conversion. When the fault characteristics are met, the protection device operates to disconnect the transformer.

[0068] Step 105: Determine whether the transformer is faulty based on the calculated differential current.

[0069] It should be noted that when a transformer experiences an internal fault, the three-phase differential current can effectively reflect the fault situation and trip to cut off the fault current.

[0070] Specifically, differential protection operating conditions can be preset in the protection device. When the differential current meets the operating conditions, the protection device determines that a transformer fault has occurred. The microprocessor of the protection device compares the calculated differential current with the preset operating conditions. If the operating conditions are met, the protection is triggered, such as issuing a trip signal to disconnect the transformer; if the differential current does not meet the operating conditions, the device continues to monitor changes in the current on each side of the transformer. Simultaneously, the protection device can also be configured with auxiliary criteria, such as the restraining characteristics of the differential current, to improve the reliability and selectivity of the protection.

[0071] In this embodiment, the three-phase currents of the high-voltage side switch, medium-voltage side switch, low-voltage side switch, and low-voltage side bushing are first collected. Then, based on the low-voltage side bushing three-phase current, the zero-sequence current of the low-voltage side bushing is calculated. Next, based on the low-voltage side switch three-phase current and the low-voltage side bushing zero-sequence current, the low-voltage side switch three-phase current is compensated, and the compensated low-voltage side switch three-phase current is calculated. Then, based on the high-voltage side switch three-phase current, medium-voltage side switch three-phase current, and the compensated low-voltage side switch three-phase current, the differential current is calculated. Finally, the transformer fault is determined based on the calculated differential current. This allows for reliable identification of various types of transformer faults, solving the problems of differential distortion caused by zero-filtering in conventional differential protection and insufficient sensitivity to high-resistance grounding faults on the star side, greatly improving the safety and stability of transformer operation.

[0072] Figure 2 This is a flowchart describing the process of a transformer protection method based on zero-sequence compensation. The specific content is as follows: First, the switching current on all three sides of the transformer and the bushing current on the low-voltage side are simultaneously collected. Then, a low-voltage side switch check is performed to determine if a low-voltage side switch exists. If no low-voltage side switch exists, the system switches to phase-differential mode.

[0073] If a low-voltage side switch is present, proceed to the next step. Next, check if a low-voltage side bushing exists. If no low-voltage side bushing exists, switch to longitudinal differential mode. If a low-voltage side bushing exists, continue with the subsequent process. Then, calculate the zero-sequence current of the low-voltage side bushing. Based on the calculated low-voltage side bushing zero-sequence current, perform low-voltage side zero-sequence compensation calculation. Using the collected high-voltage side, medium-voltage side, and compensated low-voltage side bushing currents, calculate the transformer differential current. Based on the calculated differential current, execute the transformer differential protection logic. If the protection logic determines a fault exists, trip to disconnect the fault current. The entire flowchart describes the complete protection process from data acquisition to fault handling, switching different protection modes according to different equipment configurations to ensure effective protection of the transformer under various conditions.

[0074] In this embodiment, the differential current calculation method with zero-sequence compensation is applicable to most transformers of 500kV and above. However, for transformers without low-voltage side switch CTs, phase-by-phase differential protection is implemented using low-voltage side bushing CTs; for transformers without low-voltage side bushing CTs, longitudinal differential protection is implemented using low-voltage side switch CTs, and the new differential protection with zero-sequence compensation is no longer used. Therefore, automatic switching between compensated differential mode, phase-by-phase differential mode, and longitudinal differential mode can be achieved according to the transformer CT parameter settings.

[0075] In this embodiment, the novel transformer protection based on zero-sequence compensation is simulated and verified by establishing an RTDS (Real-Time Digital Simulator) simulation model of a 500kV three-phase split autotransformer.

[0076] In this embodiment, an RTDS simulation model is used to simulate a single-phase ground fault on the high-voltage side (star connection). The grounding resistance value is adjusted, and the sensitivity of the differential protection with zero-sequence compensation is tested and compared with that of conventional longitudinal differential protection and phase-by-phase differential protection. The verification data is shown in Table 1. When the grounding resistance is large, the fault current is small, and the longitudinal differential protection after zero-filtering cannot reflect the fault, so the protection does not operate. At this time, the differential protection with zero-sequence compensation has obvious advantages, and its sensitivity is significantly higher than that of conventional differential protection. Its operating behavior is basically the same as that of phase-by-phase differential protection, but its protection range is larger.

[0077]

[0078] Table 1 In this embodiment, an RTDS simulation model is used to simulate a phase-to-phase grounding fault on the low-voltage switch side (delta connection). The grounding resistance value is adjusted, and the sensitivity of the differential protection using zero-sequence compensation is tested and compared with that of conventional longitudinal differential protection. The verification data is shown in Table 2. When the grounding resistance value is small, the sensitivity of the differential protection using zero-sequence compensation is basically the same as that of conventional differential protection. When a phase-to-phase grounding fault occurs on the delta side, since there is no zero-sequence current in the delta side fault, the differential current calculation of the differential protection using zero-sequence compensation is equivalent to the longitudinal differential protection under the delta-to-star configuration, so its sensitivity is basically the same.

[0079]

[0080] Table 2 This invention proposes a novel differential protection method that replaces zero-sequence elimination with zero-sequence compensation. Employing longitudinal differential protection with zero-sequence compensation, it offers significant advantages over conventional longitudinal differential protection and phase-by-phase differential protection, including a larger protection range, higher sensitivity, and immunity to zero-sequence filtering. It reliably identifies various types of transformer faults and solves the problems of differential distortion caused by zero-sequence filtering in conventional differential protection and insufficient sensitivity to high-resistance grounding faults on the star side, greatly improving the safety and stability of transformer operation. Compared to conventional differential protection, this method has the following advantages: a larger protection range than phase-by-phase and small-area differential protection, and the same range as conventional longitudinal differential protection. It exhibits higher sensitivity to high and medium voltage side grounding faults, and the calculated differential current is more accurate and reliable. When a fault occurs on the delta side, the differential current calculation formula is the same as the differential current calculation formula for phase correction during delta-to-star conversion. It is equivalent to longitudinal differential protection for delta-to-star conversion.

[0081] To facilitate better implementation of the zero-sequence compensation-based transformer protection method of this disclosure, this disclosure also provides a zero-sequence compensation-based transformer protection device based on the above-described zero-sequence compensation-based transformer protection method. The meanings of the terms used are the same as in the above-described zero-sequence compensation-based transformer protection method, and specific implementation details can be found in the description of the method embodiments.

[0082] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of a transformer protection device based on zero-sequence compensation provided in an embodiment of this disclosure. The transformer protection device 200 based on zero-sequence compensation includes: The acquisition module 210 is used to acquire the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, the three-phase current of the low-voltage side switch, and the three-phase current of the low-voltage side bushing of the transformer. The first calculation module 220 is used to calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing. The second calculation module 230 is used to calculate the compensated three-phase current of the low-voltage side switch based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing. The third calculation module 240 is used to calculate the differential current based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch. The judgment module 250 is used to determine whether the transformer is faulty based on the calculated differential current.

[0083] Optionally, the second calculation module is specifically used for: Based on the phase relationship between the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing, the zero-sequence compensation formula is derived. Based on the zero-sequence compensation formula, zero-sequence compensation is performed on the three-phase current of the low-voltage side switch, and the compensated three-phase current of the low-voltage side switch is calculated. The zero-sequence compensation formula is as follows:

[0084]

[0085]

[0086] in, , , For the three-phase current of the low-voltage side switch, This refers to the zero-sequence current of the low-voltage side bushing. , , The three-phase current of the low-voltage side switch after compensation.

[0087] Optionally, the second calculation module is specifically used for: The differential current is calculated using a preset differential current calculation formula, the three-phase currents of the high-voltage side switch, the three-phase currents of the medium-voltage side switch, the compensated three-phase currents of the low-voltage side switch, the medium-voltage side current conversion factor, and the low-voltage side current conversion factor. The preset differential current calculation formula is as follows:

[0088]

[0089]

[0090] Among them, K M and K L These are the current reduction factors for the medium-voltage side and the low-voltage side, respectively. , , For the three-phase current of the high-voltage side switch, , , For the three-phase current of the medium-voltage side switch, , , This is the differential current.

[0091] Optionally, when the low-voltage side of the transformer is delta-connected and the fault occurs on the low-voltage switch side, the preset differential current calculation formula is as follows: , , .

[0092] Optionally, the device is applicable to transformers with voltage levels of 500kV and above, as well as transformers equipped with low-winding current transformers; the device can switch to any of the following protection modes according to the actual configuration of the transformer's current transformers: Longitudinal differential protection mode with zero-sequence compensation; Phase-separated differential protection mode; Conventional longitudinal differential protection mode.

[0093] In this embodiment, the three-phase currents of the high-voltage side switch, medium-voltage side switch, low-voltage side switch, and low-voltage side bushing are first collected. Then, based on the low-voltage side bushing three-phase current, the zero-sequence current of the low-voltage side bushing is calculated. Next, based on the low-voltage side switch three-phase current and the low-voltage side bushing zero-sequence current, the low-voltage side switch three-phase current is compensated, and the compensated low-voltage side switch three-phase current is calculated. Then, based on the high-voltage side switch three-phase current, medium-voltage side switch three-phase current, and the compensated low-voltage side switch three-phase current, the differential current is calculated. Finally, the transformer fault is determined based on the calculated differential current. This allows for reliable identification of various types of transformer faults, solving the problems of differential distortion caused by zero-filtering in conventional differential protection and insufficient sensitivity to high-resistance grounding faults on the star side, greatly improving the safety and stability of transformer operation.

[0094] In addition, this disclosure also provides an electronic device, such as Figure 4 As shown, it illustrates a schematic diagram of the structure of the electronic device involved in this disclosure, specifically: The electronic device may include components such as a processor 401 with one or more processing cores, a memory 402 with one or more computer-readable storage media, a power supply 403, and an input unit 404. Those skilled in the art will understand that... Figure 4 The electronic device structure shown does not constitute a limitation on the electronic device and may include more or fewer components than shown, or combine certain components, or have different component arrangements. Wherein: The processor 401 is the control center of the electronic device. It connects various parts of the electronic device via various interfaces and lines. By running or executing software programs and / or modules stored in the memory 402, and by calling data stored in the memory 402, it performs various functions and processes data, thereby providing overall monitoring of the electronic device. Optionally, the processor 401 may include one or more processing cores; preferably, the processor 401 may integrate an application processor and a modem processor, wherein the application processor mainly handles the operating system, user interface, and applications, and the modem processor mainly handles wireless communication. It is understood that the modem processor may not be integrated into the processor 401.

[0095] The memory 402 can be used to store software programs and modules. The processor 401 executes various functional applications and data processing by running the software programs and modules stored in the memory 402. The memory 402 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the electronic device, etc. In addition, the memory 402 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, the memory 402 may also include a memory controller to provide the processor 401 with access to the memory 402.

[0096] The electronic device also includes a power supply 403 that supplies power to the various components. Preferably, the power supply 403 can be logically connected to the processor 401 through a power management system, thereby enabling functions such as charging, discharging, and power consumption management through the power management system. The power supply 403 may also include one or more DC or AC power supplies, recharging systems, power equipment debugging circuits, power converters or inverters, power status indicators, and other arbitrary components.

[0097] The electronic device may also include an input unit 404, which can be used to receive input digital or character information, and generate keyboard, mouse, joystick, optical or trackball signal inputs related to user settings and function control.

[0098] Although not shown, the electronic device may also include a display unit, etc., which will not be described in detail here. Specifically, in this embodiment, the processor 401 in the electronic device loads the executable files corresponding to the processes of one or more application programs into the memory 402 according to the following instructions, and the processor 401 runs the application programs stored in the memory 402, thereby implementing the steps in any of the transformer protection methods based on zero-sequence compensation provided in the embodiments of this disclosure.

[0099] In this embodiment, the three-phase currents of the high-voltage side switch, medium-voltage side switch, low-voltage side switch, and low-voltage side bushing are first collected. Then, based on the low-voltage side bushing three-phase current, the zero-sequence current of the low-voltage side bushing is calculated. Next, based on the low-voltage side switch three-phase current and the low-voltage side bushing zero-sequence current, the low-voltage side switch three-phase current is compensated, and the compensated low-voltage side switch three-phase current is calculated. Then, based on the high-voltage side switch three-phase current, medium-voltage side switch three-phase current, and the compensated low-voltage side switch three-phase current, the differential current is calculated. Finally, the transformer fault is determined based on the calculated differential current. This allows for reliable identification of various types of transformer faults, solving the problems of differential distortion caused by zero-filtering in conventional differential protection and insufficient sensitivity to high-resistance grounding faults on the star side, greatly improving the safety and stability of transformer operation.

[0100] For details on the implementation of each of the above operations, please refer to the previous examples, which will not be repeated here.

[0101] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0102] To this end, this disclosure provides a computer-readable storage medium storing a computer program that can be loaded by a processor to perform the steps in any of the transformer protection methods based on zero-sequence compensation provided in this disclosure.

[0103] For details on the implementation of each of the above operations, please refer to the previous examples, which will not be repeated here.

[0104] The computer-readable storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0105] Since the instructions stored in the computer-readable storage medium can execute the steps of any of the transformer protection methods based on zero-sequence compensation provided in this disclosure, the beneficial effects that any of the transformer protection methods based on zero-sequence compensation provided in this disclosure can achieve can be realized, as detailed in the preceding embodiments, and will not be repeated here.

[0106] The present disclosure provides a detailed description of a transformer protection method, apparatus, electronic device, and computer-readable storage medium based on zero-sequence compensation. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A transformer protection method based on zero-sequence compensation, characterized in that, include: Collect the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, the three-phase current of the low-voltage side switch, and the three-phase current of the low-voltage side bushing of the transformer; Calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing: Based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing, the three-phase current of the low-voltage side switch is compensated and the compensated three-phase current of the low-voltage side switch is calculated. The differential current is calculated based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch. The transformer is determined to be faulty based on the calculated differential current.

2. The method according to claim 1, characterized in that, The calculation of the compensated three-phase current of the low-voltage side switch based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing includes: Based on the phase relationship between the three-phase current of the low-voltage side switch and the three-phase current of the low-voltage side bushing, the zero-sequence compensation formula is derived. Based on the zero-sequence compensation formula, zero-sequence compensation is performed on the three-phase current of the low-voltage side switch, and the compensated three-phase current of the low-voltage side switch is calculated. The zero-sequence compensation formula is as follows: in, , , For the three-phase current of the low-voltage side switch, This refers to the zero-sequence current of the low-voltage side bushing. , , The three-phase current of the low-voltage side switch after compensation.

3. The method according to claim 2, characterized in that, The differential current is calculated based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch, including: The differential current is calculated using a preset differential current calculation formula, the three-phase currents of the high-voltage side switch, the three-phase currents of the medium-voltage side switch, the compensated three-phase currents of the low-voltage side switch, the medium-voltage side current conversion factor, and the low-voltage side current conversion factor. The preset differential current calculation formula is as follows: Among them, K M and K L These are the current reduction factors for the medium-voltage side and the low-voltage side, respectively. , , For the three-phase current of the high-voltage side switch, , , For the three-phase current of the medium-voltage side switch, , , This is the differential current.

4. The method according to claim 3, characterized in that, in, When the low-voltage side of the transformer is delta-connected and the fault occurs on the low-voltage switch side, the preset differential current calculation formula is as follows: ， ， 。 5. The method according to claim 1, characterized in that, The method is applicable to transformers with voltage levels of 500kV and above, as well as transformers equipped with low-winding current transformers; the method can be switched to any of the following protection modes according to the actual configuration of the transformer's current transformers: Longitudinal differential protection mode with zero-sequence compensation; Phase-separated differential protection mode; Conventional longitudinal differential protection mode.

6. A transformer protection device based on zero-sequence compensation, characterized in that, include: The data acquisition module is used to acquire the three-phase current of the high-voltage side switch, the medium-voltage side switch, the low-voltage side switch, and the low-voltage side bushing. The first calculation module is used to calculate the zero-sequence current of the low-voltage side bushing based on the three-phase current of the low-voltage side bushing. The second calculation module is used to compensate the three-phase current of the low-voltage side switch and calculate the compensated three-phase current of the low-voltage side switch based on the three-phase current of the low-voltage side switch and the zero-sequence current of the low-voltage side bushing. The third calculation module is used to calculate the differential current based on the three-phase current of the high-voltage side switch, the three-phase current of the medium-voltage side switch, and the compensated three-phase current of the low-voltage side switch. The transformer is determined to be faulty based on the calculated differential current.

7. The apparatus according to claim 6, characterized in that, The second calculation module is specifically used for: Based on the phase relationship between the three-phase current of the low-voltage side switch and the three-phase current of the low-voltage side bushing, the zero-sequence compensation formula is derived. Based on the zero-sequence compensation formula, zero-sequence compensation is performed on the three-phase current of the low-voltage side switch, and the compensated three-phase current of the low-voltage side switch is calculated. The zero-sequence compensation formula is as follows: in, , , For the three-phase current of the low-voltage side switch, This refers to the zero-sequence current of the low-voltage side bushing. , , The three-phase current of the low-voltage side switch after compensation.

8. The apparatus according to claim 7, characterized in that, The second calculation module is specifically used for: The differential current is calculated using a preset differential current calculation formula, the three-phase currents of the high-voltage side switch, the three-phase currents of the medium-voltage side switch, the compensated three-phase currents of the low-voltage side switch, the medium-voltage side current conversion factor, and the low-voltage side current conversion factor. The preset differential current calculation formula is as follows: Among them, K M and K L These are the current reduction factors for the medium-voltage side and the low-voltage side, respectively. , , For the three-phase current of the high-voltage side switch, , , For the three-phase current of the medium-voltage side switch, , , This is the differential current.

9. An electronic device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method as described in any one of claims 1-5.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program, which is loaded by a processor to perform the method according to any one of claims 1 to 5.

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