Early warning method and system for turn-to-turn short circuit fault of distribution transformer winding

Abstract

The invention relates to an early warning method and system for a turn-to-turn short circuit fault of a distribution transformer winding, and the method comprises the steps: obtaining the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculating the maximum value of the dynamic power loss change rate, the maximum value of the voltage change rate and the maximum value of the main current change rate during the operation of the winding; when the oil pressure and the oil level are within a set range, and the maximum voltage change rate and the main current change rate are smaller than set threshold values respectively, corresponding signals are sent out according to the oil temperature and winding loss change conditions. The current, the voltage, the oil temperature, the oil level and the oil pressure obtained from the distribution transformer winding are utilized, the current change rate, the voltage change rate and the power loss change rate obtained through calculation are combined, multiple parameters are comprehensively considered, and the condition of the winding turn-to-turn short circuit fault is early warned. Compared with the prior art that only current change and power loss are considered, the method can more accurately perform early warning on the possible winding turn-to-turn short circuit fault.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an early warning method and system for a distribution transformer winding turn-to-turn short-circuit fault. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] There are a large number of distribution transformers (hereinafter referred to as distribution transformers) in the power system, which are widely distributed and numerous. According to relevant statistics, most of the distribution transformer faults are caused by short circuits between winding turns. The short circuit between winding turns is a fault caused by insulation degradation during the operation of the distribution transformer. Although the existing technology can use some parameters in the operation of the distribution transformer (such as current change rate, power loss, etc.) to identify the insulation degradation phenomenon that may occur during the operation of the distribution transformer, thereby realizing fault identification, the accuracy of identification is not ideal. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides an early warning method and system for short-circuit faults between turns of a distribution transformer winding, which uses the current change rate, voltage change rate, oil temperature, oil pressure, oil level and power loss change rate of the distribution transformer winding to warn of the occurrence of short-circuit faults between turns of the winding.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides an early warning method for a distribution transformer winding turn-to-turn short-circuit fault, comprising the following steps:

[0007] Obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, voltage change rate and main current change rate during winding operation;

[0008] When the oil pressure and oil level are within the set range, and the maximum voltage change rate and the main current change rate are respectively less than the set thresholds, corresponding signals are issued according to the changes in oil temperature and winding loss, specifically:

[0009] When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued;

[0010] When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued;

[0011] When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

[0012] Furthermore, the dynamic power loss value and maximum value change rate of a phase winding of the transformer are calculated through the simulation model.

[0013] Furthermore, during the simulation calculation, the maximum value of the rate of change X = (actual measured value x-rated value x n ) / rated value x n .

[0014] Furthermore, during the simulation calculation, the inter-turn insulation resistance value corresponding to the measured maximum operating loss is found through the relationship curve of the inter-turn insulation resistance-winding dynamic power loss maximum value change rate and the numerical relationship between the maximum value of the winding loss change rate and the insulation state, so as to determine the deterioration level of the inter-turn insulation of the transformer when an inter-turn short circuit fault occurs.

[0015] Furthermore, when the oil pressure is between 0.2-0.5MPa, the oil level is between 50%-70% of the total volume of the oil tank, the voltage change rate is less than 4%, and the main current change rate is less than 10%, corresponding signals are issued according to the changes in oil temperature and winding loss.

[0016] Furthermore, the first oil temperature threshold is 85°C, and the second oil temperature threshold is 108°C.

[0017] Furthermore, the first loss threshold is 5%, and the second loss threshold is 15%.

[0018] A second aspect of the present invention provides an early warning system for a distribution transformer winding turn-to-turn short-circuit fault, comprising:

[0019] The data acquisition unit is configured to: obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, the maximum voltage change rate and the maximum main current change rate when the winding is running;

[0020] The early warning signal unit is configured to send corresponding signals according to the changes in oil temperature and winding loss when the oil pressure and oil level are within the set range and the maximum voltage change rate and the main current change rate are respectively less than the set thresholds, specifically:

[0021] When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued;

[0022] When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued;

[0023] When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

[0024] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above-mentioned early warning method for inter-turn short-circuit faults in the windings of a distribution transformer.

[0025] The fourth aspect of the present invention provides a computer 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, the steps in the above-mentioned early warning method for inter-turn short-circuit fault of the distribution transformer winding are implemented.

[0026] Compared with the prior art, one or more of the above technical solutions have the following beneficial effects:

[0027] By using the current, voltage, oil temperature, oil level and oil pressure obtained from the distribution transformer winding, combined with the calculated current change rate, voltage change rate and power loss change rate, and comprehensively considering multiple parameters, an early warning is given for the occurrence of a winding turn-to-turn short-circuit fault. Compared with the existing technology that only considers the current change and power loss, it can more accurately warn of possible winding turn-to-turn short-circuit faults, and can visualize the turn-to-turn insulation status without disassembling the actual transformer or setting a fault for the actual transformer, so as to facilitate early detection of faults and take corresponding preventive measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 It is a schematic diagram of a flow chart of a distribution transformer winding turn-to-turn short-circuit fault warning provided by one or more embodiments of the present invention;

[0030] Figure 2 It is a schematic diagram of a curve showing the relationship between the inter-turn insulation resistance of a winding and the rate of change of the maximum value of the dynamic power loss of the winding provided by one or more embodiments of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] As introduced in the background technology, although the existing technology can use some parameters in the distribution transformer operation (such as current change rate, power loss, etc.) to identify possible insulation degradation phenomena, thereby realizing the identification of inter-turn short-circuit faults, the identification accuracy is not ideal.

[0034] Therefore, the following embodiments provide an early warning and system for a short-circuit fault between turns of a distribution transformer winding. The electromagnetic transient process when the insulation between turns of the distribution transformer is degraded is reproduced through a simulation model. According to the change of the maximum value of the dynamic power loss of the winding between turns of the winding, the temperature change and oil temperature change of the corresponding winding, and the voltage change rate or current change rate, a warning is given for a possible short-circuit fault between turns of the winding by comprehensive consideration of multiple parameters.

[0035] Embodiment 1:

[0036] The early warning method for the inter-turn short circuit fault of the distribution transformer winding comprises the following steps:

[0037] Obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, the maximum voltage change rate and the maximum main current change rate during winding operation;

[0038] When the oil pressure and oil level are within the set range, and the maximum voltage change rate and the main current change rate are less than the set thresholds, there are three cases:

[0039] (1) When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued;

[0040] (2) When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued;

[0041] (3) When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

[0042] Based on the Maxwell finite element simulation software, a "field-circuit" coupled insulation degradation 3D simulation model consistent with the actual transformer geometry was built, and each phase winding on each side was constructed in layers and turns according to actual conditions.

[0043] By setting the inter-turn insulation resistance Rdld of a phase winding in the external circuit of the model to gradually decrease, the electromagnetic transient process when the inter-turn insulation of the distribution transformer deteriorates is simulated and reproduced. The dynamic power loss value and the maximum value change rate of the phase winding of the transformer are calculated by simulation. The relationship curve of the inter-turn insulation resistance of the phase winding-the maximum value change rate of the dynamic power loss of the winding can be drawn. The change law of the dynamic power loss change rate of each phase winding of the distribution transformer with the degradation of the inter-turn insulation resistance is analyzed and studied, and the numerical relationship between the critical resistance value and the loss change rate of inter-turn insulation degradation and insulation collapse and the inter-turn insulation state is obtained. At the same time, the winding temperature change and oil temperature change when the inter-turn insulation deteriorates are simulated and studied, which further provides a strong basis for the early warning of inter-turn insulation degradation, thereby realizing the online monitoring and real-time early warning of the inter-turn insulation degradation of the distribution transformer.

[0044] In this embodiment, a "field-circuit" coupled insulation degradation 3D simulation model consistent with the actual transformer geometry is built based on Maxwell finite element simulation software, and each phase winding on each side is constructed in layers and turns according to actual conditions.

[0045] Specifically, by setting the inter-turn insulation resistance Rdld of a phase winding in the external circuit of the model to gradually decrease, the electromagnetic transient process when the inter-turn insulation of the distribution transformer deteriorates is simulated and reproduced, the dynamic power loss value and the maximum value change rate of the phase winding of the transformer are simulated and calculated accordingly, and a relationship curve between the inter-turn insulation resistance of the phase winding and the maximum value change rate of the winding dynamic power loss is drawn, as shown in Figure 2 shown.

[0046] The dynamic power loss change rate of each phase winding of the distribution transformer is analyzed and studied as the inter-turn insulation resistance deteriorates, and the critical resistance value of inter-turn insulation degradation and insulation collapse, as well as the numerical relationship between the loss change rate and the inter-turn insulation state are obtained, as shown in Table 1.

[0047] Table 1 Numerical relationship between the maximum value of winding loss change rate and insulation state

[0048] Maximum value of winding loss change rate x Turn insulation resistance R Insulation status x＜5％ R>100mΩ Turn insulation normal x≈5％ R≈100mΩ Critical degradation value 5％＜x＜15％ 10mΩ<R<100mΩ Turn insulation degradation x≈15％ R≈10mΩ Critical collapse value x＞15％ R<10mΩ Turn insulation breakdown

[0049] The simulation study of the winding temperature change and oil temperature change when the inter-turn insulation deteriorates further provides a powerful basis for the early warning of inter-turn insulation degradation.

[0050] According to the above process, an early warning method for deterioration of insulation between turns of winding is realized, such as Figure 1 As shown, the following steps are included:

[0051] Obtain the voltage and current values ​​of the high- and low-voltage side windings, and calculate the dynamic power loss and total loss of the winding operation.

[0052] According to the formula: Maximum value of change rate X = (actual measured value x-rated value x n) / rated value x n The maximum value of the winding dynamic power loss change rate, the main current change rate and the voltage change rate are calculated.

[0053] Look up the inter-turn insulation resistance value corresponding to the measured maximum operating loss value on the inter-turn insulation resistance-winding dynamic power loss maximum change rate relationship curve and the winding loss change rate maximum value-insulation state numerical relationship table to determine the inter-turn insulation degradation level of the transformer when an inter-turn short circuit fault occurs. Figure 1 As shown in Table 1.

[0054] Furthermore, the distribution operation and maintenance personnel, based on the inter-turn insulation degradation level, perceive the inter-turn insulation status of the distribution transformer winding in real time according to the oil pressure, oil level, oil temperature changes, voltage change rate, main current change rate and loss change rate, and predict the inter-turn insulation degradation.

[0055] In this embodiment, when the oil pressure is between 0.2-0.5MPa, the oil level is between 50%-70% of the oil tank high and low marking lines, the voltage change rate is less than 4%, and the main current change rate is less than 10%, there are three cases as follows:

[0056] (1) When the oil temperature is less than 85°C (the first oil temperature threshold) and the maximum value of the winding loss change rate is less than 5% (the first loss threshold), it means that the turn-to-turn insulation is in good condition and no additional maintenance is required;

[0057] (2) When the oil temperature is greater than 85°C (the first oil temperature threshold) and less than 108°C (the second oil temperature threshold), and the maximum value of the winding loss change rate is greater than 5% (the first loss threshold) and less than 15% (the second loss threshold), it indicates that the inter-turn insulation has deteriorated, and an early warning signal is issued to prompt the operation and maintenance personnel to handle it in time to avoid failure;

[0058] (3) When the oil temperature is greater than 108°C and the maximum value of the winding loss change rate is greater than 15%, it indicates that the inter-turn insulation collapses, that is, an inter-turn short-circuit fault occurs, and a fault trip command is issued, prompting the operation and maintenance personnel to conduct a comprehensive maintenance of the distribution transformer to avoid accidents.

[0059] The addition of parameters such as oil temperature, oil pressure, and voltage change rate makes the early warning results of inter-turn insulation degradation more accurate and reliable, and these parameters can be measured in real time without adding additional equipment. The prediction can be improved through multi-parameter analysis and comprehensive consideration to avoid unnecessary losses caused by misjudgment.

[0060] Specifically, when the distribution operation and maintenance personnel find that the oil temperature change and dynamic power loss change rate of the distribution transformer reach the insulation degradation value in the method, combined with the oil pressure, oil level, voltage change rate and main circuit current change value, they can intelligently sense and monitor the insulation degradation of the distribution transformer turn-to-turn online, quickly predict, and accurately locate the degraded phase, and realize the function of real-time warning. It is convenient to take preventive measures in advance, and then realize the function of online monitoring of the insulation degradation of the distribution transformer turn-to-turn and real-time warning. It can also be combined with the analysis of multiple parameters when the corresponding signal is issued, and the recovery of insulation performance can be evaluated and mastered in real time. If the test finds that the data is still in the warning range, it means that the recovery is poor and needs to be repaired in time. If the test result is in the good insulation range, it means that the recovery is good and can operate normally. It helps to improve the operation and maintenance of the distribution network and reliability.

[0061] The above process can visualize the inter-turn insulation status without disassembling the actual transformer or setting faults for the actual transformer. It can sense and predict accurately in real time when the equipment is running, so as to take preventive measures in advance. The implementation of the advanced operation is simple and low-cost, and will not cause additional impact on the original system. It meets the needs of distribution network operation and maintenance personnel for integration, safety, and digitization, and helps to improve the intelligence of distribution equipment.

[0062] Embodiment 2:

[0063] The early warning system for inter-turn short-circuit fault of distribution transformer windings includes:

[0064] The data acquisition unit is configured to: obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, the maximum voltage change rate and the maximum main current change rate when the winding is running;

[0065] The early warning signal unit is configured to send corresponding signals according to the changes in oil temperature and winding loss when the oil pressure and oil level are within the set range and the maximum voltage change rate and the main current change rate are respectively less than the set thresholds, specifically:

[0066] When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued;

[0067] When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued;

[0068] When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

[0069] Embodiment three:

[0070] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps in the early warning method for inter-turn short-circuit fault of a distribution transformer winding as described in the above-mentioned embodiment 2 are implemented.

[0071] Embodiment 4:

[0072] This embodiment provides 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, the steps in the early warning method for inter-turn short-circuit fault of a distribution transformer winding as described in the above-mentioned embodiment 2 are implemented.

[0073] The steps involved in the above embodiments 2 to 4 correspond to those in embodiment 1. For the specific implementation, please refer to the relevant description of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An early warning method for a short-circuit fault in a distribution transformer winding, characterized in that: The following steps are involved: Obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, voltage change rate and main current change rate during winding operation; When the oil pressure and oil level are within the set range, and the maximum voltage change rate and the main current change rate are respectively less than the set thresholds, corresponding signals are issued according to the changes in oil temperature and winding loss, specifically: When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued; When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued; When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

2. The early warning method for inter-turn short-circuit fault of a distribution transformer winding according to claim 1, characterized in that: The dynamic power loss value and maximum value change rate of a phase winding of the transformer are calculated through the simulation model.

3. The early warning method for inter-turn short-circuit fault of distribution transformer winding according to claim 2, characterized in that: During the simulation calculation, the maximum value of the rate of change X = (actual measured value x-rated value x n ) / rated value x n .

4. The early warning method for inter-turn short-circuit fault of a distribution transformer winding according to claim 2, characterized in that: During the simulation calculation, the inter-turn insulation resistance value corresponding to the measured maximum operating loss is found from the relationship curve of the inter-turn insulation resistance-winding dynamic power loss maximum value change rate and the numerical relationship between the maximum value of the winding loss change rate and the insulation state, so as to determine the deterioration level of the inter-turn insulation of the transformer when an inter-turn short circuit fault occurs.

5. The early warning method for inter-turn short-circuit fault of distribution transformer winding according to claim 1, characterized in that: When the oil pressure is between 0.2-0.5MPa, the oil level is between 50%-70% of the total volume of the tank, the voltage change rate is less than 4%, and the main current change rate is less than 10%, corresponding signals are sent out according to the changes in oil temperature and winding loss.

6. The early warning method for inter-turn short-circuit fault of a distribution transformer winding according to claim 1, characterized in that: The first oil temperature threshold is 85°C, and the second oil temperature threshold is 108°C.

7. The early warning method for inter-turn short-circuit fault of a distribution transformer winding according to claim 1, characterized in that: The first loss threshold is 5%, and the second loss threshold is 15%.

8. An early warning system for short-circuit faults in the windings of a distribution transformer, characterized in that: include: The data acquisition unit is configured to: obtain the current, voltage, oil temperature, oil pressure and oil level of the distribution transformer winding, and calculate the maximum dynamic power loss change rate, the maximum voltage change rate and the maximum main current change rate when the winding is running; The early warning signal unit is configured to send corresponding signals according to the changes in oil temperature and winding loss when the oil pressure and oil level are within the set range and the maximum voltage change rate and the main current change rate are respectively less than the set thresholds, specifically: When the oil temperature is lower than the first oil temperature threshold and the maximum value of the winding loss change rate is lower than the first loss threshold, a prompt signal indicating that "the inter-turn insulation is in good condition" is issued; When the oil temperature is between the first oil temperature threshold and the second oil temperature threshold, and the maximum value of the winding loss change rate is between the first loss threshold and the second loss threshold, an early warning signal of "inter-insulation degradation" is issued; When the oil temperature is greater than the second oil temperature threshold and the maximum value of the winding loss change rate is greater than the second loss threshold, a warning signal of "turn-to-turn short circuit fault occurs" is issued, and a fault trip command is issued.

9. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the program is executed by a processor, the steps in the early warning method for inter-turn short-circuit fault of a distribution transformer winding are implemented as described in any one of claims 1 to 7.

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps in the early warning method for inter-turn short-circuit fault of a distribution transformer winding are implemented as described in any one of claims 1 to 7.

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