On-load Tap Changer Protection Device and Method Based on Comprehensive Feature Quantities

Abstract

On-load tap-changer protection device and method based on comprehensive characteristic quantities, including an oil pressure starting unit, a strain starting unit, a deflection starting unit, a deflection protection unit, a tripping unit, and an explosion-proof unit capable of absorbing energy; the oil pressure starting unit is connected to the strain starting unit, the explosion-proof unit is connected to the strain starting unit, the strain starting unit is connected to the deflection starting unit, the deflection starting unit is connected to the deflection protection unit, and the deflection protection unit is connected to the tripping unit. The invention comprehensively utilizes multiple characteristic quantities such as the insulating oil pressure, the strain of the explosion-proof unit, and the deflection of the on-load tap-changer top cover to jointly realize the fault discrimination of the on-load tap-changer, improving the overall mechanical performance of the on-load tap-changer and the accuracy and reliability of fault discrimination. At the same time, the sensors used in the device meet the complex environment of high temperature, oil contamination, and strong electromagnetic fields inside the on-load tap-changer in terms of both accuracy and application range.

Description

Technical Field

[0001] The invention belongs to the technical field of non - electrical quantity protection of on - load tap - changers in power systems, and particularly relates to an on - load tap - changer protection device and method based on comprehensive characteristic quantities. Background Technique

[0002] With the rapid development of UHV DC transmission projects, as a key equipment for electric energy transmission, the stable operation of converter transformers plays an important role in aspects such as the reliable transportation of the power grid and the flexible distribution of electric energy. The converter transformer is the core equipment for energy conversion and transmission in the converter station, and the on - load tap - changer is an important component of the converter transformer.

[0003] The on - load tap - changer plays important roles in the power system, such as regulating reactive power, compensating for grid - side voltage fluctuations, and stabilizing DC voltage. It is the only movable component inside the converter transformer. With the frequent switching of the on - load tap - changer during the voltage regulation process of the converter transformer, there will be multiple charged arcing inside the on - load tap - changer, accompanied by the generation of gas due to the deterioration of insulating oil, the increase of internal pressure in the tap - changer, and the significant decline of the insulating performance of the insulating oil, which is extremely likely to cause internal short - circuit faults. Statistics show that abnormal on - load tap - changers cause more than 20% of transformer faults, and are often accompanied by deformation and rupture of the top cover of the on - load tap - changer, resulting in huge economic losses. At the same time, although the pressure relief valves and electrical quantity protections of some faulty on - load tap - changers operate correctly, the explosion and rupture accidents of on - load tap - changers are still difficult to avoid. Therefore, there is an urgent need for a relay protection device and method that can quickly and effectively identify internal faults of on - load tap - changers, realize fault discrimination and excision, and at the same time cut off the evolution process of internal faults of the tap - changer into accidents. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide an on - load tap - changer protection device and method based on comprehensive characteristic quantities, which are used to monitor and analyze comprehensive information such as the strain characteristics of porous metal materials inside the on - load tap - changer, the pressure characteristics of insulating oil, and the deflection change characteristics of the top cover of the on - load tap - changer, so as to realize the discrimination and excision of faults of the on - load tap - changer.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The on - load tap - changer protection device based on comprehensive characteristic quantities includes an oil - pressure starting unit, a strain starting unit, a deflection starting unit, a deflection protection unit, a tripping unit, and an explosion - proof unit capable of absorbing energy;

[0007] The oil - pressure starting unit is connected to the strain starting unit, the explosion - proof unit is connected to the strain starting unit, the strain starting unit is connected to the deflection starting unit, the deflection starting unit is connected to the deflection protection unit, and the deflection protection unit is connected to the tripping unit.

[0008] Further, the oil pressure starting unit includes a first judging element, a first connecting wire, and an insulating oil pressure sensor. The insulating oil pressure sensor is connected to the first judging element through the first connecting wire, and the first judging element is connected to the strain starting unit.

[0009] Further, the strain starting unit includes a strain sensor and a second judging element connected to each other, and the second judging element is connected to the deflection starting unit.

[0010] Further, the explosion-proof unit includes a layered honeycomb copper, which includes a front panel, a first-layer honeycomb copper, and a second-layer honeycomb copper. The second-layer honeycomb copper is welded to the front panel, and the first-layer honeycomb copper is welded to the top cover of the on-load tap-changer; the strain sensor is arranged between the first-layer honeycomb copper and the second-layer honeycomb copper.

[0011] Further, the density of the first-layer honeycomb copper is 0.60 g / cm 3 , and the density of the second-layer honeycomb copper is 0.30 g / cm 3 .

[0012] Further, the deflection starting unit includes a third judging element, a third connecting wire, and a laser displacement sensor. The laser displacement sensor is connected to the third judging element through the third connecting wire, and the third judging element is connected to the deflection protection unit.

[0013] Further, the sampling frequency of the laser displacement sensor is 10 kHz; the laser displacement sensor measures the deflection change of the top cover of the on-load tap-changer by the triangulation method.

[0014] Further, the deflection protection unit includes a fourth judging element, a fourth connecting wire, and a deflection full amount calculating element. The deflection full amount calculating element is connected to the fourth judging element through the fourth connecting wire, and the fourth judging element is connected to the tripping unit.

[0015] The on-load tap-changer protection method based on the comprehensive characteristic quantity of the above-mentioned device includes the following steps:

[0016] Step 1: Measure the insulating oil pressure inside the on-load tap-changer to obtain the real-time oil pressure characteristic quantity;

[0017] Step 2: Judge whether the amplitude of the real-time oil pressure characteristic quantity exceeds the oil pressure starting threshold value through the oil pressure starting unit. If it exceeds the oil pressure starting threshold value, go to Step 3; otherwise, return to Step 1;

[0018] Step 3: Measure the real-time strain characteristic of the layered honeycomb copper through the strain sensor to obtain the real-time strain characteristic quantity;

[0019] Step 4: Judge whether the amplitude of the real-time strain characteristic quantity exceeds the strain starting threshold value. If it exceeds the strain starting threshold value, go to Step 5; otherwise, return to Step 1;

[0020] Step 5: Measure the deflection change on the outer side of the on-load tap-changer top cover in real time through a laser displacement sensor to obtain the real-time top cover deflection characteristic quantity;

[0021] Step 6: Calculate the real-time total deflection according to the real-time top cover deflection characteristic quantity, and judge whether the amplitude of the real-time total deflection exceeds the starting threshold of the deflection starting unit. If it exceeds the starting threshold of the deflection starting unit, go to Step 7; otherwise, return to Step 1.

[0022] Step 7: Judge whether the amplitude of the real-time total deflection exceeds the action threshold of the deflection protection unit. If it exceeds the action threshold of the deflection protection, go to Step 8; otherwise, return to Step 1;

[0023] Step 8: The tripping unit issues a deflection tripping signal and stores the transient oil pressure, strain, and deflection data within 500 ms before and after the tripping.

[0024] Furthermore, the real-time total deflection Y op (t) is calculated by the following formula:

[0025]

[0026] where T is the data window length, i = 1, 2,..N is the deflection measurement point number, and Y ms,i (t) is the instantaneous deflection measured at the i-th measurement point at time t.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention utilizes the explosion-proof unit to absorb energy and reduce the internal oil pressure of the on-load tap-changer. By forming a sandwich structure in close connection with the on-load tap-changer, the overall pressure-bearing limit of the tap-changer is improved, and at the same time, the impact on the tap-changer is alleviated. The overall explosion-proof unit has a simple structure and is easy to implement, and the sealed sandwich structure also meets the oil-immersed environment of the tap-changer.

[0029] The present invention comprehensively utilizes multiple characteristic quantities such as the pressure of insulating oil, the strain of the explosion-proof unit, and the deflection of the on-load tap-changer top cover to jointly realize the fault discrimination of the on-load tap-changer, improving the overall mechanical performance of the on-load tap-changer and the accuracy and reliability of fault discrimination. At the same time, the sensors used in the device meet the complex environment of high temperature, oil pollution, and strong electromagnetic fields inside the on-load tap-changer in terms of both accuracy and application range. The device of the present invention is independent of the power system and does not generate harmonic interference during operation and use, and does not affect the operation of the power system. Brief Description of the Drawings

[0030] Figure 1 It is a schematic diagram of an on-load tap-changer protection device containing porous metal materials based on comprehensive characteristic quantities.

[0031] Figure 2 It is a partial schematic diagram of the explosion-proof unit.

[0032] Figure 3 It is the logic flow chart of the present invention.

[0033] Figure 4 It is the measured instantaneous oil pressure result diagram of the present invention.

[0034] Figure 5 It is the measured deflection result diagram of the present invention.

[0035] Figure 6 It is the measured strain result diagram of the present invention.

[0036] In the figure, 1 is the oil pressure start unit, 2 is the explosion-proof unit, 3 is the strain start unit, 4 is the deflection start unit, 5 is the deflection protection unit, 6 is the trip unit, 7 is the layered honeycomb copper, 8 is the on-load tap-changer top cover, 9 is the transformer oil tank, 10 is the front panel, 11 is the strain sensor, 12 is the first layer of honeycomb copper, and 13 is the second layer of honeycomb copper. Detailed implementation manners

[0037] The present invention will be described in detail below with reference to the accompanying drawings.

[0038] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant accompanying drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0039] In addition, the elements in the present invention are referred to as "fixed to" or "disposed on" another element, and it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0040] Referring to Figure 1 , the on-load tap-changer protection device based on the comprehensive characteristic quantity includes an oil pressure start unit 1, an explosion-proof unit 2, a strain start unit 3, a deflection start unit 4, a deflection protection unit 5 and a trip unit 6. Among them, the tap-changer is an important component of the transformer and is located inside the transformer oil tank 9, and the on-load tap-changer top cover 8 is located at the top of the tap-changer.

[0041] The oil pressure starting unit 1 is connected to the strain starting unit 3, the explosion-proof unit 2 is connected to the strain starting unit 3, the strain starting unit 3 is connected to the deflection starting unit 4, the deflection starting unit 4 is connected to the deflection protection unit 5, and the deflection protection unit 5 is connected to the tripping unit 6.

[0042] The oil pressure starting unit 1 includes a first judgment element, a first connecting wire, and an insulating oil pressure sensor. After receiving the signal from the strain starting unit, it measures the characteristic quantity of the insulating oil pressure through the insulating oil pressure sensor located on the top cover 8 of the on-load tap-changer. The insulating oil pressure sensor is connected to the first judgment element through the first connecting wire, and the first judgment element is connected to the strain starting unit 3. The first judgment element is used to compare the amplitude of the characteristic quantity of the insulating oil pressure with the oil pressure starting threshold value. If the amplitude of the characteristic quantity of the insulating oil pressure exceeds the oil pressure starting threshold value, it starts and sends a signal to the strain starting unit 3; otherwise, it waits to continue measuring the characteristic quantity of the insulating oil pressure and compares it with the oil pressure starting threshold value.

[0043] The oil pressure starting threshold value P set is set as:

[0044] P set = K1P max

[0045] where K1 is the oil pressure setting coefficient, taking 1.5, and P max is the maximum value of the internal oil pressure in the oil chamber of the on-load tap-changer under normal operation.

[0046] See Figure 2 , the explosion-proof unit 2 includes a sandwich gradient hierarchical honeycomb copper 7. The density of the sandwich gradient hierarchical honeycomb copper 7 is arranged in the order of increasing gradient, including a front panel 10 and two layers of honeycomb copper. The honeycomb copper is welded to the front panel 10 and is tightly connected to the top cover 8 of the on-load tap-changer, forming a sandwich structure as a whole. The two layers of honeycomb copper specifically include a first layer of honeycomb copper 12 and a second layer of honeycomb copper 13. The density of the first layer of honeycomb copper 12 is 0.60 g / cm 3 , and the density of the second layer of honeycomb copper 13 is 0.30 g / cm 3 . The second layer of honeycomb copper 13 with a smaller density is welded to the front panel 10, and the first layer of honeycomb copper 12 with a larger density is welded to the top cover 8 of the on-load tap-changer.

[0047] Through the gradient hierarchical honeycomb copper 7 in the explosion-proof unit 2, energy can be absorbed, the insulating oil pressure can be reduced, the impact on the on-load tap-changer can be alleviated, the overall pressure-bearing limit of the on-load tap-changer can be improved, and the on-load tap-changer can be prevented from bursting and exploding.

[0048] The strain activation unit 3 includes a strain sensor 11, a second judging element, and a second connecting wire. The strain sensor 11 is connected to the second judging element through the second connecting wire, and the second judging element is connected to the first judging element and the deflection activation unit 4. The strain sensor 11 is arranged between the first-layer honeycomb copper 12 and the second-layer honeycomb copper 13, and the strain characteristic quantity of the honeycomb copper is measured in real time through the strain sensor 11, and the amplitude of the strain characteristic quantity is compared with the strain activation threshold value. If the amplitude of the strain characteristic quantity exceeds the strain activation threshold value, a signal is activated and sent to the deflection activation unit 4; otherwise, it continues to wait for the oil pressure activation signal and continues to measure the strain.

[0049] Strain activation threshold value ε set Is set to:

[0050] ε set = K2ε max

[0051] Wherein, K2 is the strain setting coefficient, taking 1.3, and ε set Is the maximum value of the strain of the layered honeycomb copper under the normal operation of the on-load tap-changer.

[0052] The deflection activation unit 4 includes a third judging element, a third connecting wire, and a laser displacement sensor. The sampling frequency of the laser displacement sensor is 10 kHz. The laser displacement sensor is connected to the third judging element through the third connecting wire, and the third judging element is connected to the second judging element and the deflection protection unit 5. The laser displacement sensor measures the deflection change of the top cover 8 of the on-load tap-changer by the triangulation method. By emitting laser light to irradiate the surface of the top cover 8 of the on-load tap-changer, as the deflection of the top cover surface changes, the laser light path changes, and through measuring the reflection light angle and calculation, the real-time measurement of the deflection characteristic quantity of the top cover 8 of the on-load tap-changer is realized. After receiving the signal of the strain activation unit 3, the deflection characteristic quantity of the surface of the top cover 8 of the on-load tap-changer is measured, and the amplitude of the deflection characteristic quantity is compared with the deflection activation threshold value of the deflection activation unit. If the amplitude of the deflection characteristic quantity exceeds the deflection protection threshold value, it is considered that the deflection activation unit can be activated, and a signal is sent to the deflection protection unit 5; otherwise, it continues to wait for the signal of the strain activation unit and measures the deflection.

[0053] Deflection activation threshold value Y set Is set to:

[0054] Y set = K re Y max

[0055] Wherein, K re Is the deflection reliability coefficient, taking 1.5, and Y set Is the maximum value of the deflection of the top cover under the normal operation of the on-load tap-changer.

[0056] The deflection protection unit 5 includes a fourth judging element, which is connected to the third judging element and the tripping unit 6. After receiving the signal sent by the deflection starting unit 4, the fourth judging element judges whether the transformer deflection protection reaches the action condition by comparing the amplitude of the full deflection with the deflection protection action threshold value. If the amplitude of the full deflection exceeds the deflection protection action threshold value, it is considered that the tripping condition of the deflection protection is reached, and a signal is sent to the tripping unit 6 through the fourth judging element; otherwise, it continues to wait for the deflection starting signal and judge the full deflection.

[0057] The on-load tap-changer protection device based on the deflection information is characterized by the average value of the deflections of multiple measuring points on the oil tank within a period of time. Under the normal operation, external short circuit or inrush current state of the transformer, using a sliding window, an unbalanced quantity Y with a non-zero full deflection will be obtained after the periodic superposition and cancellation of the deflections of multiple measuring points. k 。

[0058] To ensure that the deflection protection unit does not send a tripping signal when the most serious short circuit fault occurs externally, the deflection protection action threshold value Y st is set as:

[0059] Y st =K r Y k.max

[0060] wherein, K r is a reliability coefficient, generally taken as 1.2, and Y k.max is the unbalanced quantity of the tank body deflection under the most serious external short circuit fault of the transformer.

[0061] After receiving the signal sent by the fourth judging unit element, the tripping unit 6 issues a tripping signal and stores the data of the transient oil pressure of the transformer, the transient strain of the explosion-proof unit, and the deflection of the tap-changer top cover. The whole set of devices is reset.

[0062] See Figure 3 , the on-load tap-changer protection method based on the comprehensive characteristic quantity includes the following steps:

[0063] Step 1: After the device is powered on and started, read the preset oil pressure starting threshold value P set , the explosion-proof unit strain starting threshold value ε set and the deflection starting threshold value Y set , the deflection protection threshold value Y st ;

[0064] Step 2: Measure the internal insulating oil pressure of the on-load tap-changer through the insulating oil pressure sensor to obtain the real-time oil pressure characteristic quantity P(t);

[0065] Step 3: Compare whether the amplitude of the real-time oil pressure characteristic quantity exceeds the oil pressure starting threshold value P through the first judging elementset , determine whether the oil pressure starting unit is started. If the amplitude of the real-time oil pressure characteristic quantity exceeds the oil pressure starting threshold value P set , then the oil pressure starting unit is started and proceeds to step 4; otherwise, the oil pressure starting unit is not started and returns to step 2;

[0066] Step 4: Measure the real-time strain characteristics of the layered honeycomb copper 7 through the strain sensor 11 located inside the explosion-proof unit 2, quickly sense the real-time change of the honeycomb copper strain, obtain the real-time strain characteristic quantity ε(t), and adapt to the internal oil stain and strong electromagnetic environment of the on-load tap-changer;

[0067] Step 5: Determine whether the strain starting unit is started by the strain starting unit 3 to check if the amplitude of the real-time strain characteristic quantity exceeds the strain starting threshold value ε set , determine whether the strain starting unit is started. If the amplitude of the real-time strain characteristic quantity exceeds the strain starting threshold value ε set , then the strain starting unit is started and proceeds to step 6; otherwise, the strain starting unit is not started and returns to step 2;

[0068] Step 6: Measure the deflection change on the outside of the on-load tap-changer top cover in real time through the laser displacement sensor, and obtain N deflection characteristic quantities Y ms,1 (t), Y ms,2 (t),..., Y ms,N (t);

[0069] Measuring the deflection of the tap-changer top cover through the laser displacement sensor to obtain the deflection characteristic quantity of the top cover is beneficial for analyzing and judging the state of the on-load tap-changer top cover.

[0070] Step 7: Compare the peak values of the N deflection characteristic quantities of the real-time top cover with the starting threshold value of the deflection starting unit through the deflection starting unit 4, and calculate the real-time total deflection Y op (t), and compare the real-time deflection characteristic quantity Y ms,i (t) of each deflection measurement point with the starting threshold value Y set of the starting unit through the third judgment element to determine whether the starting unit is started. If the peak value of the deflection characteristic quantity of any deflection measurement point exceeds the starting threshold value of the deflection starting unit, the protection is started and proceeds to step 8; otherwise, the protection is not started and returns to step 2;

[0071] The real-time total deflection Y op (t) is calculated by the following formula:

[0072]

[0073] where T is the data window length, i = 1, 2,..., N is the deflection measurement point number, and Y ms,i (t) is the instantaneous deflection measured at the i-th measurement point at time t.

[0074] Step 8: Determine whether the real-time total deflection Y op (t) exceeds the deflection protection action threshold value Y st . If it exceeds, go to Step 9; otherwise, return to Step 2.

[0075] Step 9: The tripping unit 6 issues a deflection tripping signal, stores the transient oil pressure, the transient strain of the explosion-proof unit, and the deflection data of the tap changer top cover within 500 ms before and after the trip, and the entire device is reset.

[0076] See Figure 4 、 Figure 5 and Figure 6 , there are significant changes in the instantaneous oil pressure of the insulating oil, the measured deflection of the top cover, and the strain of the layered honeycomb copper under the internal fault of the on-load tap changer of the present invention. Based on the above characteristics, a protection device for the on-load tap changer containing porous materials is designed. At the same time, the porous metal material of the present invention effectively reduces the oil pressure, improves the pressure-bearing capacity of the on-load tap changer, reduces the deformation degree of the on-load tap changer, and enhances the explosion-proof performance of the on-load tap changer.

[0077] Through the organic combination and reasonable collocation of six parts, namely the explosion-proof unit, the oil pressure start unit, the strain start unit, the deflection start unit, the deflection protection unit, and the tripping unit, the whole method of the present invention is easy to implement and has high sensitivity.

[0078] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. On-load tap-changer protection device based on comprehensive characteristic quantity, characterized in that, It includes an oil pressure starting unit (1), a strain starting unit (3), a deflection starting unit (4), a deflection protection unit (5), a tripping unit (6), and an explosion-proof unit (2) capable of absorbing energy; The oil pressure starting unit (1) is connected to the strain starting unit (3), the explosion-proof unit (2) is connected to the strain starting unit (3), the strain starting unit (3) is connected to the deflection starting unit (4), the deflection starting unit (4) is connected to the deflection protection unit (5), and the deflection protection unit (5) is connected to the tripping unit (6); The oil pressure starting unit (1) includes a first judgment element, a first connecting wire, and an insulating oil pressure sensor. The insulating oil pressure sensor is connected to the first judgment element through the first connecting wire, and the first judgment element is connected to the strain starting unit (3); The strain starting unit (3) includes a strain sensor (11) and a second judgment element connected to each other, and the second judgment element is connected to the deflection starting unit (4); The explosion-proof unit (2) includes a layered honeycomb copper (7). The layered honeycomb copper (7) includes a front panel (10), a first-layer honeycomb copper (12), and a second-layer honeycomb copper (13). The second-layer honeycomb copper (13) is welded to the front panel (10), and the first-layer honeycomb copper (12) is welded to the on-load tap-changer top cover (8); The strain sensor (11) is arranged between the first-layer honeycomb copper (12) and the second-layer honeycomb copper (13); The deflection starting unit (4) includes a third judgment element, a third connecting wire, and a laser displacement sensor. The laser displacement sensor is connected to the third judgment element through the third connecting wire, and the third judgment element is connected to the deflection protection unit (5); The deflection protection unit (5) includes a fourth judgment element, a fourth connecting wire, and a deflection full amount calculation element. The deflection full amount calculation element is connected to the fourth judgment element through the fourth connecting wire, and the fourth judgment element is connected to the tripping unit (6).

2. The on-load tap-changer protection device based on the comprehensive characteristic quantity according to claim 1, wherein The density of the first layer of honeycomb copper (12) is 0.60 g / cm 3 , and the density of the second layer of honeycomb copper (13) is 0.30 g / cm 3 .

3. The on-load tap-changer protection device based on the comprehensive characteristic quantity according to claim 1, characterized in that, The sampling frequency of the laser displacement sensor is 10 kHz; The laser displacement sensor uses the triangulation method to measure the deflection change of the on-load tap-changer top cover (8).

4. The on-load tap-changer protection method based on the comprehensive feature quantity of the device according to claim 1, characterized in that, It includes the following steps: Step 1: Measure the insulating oil pressure inside the on-load tap-changer to obtain the real-time oil pressure characteristic quantity; Step 2: Judge whether the amplitude of the real-time oil pressure characteristic quantity exceeds the oil pressure starting threshold value through the oil pressure starting unit. If it exceeds the oil pressure starting threshold value, go to Step 3; otherwise, return to Step 1; Step 3: Measure the real-time strain characteristic of the layered honeycomb copper through the strain sensor to obtain the real-time strain characteristic quantity; Step 4: Judge whether the amplitude of the real-time strain characteristic quantity exceeds the strain starting threshold value. If it exceeds the strain starting threshold value, go to Step 5; otherwise, return to Step 1; Step 5: Measure the deflection change on the outside of the on-load tap-changer top cover in real time through the laser displacement sensor to obtain the real-time top cover deflection characteristic quantity; Step 6: Calculate the real-time deflection full amount according to the real-time top cover deflection characteristic quantity, and judge whether the amplitude of the real-time deflection full amount exceeds the starting threshold value of the deflection starting unit. If it exceeds the starting threshold value of the deflection starting unit, go to Step 7; otherwise, return to Step 1: Step 7: Determine whether the full amplitude of the real-time deflection exceeds the action threshold of the deflection protection unit. If it exceeds the action threshold of the deflection protection, proceed to Step 8; otherwise, return to Step 1. Step 8: The tripping unit issues a deflection tripping signal and stores the transient oil pressure, strain, and deflection data within 500 ms before and after the trip.

5. The on-load tap-changer protection method based on the comprehensive characteristic quantity according to claim 4, wherein, Real-time total deflection Y op (t) is calculated by the following formula: where T is the data window length, i = 1, 2,.. N, is the deflection measurement point number, and Y ms,i (t) is the instantaneous deflection measured at the i-th measurement point at time t.

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