Non-electric quantity protection method and device for on-load tap-changer

Abstract

The invention is suitable for the technical field of electric power engineering, and provides an on-load tap-changer non-electric quantity protection method and device, and the method comprises the steps: monitoring the pressure in an on-load tap-changer oil tank in real time, and when monitoring that the pressure value corresponding to each moment in a first time period is maintained in a preset pressure range, controlling the on-load tap-changer oil tank to be in a non-electric quantity protection state; when the duration of the first time period reaches a preset duration, obtaining a pressure value corresponding to each moment in the first time period; wherein the preset pressure range is larger than the pressure protection starting threshold value and smaller than or equal to the pressure protection action threshold value; based on the pressure values corresponding to all moments in the first time period, the linear regression slope of the pressure changing along with time is determined; and if the slope is greater than the preset slope, controlling the protection device to execute a protection action. According to the method, linear regression analysis is carried out on the data of the pressure changing along with time to judge whether the pressure of the oil tank has the rising trend or not, so that the fault state of the on-load tap-changer is determined, and the accuracy and reliability of protection can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electric power engineering, and in particular relates to a non-electrical quantity protection method and device for an on-load tap changer. Background Art

[0002] On-load tap-changer (OLTC) plays a vital role in the power system. It is responsible for regulating reactive power and stabilizing grid voltage, and is the core component of on-load tap-changer transformer. OLTC is divided into vacuum arc extinguishing type and insulating oil arc extinguishing type according to the arc extinguishing principle. Among them, the insulating oil arc extinguishing type is usually used for large-capacity transformers.

[0003] During the voltage regulation operation, OLTC needs to frequently switch the taps. This operation is completed in the oil chamber to achieve the current transfer and safely extinguish the arc in the insulating oil. Since the load fluctuation requires frequent voltage regulation, OLTC operates under high voltage and high current conditions, which is prone to poor contact and inadequate operation. When these faults occur, continuous heating or continuous arcing may occur, causing the insulating oil to vaporize and decompose, and the gas will expand and rise, pushing the insulating oil to flow toward the oil pillow. At the same time, the reduction in the quality of the insulating oil directly affects the normal operation of the on-load tap changer.

[0004] According to statistics, transformer failures caused by OLTC account for more than 20% of the total failures, of which mechanical failures are the main ones. For converter transformers in HVDC transmission systems, OLTC voltage regulation operations are more frequent and require higher operational reliability. At present, in order to protect the transformer OLTC, non-electrical protection facilities such as pressure relief valves, explosion-proof membranes, and gas protection are equipped. The setting values ​​of these pressure-sensitive protection facilities such as pressure relief valves and explosion-proof membranes are not uniform in domestic and foreign products. With the increase of transformer capacity, the normal switching of OLTC during heavy-load operation of the transformer will generate a large switching current, resulting in increased pressure fluctuations in the oil chamber, which puts the pressure relief valve at risk of malfunction. Although the gas relay currently used still follows the basic principles and mechanical structure of the Buchholz relay a hundred years ago, its protection setting is based on the experience summary of long-term operation. Over time, due to the shedding of oxides and the deterioration of insulating oil, a large amount of sludge may precipitate and adhere to mechanical parts such as baffles, floats or springs of gas protection, seriously affecting the accuracy and sensitivity of electrical operation. Such a mechanical heavy gas detection mechanism can only measure the single indicator of oil flow velocity, and cannot accurately identify the operating status, which may lead to wrong judgment of gas protection. Therefore, when a fault occurs during the operation of OLTC, it is necessary to seek a new non-electrical protection method to achieve rapid removal of the fault and improve the accuracy and reliability of protection. Summary of the invention

[0005] The embodiments of the present invention provide a method and a device for non-electrical quantity protection of an on-load tap changer, so as to accurately identify the operating state of the on-load tap changer and improve the accuracy and reliability of the non-electrical quantity protection of the on-load tap changer.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, an embodiment of the present invention provides a non-electrical quantity protection method for an on-load tap changer, comprising:

[0008] real-time monitoring of the pressure in the oil tank of the on-load tap changer, and when it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches a preset duration, obtaining the pressure values ​​corresponding to each moment in the first time period; wherein the preset pressure range is greater than a pressure protection start threshold value and less than or equal to a pressure protection action threshold value, the pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer;

[0009] Based on the pressure values ​​corresponding to each moment in the first time period, the slope of the linear regression of the pressure changing with time is determined; if the slope is greater than a preset slope, the protection device is controlled to perform a protection action.

[0010] In combination with the first aspect, in some embodiments, obtaining the pressure value corresponding to each moment in the first time period includes:

[0011] When the on-load tap changer starts to operate, clearing the stored pressure data;

[0012] When it is detected that the pressure value is greater than the pressure protection start threshold value, the current time is recorded as the start time;

[0013] If the pressure value corresponding to the start time is less than or equal to the pressure protection action threshold value, and the pressure values ​​corresponding to the multiple consecutive moments after the start time are all within the preset pressure range, then at each of the multiple consecutive moments, the pressure value corresponding to the moment is stored;

[0014] When it is detected that the difference between the cut-off time and the start time is greater than the preset duration, the pressure values ​​corresponding to each moment between the start time and the cut-off time are obtained, and the pressure values ​​at each moment in the first time period are obtained; wherein the cut-off time is the last moment among the multiple consecutive moments.

[0015] In combination with the first aspect, in some embodiments, the real-time monitoring of the pressure of the on-load tap changer oil tank, when it is monitored that the pressure value in the first time period remains within a preset pressure range and the duration of the first time period reaches a preset duration, obtaining the pressure value corresponding to each moment in the first time period includes:

[0016] When the on-load tap changer starts to operate, clearing the stored pressure data;

[0017] Acquire the value of the pressure in real time;

[0018] Determine whether the pressure value corresponding to the current moment is greater than the pressure protection start threshold value; if so, record the current moment as the initial time;

[0019] Continue to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value; if not, store the pressure value corresponding to the current moment, and obtain the pressure value corresponding to the next moment of the current moment, the next moment of the current moment being the new current moment;

[0020] Determine whether the duration from the initial time to the new current time reaches the preset duration;

[0021] If the duration from the initial time to the new current time reaches the preset duration, all the pressure values ​​that have been stored are obtained;

[0022] If the duration from the initial time to the new current moment does not reach the preset duration, then determine whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value; if the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value, then jump to the step of continuing to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value;

[0023] Among them, the values ​​of all the pressures that have been stored are the values ​​of the pressures corresponding to each moment in the first time period.

[0024] In combination with the first aspect, in some embodiments, the method further includes:

[0025] If the slope is less than or equal to the preset slope, the stored data of the pressure is cleared, and the new current time when the preset duration is reached is recorded as the new initial time;

[0026] Jump to the step of determining whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value;

[0027] If the pressure value corresponding to the new current moment is less than or equal to the pressure protection start threshold value, jump to the step of obtaining the pressure value in real time.

[0028] In combination with the first aspect, in some embodiments, the method further includes:

[0029] When it is detected that the pressure value is greater than the pressure protection start threshold value, the protection device is started;

[0030] When it is detected that the pressure value is greater than the pressure protection action threshold value, the protection device is controlled to perform a protection action.

[0031] In combination with the first aspect, in some embodiments, the calculation formula of the pressure protection start threshold value is:

[0032] p st =K rel p nor.max

[0033] Among them, p st K is the pressure protection start threshold value; rel is the reliability coefficient; p nor.max is the maximum value of the pressure during normal operation of the on-load tap changer in a non-switching state.

[0034] In combination with the first aspect, in some embodiments, the calculation formula of the pressure protection action threshold value is:

[0035] p th =K rel p max

[0036] Among them, p th K is the pressure protection action threshold value; rel is the reliability coefficient; p max It is the maximum value of the pressure when the on-load tap changer is in a switching state during maximum load operation or when an external fault occurs.

[0037] In combination with the first aspect, in some embodiments, the calculation formula of the slope of the linear regression is:

[0038]

[0039] Wherein, m is the slope; p(t) represents the value of the pressure at time t, and n represents the number of moments in the first period; is the average value of the time in the first period; is the average value of the pressure during the first time period.

[0040] In combination with the first aspect, in some embodiments, the calculation formula of the preset slope is:

[0041] M=K rel m max

[0042] Wherein, M is the preset slope; K rel is the reliability coefficient; m max is the maximum value of the slope of the linear regression determined based on the pressure data within the preset time period when the on-load tap changer is switched normally or subjected to an external disturbance.

[0043] In a second aspect, an embodiment of the present invention provides a non-electrical protection device for an on-load tap changer, comprising:

[0044] A monitoring and acquisition module, used for real-time monitoring of the pressure in the oil tank of the on-load tap changer, and when it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches a preset duration, the pressure values ​​corresponding to each moment in the first time period are acquired; wherein the preset pressure range is greater than a pressure protection start threshold value and less than or equal to a pressure protection action threshold value, the pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer;

[0045] The judgment and protection module is used to determine the slope of the linear regression of the pressure changing with time based on the value of the pressure corresponding to each moment in the first time period; if the slope is greater than a preset slope, control the protection device to perform a protection action.

[0046] The embodiment of the present invention provides a non-electrical protection method and device for an on-load tap changer, which monitors the pressure in the oil tank of the on-load tap changer in real time. When it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches the preset duration, the pressure values ​​corresponding to each moment in the first time period are obtained; here, the preset pressure range is greater than the pressure protection start threshold value and less than or equal to the pressure protection action threshold value; based on the pressure values ​​corresponding to each moment in the first time period, the slope of the linear regression of the pressure change over time is determined; if the slope is greater than the preset slope, the protection device is controlled to perform a protection action. In this way, by performing a linear regression analysis on the data of the pressure change over time, it is determined whether the oil tank pressure has an upward trend, thereby determining the fault state of the on-load tap changer, which can improve the accuracy and reliability of the protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0048] Figure 1 is a pressure characteristic curve corresponding to the on-load tap changer provided by an embodiment of the present invention during normal switching;

[0049] Figure 2 is a pressure characteristic curve corresponding to the on-load tap changer provided by an embodiment of the present invention when an external short circuit fault occurs in the transformer;

[0050] Figure 3 is a pressure characteristic curve corresponding to the on-load tap changer provided by an embodiment of the present invention when a short circuit fault occurs;

[0051] Figure 4 It is a flow chart of a non-electrical quantity protection method for an on-load tap changer provided by an embodiment of the present invention;

[0052] Figure 5 is a schematic diagram of a process for monitoring and obtaining pressure data provided by an embodiment of the present invention;

[0053] Figure 6 is a program flow chart of a non-electrical quantity protection method for an on-load tap changer provided by an embodiment of the present invention;

[0054] Figure 7 is a schematic diagram of installing a pressure sensor provided by an embodiment of the present invention;

[0055] Figure 8 is a linear regression fitting curve of the pressure variation over time of the on-load tap changer in a normal switching state provided by an embodiment of the present invention;

[0056] Fig. 9 is a linear regression fitting curve of the pressure change over time of the on-load tap changer provided by one embodiment of the present invention when the oil tank is subjected to external impact;

[0057] Fig.10 is a linear regression fitting curve of the pressure variation over time of the on-load tap changer provided by one embodiment of the present invention when a short circuit fault occurs on the inner wall of the oil tank;

[0058] Fig.11 It is a structural schematic diagram of a non-electrical quantity protection device for an on-load tap changer provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0060] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0061] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]", depending on the context.

[0062] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0063] References to "one embodiment" or "some embodiments" etc. described in the present specification mean that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0064] The OLTC of the on-load tap-changing transformer not only stabilizes the voltage at the load center, but also connects to the power grid, adjusts the load flow direction and improves the reactive power distribution, which is crucial to the stable operation of the system. However, OLTC needs to switch frequently and quickly under high voltage and high current environments, and is prone to failure, which directly threatens the normal operation of the power transformer.

[0065] Based on the above problems, the inventors of the present invention proposed a new OLTC protection method through research. During the research process, the inventors found that:

[0066] 1. When the OLTC switches or a fault occurs and an arc occurs, the arc action will cause the insulating oil to decompose and generate gas. The high-temperature and high-pressure gas will increase the pressure in the oil tank. During normal switching, each arc burning time does not exceed 10 milliseconds, the arc energy is small, and the gas generated is limited. Therefore, the pressure in the oil tank rises less and lasts for a short time, and the pressure will soon return to normal levels. The corresponding pressure characteristic curve for normal switching of OLTC is as follows: Figure 1 shown.

[0067] 2. The oscillation caused by the external short circuit fault of the transformer will also affect the pressure level in the oil tank. This fault will cause the winding to deform and displace, causing vibration centered on the winding. The insulating oil and solid components act as media to propagate pressure waves, which will cause the pressure level in the oil tank to oscillate violently. This pressure wave has a high vibration frequency and there is no pressure increase trend in a short period of time. The corresponding pressure characteristic curve when the transformer is short-circuited is as follows: Figure 2 shown.

[0068] 3. When an internal short circuit occurs in OLTC, a large arc current that is difficult to extinguish by itself will be generated. The continuous strong arc action will decompose the insulating oil to produce gas, causing the pressure in the oil tank to increase. If a serious fault occurs, the strong arc will instantly decompose the insulating oil, produce a large amount of gas, and the oil pressure will rise sharply to a higher level, higher than the safe state. If the fault is minor, a persistent weak arc will be generated. The continuous action of the weak arc will also cause the oil pressure to rise slowly and eventually exceed the safe level. The corresponding pressure characteristic curve when an OLTC short circuit occurs is as follows: Figure 3 shown.

[0069] It should be understood that the above-mentioned pressure in the oil tank refers to the pressure of the gas inside the oil tank on the container wall. Figures 1 to 3 The inventor compared the pressure characteristics in the above three cases and found that the pressure of the oil tank has a trend of continuous increase only when the internal short circuit fault just occurs. Therefore, the inventor proposed a fault state identification method based on judging the rising trend of the oil tank pressure, that is, the non-electrical quantity protection method of the on-load tap changer provided by the embodiment of the present invention.

[0070] The on-load tap changer non-electrical quantity protection method and device provided by the embodiment of the present invention monitors the pressure in the on-load tap changer oil tank in real time, obtains the pressure data of the oil tank in a targeted manner, performs linear regression analysis on the obtained pressure data, determines the slope of the linear regression of the pressure change over time, and judges whether the OLTC has an internal short circuit fault by the slope; if the slope is greater than the preset slope, it is determined that an internal short circuit fault has occurred, and the control protection device performs a protection action at this time. Among them, the pressure data obtained is the value of the pressure at each moment in the certain time when the pressure value is maintained between the pressure protection start threshold value and the pressure protection action threshold value for a certain time. The pressure protection start threshold value is the threshold value used to judge whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is the threshold value used to judge whether a serious fault occurs in the on-load tap changer. Therefore, the present invention determines whether the rising trend of the pressure meets the pressure characteristics of the internal short circuit fault by analyzing the data of the pressure change over time when the oil tank pressure exceeds the normal level but no serious fault occurs, so as to cut off the fault in time for protection.

[0071] The on-load tap changer non-electrical quantity protection method and device provided in the embodiment of the present invention can be applied to an oil-immersed transformer to improve the protection effect of the on-load tap changer of the oil-immersed transformer during the voltage regulation process.

[0072] Figure 4 is a flow chart of a non-electrical quantity protection method for an on-load tap changer provided by an embodiment of the present invention, referring to Figure 4 The non-electrical quantity protection method of the on-load tap changer is described as follows:

[0073] S101, monitor the pressure in the on-load tap changer oil tank in real time, and when it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches a preset duration, obtain the pressure values ​​corresponding to each moment in the first time period.

[0074] Among them, the preset pressure range is greater than the pressure protection start threshold value and less than or equal to the pressure protection action threshold value. The pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer.

[0075] In the embodiment of the present invention, after obtaining the pressure data in the first period of the preset time, the amount of the pressure data reaches a sufficient amount of data for analyzing the internal short circuit fault. The preset time is a time constant and can be determined according to the change time of the pressure characteristics in the above three cases.

[0076] In some embodiments, the calculation formula of the pressure protection start threshold value can be:

[0077] p st =K rel p nor.max

[0078] Among them, p st K is the pressure protection start threshold value; rel is the reliability coefficient; p nor.max It is the maximum pressure during normal operation of the on-load tap-changer in the non-switching state.

[0079] The calculation formula of the pressure protection action threshold value can be:

[0080] p th =K rel p max

[0081] Among them, p th K is the pressure protection action threshold value; rel is the reliability coefficient; p max It is the maximum pressure when the on-load tapchanger is in the switching state during maximum load operation or when an external fault occurs.

[0082] In some embodiments, the process of obtaining the pressure values ​​corresponding to each moment in the first time period in the above step S101 may include:

[0083] S201, when the on-load tap changer starts to operate, the stored pressure data is cleared.

[0084] S202: When the pressure value detected is greater than the pressure protection start threshold value, the current time is recorded as the start time.

[0085] S203, if the pressure value corresponding to the start time is less than or equal to the pressure protection action threshold value, and the pressure values ​​corresponding to multiple consecutive moments after the start time are all within the preset pressure range, then at each of the multiple consecutive moments, the pressure value corresponding to the moment is stored.

[0086] S204, when it is detected that the difference between the deadline and the start time is greater than the preset duration, the pressure values ​​corresponding to each moment between the start time and the deadline are obtained, and the pressure values ​​at each moment in the first time period are obtained; wherein the deadline is the last moment among multiple consecutive moments.

[0087] In the above embodiment, if the duration between the end time and the start time is less than or equal to the preset duration, the currently stored pressure data is cleared and the pressure data that meets the conditions is stored again. This situation indicates that the pressure value quickly falls back to the normal level and does not meet the pressure characteristics of the internal short circuit fault, and further detection and analysis are required.

[0088] It can be understood that in the above steps S201 to S204, when acquiring pressure data, not all the detected pressure data are directly saved, but are saved in a targeted manner, so that the storage unit (or module) used to store pressure data only stores pressure data worth analyzing (data exceeding the normal level but not exceeding the critical fault threshold), saving storage space. Moreover, in each linear regression analysis, it is only necessary to directly obtain all the pressure data in the storage unit without complicated pre-processing operations such as data screening, thereby improving the speed of fault analysis.

[0089] In some embodiments, the above step S101 can be implemented by a computer program, see Figure 5 The process of the computer program includes the following steps S301 to S307:

[0090] S301, when the on-load tap changer starts to operate, the stored pressure data is cleared.

[0091] S302, obtaining the pressure value p(t) in real time.

[0092] S303: Determine whether the pressure value p(t) corresponding to the current moment is greater than the pressure protection start threshold value p st ; If so, the current time is recorded as the initial time t0, that is, t0 = t.

[0093] S304: Continue to determine whether the pressure value p(t) corresponding to the current moment is greater than the pressure protection action threshold value p th ; If not, store the pressure value p(t) corresponding to the current moment, and obtain the pressure value p(t+1) corresponding to the next moment t+1 of the current moment, the next moment t+1 of the current moment is the new current moment t, that is, t=t+1;

[0094] S305, determine whether the duration between the initial time t0 and the new current moment t reaches the preset duration T; if the duration t-t0 between the initial time t0 and the new current moment t reaches the preset duration T, execute step S306; if the duration t-t0 between the initial time t0 and the new current moment t does not reach the preset duration T, execute step S307.

[0095] S306, obtaining all the stored pressure values; wherein all the stored pressure values ​​are the pressure values ​​corresponding to each moment in the first time period t0-t.

[0096] S307, determine whether the pressure value p(t) corresponding to the new current moment t is greater than the pressure protection start threshold value; if the pressure value p(t) corresponding to the new current moment t is greater than the pressure protection start threshold value p st, then jump to step S304; otherwise, jump to step S302.

[0097] In the above embodiment, when executing step S306, after obtaining the pressure data to be analyzed (the values ​​of all pressures that have been stored), the process proceeds to step S102 to analyze and judge the pressure data.

[0098] S102, based on the pressure values ​​corresponding to each moment in the first time period, determine the slope of the linear regression of the pressure change over time; if the slope is greater than a preset slope, control the protection device to perform a protection action.

[0099] It can be understood that the preset slope can be determined according to the slopes of the pressure linear regression fitting curves corresponding to the normal switching of the OLTC and the oscillation caused by the external short circuit fault of the transformer. For example, the maximum slope obtained in these two cases is used as the preset slope. Alternatively, the preset slope can be determined based on this, combined with the minimum slope of the pressure linear regression fitting curve corresponding to the internal short circuit fault of the OLTC.

[0100] In some embodiments, the calculation formula of the slope of linear regression can be:

[0101]

[0102] Wherein, m is the slope; p(t) represents the value of pressure at time t, and n represents the number of moments in the first period; is the average value of time in the first period; is the average pressure in the first period.

[0103] In a possible implementation, the calculation formula of the preset slope may be:

[0104] M=K rel m max

[0105] Where, M is the preset slope; K rel is the reliability coefficient; m max It is the maximum value of the slope of the linear regression determined based on the pressure data within a preset time when the on-load tapchanger is switching normally or subjected to external disturbance.

[0106] In the above embodiment, when it is detected that the slope of the pressure linear regression is greater than the preset slope, it can be determined that the pressure rises steadily over time, and its rising trend conforms to the pressure characteristics when an internal short circuit fault occurs, so that it can be determined that an internal short circuit fault has occurred in the on-load tap changer, and the protection action is performed in time to cut off the fault. Since this method can accurately identify the short circuit fault, the method of the present invention can distinguish the short circuit fault from other states, thereby avoiding false operation and significantly improving the reliability of the protection.

[0107] In addition to the above-mentioned internal short circuit fault, in actual application, when the system is switched normally or subjected to other small disturbances, the pressure of the oil tank may also rise within a certain period of time. At this time, the calculated slope will be less than or equal to the preset slope. Therefore, based on the above embodiment, the on-load tap changer non-electrical protection method in the embodiment of the present invention may also include:

[0108] S103, if the slope is less than or equal to the preset slope, clear the stored pressure data, and record the new current time when the preset time length T is reached as the new initial time t0, and then jump to the above step S307.

[0109] Wherein, step S307 may further include: if the value of the pressure corresponding to the new current moment is less than or equal to the pressure protection start threshold value, then jump to step S302.

[0110] On the basis of the above embodiments, the on-load tap changer non-electrical quantity protection method provided by the embodiments of the present invention may further include:

[0111] S104: When the pressure value p(t) detected is greater than the pressure protection start threshold value p st When the protection device is activated.

[0112] S105: When the detected pressure value p(t) is greater than the pressure protection action threshold value p th When the protection device is controlled, it will execute the protection action.

[0113] In the above embodiment, by setting the pressure protection action threshold value p th It can ensure that when a serious fault occurs, the protection action is directly responded to according to the excessive tank pressure to prevent the fault from causing more serious consequences, thus making up for the shortcoming of the linear regression method in terms of speed in terms of slow response time.

[0114] Next, we provide a program example and combine it with Figure 6 The program flow chart shown in the figure introduces various situations that may occur during the pressure monitoring process involved in the above embodiment:

[0115] Step 1: When the transformer on-load tap changer is in operation, the recorded data of the oil tank pressure is initialized and the original stored data is cleared.

[0116] Step 2: monitor the pressure in the oil tank of the on-load tap changer in real time, which is recorded as the instantaneous value of the oil pressure p(t). At this time, there is no need to store the pressure data.

[0117] Step 3: Compare the instantaneous pressure value p(t) with the pressure protection start threshold value p st ;

[0118] If p(t)>p st , record the current time t as t0, start the protection device, and go to step 4;

[0119] If p(t)≤p st , indicating that the pressure is at a normal level, return to step 2.

[0120] Step 4: Compare the instantaneous pressure value p(t) with the pressure protection action threshold value p th ;

[0121] If p(t)>p th , indicating that the pressure in the fuel tank is too high, it is judged that a serious fault has occurred, and the control protection device performs a protection action;

[0122] If p st <p(t)≤p th , go to step 5.

[0123] Step 5, continue to obtain the instantaneous value p(t) of the pressure in the fuel tank at the next moment, and store the instantaneous value p(t) of the pressure and the corresponding moment t.

[0124] Step 6, compare the value of t-t0 with the preset time length T; when t-t0>T, it indicates that there are enough recorded pressure data samples to perform linear regression calculation, and go to step 7; otherwise, go to step 8.

[0125] Step 7, based on the recorded data, calculate the slope parameter m of the linear regression of the pressure change over time; if m is greater than the preset slope M, it indicates that the pressure rises steadily over time, and it is judged that a fault has occurred, and the protection device is controlled to perform a protection action; otherwise, it is judged that the system has switched normally, or other small disturbances have caused the pressure to rise, and this time t is updated to t0, the currently stored pressure statistics are cleared and step 8 is entered.

[0126] Step 8: Compare the instantaneous pressure value p(t) with the protection start threshold value p st ;

[0127] If p(t)>p st , indicating that the pressure has not returned to normal levels, and further pressure data needs to be recorded, and then proceed to step 4;

[0128] If p(t)≤p st , indicating that the pressure is at a normal level, clear the previously recorded pressure data and return to step 2.

[0129] Through the above process, we can accurately obtain data when the tank pressure is abnormal. This way of recording data is itself a preliminary prediction of the internal short-circuit fault. Then, by performing linear regression analysis on these data, we can calculate the slope of the linear regression, and further accurately determine the internal short-circuit fault based on the slope, so as to effectively distinguish the short-circuit fault from other normal operating conditions, avoid false operation, and significantly improve the reliability of protection. In addition, by setting the pressure protection action threshold value p th It can ensure that in the event of a serious fault, the protection action is directly responded to according to the excessive oil pressure to prevent the fault from causing more serious consequences. In terms of speed, it makes up for the shortcoming of the linear regression method in terms of slow response time.

[0130] With respect to the on-load tap changer non-electrical quantity protection method provided in the embodiment of the present invention, the inventor also provides a specific embodiment to verify the feasibility of the present solution. In this specific embodiment, a CMDⅢ on-load tap changer 710 is used. The installation position of the pressure sensor in this embodiment is as follows: Figure 7 See Figure 7 The on-load tap changer 710 is connected to the oil conservator 730 through the pipeline 720, the pressure sensor 740 is arranged at the connection between the on-load tap changer 710 and the pipeline 720, and the gas relay 750 is arranged on the outer wall of the pipeline 720. The pressure sensor 740 can be used to monitor the pressure of the oil tank of the on-load tap changer 710 in real time, and the gas relay 750 is a device for protecting the on-load tap changer 710.

[0131] In the process of monitoring the oil tank pressure of the above-mentioned on-load tap changer 710, the inventor collected and analyzed the pressure data under three conditions: normal switching of the switch, external impact on the oil tank (external short-circuit fault of the transformer), and short-circuit fault on the inner wall of the oil tank, and performed linear regression analysis respectively, and verified the above-mentioned method by comparing the slopes.

[0132] Figure 8 is a linear regression fitting curve of the pressure variation over time of the on-load tap changer 710 in a normal switching state. Figure 8 is based on Figure 1 The pressure data is fitted. Figure 1After the normal switch occurs at t=500ms, the oil pressure rises from the normal state to the maximum value in less than 100ms, and falls back to below the average value in 500ms. About 4s later, the oil pressure fluctuation rises back to the normal pressure value and maintains this level. In this process, the pressure data with the fastest pressure rise within 520-560ms (time in ms, pressure in kPa, the same below) are subjected to linear regression processing, and the calculated slope m1=0.0603, and the corresponding linear regression fitting curve is shown in Figure 8 .

[0133] Fig. 9 is a linear regression fitting curve of the pressure variation over time of the on-load tap changer 710 when the oil tank is subjected to external impact. Fig. 9 is based on Figure 2 The pressure data is fitted. Figure 2 When an external fault occurs, t = 0 is impacted by an external pressure wave and is in a state of equal amplitude oscillation in a short period of time, with a maximum amplitude of 10kPa and a high pressure vibration frequency. In this case, the pressure data within 0 to 40ms is processed by linear regression, and the calculated slope is m2 = -0.0569. The corresponding linear regression fitting curve is shown in Fig. 9 .

[0134] Fig.10 It is a linear regression fitting curve of the pressure change over time of the on-load tap changer 710 when a short circuit fault occurs on the inner wall of the oil tank. Fig.10 is based on Figure 3 The pressure data were fitted. Figure 3 The figure shows the corresponding pressure characteristic curves when short circuit faults occur at four positions 1, 2, 3, and 4 on the inner wall of the oil tank. It can be seen that after the short circuit faults occur at these four positions, the oil tank pressure rises to a peak value within 20ms, and then is in a fluctuating stable state. Among them, the peak values ​​of curves 1, 2, and 3 are close, about 200kPa; the peak value of curve 4 is significantly lower, about 90kPa. Obviously, the rising trend of curve 4 is the slowest and the slope is lower. A linear regression calculation is performed on the pressure data of curve 4 within 0-40ms, and the calculated slope is m3=1.5465. The corresponding linear regression fitting curve is shown in Fig.10 .

[0135] Comparing the sizes of m1, m2, and m3, it can be seen that when a short circuit occurs in the oil tank, the slope of the pressure rise trend is the slowest, which is still significantly greater than the slope under normal switching and external impact. Therefore, the on-load tap changer non-electrical quantity protection method provided by the embodiment of the present invention can effectively distinguish short circuit faults from normal switching and external faults, accurately judge faults and perform protection in time to avoid false operation.

[0136] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0137] Corresponding to the on-load tap changer non-electrical quantity protection method described in the above embodiment, Figure 8 A schematic structural diagram of a non-electrical quantity protection device for an on-load tap changer provided in an embodiment of the present invention is shown. For ease of description, only the parts related to the embodiment of the present invention are shown.

[0138] See also Fig.11 The on-load tap changer non-electrical quantity protection device 1100 in the embodiment of the present invention may include a monitoring and obtaining module 1110 and a judging and protecting module 1120 .

[0139] Among them, the monitoring and acquisition module 1110 can be used to monitor the pressure in the on-load tap changer oil tank in real time. When it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within the preset pressure range and the duration of the first time period reaches the preset duration, the pressure values ​​corresponding to each moment in the first time period are obtained; wherein the preset pressure range is greater than the pressure protection start threshold value and less than or equal to the pressure protection action threshold value, the pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer.

[0140] The judgment and protection module 1120 can be used to determine the slope of the linear regression of the pressure change over time based on the pressure values ​​corresponding to each moment in the first time period; if the slope is greater than the preset slope, the protection device is controlled to perform a protection action.

[0141] Optionally, the monitoring and acquisition module 1110 may be specifically used for:

[0142] When the on-load tap-changer starts to operate, the stored pressure data is cleared;

[0143] When the detected pressure value is greater than the pressure protection start threshold, the current time is recorded as the start time;

[0144] If the pressure value corresponding to the start time is less than or equal to the pressure protection action threshold value, and the pressure values ​​corresponding to the multiple consecutive moments after the start time are all within the preset pressure range, then at each of the multiple consecutive moments, the pressure value corresponding to the moment is stored;

[0145] When it is detected that the difference between the deadline and the start time is greater than the preset duration, the pressure values ​​corresponding to each moment between the start time and the deadline are obtained, and the pressure values ​​at each moment in the first time period are obtained; wherein the deadline is the last moment among multiple consecutive moments.

[0146] Optionally, the monitoring and acquisition module 1110 may be specifically used for:

[0147] When the on-load tap-changer starts to operate, the stored pressure data is cleared;

[0148] Get the pressure value in real time;

[0149] Determine whether the pressure value corresponding to the current moment is greater than the pressure protection start threshold value; if so, record the current moment as the initial time;

[0150] Continue to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value; if not, store the pressure value corresponding to the current moment, and obtain the pressure value corresponding to the next moment of the current moment, the next moment of the current moment is the new current moment;

[0151] Determine whether the duration from the initial time to the new current time reaches the preset duration;

[0152] If the duration from the initial time to the new current time reaches the preset duration, all the pressure values ​​that have been stored are obtained;

[0153] If the duration from the initial time to the new current moment does not reach the preset duration, then determine whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value; if the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value, then jump to the step of continuing to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value;

[0154] Among them, all the stored pressure values ​​are the pressure values ​​corresponding to each moment in the first time period.

[0155] Optionally, the on-load tap changer non-electrical protection device 1100 can also be used for:

[0156] If the slope is less than or equal to the preset slope, the stored pressure data is cleared, and the new current moment when the preset duration is reached is recorded as the new initial time; jump to the step of determining whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value; if the pressure value corresponding to the new current moment is less than or equal to the pressure protection start threshold value, jump to the step of obtaining the pressure value in real time.

[0157] Optionally, the on-load tap changer non-electrical protection device 1100 can also be used for:

[0158] When the detected pressure value is greater than the pressure protection start threshold value, the protection device is started;

[0159] When the detected pressure value is greater than the pressure protection action threshold value, the protection device is controlled to perform a protection action.

[0160] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0161] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0162] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the above-mentioned embodiments of the non-electrical quantity protection method of the on-load tap changer. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium.

[0163] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A non-electrical quantity protection method for an on-load tap changer, characterized in that: include: real-time monitoring of the pressure in the oil tank of the on-load tap changer, and when it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches a preset duration, obtaining the pressure values ​​corresponding to each moment in the first time period; wherein the preset pressure range is greater than a pressure protection start threshold value and less than or equal to a pressure protection action threshold value, the pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer; Based on the pressure values ​​corresponding to each moment in the first time period, the slope of the linear regression of the pressure changing with time is determined; if the slope is greater than a preset slope, the protection device is controlled to perform a protection action.

2. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The obtaining the pressure value corresponding to each moment in the first time period includes: When the on-load tap changer starts to operate, clearing the stored pressure data; When it is detected that the pressure value is greater than the pressure protection start threshold value, the current time is recorded as the start time; If the pressure value corresponding to the start time is less than or equal to the pressure protection action threshold value, and the pressure values ​​corresponding to the multiple consecutive moments after the start time are all within the preset pressure range, then at each of the multiple consecutive moments, the pressure value corresponding to the moment is stored; When it is detected that the difference between the cut-off time and the start time is greater than the preset duration, the pressure values ​​corresponding to each moment between the start time and the cut-off time are obtained, and the pressure values ​​at each moment in the first time period are obtained; wherein the cut-off time is the last moment among the multiple consecutive moments.

3. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The real-time monitoring of the pressure of the on-load tap changer oil tank, when monitoring that the pressure value in the first time period remains within a preset pressure range and the duration of the first time period reaches a preset duration, obtaining the pressure value corresponding to each moment in the first time period, includes: When the on-load tap changer starts to operate, clearing the stored pressure data; Acquire the value of the pressure in real time; Determine whether the pressure value corresponding to the current moment is greater than the pressure protection start threshold value; if so, record the current moment as the initial time; Continue to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value; if not, store the pressure value corresponding to the current moment, and obtain the pressure value corresponding to the next moment of the current moment, the next moment of the current moment being the new current moment; Determine whether the duration from the initial time to the new current time reaches the preset duration; If the duration from the initial time to the new current time reaches the preset duration, all the pressure values ​​that have been stored are obtained; If the duration from the initial time to the new current moment does not reach the preset duration, then determine whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value; if the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value, then jump to the step of continuing to determine whether the pressure value corresponding to the current moment is greater than the pressure protection action threshold value; Among them, all the stored pressure values ​​are the pressure values ​​corresponding to each moment in the first time period.

4. The on-load tap changer non-electrical quantity protection method according to claim 3, characterized in that: The method further comprises: If the slope is less than or equal to the preset slope, the stored data of the pressure is cleared, and the new current time when the preset duration is reached is recorded as the new initial time; Jump to the step of determining whether the pressure value corresponding to the new current moment is greater than the pressure protection start threshold value; If the pressure value corresponding to the new current moment is less than or equal to the pressure protection start threshold value, jump to the step of obtaining the pressure value in real time.

5. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The method further comprises: When it is detected that the pressure value is greater than the pressure protection start threshold value, the protection device is started; When it is detected that the pressure value is greater than the pressure protection action threshold value, the protection device is controlled to perform a protection action.

6. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The calculation formula of the pressure protection start threshold value is: p st =K rel p nor.max Among them, p st K is the pressure protection start threshold value; rel is the reliability coefficient; p nor.max is the maximum value of the pressure during normal operation of the on-load tap changer in a non-switching state.

7. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The calculation formula of the pressure protection action threshold value is: p th =K rel p max Among them, p th K is the pressure protection action threshold value; rel is the reliability coefficient; p max It is the maximum value of the pressure when the on-load tap changer is in a switching state during maximum load operation or when an external fault occurs.

8. The on-load tap changer non-electrical quantity protection method according to claim 1, characterized in that: The calculation formula of the slope of the linear regression is: Wherein, m is the slope; p(t) represents the value of the pressure at time t, and n represents the number of moments in the first period; is the average value of the time in the first period; is the average value of the pressure during the first time period.

9. The non-electrical quantity protection method for on-load tap changer according to claim 1, characterized in that: The calculation formula of the preset slope is: M=K rel m max Wherein, M is the preset slope; K rel is the reliability coefficient; m max is the maximum value of the slope of the linear regression determined based on the pressure data within the preset time period when the on-load tap changer is switched normally or subjected to an external disturbance.

10. A non-electrical protection device for an on-load tap changer, characterized in that: include: A monitoring and acquisition module, used for real-time monitoring of the pressure in the oil tank of the on-load tap changer, and when it is monitored that the pressure values ​​corresponding to each moment in the first time period remain within a preset pressure range and the duration of the first time period reaches a preset duration, the pressure values ​​corresponding to each moment in the first time period are acquired; wherein the preset pressure range is greater than a pressure protection start threshold value and less than or equal to a pressure protection action threshold value, the pressure protection start threshold value is used to determine whether to start the protection device of the on-load tap changer, and the pressure protection action threshold value is used to determine whether a serious fault occurs in the on-load tap changer; The judgment and protection module is used to determine the slope of the linear regression of the pressure changing with time based on the value of the pressure corresponding to each moment in the first time period; if the slope is greater than a preset slope, control the protection device to perform a protection action.

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