CN111006741A - Oil level abnormity detection method and system for oil-immersed transformer body - Google Patents
Oil level abnormity detection method and system for oil-immersed transformer body Download PDFInfo
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
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Abstract
The invention discloses an oil level abnormity detection method and system for an oil immersed transformer body, wherein the oil level of the transformer is in a linear relation with the change of oil temperature in an oil level range of 30-70%, and the actual oil level value and the actual oil temperature value of the transformer are directly obtained through reading; under a certain oil temperature value, setting a fluctuation range value of an oil level value and an error value of the oil temperature value, and calculating through a linear relation to obtain an upper limit value and a lower limit value of an oil level; and if the oil level value is not in a range value formed by the upper limit value and the lower limit value, outputting an abnormal signal of the oil level. According to the invention, the oil level and oil temperature curves of the transformer are fitted, the upper limit value and the lower limit value of the oil level of the transformer are calculated, the actual oil level is compared with the upper limit value and the lower limit value, the detection of the abnormal fault of the oil level of the transformer is realized, the periodic sampling of the actual oil level is compared with the lower limit value, the oil leakage fault of the transformer body is further judged, the early warning of the fault is realized, and the real-time monitoring of the change of the oil level in the transformer is facilitated.
Description
Technical Field
The invention relates to the technical field of oil level detection of transformers, in particular to a method and a system for detecting abnormal oil level of an oil-immersed transformer body.
Background
An oil-immersed transformer is mainly insulated by insulating oil and depends on oil as cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling and forced oil circulation. The transformer oil level is too low or the transformer oil is seriously lack under the conditions of oil leakage or a large amount of oil leakage for a long time, untimely supplement after maintenance and oil discharge, insufficient oil storage capacity of an oil conservator due to too low temperature and the like. In addition, the false oil level of the transformer can be caused by the blockage of an oil gauge pipe, the blockage of a pointer type oil level gauge clamping needle, the blockage of an explosion-proof pipe vent hole, the blockage of a respirator, the accumulation of gas under a diaphragm or a capsule, the rupture of the diaphragm or the capsule and the like. When the oil level of the transformer oil is low to a certain degree, the misoperation of light gas protection can be caused; when oil is seriously lacked, the internal winding is exposed, the insulation of the internal winding is reduced, and insulation damage and breakdown accidents can be caused; the lack of transformer oil can severely expose the internal windings, making the windings susceptible to moisture and reduced insulation. Therefore, the change trend of the reading of the body oil level meter needs to be monitored during the operation process of the transformer, and the defect of abnormal oil level of the transformer is discovered in time. However, the reading of the oil level of the transformer body varies with the variation of the oil temperature, and the oil level varies with the oil temperature, so that the judgment of the abnormality of the oil level becomes difficult.
The transformer oil level can be calculated using the following formula:
wherein Δ V is a change in volume of the oil due to a change in temperature; g is the quality of the transformer oil; rho is the density of the transformer oil at 20 ℃, and is 0.88kg/dm 3; gamma is temperature expansion coefficient, 0.78X 10-3K-1; delta T is the change value of the oil temperature of the transformer at DEG C.
For a cylindrical tank with the conservator horizontally disposed, the level gauge indicates the proportion of the liquid level in the conservator, i.e., the percentage of the liquid level to the diameter of the conservator. When the volume expansion change of oil in the transformer body is delta V by taking V20 ℃ as a reference, the oil level change caused by the oil volume expansion change in the cylindrical oil conservator meets the following conditions:
in the formula, H20 ℃ is the initial oil level% of the transformer when the oil temperature is 20 ℃; h is the expanded transformer oil level,%; is the diameter of the conservator, m; d is the length of the oil conservator, and the change range of the D is 0-R, m; h is the oil level gauge reading, i.e. the percentage of oil level to conservator diameter,%.
The oil temperature meter measures the top-layer hot spot oil temperature of the transformer, represents the hot spot temperature of the oil in the transformer body, and is higher than the average temperature of the oil in the actual transformer body, so that the calculated theoretical value of the oil level is higher than the actual value. Therefore, the method for calculating the theoretical value of the oil level of the transformer body by using the theoretical formula cannot accurately judge the actual condition of the oil level of the transformer body.
Disclosure of Invention
Aiming at the problems, the invention provides a method and a system for detecting the oil level abnormity of an oil-immersed transformer body, and mainly solves the technical problem that the actual condition of the oil level of the transformer body cannot be accurately judged by a method for calculating the theoretical value of the oil level of the transformer body by a theoretical formula.
The invention provides an oil level abnormity detection method for an oil immersed transformer body, wherein the oil level of the transformer is approximately in a linear relation with the change of oil temperature in an oil level range of 30-70%, and the actual oil level value and the actual oil temperature value of the transformer are directly obtained through reading; under a certain oil temperature value, setting a fluctuation range value of an oil level value and an error value of the oil temperature value, and calculating through a linear relation to obtain an upper limit value and a lower limit value of an oil level; and if the oil level value is not in a range value formed by the upper limit value and the lower limit value, outputting an abnormal signal of the oil level.
Further, the relation curve of the oil level value and the oil temperature value is h ═ λ T + h0H is the actual oil level value of the transformer, namely the percentage of the oil level to the diameter of the oil conservator, and the range is 0-100%; t is the value of an actual oil temperature table and the unit is; h is0Is a constant in a linear fitting formula of the transformer, and the unit is%; λ is the slope in the linear fit equation for different transformers, in%/deg.C.
Further, under a certain oil temperature value, the fluctuation range value of the set oil level value is +/-20%, and the error value of the oil temperature value is +/-2.5 ℃; obtaining the upper limit value h of the oil level under the set oil temperaturemaxLower limit value hminRespectively as follows: h ismax＝1.2*[λ*(T+2.5)+h0]、hmin＝0.8*[λ*(T-2.5)+h0]。
Further, when the actual oil level value is higher than the upper limit value of the oil level or lower than the lower limit value of the oil level at a certain temperature, an alarm is triggered.
Further, when the actual oil level value is lower than the oil level lower limit value at a certain temperature, oil leakage detection logic is triggered; the oil leak detection logic steps include: and sampling and detecting the actual oil level value for a plurality of times in a certain sampling period, comparing the difference value of the actual oil level value with the lower limit value of the oil level, and outputting a signal that the oil leakage fault of the transformer exists if the obtained oil level difference value is greater than the set oil leakage alarm value.
Further, the sampling period in the oil leakage detection logic step is 30 minutes, and 6 sampling periods are continuously detected; the oil leakage alarm value is determined according to the sampling period, and when the sampling period is 30 minutes, the oil leakage alarm value is set to be 3%.
An oil level abnormity detection system of an oil-immersed transformer body comprises a pressure sensor for detecting the oil level value of the transformer body, a temperature sensor for detecting the oil temperature value, and an oil level abnormity detection module for judging whether the actual oil level value is abnormal or not according to the oil level value obtained by the pressure sensor; and the warning module is used for determining the reason of the oil level abnormity according to the signal of the oil level abnormity detection module and generating corresponding warning information.
Further, the oil level abnormality detection module comprises an abnormality detection device for an oil level upper limit alarm value and an oil level lower limit alarm value; acquiring an actual oil level value and an actual oil temperature value of the transformer, combining a set fluctuation range value of the oil level value and an error value of the oil temperature value, a slope and a constant obtained by linear relation of the oil level and the oil temperature, calculating an upper limit alarm value and a lower limit alarm value of the oil level by using a linear relation, and sending an output signal to an alarm module if the actual oil level value exceeds the upper limit alarm value or is lower than the lower limit alarm value;
the oil level upper limit warning value abnormality detection device includes:
the input end of the first adder is used for acquiring an actual oil temperature value and an error value of the oil temperature;
the input end of the first multiplier acquires the slope and is connected with the output end of the first adder;
the input end of the second adder obtains the constant and is connected with the output end of the first multiplier;
the input end of the second multiplier acquires the fluctuation range value and is connected with the output end of the second adder;
a first comparator: the input end acquires an actual oil level value and the output end is connected with the second multiplier, and when the actual oil level value is larger than an output signal of the second multiplier, the output end outputs an oil level abnormal over-high alarm signal to the alarm module;
the oil level lower limit warning value abnormality detection device includes:
the input end of the first subtracter is used for acquiring an actual oil temperature value and an error value of the oil temperature;
the input end of the third multiplier acquires the slope and is connected with the output end of the first subtracter;
the input end of the third adder obtains the constant and is connected with the output end of the third multiplier;
the input end of the fourth multiplier acquires the fluctuation range value and is connected with the output end of the third adder;
and when the actual oil level value is smaller than an output signal of the fourth multiplier, the output end outputs an oil level abnormal low alarm signal to the alarm module.
The oil leakage detection device comprises a second subtracter, an absolute value arithmetic unit, a latch, a third comparator and an AND gate logic unit which are sequentially connected; the input end of the second subtracter acquires an actual oil level value and is connected with the output end of the fourth multiplier, and the actual oil level value and the output end of the fourth multiplier are used for calculating a difference value between the actual oil level value and an oil level lower limit alarm value; the latch is used for latching the signal output by the absolute value arithmetic unit and periodically outputting the signal to the third comparator; the input end of the third comparator is also used for acquiring an oil leakage fixed value number, and if the result output by the latch is greater than the oil leakage fixed value number, an oil leakage signal is output; and if the AND gate logic simultaneously acquires the oil leakage signal output by the third comparator and the oil level abnormal low warning signal output by the second comparator, the output end of the AND gate logic outputs a transformer oil leakage warning signal to the warning module.
Further, the fluctuation range value of the oil level is +/-20%, and the oil temperature error value is +/-2.5 ℃.
The invention has the beneficial effects that: the method comprises the steps of fitting oil level and oil temperature curves of the transformer, calculating upper limit value and lower limit value of the oil level of the transformer, comparing the actual oil level with the upper limit value and the lower limit value to detect abnormal faults of the oil level of the transformer, comparing periodic sampling of the actual oil level with the lower limit value to further judge oil leakage faults of a transformer body, and realizing early warning of faults, so that the method is beneficial to monitoring changes of the oil level in the transformer in real time, and solves the problem that the oil level state of the transformer is difficult to judge visually along with changes of the oil temperature; the transformer on-line monitoring system for the transformer substation can timely find the abnormal fault condition of the oil level of the transformer and avoid the occurrence of the tripping event of the transformer.
Drawings
Fig. 1 is a schematic diagram of upper and lower limit values of an oil temperature value and an oil level value of an oil-immersed transformer according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a method for detecting abnormal oil level in an oil-immersed transformer body according to an embodiment of the present invention;
fig. 3 is a logic diagram of an oil level abnormality detection system for an oil-immersed transformer body according to an embodiment of the invention.
Detailed Description
In order to further understand the present invention, the following detailed description will be made with reference to the following examples, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, so to speak, as communicating between the two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art. The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
According to fig. 2, the present embodiment provides a method for detecting an abnormal oil level of an oil-immersed transformer body, and according to the existing theoretical analysis result, the oil level of the transformer is basically in a linear relationship with the change of the oil temperature in an oil level range of 30% to 70%, so that the actual oil level value and the actual oil temperature value of the transformer are directly obtained through reading; under a certain oil temperature value, setting a fluctuation range value of an oil level value and an error value of the oil temperature value, and calculating through a linear relation to obtain an upper limit value and a lower limit value of an oil level; and if the oil level value is not in a range value formed by the upper limit value and the lower limit value, outputting an abnormal signal of the oil level. That is, the linear variation relationship between the oil level value and the oil temperature value and the error value between the oil level value and the oil temperature value are used to calculate the upper limit value and the lower limit value of the oil level value under the set oil temperature value, and the upper limit value and the lower limit value are used as the judgment result to judge whether the oil level value is in the normal data range. The oil level reading of the transformer body can change along with the change of the oil temperature, the technical problem that the oil level is difficult to judge the abnormal oil level along with the change of the oil temperature is solved, the error values of the oil level value and the oil temperature value are added in the linear relation calculation, the accuracy of the method is further improved, and the obtained result is closer to the actual numerical value in the transformer body.
And obtaining a relation curve of the oil level value and the oil temperature value. Generally, the oil level of the transformer in normal operation is in a range of 30% -70%, so that the operation data can be linearly fitted, and a relation curve of an oil temperature value and an oil level value is fitted through a large amount of data of the transformer in normal operation to obtain the relation curve of the oil level value and the oil temperature value, wherein h is lambda T + h0H is the actual oil level value of the transformer, namely the percentage of the oil level to the diameter of the oil conservator, and the range is 0-100%; t is the value of an actual oil temperature table and the unit is; h is0Is a constant in a linear fitting formula of the transformer, and the unit is%; λ is the slope in the linear fit equation for different transformers, in%/deg.C. I.e. lambda and h0The numerical values of (a) can be obtained by experiments, and the data can be obtained by a person skilled in the art without further description.
The fluctuation range value of the oil level is set. When the oil temperature of the transformer body is higher, the possibility that the distribution of the internal temperature gradient of the body oil is more different is higher, and the range of the oil level fluctuation is likely to be larger. Setting the fluctuation range of the oil level to be +/-20%, namely setting the upper limit of the oil level to be 1.2 times of the fitting value and the lower limit to be 0.8 of the fitting value at a certain temperature; the oil level upper limit value, namely the highest calculated value, is a value calculated according to the change relation of the theoretical oil level along with the oil temperature, and the actual oil level value is not higher than the upper limit value when the oil level is in normal operation; the fitting calculation oil level value is used for fitting the calculated oil level value according to historical data, the upper limit value and the lower limit value of the oil level are within a set fluctuation range of +/-20%, and the oil level value is within the range of the upper limit value and the lower limit value under normal conditions.
And selecting an error value of the oil temperature value. Considering the influence of possible errors of the oil temperature gauge measurement value on the oil level, the error range of the thermometer is generally +/-5 ℃, and in order to make the calculated fixed value as accurate as possible, the error of +/-2.5 ℃ is considered.
As shown in fig. 1, taking 50 ℃ oil temperature as an example, if the error of the oil temperature gauge is not taken into consideration, the upper and lower limit values of the oil level are F, E points. When the oil temperature measurement error is taken into consideration, the lower limit of the temperature deviation is 47.5 ℃, the upper limit is 52.5 ℃, the upper limit and the lower limit of the oil level corresponding to the upper limit and the lower limit of the temperature deviation are A, B, C, D four points respectively, namely when the oil temperature is taken into consideration as 50 ℃, the lowest oil level is A point and the highest oil level is D point within the variation range of +/-20% of the set oil level and the error action of the temperature meter. Further, the upper limit value h of the oil level at a certain temperature can be setmaxLower limit value hminComprises the following steps: h ismax＝1.2*[λ*(T+2.5)+h0]、hmin＝0.8*[λ*(T-2.5)+h0]。
And when the actual oil level value is higher than the upper limit value of the oil level or lower than the lower limit value of the oil level at a certain temperature, triggering an alarm to prompt an operator to overhaul and maintain the transformer.
Specifically, when the actual oil level value is higher than the upper limit value of the oil level at a certain temperature, it may be that there is an abnormality in the oil level gauge or the oil passage, or the temperature gradient difference of the oil inside the transformer is small due to poor cooling effect of the cooler of the transformer, and the average temperature of the oil is close to the top hot spot oil temperature measured by the oil temperature gauge, so that the oil level value deviates from the upper limit value and approaches the highest calculated value.
When the actual oil level is lower than the lower limit value h of the oil level at a certain temperatureminThere may be an abnormality in the oil level gauge or the oil passage, or there may be an oil leakage in the transformer.
If the oil level indicator is jammed or the oil path is blocked without change, the oil level value exceeds the set h along with the change of the oil temperaturemaxOr hminAt this time, the oil level gauge may also be subjected to troubleshooting using the calculated upper limit value and lower limit value as a criterion.
And detecting oil leakage of the transformer. When the actual oil level value is lower than the oil level lower limit value at a certain temperature, triggering oil leakage detection logic; the oil leak detection logic steps include: and sampling and detecting the actual oil level value for a plurality of times in a certain sampling period, comparing the difference value of the actual oil level value with the lower limit value of the oil level, and outputting a signal that the oil leakage fault of the transformer exists if the obtained oil level difference value is greater than the set oil leakage alarm value.
And continuously detecting N sampling periods by taking 30min as a sampling period, if N is 6, detecting the difference value of the actual oil level value and the actual oil level value, and if the converter transformer continuously leaks oil, taking the criterion of oil leakage detection as follows: h isN·min-hNIf the difference △ K between the actual oil level value and the lower limit value of the oil level is detected to be larger than the oil leakage alarm value K, the transformer is judged to have the oil leakage fault of the body, and the K is determined according to the sampling period, and when the sampling period is 30 minutes, the K can be 3 percent, namely, the oil level is continuously reduced by 0.1 percent per minute.
As shown in fig. 3, the present embodiment further provides an oil level abnormality detection system for an oil-immersed transformer body, including a pressure sensor for detecting an oil level value of the transformer body, a temperature sensor for detecting an oil temperature value, and an oil level abnormality detection module for determining whether an actual oil level value is abnormal according to the oil level value obtained by the pressure sensor; and the warning module 4 is used for determining the reason of the oil level abnormity according to the signal of the oil level abnormity detection module and generating corresponding warning information.
The method provided by the present application is adopted in the use process of the system provided by the embodiment, and therefore the working principle and the working process of the system are not described herein again.
The oil level abnormality detection module comprises an abnormality detection device for an oil level upper limit alarm value and an oil level lower limit alarm value; acquiring an actual oil level value and an actual oil temperature value of the transformer, combining a set fluctuation range value of the oil level value and an error value of the oil temperature value, a slope and a constant obtained by linear relation of the oil level and the oil temperature, calculating an upper limit alarm value and a lower limit alarm value of the oil level by using a linear relation, and sending an output signal to an alarm module if the actual oil level value exceeds the upper limit alarm value or is lower than the lower limit alarm value;
the oil level upper limit warning value abnormality detection device includes:
a first adder 10, the input end of which is used for obtaining the error value of the actual oil temperature value and the oil temperature;
a first multiplier 11, the input end of which obtains the slope and is connected with the output end of the first adder;
a second adder 12, the input end of which obtains the constant and is connected with the output end of the first multiplier;
a second multiplier 13, the input end of which obtains the fluctuation range value and is connected with the output end of the second adder;
the first comparator 14: the input end acquires an actual oil level value and the output end is connected with the second multiplier, and when the actual oil level value is larger than an output signal of the second multiplier, the output end outputs an oil level abnormal over-high alarm signal to the alarm module;
the oil level lower limit warning value abnormality detection device includes:
a first subtractor 20, the input end of which is used to obtain the actual oil temperature value and the error value of the oil temperature;
a third multiplier 21, the input end of which obtains the slope and is connected with the output end of the first subtracter;
a third adder 22, the input end of which obtains the constant and is connected with the output end of the third multiplier;
a fourth multiplier 23, the input end of which obtains the fluctuation range value and is connected with the output end of the third adder;
and the input end of the second comparator 24 acquires the actual oil level value and is connected with the output end of the fourth multiplier, and when the actual oil level value is smaller than the output signal of the fourth multiplier, the output end outputs an oil level abnormal low alarm signal to the alarm module.
The system also comprises an oil leakage detection device, wherein the oil leakage detection device comprises a second subtracter 30, an absolute value arithmetic unit 31, a latch 32, a third comparator, a 33 AND gate logic unit 34 which are sequentially connected; the input end of the second subtracter acquires an actual oil level value and is connected with the output end of the fourth multiplier, and the actual oil level value and the output end of the fourth multiplier are used for calculating a difference value between the actual oil level value and an oil level lower limit alarm value; the latch is used for latching the signal output by the absolute value arithmetic unit and periodically outputting the signal to the third comparator; the input end of the third comparator is also used for acquiring an oil leakage fixed value number, and if the result output by the latch is greater than the oil leakage fixed value number, an oil leakage signal is output; and if the AND gate logic simultaneously acquires the oil leakage signal output by the third comparator and the oil level abnormal low warning signal output by the second comparator, the output end of the AND gate logic outputs a transformer oil leakage warning signal to the warning module.
Specifically, the oil level fluctuation range value is ± 20%, and the oil temperature error value is ± 2.5 ℃.
The invention discloses a method for detecting the oil level abnormality of an oil-immersed transformer body, which is suitable for an oil-immersed transformer of a transformer substation. On the basis of theoretical research and analysis of a large amount of operating data, the oil level of the transformer is proposed to be in a substantially linear relation with the change of the oil temperature within the oil level range of 30% -70%, the oil level and the oil temperature curve of the transformer are fitted according to the oil level and the oil temperature curve of the transformer, the upper limit value and the lower limit value of the oil level of the transformer are calculated, the actual oil level is compared with the upper limit value and the lower limit value, the abnormal fault of the oil level of the transformer is detected, the periodic sampling of the actual oil level is compared with the lower limit value, and the oil leakage fault of the transformer.
The method can solve the problem that the oil level state of the transformer is difficult to judge visually due to the change of the oil temperature, and the condition of the oil level can be predicted more accurately than the condition of the oil level calculated theoretically due to the fact that fitting calculation is carried out by adopting actual data. Under the development trend of information and intelligence of the transformer substation, the invention can be used for the transformer on-line monitoring system of the transformer substation, and can find the abnormal fault condition of the oil level of the transformer in time and avoid the occurrence of the tripping event of the transformer.
The above-described embodiments are merely illustrative of the embodiments of the present invention, and do not limit the spirit and scope of the present invention. Various modifications and improvements of the technical solutions of the present invention may be made by those skilled in the art without departing from the design concept of the present invention, and all of them should fall into the protection scope of the present invention.
Claims (9)
1. The oil level abnormity detection method of the oil-immersed transformer body is characterized in that the oil level of the transformer is in a linear relation with the change of oil temperature in an oil level range of 30% -70%, and a slope and a constant value are obtained; acquiring an actual oil level value and an actual oil temperature value of the transformer, and calculating an upper limit value and a lower limit value of the oil level through a linear relation by combining a fluctuation range value of the set oil level value and an error value of the oil temperature value; and if the actual oil level value is not in a range value formed by the upper limit value and the lower limit value, judging that the oil level is abnormal.
2. The oil-filled transformer body oil level abnormality detection method according to claim 1, wherein a relation curve between the oil level value and the oil temperature value is h- λ T + h0H is the actual oil level value of the transformer, namely the percentage of the oil level to the diameter of the oil conservator, and the range is 0-100%; t is the value of an actual oil temperature table and the unit is; h is0Is a constant in a linear fitting formula of the transformer, and the unit is%; λ is the slope in the linear fit equation for different transformers, in%/deg.C.
3. The oil-immersed transformer body oil level abnormality detection method according to claim 2, wherein under a certain oil temperature value, the fluctuation range value of the set oil level value is ± 20%, and the error value of the oil temperature value is ± 2.5 ℃; obtaining the upper limit value h of the oil level under the set oil temperaturemaxLower limit value hminRespectively as follows: h ismax＝1.2*[λ*(T+2.5)+h0]、hmin＝0.8*[λ*(T-2.5)+h0]。
4. The oil-immersed transformer body oil level abnormality detection method according to claim 1, characterized in that when an actual oil level value is lower than an oil level lower limit value at a certain temperature, an oil leakage detection logic is triggered; the oil leak detection logic steps include: and carrying out sampling detection on the actual oil level value for a plurality of times in a preset sampling period, comparing the difference value of the actual oil level value with the lower limit value of the oil level, and judging that the oil leakage fault of the transformer exists if the obtained oil level difference value is greater than the set oil leakage alarm value.
5. The oil-filled transformer body oil level abnormality detection method according to claim 5, wherein the sampling period in the oil leakage detection logic step is 30 minutes, and 6 sampling periods are continuously detected; the oil leakage alarm value is determined according to the sampling period, and when the sampling period is 30 minutes, the oil leakage alarm value is set to be 3%.
6. The oil level abnormity detection system of the oil-immersed transformer body comprises a pressure sensor for detecting the oil level value of the transformer body and a temperature sensor for detecting the oil temperature value, and is characterized by further comprising an oil level abnormity detection module for judging whether the actual oil level value is abnormal or not according to the oil level value obtained by the pressure sensor; and the warning module is used for determining the reason of the oil level abnormity according to the signal of the oil level abnormity detection module and generating corresponding warning information.
7. The oil-filled transformer body oil level abnormality detection system according to claim 6, wherein the oil level abnormality detection module includes abnormality detection means for an oil level upper limit alarm value and an oil level lower limit alarm value; acquiring an actual oil level value and an actual oil temperature value of the transformer, combining a set fluctuation range value of the oil level value and an error value of the oil temperature value, a slope and a constant obtained by linear relation of the oil level and the oil temperature, calculating an upper limit alarm value and a lower limit alarm value of the oil level by using a linear relation, and sending an output signal to an alarm module if the actual oil level value exceeds the upper limit alarm value or is lower than the lower limit alarm value;
the oil level upper limit warning value abnormality detection device includes:
the input end of the first adder is used for acquiring an actual oil temperature value and an error value of the oil temperature;
the input end of the first multiplier acquires the slope and is connected with the output end of the first adder;
the input end of the second adder obtains the constant and is connected with the output end of the first multiplier;
the input end of the second multiplier acquires the fluctuation range value and is connected with the output end of the second adder;
a first comparator: the input end acquires an actual oil level value and the output end is connected with the second multiplier, and when the actual oil level value is larger than an output signal of the second multiplier, the output end outputs an oil level abnormal over-high alarm signal to the alarm module;
the oil level lower limit warning value abnormality detection device includes:
the input end of the first subtracter is used for acquiring an actual oil temperature value and an error value of the oil temperature;
the input end of the third multiplier acquires the slope and is connected with the output end of the first subtracter;
the input end of the third adder obtains the constant and is connected with the output end of the third multiplier;
the input end of the fourth multiplier acquires the fluctuation range value and is connected with the output end of the third adder;
and when the actual oil level value is smaller than an output signal of the fourth multiplier, the output end outputs an oil level abnormal low alarm signal to the alarm module.
8. The oil-immersed transformer body oil level abnormality detection system according to claim 7, further comprising an oil leakage detection device, wherein the oil leakage detection device comprises a second subtractor, an absolute value operator, a latch, a third comparator and an AND gate logic device which are connected in sequence; the input end of the second subtracter acquires an actual oil level value and is connected with the output end of the fourth multiplier, and the actual oil level value and the output end of the fourth multiplier are used for calculating a difference value between the actual oil level value and an oil level lower limit alarm value; the latch is used for latching the signal output by the absolute value arithmetic unit and periodically outputting the signal to the third comparator; the input end of the third comparator is also used for acquiring an oil leakage fixed value number, and if the result output by the latch is greater than the oil leakage fixed value number, an oil leakage signal is output; and if the AND gate logic simultaneously acquires the oil leakage signal output by the third comparator and the oil level abnormal low warning signal output by the second comparator, the output end of the AND gate logic outputs a transformer oil leakage warning signal to the warning module.
9. The oil-filled transformer body oil level abnormality detection system according to claim 7, wherein the oil level has a fluctuation range value of ± 20%, and the oil temperature error value is ± 2.5 ℃.
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