Steam turbine regenerative system extraction steam short circuit detection method and device in high pressure heater

Abstract

The present application relates to a kind of steam turbine regenerative system steam extraction in high pressure heater short circuit detection method and device, establish the quantitative relationship of steam turbine regenerative system steam extraction in high pressure heater short circuit and high pressure heater upper end difference, high pressure heater lower end difference, high pressure heater temperature rise etc.Parameter, by installing atmospheric pressure gauge and high pressure heater normal drain pipe displacement measuring point, give the judgment basis of steam turbine regenerative system steam extraction in high pressure heater short circuit, simultaneously occur as the final judgment basis of short circuit with three more judgment basis.Compared with prior art, the present application can timely, accurately find the short circuit of steam turbine regenerative system steam extraction in high pressure heater, effectively prevent leakage further expansion, improve the safety and economy of unit operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal-fired power generation, in particular to a method and device for detecting short circuit of extraction steam in high-pressure heater of a steam turbine regenerative system. BACKGROUND

[0002] Under the new situation of the power industry, coal-fired generating units have an increased low-load operation time and frequent start-stop, which adversely affects the safety of unit operation. At the same time, the requirements for the safety of coal-fired generating units are continuously improved, and it is an urgent need to use new technologies to improve the safety level of units.

[0003] The extraction steam regenerative system is an important component of a coal-fired generating unit, and its working principle is as follows: high-temperature and high-pressure superheated steam is extracted from a steam turbine to heat the feedwater in a high-pressure heater, thereby reducing the temperature difference between the feedwater entering the boiler and the furnace and improving the heat exchange efficiency. The high-pressure heater has a surface structure, and the temperature and pressure differences between the steam and the feedwater are large. In addition, the thermal stress generated during start-up is too large, and the water level in the heater is unstable, which can easily cause short circuit of extraction steam in the high-pressure heater. The impact of extraction steam short circuit on the safety and economy of the unit includes: (1) the formation of steam-water two-phase flow in the drain pipe can easily cause steam-water impact on the pipe, affecting the safe operation of the unit; (2) the reduction of extraction steam flow participating in heat exchange can cause a decrease in the outlet water temperature of the heater, affecting the final feedwater temperature and reducing the economic efficiency of the unit; and (3) the participation of high-quality steam in heat exchange in the next stage of the heat exchanger can cause the high-quality heat not to be fully utilized, increasing the heat load of the condenser and reducing the economic efficiency of the unit.

[0004] As can be seen, the short circuit of extraction steam into the high-pressure heater has an important impact on the safety and economy of the unit, and therefore, it is necessary to timely and accurately detect the short circuit of extraction steam in the high-pressure heater: (1) to take timely operation measures to effectively prevent the expansion of extraction steam short circuit accidents; (2) to reduce the problem of reduced economic efficiency of the unit caused by extraction steam short circuit; and (3) to avoid a significant increase in coal consumption of the unit due to severe extraction steam short circuit.

[0005] Currently, the short circuit of regenerative extraction steam in the high-pressure heater is mainly determined by humans, and the relevant data such as the terminal difference of the heater and the feedwater temperature are abnormal, and the judgment is made by relying on rich operation experience and data historical trends, which requires higher ability and experience of the operation personnel. When the personnel find that the relevant parameters of the high-pressure heater are abnormal, the extraction steam short circuit has already occurred, which adversely affects the safe and economic operation of the unit, and there is a lack of an intelligent judgment system for the short circuit of extraction steam into the high-pressure heater. SUMMARY

[0006] The purpose of the present application is to provide a method and device for detecting short circuit of extraction steam in a high-pressure heater of a steam turbine regenerative system.

[0007] The object of the application can be realized by the following technical solutions:

[0008] A steam turbine regenerative system steam extraction short circuit detection method in a high-pressure heater, comprising:

[0009] Step S1: listen to the start signal, and execute step S2 when receiving the start signal;

[0010] Step S2: obtain the lower end difference of the high-pressure heater, and determine whether it exceeds the first set value, if yes, execute step S3, otherwise return to step S1;

[0011] Step S3: obtain the upper end difference of the high-pressure heater, and determine whether it exceeds the second set value, if yes, execute step S5, otherwise, execute step S4;

[0012] Step S4: obtain the temperature rise of the high-pressure heater, and determine whether the difference between the temperature rise and the temperature rise design value under the same load condition exceeds the third set value, if yes, execute step S5, otherwise, return to step S1;

[0013] Step S5: obtain the water level record data of the high-pressure heater, and determine whether the number of times that the water level change amplitude exceeds the fourth set value within a set time period exceeds a set number of times, if yes, execute step S7, otherwise, execute step S6;

[0014] Step S6: obtain the high-pressure heater normal drain pipe swing record data, and determine whether the high-pressure heater normal drain pipe swing value is greater than the fifth set value, if yes, execute step S7, otherwise, return to step S1;

[0015] Step S7: output a pre-warning signal for indicating that a short circuit occurs in the high-pressure heater.

[0016] The step S5 specifically comprises:

[0017] Step S51: obtain the water level record data of the high-pressure heater within a set time period before the current time;

[0018] Step S52: extract all extreme values in the water level record data, wherein the extreme values include maximum values and minimum values;

[0019] Step S53: count the number of extreme value pairs whose adjacent extreme value differences exceed the fourth set value;

[0020] Step S54: determine whether the number of extreme value pairs exceeds a set number of times, if yes, execute step S7, otherwise, execute step S6.

[0021] The set number of times is 3 times, and the fourth set value is 50 mm.

[0022] The first set value is 10 degrees Celsius, and the second set value is 3 degrees Celsius.

[0023] The fifth set value is 2 millimeters.

[0024] A steam turbine regenerative system steam extraction short circuit detection device in a high-pressure heater, comprising a processor, a memory, and a program stored in the memory and executed by the processor, the processor implements the method as described above when executing the program:

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1) The steam turbine regenerative system steam extraction short circuit accident in the high-pressure heater can be found in time, a warning is issued, and a safety accident is avoided,

[0027] 2) It is suitable for high-pressure heater steam inlet short circuit warning of a high-pressure heater and also suitable for high-pressure heater steam inlet short circuit warning of multiple high-pressure heaters, and has strong practicability and can meet different needs of power generation enterprises,

[0028] 3) A one-to-one correspondence between the steam inlet short circuit and five operating parameters is established, and the simultaneous occurrence of more than three judgment bases is simultaneously triggered as the final judgment basis, which improves the judgment accuracy,

[0029] 4) The steam extraction short circuit of the regenerative system in the high-pressure heater can be found in time, continuous low-efficiency operation of the regenerative system is avoided, and economic losses are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a structure schematic diagram of the embodiment judgment method of the present application;

[0031] Figure 2 is a high-pressure heater local schematic diagram of the embodiment judgment method of the present application;

[0032] Wherein: 1, #1 high-pressure heater, 2, #2 high-pressure heater, 3, #3 high-pressure heater, 4, deaerator, 11, boiler, 12, steam turbine high-pressure cylinder, 13, steam turbine medium-pressure cylinder, 14, generator, 15, feed water pump, 21, first-stage steam extraction pipeline, 22, second-stage steam extraction pipeline, 23, third-stage steam extraction pipeline, 24, fourth-stage steam extraction pipeline, 31, main steam pipeline, 32, high-pressure cylinder exhaust pipeline, 33, reheat steam pipeline, 34, medium-pressure cylinder exhaust pipeline, 35, condensate water pipeline, 36, reheat water reducing pipeline, 37, feed water pipeline, 41, #1 high-pressure heater normal drainage regulating valve, 42, #2 high-pressure heater normal drainage regulating valve, 43, #3 high-pressure heater normal drainage regulating valve, 51, #1 high-pressure heater water level gauge, 52, #2 high-pressure heater water level gauge, 53, #3 high-pressure heater water level gauge, P0, atmospheric pressure, P1, #1 high-pressure heater inlet steam pressure, t 1jq#1 high-pressure heater steam inlet temperature, t 1ss #1 high-pressure heater drain temperature, t 1js #1 high-pressure heater water inlet temperature, t 1cs #1 high-pressure heater water outlet temperature, P2, #2 high-pressure heater steam inlet pressure, t 2jq #2 high-pressure heater steam inlet temperature, t 2ss #2 high-pressure heater drain temperature, t 2js #2 high-pressure heater water inlet temperature, t 2cs #2 high-pressure heater water outlet temperature, P3, #3 high-pressure heater steam inlet pressure, t 3jq #3 high-pressure heater steam inlet temperature, t 3ss #3 high-pressure heater drain temperature, t 3js #3 high-pressure heater water inlet temperature, t 3cs #3 high-pressure heater water outlet temperature, δ1, #1 high-pressure heater normal drain pipeline displacement, δ2, #2 high-pressure heater normal drain pipeline displacement, δ3, #3 high-pressure heater normal drain pipeline displacement. DETAILED DESCRIPTION

[0033] The application will be described in detail below in conjunction with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0034] A judgment method for short circuit of steam extraction in a high-pressure heater in a steam turbine regenerative system is disclosed in the embodiments, which can timely and accurately find the steam inlet short circuit of the high-pressure heater. Referring to Figure 1 , the judgment system comprises a #1 high-pressure heater 1, a #2 high-pressure heater 2, a #3 high-pressure heater 3, a deaerator 4, a boiler 11, a steam turbine high-pressure cylinder 12, a steam turbine medium-pressure cylinder 13, a generator 14, a feedwater pump 15, a first-stage steam extraction pipeline 21, a second-stage steam extraction pipeline 22, a third-stage steam extraction pipeline 23, a fourth-stage steam extraction pipeline 24, a main steam pipeline 31, a high-pressure cylinder exhaust steam pipeline 32, a medium-pressure cylinder steam inlet pipeline 33, a medium-pressure cylinder exhaust steam pipeline 34, a condensate water pipeline 35, a reheater desuperheating water pipeline 36, and a feedwater pipeline 37.

[0035] The boiler 11 has a feedwater inlet and a steam outlet. The steam outlet enters the steam turbine high-pressure cylinder 12 through the main steam pipeline 31. After the steam does work in the steam turbine high-pressure cylinder 12, it enters the boiler 11 through the high-pressure cylinder exhaust steam pipeline 32 for heating. The reheated steam enters the steam turbine medium-pressure cylinder 13 for work. After the work, the steam is discharged through the exhaust steam pipeline 34. The steam condenses into water and enters the deaerator 4 through the condensate water pipeline 35 for heating. The feedwater enters the boiler 11 after being heated by the #3 high-pressure heater 3, the #2 high-pressure heater 2, and the #1 high-pressure heater 1 in turn.

[0036] The outlet of the deaerator 4 is connected with the inlet of the feed water pump 15, the outlet of the feed water pump 15 is connected with the inlet of the #3 high pressure heater 3, the outlet of the #3 high pressure heater 3 is connected with the inlet of the #2 high pressure heater 2, the outlet of the #2 high pressure heater 2 is connected with the inlet of the #1 high pressure heater 1, and the outlet of the #1 high pressure heater 1 is connected with the inlet of the feed water pipeline 37 of the boiler 11.

[0037] The bottoms of the #1 high pressure heater 1, the #2 high pressure heater 2 and the #3 high pressure heater 3 are respectively provided with a drain outlet; the drain outlet of the bottom of the #1 high pressure heater 1 is connected with the #2 high pressure heater 2, the drain outlet of the bottom of the #2 high pressure heater 2 is connected with the #3 high pressure heater 3, and the drain outlet of the bottom of the #3 high pressure heater 3 is connected with the deaerator 4.

[0038] The two ends of the first stage extraction pipeline 21 are respectively connected with the high pressure cylinder 12 of the steam turbine and the #1 high pressure heater 1, the two ends of the second stage extraction pipeline 22 are respectively connected with the high pressure cylinder 12 of the steam turbine and the #2 high pressure heater 2, the two ends of the third stage extraction pipeline 23 are respectively connected with the medium pressure cylinder 13 of the steam turbine and the #3 high pressure heater 3, and the two ends of the fourth stage extraction pipeline 24 are respectively connected with the medium pressure cylinder 13 of the steam turbine and the deaerator 4.

[0039] The inventor establishes the quantitative relationship between the short circuit of the extraction of the regenerative system in the high pressure heater and the upper end difference, the lower end difference, the temperature rise of the high pressure heater, etc., determines the judgment basis of the short circuit of the extraction of the regenerative system in the high pressure heater, and discovers the short circuit accident of the extraction of the regenerative system in the high pressure heater in time.

[0040] The judgment method of the short circuit of the extraction of the regenerative system in the high pressure heater is provided, the judgment method is implemented by using the above method, and the judgment method and basis are as follows.

[0041] The judgment basis of the short circuit of the extraction of the regenerative system in the #1 high pressure heater is that the extraction in the high pressure heater causes the increase of the lower end difference, the increase of the upper end difference, the fluctuation of the water level, the swing of the normal drain pipeline, the decrease of the temperature rise of the heater under the same load condition, and the following conditions are met: ① the lower end difference of the high pressure heater t 1ss -t 1js ≥ 10℃, ② the upper end difference pswsat_t(P1+P0)-t 1cs ≥ 3℃, ③ the temperature rise of the high pressure heater t 01cs -t 01js -t 1cs +t 1js≥ 3℃, ④ high pressure heater water level change amplitude more than 50 mm and more than 3 times within 3 minutes, ⑤ high pressure heater normal drain pipe swing value δ ≥ 2 mm, the five boundary conditions are as the basis for judging that the regenerative system extraction steam occurs short circuit in the high pressure heater;

[0042] The basis for judging that the regenerative system extraction steam occurs short circuit in the #2 high pressure heater is that the extraction steam occurs short circuit in the high pressure heater, causing the high pressure heater lower end difference to rise, the upper end difference to rise, the water level to fluctuate, the normal drain pipe to swing, and the heater temperature rise to decrease under the same load condition, so that ① the high pressure heater lower end difference t 2ss -t 2js ≥ 10℃, ② the upper end difference pswsat_t(P2+P0)-t 2cs ≥ 3℃, ③ the high pressure heater temperature rise deviation t 02cs -t 02js -t 2cs +t 2js ≥ 3℃, ④ the high pressure heater water level change amplitude more than 50 mm and more than 3 times within 3 minutes, ⑤ the high pressure heater normal drain pipe swing value δ ≥ 2 mm, the five boundary conditions are as the basis for judging that the regenerative system extraction steam occurs short circuit in the high pressure heater.

[0043] The basis for judging that the regenerative system extraction steam occurs short circuit in the #3 high pressure heater is that the extraction steam occurs short circuit in the high pressure heater, causing the high pressure heater lower end difference to rise, the upper end difference to rise, the water level to fluctuate, the normal drain pipe to swing, and the heater temperature rise to decrease under the same load condition, so that ① the high pressure heater lower end difference t 3ss -t 3js ≥ 10℃, ② the upper end difference pswsat_t(P3+P0)-t 3cs ≥ 3℃, ③ the high pressure heater temperature rise deviation t 03cs -t 03js -t 3cs +t 3js ≥ 3℃, ④ the high pressure heater water level change amplitude more than 50 mm and more than 3 times within 3 minutes, ⑤ the high pressure heater normal drain pipe swing value δ ≥ 2 mm, the five boundary conditions are as the basis for judging that the regenerative system extraction steam occurs short circuit in the high pressure heater.

[0044] To avoid the influence of occasional factors, at least one of the boundary conditions ①+② / ③ and at least one of ④ / ⑤ are as the final basis for judging that the regenerative system extraction steam occurs short circuit in the high pressure heater.

[0045] Specifically, the above judgment logic is realized in the form of a computer program, and the computer program realizes the following steps when executed:

[0046] A steam turbine regenerative system extraction steam short circuit detection method in a high-pressure heater, comprising:

[0047] Step S1: listen to the start signal, and execute step S2 when receiving the start signal;

[0048] Step S2: obtain the high-pressure heater lower end difference, and determine whether it exceeds 10 degrees Celsius, if yes, execute step S3, otherwise return to step S1;

[0049] Step S3: obtain the high-pressure heater upper end difference, and determine whether it exceeds 3 degrees Celsius, if yes, execute step S5, otherwise, execute step S4;

[0050] Step S4: obtain the temperature rise of the high-pressure heater, and determine whether the difference with the temperature rise design value under the same load condition exceeds a third set value, if yes, execute step S5, otherwise, return to step S1;

[0051] Step S5: obtain the water level record data of the high-pressure heater, and determine whether the number of times that the water level change amplitude exceeds 50 millimeters within a set time period exceeds 3 times, if yes, execute step S7, otherwise, execute step S6, specifically including:

[0052] Step S51: obtain the water level record data of the high-pressure heater within a set time period before the current time;

[0053] Step S52: extract all extreme values in the water level record data, wherein the extreme values include maximum and minimum values;

[0054] Step S53: count the number of extreme value pairs whose adjacent extreme value difference exceeds a fourth set value;

[0055] Step S54: determine whether the number of extreme value pairs exceeds a set number of times, if yes, execute step S7, otherwise, execute step S6.

[0056] Step S6: obtain the high-pressure heater normal drain pipe swing record data, and determine whether the high-pressure heater normal drain pipe swing value is greater than 2 millimeters, if yes, execute step S7, otherwise, return to step S1;

[0057] Step S7: output a pre-warning signal for indicating that a short circuit occurs in the high-pressure heater.

[0058] In summary, the accuracy can be improved while reducing the consumption of computing resources, and the execution efficiency of the program can be improved.

[0059] The following is an example application analysis:

[0060] A 300 MW unit in a domestic power plant is taken as an example for embodiment analysis, which is equipped with three high-pressure heaters and one deaerator. The above-mentioned equipment is installed and numbered according to the embodiment structure diagram, #1 high-pressure heater 1, #2 high-pressure heater 2, #3 high-pressure heater 3, deaerator 4.

[0061] Under the rated power condition of 300 MW, the design parameters of #1 high-pressure heater are: the upper end difference is-1.6℃, the lower end difference is 5.6℃, and the heater temperature rise is 30.5℃. The unit is stably running, and each operating parameter is normal. With the increase of unit start-stop times and running time, under the rated power condition of the unit, the temperature of #1 high-pressure heater gradually increases, the lower end difference reaches 10℃, at this time, the water level of #1 high-pressure heater starts to fluctuate, and the outlet water temperature of #1 high-pressure heater starts to decrease, when the lower end difference of #1 high-pressure heater reaches 12℃, and the heater temperature rise decreases by 4℃, the water level of high-pressure heater fluctuates 50mm and 3 times in 2 minutes, three judgment criteria occur at the same time, triggering the short circuit alarm of regenerative system steam extraction in #1 high-pressure heater. Field inspection found that the drain pipe of #1 high-pressure heater had a shaking phenomenon, which further confirmed the fact that the regenerative system steam extraction in #1 high-pressure heater had a short circuit.

[0062] The unit operation personnel took the high-pressure heater de-parallel measures, exited the high-pressure heater steam side operation and water side operation, and switched to water side bypass operation. The #1 high-pressure heater drain pipe was cut on site, and the drain pipe on the same side of the drain cooling section was inspected, and it was found that the shell had a hole caused by erosion, and the shell and the weld of the end tube plate had a gap caused by erosion, which verified the accuracy of the alarm system.

[0063] Through the judgment method of short circuit of turbine regenerative system steam extraction in high-pressure heater, it can be seen that the influence of high-pressure heater intelligent early warning system on the safety and economy of turbine operation mainly reflects in the following aspects.

[0064] 1) Timely and accurately find the #1 high-pressure heater inlet short circuit and give an early warning, check the holes caused by shell erosion, and verify the accuracy of the analysis and judgment;

[0065] 2) After the warning, the unit operation personnel take timely measures to effectively prevent the expansion of the inlet short circuit accident, avoid safety accidents caused by inlet short circuit, and even the risk of unit non-stop;

[0066] 3) If the high-pressure heater inlet short circuit is not found in time, the heat exchange effect will be deteriorated, the operating end difference will be increased, and the feedwater temperature will be reduced, which will increase the unit coal consumption by more than 1.1g / (kW·h), affecting the economic efficiency of unit operation.

[0067] The application relates to a method for judging short circuit of steam extraction of a steam turbine regenerative system in a high-pressure heater, and the method analyzes the influence of high-pressure heater steam inlet short circuit on operation parameters, establishes one-to-one correspondence between the steam inlet short circuit and the operation parameters, and develops an intelligent early warning system for the short circuit of steam extraction of the regenerative system in the high-pressure heater, so that the high-pressure heater steam inlet short circuit can be judged in time and accurately, the early warning system is practical, and has a wide application prospect.

[0068] In addition, it should be noted that the specific embodiments described in the specification, the shape of the zero, the components, the name taken, etc. can be different, and the above described in the specification is only an example of the structure of the application. Any equivalent changes or simple changes made according to the structure, features and principles of the patent concept of the application are included in the protection scope of the patent. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the structure of the application or exceed the scope defined by the claims, which should belong to the protection scope of the application.

Claims

1. A method for detecting short circuit of extraction steam of a steam turbine regenerative system in a high pressure heater, characterized by, The method comprises the following steps: Step S1: listening to a start signal and executing step S2 when the start signal is received; Step S2: obtaining a lower end difference of the high-pressure heater and judging whether the lower end difference exceeds a first set value, if yes, executing step S3, otherwise returning to step S1; Step S3: obtaining an upper end difference of the high-pressure heater and judging whether the upper end difference exceeds a second set value, if yes, executing step S5, otherwise executing step S4; Step S4: obtaining a temperature rise of the high-pressure heater and judging whether a difference between the temperature rise and a temperature rise design value under a same load condition exceeds a third set value, if yes, executing step S5, otherwise returning to step S1; Step S5: obtaining a water level lower end difference record data of the high-pressure heater and judging whether a number of times that a water level change amplitude exceeds a fourth set value within a set time period exceeds a set number of times, if yes, executing step S7, otherwise executing step S6; Step S6: obtaining a normal drain pipe swing record data of the high-pressure heater and judging whether a normal drain pipe swing value of the high-pressure heater is greater than a fifth set value, if yes, executing step S7, otherwise returning to step S1; Step S7: outputting a pre-warning signal for representing that a short circuit occurs in the high-pressure heater; The set number of times is 3, and the fourth set value is 50 mm; The first set value is 10 degrees Celsius, the second set value is 3 degrees Celsius, and the third set value is 3 degrees Celsius; The fifth set value is 2 mm.

2. A method of detecting short circuiting of extraction steam in a high pressure heater in a steam turbine regenerative system according to claim 1, characterized by, The step S5 specifically comprises: Step S51: obtaining water level record data of the high-pressure heater within a certain time period before a current time; Step S52: extracting all extreme values in the water level record data, wherein the extreme values include maximum values and minimum values; Step S53: counting a number of extreme value pairs whose adjacent extreme values exceed the fourth set value; Step S54: judging whether the number of extreme value pairs exceeds the set number of times, if yes, executing step S7, otherwise executing step S6.

3. A device for detecting short circuit of extraction steam of a steam turbine regenerative system in a high pressure heater, comprising a processor, a memory, and a program stored in the memory and executed by the processor, characterized in that, The processor implements the following steps when executing the program: Step S1: listening to a start signal and executing step S2 when the start signal is received; Step S2: obtaining a lower end difference of the high-pressure heater and judging whether the lower end difference exceeds a first set value, if yes, executing step S3, otherwise returning to step S1; Step S3: obtaining an upper end difference of the high-pressure heater and judging whether the upper end difference exceeds a second set value, if yes, executing step S5, otherwise executing step S4; Step S4: obtaining a temperature rise of the high-pressure heater and judging whether a difference between the temperature rise and a temperature rise design value under a same load condition exceeds a third set value, if yes, executing step S5, otherwise returning to step S1; Step S5: obtaining water level record data of the high-pressure heater and judging whether a number of times that a water level change amplitude exceeds a fourth set value within a set time period exceeds a set number of times, if yes, executing step S7, otherwise executing step S6; Step S6: obtaining a normal drain pipe swing record data of the high-pressure heater and judging whether a normal drain pipe swing value of the high-pressure heater is greater than a fifth set value, if yes, executing step S7, otherwise returning to step S1; Step S7: outputting a pre-warning signal for representing that a short circuit occurs in the high-pressure heater; The first setting value is 10 degrees Celsius, the second setting value is 3 degrees Celsius, and the third setting value is 3 degrees Celsius. The fifth setting value is 2 millimeters. The step S5 specifically comprises:

4. A device for detecting short circuit of extraction steam in a high pressure heater in a steam turbine regenerative system according to claim 3, characterized by Step S51: obtaining water level record data of the high-pressure heater in a fixed time period before the current time; Step S52: extracting all extreme values in the water level record data, wherein the extreme values include maximum values and minimum values; Step S53: counting the number of extreme value pairs whose difference exceeds the fourth setting value; Step S54: determining whether the number of extreme value pairs exceeds a set number of times, and if yes, executing step S7, otherwise executing step S6. ​

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