Performance evaluation method for deep peak regulation steam turbine generator stator

Abstract

The invention provides a performance evaluation method for a deep peak regulation steam turbine generator stator. The performance evaluation method comprises the steps that the axial deformation quantity of a stator bar is calculated according to the temperature of the stator bar, and the axial deformation quantity of a stator core is calculated according to the temperature of the stator core; calculating the relative axial deformation quantity according to the axial deformation quantity of the stator bar and the axial deformation quantity of the stator core; and determining the performance of the generator stator according to the relative axial deformation quantity. According to the existing temperature operation state information of the steam turbine generator, whether the steam turbine generator has the fault hidden danger or not can be accurately judged, the diagnosis efficiency is high, and the method has important significance on early fault prevention, economic loss reduction and power system stability improvement.

Description

Technical Field

[0001] The present application belongs to the field of renewable energy power generation technology, and specifically, relates to a performance evaluation method for a deep peak-shaving steam turbine generator stator. Background Art

[0002] Large steam turbine generators are the core equipment of thermal power plants and play a fundamental supporting role in the power system. Ensuring the safe, reliable and stable operation of thermal power units is of great practical significance for power supply and the development and utilization of renewable energy. In order to solve the problem of clean energy consumption, thermal power steam turbine generator units generally participate in deep peak load regulation operation. The units frequently switch between different operating conditions, and the thermal conditions of key components such as windings are in a dynamic and greatly changing state.

[0003] When a steam turbine generator is operated for a long time at deep peak load regulation, the stator wire rods will expand axially due to the heat generated by the large current. At this time, the magnetic load of the stator core does not change significantly. Therefore, the axial expansion of the stator core can be considered to be zero. The expansion of the stator wire rods causes axial friction stress and displacement relative to the stator core. If it continues for a long time, it is easy to cause the ends of the stator windings to loosen and the insulation to break. The ends of the stator core may also become loose or short-circuited. At present, there is no evaluation method for this problem, which makes it very difficult to evaluate the degradation and life prediction of the stator wire rods and cores of steam turbine generators under deep peak load regulation conditions. Developing an indirect evaluation method for the insulation performance of the stator wire rods of deep peak load regulation steam turbine generators is of great significance for unit maintenance and fault prevention. Summary of the invention

[0004] The technical problem solved by the present application is: how to provide a performance evaluation method for a stator of a deep peak-shaving steam turbine generator that can balance the power fluctuations of the grid to improve the anti-interference capability of the grid.

[0005] The present application provides a performance evaluation method for a deep peak-shaving steam turbine generator stator, the performance evaluation method comprising:

[0006] The axial deformation of the stator wire rod is calculated according to the temperature of the stator wire rod, and the axial deformation of the stator core is calculated according to the temperature of the stator core;

[0007] Calculating a relative axial deformation amount according to the axial deformation amount of the stator wire bar and the axial deformation amount of the stator core;

[0008] The performance of the generator stator is determined according to the relative axial deformation amount.

[0009] Optionally, the calculation formula for the axial deformation of the stator bar is as follows:

[0010] Δl1(t)=α1*l1*[T cu (t)-T0]

[0011] Where Δl1(t) is the axial deformation of the straight part of the stator bar at time t, α1 is the linear thermal expansion coefficient of the stator bar, l1 is the original length of the straight part of the bar, and T cu (t) is the temperature of the stator bar at time t during operation, and T is the temperature of the stator bar at the initial time.

[0012] Optionally, the calculation formula for the axial deformation of the stator core is as follows:

[0013] Δl2(t)=α2*l2*[T fe (t)-T0]

[0014] Where Δl2(t) is the axial deformation of the stator core length at time t, α2 is the linear thermal expansion coefficient of the stator core material, l2 is the original length of the stator core, and T fe is the stator core temperature at time t during operation, and T is the stator core temperature at the initial moment.

[0015] Optionally, the calculation formula for the relative axial deformation is:

[0016]

[0017] Where Δl represents the relative axial deformation.

[0018] Optionally, the method for determining the performance of the generator stator according to the relative axial deformation comprises:

[0019] When the relative axial deformation amount is greater than a first threshold value, it is determined that the stator core has reached a critical point of failure;

[0020] When the relative axial deformation amount is greater than a second threshold, it is determined that the stator bar has reached a critical failure point, wherein the second threshold is greater than the first threshold.

[0021] Optionally, the performance evaluation method further includes:

[0022] The temperature of the stator bar is obtained by the temperature sensor installed between the upper and lower windings of the stator;

[0023] The temperatures of a plurality of similar measuring points are obtained according to the temperature measuring sensors installed on the stator core, and the average temperature of the plurality of similar measuring points is taken as the temperature of the stator core.

[0024] The present application provides a performance evaluation method for a deep peak-shaving steam turbine generator stator, which has the following technical effects:

[0025] Based on the existing temperature operating status information of the steam turbine generator, it is possible to accurately determine whether it has hidden fault hazards. The diagnosis efficiency is high, which is of great significance for early fault prevention, reducing economic losses and improving the stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of the main steps of a performance evaluation method for a deep peak-shaving steam turbine generator stator according to one or more embodiments;

[0027] Figure 2a is an excitation current curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0028] Figure 2b is an active power curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0029] Figure 2c is a three-phase current curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0030] Figure 2d is a line voltage curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0031] Figure 3 is a stator bar temperature curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0032] Figure 4 is an average temperature curve of stator bars from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0033] Figure 5 is a stator bar axial deformation curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0034] Figure 6 is a stator core temperature curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0035] Figure 7 is an average temperature curve of the stator core from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0036] Figure 8 is a stator core axial deformation curve from June to August of a 660MW steam turbine generator according to one or more embodiments;

[0037] Fig. 91 is a curve of relative axial deformation of the stator core and stator bars of a 660MW steam turbine generator from June to August according to one or more embodiments. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] Before describing the various embodiments of the present application in detail, the technical concept of the present application is briefly described first: At present, when performing deep peak regulation, the stator wire rods are prone to axial expansion and the stator core becomes loose due to heat, and there is no good monitoring method for this situation. To this end, the performance evaluation method for the stator of a deep peak regulation steam turbine generator provided by the present application calculates the axial deformation of each of the stator wire rods and the stator core according to the temperature of the stator wire rods and the temperature of the stator core, and further obtains the relative axial deformation of the two based on this, and finally judges the performance of the generator stator. Since the stator current changes frequently and significantly when the steam turbine generator is deeply peak-shaving, which in turn causes a temperature difference between the stator wire bar and the core, and considering the difference in thermal expansion coefficient caused by the difference in material between the stator wire bar and the stator core, the deformation of the stator wire bar relative to the stator core at any time can be calculated, and this deformation is the main cause of faults such as loose stator winding ends, insulation damage, and loose stator core ends and short circuits. Therefore, an indirect evaluation method for the performance of stator windings and cores can be established based on the displacement of the stator wire bar relative to the stator core, which is of great significance for the safety inspection, maintenance and fault prevention of key components of steam turbine generators. The specific principles of the performance evaluation method for the stator of a deep peak-shaving steam turbine generator of this application are described below in conjunction with more embodiments.

[0040] Specifically, Figure 1 As shown, the performance evaluation method for the deep peak-shaving steam turbine generator stator of the first embodiment includes:

[0041] Step S10: Calculate the axial deformation of the stator bar according to the temperature of the stator bar, and calculate the axial deformation of the stator core according to the temperature of the stator core.

[0042] Step S20: Calculate the relative axial deformation according to the axial deformation of the stator bar and the axial deformation of the stator core.

[0043] Step S30: determining the performance of the generator stator according to the relative axial deformation amount.

[0044] In one or more embodiments, the calculation formula of the axial deformation of the stator bar in step S10 is as follows:

[0045] Δl1(t)=α1*l1*[T cu (t)-T0]

[0046] Where Δl1(t) is the axial deformation of the straight part of the stator bar at time t (in m), α1 is the linear thermal expansion coefficient of the stator bar (in m / m°C), l1 is the original length of the straight part of the bar (in m), and T cu (t) is the temperature of the stator bar at time t during operation (in °C), and T0 is the temperature of the stator bar at the initial time (in °C), which generally refers to room temperature. The temperature of the stator bar can be obtained based on the temperature sensor installed between the upper and lower windings of the stator.

[0047] In one or more embodiments, the calculation formula of the axial deformation of the stator core in step S10 is as follows:

[0048] Δl2(t)=α2*l2*[T fe (t)-T0]

[0049] Where Δl2(t) is the axial deformation of the stator core length at time t (in m), α2 is the linear thermal expansion coefficient of the stator core material (in m / m°C), l2 is the original length of the stator core (in m), and T fe is the stator core temperature at time t during operation (in °C), and T0 is the stator core temperature at the initial time (in °C). Among them, the temperatures of multiple similar measuring points can be obtained according to the temperature measuring sensor installed on the stator core, and the average temperature of the multiple similar measuring points is used as the temperature of the stator core.

[0050] In one or more embodiments, the calculation formula of the relative axial deformation in step S20 is:

[0051]

[0052] In the formula, Δl represents the relative axial deformation, which represents the relative axial deformation accumulated from the initial time to time t, and its numerical form is as follows:

[0053]

[0054] In one or more embodiments, the method for determining the performance of the generator stator according to the relative axial deformation in step S30 includes:

[0055] When the relative axial deformation is greater than the first threshold, it is determined that the stator core has reached the critical point of failure; when the relative axial deformation is greater than the second threshold, it is determined that the stator bar has reached the critical point of failure, wherein the second threshold is greater than the first threshold. The first threshold is set to b = 93152m, and the second threshold is set to a = 128780m.

[0056] Since the stator current and stator core temperature are different under different load levels of the generator, and the stator core material is silicon steel and the stator bar material is copper wire, their thermal expansion coefficients are different, which causes the deformation of the stator bar to be different from that of the stator core, thereby generating axial friction stress. This stress and the damage it causes are positively correlated with the relative deformation of the stator bar and the stator core.

[0057] Taking a 660MW steam turbine generator as an example, the stator core teeth 1-12 and stator coils 1-42 are selected to set the measuring points, and the real-time temperature from 0:00 on June 1, 2024 to 0:00 on August 31, 2024 is recorded. The relative expansion and contraction of the stator coil and the stator core is calculated by the theoretical formula, and compared with the actual situation to verify the feasibility of this method. The rated parameters of the steam turbine generator are shown in Table 1 below.

[0058] Table 1 Basic structural parameters of a 660MW steam turbine generator stator

[0059] Stator core outer diameter 2625mm Stator core inner diameter 1312mm Stator core length 6731mm Number of stator slots 42 Number of parallel branches 2

[0060] The following is drawn based on the data of excitation current, active power, three-phase current and line voltage from June to August: Figure 2a ,like Figure 2b ,like Figure 2c , Figure 2d The corresponding curve of the generator. From the overall operation situation, the active power of the generator fluctuates between 300MW and 600MW for a long time, and the operating conditions of the generator are changeable. When the active power is about 300MW, the peak load depth of the generator is around 45.45%.

[0061] When the generator is subjected to deep peak regulation, the operating conditions change significantly, and the stator core and wire rods will be deformed frequently. Calculating the deformation of the stator core and wire rods under deep peak regulation is extremely important for preventing generator failures. The following research is carried out on the stator winding and core respectively.

[0062] The stator winding has 42 slots, with double-layer windings in the slots, and the temperature measurement point is set in the middle of the double-layer winding. Considering that the stator winding is evenly arranged on the stator core, the temperature measurement point data of stator winding 1, 8, 15, 22, 29, 36, and 42 are selected for research. Figure 3 The figure shows the stator bar temperature from June to August. In June and August, the temperature is recorded every 5 seconds, and in July, the interval is 300 seconds. From the curve in the figure, it can be seen that the data changes of the selected temperature measurement points are similar and the difference is not large, so the average value is taken for research, and the average temperature from June to August is plotted as Figure 4 The curve shown.

[0063] According to the average winding temperature from June to August, the axial deformation of the stator bar at time t from June to August can be calculated by the above calculation formula and plotted as Figure 5 As shown. The material of the winding is copper, which has a large linear thermal expansion coefficient, and the winding is the main component that generates heat, so its deformation is large. It can be seen that the deformation change curve of the winding at time t is similar to the change curve of the winding temperature.

[0064] 12 temperature measuring devices are evenly placed on the core, recording the core temperature data from June to August. The temperature data is now plotted as follows: Figure 6 The change curve is shown in the figure. The temperature measurement interval in June and August is 5s, and in July it is 300s. It can be seen from the figure that the core temperature measured at the 12 temperature measurement points has the same change trend, and the data is not much different. In order to facilitate the study, the average temperature of the 12 temperature measurement points is used as the research data and plotted as follows Figure 7 The average temperature variation curve is shown.

[0065] It can be seen from the average core temperature that the core temperature fluctuates in a curve, and the trend of change is roughly rising and then falling. The changing trend of the core temperature shows that the generator is in a frequently changing working condition, but because the main heat-generating component is the winding, the temperature of the core does not change much. The lowest temperature in the three months is around 57°C, and the highest temperature is around 61°C.

[0066] The above calculation formula can be used to calculate the axial deformation of the stator core at time t from June to August, and it can be plotted as Figure 8 As shown. Because the core temperature does not change much, and the core material is silicon steel, its linear thermal expansion coefficient is small, so the deformation of the core is also small. It can be seen from the figure that the deformation of the core at time t is similar to the change curve of the core temperature.

[0067] Finally, based on the deformation data of the wire rod and the core at time t from June to August, the above calculation formula is used to calculate the accumulation of the relative deformation of the two from June to August over time, and the result is plotted as follows: Fig. 9 The relative deformations of the stator bars and core from June to August are 362.9498724m, 22.66709521m, and 505.0062512m respectively.

[0068] Depend on Fig. 9It can be seen that frequent changes in temperature will cause the stator wire bar and the core to produce a large deformation, which will gradually accumulate over time. The stator wire bar and the core are both important components of the generator. If the two have a large relative deformation for a long time, it will cause them to deteriorate or even fail. Therefore, it is extremely important to stipulate the normal operating range of the relative deformation of the stator wire bar and the core. If this range is exceeded, there is a greater possibility of failure. Considering that the deformation of the generator wire bar and the core will accumulate over time, and the temperature rise of the core and winding of generators of different capacities during operation is different, the first threshold and the second threshold for judging whether the stator winding and the core have a fault can be formulated according to the situation.

[0069] The performance evaluation method for the deep peak-shaving steam turbine generator stator provided in this embodiment can accurately determine whether there is a potential fault according to the existing temperature operating status information of the steam turbine generator. It has high diagnostic efficiency and is of great significance for early fault prevention, reducing economic losses and improving power system stability.

[0070] The specific implementation methods of the present application are described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be modified and improved without departing from the principles and spirit of the present application whose scope is defined by the claims and their equivalents. These modifications and improvements should also be within the scope of protection of the present application.

Claims

1. A performance evaluation method for a deep peak-shaving steam turbine generator stator, characterized in that: The performance evaluation method includes: The axial deformation of the stator wire rod is calculated according to the temperature of the stator wire rod, and the axial deformation of the stator core is calculated according to the temperature of the stator core; Calculating a relative axial deformation amount according to the axial deformation amount of the stator wire bar and the axial deformation amount of the stator core; The performance of the generator stator is determined according to the relative axial deformation amount.

2. The performance evaluation method for a deep peak-shaving steam turbine generator stator according to claim 1, characterized in that: The calculation formula of the axial deformation of the stator bar is as follows: Δl1(t)=α1*l1*[T cu (t)-T0] Where Δl1(t) is the axial deformation of the straight part of the stator bar at time t, α1 is the linear thermal expansion coefficient of the stator bar, l1 is the original length of the straight part of the bar, and T cu (t) is the temperature of the stator bar at time t during operation, and T0 is the temperature of the stator bar at the initial time.

3. The performance evaluation method for a deep peak-shaving steam turbine generator stator according to claim 2, characterized in that: The calculation formula of the axial deformation of the stator core is as follows: Where Δl2(t) is the axial deformation of the stator core length at time t, α2 is the linear thermal expansion coefficient of the stator core material, l2 is the original length of the stator core, and T fe is the stator core temperature at time t during operation, and T0 is the stator core temperature at the initial moment.

4. The performance evaluation method for a deep peak-shaving steam turbine generator stator according to claim 3 is characterized in that: The calculation formula of the relative axial deformation is: Where Δl represents the relative axial deformation.

5. The performance evaluation method for a deep peak-shaving steam turbine generator stator according to claim 1, characterized in that: The method for determining the performance of the generator stator according to the relative axial deformation comprises: When the relative axial deformation amount is greater than a first threshold value, it is determined that the stator core has reached a critical point of failure; When the relative axial deformation amount is greater than a second threshold, it is determined that the stator bar has reached a critical failure point, wherein the second threshold is greater than the first threshold.

6. The performance evaluation method for a deep peak-shaving steam turbine generator stator according to claim 1, characterized in that: The performance evaluation method further comprises: The temperature of the stator bar is obtained by the temperature sensor installed between the upper and lower windings of the stator; The temperatures of a plurality of similar measuring points are obtained according to the temperature measuring sensors installed on the stator core, and the average temperature of the plurality of similar measuring points is taken as the temperature of the stator core.

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