The causes of vibration in steam turbine generator sets are often complex and have many factors. For example, some vibrations are not only related to factors such as mass imbalance and misalignment of rotating machinery itself, but also to factors such as electrical, thermal expansion, and fluid during operation. Some are also related to structural stiffness and installation quality. Therefore, it is necessary to conduct some relevant vibration tests to determine the cause of the vibration.

对于转速的升降速振动试验

Vibration test for speed increase and decrease

该实验的目的是确定机组实际的轴系临界转速和相位的振动值。由于制造厂商提供的都是计算临界转速，在计算中有关参数的模拟可能与实际机组本身和其安装条件有些偏差，故计算结果和实际值会有一定的误差。机组的临界转速应以实测结果为准。根据过临界转速时的振动值大小，也可以判断转子各阶振型的平衡状况。

The purpose of this experiment is to determine the actual critical speed and phase vibration values of the shaft system of the unit. Due to the fact that manufacturers only provide critical speed calculations, the simulation of relevant parameters in the calculation may deviate from the actual unit itself and its installation conditions, resulting in certain errors between the calculation results and the actual values. The critical speed of the unit should be based on the measured results. Based on the magnitude of the vibration value at the critical speed, the balance status of each vibration mode of the rotor can also be determined.

该实验的另一个目的是可以确定转子是否发生热弯曲。如果冷态下机组启动过程中过临界转速时的振动值不大，但在带负荷运行一段时间后快速降负荷并解列打闸停机过程中临界转速下振动增大许多时，则可以作为判断转子产生了热弯曲的因素之一。

Another purpose of this experiment is to determine whether the rotor has undergone thermal bending. If the vibration value at the critical speed during the cold start process of the unit is not significant, but after running under load for a period of time, the load is quickly reduced and the vibration at the critical speed increases significantly during the trip and shutdown process, it can be used as one of the factors that determine the thermal bending of the rotor.

发电机励磁电流试验

Generator excitation current test

发电机励磁电流试验的目的是判断机组振动原因，是来自电磁方面还是机械方面，电磁方面的原因可分为两种：

The purpose of generator excitation current test is to determine the cause of unit vibration, whether it comes from electromagnetic or mechanical aspects. The electromagnetic reasons can be divided into two types:

一是，由于纯电磁激振力引起的振动（如发电机转子线圈匝间短路以及转子与定子间的空气不均匀引起的激振力）；

One is the vibration caused by pure electromagnetic excitation force (such as the excitation force caused by the inter turn short circuit of the generator rotor coil and the uneven air between the rotor and stator);

二是，由于电方面的原因引起的，发电机受热不均的热弯曲而引起的振动。

The second is the vibration caused by uneven thermal bending of the generator due to electrical reasons.

后者由于转子热惯性，其振动值的增大在时间上较励磁变化滞后，通常只有在发电机转子励磁电流有较大幅度变化时，振动才有明显改变。励磁电流试验是在机组带上一定负荷时，保持该负荷不变而增大发电机转子励磁电流（降低功率因素）的条件下进行的，发电机转子励磁电流的变化范围是，以不超过其额定值为限。通常随着励磁电流增加，振动值也随之增大。如试验曲线呈光滑上升形状，则说明振动直接与励磁电流有关，是纯电气原因造成的。如振幅增加呈阶梯形，即振动不立即随励磁电流的增加而增大，而是到一定时间阶跃增加，则振动是因转子热弯曲变形增大引起的，通常的原因是转子冷却通风道开孔不正确或灰尘、杂物的不均匀堵塞、线圈膨胀受阻等。

Due to the thermal inertia of the rotor, the increase of its vibration value lags behind the excitation change in time. Usually, only when there is a significant change in the excitation current of the generator rotor, does the vibration change significantly. The excitation current test is conducted under the condition of increasing the excitation current of the generator rotor (reducing power factor) while maintaining a certain load on the unit. The variation range of the excitation current of the generator rotor is limited to its rated value. Usually, as the excitation current increases, the vibration value also increases. If the test curve shows a smooth rising shape, it indicates that the vibration is directly related to the excitation current and is caused solely by electrical reasons. If the amplitude increases in a stepped shape, that is, the vibration does not immediately increase with the increase of excitation current, but increases step by step at a certain time, then the vibration is caused by the increase in thermal bending deformation of the rotor. The usual reasons are incorrect opening of the rotor cooling ventilation duct, uneven blockage of dust and debris, and obstruction of coil expansion.

并网前后振动变化。如果并网前后振动变化较大，说明转子上存在不平衡电磁力的作用。例如，电动机出现故障后，可以采用“断电速查”法，根据断电瞬间振动的变化情况判断电气缺陷情况。

Vibration changes before and after grid connection. If the vibration changes significantly before and after grid connection, it indicates the presence of unbalanced electromagnetic force on the rotor. For example, after a motor malfunction occurs, the "power outage quick check" method can be used to determine the electrical defect situation based on the changes in vibration at the moment of power outage.

励磁电流变化后，振动随即变化，两者之间没有滞后。这种现象说明振动主要是由于电气缺陷引起的。发电机转子线圈出现匝间短路后，振动变化将以基频为主。发电机转子与静子间的空气间隙不均匀，将会诱发较大的二倍频振动，转子振动增大的同时，静子振动一般也会增大。

After the excitation current changes, the vibration changes immediately, and there is no lag between the two. This phenomenon indicates that vibration is mainly caused by electrical defects. After the inter turn short circuit occurs in the generator rotor coil, the vibration change will be mainly based on the fundamental frequency. The uneven air gap between the generator rotor and stator will induce significant second harmonic vibration. As the rotor vibration increases, the stator vibration generally also increases.

励磁电流变化后，振动逐渐变化，一段时间后才能稳定下来，振动变化滞后于励磁电流变化。这种现象说明振动主要是由于热变形引起的。可能的原因有：匝间短路诱发的转子部件非对称热变形，通风孔堵塞、冷却水量不均匀等诱发的转子冷却不均匀以及部件松动或膨胀受阻等。

After the excitation current changes, the vibration gradually changes and stabilizes after a period of time. The vibration changes lag behind the excitation current changes. This phenomenon indicates that vibration is mainly caused by thermal deformation. Possible reasons include asymmetric thermal deformation of rotor components caused by inter turn short circuits, uneven cooling of the rotor caused by blocked ventilation holes, uneven cooling water volume, and looseness or expansion of components.

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发电机冷却介质温度试验

Generator cooling medium temperature test

当发电机转轴存在不对称冷却时，发电机转子会发生热弯曲，引起振动增大。因此，通过改变冷却介质的温度，可以判断有无不对称冷却。对于水冷发电机可采用改变冷却水温试验，而对于氢冷发电机可采用改变冷却氢温试验，观察其变化对振动发展的影响。双流式氢冷系统，可以单独改变发电机某一端氢冷器的出口氢温，有助于判断不对称冷却发生在转子的哪一端。通常在存在不对称冷却故障时，冷却介质温度越高，振动越小。

When there is asymmetric cooling of the generator shaft, the generator rotor will undergo thermal bending, causing increased vibration. Therefore, by changing the temperature of the cooling medium, it is possible to determine whether there is asymmetric cooling. For water-cooled generators, changing the cooling water temperature test can be used, while for hydrogen cooled generators, changing the cooling hydrogen temperature test can be used to observe the impact of its changes on vibration development. The dual flow hydrogen cooling system can independently change the outlet hydrogen temperature of the hydrogen cooler at one end of the generator, which helps to determine which end of the rotor asymmetric cooling occurs. Usually, in the presence of asymmetric cooling faults, the higher the temperature of the cooling medium, the smaller the vibration.

负荷试验

Load test

负荷改变后，流量、温度、压力、联轴器传递扭矩、汽流激振力、汽缸膨胀、轴承标高等都会发生变化，从而有可能影响机组振动。负荷试验可以在空负荷、中间负荷和满负荷三种状态下进行。负荷改变后，应立即测量振动。然后，保持负荷不变，稳定一段时间或等振动不变后再次测取振动值。负荷变化后，一般需要稳定30分钟以上。

After the load changes, the flow rate, temperature, pressure, torque transmitted by the coupling, steam flow excitation force, cylinder expansion, bearing elevation, etc. will all change, which may affect the vibration of the unit. The load test can be conducted under three states: no-load, intermediate load, and full load. After the load changes, the vibration should be measured immediately. Then, keep the load constant, stabilize for a period of time, or measure the vibration value again after the vibration remains unchanged. After a load change, it usually needs to stabilize for more than 30 minutes.

负荷试验的目的是判断机组负荷变化过程中，汽轮机的机械状态和热状态的变化对振动的影响。当机组负荷变化时，一方面汽轮机经联轴节传递到发电机的扭矩立即会发生变化，如果联轴节有缺陷，则机组的振动状态也会立即发生变化。另一方面，因流过汽轮机的蒸汽流量变化，会引起汽缸内蒸汽压力和温度分布的变化，也即汽轮机汽缸、转子和轴承座的热膨胀要相应改变。如果此时汽缸出现不均匀变形而使转子不正，导致轴承不能正常工作或汽缸滑销系统卡涩等缺陷，机组振动就要发生变化。由于热惯性，后者引起的振动变化在时间上要比负荷的改变滞后得多。若试验结果表明，振动随负荷的增大立即增大，则说明振动与传递的扭矩有关，一般是联轴节有缺陷或齿牙之间负荷不均等原因造成的。负荷试验时负荷的增加应在运行规程允许的范围内进行。试验时应保持真空等参数不变。

The purpose of the load test is to determine the impact of changes in the mechanical and thermal states of the steam turbine on vibration during the load change process of the unit. When the load of the unit changes, on the one hand, the torque transmitted by the turbine through the coupling to the generator will immediately change. If the coupling is defective, the vibration state of the unit will also change immediately. On the other hand, changes in steam flow through the turbine can cause changes in steam pressure and temperature distribution inside the cylinder, which means that the thermal expansion of the turbine cylinder, rotor, and bearing seat needs to be correspondingly changed. If the cylinder undergoes uneven deformation at this time, causing the rotor center to be misaligned, resulting in defects such as bearing failure or jamming of the cylinder sliding pin system, the vibration of the unit will change. Due to thermal inertia, the vibration changes caused by the latter are much delayed in time compared to the changes in load. If the test results indicate that the vibration increases immediately with the increase of load, it indicates that the vibration is related to the transmitted torque, usually caused by defects in the coupling or uneven load between teeth. The increase in load during load testing should be carried out within the allowable range of operating regulations. During the test, parameters such as vacuum should be kept constant.

负荷改变后振动迅速改变，振动变化与负荷变化之间没有滞后。

After the load changes, the vibration changes rapidly, and there is no lag between the vibration changes and the load changes.

有的机组并网或解列时，振动也会发生较大变化。这种现象说明振动与转子热变形无关。主要是由于变负荷过程中，作用在转子上的力或力矩发生了变化，导致转子上的激振力发生了变化。激振力改变后，振动随即改变。

When some units are connected to the grid or disconnected, the vibration will also undergo significant changes. This phenomenon indicates that vibration is not related to the thermal deformation of the rotor. Mainly due to changes in the force or torque acting on the rotor during the variable load process, resulting in changes in the excitation force on the rotor. After the excitation force changes, the vibration immediately changes.

齿式联轴器磨损后间隙变大，机组升负荷过程中可能会因传递扭矩的变化导致齿套偏向一侧而产生不平衡振动。负荷变化、传递扭矩变化、齿套偏移、不平衡力变化、振动变化五者之间几乎是同步的。

After the wear of the gear coupling, the gap increases, and during the load increase process of the unit, there may be unbalanced vibration caused by the deviation of the gear sleeve to one side due to changes in torque transmission. The changes in load, transmitted torque, gear sleeve offset, unbalanced force, and vibration are almost synchronous.

加负荷过程中，由于蒸汽流量的增大，汽流激振力越来越大。对于稳定性较差的机组，当汽流力增大到一定程度后，会造成机组失稳。此时，振动也会随负荷的增加而突然增加。

During the loading process, due to the increase in steam flow rate, the steam flow excitation force becomes greater and greater. For units with poor stability, when the steam flow force increases to a certain extent, it will cause the unit to lose stability. At this point, the vibration will also suddenly increase with the increase of load.

有些机组带负荷过程中，由于传递扭矩和部分进汽度的变化，转轴在轴瓦内的位置会发生一定变化。如果轴承内更小油膜间隙过小，将会导致转轴与乌金之间的轻微摩擦和不稳定振动。这种振动将随负荷的增加而快速增加。

During the loading process of some units, the position of the shaft inside the bearing pad may undergo certain changes due to changes in transmitted torque and partial steam admission. If the minimum oil film clearance inside the bearing is too small, it will cause slight friction and unstable vibration between the shaft and the black metal. This vibration will rapidly increase with the increase of load.

负荷改变初期振动变化较小，一段时间后振动逐渐变化，振动变化滞后于负荷变化。

The initial vibration change during the load change is relatively small, but after a period of time, the vibration gradually changes, and the vibration change lags behind the load change.

这种现象说明振动与膨胀不畅或热变形等因素有关。负荷改变后，汽缸及转子内部温度场发生了变化，机组有可能因此而产生膨胀不畅或热变形故障。前者改变了支承刚度，后者改变了转子上的激振力，都会导致振动的变化。由于温度变化以及由此引起的热变形和膨胀等都需要时间，因此出现这类故障后，振动变化大多滞后于负荷变化。

This phenomenon indicates that vibration is related to factors such as poor expansion or thermal deformation. After the load changes, the temperature field inside the cylinder and rotor changes, which may result in poor expansion or thermal deformation faults in the unit. The former changes the support stiffness, while the latter changes the excitation force on the rotor, both of which can lead to changes in vibration. Due to temperature changes and the resulting thermal deformation and expansion, which require time, vibration changes often lag behind load changes after such faults occur.

检查机组膨胀是否正常，可根据汽缸两侧膨胀指示器或自行架设百分表来分析。如果两侧指示相同，但数值偏小，说明汽缸膨胀不畅；如果两侧指示值差异较大，说明汽缸存在跑偏。汽缸膨胀不畅或跑偏主要是由于汽缸及所属管道较重、汽缸受管道约束力较大、轴承座与台板之间缺少润滑或润滑油脂干枯、汽缸刚性不足等因素所引起的。这时应力求减少汽缸膨胀阻力和管道约束力，增强汽缸刚度，延长暖机时间。

Check whether the expansion of the unit is normal, and analyze it based on the expansion indicators on both sides of the cylinder or by setting up a dial indicator on your own. If the indications on both sides are the same, but the values are too small, it indicates that the cylinder is not expanding smoothly; If there is a significant difference in the indicated values on both sides, it indicates that the cylinder has deviated. The poor expansion or deviation of the cylinder is mainly caused by factors such as the cylinder and its associated pipeline being heavy, the cylinder being heavily constrained by the pipeline, the lack of lubrication or dry lubricating grease between the bearing seat and the bedplate, and insufficient rigidity of the cylinder. At this point, efforts should be made to reduce cylinder expansion resistance and pipeline restraint, enhance cylinder stiffness, and extend warm-up time.

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变化真空试验

Variable vacuum test

大型汽轮机低压转子轴承通常与排汽缸连成一个整体。凝汽器内建立真空时，在大气压力作用下，排汽缸和位于其上的轴承座会下沉。真空变化的过程中，排汽缸温度也会发生变化，这些因素都会影响振动。真空试验的目的在于判别机组振动与真空及排汽温度之间的关系，也可用于判断汽缸底部与台板之间的接触状态。

The low-pressure rotor bearings of large steam turbines are usually connected to the exhaust cylinder as a whole. When a vacuum is established in the condenser, the exhaust cylinder and the bearing seat located on it will sink under the action of atmospheric pressure. During the process of vacuum change, the temperature of the exhaust cylinder will also change, and these factors will affect vibration. The purpose of vacuum testing is to distinguish the relationship between unit vibration, vacuum, and exhaust temperature, and can also be used to determine the contact state between the bottom of the cylinder and the bedplate.

真空试验通常是在较低负荷下进行，这时真空变化范围可以大些。真空变化可以通过改变凝汽器循环水量来完成。真空改变后，应立即测取振动值，稳定半小时后再测一次振动。

Vacuum tests are usually conducted at lower loads, where the range of vacuum changes can be larger. The vacuum change can be achieved by changing the circulating water volume of the condenser. After the vacuum changes, the vibration value should be measured immediately, and after stabilizing for half an hour, the vibration should be measured again.

振动随真空的变化而迅速变化

Vibration rapidly changes with changes in vacuum

这种情况多出现在排汽口与凝汽器采用弹性连接的机组上。主要原因有，排汽缸刚度较差、轴承座标高变化影响对中偏差；真空变化过程中，低压缸动静部分间隙变化较大并导致了摩擦；排汽缸底部与台板之间接触不好。真空变化过程中因排汽缸位置变化，导致排汽缸底部与台板之间出现松动和支承系统刚度降低。

This situation often occurs in units where the exhaust port and condenser are elastically connected. The main reasons are that the stiffness of the exhaust cylinder is poor, and changes in the elevation of the bearing seat affect the alignment deviation; During the vacuum change process, the gap between the dynamic and static parts of the low-pressure cylinder changes significantly, leading to friction; Poor contact between the bottom of the exhaust cylinder and the bedplate. During the vacuum change process, due to changes in the position of the exhaust cylinder, there is looseness between the bottom of the exhaust cylinder and the bedplate, and the stiffness of the support system decreases.

振动变化滞后于真空变化

Vibration changes lag behind vacuum changes

振动变化滞后于真空变化，表明振动与热状态有关，这是因为真空变化的过程中，排汽缸温度也发生了变化。这种情况多发生在排汽口与凝汽器采用刚性连接、且排汽部分刚度又较好的机组上。

The vibration change lags behind the vacuum change, indicating that the vibration is related to the thermal state. This is because during the process of vacuum change, the temperature of the exhaust cylinder also changes. This situation often occurs in units where the exhaust port and condenser are rigidly connected, and the exhaust part has good stiffness.

轴承润滑油试验

Bearing lubricating oil test

轴承工作状况对于旋转机械安全运行至关重要。轴承间隙过大、供油不足、油温不当、载荷过重或过轻等都会使轴承发生故障。改变轴承润滑油温和压力，也就改变了轴承工作状态。通过该试验，可以分析轴承工作状况及其对振动的影响。

The working condition of bearings is crucial for the safe operation of rotating machinery. Excessive bearing clearance, insufficient oil supply, improper oil temperature, heavy or light load can all cause bearing failure. Changing the temperature and pressure of the bearing lubricating oil also changes the working state of the bearing. Through this experiment, the working condition of the bearing and its impact on vibration can be analyzed.

润滑油压试验时，可以先将油压升高20～40kPa，观察振动是否因轴承供油量的增大而发生变化。如果振动是由于轴承供油不足而引起的，那么供油压力提高后，振动幅值将明显变小。

During the lubrication oil pressure test, the oil pressure can be increased by 20-40kPa to observe whether the vibration changes due to the increase in bearing oil supply. If the vibration is caused by insufficient oil supply to the bearing, the amplitude of the vibration will significantly decrease as the oil supply pressure increases.

油温试验可以在高和低两种状态下进行。油温改变后，需要立即测量振动。稳定30min后再次测量振动。油温降低过程中，处于稳定性边缘的轴承有可能发生油膜振荡，振动突增。试验中一旦出现这种趋势，应立即停止试验。

The oil temperature test can be conducted in both high and low states. After the oil temperature changes, it is necessary to immediately measure the vibration. Measure the vibration again after stabilizing for 30 minutes. During the process of decreasing oil temperature, bearings at the edge of stability may experience oil film oscillation and sudden increase in vibration. Once this trend occurs during the experiment, the experiment should be stopped immediately.

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