Fault Analysis and Prevention of Stator Core of Large Turbogenerator

In recent years, Hebei Southern Power Grid will be abbreviated as the Generator Stator Core of the Hebei South Network, and the phenomenon of frequent occurrence of vibration and noise due to the Stator Core core breaking and the looseness of the stator core during operation will occur. Generator core fault vibration and noise generation are more complicated. It involves many factors such as generator design, manufacture and operation, electromagnetic force, mechanical force and heat, which brings hidden danger to the safe operation of generators. One of the crew was forced to stop running. In this case, it is necessary to pay enough attention to this question. 1 In recent years, the occurrence of core accidents and noise increase in the operation of the Hebei South Network generator has been evaluated. Example 1 The generator was manufactured in May 1988 in the Dongfang Electric Machinery Factory. For water hydrogen, the rated power factor is 0.85, and the stator rated voltage of 15.751 is constantly running and the machine noise is sudden and large. At that time, Gong Gongyu. 200 reactive power. For 53 people, the electrical parameters and temperature of each part of the generator are normal, and the lifting and regenerative power has no effect on the noise level. The impact of adjusting the generator card to pay attention to the noise is not as heavy as the load reduction 1601; after that, it returns to normal. The generator vibration and noise are measured during no-load step-up of the generator. When the stator voltage is 131, the frequency-doubled vibration is abrupt and large. The frequency-doubled vibration occurs at 161, and the vibration at each measurement point decreases after step-down, and the noise is not obvious. Variety. Shutdown inspection found. Locating Nuts at Both Ends of the Generator Loose Nuts There is an empty sound at 0 o'clock on the steam side, and the nut is completely loose at the 3 o'clock position. The nut at position 1 on the excitation side has an empty sound; the back of the iron core 1 is loose.

1.2 Cases of a plant to turn on the machine for the Harbin Electric Machinery Factory to produce fewer places, the cooling method is water ceremony, the rated capacity of 3 Jiaohe in the travel of the sound anomaly, stop inspection and found that the stator excitation side slot 34 and 35 slots Between the 35th and 36th sections of the iron core section 1 Between the first section of the core 1 and the 2nd section, the first section iron core and the like are severely overheated and the teeth are burned. The 35th and 36th end iron core parts can be shaken by hand. The upper layer of coil 23536 slot rod slot insulation wear due to shaking the core, 36 slot bar wear is particularly serious, the active core will 5.5 line insulation wear up to 5 deep, with a special month instrument wedge wedge Situation, found that the wedge wedge is generally loose, according to the manufacturer's requirements, the value should be between 0.20.5mm, the actual measured value up to lJ with water The plant and machine with the manufacturer's eyebrow model of the unit in normal operation with a work load of 300 added And when the internal cold water temperature rises from 25 to 36, the noise and vibration increase, the noise characteristics are low-frequency noise, the vibration amplitude of the base is from 0.008 to 00, when the water temperature is controlled at 3 left and the load is below 30 1 Jia The generator's noise and vibration are basically normal.

After the overhaul of the unit was dismantled, the iron core was found to have 4 hot spots in the iron loss test, and the stator excitation side lead splices 8 were loosened.

1.3 cases of a factory machine are Harbin Electric Factory production volume tolerance 300 with. The cooling method is hydroquinone hydrogen. During the operation, the stator grounding signal was issued twice. After being forced to stop, it was found that the stator steel wire insulation was broken at the first stage iron core and the saw was broken. Side iron core ladder; There are many places where the oscillating steel can be shaken, 2 Iron core overheating analysis in operation The stator core of modern large-scale generators is usually made of high-permeability and low-loss cold rolled non-oriented silicon steel with a degree of orientation of 0.35, 0.5. The sheets are laminated and the silicon steel sheet is coated with insulating paint. The iron core section formed by stacking 20 pieces of fan-shaped silicon steel sheets is mounted on the positioning ribs with 12 cuboids and 1 machine-shaped fan-shaped pieces, so that all the fan-shaped pieces are electrically connected with each other through the positioning ribs themselves. If the insulation of the iron chip is damaged or becomes low. During the operation, the generators form a closed circuit of current. The loss caused by this eddy current is related to the loop resistance. When the insulation damage of Guisteel is severe, the current may reach a large value, causing the temperature of the core to increase or even dissolve. Serious accident. The cause of short-circuit caused by the insulation damage between the iron chips The manufacturer used the core fan-shaped edge-effect iron core to loosen the stator vibration and inter-chip insulation damage before the stator windings went offline; the pressure applied during press-fitting was too large. 2 Rivers, 3 Insulation damage between plates; operating voltage is higher than 1.1 times the rated voltage for a long time; hard foreign objects suddenly appear in the generator for some reason, and the iron core is impacted under the action of wind pressure and rotor rotation, etc. .

3 Causes of vibration and loosening of the generator core fault 3.1 Quality of manufacture of the iron core In the operation of the generator, the iron core will be subjected to various forces, in which the radial magnetic force waves between the rotor and the stator form an alternating magnetic pull and The core of the iron core will be greatly relieved if the iron core is loaded with looser force waves, which will cause noise and tooth breakage of the core and the fan-shaped pieces.

The interaction of the magnetic field of the stator and rotor causes the stator core coil to be subjected to a rotational force wave, which changes position with the rotation of the magnetic field. For a 2-pole stealth generator, when the rotating magnetic field rotates around, magnetic tension and electromagnetic force The vibration changes 2 times, which is 2 times the power frequency. Therefore, during the normal operation of the generator, iron core bars and other parts will be subjected to a rotational force wave that is twice the generator frequency.

Affected by this force, the iron core bar may vibrate, and the iron core produced by the electromagnetic force casts the pharynx into an ellipse and pharynx. Therefore, during the production process, the self-resonance frequency of the iron core bar should be kept away from 100, avoiding resonance with 10 out of the electromagnetic excitation frequency and causing severe vibration and noise.

When the press-fit tightness of the iron core becomes loose, the effect of the force wave will generate vibration and friction, which will reduce the insulation between the sheets and easily form a closed-loop eddy current. In this case, the rust may be completely dry. The rust on the vibrating laminations is often very stable. After the rusted parts are painted with insulating paint, the rust will not stop because the insulating paint applied on this part will soon be destroyed again and the individual cores will loosen and become loose. The main reason is that the thickness of the sector is particularly uneven. Stator positioning ribs are not properly installed. Ventilation channel is not installed correctly. Iron cores are stacked in the factory. Trial is poor. The stator shell is vibrating and the nut's buckle is not reliable. It can be seen from the front fault phenomenon that the screw nut of the tight screw is screwed out.

The most frequent throttling becomes loose in the tooth zone of the production side, which causes damage to the individual fan fry. Keep the core loose.

3.2 The effect of temperature changes during operation The daily load of the engine is not uniform, and the active load changes more than people, and the reactive power load also has a great change. These will cause the core temperature to change. According to relevant data, the change in active load of 200,130 lbs. of euphoric load changes 020 will cause changes in core temperature of up to 2535. Some generator cadastral peaks will be frequently started and stopped, so that the temperature range of the generator stator core can reach 50 70. The temperature change of the stator core during the operation of the generator causes the tight clamping force between the wafers to change elastically. It will be repeated for a long time. The iron core will periodically heat and shrink, and the core will loosen easily. Forces produce vibration and noise.

The generator runs during low load phases such as midnight on holidays or when the power factor approaches unity. The axial magnetic flux leakage in the stator core at the end of the stator side is large, which can cause the core temperature of the side section to rise. There is only one vent channel support between the first core of the machine and the width of the press finger is much narrower than that of the core. The side core opens several trapezoidal grooves, and the core can't be guaranteed when the bottom stack is installed. Uniform distribution of armor pressure, under the influence of electromagnetic force and temperature change of the iron core at the side section, can easily cause the vibration of the laminated sheet, resulting in the fracture of the ferrous steel sheet at the edge of the teeth, and the up and down motion of the iron core section, resulting in the insulation of the fixed 1 winding. Breaking and grounding, loosening of the 4 iron cores and handling of the noise The handling of the whole or partial loosening of the iron core of the generator is relatively complicated, and it needs to be concretely solved under the participation of the manufacturer according to the specific circumstances. It should be noted that it is generally not allowed to press the iron compact core with compact ceramics, as this method may damage the winding insulation of the household and this method can only compress the short segment iron chips.

When designing and manufacturing generator iron cores, they generally consider schemes and processes to avoid 7 electromagnetic excitation frequencies. The modal frequency of the iron core is less than 100 iron cores whose oscillating mode is elliptical. At this time, the positioning ribs have a great influence on the vibration and noise of the generator. The frequent and effective method of changing the core's natural frequency is Adjust the stiffness structure of the positioning ribs between the stator core and the casing. Turn to page 28 to make it have two groups of end networks inside. The impedance characteristics of the end network are respectively matched with the impedance of the local function end of the ground end. Avoid the impedance mismatch due to the local function and the use of the ground tone to share the interface, and the remote device caused by the lower level is dead. Modem measurement remote code transfer to the key control, corresponding to 0 or 1 number of milk rate sine wave voltage. With the change of the digital equal-amplitude FM signal, after amplification by the amplifier, it has a constant transmission level. The bandpass filter then filters out the higher harmonics and noise, and then sends it to the attenuator to adjust the output signal to The size of the transmission level is most matched with the line matching transformer for impedance conversion and cooperates with various transmission channels. The number of pages and the number of pages are connected. This requires the operating unit and the manufacturer to complete the plan.

Loosening of the end iron core and greater vibration are common.

In order to enhance the insulation between the sheets and reduce the eddy current, a method of inserting a 0.2 mm thick epoxy glass cloth sheet between the sheets is generally used for processing. Epoxy glass cloth and iron chip spacers or two carefully inserted according to the degree of loose core, determine the number of inserted pieces and the depth of each piece inserted.

According to experience, the maximum insertion depth is about 100 without removing the bar. To do the iron loss test, pay for one, the core of the tooth is still very hot, can insert the epoxy glass cloth plate deeper. If it is more difficult to continue inserting at a deeper level, it is necessary to take out the bar to facilitate the insertion of the insert. For small gaps, the epoxy chip can not be inserted into the epoxy glass cloth, narrow and thin special tools can be used to open the teeth, in the open gap infused with the same brand of insulating paint.

5 Preventive measures 5.1 Monitoring and monitoring during operation and overhaul The operating personnel should pay attention to changes in noise during the inspection of the generator. The loose core will increase the generator noise. If noise is found to be abnormal, people should find out the reasons. At the time when the machine is scheduled to be shut down, repairs can sometimes be performed by adjusting the generator operating parameters such as 旮 无 无 氢 氢 氢 氢 氢 氢 氢 温 温 温 温 温 发电机 发电机 在 在To examine the tightness of the stator core in detail. The loose core can be processed by wedge-insulated wedges. After the wedges are wedged, epoxy glue is applied to fix the wedges. The signal is transmitted to the receiver for the load. The filter attenuator and the line transformer in the modulation circuit are all end-to-end networks. The output of the end-to-end network is directly connected to the input of the other end of the network. To achieve a matching cascade, the characteristic impedances at both ends of the connection must be equalized. 4 Inspection and consolidation of the measures' implementation effects In October 2000, the Xuying Zhaotong Station was inspected for its effects. It was found that the availability rate of the telecontrol equipment after the transformation was significantly increased to 100, effectively ensuring that the dispatcher correctly mastered the station port. , raised the efficiency of the dispatcher. The expected value was achieved and the transformation was successful. In addition, corresponding consolidation measures have been formulated to formally incorporate the results of the transformation into the routine maintenance of automation to ensure the reliability of its operation. In the course of operation and maintenance, various types of failures of the telecontrol equipment are verified. Discover + more than enough to improve. In order to improve the measures and improve the generators that are relatively large, high-powered, or operate in phase, special attention should be paid to checking the presence or absence of loosening of the positioning tendons. Before this, Hebei Nanfang 200 Fantun units had encountered this type of loosening of the positioning ribs nut to use a special wrench to tighten and relock the locking piece.

5.2300倨婪5. 缁 缁 笮奘 笮奘 笮奘 笮奘 笮奘 缁 疚 疚 疚 疚 疚 疚 疚 疚 疚 疚 疚 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北 河北. Core temperature rise tests should be done to determine the state of the insulation between the plates. In order to ensure the magnetic flux density of the iron loss test, according to experience, it is best to select 61 grade grades in the inspection field. The magnetic flux density is 1.4 D. The duration is 45. After the start of the test, the thermal imager should be used to check all the stators. Teeth, find the higher temperature rise, and then use infrared thermometers for special surveillance. The maximum temperature rise of the tooth should not exceed 25, and the temperature difference between the most teeth + should exceed 5.

For excessive teeth, it should be combined with major repairs to carry out the necessary treatment.

5.3 The transport hall of the generator should be as reasonable as possible The change of the temperature of the large turbine generator hall will not only affect the service life of the fixed coil insulated rotor parts, but also affect the tightness of the iron core. Therefore, it is necessary to keep the generator load continuously stable during the operation of the generator. For the peak load adjustment of the grid, the burden of small units should be arranged as much as possible. In addition, due to the high rate of force or the turbogenerator running in phase, due to the large magnetic leakage at the end, the poorer generators at the end cores should be arranged to operate as little as possible. For generators with more load changes and more phase-in operation during operation, attention should be paid to changes in generator noise. Attention should be paid to checking the condition of the core during maintenance.