Causes and Countermeasures of stator water leakage

2022-08-16
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Causes and Countermeasures of stator water leakage of 100 MW generator

no.2 generator is produced by Beijing heavy duty motor factory, the model is QFS type, the active power is 100MW, and the cooling mode is water water air. It was put into operation in July 1996, and the first water leakage fault occurred in 2001. So far, there have been four water leakage faults

1 4 times of water leakage fault of No.2 generator

(1) fault shutdown time:, water leakage position: the upper coil of slot 56 at the excitation side of the generator end, but a hollow wire is leaking, which is a small crack, and it is about 25mm to the copper box with water connection and joint

(2) fault shutdown time:, water leakage position: a hollow conductor on the upper layer of the 57th slot of the generator seeps water, and it is about 20mm to the copper box with water connection and joint

(3) fault shutdown time:, water leakage position: water leakage occurs at the welding between the hollow conductor of the lower layer of the first slot at the excitation side of the generator end and the water connected copper box

(4) fault shutdown time:, the water cut-off position is the same as the third time

2 cause analysis of water leakage

(1) the hollow conductor itself has defects, and there is residual stress during processing

(2) the vibration at the end of No.2 generator has been large. In 2001, the most expert team in the vibration record of No.6 bearing (generator excitation side) was a private R & D team composed of retired experts and young and middle-aged experts. The high value of horizontal vibration reached 130 Ω, and the shaft vibration reached 260 Ω. The main reason is that the platen of No.6 bearing is loose, resulting in large vibration at the end of the generator excitation side. A fracture of the binding wire at the end of the excitation side was found during the overhaul in 2002, During the overhaul, the vibration problem was dealt with, and the foundation of No. 6 tile was re poured and reinforced, so that the vibration of No. 6 tile was reduced to qualified

(3) welding quality problems. The third leakage was caused by poor welding during manufacturing and poor process quality. The fourth leakage was caused by the previous welding without penetration. Objectively, the water leakage part is located at the welding place between the hollow conductor of the lower layer of the first slot at the excitation side of the generator end and the water connected copper box, and it is difficult to weld at the lower part of the generator

(4) the influence of the speed of load increase and decrease. Before the second fault shutdown, the connection between water leakage and load increase and decrease of No. 2 generator was tested. Under the condition of rapid load increase and decrease (above 6mw/min), the light word of water leakage was frequently sent out, while under the condition of stable and slow load increase and decrease (about n introduced by Mr. 3mw/mibakker), the light word of water leakage was not easy to send out, indicating that under the condition of rapid load change, the generator vibration and the difference between thermal expansion and cold contraction of hollow conductor and solid strand wire, Cause obvious water leakage. It can be said that the loading and unloading is stable and slow, which will alleviate the occurrence of water leakage fault to a certain extent

3 leakage prevention measures

(1) eliminate the vibration at the end of the generator, fix the end of the stator winding firmly, and make its natural vibration frequency avoid 100Hz

(2) in case of post-treatment of water leakage, the welding quality should be guaranteed, especially at the joint seal welding of hollow conductor, phosphorous silver copper welding strip should be used, which should be fully welded, and the solder should be filled

(3) the speed of loading and unloading of generator is uniform

(4) after the high resistance leak detector acts, the maintenance must find out the cause. If there is no problem with the outside and the leak detector itself, the generator shall be subject to hydraulic test to find out the leak point and deal with it as soon as possible. If the leak detector operates frequently, a specially assigned person shall be used to stop and catch the leak r=......................... Formula (10). It is strictly forbidden to exit the leak detector from operation. Strengthen the maintenance and regular inspection of the leak detection device, and install a humidity differential leak detector on No. 2 generator

(5) through several times of water leakage, we feel that we must find a more effective method to detect the hidden danger of water leakage as soon as possible than pumping water. Therefore, we try to use the method of measuring the ground potential of the insulation surface of the welding joint. After the water pressure is applied, the rated DC voltage is added to the stator winding, and the voltage on the outer surface of the welding joint of the stator winding is measured successively with a voltmeter with high internal resistance. The higher voltage may have water leakage

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