Under the correct use and maintenance of the general turbogenerator, it is not easy to fail, but if the use and maintenance of improper, poor environment, disrepair, will also cause failure, the common causes of failure should be analyzed as follows:
1) The output voltage of generator is unstable
1.1) AVR control (normal when manual control) refer to AVR manual;
1.2) Manual or automatic control, it may be due to other mechanical reasons in the system or the prime mover speed is unstable;
2) The output voltage is too high, check whether the voltage reading meets the AVR requirements, refer to the AVR manual.
3) Generator excitation failure
3.1) If the excitation is normal under manual control and abnormal under AVR control, refer to the AVR manual and check the relevant connections;
3.2) When there is no excitation current under manual or automatic control, check the circuit between AC exciter and rotating rectifier and AVR, and check whether the lead of rotor coil is open;
4) The vibration of the generator is large
4.1) Electrical: short circuit or grounding of rotor coil between turns, uneven air gap, deformation and displacement of rotor coil, damage and loosening of insulation of stator core;
4.2) Mechanical aspects: the rotor is unbalanced, the center of the generator is not properly matched with the turbine, the gap between the bushing and the shaft is not uniform, the oil is short or the bearing fixing screw is loose, the foundation is not firm, etc.
5) The generator rotor moves axially in series
5.1) The rotor position is tilted during generator installation;
5.2) When the generator is running, the center of the stator and the center of the rotor do not coincide.
6) Damage of stator core
6.1) When the stator coil is broken down, the silicon steel sheet will be burned;
6.2) Loose iron core due to poor manufacturing or rusting.
7) Fault of stator coil
7.1) The loosening of slot wedge or end pad causes insulation wear of winding;
7.2) Insulation aging caused by overheating of stator winding due to excessive load or other reasons;
7.3) Mechanical damage of winding insulation caused by sudden short circuit;
7.4) Breakdown of winding insulation caused by overvoltage;
7.5) Insulation damage caused by stator core relaxation;
7.6) Poor welding of stator coil joint.
8) Fault of rotor coil
8.1) Insulation resistance drop due to dust accumulation at the end of rotor coil;
8.2) The sudden unloading of the generator causes excessive speed of the generator set, resulting in the increase of excitation voltage, which exceeds the voltage of the generator rotor and causes insulation breakdown;
8.3) Short circuit between turns of rotor coil or unstable grounding;
8.4) Local overheating of the rotor due to unbalanced load or asynchronous operation;
8.5) Excessive excitation current caused by generator overload and overheating;
8.6) Bad contact of coil joint causes overheating and insulation aging.
9) Bearing failure
9.1) Due to poor insulation between the bearing bush and the shaft, the shaft current passes through the bearing, causing overheating and corrosion of the bearing;
9.2) Bearing overheating due to lack of oil;
9.3) Bearing oil leakage due to improper oil adjustment and poor sealing;
9.4) The bearing center is not aligned, and the bearing bush is scraped.
10) The cooler is faulty
10.1) Cooler pipeline blockage caused by cooling water fouling;
10.2) Water leakage and pipe rupture due to mechanical damage, corrosion and vibration of the pipe;
10.3) Because the cooling water temperature is too low or because the external inflow of air with too much humidity, resulting in condensation on the surface of the cooler;
10.4) Because the inlet temperature of the cooler is too high, the inlet water amount is too small, or the cold and hot air channels are short circuit, the outlet air temperature of the cooler is too high;
10.5) Gaskets between the water chamber and the tube plate are aged and not tight.
11) Overheating of the generator
11.1) Overload operation of the generator;
11.2) Short circuit of core or winding;
11.3) Failure of air cooler or ventilation system.
