How to prevent safety accident caused by generator damage

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How to prevent safety accident caused by generator damage

1 daily management

In order to prevent damage accidents of generators, the "Technical Measures for Power Generation Anti-Accidents", "Supplementary Provisions for Technical Measures for Power Generation Anti-Accidents", " Operational Regulations for 600 MW Units" (Boundaries), and "Regulations for Electrical Maintenance" shall be strictly implemented. Provisions and key requirements are as follows:

1.1 Strengthening the supervision of insulation of generators

1.2 Strengthen the operation and maintenance management of turbine generators. In particular, the operation of the hydrogen system, the cooling water system, and the seal oil system are adjusted to monitor the temperature of the generator core and windings.

1.3 Generator Excitation System Operation

1.4 The generator protection device shall be put into operation normally, and shall be periodically tested and overhauled as required

2 aspects of operation

2.1 Prevent Stator and Rotor Insulation Damage of Generator

1) The rated hydrogen pressure of the generator is 0.4 MPa , and the amount of hydrogen leakage when operating under rated hydrogen pressure must not exceed 11 m3 /day .

2) The hydrogen purity during normal operation of the generator must be > 98% and oxygen content < 1.2% . If hydrogen purity is less than 98% , hydrogen must be supplied to make the hydrogen purity > 98% . When the hydrogen purity is reduced to 95% , the load should be immediately reduced and the hydrogen must be replaced. If the purity of hydrogen continues to drop to 90% , it should be immediately Stop the hydrogen discharge for inspection. When the hydrogen side seal oil pump is deactivated, it should be noted that the hydrogen purity is above 90% .

3) Strictly control the hydrogen humidity inside the generator shell to minimize the moisture content of hydrogen. The absolute humidity under the rated pressure should be ≤ 2 g /m3 to prevent the hydrogen humidity from being too high and the insulation level of the generator to decrease.

4) When the hydrogen pressure changes, the allowable output of the generator is determined by the temperature of the hottest point of the winding, ie, the temperature at this point must not exceed the temperature of the generator at rated operating conditions. The output of the generator with different hydrogen pressures and different power factors should be loaded according to the capacity curve. When the hydrogen pressure is too low or in the CO2 and air cooling mode is not allowed to load.

5) Reasonably adjust the sealing oil pressure of the sealing tile to prevent the leakage of hydrogen due to the unreasonable pressure of the sealing oil and the large leakage of the sealing oil into the casing, thereby causing the insulation aging of the generator. Operation hydraulic pressure difference should be 84 kPa of hydrogen, hydrogen-side hydraulic pressure difference of air 49 Kpa.

6) Reasonably control the temperature of the internal cooling water, generally 45 ~ 50 °C , the hydrogen inlet temperature is controlled at 451 °C , prevent the temperature of the stator coil from falling due to the temperature of the internal cold water too low, condensation in the generator shell, when the long-term operation At that time, the insulation level of the generator will be reduced, and in severe cases, the insulation of the generator will be corroded.

7) The inlet pressure for replenishing the stator cooling water system is 0.36 MPa , and the maximum allowable inlet temperature is 50 °C .

8) The pressure difference between the generator hydrogen pressure and the stator cooling water must be above 0.035 MPa . Alarm when the pressure difference is as low as 0.035MPa .

9) The conductivity of the outlet of the ion exchanger during normal operation is 0.1-0.4s/cm . When measuring the water conductivity> 1.5s/cm , the control room emits an alarm light plate.

10) When the stator cooling water conductivity> 2s/cm , replace the cooling water and other measures should be taken to try to reduce the conductivity to normal.

11) When the cooling water conductivity of the stator rises to 9.5s/cm , a high-conductivity alarm will be issued. The report will be reported to the leader and ready for shutdown.

12) The liquid at the bottom of the generator shell should be drained in time to monitor the accumulation of water inside the generator and to analyze the insulation of the generator based on the condition of accumulated water.

13) The maximum cold air temperature of the AC exciter and the rectifier ring should not exceed 50 °C . When the exciter is in operation, a lower cold air temperature is advantageous, but condensation must be prevented on the parts of the brushless exciter during shutdown.

3 Prevention of generator damage accidents

3.1 Disable the generator's non-excitation operation.

3.2 When the generator is running at high power, the automatic excitation regulator must be put into automatic operation. If the excitation is in the manual mode, the power factor must be controlled to run within 0.95 of the phase delay . Prevent the generator from losing step.

3.3 Generators that have not been tested in phase, are not allowed to enter the phase operation without knowing their ability to enter the phase. Generators that can be operated in phase will not be allowed to run in the case that the automatic excitation regulator is not automatic. , And in the phase-in operation, the automatic excitation regulator must have a low excitation limit function. Low excitation limit protection must be reliably invested.

3.4 During the phase-in operation, the monitoring of the generator body and operating parameters should be strengthened, and the temperature of the generator core should be overheated.

3.5 Prevention of non-full-phase operation and asymmetric operation of the generator. Strictly control the negative sequence current of the generator to prevent the generator rotor from being burned out due to excessive negative sequence current for a long time.

3.6 Strict implementation of the generator tight stop regulation, should stop the stop, beware of damage to the generator due to time delays.

Hydrogen generator system 4 prevents fire and explosion accident

4.1 During the operation of the hydrogen-cooled generator and its hydrogen system is strictly prohibited within the scope of pyrotechnics, such as the need to conduct open fire operations or maintenance tests and other work, must first detect the leakage of hydrogen, gas sampling analysis, confirm that the gas mixture ratio is within the safe range, Only after the examination and approval is approved, can the hot work ticket be under the supervision of a special person to work. If the above work requires more than 4 hours, the above-mentioned inspection and test work shall be re-entered.

4.2 It is prohibited to place flammable and explosive articles near the generator in operation and it is forbidden to lap the welding machine ground wire on the hydrogen charging pipeline.

4.3 During operation of the generator, the exhaust fume fan shall be checked for reliable operation, and shall be regularly sampled from the outlet of the fume extractor and the main tank to monitor whether the hydrogen content exceeds the specified value ( 2% ). If it exceeds, the cause shall be ascertained and eliminated.

4.4 seal pump work, standby switch should be normal, and do a regular test record

4.5 If the operator finds that the hydrogen supplementation is abnormally increased, the relevant personnel should be promptly contacted to find out the missing point and eliminate it in time.

4.6 The purity of hydrogen in the machine should be kept above 98% and the oxygen content should be less than 1.2% . When these limits are exceeded, hydrogen should be drained and then filled with pure hydrogen until the hydrogen purity is acceptable

 

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