Analysis on Energy-saving Operation Technology of Generator

1. Harm caused by too high or too low power factor during generator operation

The excessively high rated power factor of the generator actually refers to the power factor value when the generator is operated at the same time at the rated active power and the rated apparent power (usually in the hysteresis mode). For the same rated active power unit, if The lower the rated power factor, the higher the reactive power capability during operation, and the higher the rated current of the unit, which increases the cost.

Generally, the rated power factor of the generator is about 0.9.

In the generator operation, theoretically speaking, under the same terminal voltage, if the higher the power factor is under the same active output, the less reactive power is generated, and the lower the generator potential is. The steady level of static operation drops.

During the operation of the generator, if the power factor is to be reduced below the rated value, the active power output must be reduced so that the stator and rotor currents do not exceed the limit, which is neither economical nor safe. This mode of operation often occurs when an accident occurs in the system and the reactive power shortage is more serious, and the generator is required to reduce active power and increase reactive power.

2. The relationship between generator stator cooling water system and generator economic operation

The generator cooling water system mainly provides uninterrupted water source to the stator winding and lead wire of the generator. Its advantages are large water heat capacity, high thermal conductivity and cooling capacity, stable chemical properties of water, no combustion at high temperatures, convenient adjustment, and uniform cooling.

The cooling water of the generator stator must have high working reliability, otherwise it will reduce the load operation of the generator set, which will endanger the normal operation of the generator in serious cases. Therefore, there are higher requirements for the quality of cooling water, very low mechanical impurities, electrical conductivity not greater than 2vs/em, PH value between 7 and 8, hardness not greater than 2vg equivalent/L, and oxygen content as low as possible .

3. What are the ways to increase the capacity of thermal generators?

1. Improve the insulation strength of stator wires and rotor turns. After the generator insulation appraisal, its mechanical and dielectric properties have deteriorated, and the electrical strength of the engine needs to be replaced when the upper and lower stator bars (determined by the temperature calculation experiment), the insulation material of the stator bar can be changed from the original B The insulation is changed to F grade, and the trunking part is replaced with a suitable material for insulating varnish to strengthen insulation and bonding. Wire rod insulation wrapping is used to improve the insulation quality of the wire rod, improve the rotor collector ring and lead, slot insulation, inter-row insulation, wedge factory, gasket, large guard ring insulation, etc.

2. Exchange the stator bar to increase the cross-sectional area of the copper wire. After the generator temperature rise calculation and experiment, the stator and rotor winding core temperature margin is insufficient, and in order to improve the efficiency of the generator, reduce the line current density of the stator winding, and further reduce the stator copper consumption, all the upper and lower stator bars of the stator can be replaced. With reference to the imported technology, the insulation thickness of the same voltage is increased to increase the cross-sectional area of the copper wire.

3. The generator is equipped with copper shielding and pipeline water cooling to reduce end loss and reduce the temperature of main structural parts at the end.

4. Modification of other defective parts.

Fourth, improving certain parameters of the hydrogen-cooled generator can improve the efficiency of the generator

The higher the hydrogen pressure, the higher the hydrogen density and the higher its thermal conductivity. Therefore, when the temperature rise of all parts of the generator remains unchanged, more heat can be dissipated and the efficiency of the generator can be improved. Especially the efficiency of hydrogen internal cooling engine is more obvious.

If the purity of hydrogen is too high, the greater the amount of hydrogen consumed by the generator, the less economical it is. However, if the purity of hydrogen is too low, the safety factor of the mixed gas will decrease due to the decrease in hydrogen content. Therefore, the purity of hydrogen should be maintained at 96%-98% by volume, and the oxygen content in the gas mixture should not exceed 2%.

The humidity of hydrogen is the main factor that affects the insulation of the generator. The higher the humidity of hydrogen, the more the insulation strength of the generator will be reduced, the insulation of the generator will not meet the standard, and the normal operation of the generator will be affected.

5. The main factors affecting the hydrogen supplement rate

The hydrogen supplement rate refers to the amount of hydrogen that needs to be supplemented daily to maintain the hydrogen pressure of the hydrogen-cooled generator.

1. Leakage of the internal cold water system of the generator and hydrogen leakage into the internal cold water;

2. The oil pressure of the generator sealing oil is low, the hydrogen oil separation equipment fails, and hydrogen enters the oil system;

3. The hydrogen pressure gauge tube is blocked or the gauge fails;

4. The generator end cover and outlet seal (sealed busbar) are poor;

5. Leakage in hydrogen system pipelines, valves, instrument joints, etc.;

6. Valves such as the hydrogen supplement valve of the generator hydrogen system are not tight, causing internal leakage.

6. Measures to reduce hydrogen supplement rate

1. After major repairs or generators that are working to eliminate hydrogen leakage defects, the overall air tightness test should be carried out before starting, and the test lasts for 24 hours (not less than 12 hours in special cases). The maximum allowable hydrogen leakage in the air tightness test should meet the standard or the manufacturer's technical requirements.

2. The actual hydrogen leakage of the generator should be tested regularly every month. The test calculation method is in accordance with the National Electric Power Company's "Turbine Generator Operation Regulations" (1999 edition).

3. Use leak detectors or other methods to find hydrogen leaks and try to eliminate them. When the hydrogen content in the sealed bus bar exceeds 1%, it should be shut down immediately to check for leaks. When the ammonia content in the generator bearing oil system or the main oil tank exceeds 1%, it should be shut down immediately to check for leakage. When ammonia gas appears in the internal cooling water system, a shutdown should be arranged as soon as possible.

4. Keep the generator sealing oil pressure higher than the ammonia pressure within the specified operating range, otherwise the ammonia pressure should be reduced for operation.

5. When internal leakage is caused by inadequate valves such as the ammonia supply valve of the generator ammonia system, try to eliminate it.

7. The harm of low voltage to economy and safe operation

1. Burn down the electric motor. If the voltage is too low for more than 10%, the motor current will increase, the coil temperature will rise, and in severe cases, the mechanical equipment will stop running or fail to start, or even burn the motor;

2. The lights are dim. The voltage is reduced by 5%, the illuminance of ordinary lighting is reduced by 18%; the voltage is reduced by 10%, and the illuminance is reduced by 35%; the voltage is reduced by 20%. The fluorescent lamp cannot be started;

3. Increase the line loss. When a certain amount of power is delivered, the voltage decreases and the current increases correspondingly, causing the line loss to increase;

4. Reduce the static and transient stability of the power system. As the voltage is reduced, the transmission limit capacity of the line is reduced correspondingly, thus reducing the stability, and voltage collapse may occur when the voltage is too low;

5. The generator output is reduced. If the voltage drops by more than 5%, the generator output will also be reduced accordingly;

6. Affect the stability of voltage. If the regional reactive power compensation is insufficient, the reactive power deficit can only be compensated by the voltage drop, resulting in an increasing reactive power deficit and a lower and lower voltage until it collapses.