Introduction To The Principle Of Diesel Generators

After the main valve of the turbine is closed, the grid-connected turbogenerator operates as a synchronous motor, absorbing active power and dragging the turbine to rotate, thus generating reactive power for the system. Because the main valve of the steam turbine has been closed, the steam turbine tail blade and residual steam friction, forming explosion damage, overheating damage after long-term operation. Gas and water turbines also mainly damage the prime mover. Generator reverse power protection mainly protects the turbine from damage.

The setting of steam turbine inverse power protection is to determine the protection action power Pdz and action delay T.

1、The operation power of the reverse power protection of the turbogenerator can be calculated as follows :Pdz =(krel * P1)/ηPdz- the operation power of the reverse power protection krel- reliability coefficient, take 0.8 P1- the power consumed by the turbine to maintain the synchronous speed after the main valve is closed, It is related to the structure and capacity of the steam turbine. It is also related to the structure of the main steam system of the turbine generator (pipeline structure and whether there are bypass pipes, etc.). Under normal circumstances, the rated power η of 1.5 ~ 2%(the efficiency when the generator drives the turbine generator to rotate) is 0.98~0.99, so :PDZ∑(1.2 ~ 1.6%) PN - the rated power of the generator. In fact, Pdz = 1-1.5% PN is better.

2、 Action delay .The action delay of generator inverse power protection should be set according to the allowable running time of the main valve closing of the turbine generator. The allowable time is generally 10 ~ 15 minutes. Calculation and operation practice show that when the steam turbine system has bypass pipe, the allowable running time is longer. Therefore, if the protection action delay is set according to the allowed running time after the main valve of the steam turbine is closed, 5 ~ 10 minutes can be taken. After action, it is applied to demagnetization.

In addition, most large turbogenerators in operation use reverse power protection to initiate programmed trip circuits. At this point, the action time usually takes 1 to 2s. For programmed inverse power protection, due to the short operation time, the actual inverse power may be small due to the inertia of the steam turbine and generator in a short time after the main valve is closed, so the fixed value of the inverse power should not be greater than 1%PN.

Generator manufacturer principle introduction

When the generator has reverse power (the external power points to the generator, i.e. the generator becomes the motor), the reverse power protects the action circuit breaker from tripping. Three phase voltage and two phase current signals need to be collected.

Because of the different forms of primary energy, different generators can be made. Hydrogenerators can be made from water and turbines. Due to different reservoir capacity and drop, hydro-generators with different capacity and speed can be manufactured. Using coal, oil and other resources, with boilers and turbo-steam engines, steam turbine generators can be made, mostly high-speed motors (3000rpm). There are also generators that use solar, wind, atomic, geothermal, tidal and bioenergy. In addition, because of the different working principles of generators, they are divided into DC generators, asynchronous generators and synchronous generators. The large generators widely used are synchronous generators.