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Principle of inverse power protection of generator

 Introduction of generator reverse power protection      

       Turbo generator and power grid is running at the paralleling time ,due to some causes then closed  turbine main steam valve, the generator transferred by output power into the synchronous speed and power loss absorption to maintain the generator, this state is called the inverse power operation, the generator will become the motor running, which absorbs the active power from the system, the operation effect of drag turbine to rotate. On the condition of the steam turbine generator is not but for a long time without running steam will cause the exhaust cylinder temperature and the tail blades. Due to overheating steam cylinder filled with no current, it will produce friction heat and steam turbine blades, the turbine blade temperature and low pressure cylinder exhaust Temperature rise, the overall upward expansion of the low-pressure cylinder, the rotor center up, in the case of the bearing seat of the same location caused the unit vibration.
 generator backup protection
9688 generator back-up protection relay
 
Generator reverse power protection      
       Input reverse power protection for terminal two PT and two CT three-phase voltage generator of three-phase current. When the generator active power absorption action. Therefore, reverse power protection can accurately react power abnormal conditions in the opposite direction, timely signals, automatic stop within the time allowed.
 
Inverse power protection action time problem.
       Electrical protection, when the turbine reverse power operation, the first signal, after a certain period of time delay protection export series generator, the delay time is not allowed according to the running time of the steam turbine condition setting, usually for 1 to 3 minutes. If the solution by using the program column generator tripping inverse solution column generator power protection, reverse power running times than the automatic main valve closed signal generator terminal series number, so from the perspective of protection of steam turbine, the delay time can be shortened, as long as the turbine regulating system can hide from grid due to reverse power operation instantly appears error generator can shorten the jump. The protection of trip time will bring benefits, in some cases, for example, due to the down off blade turbine fault, automatic main steam valve is closed, start the program trip inverse column generator power protection, if the delay is too long, will aggravate the damage degree of the turbine generator.
 
Reverse power protection action results       
       For the generator outlet switch is non three-phase linkage switch, reverse power protection exports should only jump generator outlet switch, and also should not jump out the magnetic switch. When the generator non all phase operation, namely generator circuit breaker incomplete phase disconnection or non identical, the stator current of three-phase generator the balance of negative sequence current and vibration in the induction rotor surface current is two times the frequency, causes the rotor fever, severe burning in the rotor. Generator negative sequence current without negative sequence current or no-load generator non all phase operation is very small; the non full phase generator circuit breaker disconnect, demagnetization switch off and at the same time The original motivation for the energy supply is cut off, the generator negative sequence current, the system, and have the greatest impact on the generator, must cut off the power immediately related, thus expanding the scope of the accident. So the reverse power protection action jump development of motor outlet switch, magnetic switch without tripping out, if the generator outlet switch the disconnect, can immediately reduce the excitation current of the generator, maintain the no-load operation, then according to the rules.
 
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209585994

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