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Principle of Generator Reverse Power Protection

       Generator reverse power protection is one of the important protection of the generator, I produced the 9688 generator backup protection device, with generator reverse power protection, users are welcome to consult! 


9688 generator backup protection device

Introduction of Generator Inverse Power Protection

       When the turbine generator and the grid are running in parallel, the generator is turned off by the output power to absorb the power of the grid to maintain the synchronous speed and loss of the generator for some reason. This state is called reverse power operation, At this time the generator will become the motor running, that is, from the system to absorb active power, drag the turbine rotation. This operating condition has no effect on the generator, but for steam turbines, prolonged no steam operation will cause the cylinder temperature to rise and the tail leaves to overheat. As the cylinder is filled with non-flow of steam, it will produce heat with the friction of the turbine blades, so that the steam turbine blade overheating and low pressure cylinder exhaust steam temperature rise, the overall expansion of the low-pressure cylinder, the rotor center shift, the same position in the bearing The case caused the unit vibration.

Generator reverse power protection 

       Reverse power protection input for the machine terminal PT secondary three-phase voltage and generator CT secondary three-phase current. When the generator absorbs active power when the action. Therefore, the reverse power protection can accurately reflect the power of the opposite direction of the abnormal conditions, timely signal, in the allowed time to automatically shut down.

Reverse power protection action time.

       In the electrical protection, when the steam turbine appears reverse power operation, the first signal, delay after a certain period of time to protect the action out of the export generator, the delay time is based on the steam turbine to allow no steam running time to set the conditions, 3 minutes. If the inverter generator mode is changed by the program trip reverse power protection action to solve the generator, the number of reverse power operation is more than the number of times the automatic main valve terminal closes the signal to solve the generator. Therefore, from the viewpoint of protecting the steam turbine, When the time can be shortened, as long as the turbine control system can escape the grid due to the moment of the reverse power operation caused by mistakenly jumping generators can be. Shortening the protection of the trip time in some cases will bring benefits, for example, the turbine due to loss of leaves and other fault shutdown, the automatic main valve closed, start the program trip reverse power protection solution generator, if the delay is too long Will aggravate the damage level of turbo-generator sets.

Reverse power protection action results

       For the generator outlet switch is a non-three-phase mechanism linkage switch, the reverse power protection action exit should only jump generator exit switch, and should not also jump off the magnetic switch. 

       When the generator is non-full-phase operation, that is, the generator outlet switch is not fully-phase open or non-full phase, the generator stator current three-phase imbalance occurs negative sequence current and vibration, in the rotor surface induced twice Frequency of the current, causing the rotor fever, serious burn the rotor. When the generator is in the no-load condition, the negative sequence current is generated when the non-negative sequence current is generated or the negative sequence current is generated. The generator outlet switch is not fully disconnected and the de-energizing switch is disconnected and the energy supply of the prime mover Cut off, the generator produces the largest negative sequence current, the system, the greatest impact on the generator, you must immediately cut off the relevant power supply, thus expanding the scope of the accident. 

       So the reverse power protection action to jump off the generator outlet switch, the de-excitation switch is not jump, if the generator outlet switch is not fully-phase disconnect, can immediately reduce the excitation current, so that the generator to maintain no-load operation, and then according to the procedures deal with.


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