In the process of using hoists in coal fields and industrial and mining enterprises, reverse power transmission often occurs, causing the generator to trip due to reverse power. In order to ensure the safe operation of industrial and mining enterprises, the safety of the distribution system is not affected by the problem of reverse power transmission of the hoist, and reverse power transmission to the power generation system is prevented, and the power generation power supply is used scientifically and reasonably. Therefore, it is necessary to safely control the reverse power and absorb the reverse power. Therefore, it is necessary to configure a reverse power absorption device. The task of this device is to monitor the high-voltage side of the generator in real time; to perform necessary control on the reverse power transmission of the power generation. The microcomputer device and control circuit specially designed for it are used, which can ensure the rapidity of protection action and the accuracy of control.

The role of reverse power protection

The reverse power protection of the generator is mainly used to protect the steam turbine. Generally speaking, the power direction of the generator should flow from the generator to the busbar. However, when the main steam valve of the steam turbine is closed due to various reasons and the generator outlet circuit breaker is not tripped, the generator will become a motor, that is, it will draw active power from the system to drive the steam turbine to rotate, and the power direction will flow from the busbar to the generator, which is reverse power.

This operating condition has no effect on the generator, but for the steam turbine, since there is no steam inflow, the rotation of the steam turbine will cause serious blast friction inside, causing blade overheating damage, low-pressure cylinder exhaust temperature increase, and the low-pressure cylinder will expand upward as a whole. The center of the rotor moves upward, causing unit vibration when the bearing seat position remains unchanged. Therefore, reverse power protection is set. When reverse power occurs, the generator-transformer group is decoupled to protect the steam turbine.

The role of reverse power protection of program tripping

The reverse power protection of the generator program tripping is mainly used to prevent the steam turbine from overspeeding. When the generator is carrying a certain active load, the generator outlet circuit breaker suddenly trips and the main steam valve of the steam turbine is not completely closed, the steam turbine may have an overspeeding and runaway accident. In order to avoid the occurrence of such major accidents, under abnormal operating modes such as overload and demagnetization of the excitation winding, the protection generally adopts a program tripping method. After actuation, it acts on the main steam valve of the steam turbine to close first. After the reverse power relay of the generator is actuated, it forms an AND gate with the auxiliary contacts connected after the main steam valve is closed. After a short time limit, it forms a program tripping reverse power protection, which acts on the whole stop after actuation.