Large Coal-fired Units Rb Run Back Function Of Research And Practice Of Technology

As the power technology develops and the capacity of units becomes larger and larger, the control requirement of the operation parameters is accordingly raised and the units also need higher automatic adjusting ability and fault-correcting ability. Only depending on the manual operation is bound to cause the units and equipment unstable, it has been unable to meet the control requirement. RunBack(RB) is a function that controls the system to correct the fault automatically when the failure of the main auxiliary equipment occurs. RB function is very important to the improvement of the efficiency and stability of the units.The design purpose of the RB function of the Coordinating Control System is to guarantee that the load will be automatically forced down to the planned load that the units permit by he coordinative action of the control systems including the Coordinating Control System (CCS), Furnace Safety Supervising System (FSSS), Sequence Control System (SCS) and_Steam turbine control System(DEH) when the auxiliary equipment failure, and that once the load reaches the target, the auxiliary equipment will run safely, economically and stably. RB function can not only test the condition and performance of the CCS and other automatic control systems and their anti-interference ability, but also adjust and optimize their control circuits and make the thermos-control system work under the best condition, which enables the load control for the whole course.The RB function has the following characteristics:1. RB function is suitable for all operation modes; it can be performed under no matter manual mode or unit self-controlling mode.2. The design of the RB function sticks to high automation level. It will automatically occur and end without the operator's interference and the unit can run very stably.3. It soles the problem of the RB of water supply pumps under the condition that when two.steam-driven water supply pumps running, the pump cannot automatically re-start, thus, can guarantee the operation of the water supply system. Because when most units are working normally, in order to save power, the pumps will not stay standby.4. It solves the problem that the coal grater can easily trip when the RB of the direct blowing type milling system and primary air system5. It also solves the problem that the drop-extent of the pressure in the furnace is too big when the RB of the forced fans and induced fansNow, a lot of the electric power plants and study organizations are studying on the CCS RB function, and it has already come into use in some plants. Judging from the condition of its functional finish condition, the automatic level of the actual tests is still low and only manage not to make the fire of the furnace go out or the unit stop. Based on the condition that the units can completely automatically run, my plan is not only to guarantee the unit to restore to normal working condition when all the control systems are in order, but also to ensure the units to fulfill the task of cutting off the coal powder and reducing the load automatically and when some parts of the automation of the unit go wrong, thus, it helps the operator to keep the units stable.