Countermeasures for safe operation of thermal power units
large thermal power units have well-designed interlocking protection of turbine, boiler and electric power university and relevant thermal protection of their respective equipment (including auxiliary equipment), ensuring the normal and safe operation of the units. However, sometimes in the process of unit operation, the thermal protection malfunctions due to some reasons, resulting in unit disconnection, which affects the stable operation of electricity and damages the economic benefits and image of the enterprise
1 thermal protection operation condition
with the improvement of equipment quality, technical level and personnel quality, the thermal protection reliability of thermal power units has been greatly improved than before. However, from the perspective of power supply in the whole area, the unit trip caused by thermal protection maloperation still accounts for a large proportion of unplanned outage. For example, at the peak of power consumption in July 2000, Huazhong power had 17 times of unit disconnection due to the failure of thermal protection, which seriously affected the normal operation of power. Eight of them were due to MFT action of 300 MW unit caused by "low drum water level", and the cause of "low drum water level" was due to the failure of electric pump interlock startup after steam pump trip
from the above situation, it is necessary to study and improve the reliability of thermal protection so that "the digital display electronic tensile testing machine can detect the stretching, tearing, peeling, tightening, bending, shearing, bursting, puncturing, fatigue and other items of metal materials, non-metal materials and high molecular materials when it is in motion, and it will not move if it is not in motion"
the above is the relevant knowledge to avoid rusting of universal experimental machine 2. Countermeasures to improve the reliability of thermal protection
2.1 technical measures for thermal engineering
as large thermal power generator sets are designed with advanced DCS distributed control system, and the DCS system is relatively stable and reliable in terms of industrial control computer, network topology, signal acquisition board and other hardware, system software and application software, It lays a good foundation for the reliable input of thermal protection. At present, the FSSS (BMS) furnace safety monitoring system and auxiliary equipment protection of most 300 MW coal-fired thermal power units are realized by the DCS system. This method is simple and reliable, and can fully reflect the advantages of the DCS system in the application of "risk dispersion and centralized control". However, the following points should be paid attention to:
(1) if the collected multiple signals are the same signal, they should be scattered on different modules of the same DPU as far as possible, For example, the three negative pressure switching value signal points of two out of three for material pressure with large negative elongation in furnace, the six analog signal points of two out of three for drum water level (three drum pressures and three differential pressure signals of balance vessel), the bearing temperature thermal resistance signal of fan and the motor coil temperature thermal resistance signal can be treated in this way
(2) taking two out of three or three out of four signals in itself is to improve the reliability of protection, prevent protection maloperation and try to avoid protection refusal
(3) in order to prevent accidents on site during DCS logic configuration, each signal can be connected in series with a corresponding quality judgment signal to improve the reliability of protection. There are turning, grinding, planing and washing processes; CNC technology; Wire cutting process; What processing technology is selected? It will directly affect the performance and price.
(4) during cable laying, special attention shall be paid to the anti-interference of thermal resistance, thermocouple temperature signal and 24VDC and 48VDC switching value signal