CN114110647B

CN114110647B - System and method for improving MFT protection reliability of thermal power generating unit boiler

Info

Publication number: CN114110647B
Application number: CN202111434120.9A
Authority: CN
Inventors: 曲广浩; 赵志丹; 王邦行; 李�杰; 刘孝国; 周昭亮; 安欣; 张开鹏; 唐伟; 杨光锐; 李继福; 王勇刚; 何未雨; 张海龙; 李钊; 吴猛; 曹勇
Original assignee: Xian Thermal Power Research Institute Co Ltd
Current assignee: Xian Thermal Power Research Institute Co Ltd
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2023-06-27
Anticipated expiration: 2041-11-29
Also published as: CN114110647A

Abstract

The invention discloses a system and a method for improving the protection reliability of an MFT of a boiler of a thermal power unit, comprising the following steps: the problems of protection misoperation caused by network communication signals are solved by connecting each 6KV power equipment switch cabinet, each air preheater main motor control cabinet, each air preheater auxiliary motor control cabinet, each air preheater stall detection device and each pressure measurement device into the protection system control cabinet in a hard-wired mode. The invention adopts a switch opening signal to realize a three-out-two logic judgment mode, and solves the problem that the protection refuses due to the adoption of the switch opening signal in the full-stop protection of 6KV switch equipment such as fans and the like. The invention is provided with the first air preheater stall detection device and the second air preheater stall detection device, so that the problem of protection refusal is solved. The invention provides a protection system for the pressure measuring points of the three-side furnace, which solves the problem of misoperation protection. The reliability of the whole system is improved by improving the reliability of the blower shutdown protection subsystem, the air preheater shutdown protection subsystem and the hearth pressure protection subsystem.

Description

System and method for improving MFT protection reliability of thermal power generating unit boiler

Technical Field

The invention belongs to the technical field of automatic control of thermal power plants, and relates to a system and a method for improving reliability of an MFT protection system of a boiler of a thermal power unit.

Background

Along with the improvement of the safety and stability requirements of the thermal power generating unit, the requirements on the interlocking protection configuration of the unit are also higher and higher. In recent years, the related standard specification of the thermal control interlocking protection is gradually improved, and various power plants are subjected to a great amount of improvement and improvement work in comparison with the standard specification, so that a good effect is achieved. However, some protection systems after the machine set is finished have new problems, and even cause non-stop events of the machine set. The main reason for analysis is that the configuration of the thermal control protection signal is unreasonable and can not adapt to some special working conditions.

Shutdown signal of 6KV power equipment

According to the relevant regulations: all important main and auxiliary machine protection should adopt a logic judgment mode of 'three-out-of-two', and in recent years, most power plants realize three-out-of-two logic by adding protection signal redundancy configuration, so that the thermal control protection reliability is greatly improved. However, in practical application, the total stop protection of important power equipment such as a blower, a draught fan, a primary fan and the like in the MFT protection exposes some problems and defects.

Network communication signal is adopted for shutdown protection of 6KV power equipment

And the equipment shutdown signals are directly taken from the electric 6KV switch cabinet. Because the electrical switch cabinet sends out a limited signal, many power plants adopt a logic judgment mode of 'switching on and off' and 'current lower than a fixed value' to form 'three-out-two' so as to meet related regulations.

However, although the power plant shutdown protection realizes the three-out-of-two logic, due to the limitation of signal sources, a compromise scheme is adopted, for example, a fan stop signal in the whole shutdown protection of a blower still adopts an original hard-wired switch-off signal, a switch-on signal and a current signal all adopt network communication signals, and the signals participate in the three-out-of-two logic after being respectively subjected to negation and low limit judgment. The scheme utilizes the existing signal of the DCS, has small workload and is easy to realize, but has larger potential protection false operation hazards. If the DCS network communication fails, a switch closing signal received in logic becomes 0, and the signal is 1 after the signal is inverted; and the received current signal is lost, and logic '1' is sent out after the low limit judgment. The two conditions are that "1" satisfies the three-out-of-two logic operation condition, and the "blower complete stop" signal is sent out, resulting in MFT protection misoperation.

6KV power equipment protection adopts separating brake signal

The shutdown protection of the power equipment of the power plant directly takes three switch-off signals of the 6KV power equipment, and three-out-of-two logic is realized. However, for a double-row fan unit, under certain special working conditions, a protection refusing action risk exists. If a certain fan stops running and is out of order in the running process of the unit, in order to ensure safety, a fan 6KV switch is pulled out after power failure, signals of switching on and switching off cannot be sent out, and a fan stop signal in a DCS is 0. During this time, if another fan trips, because the shutdown signal of the defect fan is "0", the total shutdown signal of the two fans cannot be sent, and the MFT protection will be refused.

Air preheater shutdown protection

In the protection of the full stop MFT of the air preheater, the 'full stop of the main motor and the auxiliary motor' signals are basically adopted by each power plant, but if the coupling of the air preheater is damaged, the 'full stop of the main motor and the auxiliary motor' signals can not be sent out, and the related lock protection of the MFT, the RB, the air smoke baffle of the inlet and outlet of the linked air preheater and the like can not be triggered, so that the hidden safety hazards of burning the equipment of the air preheater, the sudden rise of the smoke discharge temperature, the refusal of the MFT and the RB and the like exist.

Hearth pressure high-low protection

For boiler furnace pressure protection, a pressure switch is generally adopted to measure a furnace pressure or a furnace pressure signal, and the signal is sent to a DCS system to be judged by a logic of three-out-two to form a furnace pressure high or furnace pressure low signal to trigger MFT action. Most of the power plants with sampling measuring points adopt front and rear wall arrangement of a boiler, two measuring points are arranged on one side, one measuring point is arranged on the other side, and a DCS adopts a logic of three to two. For example, the flue collapses ash or the hearth drops coke, and the like, the single-side pressure is easy to instantaneously and greatly fluctuate, so that the single-side furnace pressure switch action, such as the switch action of two measuring point sides, can meet the logic action condition of 'three-out-of-two', and the MFT protection misoperation is triggered.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides a method for improving the reliability of an MFT protection system of a thermal power unit boiler, so that the safety of the thermal power unit boiler MFT is ensured.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

a system for improving MFT protection reliability of a thermal power generating unit boiler, comprising:

the fan outage protection subsystem and the MFT logic loop are positioned in the protection system control cabinet;

the fan outage protection subsystem comprises: the first logic judgment protection subsystem and the second logic judgment protection subsystem; the first logic judgment protection subsystem and the second logic judgment protection subsystem are connected through an MFT logic loop;

The first logic judgment protection subsystem comprises: the first NOT gate logic gate, the second NOT gate logic gate, the first low limit judgment gate, the second low limit judgment gate, the first three-out-of-two logic gate, the second three-out-of-two logic gate and the first AND gate logic gate;

the second logic judgment protection subsystem comprises: the third NOT gate logic gate, the third two-out-of-three gate logic gate, the fourth NOT gate logic gate, the fourth two-out-of-three gate logic gate and the second AND gate logic gate;

the first low limit judgment gate and the first NOT gate logic gate are simultaneously connected with a first three-out-of-two logic gate; the second NOT gate logic gate and the second low limit judgment gate are connected with a second three-out-of-two logic gate; the second three-out-of-two logic gate and the first three-out-of-two logic gate are simultaneously connected with the first AND gate logic gate;

the third NOT gate logic gate is connected with a third two-out-of-three logic gate; the fourth NOT logic gate is connected with the fourth two-out-of-three logic gate; the third two-out-of-three logic gate and the fourth two-out-of-three logic gate are simultaneously connected with the second AND gate logic gate; the first and gate logic gate and the second and gate logic gate are connected with the MFT logic loop.

The invention further improves that:

the system also comprises an air preheater shutdown protection subsystem; the air preheater shutdown protection subsystem comprises: a fifth NOT gate logic gate, a third low limit judgment logic gate, a third AND gate logic gate, a sixth NOT gate logic gate, a fourth low limit judgment logic gate, a fourth AND gate logic gate, a fifth three-out-of-two logic gate, a sixth three-out-of-two logic gate, a first OR gate logic gate, a sixth AND gate logic gate, a seventh NOT gate logic gate, a fifth low limit judgment logic gate, an eighth NOT gate logic gate, a sixth low limit judgment logic gate, an eighth AND gate logic gate, a ninth AND gate logic gate, a tenth AND gate logic gate, and a fourth OR gate logic gate;

The air preheater shutdown protection subsystem is connected with the MFT logic loop through a sixth AND gate logic gate; the air preheater off-line protection subsystem is positioned in the protection system control cabinet;

the third low limit judgment logic gate and the fifth NOT gate logic gate are simultaneously connected with a third AND gate logic gate; the fourth low limit judgment logic gate and the sixth NOT gate logic gate are simultaneously connected with the fourth AND gate logic gate; the third AND gate logic gate and the fourth AND gate logic gate are simultaneously connected with the fifth AND gate logic gate; the fifth two-out-of-three logic gate and the fifth AND gate logic gate are connected with the first OR gate logic gate at the same time;

the seventh NOT gate logic gate and the fifth low limit judgment logic gate are connected with an eighth AND gate logic gate; the eighth NOT gate logic gate and the sixth low limit judgment logic gate are connected with a ninth AND gate logic gate; the ninth AND gate logic gate and the eighth AND gate logic gate are connected with the tenth AND gate logic gate at the same time; the sixth two-out-of-three logic gate and the tenth AND gate logic gate are connected with the fourth OR gate logic gate at the same time;

the first or gate logic gate and the fourth or gate logic gate are connected with the sixth or gate logic gate.

The furnace pressure protection subsystem comprises a three-side furnace pressure measuring point protection subsystem and a double-side furnace pressure measuring point protection subsystem;

The hearth pressure protection subsystem is positioned in the protection system control cabinet;

the double-side furnace pressure measuring point protection subsystem and the three-side furnace pressure measuring point protection subsystem are simultaneously connected with an MFT logic loop; the double-side furnace pressure measuring point protection subsystem comprises a second or gate logic gate, a third or gate logic gate and a seventh or gate logic gate; the second or gate logic gate and the third or gate logic gate are connected with a seventh or gate logic gate; the seventh AND gate logic gate is connected with the MFT logic loop;

the three-side furnace pressure measuring point protection subsystem comprises: a seventh three-out-of-two logic judgment gate;

the seventh two-out-of-three logic judgment gate is connected with the MFT logic loop.

Further comprises: the first 6KV power equipment switch cabinet, the second 6KV power equipment switch cabinet, the first current transducer, the second current transducer, the third 6KV power equipment switch cabinet and the fourth 6KV power equipment switch cabinet;

the first logic judgment protection subsystem is connected with the first 6KV power equipment switch cabinet, the second 6KV power equipment switch cabinet, the first current transducer and the second current transducer at the same time;

the first 6KV power equipment switch cabinet is respectively connected with a first two-out-of-three logic gate and a first NOT logic gate; the first current transmitter is connected with a first low limit judgment gate;

The third 6KV power equipment switch cabinet and the fourth 6KV power equipment switch cabinet are simultaneously connected with a second logic judgment protection subsystem; the third 6KV power equipment switch cabinet is connected with a third NOT gate logic gate; the fourth 6KV power equipment switch cabinet is connected with a fourth NOT gate logic gate;

the first 6KV power equipment switch cabinet, the second 6KV power equipment switch cabinet, the first current transducer, the second current transducer, the third 6KV power equipment switch cabinet and the fourth 6KV power equipment switch cabinet are respectively connected with the protection system switch cabinet in a hard-wired mode.

Further comprises: the system comprises a first air preheater main motor control cabinet, a third current transmitter, a first air preheater auxiliary motor control cabinet, a fourth current transmitter, a first air preheater stall detection device, a second air preheater main motor control cabinet, a fifth current transmitter, a second air preheater auxiliary motor control cabinet, a sixth current transmitter and a second air preheater stall detection device;

the air pre-heater shutdown protection subsystem is simultaneously connected with a first air pre-heater main motor control cabinet, a third current transmitter, a first air pre-heater auxiliary motor control cabinet, a fourth current transmitter, a first air pre-heater shutdown detection device, a second air pre-heater main motor control cabinet, a fifth current transmitter, a second air pre-heater auxiliary motor control cabinet, a sixth current transmitter and a second air pre-heater shutdown detection device;

The first air preheater main motor control cabinet is connected with a fifth NOT gate logic gate; the third current transducer is connected with a third low limit judgment logic gate; the first air preheater auxiliary motor control cabinet is connected with a sixth NOT gate logic gate; the fourth current transducer is connected with a fourth low limit judgment logic gate;

the first air preheater stall detection device is connected with a fifth two-out-of-three logic gate;

the second air preheater main motor control cabinet is connected with a seventh NOT gate logic gate; the fifth current transducer is connected with a fifth low limit judgment logic gate;

the second air preheater auxiliary motor control cabinet is connected with an eighth NOT gate logic gate; the sixth current transducer is connected with a sixth low limit judgment logic gate;

the second air preheater stall detection device is connected with a sixth two-out-of-three logic gate;

the first air preheater main motor control cabinet, the third current transmitter, the first air preheater auxiliary motor control cabinet, the fourth current transmitter, the first air preheater stall detection device, the second air preheater main motor control cabinet, the fifth current transmitter, the second air preheater auxiliary motor control cabinet, the sixth current transmitter and the second air preheater stall detection device are respectively connected with the protection system control cabinet in a hard-wired mode.

Further comprises: a first pressure measurement device, a second pressure measurement device, a third pressure measurement device, a fourth pressure measurement device, a fifth pressure measurement device, a sixth pressure measurement device, and a seventh pressure measurement device;

The first pressure measuring device, the second pressure measuring device, the third pressure measuring device and the fourth pressure measuring device are simultaneously connected with the double-side furnace pressure measuring point protection subsystem;

the fifth pressure measuring device, the sixth pressure measuring device and the seventh pressure measuring device are simultaneously connected with the three-side furnace pressure measuring point protection subsystem;

the first pressure measuring device and the second pressure measuring device are simultaneously connected with a second OR gate logic gate; the third pressure measuring device and the fourth pressure measuring device are simultaneously connected with a third OR gate;

the fifth pressure measuring device, the sixth pressure measuring device and the seventh pressure measuring device are simultaneously connected with a seventh three-out-two logic gate

The first pressure measuring device, the second pressure measuring device, the third pressure measuring device, the fourth pressure measuring device, the fifth pressure measuring device, the sixth pressure measuring device and the seventh pressure measuring device are respectively connected with the protection system control cabinet in a hard-wired mode.

The first air preheater stall detection device and the second air preheater stall detection device are respectively three sets.

A method for improving MFT protection reliability of a thermal power generating unit boiler, comprising:

the first 6KV power equipment switch cabinet sends a first switch closing signal and a first switch opening signal, and the first switch closing signal is inverted through a first NOT logic gate to obtain a first switch closing NOT signal; the first current signal sent by the first current transducer is judged by a first low limit judgment gate to obtain a signal that the first current is lower than a fixed value; the first switch opening signal, the first switch closing non signal and the first current lower than a fixed value signal are judged through a first three-out-of-two logic gate to obtain a first power equipment outage signal;

The second 6KV power equipment switch cabinet sends out two signals of a second switch closing signal and a second switch opening signal, and the second switch closing signal is inverted through a second NOT logic gate to obtain a second switch closing NOT signal; the second current signal sent by the second current transducer is judged by a second low-limit judging gate to obtain a second current lower than a fixed value; judging a second switch opening signal, a second switch closing non signal and a second current lower than a fixed value signal through a second three-out-of-two logic gate to obtain a second power equipment outage signal;

the first power equipment outage signal and the second power equipment outage signal are transmitted to an MFT logic loop through a first AND gate logic gate to obtain a first power equipment complete outage signal, and the first power equipment complete outage signal is transmitted to an MFT logic loop to trigger an MFT protection action;

the third 6KV power equipment switch cabinet sends three third switch closing signals, the three third switch closing signals are judged through a third NOT gate logic gate to obtain three third switch closing NOT signals, and the three third switch closing NOT signals are judged through a third two-out-of-three logic gate to obtain a third power equipment shutdown signal;

The fourth 6KV power equipment switch cabinet sends three fourth switch closing signals, the three fourth switch closing signals are judged through a fourth NOT gate logic gate to obtain three fourth Guan Gezha NOT signals, and the three fourth Guan Gezha NOT signals are judged through a fourth two-out-of-three logic gate to obtain a fourth power equipment shutdown signal;

judging a third power equipment outage signal and a fourth power equipment outage signal through a second AND gate logic gate to obtain a second power equipment complete outage signal; the "second power device full stop" signal is sent to the MFT logic loop to trigger MFT protection actions.

The first air preheater main motor control cabinet sends a first main motor running signal, and the first main motor running signal is judged through a fifth NOT gate logic gate to obtain a first main motor stopping signal;

the third current signal sent by the third current transducer is judged by a third low limit judgment logic gate, so as to obtain a signal that the third current is lower than a fixed value; the third current lower than a fixed value signal and the first main motor stop signal are judged through a third AND gate logic gate, and a first air preheater main motor stop signal is obtained;

The first air preheater auxiliary motor control cabinet sends a first auxiliary motor running signal, and the first auxiliary motor running signal is judged through a sixth NOT gate logic gate to obtain a first auxiliary motor stop signal;

the fourth current signal sent by the fourth current transducer is judged by a fourth low limit judgment logic gate, and a signal that the fourth current is lower than a fixed value is obtained; the signal that the fourth current is lower than a fixed value and the signal that the first auxiliary motor stops are judged through a fourth AND gate logic gate, so that a signal that the first air preheater is stopped for the auxiliary motor is obtained;

the first air preheater main motor outage signal and the first air preheater auxiliary motor outage signal are subjected to a fifth AND gate logic gate to obtain a first air preheater motor outage signal;

the first air preheater stall detection device sends three signals of low rotating speed of the first air preheater, and the three signals of low rotating speed of the first air preheater are judged through a fifth two-out logic gate to obtain a signal of first air preheater stall; judging a first air preheater stop signal and a first air preheater motor stop signal through a first OR gate logic gate to obtain a first air preheater stop signal;

The second air preheater main motor control cabinet sends a second main motor running signal, and the second main motor running signal is judged through a seventh NOT gate logic gate to obtain a second main motor stopping signal;

a fifth current signal sent by a fifth current transducer is judged by a fifth low limit judgment logic gate, and a fifth current signal lower than a fixed value is obtained; the fifth current lower than a fixed value signal and the second main motor stop signal are judged through an eighth AND gate logic gate, and a second air preheater main motor stop signal is obtained;

the second air preheater auxiliary motor control cabinet sends a second auxiliary motor running signal, and the second auxiliary motor running signal is judged through an eighth NOT gate logic gate to obtain a second auxiliary motor stop signal;

a sixth current signal sent by a sixth current transducer is judged through a sixth low limit judgment logic gate, and a signal that the sixth current is lower than a fixed value is obtained; the signal that the sixth current is lower than a fixed value and the signal that the second auxiliary motor stops are judged through a ninth AND gate logic gate, and a signal that the second air preheater is stopped for the auxiliary motor is obtained;

the second air preheater main motor outage signal and the second air preheater auxiliary motor outage signal are subjected to a tenth AND gate logic gate to obtain a second air preheater motor outage signal;

The second air preheater stall detection device sends out three signals of low rotation speed of the second air preheater, and the three signals of low rotation speed of the second air preheater are judged through a sixth two-out logic gate to obtain a signal of second air preheater stall; judging a second air preheater stop signal and a second air preheater motor stop signal through a fourth OR gate logic gate to obtain a second air preheater stop signal;

judging the first air preheater stop signal and the second air preheater stop signal through a sixth AND gate logic gate to obtain an air preheater complete stop signal; the air preheater complete stop signal is transmitted to the MFT logic loop to trigger the MFT protection action.

The first pressure measuring device and the second pressure measuring device respectively send a first furnace pressure signal and a second furnace pressure signal, and the first furnace pressure signal and the second furnace pressure signal are judged through a second OR gate logic gate to obtain a first pressure signal;

the third pressure measuring device and the fourth pressure measuring device respectively send a third furnace pressure signal and a fourth furnace pressure signal, and the third furnace pressure signal and the fourth furnace pressure signal are judged through a third OR gate logic gate to obtain a second pressure signal;

The first pressure signal and the second pressure signal are judged through a seventh AND gate logic gate to obtain first furnace pressure information, and the first furnace pressure information enters an MFT logic loop to trigger MFT protection action;

the fifth pressure measuring device, the sixth pressure measuring device and the seventh pressure measuring device respectively send a fifth furnace pressure signal, a sixth furnace pressure signal and a seventh furnace pressure signal, the fifth furnace pressure signal, the sixth furnace pressure signal and the seventh furnace pressure signal are judged through a seventh two-out-of-three logic gate to obtain second furnace pressure information, and the second furnace pressure information enters an MFT logic loop to trigger MFT protection action.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the fan off-operation protection subsystem is connected with the MFT logic loop, and all logic gates in the fan off-operation protection subsystem are connected with each other, so that the reliability of the fan in the operation process can be realized; meanwhile, the space-time pre-heater shutdown protection subsystem and the hearth pressure protection subsystem are respectively connected with an MFT logic loop, and a stable signal trigger loop is constructed through the logic loops of the subsystems, so that the reliability of the whole system is improved. According to the invention, each 6KV power equipment switch cabinet, each air preheater main motor control cabinet, each air preheater auxiliary motor control cabinet, each air preheater stall detection device and each pressure measurement device are connected into the protection system control cabinet in a hard wiring mode, so that the problem of protection misoperation caused by network communication signals is solved. The invention adopts a switch brake-separating signal to realize a three-out-two logic judgment mode, and solves the problem that the protection refuses due to the adoption of the switch brake-separating signal in the full-stop protection of 6KV switch equipment such as a blower, a draught fan, a primary fan and the like. The invention provides a method for solving protection refusal by arranging a first air preheater stall detection device and a second air preheater stall detection device. The invention provides a method for setting a three-furnace pressure measuring point protection system and solving the problem of protection misoperation.

Drawings

For a clearer description of the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a logic diagram of a plant blower full stop protection in accordance with an embodiment of the present invention;

FIG. 2 is another logic diagram of a plant blower full stop protection according to an embodiment of the present invention;

FIG. 3 is a logic diagram of air preheater shutdown according to an embodiment of the present invention;

FIG. 4 is a logic diagram of a power plant furnace pressure protection according to an embodiment of the present invention;

FIG. 5 is another logic diagram of power plant protection according to an embodiment of the present invention.

Wherein: 1-first 6KV power equipment switch cabinet, 2-first NOT gate logic gate, 3-protection system control cabinet, 4-first low limit judgment gate, 5-first three-taking two logic gates, 6-first AND gate logic gate, 7-second 6KV power equipment switch cabinet, 8-second NOT gate logic gate, 9-second low limit judgment gate, 10-second three-taking two logic gate, 11-third 6KV power equipment switch cabinet, 12-fourth 6KV power equipment switch cabinet, 13-third NOT gate logic gate, 14-third three-taking two logic gate, 15-fourth NOT gate logic gate, 16-fourth three-taking two logic gate, 17-second AND gate logic gate, 18-first air pre-heater main motor control cabinet, 19-third current transducer, 20-first air pre-heater auxiliary motor control cabinet, 21-fourth current transducer, 22-first air pre-heater stall detection device, 23-second air pre-heater stall detection device, 24-fifth NOT gate, 25-fourth low limit judgment gate, 15-fourth NOT gate logic gate, 16-fourth three-taking two logic gate, 17-third three-second AND gate logic gate, 18-first three-second gate logic gate, 18-first three-third and fourth air pre-third gate logic gate, 19-third three-third gate logic gate, 20-first three-third and fourth gate logic gate; 32-a fifth AND gate logic gate; 33-first or gate logic gate, 34-sixth and gate logic gate, 35-first pressure measurement device, 36-second pressure measurement device, 37-third pressure measurement device, 38-fourth pressure measurement device, 39-second or gate logic gate, 40-third or gate logic gate, 41-seventh and gate logic gate, 42-fifth pressure measurement device, 43-sixth pressure measurement device, 44-seventh pressure measurement device, 45-seventh two-out-of-seventh logic gate, 46-first current transmitter, 47-second current transmitter, 48-MFT logic loop, 49-second air preheater main motor control cabinet, 50-fifth current transmitter, 51-second air preheater auxiliary motor control cabinet, 52-sixth current transmitter, 53-seventh non gate logic gate, 54-fifth low limit determination logic gate, 55-eighth non gate logic gate, 56-sixth low limit determination logic gate, 57-eighth and gate logic gate, 58-ninth and gate logic gate, 59-tenth and gate logic gate, 60-tenth and gate logic gate.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the embodiments of the present invention, it should be noted that, if the terms "upper," "lower," "horizontal," "inner," and the like indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, or the azimuth or the positional relationship in which the inventive product is conventionally put in use, it is merely for convenience of describing the present invention and simplifying the description, and does not indicate or imply that the apparatus or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

Furthermore, the term "horizontal" if present does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the embodiments of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" should be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

The invention is described in further detail below with reference to the attached drawing figures:

referring to fig. 1 to 5, the invention provides a system for improving MFT protection reliability of a thermal power generating unit boiler, comprising:

a fan outage protection subsystem, an MFT logic loop 48 and a protection system control cabinet 3;

The fan outage protection subsystem and the MFT logic loop 48 are located inside the protection system control cabinet 3;

the fan outage protection subsystem comprises: the first logic judgment protection subsystem and the second logic judgment protection subsystem; the first logic judgment protection subsystem and the second logic judgment protection subsystem are connected through an MFT logic loop 48;

the first logic judgment protection subsystem specifically comprises:

the first logic judgment protection subsystem comprises: the first NOT gate logic gate 2, the second NOT gate logic gate 8, the first low limit judgment gate 4, the second low limit judgment gate 9, the first two-out-of-three logic gate 5, the second two-out-of-three logic gate 10 and the first AND gate logic gate 6;

the first logic judgment and protection subsystem is simultaneously connected with the first 6KV power equipment switch cabinet 1, the second 6KV power equipment switch cabinet 7, the first current transmitter 46 and the second current transmitter 47;

the method comprises the steps that a first switch closing signal and a first switch opening signal are sent out by a first 6KV power equipment switch cabinet 1, and after the first switch closing signal enters a protection system control cabinet 3, a first NOT gate logic gate 2 is used for inverting, so that a first switch closing NOT signal is obtained; the first current signal sent by the first current transducer 46 enters the protection system control cabinet 3 and is judged by the first low limit judgment gate 4 to obtain a signal that the first current is lower than a fixed value; the first switch opening signal, the first switch closing non signal and the first current lower than a fixed value signal are judged through the first three-out-of-two logic gate 5, and a first power equipment outage signal is obtained.

The second 6KV power equipment switch cabinet 7 sends a second switch closing signal and a second switch opening signal, and after the second switch closing signal enters the protection system control cabinet 3, the second switch closing signal is inverted through the second NOT gate logic gate 8 to obtain a second switch closing NOT signal; the second current signal sent by the second current transducer 47 enters the protection system control cabinet 3 and is judged by the second low limit judgment gate 9 to obtain a signal that the second current is lower than a fixed value; the second switch opening signal, the second switch closing non signal and the second current lower than a fixed value signal are judged through a second three-out-of-two logic gate 10, and a second power equipment outage signal is obtained;

the first power equipment outage signal and the second power equipment outage signal are transmitted to an MFT logic loop through a first AND gate logic gate 6 to obtain a first power equipment complete outage signal, and the first power equipment complete outage signal is transmitted to an MFT logic loop to trigger an MFT protection action;

the first 6KV power equipment switch cabinet 1, the second 6KV power equipment switch cabinet 7, the first current transducer 46 and the second current transducer 47 are respectively connected with the protection system control cabinet 3 in a hard-wired mode.

The second logic judgment protection subsystem specifically comprises:

the second logic judgment protection subsystem comprises: a third not gate logic gate 13, a third two-out-of-three logic gate 14, a fourth not gate logic gate 15, a fourth two-out-of-three logic gate 16, and a second and gate logic gate 17;

the second logic judgment and protection subsystem is simultaneously connected with a third 6KV power equipment switch cabinet 11 and a fourth 6KV power equipment switch cabinet 12;

after the third 6KV power equipment switch cabinet 11 sends three third switch closing signals and enters the protection system control cabinet 3, the three third switch closing signals are obtained through judgment of a third NOT gate logic gate 13, and then judgment is carried out through a third two-out-of-three logic gate 14, so that a third power equipment shutdown signal is obtained;

after the fourth 6KV power equipment switch cabinet 12 sends out three fourth switch closing signals and enters the protection system control cabinet 3, three fourth switch Guan Gezha NOT signals are obtained through judgment of a fourth NOT gate logic gate 15, and then judgment is carried out through a fourth three-out-of-two logic gate 16, so that a fourth power equipment outage signal is obtained;

the third power equipment outage signal and the fourth power equipment outage signal are judged through a second AND gate logic gate 17, and a second power equipment complete outage signal is obtained; the second power equipment complete stop signal is transmitted to the MFT logic loop to trigger the MFT protection action;

The third 6KV power equipment switch cabinet 11 and the fourth 6KV power equipment switch cabinet 12 are respectively connected with the protection system control cabinet 3 in a hard-wired mode.

The air preheater shutdown protection subsystem specifically comprises:

the air preheater shutdown protection subsystem comprises: fifth NOT gate logic gate 24, third Low edge decision logic gate 25, third AND gate logic gate 30, sixth NOT gate logic gate 26, fourth Low edge decision logic gate 27, fourth AND gate logic gate 31, fifth AND gate logic gate 32, fifth two-out-of-three gate logic gate 28, sixth two-out-of-three gate logic gate 29, first OR gate logic gate 33, sixth AND gate logic gate 34, seventh NOT gate logic gate 53, fifth Low edge decision logic gate 54, eighth NOT gate logic gate 55, sixth Low edge decision logic gate 56, eighth AND gate logic gate 57, ninth AND gate logic gate 58, tenth AND gate logic gate 59, and fourth OR gate logic gate 60;

the air preheater off protection subsystem connection is connected to MFT logic loop 48 through sixth and gate logic gate 34; the air preheater off-line protection subsystem is positioned in the protection system control cabinet 3;

the air pre-conditioner shutdown protection subsystem is simultaneously connected with an air pre-conditioner main motor control cabinet 18, a third current transmitter 19, an air pre-conditioner auxiliary motor control cabinet 20, a fourth current transmitter 21, a first air pre-conditioner shutdown detection device 22 and a second air pre-conditioner shutdown detection device 23;

The first air preheater main motor control cabinet 18 sends out a first main motor running signal, and the first main motor running signal is judged by the fifth NOT gate logic gate 24 to obtain a first main motor stopping signal;

the third current signal sent by the third current transducer 19 is judged by the third low limit judgment logic gate 25, so as to obtain a signal that the third current is lower than a fixed value; the third current lower than a fixed value signal and the first main motor stop signal are judged through a third AND gate logic gate 30, so that a first air preheater main motor stop signal is obtained;

the first air preheater auxiliary motor control cabinet 20 sends a first auxiliary motor running signal, and the first auxiliary motor running signal is judged through the sixth NOT gate logic gate 26 to obtain a first auxiliary motor stop signal;

the fourth current signal sent by the fourth current transducer 21 is judged by the fourth low limit judgment logic gate 27, so as to obtain a signal that the fourth current is lower than a fixed value; the signal that the fourth current is lower than a fixed value and the signal that the first auxiliary motor stops are judged through a fourth AND gate logic gate 31, so that a signal that the first air preheater is stopped for the auxiliary motor is obtained;

the first air preheater main motor outage signal and the first air preheater auxiliary motor outage signal are subjected to a fifth AND gate logic gate 32 to obtain a first air preheater motor outage signal;

The first air preheater stall detection device 22 sends out three signals of low rotation speed of the first air preheater, and the three signals of low rotation speed of the first air preheater are judged through a fifth two-out-of-three logic gate 28 to obtain a signal of stall of the first air preheater; the first air preheater stopping signal and the first air preheater motor stopping signal are judged through a first OR gate logic gate 33, so that a first air preheater stopping signal is obtained;

the second air preheater main motor control cabinet 49 sends out a second main motor running signal, and the second main motor running signal is judged by the seventh NOT gate logic gate 53 to obtain a second main motor stop signal;

the fifth current signal sent by the fifth current transducer 50 is judged by the fifth low limit judgment logic gate 54, so as to obtain a fifth current lower than a fixed value signal; the fifth current lower than a fixed value signal and the second main motor stop signal are judged through an eighth AND gate logic gate 57 to obtain a second air preheater main motor stop signal;

the second air preheater auxiliary motor control cabinet 51 sends out a second auxiliary motor running signal, and the second auxiliary motor running signal is judged by the eighth NOT gate logic gate 55 to obtain a second auxiliary motor stop signal;

The sixth current signal sent by the sixth current transducer 52 is judged by the sixth low limit judgment logic gate 56, so as to obtain a signal that the sixth current is lower than a fixed value; the signal that the sixth current is lower than the fixed value and the signal that the second auxiliary motor stops are judged through a ninth AND gate logic gate 58, so as to obtain a signal that the second air preheater auxiliary motor stops;

the second air preheater main motor shutdown signal and the second air preheater auxiliary motor shutdown signal obtain a second air preheater motor shutdown signal through a tenth AND gate logic gate 59;

the second air preheater stall detection device 23 sends out three signals of low rotation speed of the second air preheater, and the three signals of low rotation speed of the second air preheater are judged through a sixth two-out-of-three logic gate 29 to obtain a signal of second air preheater stall; the second air preheater stop signal and the second air preheater motor stop signal are judged through a fourth OR gate logic gate 60, so that a second air preheater stop signal is obtained;

the first air preheater stop signal and the second air preheater stop signal are judged through a sixth AND gate logic gate 34, and an air preheater full stop signal is obtained; the air preheater complete stop signal is transmitted to the MFT logic loop to trigger the MFT protection action.

The first air preheater stall detection device 22 is connected with the first air preheater; the second air pre-conditioner stall detection 23 is connected to the second air pre-conditioner.

The furnace pressure protection subsystem comprises: a three-side furnace pressure measuring point protection subsystem and a double-side furnace pressure measuring point protection subsystem;

the three-side furnace pressure measuring point protection subsystem and the two-side furnace pressure measuring point protection subsystem are simultaneously connected with the boiler;

the protection subsystem of the pressure measuring point of the double-side furnace comprises the following components:

the first pressure measuring device 35, the second pressure measuring device 36, the third pressure measuring device 37 and the fourth pressure measuring device 38 are simultaneously connected with the double-side furnace pressure measuring point protection subsystem;

the first 35 and second 36 pressure measuring devices are located on one side of the boiler, and the third 37 and fourth 38 pressure measuring devices are located on the other side of the boiler;

the first pressure measuring device 35 and the second pressure measuring device 36 respectively send a first furnace pressure signal and a second furnace pressure signal, and the first furnace pressure signal and the second furnace pressure signal are judged through a second OR gate logic gate 39 after passing through the protection system control cabinet 3 to obtain a first pressure signal;

the third pressure measuring device 37 and the fourth pressure measuring device 38 respectively send out a third furnace pressure signal and a fourth furnace pressure signal, and the third furnace pressure signal and the fourth furnace pressure signal are judged through a third OR gate logic gate 40 after passing through the protection system control cabinet 3 to obtain a second pressure signal;

The "first pressure" signal and the "second pressure" signal are judged by the seventh and gate logic gate 41, so as to obtain "first furnace pressure" information, and the "first furnace pressure" information enters the MFT logic loop to trigger the MFT protection action.

The three-side furnace pressure measuring point protection subsystem specifically comprises:

the fifth pressure measuring device 42, the sixth pressure measuring device 43 and the seventh pressure measuring device 44 are simultaneously connected with the three-side furnace pressure measuring point protection subsystem;

the fifth pressure measuring device 42, the sixth pressure measuring device 43 and the seventh pressure measuring device 44 respectively send out a fifth furnace pressure signal, a sixth furnace pressure signal and a seventh furnace pressure signal, and the fifth furnace pressure signal, the sixth furnace pressure signal and the seventh furnace pressure signal are judged through a seventh two-out-of-three logic gate 45 to obtain second furnace pressure information, and the second furnace pressure information enters an MFT logic loop to trigger MFT protection action.

A method for improving reliability of an MFT protection system of a thermal power generating unit boiler comprises the following steps:

the logical judgment mode of 'three taking two' is formed by adopting a 'switch closing non', 'switch opening', 'current is lower than a fixed value':

the first 6KV power equipment switch cabinet 1 sends a first switch closing signal and a first switch opening signal, the first switch closing signal is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS system switching value input card (DI point), and the first switch closing signal is inverted through the first NOT gate logic gate 2 to obtain a first switch closing NOT signal; the first current signal sent by the first current transmitter 46 is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS analog input card (AI point), and the first current signal is judged by the first low-limit judgment gate 4 to obtain a signal that the first current is lower than a fixed value; the first switch opening signal, the first switch closing non signal and the first current lower than a fixed value signal are judged through a first three-out-of-two logic gate 5, and a first power equipment outage signal is obtained;

The second 6KV power equipment switch cabinet 7 sends out two signals of a second switch closing signal and a second switch opening signal, the second switch closing signal is connected into the protection system control cabinet 3 in a hard-wired mode through a DCS system switching value input card (DI point), and the second switch closing signal is inverted through the second NOT gate logic gate 8 to obtain a second switch closing NOT signal; the second current signal sent by the second current transmitter 47 is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS analog input card (AI point), and the second current signal is judged by a second low-limit judgment gate 9 to obtain that the second current is lower than a fixed value; the second switch opening signal, the second switch closing non signal and the second current lower than a fixed value signal are judged through a second three-out-of-two logic gate 10, and a second power equipment outage signal is obtained;

the first power equipment outage signal and the second power equipment outage signal are transmitted to an MFT logic loop through a first AND gate logic gate 6 to obtain a first power equipment complete outage signal, and the first power equipment complete outage signal is transmitted to an MFT logic loop to trigger an MFT protection action; the method for processing the input signals and the logic processing method solve the problem that communication faults affect transmission of protection signals, and greatly improve the protection reliability.

The three-out-of-two logic judgment mode is realized by adopting a switch opening signal:

the third 6KV power equipment switch cabinet 11 sends three third switch closing signals, the three third switch closing signals are connected into the protection system control cabinet 3 in a hard-wired mode through a DCS system switching value input card (DI point), the three third switch closing signals are judged through a third NOT gate logic gate to obtain three third switch closing NOT signals, and the three third switch closing NOT signals are judged through a third two-out logic gate 14 to obtain a third power equipment outage signal;

the fourth 6KV power equipment switch cabinet 12 sends three fourth switch closing signals, the three fourth switch closing signals are connected into the protection system control cabinet 3 in a hard-wired mode through a DCS system switching value input card (DI point), the three fourth switch closing signals are judged through a fourth NOT gate logic gate 15 to obtain three fourth switch Guan Gezha NOT signals, and the three fourth switch Guan Gezha NOT signals are judged through a fourth two-out-of-three logic gate 16 to obtain a fourth power equipment shutdown signal;

the third power equipment outage signal and the fourth power equipment outage signal are judged through a second AND gate logic gate 17, and a second power equipment complete outage signal is obtained; the second power equipment complete stop signal is transmitted to the MFT logic loop to trigger the MFT protection action; the invention adopts the input signal mode and the logic processing process, can thoroughly solve the problem that the power failure of the switch affects the protection action, and greatly improves the protection reliability.

The shutdown protection method of the air preheater comprises the following steps:

the first air preheater main motor control cabinet 18 sends out a first main motor running signal, and is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS switching value input card (DI point); the "first main motor running" signal is judged by the fifth NOT gate logic gate 24, and a "first main motor stop" signal is obtained;

the third current signal sent by the third current transducer 19 is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS analog input card (AI point), and the third current signal is judged by a third low-limit judgment logic gate 25 to obtain a signal that the third current is lower than a fixed value; the third current lower than a fixed value signal and the first main motor stop signal are judged through a third AND gate logic gate 30, so that a first air preheater main motor stop signal is obtained;

the first air preheater auxiliary motor control cabinet 20 sends out a first auxiliary motor running signal, and is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS switching value input card (DI point); the "first auxiliary motor running" signal is judged by the sixth NOT gate logic gate 26, and a "first auxiliary motor stop" signal is obtained;

the fourth current signal sent by the fourth current transducer 21 is connected with the protection system control cabinet 3 in a hard-wired mode through a DCS analog input card (AI point), and the fourth current signal is judged by a fourth low-limit judgment logic gate 27, so that a signal that the fourth current is lower than a fixed value is obtained; the signal that the fourth current is lower than a fixed value and the signal that the first auxiliary motor stops are judged through a fourth AND gate logic gate 31, so that a signal that the first air preheater is stopped for the auxiliary motor is obtained;

the first air preheater stall detection device 22 sends three signals of low rotation speed of the first air preheater, the three signals of low rotation speed of the first air preheater are connected into the protection system control cabinet 3 through a DCS system switch value input card (DI point) hard wire, and the three signals of low rotation speed of the first air preheater are judged through a fifth three-out-two logic gate 28 to obtain signals of stall of the first air preheater; the first air preheater stopping signal and the first air preheater motor stopping signal are judged through a first OR gate logic gate 33, so that a first air preheater stopping signal is obtained;

the second air preheater stall detection device 23 sends out three signals of low rotation speed of the second air preheater, the three signals of low rotation speed of the second air preheater are connected into the protection system control cabinet 3 through a DCS system switching value input card (DI point) hard wire, and the three signals of low rotation speed of the second air preheater are judged through a sixth two-out-of-three logic gate 29 to obtain signals of low rotation speed of the second air preheater; the second air preheater stop signal and the second air preheater motor stop signal are judged through a fourth OR gate logic gate 60, so that a second air preheater stop signal is obtained;

According to the invention, through additionally arranging the first air preheater stall detection device and the second air preheater stall detection device, the problem that the air preheater coupling is damaged and the like can be solved, and the special working conditions that the air preheater main motor and the air preheater auxiliary motor are still running can be solved, so that the protection is applicable to various working conditions, and the protection reliability is greatly improved.

The hearth pressure height protection method comprises the following steps:

because of the differences of the boiler types and design schemes, some boiler pressure measuring devices are designed and arranged on two sides of the hearth, and some boiler pressure measuring devices are designed and arranged on three sides of the hearth, the boiler pressure protection logic should adopt different logic judgment modes according to different conditions of the arrangement of the boiler pressure measuring devices.

The first pressure measuring device 35 and the second pressure measuring device 36 are connected with the protection system control cabinet 3 in a hard-wired mode through a switching value input card (DI point) of the DCS system,

the first pressure measuring device 35 and the second pressure measuring device 36 respectively send out a first furnace pressure signal and a second furnace pressure signal, and the first furnace pressure signal and the second furnace pressure signal are judged through the second or gate 39 to obtain a first pressure signal; the "first furnace pressure" signal and the "second furnace pressure" signal are both high or both low. When the first furnace pressure signal and the second furnace pressure signal are high at the same time, the first pressure signal is high; when both the "first furnace pressure" signal and the "second furnace pressure" signal are low, the "first pressure" signal is low.

The third pressure measuring device 37 and the fourth pressure measuring device 38 are connected with the protection system control cabinet 3 in a hard-wired mode through a DCS switching value input card (DI point);

the third pressure measuring device 37 and the fourth pressure measuring device 38 respectively send out a third furnace pressure signal and a fourth furnace pressure signal, and the third furnace pressure signal and the fourth furnace pressure signal are judged through a third OR gate logic gate 40 to obtain a second pressure signal; the third furnace pressure signal and the fourth furnace pressure signal are simultaneously high or simultaneously low; when the third furnace pressure signal and the fourth furnace pressure signal are high at the same time, the second pressure signal is high; when the third and fourth furnace pressure signals are simultaneously low, the second pressure signal is low.

The first pressure signal and the second pressure signal are judged through a seventh AND gate logic gate 41 to obtain first furnace pressure information, and the first furnace pressure information enters an MFT logic loop to trigger MFT protection action;

the fifth pressure measuring device 42, the sixth pressure measuring device 43 and the seventh pressure measuring device 44 are hard-wired into the protection system control cabinet 3 via a DCS system switching value input card (DI point).

The fifth pressure measuring device 42, the sixth pressure measuring device 43 and the seventh pressure measuring device 44 respectively send out a fifth furnace pressure signal, a sixth furnace pressure signal and a seventh furnace pressure signal, and the fifth furnace pressure signal, the sixth furnace pressure signal and the seventh furnace pressure signal are judged through a seventh two-out-of-three logic gate 45 to obtain second furnace pressure information, and the second furnace pressure information enters an MFT logic loop to trigger MFT protection action. The fifth furnace pressure signal, the sixth furnace pressure signal and the seventh furnace pressure signal can be respectively high or low, and the high or low furnace pressure signal is output through the three-out-two logic judgment. The invention adopts the mode of the input signal of the boiler pressure protection system and the signal logic processing process, and can avoid the problem of MFT protection misoperation caused by instantaneous fluctuation of single-side pressure due to combustion ash collapse, coke falling and other reasons.

The fan in the invention can be a primary fan, a blower, a draught fan and the like.

Wherein, "DCS" is Distributed Control System and "MFT" is Main Fuel Trip, "DO" is Digital output and DI "is Digital input, and" AI "is Analog input and RB is Runback and rapid load reduction.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for improving MFT protection reliability of a thermal power generating unit boiler, comprising: the system comprises a fan outage protection subsystem, a first 6KV power equipment switch cabinet (1), a second 6KV power equipment switch cabinet (7), a first current transducer (46), a second current transducer (47), a third 6KV power equipment switch cabinet (11), a fourth 6KV power equipment switch cabinet (12), an MFT logic loop (48) and a protection system control cabinet (3);

the fan outage protection subsystem and the MFT logic loop (48) are positioned in the protection system control cabinet (3);

the fan outage protection subsystem comprises: the first logic judgment protection subsystem and the second logic judgment protection subsystem; the first logic judgment protection subsystem and the second logic judgment protection subsystem are connected through an MFT logic loop (48);

the first logic judgment protection subsystem comprises: the first NOT gate logic gate (2), the second NOT gate logic gate (8), the first low limit judgment gate (4), the second low limit judgment gate (9), the first two-out-of-three logic gate (5), the second two-out-of-three logic gate (10) and the first AND gate logic gate (6);

The second logic judgment protection subsystem comprises: a third NOT gate logic gate (13), a third two-out-of-three gate logic gate (14), a fourth NOT gate logic gate (15), a fourth two-out-of-three gate logic gate (16) and a second AND gate logic gate (17);

the first low limit judgment gate (4) and the first NOT gate logic gate (2) are simultaneously connected with a first three-out-of-two logic gate (5); the second NOT gate logic gate (8) and the second low limit judgment gate (9) are connected with a second three-out-of-two logic gate (10); the second three-out-of-two logic gate (10) and the first three-out-of-two logic gate (5) are simultaneously connected with the first AND gate logic gate (6);

the third NOT gate logic gate (13) is connected with a third two-out-of-three logic gate (14); the fourth NOT logic gate (15) is connected with a fourth two-out-of-three logic gate (16); the third two-out-of-three logic gate (14) and the fourth two-out-of-three logic gate (16) are simultaneously connected with a second AND gate logic gate (17); the first AND gate logic gate (6) and the second AND gate logic gate (17) are connected with an MFT logic loop (48);

the first logic judgment protection subsystem is simultaneously connected with a first 6KV power equipment switch cabinet (1), a second 6KV power equipment switch cabinet (7), a first current transmitter (46) and a second current transmitter (47);

the first 6KV power equipment switch cabinet (1) is respectively connected with a first three-out-of-two logic gate (5) and a first NOT logic gate (2); the first current transducer (46) is connected with a first low limit judgment gate (4);

The third 6KV power equipment switch cabinet (11) and the fourth 6KV power equipment switch cabinet (12) are simultaneously connected with a second logic judgment protection subsystem;

the third 6KV power equipment switch cabinet (11) is connected with a third NOT gate logic gate (13); the fourth 6KV power equipment switch cabinet (12) is connected with a fourth NOT gate logic gate (15);

the first 6KV power equipment switch cabinet (1), the second 6KV power equipment switch cabinet (7), the first current transmitter (46), the second current transmitter (47), the third 6KV power equipment switch cabinet (11) and the fourth 6KV power equipment switch cabinet (12) are respectively connected with the protection system control cabinet (3) in a hard-wired mode.

2. The system for improving the MFT protection reliability of a thermal power generating unit boiler according to claim 1, further comprising an air preheater shutdown protection subsystem; the air preheater shutdown protection subsystem comprises: a fifth not gate logic gate (24), a third low limit judgment logic gate (25), a third and gate logic gate (30), a sixth not gate logic gate (26), a fourth low limit judgment logic gate (27), a fourth and gate logic gate (31), a fifth and gate logic gate (32), a fifth two-out-of-three gate logic gate (28), a sixth two-out-of-three gate logic gate (29), a first or gate logic gate (33), a sixth and gate logic gate (34), a seventh not gate logic gate (53), a fifth low limit judgment logic gate (54), an eighth not gate logic gate (55), a sixth low limit judgment logic gate (56), an eighth and gate logic gate (57), a ninth and gate logic gate (58), a tenth and gate logic gate (59), and a fourth or gate logic gate (60);

The air preheater shutdown protection subsystem is connected with an MFT logic loop (48) through a sixth AND gate logic gate (34); the air preheater off-line protection subsystem is positioned in the protection system control cabinet (3);

the third low limit judgment logic gate (25) and the fifth NOT gate logic gate (24) are simultaneously connected with a third AND gate logic gate (30); the fourth low limit judgment logic gate (27) and the sixth NOT gate logic gate (26) are simultaneously connected with a fourth AND gate logic gate (31); the third AND gate logic gate (30) and the fourth AND gate logic gate (31) are simultaneously connected with a fifth AND gate logic gate (32); the fifth two-out-of-three logic gate (28) and the fifth AND gate logic gate (32) are simultaneously connected with the first OR gate logic gate (33);

the seventh NOT gate logic gate (53) and the fifth low limit judgment logic gate (54) are connected with an eighth AND gate logic gate (57); the eighth NOT gate logic gate (55) and the sixth low limit judgment logic gate (56) are connected with a ninth AND gate logic gate (58); the ninth AND gate logic gate (58) and the eighth AND gate logic gate (57) are simultaneously connected with a tenth AND gate logic gate (59); the sixth two-out-of-three logic gate (29) and the tenth AND gate logic gate (59) are connected with a fourth OR gate logic gate (60) at the same time;

the first or gate logic gate (33) and the fourth or gate logic gate (60) are connected together to a sixth or gate logic gate (34).

3. The system for improving the MFT protection reliability of a thermal power generating unit boiler according to claim 1, further comprising a furnace pressure protection subsystem, wherein the furnace pressure protection subsystem further comprises a three-side furnace pressure measuring point protection subsystem and a double-side furnace pressure measuring point protection subsystem;

the hearth pressure protection subsystem is positioned in the protection system control cabinet (3);

the two-side furnace pressure measuring point protection subsystem and the three-side furnace pressure measuring point protection subsystem are simultaneously connected with an MFT logic loop (48);

the double-side furnace pressure measuring point protection subsystem comprises a second or gate logic gate (30), a third or gate logic gate (40) and a seventh or gate logic gate (41);

the second or gate logic gate (39) and the third or gate logic gate (40) are connected with a seventh or gate logic gate (41);

the seventh AND gate logic gate (41) is connected with an MFT logic loop (48);

the three-side furnace pressure measuring point protection subsystem comprises: a seventh two-out-of-three logic gate (45);

the seventh two-out-of-three logic gate (45) is connected to the MFT logic loop (48).

4. The system for improving MFT protection reliability of a thermal power generating unit boiler according to claim 2, further comprising: the air preheater comprises a first air preheater main motor control cabinet (18), a third current transmitter (19), a first air preheater auxiliary motor control cabinet (20), a fourth current transmitter (21), a first air preheater stall detection device (22), a second air preheater main motor control cabinet (49), a fifth current transmitter (50), a second air preheater auxiliary motor control cabinet (51), a sixth current transmitter (52) and a second air preheater stall detection device (23);

The air pre-heater shutdown protection subsystem is simultaneously connected with a first air pre-heater main motor control cabinet (18), a third current transmitter (19), a first air pre-heater auxiliary motor control cabinet (20), a fourth current transmitter (21), a first air pre-heater shutdown detection device (22), a second air pre-heater main motor control cabinet (49), a fifth current transmitter (50), a second air pre-heater auxiliary motor control cabinet (51), a sixth current transmitter (52) and a second air pre-heater shutdown detection device (23);

the first air preheater main motor control cabinet (18) is connected with a fifth NOT gate logic gate (24); the third current transducer (19) is connected with a third low limit judgment logic gate (25);

the first air preheater auxiliary motor control cabinet (20) is connected with a sixth NOT gate logic gate (26); the fourth current transducer (21) is connected with a fourth low limit judgment logic gate (27);

the first air preheater stall detection device (22) is connected with a fifth two-out-of-three logic gate (28);

the second air preheater main motor control cabinet (49) is connected with a seventh NOT gate logic gate (53); the fifth current transducer (50) is connected with a fifth low limit judgment logic gate (54);

the second air preheater auxiliary motor control cabinet (51) is connected with an eighth NOT gate logic gate (55); the sixth current transducer (52) is connected with a sixth low limit judgment logic gate (56);

The second air preheater stall detection device (23) is connected with a sixth two-out-of-three logic gate (29);

the air preheater motor control cabinet (18), the third current transmitter (19), the first air preheater auxiliary motor control cabinet (20), the fourth current transmitter (21), the first air preheater stall detection device (22), the second air preheater main motor control cabinet (49), the fifth current transmitter (50), the second air preheater auxiliary motor control cabinet (51), the sixth current transmitter (52) and the second air preheater stall detection device (23) are respectively connected with the protection system control cabinet (3) in a hard-wired mode.

5. A system for improving MFT protection reliability of a thermal power plant boiler according to claim 3, further comprising: a first pressure measuring device (35), a second pressure measuring device (36), a third pressure measuring device (37), a fourth pressure measuring device (38), a fifth pressure measuring device (42), a sixth pressure measuring device (43) and a seventh pressure measuring device (44);

the first pressure measuring device (35), the second pressure measuring device (36), the third pressure measuring device (37) and the fourth pressure measuring device (38) are simultaneously connected with the double-side furnace pressure measuring point protection subsystem;

the fifth pressure measuring device (42), the sixth pressure measuring device (43) and the seventh pressure measuring device (44) are simultaneously connected with the three-side furnace pressure measuring point protection subsystem;

The first pressure measuring device (35) and the second pressure measuring device (36) are simultaneously connected with a second OR gate logic gate (39);

the third pressure measuring device (37) and the fourth pressure measuring device (38) are simultaneously connected with a third OR gate logic gate (40);

the fifth pressure measuring device (42), the sixth pressure measuring device (43) and the seventh pressure measuring device (44) are simultaneously connected with a seventh three-out-of-two logic judging gate (45);

the first pressure measuring device (35), the second pressure measuring device (36), the third pressure measuring device (37), the fourth pressure measuring device (38), the fifth pressure measuring device (42), the sixth pressure measuring device (43) and the seventh pressure measuring device (44) are respectively connected with the protection system control cabinet (3) in a hard-wired mode.

6. The system for improving the MFT protection reliability of a thermal power generating unit boiler according to claim 4, wherein the first air preheater stall detection device (22) and the second air preheater stall detection device (23) are each three sets.

7. A method for improving MFT protection reliability of a thermal power generating unit boiler according to claim 1, comprising:

a first 6KV power equipment switch cabinet (1) sends a first switch closing signal and a first switch opening signal, and the first switch closing signal is inverted through a first NOT gate logic gate (2) to obtain a first switch closing NOT signal; a first current signal sent by a first current transducer (46) is judged by a first low limit judgment gate (4) to obtain a signal that the first current is lower than a fixed value; the first switch opening signal, the first switch closing non signal and the first current lower than a fixed value signal are judged through a first three-out-of-two logic gate (5) to obtain a first power equipment outage signal;

A second 6KV power equipment switch cabinet (7) sends out two signals of a second switch closing signal and a second switch opening signal, and the second switch closing signal is inverted through a second NOT gate logic gate (8) to obtain a second switch closing NOT signal; the second current signal sent by the second current transducer (47) is judged by a second low limit judgment gate (9) to obtain that the second current is lower than a fixed value; the second switch opening signal, the second switch closing non signal and the second current lower than a fixed value signal are judged through a second three-out-of-two logic gate (10) to obtain a second power equipment outage signal;

the first power equipment outage signal and the second power equipment outage signal are transmitted to an MFT logic loop through a first AND gate logic gate (6) to obtain a first power equipment complete outage signal, and the first power equipment complete outage signal is transmitted to the MFT logic loop to trigger an MFT protection action;

the third 6KV power equipment switch cabinet (11) sends three third switch closing signals, the three third switch closing signals are judged through a third NOT gate logic gate (13) to obtain three third switch closing NOT signals, and the three third switch closing NOT signals are judged through a third two-out-of-three logic gate (14) to obtain a third power equipment shutdown signal;

The fourth 6KV power equipment switch cabinet (12) sends three fourth switch closing signals, the three fourth switch closing signals are judged through a fourth NOT gate logic gate (15) to obtain three fourth switch Guan Gezha NOT signals, and the three fourth switch Guan Gezha NOT signals are judged through a fourth three-out-of-two logic gate (16) to obtain a fourth power equipment shutdown signal;

the third power equipment outage signal and the fourth power equipment outage signal are judged through a second AND gate logic gate (17) to obtain a second power equipment complete outage signal; the "second power device full stop" signal is sent to the MFT logic loop to trigger MFT protection actions.

8. A method for improving MFT protection reliability of a thermal power plant boiler according to claim 4, comprising:

the first air preheater main motor control cabinet (18) sends a first main motor running signal, and the first main motor running signal is judged through a fifth NOT gate logic gate (24) to obtain a first main motor stopping signal;

a third current signal sent by a third current transducer (19) is judged by a third low limit judgment logic gate (25) to obtain a signal that the third current is lower than a fixed value; the third current lower than the fixed value signal and the first main motor stop signal are judged through a third AND gate logic gate (30) to obtain a first air preheater main motor stop signal;

The first air preheater auxiliary motor control cabinet (20) sends a first auxiliary motor running signal, and the first auxiliary motor running signal is judged through a sixth NOT gate logic gate (26) to obtain a first auxiliary motor stop signal;

a fourth current signal sent by a fourth current transducer (21) is judged by a fourth low limit judgment logic gate (27) to obtain a signal that the fourth current is lower than a fixed value; the fourth current lower than a fixed value signal and the first auxiliary motor stop signal are judged through a fourth AND gate logic gate (31) to obtain a first air preheater auxiliary motor stop signal;

the first air preheater main motor outage signal and the first air preheater auxiliary motor outage signal are subjected to a fifth AND gate logic gate (32) to obtain a first air preheater motor outage signal;

the first air preheater stall detection device (22) sends three signals of low rotation speed of the first air preheater, and the three signals of low rotation speed of the first air preheater are judged through a fifth two-out-of-three logic gate (28) to obtain a signal of stall of the first air preheater; judging a first air preheater stop signal and a first air preheater motor stop signal through a first OR gate logic gate (33) to obtain a first air preheater stop signal;

A second air preheater main motor control cabinet (49) sends a second main motor running signal, and the second main motor running signal is judged through a seventh NOT gate logic gate (53) to obtain a second main motor stop signal;

a fifth current signal sent by a fifth current transducer (50) is judged by a fifth low limit judgment logic gate (54) to obtain a fifth current signal lower than a fixed value; the fifth current lower than a fixed value signal and the second main motor stop signal are judged through an eighth AND gate logic gate (57) to obtain a second air preheater main motor stop signal;

the second air preheater auxiliary motor control cabinet (51) sends a second auxiliary motor running signal, and the second auxiliary motor running signal is judged through an eighth NOT gate logic gate (55) to obtain a second auxiliary motor stop signal;

a sixth current signal sent by a sixth current transducer (52) is judged by a sixth low limit judgment logic gate (56) to obtain a signal that the sixth current is lower than a fixed value; the signal that the sixth current is lower than a fixed value and the signal that the second auxiliary motor stops are judged through a ninth AND gate logic gate (58) to obtain a signal that the second air preheater auxiliary motor stops;

The second air preheater main motor outage signal and the second air preheater auxiliary motor outage signal are subjected to a tenth AND gate logic gate (59) to obtain a second air preheater motor outage signal;

the second air preheater stall detection device (23) sends out three signals of low rotation speed of the second air preheater, and the three signals of low rotation speed of the second air preheater are judged through a sixth two-out-of-three logic gate (29) to obtain a signal of second air preheater stall; judging the second air preheater stop signal and the second air preheater motor stop signal through a fourth OR gate logic gate (60) to obtain a second air preheater stop signal;

judging the first air preheater stop signal and the second air preheater stop signal through a sixth AND gate logic gate (34) to obtain an air preheater full stop signal; the air preheater complete stop signal is transmitted to the MFT logic loop to trigger the MFT protection action.

9. A method for improving MFT protection reliability of a thermal power plant boiler according to claim 5, comprising:

the first pressure measuring device (35) and the second pressure measuring device (36) respectively send a first furnace pressure signal and a second furnace pressure signal, and the first furnace pressure signal and the second furnace pressure signal are judged through a second OR gate logic gate (39) to obtain a first pressure signal;

The third pressure measuring device (37) and the fourth pressure measuring device (38) respectively send a third furnace pressure signal and a fourth furnace pressure signal, and the third furnace pressure signal and the fourth furnace pressure signal are judged through a third OR gate logic gate (40) to obtain a second pressure signal;

the first pressure signal and the second pressure signal are judged through a seventh AND gate logic gate (41) to obtain first furnace pressure information, and the first furnace pressure information enters an MFT logic loop to trigger MFT protection action;

the fifth pressure measuring device (42), the sixth pressure measuring device (43) and the seventh pressure measuring device (44) respectively send a fifth furnace pressure signal, a sixth furnace pressure signal and a seventh furnace pressure signal, the fifth furnace pressure signal, the sixth furnace pressure signal and the seventh furnace pressure signal are judged through a seventh two-out-of-three logic judging gate (45), so that second furnace pressure information is obtained, the second furnace pressure information enters an MFT logic loop, and MFT protection action is triggered.