CN103427479B - Method for switching safety power sources of power plant on basis of DCS (distributed control system) - Google Patents

Abstract

The invention relates to a method for switching safety power sources of a power plant on the basis of a DCS (distributed control system). The method includes steps of (1), inputting states of bus protection devices configured on safety sections in the power plants, protection outlets of overcurrent protection devices configured on circuit breakers, position junctions of the circuit breakers and diesel-driven generators into the DCS of the power plant and performing logical configuration; (2), enabling the DCS to judge switching values after logical configuration according to the importance of load, controlling the circuit breakers and the diesel-driven generators, and transmitting load starting instructions in batches to switch the safety power sources so that the important load on the safety power sources can be automatically recovered and run. The method has the advantages that 'voltage loss' and 'permanent faults' can be judged, so that the safety power sources can be reliably switched, existing devices of the power plant are sufficiently utilized to achieve the purpose of switching the safety power sources, and the cost is saved.

Description

DCS-Based Switching Method of Safe Power Source in Power Plant

technical field

The invention belongs to the technical field of unit automatic power generation control, in particular to a DCS-based power plant security power switching method.

Background technique

In the case of power failure of the whole plant, in order to ensure the normal shutdown of the generator set and avoid damage to the equipment, it is necessary to ensure that some important loads of the power plant can be continuously powered, such as: air preheater motor, fire detection cooling fan, AC sealed oil pump, Lubricating oil pump and other loads to ensure that the unit can be shut down safely. The current practice is to connect these important loads to the "safety section". The load is switched through the standby automatic switching device to prevent power loss in the "safety section". 1. The current method mostly adopts the introduction of standby automatic switching device to realize the switching of security power supply, but the standby automatic switching device can only control the switch on the power side according to the voltage and current criteria, and cannot realize the self-starting of important loads after the bus voltage is restored. At the same time, this method requires the purchase of self-injection protection devices, which increases costs; 2. DCS is the abbreviation of Distributed Control System (Distributed Control System), which is a process control level and a process monitoring level. The communication network is the link The multi-level computer system can realize decentralized control, centralized operation, hierarchical management, flexible configuration and convenient configuration. However, purely relying on DCS logic to achieve switching also has its obvious disadvantages. Since the voltage and current collected in the DCS system are all 4-20mA quantities provided by the transmitter, the reliability, accuracy and fault transient characteristics of the sampling are high. It is not as good as traditional protection and automatic devices, so it is not as accurate as traditional protection and automatic devices in terms of logical judgments such as "permanent failure" and "low voltage action" based on voltage, current and switching values.

Contents of the invention

The purpose of the present invention is to provide a DCS-based power plant security power switching method for the deficiencies of the prior art.

The present invention solves its technical problem and realizes by taking the following technical solutions:

A DCS-based power plant security power switching method, the method steps are as follows:

(1) Introduce the bus protection device configured on the security section of the power plant and the protection outlet of the overcurrent protection device configured on the circuit breaker, the position contact of the circuit breaker and the state of the diesel generator into the DCS system of the power plant for logical configuration;

⑵The DCS system controls the circuit breaker and diesel generator according to the importance of the load, through the judgment of the switching value after the logic configuration, and issues instructions to start the load in batches, so as to realize the switching of the security power supply, so that the important load on the security power supply is automatically Resume the operation and maintain the continuous power supply of the bus in the security section.

For units of 300MW and above with A and B two-stage security power switching systems, the steps of the A-section security power switching method are as follows:

(1) Judging the low voltage protection action of the busbar protection of the security section A and the protection action of the circuit breaker DL1 protection device, if both act at the same time, introduce the next step of the method, if the two are only a single action, then end;

⑵ Issue the command to start the diesel generator, and at the same time start the bus switching logic of the security section A;

(3) After starting the bus switching logic of the security section A, implement three-way judgment;

①The first operation: there is no low-voltage protection action on the busbar of the security section B, and DL3 and DL7 are divided, then proceed to step A, otherwise end the first operation;

A. Continue to operate the first channel, issue a skip DL2 command, and judge the DL2 status, if the DL2 status is divided, proceed to step B, otherwise end the first channel operation;

B. Continue to operate the first channel, and issue the merge into DL7 command;

C. Continue to operate the first road, and judge whether the low-voltage protection action of the busbar protection of the security section A disappears. If it disappears, proceed to step D, otherwise end the operation of the first road;

D. Continue to operate the first road, according to the starting characteristics of the motor, respectively implement 0-second starting motor, 15-second starting motor and 30-second starting motor, and the operation is completed;

②The second operation: there is no low-voltage protection action in the security section B, and DL3 is the split position, and DL7 is the close position, then proceed to step A, otherwise end the second operation;

A. Continue to operate the second road, issue a command to skip DL2 and DL7, and judge the status of DL2 and DL7. If the status of DL2 and DL7 is both in place, it means that the diesel engine can be loaded, and then proceed to step B, otherwise, after a 3-minute delay End the second operation;

B. Continue to operate the second channel, and issue the instruction of combining into DL7;

C. Continue to operate the second circuit, and judge whether the low-voltage protection action of the busbar protection in the security section A disappears. If it disappears, proceed to step D, otherwise end the operation of the second circuit;

D. Continue to operate the second circuit. According to the starting characteristics of the motor, start the motor for 0 seconds, start the motor for 15 seconds and start the motor for 30 seconds respectively, and the operation is completed;

③Third operation: No low-voltage protection action for the security section B busbar, and DL3 is closed, ending the third operation.

Advantages and positive effects of the present invention are

1. The present invention can replace the automatic switching protection device, use the existing basic configuration of the power plant to complete the switching of the security power supply, make full use of the existing equipment of the power plant to achieve the purpose of switching the security power supply, and save costs.

2. Compared with the traditional standby automatic switching, the present invention can automatically start important equipment after the power supply is restored in the security section, and realize the automatic control of switching from the security power supply to the important load and restarting the operation.

3. Different from the method of simply relying on DCS logic to realize switching, the present invention uses a more professional protection device to judge "loss of voltage" and "permanent failure", making switching more reliable.

4. The present invention makes full use of the flexible and changeable characteristics of DCS logic to realize the switching mode under different situations such as switch refusal and permanent fault judgment that may occur during the switching process.

5. In view of the fact that DCS has obvious disadvantages compared with professional protection devices in judging low voltage or permanent faults, use low-voltage section low-voltage protection devices and low-voltage section segment protection devices to replace DCS for low-voltage or permanent faults. Distinguish the permanent fault, and send the judgment result to the DCS in the form of a switch, assisting the DCS to make a logical judgment and complete the switching of the security power supply.

Description of drawings

Figure 1 is a schematic diagram of the circuit structure of the A and B two-stage security power switching system of the 300MW and above units;

Fig. 2 is a logical diagram of method steps in section A of the present invention having two sections A and B security power switching system.

Detailed ways

The embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

Fundamental

Introduce the bus protection device configured on the security section of the power plant, the protection outlet of the overcurrent protection device configured on the circuit breaker, the position contact of the circuit breaker and the status of the diesel generator into the DCS (distributed control systems) system of the power plant for logical configuration , Through the judgment of the switching value, control the circuit breaker, diesel generator, etc., realize the switching of the security power supply, and keep the continuous power supply of the busbar in the security section.

When the voltage of the safety power supply is restored, the DCS system will issue commands to start the load in batches according to the importance of the load, so that the important loads on the safety power supply can automatically resume operation and ensure the safe and stable shutdown of the unit.

A DCS-based power plant security power switching method, as shown in Figure 1, the two-stage security power supply is a common mode for large units of 300MW and above, so the switching system with A and B two-stage security power supply is used as an example, and the A section The method is the same as that of section B, and the steps of section A are as follows:

⑴Judge the low-voltage protection action of the A-section busbar protection and the protection action of the circuit breaker DL1 protection device. If both act at the same time, introduce the next step of the method. If the two are only a single action, then end;

⑵ Issue the command to start the diesel generator, and at the same time start the bus switching logic of the security section A;

(3) After starting the bus switching logic of the security section A, implement three-way judgment;

①The first operation: there is no low voltage protection action in the security section B, and DL3 and DL7 are divided, continue the first operation, otherwise end the first operation;

A. Continue to operate the first route, issue a skip DL2 command, judge the DL2 status, if the DL2 status is divided, continue the first route operation, otherwise end the first route operation;

B. Continue to operate the first channel, and issue the merge into DL7 command;

C. Continue to operate the first road, and judge whether the low-voltage protection action of the A-section busbar protection disappears. If it disappears, continue the first road operation, otherwise end the first road operation;

D. Continue to operate the first road, according to the starting characteristics of the motor, respectively implement 0-second starting motor, 15-second starting motor and 30-second starting motor, and the operation is completed;

②The second way of judgment: there is no low-voltage protection action in the security section B, and DL3 is in position, and DL7 is in position, continue the second way of operation, otherwise end the second way of operation;

A. Continue to operate the second road, issue the command to skip DL2 and DL7, and judge the status of DL2 and DL7. If the status of DL2 and DL7 is both in place, it means that the diesel engine can be loaded, and continue to operate the second road. Otherwise, delay for 3 minutes Then end the second operation;

B. Continue to operate the second channel, and issue the instruction of combining into DL7;

C. Continue to operate the second route, and judge whether the low-voltage protection action of the A-section busbar protection disappears, if it disappears, continue the second route operation, otherwise end the second route operation;

D. Continue to operate the second circuit. According to the starting characteristics of the motor, start the motor for 0 seconds, start the motor for 15 seconds and start the motor for 30 seconds respectively, and the operation is completed;

③Third judgment: There is no low-voltage protection action in the security section B, and DL3 is closed, and the third operation is ended.

Claims (1)

1. A DCS-based power plant security power switching method, the method steps are as follows: (1) Introduce the bus protection device configured on the security section of the power plant and the protection outlet of the overcurrent protection device configured on the circuit breaker, the position contact of the circuit breaker and the state of the diesel generator into the DCS system of the power plant for logical configuration; ⑵The DCS system controls the circuit breaker and diesel generator according to the importance of the load, through the judgment of the switching value after the logic configuration, and issues instructions to start the load in batches, so as to realize the switching of the security power supply, so that the important load on the security power supply is automatically resume operation, characterized in that: For units of 300MW and above with A and B two-stage security power switching systems, the steps of the A-section security power switching method are as follows: (1) Judging the low voltage protection action of the busbar protection of the security section A and the protection action of the circuit breaker DL1 protection device, if both act at the same time, introduce the next step of the method, if the two are only a single action, then end; ⑵ Issue the command to start the diesel generator, and at the same time start the bus switching logic of the security section A; (3) After starting the bus switching logic of the security section A, implement three-way judgment; ①The first operation: there is no low-voltage protection action on the busbar of the security section B, and the circuit breaker DL3 is in the sub-position, and the circuit breaker DL7 is in the sub-position, proceed to step A, otherwise end the first operation; A. Continue to operate the first route, issue a command to trip the circuit breaker DL2, judge the state of the circuit breaker DL2, and if the state of the circuit breaker DL2 is divided, proceed to step B, otherwise end the first route operation; B. Continue to operate the first road, and issue the instruction of closing the circuit breaker DL7; C. Continue to operate the first road, and judge whether the low-voltage protection action of the busbar protection of the security section A disappears. If it disappears, proceed to step D, otherwise end the operation of the first road; D. Continue to operate the first road, according to the starting characteristics of the motor, respectively implement 0-second starting motor, 15-second starting motor and 30-second starting motor, and the operation is completed; ②The second operation: there is no low-voltage protection action in the security section B, and the circuit breaker DL3 is in position, and the circuit breaker DL7 is in position, go to step A, otherwise end the second operation; A. Continue to operate the second circuit, issue a command to trip circuit breaker DL2 and circuit breaker DL7, and judge the status of circuit breaker DL2 and circuit breaker DL7. , proceed to step B, otherwise, end the second operation after a 3-minute delay; B. Continue to operate the second road, and issue the instruction of closing the circuit breaker DL7; C. Continue to operate the second circuit, and judge whether the low-voltage protection action of the busbar protection in the security section A disappears. If it disappears, proceed to step D, otherwise end the operation of the second circuit; D. Continue to operate the second circuit. According to the starting characteristics of the motor, start the motor for 0 seconds, start the motor for 15 seconds and start the motor for 30 seconds respectively, and the operation is completed; ③Third-way operation: There is no low-voltage protection action on the busbar of the security section B, and the circuit breaker DL3 is closed, and the third-way operation is ended.