Intelligent control method and system suitable for large main transformer cooler

Abstract

The invention belongs to the technical field of transformer control, and particularly relates to an intelligent control method and system suitable for a large main transformer cooler. The method comprises the following steps: step 1, determining an operation mode of the cooler; 2, determining a cooler control method according to the running state of the cooler; and step 3, according to the PLC, determining an automatic cycle switching control method of the cooler. The PLC technology is adopted to achieve control over the transformer cooling device, optimal judgment can be conducted according to the load and the oil temperature of the transformer, operation of the cooler can be automatically put into or quitted, energy is saved, consumption is reduced, the service life is prolonged, meanwhile, electrical secondary circuit wiring is simplified, the reliability of equipment operation is improved, and the service life is prolonged. And online real-time monitoring of the working state and the fault condition of the main transformer cooler system is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer control, and in particular relates to an intelligent control method and system suitable for a large main transformer cooler. Background Art

[0002] The main transformer is a key electrical equipment in the power plant, which directly affects the power supply reliability of the power system. Once a fault occurs, it not only threatens the safe and stable operation of the power plant and the power grid, but also may cause huge economic losses to production. In order to ensure the safe, stable and economical operation of the transformer, the oil temperature change of the transformer must be monitored in real time, and the cooler control system must control the cooler to cool it. The complete shutdown of the main transformer cooler is a very serious accident in the power system. When the cooler power fails or fails due to other reasons, the cooler will stop completely, causing the main transformer non-electrical protection outlet to cause the main transformer to trip, resulting in more serious consequences such as forced load reduction or even shutdown.

[0003] The traditional main transformer cooler control system adopts a control loop built with intermediate relays, time relays, contactors, etc., which has disadvantages such as high component failure rate, complex control wiring, single cooler control function, and low redundancy. It can no longer meet the safety, reliability, intelligence, and automation requirements of on-site equipment. Summary of the invention

[0004] The object of the present invention is to provide an intelligent control method and system suitable for a large main transformer cooler, which method can fully ensure the reliability and flexibility of the operation of the main transformer cooler control system.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] An intelligent control method applicable to a large main transformer cooler, the method comprising:

[0007] Step 1, determine the cooler operation mode;

[0008] Step 2: Determine the cooler control method according to the cooler operation status;

[0009] Step 3: Determine the automatic cycle switching control method of the cooler according to the PLC.

[0010] The cooler operation mode in step 1 includes: 3 groups of working and 1 group of standby, or 2 groups of working, 1 group of auxiliary and 1 group of standby.

[0011] The step 2 comprises:

[0012] Step 2.1: If the cooler has no faults, determine whether to put the working cooler into operation or cut off the working cooler according to the status of the main transformer or cooler test handle;

[0013] Step 2.2, in case of a fault during the operation of the cooler, the operation of the cooler is determined based on the oil pump operation signal, and the cooler fault is determined based on the fan operation signal negated from the fan fault signal;

[0014] Step 2.3: When all coolers are stopped, determine the longest delayed operation time of the transformer according to the oil level temperature of the transformer. After the delay, the main transformer cooler will be fully stopped and delayed tripped.

[0015] The step 2.1 is specifically as follows: when there is no fault in the cooler, when the main transformer is put into operation or the cooler test handle is put into operation, the working cooler is automatically put into operation; when the main transformer is stopped and the cooler test handle is withdrawn, the working cooler is automatically cut off.

[0016] The step 2.2 is specifically as follows: when the fan operation signal is not equal to the number of fan fault signals = 1, and the oil pump operation signal is present, it is determined that a single fan fault occurs during the operation of the cooler; when the fan operation signal is not equal to the number of fan fault signals ≥ 2, and the oil pump operation signal is present, it is determined that the cooler is faulty during operation; when the 380VAC incoming power supply is lost, and the oil pump operation signal is present, it is determined that the cooler is faulty during operation.

[0017] In the step 2.2, when a single fan drawer is manually pulled out, the fan will not be judged as faulty, ensuring that when one fan is under maintenance, the group of coolers is still available.

[0018] The step 2.3 is specifically as follows: when the main transformer is running at full load, after all coolers have been shut down, when the transformer oil level temperature exceeds 75°C, it is allowed to continue running for 20 minutes; when the transformer oil level temperature does not reach 75°C, it is allowed to rise to 75°C, and the maximum running time allowed after the transformer coolers are removed shall not exceed 1 hour.

[0019] The step 3 is specifically as follows: in the 3-in-1-standby mode, when the cycle switching interlock is put into operation, the standby cooler that is not in operation is started, and after the start-up is successful, a delay of 15 seconds is made, and the originally running group of coolers is stopped, and the status bit is changed; in the 2-in-1-auxiliary-1-standby mode, the cycle switching interlock is put into operation, and the not-in-operation group of auxiliary and group of standby are started, and after the start-up is successful, a delay of 15 seconds is made, and the originally running groups of coolers are stopped, and the status bit is changed.

[0020] An intelligent control system suitable for a large main transformer cooler, the system comprising: 1 PLC master control cabinet and 4 cooler control boxes, the 1 PLC master control cabinet is connected to the 4 cooler control boxes respectively, each cooler control box controls a group of coolers of each A / B / C three-phase transformer, the coolers are connected to the transformer oil tank through a connecting pipe; each group of coolers comprises 3 fans, 1 transformer oil pump and 1 oil flow relay.

[0021] In each group of coolers, one transformer oil pump and three fans are independently controlled by a drawer-type unit, and each motor is protected against short circuit, overload and phase loss.

[0022] The beneficial technical effects of the present invention are:

[0023] The present invention provides an intelligent control method and system suitable for a large main transformer cooler. The PLC technology is used to control the transformer cooling device. The method can make an optimal judgment according to the transformer load size and oil temperature, automatically start or exit the operation of the cooler, save energy and reduce consumption, and increase the service life. At the same time, the electrical secondary circuit wiring is simplified, the reliability of equipment operation is improved, and online real-time monitoring of the working status and fault conditions of the main transformer cooler system is achieved. The PLC and cooling system and the real-time working conditions are clearly visible on the human-computer interaction interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A start-stop logic diagram of a cooler without fault in an intelligent control method for a large main transformer cooler provided by the present invention (taking the first group of coolers of phase A as an example);

[0025] Figure 2 A fault logic diagram of a cooler in operation in an intelligent control method for a large main transformer cooler provided by the present invention (taking the first group of coolers of phase A as an example);

[0026] Figure 3 A cooler linkage logic diagram in an intelligent control method for a large main transformer cooler provided by the present invention (taking the first group of coolers of phase A as an example);

[0027] Figure 4 A cooler interlocking and stopping logic diagram in an intelligent control method for a large main transformer cooler provided by the present invention (taking the first group of coolers of phase A as an example);

[0028] Figure 5 A cooler full stop logic diagram in an intelligent control method applicable to a large main transformer cooler provided by the present invention (taking the A-phase cooler as an example). DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0030] The present invention provides an intelligent control method applicable to a large main transformer cooler, which specifically comprises the following steps:

[0031] Step 1: Determine the cooler operation mode

[0032] During normal operation of the main transformer cooler, the cooler operating status is generally set to 3 groups working and 1 group standby. When the heat dissipation efficiency is high, it is occasionally set to 2 groups working, 1 group auxiliary, and 1 group standby. Considering that the general operating mode of other power plants is 2 groups working, 1 group auxiliary, and 1 group standby, the cooler is configured with two operating modes: "3 in use and 1 standby mode" and "2 in use, 1 auxiliary, and 1 standby mode" to meet various needs.

[0033] Step 2: Determine the cooler control method based on the cooler operating status

[0034] Step 2.1: If the cooler is fault-free, determine whether to put the working cooler into operation or cut off according to the status of the main transformer or cooler test handle.

[0035] If the cooler has no faults, when the main transformer is put into operation or the cooler test handle is turned on, the working cooler is automatically turned on; when the main transformer is stopped and the cooler test handle is turned off, the working cooler is automatically turned off. Figure 1 shown.

[0036] Step 2.2: In case of a cooler failure, determine the cooler operation based on the oil pump operation signal, and determine the cooler failure based on the fan operation signal and the fan failure signal.

[0037] When the fan running signal is not equal to the number of fan fault signals = 1, and the oil pump is running, it is judged that a single fan is faulty during the operation of the cooler; when the fan running signal is not equal to the number of fan fault signals ≥ 2, and the oil pump is running, it is judged that the cooler is faulty during operation; when the 380VAC incoming power supply is lost, and the oil pump is running, it is judged that the cooler is faulty during operation. The fault judgment logic of the cooler operation is as follows: Figure 2 shown.

[0038] When a single fan drawer is manually pulled out, the fan will not be judged as faulty, ensuring that when a fan is under maintenance, the group of coolers can still be used, thereby improving the flexibility of cooler control and reliability in extreme situations.

[0039] Specifically, the fault switching control method during cooler operation is determined according to the cooler operation mode:

[0040] Step 2.2.1, the cooler operation mode is 3 in use and 1 in standby mode (taking phase A of the main transformer as an example), and the fault switching control method during cooler operation is:

[0041] (1) Phase A is over-temperature (>50°C), an alarm is triggered, and no action is taken;

[0042] (2) If the A phase is over-temperature (>75°C), the standby cooler is started; after the temperature drops (<50°C), the standby cooler is stopped;

[0043] (3) If a single fan fails, the standby cooler will be started. For example, after the A1 cooler is running, one of the three fans fails and the standby cooler is started. When the number of coolers running is ≥ 4 groups, the A1 cooler will be stopped. When the number of coolers running is still 3 groups, A1 continues to run (indicating that the standby cooler has not started successfully).

[0044] (4) If the oil pump of the running cooler trips, or the 380VAC power supply fails, or the 110VDC power supply fails, or two or more fans fail, the standby cooler will be started and the entire group of failed coolers will be stopped.

[0045] Step 2.2.2, the cooler operation mode is 2-in-1-assistant and 1-standby mode (taking the main transformer phase A as an example). The fault switching control method during cooler operation is:

[0046] (1) Phase A is over-temperature (>50°C), an alarm is triggered, and no action is taken;

[0047] (2) If the A phase is over-temperature (>60°C) or over-current (>0.75A), the auxiliary cooler will be started; if the auxiliary cooler fails to be started, the standby cooler will be started after a delay of 5 seconds; if there is no A phase over-temperature (>50°C) and no A phase over-current (>0.75A), and the number of coolers in operation is ≥3 groups, the auxiliary cooler will be stopped; if there is a delay of 5 seconds, and the number of coolers in operation is ≥3 groups, the standby cooler will be stopped (this step is when the standby cooler is started due to over-temperature);

[0048] (3) If the A phase is over-temperature (>75°C), the auxiliary and standby coolers are started; after the temperature drops (<50°C), if the number of coolers in operation is ≥3 groups, the auxiliary cooler is stopped; after a delay of 5 seconds, if the number of coolers in operation is ≥3 groups, the standby cooler is stopped (this step is when the standby cooler is started due to over-temperature);

[0049] (4) If a single fan of A1 / A2 / A3 / A4 fails, the standby cooler will be started. For example, if A1 cooler is running and one of the three fans fails, the standby cooler will be started. If the standby cooler fails to start, the auxiliary cooler will be started after a delay of 5 seconds. If the number of coolers running is ≥ 3 groups, the A1 cooler will be stopped. If the number of coolers running is still 2 groups, A1 will continue to run (which means that the other 2 groups failed to start).

[0050] (5) If two or more of the three fans fail or the 380VAC power supply fails, the failed cooler will be stopped and the non-operating cooler will be started (both the auxiliary position and the standby position will be started). Considering that the running cooler is stopped first in this step, in order to improve reliability, both the auxiliary position and the standby position will be started. After the start-up is successful, the auxiliary position cooler will be stopped;

[0051] (6) If the running cooler trips or the oil pump fails, or the 110VDC power supply is lost, the non-running cooler will be started (both the auxiliary position and the standby position will be started); after the start-up is successful, the auxiliary position cooler will be stopped;

[0052] All the above-mentioned joint start, joint stop, trip, and failure of starting equipment will generate alarms. Figure 3 , 4 shown.

[0053] Step 2.3: When the cooler is completely stopped, determine the longest delay operation time of the transformer according to the oil level temperature of the transformer. After the delay, the main transformer cooler will be completely stopped and tripped.

[0054] When the main transformer is running at full load, after all coolers are shut down, it is allowed to continue running for 20 minutes. When the transformer oil surface temperature does not reach 75°C, it is allowed to rise to 75°C, but the maximum running time allowed after the transformer cooler is cut off cannot exceed 1 hour. In order to avoid the main transformer running for a long time without cooler heat dissipation, which may cause transformer insulation aging or even damage due to high temperature, the main transformer cooler full stop trip circuit is generally designed to increase the service life of the transformer.

[0055] The complete shutdown of the main transformer cooler is a very serious accident. When a cooler failure or power failure occurs, the cooler may be completely shut down, causing the main transformer to trip, leading to more serious consequences such as forced load reduction or even shutdown. Therefore, it is necessary to formulate an intelligent control strategy for the complete shutdown of the cooler. The logic of the complete shutdown of the cooler is shown in Table 5.

[0056] The cooler full stop circuit adopts phased alarm and improves the cooler full stop tripping logic, so that maintenance and operation personnel have a certain amount of reaction and processing time when the cooler fails, avoiding unnecessary tripping of the main transformer.

[0057] Step 3: Determine the automatic cycle switching control method of the cooler based on PLC

[0058] By utilizing the timing and counting functions of the PLC, a control strategy was designed for automatic periodic rotation of the coolers, thereby achieving automatic, timed and balanced rotation of the coolers, effectively extending the service life of the coolers and reducing the workload of operators in regularly switching coolers.

[0059] In the 3-in-use 1-standby mode, when the cycle switching interlock is put into operation, the standby cooler that is not in operation is started. After the interlock is successfully started, there is a delay of 15s, and the original group of coolers in operation is stopped, and the status position is changed (the new standby cooler is changed to the operation position, and the original group of coolers in operation is changed to the standby position). The order of the joint stop is fixed (A1, A2, A3 are in operation, and A4 is in standby, that is, 123 operation_4 stop; cycle switching stops A3, and the status position after switching is 412 operation_3 stop; the next cycle switching status position is 341 operation_2 stop; the next cycle switching status position is 234 operation_1 stop; the next cycle switching status position is 123 operation_4 stop).

[0060] In the 2-in-1 auxiliary and 1-in-standby mode, the periodic switching interlock is put into operation, and the two groups of coolers that are not in operation are started (1 auxiliary group and 1 standby group). After the joint start is successful, there is a delay of 15s, and the two groups of coolers that were originally in operation are stopped and the status bits are changed (the two groups of coolers that are newly in operation are changed to the operation bit, and the two groups of coolers that were originally in operation are changed to 1 auxiliary group and 1 standby group).

[0061] The present invention provides an intelligent control system suitable for a large main transformer cooler, comprising:

[0062] 1 PLC master control cabinet and 4 cooler control boxes. 1 PLC master control cabinet is connected to 4 cooler control boxes respectively. The transformers of 4 groups of coolers are distributed to 4 cooler control boxes for decentralized control, that is, each cooler control box controls one group of coolers of A / B / C three-phase transformers. The cooler is connected to the transformer oil tank through a connecting pipe. Each group of coolers includes 3 fans, 1 transformer oil pump and 1 oil flow relay.

[0063] One transformer oil pump and three fans in each cooler group are independently controlled by a drawer-type unit, and each motor is protected against short circuit, overload and phase loss.

[0064] Under the action of the transformer oil pump, the hot oil on the upper part of the transformer oil tank is sucked into the cooler, flows through the cooler tube cluster, transfers the heat to the cooling tube, and then the cooling tube cluster releases the heat to the air. On the air side, the transformer fan sucks the air, makes it flow through the tube cluster, absorbs the heat, and blows it out of the cooler, thereby achieving the purpose of cooling the transformer oil and keeping the transformer running at the allowable temperature.

[0065] Through PLC logic design, the corresponding number of coolers are automatically put into or out of operation according to the load and temperature of the main transformer. When the running cooler is cut off due to a fault, the standby and auxiliary cooler can be automatically put into operation.

[0066] PCS-9150Pro PLC is selected as the main controller with redundant configuration. Dual-core processor, main frequency 766MHz, RAM 512MB, electronic disk FLASH 4GB, to ensure the real-time and rapidity of postpartum care information. It supports developers to customize programming, greatly reduces the number of relays used, simplifies the wiring of the electrical secondary circuit, and flexibly realizes various operation control modes of the cooler.

[0067] The control system provided by the present invention also includes a display screen, which is connected to a PLC main control cabinet and four cooler control boxes respectively, and is used to display the status of the PLC and the cooling system in real time. In a specific embodiment, the display screen includes a human-computer interaction interface, and the status of the PLC and the cooling system is displayed in real time through the human-computer interaction interface.

[0068] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. An intelligent control method for a large main transformer cooler, characterized in that: The method comprises: Step 1, determine the cooler operation mode; Step 2: Determine the cooler control method according to the cooler operation status; Step 3: Determine the automatic cycle switching control method of the cooler according to the PLC.

2. The intelligent control method for a large main transformer cooler according to claim 1, characterized in that: The cooler operation mode in step 1 includes: 3 groups of working and 1 group of standby, or 2 groups of working, 1 group of auxiliary and 1 group of standby.

3. The intelligent control method for a large main transformer cooler according to claim 1, characterized in that: The step 2 comprises: Step 2.1: If the cooler has no faults, determine whether to put the working cooler into operation or cut off the working cooler according to the status of the main transformer or cooler test handle; Step 2.2, in case of a fault during the operation of the cooler, the operation of the cooler is determined based on the oil pump operation signal, and the cooler fault is determined based on the fan operation signal negated from the fan fault signal; Step 2.3: When all coolers are stopped, determine the longest delayed operation time of the transformer according to the oil level temperature of the transformer. After the delay, the main transformer cooler will be fully stopped and delayed tripped.

4. The intelligent control method for a large main transformer cooler according to claim 3, characterized in that: The step 2.1 is specifically as follows: when there is no fault in the cooler, when the main transformer is put into operation or the cooler test handle is put into operation, the working cooler is automatically put into operation; when the main transformer is stopped and the cooler test handle is withdrawn, the working cooler is automatically cut off.

5. The intelligent control method for a large main transformer cooler according to claim 3, characterized in that: The step 2.2 is specifically as follows: when the fan operation signal is not equal to the number of fan fault signals = 1, and the oil pump operation signal is present, it is determined that a single fan fault occurs during the operation of the cooler; when the fan operation signal is not equal to the number of fan fault signals ≥ 2, and the oil pump operation signal is present, it is determined that the cooler is faulty during operation; when the 380VAC incoming power supply is lost, and the oil pump operation signal is present, it is determined that the cooler is faulty during operation.

6. The intelligent control method for a large main transformer cooler according to claim 3, characterized in that: In the step 2.2, when a single fan drawer is manually pulled out, the fan will not be judged as faulty, ensuring that when one fan is under maintenance, the group of coolers is still available.

7. The intelligent control method for a large main transformer cooler according to claim 3, characterized in that: The step 2.3 is specifically as follows: when the main transformer is running at full load, after all coolers have been shut down, when the transformer oil level temperature exceeds 75°C, it is allowed to continue running for 20 minutes; when the transformer oil level temperature does not reach 75°C, it is allowed to rise to 75°C, and the maximum running time allowed after the transformer coolers are removed shall not exceed 1 hour.

8. The intelligent control method for a large main transformer cooler according to claim 1, characterized in that: The step 3 is specifically as follows: in the 3-in-1-standby mode, when the cycle switching interlock is put into operation, the standby cooler that is not in operation is started, and after the joint start is successful, a delay of 15 seconds is made, and the original running cooler is stopped, and the status bit is changed; In the 2-in-1 auxiliary and 1-in-1 standby mode, the periodic switching interlock is activated, and the 1 auxiliary group and 1 standby group that are not in operation are started. After the joint start is successful, there is a delay of 15s, and the 2 groups of coolers that were originally in operation are stopped and the status bit is changed.

9. An intelligent control system suitable for a large main transformer cooler, characterized in that: The system includes: 1 PLC main control cabinet and 4 cooler control boxes. 1 PLC main control cabinet is connected to 4 cooler control boxes respectively. Each cooler control box controls a group of coolers of each A / B / C three-phase transformer. The coolers are connected to the transformer oil tank through a connecting pipe; each group of coolers includes 3 fans, 1 transformer oil pump and 1 oil flow relay.

10. An intelligent control system suitable for a large main transformer cooler according to claim 9, characterized in that: In each group of coolers, one transformer oil pump and three fans are independently controlled by a drawer-type unit, and each motor is protected against short circuit, overload and phase loss.

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