A smart control method and system applicable to large main transformer coolers

Abstract

This invention belongs to the field of transformer control technology, specifically relating to an intelligent control method and system suitable for large main transformer coolers. The method includes: Step 1, determining the cooler operating mode; Step 2, determining the cooler control method based on the cooler's operating status; Step 3, determining the cooler's automatic periodic switching control method based on a PLC. This invention uses PLC technology to control the transformer cooling device, enabling optimal judgment based on transformer load and oil temperature, automatically activating or deactivating the cooler, saving energy, reducing consumption, and extending its lifespan. Simultaneously, it simplifies electrical secondary circuit wiring, improves equipment reliability, and achieves online real-time monitoring of the main transformer cooler system's operating status and fault conditions.

Description

Technical Field

[0001] This invention belongs to the field of transformer control technology, specifically relating to an intelligent control method and system suitable for large main transformer coolers. Background Technology

[0002] The main transformer is a critical electrical device in a power plant, directly affecting the reliability of the power supply system. A failure in this transformer not only threatens the safe and stable operation of the power plant and grid but can also lead to significant economic losses. To ensure the safe, stable, and economical operation of the transformer, it is essential to monitor the transformer oil temperature in real time and control the cooler system to manage its cooling. A complete shutdown of the main transformer cooler is a very serious accident in the power system. When a power outage or malfunction causes a complete shutdown of the cooler, it triggers the main transformer's non-electrical protection circuit breaker, leading to the transformer tripping and potentially resulting in forced load reduction or even shutdown.

[0003] Traditional main transformer cooler control systems use control loops built from intermediate relays, time relays, contactors, etc., which have drawbacks such as high component failure rate, complex control wiring, single cooler control function, and low redundancy. They can no longer meet the requirements of safety, reliability, intelligence, and automation of field equipment. Summary of the Invention

[0004] The purpose of this invention is to provide an intelligent control method and system suitable for large main transformer coolers, which can fully guarantee the reliability and flexibility of the main transformer cooler control system.

[0005] Technical solution to achieve the purpose of this invention:

[0006] A smart control method for large main transformer coolers, the method comprising:

[0007] Step 1: Determine the cooler's operating mode;

[0008] Step 2: Determine the cooler control method based on the cooler's operating status;

[0009] Step 3: Determine the automatic cycle switching control method for the cooler based on the PLC.

[0010] The cooler operating modes in step 1 include: 3 working groups and 1 standby group, or 2 working groups, 1 auxiliary group, and 1 standby group.

[0011] Step 2 includes:

[0012] Step 2.1: If the cooler is fault-free, determine whether to put the working cooler into or out of operation based on the status of the main transformer or cooler test handle.

[0013] Step 2.2: In case of a malfunction during cooler operation, determine the cooler's operation based on the oil pump operation signal, and determine the cooler malfunction by taking the non-fan operation signal and the fan malfunction signal.

[0014] Step 2.3: With all coolers shut down, determine the maximum delay time for the transformer based on the transformer oil temperature. After the delay, the main transformer coolers will shut down and trip after a delay.

[0015] Specifically, step 2.1 is as follows: when the main transformer is put into operation or the cooler test handle is engaged, the working cooler is automatically engaged when the main transformer is shut down or the cooler test handle is disengaged.

[0016] Step 2.2 specifically involves: when the number of non-fan fault signals is 1 and the oil pump is running, it is determined that a single fan is faulty in the cooler; when the number of non-fan fault signals is ≥2 and the oil pump is running, it is determined that the cooler is faulty in operation; when the 380VAC incoming power supply is lost and the oil pump is running, it is determined that the cooler is faulty in operation.

[0017] In step 2.2, when a single fan drawer is manually pulled out, the fan will not be identified as faulty, ensuring that the cooler group is still usable when a fan is under maintenance.

[0018] Step 2.3 specifically refers to the following: When the main transformer is running at full load, after all coolers are taken out of operation, if the transformer oil temperature exceeds 75°C, it is allowed to continue running for 20 minutes; if the transformer oil temperature does not reach 75°C, it is allowed to rise to 75°C. The maximum allowed operating time after the transformer is disconnected from the coolers shall not exceed 1 hour.

[0019] Step 3 specifically involves the following steps: In the 3-use, 1-standby mode, when the periodic switching interlock is engaged, the non-operating standby cooler is started. After a 15-second delay, the original operating cooler group is stopped and its status is changed. In the 2-use, 1-auxiliary, 1-standby mode, when the periodic switching interlock is engaged, the non-operating auxiliary and standby coolers are started. After a 15-second delay, the original operating coolers are stopped and their status is changed.

[0020] An intelligent control system for large main transformer coolers is provided. The system includes: one PLC main control cabinet and four cooler control boxes. The PLC main control cabinet is connected to the four cooler control boxes respectively. Each cooler control box controls one set of coolers for each of the three-phase A / B / C transformers. The coolers are connected to the transformer oil tank through connecting pipes. Each set of coolers includes three fans, one transformer oil pump and one 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 this invention are as follows:

[0023] This invention provides an intelligent control method and system suitable for large main transformer coolers. It uses PLC technology to control the transformer cooling device, and can make optimal judgments based on the transformer load and oil temperature to automatically start or stop the cooler's operation, saving energy, reducing consumption, and extending its service life. At the same time, it simplifies the wiring of the electrical secondary circuit, improves the reliability of equipment operation, and realizes online real-time monitoring of the main transformer cooler system's working status and fault conditions. The PLC, the cooling system, and the real-time operating conditions are clearly displayed on the human-machine interface. Attached Figure Description

[0024] Figure 1 The present invention provides a start-stop logic diagram for a cooler in the absence of a fault in an intelligent control method for a large main transformer cooler (taking the first group of coolers in phase A as an example);

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

[0026] Figure 3 The present invention provides a smart control method for large main transformer coolers, which includes a cooler interconnection logic diagram (taking the first group of coolers in phase A as an example).

[0027] Figure 4 The present invention provides a logic diagram for the inter-shutdown of a cooler in an intelligent control method applicable to a large main transformer cooler (taking the first group of coolers in phase A as an example);

[0028] Figure 5 The present invention provides a logic diagram for the complete shutdown of the cooler in an intelligent control method applicable to large main transformer coolers (taking the A-phase cooler as an example). Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0030] This invention provides an intelligent control method suitable for large main transformer coolers, specifically including the following steps:

[0031] Step 1: Determine the cooler operating mode

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

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

[0034] Step 2.1: If the cooler is fault-free, determine whether to engage or disengage the working cooler based on the status of the main transformer or cooler test handle.

[0035] When the cooler is functioning correctly, the working cooler automatically engages when the main transformer is put into operation or the cooler test handle is engaged; when the main transformer is shut down or the cooler test handle is disengaged, the working cooler automatically disengages. Figure 1 As shown.

[0036] Step 2.2: In case of a cooler malfunction during operation, determine the cooler's operation based on the oil pump operation signal, and determine the cooler malfunction by taking the non-fault signal from the fan operation signal.

[0037] When the number of non-fan fault signals in the fan operation signal is 1, and the oil pump operation signal is also present, a single fan fault is determined to be occurring in the cooler. When the number of non-fan fault signals in the fan operation signal is ≥2, and the oil pump operation signal is also present, a cooler fault is determined to be occurring in operation. Similarly, when the 380VAC power supply fails, and the oil pump operation signal is also present, a cooler fault is determined to be occurring in operation. The cooler fault determination logic is as follows: Figure 2 As shown.

[0038] When a single fan drawer is manually pulled out, no fan malfunction is detected, ensuring that the cooler group remains usable even when one fan is under maintenance. This improves the flexibility of cooler control and reliability under extreme conditions.

[0039] Specifically, based on the cooler's operating mode, the fault switching control method during cooler operation is determined as follows:

[0040] Step 2.2.1: The cooler operates in a 3-in-1-out mode (taking the main transformer's A phase as an example). The fault switching control method during cooler operation is as follows:

[0041] (1) If phase A overheats (>50℃), an alarm will be triggered, but no action will be taken.

[0042] (2) If phase A overheats (>75℃), the standby cooler will be started; if the temperature drops (<50℃), the standby cooler will be shut down.

[0043] (3) If a single fan fails, the standby cooler will be activated. Taking A1 as an example, if one of the three fans fails after A1 cooler is running, the standby cooler will be activated. When the number of coolers running is ≥4, A1 cooler will be shut down. When the number of coolers running is still 3, A1 will continue to run (indicating that the standby cooler failed to start).

[0044] (4) If the operating cooler oil pump 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 faulty cooler unit will be shut down.

[0045] Step 2.2.2: The cooler operates in a 2-in-1-out-of-service mode (taking the main transformer's A phase as an example). The fault switching control method during cooler operation is as follows:

[0046] (1) If phase A overheats (>50℃), an alarm will be triggered, but no action will be taken.

[0047] (2) If phase A overheats (>60℃) or phase A overcurrents (>0.75A), the auxiliary cooler is started; if the auxiliary cooler fails to start, the standby cooler is started after a 5s delay; if there is no phase A overheat (>50℃) and no phase A overcurrent (>0.75A), and the number of coolers in operation is ≥3, the auxiliary cooler is stopped; after a 5s delay, if the number of coolers in operation is ≥3, the standby cooler is stopped (this step is for the standby cooler to start due to overheating).

[0048] (3) If phase A overheats (>75℃), start the auxiliary and standby coolers; after the temperature drops (<50℃), if the number of coolers in operation is ≥3, stop the auxiliary cooler; after a 5s delay, if the number of coolers in operation is ≥3, stop the standby cooler (this step is for the standby cooler to start when overheating).

[0049] (4) If a single fan in A1 / A2 / A3 / A4 fails, the standby cooler will be activated. Taking A1 as an example, if one of the three fans fails after A1 cooler is running, the standby cooler will be activated. If the standby cooler fails to start, the auxiliary cooler will be activated after a 5-second delay. When the number of coolers running is ≥3, A1 cooler will be shut down. When the number of coolers running is still 2, A1 will continue to run (indicating 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 faulty cooler will be shut down and the non-operating cooler will be started (both the auxiliary and standby coolers will be started). Considering that the operating cooler will be shut down first, in order to improve reliability, both the auxiliary and standby coolers will be started. After the start-up is successful, the auxiliary cooler will be stopped.

[0051] (6) If the running cooler trips, the oil pump fails, or the 110VDC power supply fails, the non-running cooler will be restarted (both the auxiliary and standby coolers will be restarted); after the restart is successful, the auxiliary cooler will be stopped.

[0052] An alarm will be triggered for all the above-mentioned failures in joint start-up, joint stop-up, tripping, and starting of equipment. The logic for joint start-up and joint stop of the cooler is as follows: Figure 3 , 4 As shown.

[0053] Step 2.3: With all coolers shut down, determine the maximum delayed operation time of the transformer based on the transformer oil temperature. After the delay, the main transformer coolers will shut down and trip after a delay.

[0054] When the main transformer is running at full load, it is allowed to continue operating for 20 minutes after all coolers have been shut down. If the transformer oil temperature has not reached 75℃, it is allowed to rise to 75℃. However, the maximum allowed operating time after the coolers are disconnected cannot exceed one hour. To prevent the main transformer from operating for extended periods without cooler cooling, which could lead to transformer insulation aging or even damage due to high temperatures, a complete shutdown trip circuit for the main transformer coolers is generally designed to improve the transformer's service life.

[0055] A complete shutdown of the main transformer cooler is a very serious accident. Cooler malfunctions, power outages, and other situations can all cause a complete cooler shutdown, leading to a tripping of the main transformer and potentially resulting in forced load reduction or even shutdown. Therefore, an intelligent control strategy for a complete cooler shutdown is necessary. The cooler shutdown logic is shown in Table 5.

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

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

[0058] By utilizing the timing and counting functions of the PLC, a control strategy for automatic switching of coolers according to a cycle was designed, thereby realizing automatic timed and balanced switching of coolers, effectively extending the service life of coolers and reducing the workload of operators in periodically switching coolers.

[0059] In 3-operation, 1-standby mode, when the periodic switching interlock is engaged, the non-operating standby cooler is started. After a 15-second delay, the originally operating cooler group is stopped, and its status is changed (the newly operating standby cooler is changed to the operating position, and the originally operating cooler group is changed to the standby position). The stopping sequence is fixed (A1, A2, A3 are operating, A4 is standby, i.e., 123 operating_4 stopping; during periodic switching, A3 is stopped, and the status after the switch is 412 operating_3 stopping; the next periodic switch status is 341 operating_2 stopping; the next subsequent periodic switch status is 234 operating_1 stopping; the next subsequent periodic switch status is 123 operating_4 stopping).

[0060] In the 2-use, 1-auxiliary, 1-standby mode, the interlock is periodically switched on and started, and the two non-running coolers (1 auxiliary and 1 standby) are started. After a 15-second delay, the two running coolers are stopped and their status is changed (the two newly running coolers are changed to the running position, and the two running coolers are changed to 1 auxiliary and 1 standby).

[0061] This invention provides an intelligent control system suitable for large main transformer coolers, comprising:

[0062] The system consists of one main PLC control cabinet and four cooler control boxes, with each control box connected to one of the four cooler control boxes. The transformers for the four cooler groups are distributed among the four control boxes for decentralized control; each control box controls one cooler group for each of the A, B, and C three-phase transformers. The coolers are connected to the transformer oil tank via connecting pipes. Each cooler group includes three fans, one transformer oil pump, and one oil flow relay.

[0063] Each cooler unit has one transformer oil pump and three fans, each controlled independently by a drawer-type unit, with short-circuit, overload, and phase loss protection for each motor.

[0064] Under the action of the transformer oil pump, hot oil from the upper part of the transformer tank is drawn into the cooler, flows through the cooler tube bundle, transfers heat to the cooling tubes, and then the cooling tube bundle releases heat to the air. On the air side, the transformer fan draws in air, makes it flow through the tube bundle, absorbs heat, and blows it out of the cooler, thereby achieving the purpose of cooling the transformer oil and keeping the transformer operating at the allowable temperature.

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

[0066] The PCS-9150Pro PLC was selected as the main controller, employing a redundant configuration. It features a dual-core processor with a 766MHz clock speed, 512MB of RAM, and 4GB of FLASH memory to ensure the real-time and rapid delivery of postpartum care information. It supports custom programming by developers, significantly reducing the number of relays used, simplifying electrical secondary circuit wiring, and flexibly implementing various operating control modes for the cooler.

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

[0068] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A smart control method applicable to large main transformer coolers, characterized in that, The method includes: Step 1: Determine the cooler's operating mode; Step 2: Determine the cooler control method based on the cooler's operating status; Step 3: Determine the automatic cycle switching control method for the cooler based on the PLC; The cooler operation modes in step 1 include: 3 groups working and 1 group on standby, or 2 groups working, 1 group auxiliary and 1 group on standby. Step 2 includes: Step 2.1: If the cooler is fault-free, determine whether to put the working cooler into or out of operation based on the status of the main transformer or cooler test handle. Step 2.2: In case of a malfunction during cooler operation, determine the cooler's operation based on the oil pump operation signal, and determine the cooler malfunction by taking the non-fan operation signal and the fan malfunction signal. Step 2.3: With all coolers shut down, determine the maximum delay time for the transformer based on the transformer oil temperature. After the delay, the main transformer coolers will shut down and trip after a delay. Step 3 specifically involves the following steps: In the 3-use, 1-standby mode, when the periodic switching interlock is engaged, the non-operating standby cooler is started. After a 15-second delay, the original operating cooler group is stopped and its status is changed. In the 2-use, 1-auxiliary, 1-standby mode, when the periodic switching interlock is engaged, the non-operating auxiliary and standby coolers are started. After a 15-second delay, the original operating coolers are stopped and their status is changed.

2. The intelligent control method for large main transformer coolers according to claim 1, characterized in that, Specifically, step 2.1 is as follows: when the main transformer is put into operation or the cooler test handle is engaged, the working cooler is automatically engaged when the main transformer is shut down or the cooler test handle is disengaged.

3. The intelligent control method for large main transformer coolers according to claim 1, characterized in that, Step 2.2 specifically involves: when the number of non-fan fault signals is 1 and the oil pump is running, it is determined that a single fan is faulty in the cooler; when the number of non-fan fault signals is ≥2 and the oil pump is running, it is determined that the cooler is faulty in operation; when the 380VAC power supply is lost and the oil pump is running, it is determined that the cooler is faulty in operation.

4. The intelligent control method for large main transformer coolers according to claim 1, characterized in that, In step 2.2, when a single fan drawer is manually pulled out, the fan will not be identified as faulty, ensuring that the cooler group is still usable when a fan is under maintenance.

5. The intelligent control method for large main transformer coolers according to claim 1, characterized in that, Step 2.3 specifically refers to the following: When the main transformer is running at full load, after all coolers are taken out of operation, if the transformer oil temperature exceeds 75°C, it is allowed to continue running for 20 minutes; if the transformer oil temperature does not reach 75°C, it is allowed to rise to 75°C. The maximum allowed operating time after the transformer is disconnected from the coolers shall not exceed 1 hour.

6. An intelligent control system suitable for large main transformer coolers, using the intelligent control method for large main transformer coolers as described in any one of claims 1-5, characterized in that, The system includes: one PLC main control cabinet and four cooler control boxes. The PLC main control cabinet is connected to the four cooler control boxes respectively. Each cooler control box controls one set of coolers for each of the three-phase transformers A, B, and C. The coolers are connected to the transformer oil tank through connecting pipes. Each set of coolers includes three fans, one transformer oil pump, and one oil flow relay.

7. The intelligent control system for large main transformer coolers according to claim 6, 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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