Main transformer cooler control system based on PLC

Abstract

The invention belongs to the technical field of transformer control, and particularly relates to a main transformer cooler control system based on a PLC. Comprising a main transformer cooler control cabinet and a PLC master control cabinet, and the main transformer cooler control cabinet changes a traditional centralized control mode into a decentralized control mode. The system has the beneficial effects that the manual mode or the automatic mode of the transformer cooler can be flexibly switched according to requirements, and the system has the advantages of high reliability, high flexibility, strong anti-interference capability, powerful functions, high intelligent, digital and automatic levels and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer control, and in particular relates to a main transformer cooler control system based on PLC. Background Art

[0002] The main transformer is a very important and expensive main equipment in the power system. Once a failure occurs, it will not only threaten 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 and stable operation of the main transformer, it is necessary to work hard to improve the safety and controllability of the main transformer cooler control system.

[0003] Traditional transformer cooler control systems mostly use a large number of electromagnetic relays, which are not very reliable and have relatively simple control functions. In addition, there are some design defects and deficiencies in the AC power supply circuit, cooler control circuit, cooler full stop trip circuit and box auxiliary circuit. The entire operating environment is complex, the operation is frequent, and the components are easily affected by moisture, heat and damage, which has become the weak link of the transformer. Therefore, there are many problems and a large amount of maintenance. Summary of the invention

[0004] The purpose of the present invention is to provide a PLC-based main transformer cooler control system, which can completely solve the hidden dangers brought to the unit by various defects and shortcomings of traditional control methods by setting up a cooler main circuit and a control circuit, and realize safe and stable operation of the unit.

[0005] The technical solution of the present invention is as follows: a PLC-based main transformer cooler control system, including a main transformer cooler control cabinet and a PLC master control cabinet, the main transformer cooler control cabinet changes the traditional centralized control mode into decentralized control.

[0006] The main transformer cooler control cabinet includes an A-phase transformer, a B-phase transformer and a C-phase transformer, each phase transformer includes 4 groups of coolers, wherein each group of coolers includes 3 fans and 1 oil pump, and the cooling method of the main transformer cooler is forced oil circulation air cooling. The cooler is connected to the transformer oil tank through a connecting pipe. 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.

[0007] The main transformer cooler control cabinet controls a group of coolers for phases A, B, and C, where each group of coolers includes 3 fans and 1 oil pump, and 3 groups have a total of 12 control loops, as shown in the following table:

[0008] Control cabinet name Control Object Number of control loops Main transformer group 1 cooler control cabinet Group A1, Group B1, Group C1 4 per group, 12 in total Main transformer group 2 cooler control cabinet Group A2, Group B2, Group C2 4 per group, 12 in total Main transformer group 3 cooler control cabinet Group A3, Group B3, Group C3 4 per group, 12 in total Main transformer group 4 cooler control cabinet Group A4, Group B4, Group C4 4 per group, 12 in total

[0009] The main transformer cooler control cabinet adopts ABB MNS3.0 low-voltage withdrawable switch cabinet, in which the control unit is a fixed unit and the rest are all withdrawable drawer designs.

[0010] The electrical components and functions of the main transformer cooler control cabinet are shown in the following table:

[0011]

[0012] The 380VAC power supply in the control cabinet is connected to the incoming drawer through the busbar. The incoming drawer is equipped with an incoming circuit breaker, power monitoring and alarm circuit. The outlet of the incoming drawer is connected to the vertical busbar of the control cabinet and distributed to each fan and oil pump load unit through the vertical busbar.

[0013] The front of the main transformer cooler control cabinet is installed from top to bottom in sequence:

[0014] 1) PLC redundant controller, local switch, 24V switching power supply;

[0015] 2)PLC first I / O branch;

[0016] 3)PLC second I / O branch;

[0017] 4) Air switch, intermediate relay;

[0018] 5) Power surge protector and maintenance power socket.

[0019] The internal and external terminals and terminal boards are arranged in three rows on both sides of the main transformer cooler control cabinet. The main transformer cooler control cabinet is designed with three power input lines, namely the first power supply of PLC, the second power supply of PLC, and the fan, lighting and maintenance power supply. Surge protectors are installed in all three power supplies to prevent peak current or voltage caused by external interference. Power monitoring relays are installed in front of the circuit breaker for the first and second incoming power supplies.

[0020] The PLC master control cabinet adopts PLC as the control core and touch screen as the human-machine interface, and is connected to 4 cooler control cabinets through cables. The cooler control cabinet is a unit structure, each unit controls a group of coolers, the AC contactor in the unit is used as an actuator, and the circuit breaker is used as a protection element. The PLC master control cabinet sends start and stop instructions to the corresponding control circuits of each control unit of the cooler control cabinet according to the logic control requirements, and starts a group of fans and oil pumps in each phase at the same time.

[0021] The beneficial effects of the present invention are as follows: the manual or automatic mode of the transformer cooler can be flexibly switched as needed, and it has the advantages of high reliability, flexibility, strong anti-interference ability, powerful functions, intelligence, digitization, and high automation level; the system collects all cooler signals of the transformer for real-time monitoring, and the operating status of each phase cooler of the transformer, including the input status, fault shutdown and other information, can be displayed on the local human-machine interface, which is clear at a glance, thereby enhancing the monitoring function of the operation; the transformer fault signal is connected to the main control alarm light window and the computer monitoring system through the PLC output point quantity, the signal is eye-catching, and is accompanied by an alarm, so that the operating personnel can promptly discover and grasp the operation and fault conditions of the transformer cooler; the control system integrates signal acquisition, data processing, intelligent control, human-computer interaction and other functions, and realizes the intelligence of the transformer controller. Control, monitoring and execution improve the safety and economy of transformer operation; use the internal clock of PLC to realize the automatic timed rotation function of transformer cooler, effectively extend the service life of cooler and reduce the workload of operators to switch coolers regularly; optimize the control loop design of main transformer cooler control system, adopt the design idea of ​​"single cabinet controls a group of fans in three phases", transform the control mode of main transformer cooler, eliminate single-point sensitive components, avoid single failure of main transformer cooler leading to load reduction or shutdown of unit, completely solve the hidden danger of "full shutdown", achieve the effect of separation from sensitive equipment, and improve the risk resistance of equipment; optimize the installation and wiring mode of components in control box, facilitate online processing of faulty components, and realize power-off maintenance of single cabinet without affecting the normal operation of cooler; it has wide applicability and covers the control of transformer coolers in all power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the cooler control;

[0023] Figure 2 It is the delay tripping circuit for the complete stop of the cooler. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] By optimizing the control loop design of the main transformer cooler control system and adopting the design concept of "single cabinet controlling a group of fans in three phases", the main transformer cooler control system is transformed, the SPV single-point sensitive components are eliminated, and the load reduction or shutdown of the unit caused by a single failure of the main transformer cooler is avoided, thereby achieving the effect of disconnecting from sensitive equipment.

[0026] The control mode of the cooler is drawer-type, and each fan has a drawer to control it. If a single fan in a group fails, it can be maintained under power, and it can be repaired independently without affecting other normal working units. At the same time, programmable controller (PLC) technology is used to control the main transformer cooler, simplify the wiring of the electrical secondary circuit, and improve the flexibility of equipment control and the reliability of operation.

[0027] The control loop of the cooler consists of two parts: manual mode and automatic mode, and these two parts are interlocked. The PLC control system is the main control core. The automatic mode adopts a redundant CPU configuration with one main and one standby. PLC software programming is used to control the cooler, which greatly reduces the number of relays used. Through the coordination of PLC software programming and hardware circuits, a variety of operation control modes of the cooler can be realized, which is more flexible and controllable. It can eliminate the hidden dangers and risks of the cooler stopping due to unscientific circuit design and single component failure. The domestic PLC is used to achieve complete independent control of key equipment.

[0028] At the same time, by utilizing the powerful timing and counting functions of PLC, an automatic cycle switching function is innovatively added to achieve automatic timed and balanced rotation of the cooler, effectively extending the service life of the cooler and reducing the workload of operators in regularly switching coolers.

[0029] The cooler full stop circuit adopts phased alarm and transforms the cooler full stop tripping logic, so that maintenance and operation personnel have a certain amount of processing time when the cooler fails, avoiding unnecessary tripping of the main transformer and completely solving the "full stop" hidden danger.

[0030] The auxiliary circuit of the cooler control cabinet box adds a ventilation and cooling circuit to keep the cooler control cabinet in a suitable temperature range, thereby increasing the service life of the components in the cabinet.

[0031] like Figure 1 and 2 As shown, a PLC-based main transformer cooler control system includes a main transformer cooler control cabinet and a PLC main control cabinet. (Description: Figure 1 and Figure 2 It is not a schematic diagram of the cooler control cabinet and PLC control cabinet)

[0032] The connection relationship between the main transformer cooler control cabinet and the PLC main control cabinet.

[0033] The control circuit of the cooler consists of two parts: manual mode and automatic mode, and the two parts are interlocked. The manual mode uses the operating handle on the cooler control cabinet to start and stop the cooler; the automatic mode uses the PLC in the PLC main control cabinet as the core controller, and uses the PLC software logic to control the cooler. The coordination of the PLC software program and the hardware circuit of the cooler control cabinet realizes various operation control modes of the cooler.

[0034] The main transformer cooler control cabinet changes the traditional centralized control mode to decentralized control. When a major failure occurs in a control cabinet, it will not affect all coolers in the corresponding phase, thus avoiding shutdown accidents.

[0035] like Figure 1 As shown, the main transformer cooler control cabinet includes an A-phase transformer, a B-phase transformer and a C-phase transformer. Each phase transformer includes 4 groups of coolers, wherein each group of coolers includes 3 fans and 1 oil pump. (Additional information on the relationship between the fan and the oil pump: the cooling method of the main transformer cooler is forced oil circulation air cooling. The cooler is connected to the transformer oil tank through a connecting pipe. 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 heat to the air. On the air side, the transformer fan sucks in 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 an allowable temperature.) Connect each group of coolers of the A / B / C three-phase transformers to a cooler control box, for a total of 4.

[0036] Each unit is equipped with 4 cooler control cabinets. Each control cabinet controls a group of coolers for phases A, B, and C. Each group of coolers contains 3 fans and 1 oil pump. There are 12 control loops in 3 groups, as shown in the following table:

[0037] Control cabinet name Control Object Number of control loops Main transformer group 1 cooler control cabinet Group A1, Group B1, Group C1 4 per group, 12 in total Main transformer group 2 cooler control cabinet Group A2, Group B2, Group C2 4 per group, 12 in total Main transformer group 3 cooler control cabinet Group A3, Group B3, Group C3 4 per group, 12 in total Main transformer group 4 cooler control cabinet Group A4, Group B4, Group C4 4 per group, 12 in total

[0038] The control cabinet adopts ABB MNS3.0 low-voltage withdrawable switch cabinet, of which the control unit is a fixed unit and the rest are withdrawable drawer designs.

[0039] What are the main components of the control cabinet and what are its main functions?

[0040] The main electrical components and functions of the control cabinet are shown in the following table:

[0041]

[0042] The 380VAC power supply in the control cabinet is connected to the incoming drawer through the busbar. The incoming drawer is equipped with an incoming circuit breaker, power monitoring (three-phase indicator light) and an alarm circuit. The outlet of the incoming drawer is connected to the vertical busbar of the control cabinet and distributed to each fan and oil pump load unit through the vertical busbar.

[0043] The BA unit is a 380VAC power supply incoming line drawer. The main circuit is equipped with a molded case circuit breaker, which is manually operated. The control circuit is equipped with three power-on indicator lights, a voltage monitoring relay and a three-color indicator light for closing / opening / fault. The closing, opening, fault and 380VAC power failure contact signals of the incoming line circuit are externally led to the PLC cabinet for status indication and fault alarm.

[0044] The CA unit is a control unit. Each cabinet is independently supplied with a 110VDC control power supply from the outside. There are 6 conversion switches on the control unit door panel, 3 of which are manual / automatic selection switches, and the other 3 are start / stop control switches. Each control switch controls the simultaneous start and stop of 1 oil pump and 3 fans of each phase cooler. When the manual control mode is selected, the cooler oil pump and fan are controlled by the start / stop switch; when the automatic control mode is selected, the cooler oil pump and fan are automatically controlled by the PLC. The control signal is extended through the intermediate relay and connected to the start and stop circuits of each oil pump and fan. The control unit receives the start and stop commands input from the PLC cabinet; the automatic and manual signals of the control unit and the 110VDC power failure signal contacts are output to the PLC cabinet for status indication and fault alarm.

[0045] EA~FC, GA~HC, JA~KC units are motor starter units, which control the A / B / C three-phase oil pump and fan of each group of coolers respectively. The main circuit in the unit is equipped with a circuit breaker, contactor and thermal relay. The start and stop commands of the control circuit come from the CA control unit, and the three-color indicator lights of closing / opening / fault are set for local indication. The operation, stop and fault contact signals of the starter circuit are output to the PLC cabinet for status indication and fault alarm.

[0046] The PLC main control cabinet adopts the PCS-9150Pro PLC system of NARI Relay Protection, which can set the working mode (working, auxiliary, standby, stop) of each group of coolers of the three phases A, B, and C of the transformer, and display the equipment operation status and alarm information. Two sets of fan filter groups are installed on the upper part of the front door, and ventilation filters are installed on the lower part to form a bottom-in and top-out ventilation mode. A touch screen is installed about 1.6m above the ground on the front door to facilitate operation and maintenance personnel. The "cooler test handle", "cooler full stop handle", and "touch screen power switch handle" are installed from left to right below the touch screen.

[0047] The relationship between the PLC main control cabinet and the control cabinet, and which part is specifically connected.

[0048] The PLC master control cabinet uses PLC as the main control core and the touch screen as the human-machine interface, and is connected to the four cooler control cabinets through cables. The cooler control cabinet is a unit structure, each unit controls a group of coolers, the AC contactor in the unit is used as the actuator, and the circuit breaker is used as the protection element. According to the logic control requirements, the PLC master control cabinet sends start and stop instructions to the corresponding control circuits of each control unit of the cooler control cabinet, and starts a group of fans and oil pumps in each phase at the same time. In addition, based on PLC and configuration software, the working status and fault conditions of the cooler can be monitored online in real time in the touch screen visualization interface, and the cooler operation mode can be automatically rotated at a fixed time, realizing control automation, status informationization, and humanized display and operation.

[0049] Install the following from top to bottom on the front of the control cabinet:

[0050] 1) PLC redundant controller, local switch, 24V switching power supply;

[0051] 2)PLC first I / O branch;

[0052] 3)PLC second I / O branch;

[0053] 4) Air switch, intermediate relay;

[0054] 5) Power surge protector and maintenance power socket.

[0055] Internal and external terminals and terminal boards are arranged in three rows on both sides of the control cabinet. The control cabinet is designed with 3 power input lines, namely the first power supply of PLC (DC110V), the second power supply of PLC (UPS AC220V), and the fan, lighting and maintenance power supply (AC220V). Surge protectors are set for all 3 power supplies to prevent peak current or voltage caused by external interference. Power monitoring relays are set at the front end of the circuit breaker for the first and second power supply lines.

[0056] The power supply of PLC and local switch device is designed with dual redundant DC24V input, and two DC24V power supply monitoring relays are set. Since the touch screen only supports single power supply, a power switch handle is set so that when one power supply fails, it can be manually switched to the second power supply, thereby improving the power supply reliability of single power supply equipment.

[0057] The cooler full stop delay trip hard circuit is set in phases, which is connected in series by the "cooler full stop input handle", PLC full stop delay logic trip output, four groups of oil flow indication signals, and circuit breaker position signal. For specific design circuits, see Figure 2 .

[0058] The touch screen installed on the main transformer cooler PLC control cabinet and the signal lights on the main transformer cooler power cabinet can intuitively and comprehensively reflect the operating status of the main transformer cooler and the signals of each conversion switch and indicator light.

[0059] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solution of the present invention rather than to limit it. The protection scope of the present invention is not limited thereto.

Claims

1. A PLC-based main transformer cooler control system, characterized in that: It includes the main transformer cooler control cabinet and the PLC main control cabinet. The main transformer cooler control cabinet changes the traditional centralized control method into decentralized control.

2. A PLC-based main transformer cooler control system as claimed in claim 1, characterized in that: The main transformer cooler control cabinet includes an A-phase transformer, a B-phase transformer and a C-phase transformer, each phase transformer includes 4 groups of coolers, wherein each group of coolers includes 3 fans and 1 oil pump, and the cooling method of the main transformer cooler is forced oil circulation air cooling. The cooler is connected to the transformer oil tank through a connecting pipe. 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.

3. A PLC-based main transformer cooler control system as claimed in claim 2, characterized in that: The main transformer cooler control cabinet controls a group of coolers for phases A, B, and C, where each group of coolers includes 3 fans and 1 oil pump, and 3 groups have a total of 12 control loops, as shown in the following table:

4. A PLC-based main transformer cooler control system as claimed in claim 2, characterized in that: The main transformer cooler control cabinet adopts ABB MNS3.0 low-voltage withdrawable switch cabinet, in which the control unit is a fixed unit and the rest are all withdrawable drawer designs.

5. A PLC-based main transformer cooler control system as claimed in claim 2, characterized in that: The electrical components and functions of the main transformer cooler control cabinet are shown in the following table: The 380VAC power supply in the control cabinet is connected to the incoming drawer through the busbar. The incoming drawer is equipped with an incoming circuit breaker, power monitoring and alarm circuit. The outlet of the incoming drawer is connected to the vertical busbar of the control cabinet and distributed to each fan and oil pump load unit through the vertical busbar.

6. A PLC-based main transformer cooler control system as claimed in claim 2, characterized in that: The front of the main transformer cooler control cabinet is installed from top to bottom in sequence: 1) PLC redundant controller, local switch, 24V switching power supply; 2)PLC first I / O branch; 3)PLC second I / O branch; 4) Air switch, intermediate relay; 5) Power surge protector and maintenance power socket. The internal and external terminals and terminal boards are arranged in three rows on both sides of the main transformer cooler control cabinet. The main transformer cooler control cabinet is designed with three power input lines, namely the first power supply of PLC, the second power supply of PLC, and the fan, lighting and maintenance power supply. Surge protectors are installed in all three power supplies to prevent peak current or voltage caused by external interference. Power monitoring relays are installed in front of the circuit breaker for the first and second incoming power supplies.

7. A PLC-based main transformer cooler control system as claimed in claim 1, characterized in that: The PLC master control cabinet adopts PLC as the control core and touch screen as the human-machine interface, and is connected to 4 cooler control cabinets through cables. The cooler control cabinet is a unit structure, each unit controls a group of coolers, the AC contactor in the unit is used as an actuator, and the circuit breaker is used as a protection element. The PLC master control cabinet sends start and stop instructions to the corresponding control circuits of each control unit of the cooler control cabinet according to the logic control requirements, and starts a group of fans and oil pumps in each phase at the same time.

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