CN100524139C - Monitoring device for main transfer wind cooling system and its working method - Google Patents

Abstract

The invention relates to a monitoring device for a main transformer air-cooled system, which has a programmable controller and a drive control circuit connected with the programmable controller; the fault signal input end of the programmable controller is connected with a CPLD fault detection circuit to detect cooling The oil pumps and fans in the device may have phase loss, overload or short circuit faults, and cut off the oil pumps and fans with the faults through the drive control circuit, which greatly improves the reliability of phase loss fault monitoring; the digital controller of the programmable controller The signal terminal can receive the oil temperature digital signal of the main transformer and the load current digital signal; after adopting the touch screen which is electrically connected with the programmable controller bidirectionally, the parameters in the programmable controller can be artificially set; the touch screen can also record and display The fault information of the cooler, the oil temperature of the main transformer and the load current make the monitoring device of the present invention more practical and easy to use.

Description

Monitoring device and working method of main transformer air-cooling system

technical field

The invention relates to a monitoring device and working method suitable for the main transformer air-cooling system of a substation and a power plant.

Background technique

In the traditional transformer cooler control device, traditional detection components such as contactors, intermediate relays, time relays, and selector switches are often used to control the cooler. The components are installed in the control device of the cooler. Since the distribution of the components is scattered and there are many circuit circuits in the cooling device, there are many control components, so the wiring between the components is very cumbersome. More control components also make the cooling control device bulkier. In addition, most of the relays used in the cooler control device of the transformer are composed of electromagnets and contacts. Therefore, when the cooler control device is running normally with electricity, the electromagnetic coil will make a loud sound when it is running normally with electricity and the contacts are closed. The noise is large during operation, the failure rate is high, and the maintenance is inconvenient.

Chinese patent application 01221810.3 discloses a transformer cooler control device. The application adopts a module controller to control the automatic timing on or off of the cooler, and has two control modes: manual and automatic. But the control device of this application has some deficiencies in actual use. First of all, the control device of this application only realizes the control of the automatic timing input or cut-off of the cooler through the module controller, and its fault detection circuit still uses traditional detection components, and the failure rate is high. The fault does not prompt the user where the fault is, which brings a certain degree of difficulty to the maintenance; secondly, the cooler in this application can only operate according to the control program and parameters set in the module controller, and the user cannot operate during use. Modification of the parameters in the module controller, such as the main transformer oil temperature, load current or cooler fan rotation time cannot be modified, the function is single and the applicability is not strong; again, the control device of this application can only be carried out locally Manual or automatic control, it is inconvenient to realize remote centralized monitoring for the situation where the coolers are scattered.

Contents of the invention

The purpose of the present invention is to provide a monitoring device and working method of the main transformer air-cooling system which can monitor in an intuitive manner with low failure rate in time.

In order to achieve the above object, the monitoring device of the main transformer air-cooled system of the present invention has a programmable controller, a drive control circuit connected to the control signal output end of the programmable controller; its structural feature is that the programmable controller has a digital Signal terminal: The digital signal of oil temperature and load current digital signal of the main transformer where the air-cooling system of the main transformer is received by the programmable controller is transmitted to each oil pump in the cooler of the air-cooling system of the main transformer through the drive control circuit according to the digital signal terminal. and fan inputs are automatically controlled; the fault signal input terminal of the programmable controller is connected with a CPLD fault detection circuit to detect possible phase loss, overload or short circuit faults of each oil pump and fan in the cooler, and through the drive control circuit Cut off the oil pump and fan with the above fault.

Further, the present invention also has a touch screen bidirectionally electrically connected with the programmable controller, so as to artificially set various parameters in the programmable controller, and simultaneously record and display the fault information of the cooler, the oil temperature of the main transformer, etc. and load current.

In the above technical scheme, the CPLD failure detection circuit comprises a CPLD phase loss detection circuit, a CPLD overload detection circuit and a CPLD short circuit detection circuit; The fault signal input terminal, the overload signal input terminal and the short circuit signal input terminal are connected.

The above-mentioned CPLD phase loss detection circuit includes a precision transformer circuit, a rectifier circuit, a comparison circuit, a CPLD and a drive circuit connected in series; the precision transformer circuit can generate phase Corresponding to each group of induced currents, the induced currents output corresponding state signals after the rectification circuit and the comparison circuit, and the CPLD can judge whether there is a phase loss in the oil pump and the fan in the cooler of the air-cooled system of the main transformer according to the state signals Fault, and the judged phase loss fault signal is sent to the phase loss fault signal input terminal of the programmable controller after the drive circuit.

Further, the circuit structure of the CPLD overload detection circuit and the CPLD short circuit detection circuit is the same as that of the CPLD phase loss detection circuit.

Further, the programmable controller of the present invention is connected with a running state detection circuit; the programmable controller detects the power state of the main transformer air-cooling system and the circulation state of the main transformer cooling oil through the running state detection circuit.

Further, the indication signal output end of the programmable controller of the present invention is connected with an indicator light circuit.

Further, the manual control input terminal of the programmable controller of the present invention is connected with a manual control circuit, and the manual control circuit includes a remote/local selection switch, an automatic/manual selection switch and control switches corresponding to each oil pump and fan in the cooler .

Further, the communication end of the programmable controller of the present invention is also electrically connected to the remote monitoring center through the communication module; the digital signal end of the programmable controller is the communication end of the programmable controller; the remote monitoring center sends the control signal and the oil temperature value signal of the main transformer and the load current value signal are sent to the communication terminal of the programmable controller through the communication module.

The working method of the monitoring device of the main transformer air cooling system of the present invention comprises:

The communication terminal of the programmable controller receives the oil temperature digital signal and the load current digital signal of the main transformer where the air cooling system of the main transformer is located in the remote monitoring center;

The programmable controller automatically controls the inputs of each oil pump and fan in the cooler of the air-cooled system of the main transformer through the drive control circuit according to the main transformer oil temperature and load current;

The programmable controller detects the possible phase loss, overload or short circuit faults of each oil pump and fan in the cooler through the CPLD phase loss detection circuit, CPLD overload detection circuit and CPLD short circuit detection circuit in the CPLD fault detection circuit, and controls the The circuit cuts off the oil pump and blower with said fault.

Among them, the touch screen connected bidirectionally with the programmable controller can control the parameters in the programmable controller such as: main transformer oil temperature upper limit, oil temperature lower limit, oil temperature hysteresis, load current upper limit, load current The lower limit value, load current hysteresis and rotation time can be set manually, and the operating status information and fault information of the oil pump and fan in the cooler of the main transformer air-cooled system can be recorded and displayed, as well as the main transformer oil temperature value and load current value.

Among them, the CPLD phase loss detection circuit, the CPLD overload detection circuit and the CPLD short circuit detection circuit detect the fault by detecting the magnitude of the induced current of the precision transformer circuit.

Among them, the manual control input terminal of the programmable controller is connected with a manual control circuit, and the manual control circuit includes a remote/local selection switch, an automatic/manual selection switch and control switches corresponding to each oil pump and fan in the cooler; manual control The circuit can selectively control the control mode of the programmable controller and the operation of the cooler of the air-cooled system of the main transformer.

Among them, the programmable controller sends the operation status information and fault information of each oil pump and fan in the cooler to the remote monitoring center through the communication module.

Compared with the prior art, the above-mentioned technical solution of the present invention has the following positive effects:

(1) The monitoring device of the main transformer air cooling system of the present invention adopts the CPLD fault detection circuit, and judges whether the measured oil pump or the blower fan have phase loss, overload or short circuit faults according to the size of the induced current generated by the precision transformer circuit, and solves the problem The problem of high failure rate caused by the use of traditional detection components. (2) The touch screen that the present invention adopts can artificially set and record the parameters in the programmable controller, and displays the operating status information and fault information about the measured oil pump or blower fan, so that on-site monitoring becomes very intuitive, The practicability and ease of use of the main transformer air-cooling system of the present invention are improved. (3) The communication terminal of the programmable controller among the present invention is electrically connected with the remote monitoring center bidirectionally through the communication module, so that the oil temperature and the load current signal of the main transformer received by the programmable controller are digital signals, further improving the monitoring precision and reliability. At the same time, the remote monitoring center can visually monitor the working status information and fault information of each oil pump and fan in the cooler, and can perform remote control on each oil pump and fan in the cooler, realizing the combination of remote monitoring and local monitoring .

Description of drawings

Fig. 1 is a circuit block diagram of the present invention.

FIG. 2 is a circuit block diagram of the CPLD fault detection circuit in FIG. 1 .

FIG. 3 is a circuit block diagram of the CPLD phase loss detection circuit in FIG. 2 .

FIG. 4 is a schematic circuit diagram of the CPLD phase loss detection circuit in FIG. 3 .

Detailed ways

Example 1

See Fig. 1, the monitoring device of the air-cooled system of the main transformer of the present embodiment has a programmable controller 1, an indicator light circuit 2, a manual control circuit 3, a touch screen 4, an operating state detection circuit 6, a CPLD fault detection circuit 7, a drive control circuit 8. The communication terminal of the programmable controller 1 is bidirectionally electrically connected with the remote monitoring center 51 via the communication module 50 .

PLC programmable controller 1 adopts FX2N-80MR-001 of Mitsubishi Corporation, and FX2N-16EX of Mitsubishi Corporation is connected to the I/O expansion port of FX2N-80MR-001. The communication terminal of FX2N-16EX is connected with a communication module 50, and the communication module 50 adopts FX-485PC-IF of Mitsubishi Corporation.

The indication signal output end of the programmable controller 1 is connected with an indicator light circuit 2 which can indicate to the user the operating status or fault location of the air-cooling system of the main transformer. Indicator light circuit 2 includes: cooler fan failure signal light, cooler fan operation signal light, cooler oil pump failure signal light, cooler oil pump operation signal light, power failure indicator light, power supply monitoring indicator light, high oil temperature indicator light, and high current indicator light , Short circuit fault indicator light, contactor fault indicator light, automatic indicator light and manual indicator light, etc. The above-mentioned signal lights or indicator lights are connected in series with corresponding output ends of the programmable controller 1 .

The manual control input terminal of the programmable controller 1 is connected with a manual control circuit 3, and the manual control circuit 3 includes a remote/local selection switch, an automatic/manual selection switch and a control switch corresponding to the cooler 9 of the main transformer air cooling system ; The manual control circuit 3 can selectively control the control mode of the programmable controller 1 and the operation of the cooler 9 of the main transformer air-cooled system.

The touch screen 4 is electrically connected to the programmable controller 1 bidirectionally. Through the touch screen 4, the user can adjust the parameters in the programmable controller 1 such as the upper limit value of the main transformer oil temperature, the lower limit value of the oil temperature, the hysteresis of the oil temperature, the upper limit value of the load current, the lower limit value of the load current, and the hysteresis of the load current. The fault information of the oil pump and fan in the cooler 9 of the air-cooled system of the main transformer, the oil temperature of the main transformer and the load current can be recorded and displayed manually.

The programmable controller 1 is also connected with a running state detection circuit 6; the running state detection circuit 6 includes an oil flow relay for detecting the cooling oil circulation state, an AC relay for detecting the power state, and an oil flow relay arranged on the programmable controller 1. High temperature, low oil temperature and high load current input contacts, etc. The programmable controller 1 detects the power state of the main transformer air-cooled system, the state of the cooling oil circulation of the main transformer, the state of oil temperature and the state of the load current through the operating state detection circuit 6, and passes the state information through the indicator light circuit 2 and the touch screen. 4 show outwards.

The drive control circuit 8 is connected to the control signal output end of the programmable controller 1, and the drive control circuit 8 includes an AC contactor control coil and a setting for controlling the cooler 9 connected in series at the cooler control output end of the programmable controller 1. AC contactor contacts and the like at the cooler 9 power supply end.

See Fig. 2, the fault signal input end of programmable controller 1 is connected with CPLD fault detection circuit 7, CPLD fault detection circuit 7 comprises CPLD phase loss detection circuit 71, CPLD overload detection circuit 72 and CPLD short circuit detection circuit 73.

Referring to FIG. 3 and FIG. 4 , the CPLD phase loss detection circuit 71 includes a precision transformer circuit 711 , a rectification circuit 712 , a comparison circuit 713 , a CPLD 714 and a drive circuit 715 connected in series.

In this embodiment, the CPLD714 adopts the CPLD whose model is EPM7128SL8-15. Other ASIC application-specific integrated circuits can also be used, including CPLD complex programmable logic devices and FPGA field programmable gate arrays.

The CPLD overload detection circuit 72 and the CPLD short circuit detection circuit 73 adopt the same circuit structure as the CPLD phase loss detection circuit 71 .

The programmable controller 1 detects the running state of each oil pump and fan in the cooler 9 of the air-cooled system of the main transformer and the circulation state of the cooling oil of the main transformer through the running state detection circuit 6 .

The remote monitoring center 51 sends the digital signal of the oil temperature and the digital signal of the load current of the main transformer where the air-cooled system of the main transformer is located to the digital signal terminal of the programmable controller 1, that is, the communication terminal, through the communication module 50 .

There are 4 coolers 9 in the main transformer air-cooling system in this embodiment, and each cooler has 1 oil pump and 2 blowers. Therefore, there are 12 3-phase AC motors in the cooler 9, and 36 power supply inlet terminals in total.

During the work of the monitoring device of the air-cooled system of the main transformer, the programmable controller 1 judges whether the working power of the air-cooled system of the main transformer is normal, if normal, then puts into the working power; if not normal, then puts into the standby power and prompts to work Power failure information. The communication terminal of the programmable controller 1 receives the oil temperature digital signal and the load current digital signal of the main transformer where the air-cooled system of the main transformer is located in the remote monitoring center 51; the programmable controller 1 according to the main transformer oil temperature and load current Through the drive control circuit 8, the inputs of the oil pumps and blowers in the cooler 9 of the main transformer air-cooling system are automatically controlled. The programmable controller 1 detects respectively the possible phase loss, overload or short circuit of each oil pump and fan in the cooler 9 through the CPLD phase loss detection circuit 71, the CPLD overload detection circuit 72 and the CPLD short circuit detection circuit 73 in the CPLD fault detection circuit 7 Fault, and cut off the oil pump and fan that have the fault through the drive control circuit 8. At the same time, the programmable controller 1 sends the operation status information and fault information of each oil pump and fan in the cooler 9 to the remote monitoring center 51 through the communication module 50 .

Among them, when the programmable controller 1 automatically controls the inputs of the oil pumps and fans in the cooler 9, if the programmable controller 1 detects that the oil temperature of the main transformer is greater than the set lower limit of 45°C, the programmable controller 1 Put the working coolers in the cooler 9 of the main transformer air-cooled system, that is, three coolers into operation; is greater than the set upper limit, the programmable controller 1 will put the spare cooler in the cooler 9 of the main transformer air-cooled system, that is, the fourth cooler, into operation, and at the same time, the high oil temperature indicator light in the indicator circuit 2 is on or The high current indicator light is on; the oil temperature of the main transformer to be measured is less than 55°C, that is, the difference between the upper limit of the oil temperature setting of 65°C and the return difference of the oil temperature is 10°C; or the measured load current of the main transformer is less than the load When the difference between the upper limit value of the current setting and the hysteresis of the load current is reached, the programmable controller 1 cuts off the standby cooler in the cooler 9 of the air-cooled system of the main transformer.

When the running time of the currently running coolers in the coolers 9 of the main transformer air-cooling system reaches the preset shift time, the programmable controller 1 will switch the one with the longest current running time among the coolers 9 of the main transformer air-cooling system The cooler is cut off, and at the same time, the spare cooler in the cooler 9 of the main transformer air-cooling system, that is, the fourth cooler that can work normally, is put into operation.

When the programmable controller 1 cuts off the power supply of the cooler with the fault through the drive control circuit 8, the programmable controller 1 controls the standby cooler, that is, the fourth cooler that can work normally, to be put into operation. At the same time, the programmable controller 1 prompts that a fault occurs through the indicator light circuit 2 , and sends the fault information to the touch screen 4 and the remote monitoring center 51 . The fault information includes the serial number and fault type of the motor of the oil pump or blower that has failed, so that maintenance personnel can find the faulty motor in time and perform corresponding repairs in time.

The user selects remote automatic control, local manual control or local automatic control through the remote/local selection switch and automatic/manual selection switch in the manual control circuit 3 . When the remote automatic control mode is selected, the remote monitoring center 51 sends the control signal to the programmable controller 1 through the communication module 50, and the programmable controller 1 controls each of the coolers 9 according to the control signal from the remote monitoring center 51. The operation of oil pumps and fans; when the local manual control mode is selected, the user can control the operation of each oil pump and fan in the cooler 9 through the cooler control switch in the manual control circuit 3; when the local automatic control mode is selected, the user can The programming controller 1 automatically controls the operation in the cooler 9 of the main transformer air-cooling system according to the main transformer oil temperature and load current where the main transformer air-cooling system is located.

The user can set the upper limit value of main transformer oil temperature, the lower limit value of oil temperature, the hysteresis of oil temperature, the upper limit value of load current, the lower limit value of load current, the hysteresis of load current and the rotation Time parameters; at the same time, the programmable controller 1 performs automatic control according to the set parameters.

Still see Fig. 4, in CPLD open-phase detection circuit 71, corresponding to described 36 power supply inlet terminals of cooler 9, precision transformer circuit 711 comprises 36 current transformers, and rectification circuit 712 comprises 36 rectifiers, The comparison circuit 713 includes 36 comparators. Wherein, the precision transformer circuit 711 is arranged on each phase power inlet end of each oil pump and blower fan (that is, 12 3-phase AC motors in the cooler 9) in the cooler 9, and generates a 12 groups of induced currents corresponding to 12 sets of 3-phase AC motors, each group of induced currents includes 3 phases; the 12 groups of induced currents are respectively output through each rectifier in the rectifier circuit 712 and each comparator in the comparison circuit 713 Corresponding to 12 groups of status signals, each group of status electrical signals includes 3 phases. The CPLD714 can judge whether the oil pump and the fan in the cooler 9 of the air-cooled system of the main transformer have an open-phase fault according to the state signal. Among them, if the three phases in a group of status signals are all in the high level state, the oil pump or fan corresponding to the group of status signals is normal; on the contrary, if one or two phases in a group of status signals are in the low level state , the oil pump or fan corresponding to this group of status signals is out of phase. Then the CPLD 714 sends the judged phase loss fault signal to the input terminal of the phase loss fault signal of the programmable controller 1 through the drive circuit 715 . Wherein, the driving circuit 715 includes 12 driving circuits, and the 12 driving circuits respectively correspond to the oil pumps and fans in the cooler 9 . The 12-way driving circuit includes triodes and photocouplers. The output terminals of the 12-way driving circuits, that is, the output terminals of the photocouplers, are connected to the 12 interfaces of the phase-loss fault signal input terminals of the programmable controller 1 . Finally, the programmable controller 1 prompts that a fault occurs through the indicator light circuit 2 , and sends the fault information to the touch screen 4 and the remote monitoring center 51 .

The CPLD overload detection circuit 72 and the CPLD short circuit detection circuit 73 adopt the same circuit structure as the CPLD phase loss detection circuit 71 .

When the CPLD overload detection circuit 72 performs overload fault detection, the precision transformer circuit can generate corresponding induction currents according to the operating currents of each phase of each oil pump and fan in the cooler 9, and the induction currents are respectively passed through the rectification circuit and the comparison circuit. Corresponding groups of status signals are output, and each group of status electrical signals includes 3 phases. Wherein, the comparison reference level set by the comparison circuit of the CPLD overload detection circuit 72 is 1.5 times of that of the comparison circuit in the CPLD overload detection circuit 71, so as to meet the requirement of overload detection. According to the state signal, the CPLD can determine which specific oil pump or blower in the cooler 9 of the air-cooled system of the main transformer has an overload fault. Among them, if the three phases in a group of status signals are all in the high level state, the oil pump or fan corresponding to the group of status signals is overloaded; on the contrary, if the three phases in a group of status signals are in the low level state, then The oil pump or fan corresponding to this group of status signals is normal. Then the CPLD sends the judged overload fault signal to the input terminal of the overload fault signal of the programmable controller 1 through the driving circuit. Wherein, each drive in the drive circuit corresponds to each oil pump and fan in the cooler 9 respectively. The drivers of each channel include triodes and photocouplers. The output terminals of the various drivers, that is, the output terminals of the photocouplers, are connected to 12 interfaces of the overload fault signal input terminals of the programmable controller 1 . Finally, the programmable controller 1 prompts that a fault occurs through the indicator light circuit 2 , and sends the fault information to the touch screen 4 and the remote monitoring center 51 .

When the CPLD short-circuit detection circuit 73 performs short-circuit fault detection, the precision transformer circuit can generate corresponding induction currents according to the operating currents of each phase of each oil pump and blower fan in the cooler 9, and the induction currents are respectively passed through the rectification circuit and the comparison circuit. Corresponding groups of status signals are output, and each group of status electrical signals includes 3 phases. Wherein, the comparison reference level set by the comparison circuit in the CPLD short-circuit detection circuit 72 is three times that of the comparison circuit in the CPLD short-circuit detection circuit 71, so as to meet the requirement of short-circuit detection. The CPLD can determine which specific oil pump or fan in the cooler 9 of the air-cooled system of the main transformer has a short-circuit fault according to the state signal output by the comparison circuit. Among them, if one or two phases in a group of status signals are in the high level state, and the remaining two phases or one phase are in the low level state, then the oil pump or fan corresponding to the group of status signals is short-circuited; If the three phases in the state signal are all in low level state, then the oil pump or fan corresponding to this group of state signals is normal. Then the CPLD sends the judged short-circuit fault signal to the input terminal of the short-circuit fault signal of the programmable controller 1 through the drive circuit. Wherein, each drive in the drive circuit corresponds to each oil pump and fan in the cooler 9 respectively. The drivers of each channel include triodes and photocouplers. The output terminals of the various drivers, that is, the output terminals of the photocouplers, are connected to 12 interfaces of the short-circuit fault signal input terminals of the programmable controller 1 . Finally, the programmable controller 1 prompts that a fault occurs through the indicator light circuit 2 , and sends the fault information to the touch screen 4 and the remote monitoring center 51 .

In this embodiment, the oil temperature signal and the load current value signal of the main transformer where the main transformer air cooling system is located are sent to the programmable controller 1 through the communication module 50 . In other embodiments, other approaches may also be used.

Example 2

The difference between this embodiment and Embodiment 1 is that the CPLD fault detection circuit 7 includes a CPLD phase loss detection circuit 71 , a traditional overload detection circuit and a traditional short circuit detection circuit. The traditional overload detection circuit adopts thermal relays arranged on the power line ends of each phase of each oil pump and blower fan in the cooler 9, and the contacts of each thermal relay are arranged on the overload fault signal input end of the programmable controller 1; the traditional short circuit detection The circuit adopts an automatic air switch arranged at each phase power inlet end of the cooler 9 .

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And these obvious changes or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims (12)

1. A monitoring device for an air-cooled system of a main transformer, comprising a programmable controller (1) and a drive control circuit (8) connected to the control signal output end of the programmable controller (1); The programmable controller (1) has a digital signal terminal; the digital signal of the oil temperature and the digital signal of the load current of the main transformer where the air-cooling system of the main transformer is located is received by the programmable controller (1) through the drive control circuit (8) Automatically control the inputs of each oil pump and blower fan in the cooler (9) of the main transformer air-cooled system; The fault signal input terminal of the programmable controller (1) is connected with a CPLD fault detection circuit (7) to detect possible phase loss, overload or short-circuit faults of the oil pumps and fans in the cooler (9), and through the drive control circuit (8) there will be the oil pump and blower blower removal of described fault; CPLD failure detection circuit (7) comprises CPLD phase loss detection circuit (71), CPLD overload detection circuit (72) and CPLD short circuit detection circuit (73); CPLD phase loss The detection circuit (71), the CPLD overload detection circuit (72) and the CPLD short circuit detection circuit (73) are respectively connected with the phase loss fault signal input end, the overload signal input end and the short circuit signal input end of the programmable controller (1); It is characterized in that: the above-mentioned CPLD phase loss detection circuit (71) includes a precision transformer circuit (711), a rectification circuit (712), a comparison circuit (713), a CPLD (714) and a drive circuit (715) connected in series in sequence; The transformer circuit (711) generates corresponding sets of induced currents according to the respective phase operating currents of the oil pumps and blowers in the cooler (9), and the induced currents are passed through the rectification circuit (712) and the comparison circuit (713). After outputting the corresponding state signal, CPLD (714) can judge whether the oil pump and the fan in the cooler (9) of the main transformer air-cooled system have a phase failure according to the state signal, and will judge the phase failure signal After the drive circuit (715), it is sent to the phase loss fault signal input terminal of the programmable controller (1). 2. The monitoring device of the main transformer air-cooling system according to claim 1, characterized in that: it also has a touch screen (4) that is electrically connected to the programmable controller (1) bidirectionally to control the programmable controller (1) Various parameters in the system are set manually, and at the same time, the fault information of the cooler, the main transformer oil temperature and the load current are also recorded and displayed. 3. The monitoring device of the main transformer air-cooled system according to claim 1, characterized in that: the circuit structure of the CPLD overload detection circuit (72) and the CPLD short circuit detection circuit (73) is the same as that of the CPLD phase loss detection circuit (71 )same. 4. The monitoring device of the main transformer air-cooled system according to claim 1, characterized in that: the programmable controller (1) is connected with a running state detection circuit (6); the programmable controller (1) passes the running state detection The circuit (6) detects the power state of the main transformer air cooling system and the circulation state of the main transformer cooling oil. 5. The monitoring device for the air-cooled system of the main transformer according to claim 1, characterized in that: the indication signal output end of the programmable controller (1) is connected with an indicator light circuit (2). 6. The monitoring device of the air-cooled system of the main transformer according to claim 1, characterized in that: the manual control input terminal of the programmable controller (1) is connected with a manual control circuit (3), and the manual control circuit (3) includes Distant place/on-the-spot selector switch, automatic/manual selector switch and the corresponding control switch with each oil pump and blower fan in cooler (9). 7. The monitoring device of the main transformer air-cooled system according to claim 1, characterized in that: the communication terminal of the programmable controller (1) is also bidirectionally electrically connected to the remote monitoring center (51) through the communication module (50); The digital signal terminal of the programmable controller (1) is the communication terminal of the programmable controller (1). 8. The working method of the monitoring device of the main transformer air-cooling system according to any one of claims 1-7, comprising: The communication terminal of the programmable controller (1) receives the oil temperature digital signal and the load current digital signal of the main transformer where the air cooling system of the main transformer is located in the remote monitoring center (51); The programmable controller (1) automatically controls the inputs of each oil pump and fan in the cooler (9) of the air-cooled system of the main transformer through the drive control circuit (8) according to the oil temperature and load current of the main transformer; Programmable controller (1) detects each in cooler (9) respectively by CPLD phase loss detection circuit (71), CPLD overload detection circuit (72) and CPLD short circuit detection circuit (73) in CPLD failure detection circuit (7). Oil pumps and fans may have phase loss, overload or short-circuit faults, and the oil pumps and fans with the faults are cut off through the drive control circuit (8). 9. The working method of the monitoring device of the main transformer air-cooled system according to claim 8, characterized in that: the touch screen (4) electrically connected to the programmable controller (1) in both directions can control the programmable controller (1) The main transformer oil temperature upper limit, oil temperature lower limit, oil temperature hysteresis, load current upper limit, load current lower limit, load current hysteresis and rotation time are artificially set, and the main transformer is recorded and displayed. The operating status information and fault information of the oil pump and fan in the cooler (9) of the variable air cooling system, as well as the oil temperature value and load current value of the main transformer. 10. The working method of the monitoring device of the main transformer air-cooled system according to claim 8, characterized in that: the CPLD phase loss detection circuit (71), the CPLD overload detection circuit (72) and the CPLD short circuit detection circuit (73) pass Detect the magnitude of the induced current of the precision transformer circuit for fault detection. 11. The working method of the monitoring device of the main transformer air-cooled system according to claim 8, characterized in that: the manual control input terminal of the programmable controller (1) is connected with a manual control circuit (3), and the manual control circuit ( 3) Including remote/local selection switch, automatic/manual selection switch and control switches corresponding to each oil pump and fan in the cooler (9); the manual control circuit (3) can control the programmable controller (1) Mode and the operation of the cooler (9) of the main transformer air-cooled system are selected and controlled. 12. The working method of the monitoring device of the main transformer air-cooled system according to claim 8, characterized in that: the remote monitoring center (51) passes the control signal and the oil temperature value signal and load current value signal of the main transformer through The communication module (50) is sent to the communication terminal of the programmable controller (1); at the same time, the programmable controller (1) transmits the operating status information and fault information of each oil pump and fan in the cooler (9) through the communication module (50) Send to remote monitoring center (51).

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