Automatic measurement and control system technolog

2022-08-24
  • Detail

Tongjiezi power station is located in Shabian, Leshan City, which can meet the application requirements for the repeatability of this pendulum impact experimental machine. It is the last stage of the cascade development of the Dadu River. It is under the jurisdiction of Gongzui Hydropower Plant, about 33 km away from the upstream Gongzui power station and 32 km away from the base of Shawan power plant. The installed capacity of the whole station is 4150 MW, which is the exposed powerhouse behind the dam, and the unit and transformer are typical unit wiring; The capacity of the main transformer is 180000 KVA, and the cooling mode is forced oil circulation air cooling, with a total of 5 coolers

due to the early design, there have been many defects in the automatic control system of the main transformer cooler of the power station in terms of measurement and control methods, control elements and peripheral measurement elements for a long time. In the operation of previous years, there have been many failures in the control of automatic control devices, resulting in the failure of the cooler to start automatically; There is no signal output when there is a large amount of oil leakage in the main transformer body, resulting in the forced power failure of the whole power generation unit; The technology of the measurement part is backward and has been seriously damaged, so that the protection function and the function of self starting the cooler according to load and temperature cannot be realized when the temperature of the main transformer rises. It has laid a great hidden danger for safety production. At the same time, the oil level and temperature of the main transformer must rely on manual regular patrol inspection, recording and regular cooler switching operation, which cannot meet the requirements of unattended (few people on duty) operation of hydropower plants. In order to solve the above problems, the system can meet the requirements of unattended (few people on duty) operation mode. Our factory decided to reform the automatic measurement and control system of the main transformer cooler

after more than half a year of investigation and data collection, and after full research and demonstration, the company, together with Sichuan Zhongding Electric Control Co., Ltd. and Sichuan electric power test and Research Institute, jointly developed a new type of automatic measurement and control system for power air-cooled transformer cooler (tcpc-f automatic control device) by using programmable controller. After more than half a year, the device was officially put into use in the 11 main transformer of the power station in November 1997. The actual production and operation test shows that the device can fully meet the pre design requirements, fundamentally solve the problems existing in the original device 0.36 ~ 0.40, and meet the requirements of unattended (few people on duty) and computer monitoring

2 development principle of measurement and control system

in order to meet the technical requirements of the new situation, the developed device must adopt new technologies, new methods and new devices. In addition, the new system should completely change the traditional measurement and control mode, requiring high degree of automation, reliable operation, complete functions, relatively perfect self-control, protection and information transmission functions, can adapt to various operating conditions of the main transformer, and achieve the purpose of maintenance free and no operation

3 technical difficulties in the development of measurement and control system

first, the measurement and control device should be able to control the start and stop of the cooler according to the temperature value sent by the temperature switch and temperature sensor, and at the same time, the start and stop of each cooler should meet the conditions for symmetrical heat dissipation of the transformer required by the manufacturer; Second, in order to ensure reliable action when the oil temperature of the main transformer rises, avoid MIS tripping the switch due to the misoperation of the measuring elements, and automatically send a signal when any temperature sensor or temperature switch fails

4 hardware configuration and technical indicators of the system

the measurement and control system of main transformer cooler is composed of six main parts:

(1) tcpc-f automatic measurement and control device of main transformer cooler

the measurement and control device includes: FX MT programmable controller, 4 ad module, switching power supply, relay and other peripheral parts

plc input: 4 analog quantities, 40 switching quantities

plc output: 40 channel switching value

uplink LCU: 12 channel switching value

contact capacity: 220 vdc/5a

measurement accuracy: 0.5%

power supply: three 220 10% VAC

working mode: continuous

working environment: temperature 0 ~ 55 ℃, relative humidity: 95%

(2) temperature transmitter

model: jump-p T100 (Germany)

working pressure: 300 kPa

temperature adjustment range: 0 ~ 100 ℃

maximum allowable temperature: 100 ℃

output: DC4 ~ 20 mA

accuracy: 0.2% F.S

protection grade: IP65

(3) temperature switch

model: B (USA)

working pressure: 600 kPa

adjust the temperature range of 20.0: -15 ~ 105 ℃

maximum allowable temperature: 0 ~ 135 ℃

output: 2 SPDT, 3 SPDT

protection grade: IP65

(4) flow switch

model: fcs-g 1/2 an8 x (Germany)

pressure: 6 MPa

power supply: 24 VDC

working range: H201 ~ 150 cm/S

protection grade: IP67

(5) air switch, contactor, TK (including phase loss protection)

power supply: 3-phase AC

working voltage: 400 V

working current: 100 a, 15 a

(6) differential pressure transmitter

model: foxboro-841 (Shanghai)

range: 0 ~ 4 m water column

accuracy: 0.2% F.S

power supply: 24 VDC 20%

output: DC4 ~ 20 mA

5 the main control function of the device

the measurement and control core of TCPC system is PLC, which is responsible for the collection and processing of all information. When all monitoring switching values are sent to the PLC input port, and the temperature transmitter sends the measured temperature signal to the special a/d conversion module of PLC for data processing, the device completes the automatic measurement of the oil temperature of the main transformer and the automatic control of the cooler according to the prefabricated program

its operation mode is not only automatically adjusted according to the oil temperature of the main transformer, but also automatically performs periodic switching one by one. When the cooler fails in operation, the measurement and control device can automatically switch the working standby state; At the same time, send up the alarm signal

according to the design, the whole device completes the automatic control of the main transformer cooling system, realizes the automatic start and stop of the oil pump and cooler, and maintains the oil temperature of the main transformer within the normal working range. According to the actual operation, once the main transformer is put into operation, three coolers will be put into operation as the basic cooling load, and the other two as automatic regulation. At the same time, start the cooler according to the symmetrical heat dissipation conditions, specifically: when only three coolers are running, the combination mode is ① ③ ④, ② ④ ⑤, ① or ② ③ ⑤. When four coolers are running, the combination mode is ① ② ④ ⑤, ① ② ③ ⑤, ① ② ③ ④, and it can be switched automatically and regularly

5.1 according to the power adjustment function

plc will start and adjust the remaining two coolers according to the set value information of power transmitter and temperature transmitter; When the load of the main transformer increases rapidly (the generator has 50% - 100% load), the PLC will give priority to the information of the power transmitter, supplemented by the gradient value of oil temperature rise, and then start one or two coolers involved in the regulation

5.2 according to the oil temperature regulation function of the main transformer

plc focuses on the set temperature value sent by the ecological balance of hard bubbles in the field of thermal insulation at the 2015 international polyurethane Exhibition (UTECH Europe) according to the temperature transmitter Bayer Material Technology. It can start and stop the regulation of the remaining two coolers, and can be switched automatically at a fixed time

when the oil temperature of the main transformer operates in the range of 50 ~ 55 ℃, the cooler can no longer be started. If the oil temperature rises to 60 ℃, PLC commands to start a cooler; When the oil temperature continues to rise to 65 ℃, PLC will command to start a cooler; When all coolers are put into operation, the oil temperature will continue to rise to more than 75 ℃. At this time, PLC will delay the segmented alarm and send the alarm signal to the computer monitoring system. On the contrary, when the oil temperature drops from 65 ℃ to 55 ℃ during operation, PLC will stop two coolers one by one

5.3 cooler full stop protection function

the normal full stop operation of the cooler should meet the following requirements: the unit oil switch jumps, the main transformer oil temperature drops to the temperature switch reset contact action (50 ℃), and PLC also judges that the temperature switch action sequence (from high to low) is consistent with the information sent by the power transmitter (power is zero). Otherwise, the cooler will remain in operation

the operation of the main transformer shall meet the following requirements: ① the cooler shall be stopped due to all faults, with a delay of 60 min; ② When all coolers fail and shut down, and the oil temperature of the main transformer rises to 75 ℃, the temperature sensor and the temperature switch will act in association (75 ℃), and the PLC outlet will trip and send a trip signal when the situation occurs with a delay of 10 minutes. When the oil temperature is close to the trip temperature, PLC can send an alarm signal first

5.4 main transformer oil temperature rise protection function

in order to ensure the reliable emergency shutdown action when the main transformer oil temperature rises, for the correct action of three temperature switches and one temperature sensor, the measurement and control device not only performs self inspection and mutual inspection on the temperature measuring elements; It is also necessary to perform two out of three related actions between the two (that is, when more than two outputs of two temperature switches and one temperature sensor reach the set value of emergency temperature, the device will output the emergency action signal to the trip circuit.)

① when the oil temperature is 75 ℃, the measurement and control device will send a signal to the main transformer trip circuit with a delay of 1 h

② when the oil temperature of the main transformer is 75 ℃, but all coolers fail or the two sections of power supply disappear, the signal is sent to the main transformer trip circuit after a delay of 10 min

③ when the oil temperature reaches 80 ℃, the measurement and control device will immediately send a signal to the main transformer trip circuit

5.5 the automatic measurement and control device can monitor the power supply of the main transformer cooler and automatically control the switching

6 conclusion

with the joint efforts of Gongzui Hydropower Plant, Sichuan Zhongding Electric Control Co., Ltd. and Sichuan electric power test and Research Institute, the automatic measurement and control system has completed the functional research and development of the entire automatic measurement and control system and has been successfully put into use in Tongjiezi power station. After more than one year of operation, it has been proved that the equipment is safe, stable and reliable, which eliminates the phenomenon of high failure rate and unstable operation of this part of our factory, improves the automatic control function that could not be realized before, improves the safe operation rate of the main transformer, reduces the failure rate of the equipment, greatly reduces the maintenance work of this part of the equipment, and extends the service life of the equipment; Complete system performance and measurement and control function; All components and parts of the system are well selected, achieving the purpose of maintenance free and duty-free technical transformation; The whole system and peripheral automation components have strong outdoor protection ability, which can fully meet the requirements of unattended (few people on duty). In January, 1999, the expert appraisal committee organized by Sichuan Electric Power Company spoke highly of the device: it has obvious economic and social benefits, has extensive promotion and application value, and has played a positive role in promoting the automation process of hydropower plants

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