Engineer story sharing(11)

I have dealt with the problem of EMC in the wind turbine. The general wind farm environment is relatively windy, summer is good, it is really cold in the winter, so the environment is relatively bad, but I am most impressed once, still An experience of wind turbine inspections on a land wind farm in the mountains in March.


        The user is using our product for the first time. Only one fan is installed for field test. As a result, the MODBUS communication on the site is unstable. If it cannot be processed in time, the subsequent cooperation will be difficult to carry out, so we need to go to the site. EMC inspection.


        The wind farms I have been to are on the grasslands or on the Gobi Desert. But when I arrived at the scene, I discovered that the wind farm is on the top of the mountain. The whole mountain range is a wind farm. All the wind turbines are on the hill. It is hard to imagine these. How is the fan erected on the hill?
     Since the fan is on the top of the mountain, it must be driven by car.


        The mountain has just been snowed recently, and the altitude is relatively high, so there is still some snow on the mountain. If you encounter a landslide on the road, you have to wait for the road to open before you can continue.
     After two hours of bumps, I finally reached the foot of the fan. Because the road was muddy, the car could not be driven up. In the end, the tens of meters could only go up.
        Get out of the car and take the tool to the fan. The weather began to become gloomy and it felt like it was going to snow. A few tens of meters of road, the hands are frozen, the breathing is difficult, the deep one foot is shallow, the key is that the wind blows on the face and hurts - this is the wind field. . .
       Finally entering the fan, you can start working.


        Because of the MODBUS communication problem, we checked some aspects that may affect communication, such as the grounding treatment of the cabinet, the handling of the shielding layer of the cable, etc., which are basically more standardized.
       On the terminal block of the MODBUS communication module of the ET200S, an external terminating resistor can be seen, which is verified to be 120 ohms.
        However, the communication partner is a meter that supports the MODBUS protocol. The installation position is relatively deep, and there is no terminal resistance. After confirmation, there is no terminating resistor.


        In addition, we detected the interference on the communication cable. Through the oscilloscope, we can see that there are some interference pulses on the cable when the device starts. In normal operation, no large interference signal is detected on the communication cable.
        In order to prevent surges on the communication cable, we added a lightning arrester for testing.


       However, after the increase, the communication is unreasonable, so the arrester is cancelled and the original wiring is restored. It can be seen that the lightning arresters on site are not free to add.


        From the situation of on-site EMC detection, there are two main problems: 1 terminal resistance mismatch; 2 interference during startup. Therefore, it is recommended that the user perform matching processing on the terminating resistor, and additionally consider the communication cable to redesign the wiring.


        It took nearly six hours for the entire inspection process. When we opened the fan door, we found that there was thick snow on the outside.


        Under the guarantee of the driver's skillful driving skills, we finally flew down from the snowy mountains in the night. The reason why it can fly down is because the driver's master has been accompanied by maintenance personnel numerous times to go to various hills. According to him, today's snow is not the biggest. . .
      The whole experience of this on-site service made me unforgettable. But what makes me even more admirable is that many ordinary people who are ordinary people who overcome the harsh natural environment, always keep their own work and even risk to ensure the normal operation of the fan equipment, so please cherish us. Environment, saving every point of energy, because they come really not easy!
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