Practical purpose
A few days of understanding practice is both tense and fresh, because the unit we visited is where we will work in the future. Through practice, we personally feel the future working state, as well as the object of work and the knowledge used after work, which not only stimulates my enthusiasm for learning courses, but also urges us to continuously improve our ability to use knowledge and realize the shortcomings of classroom learning. In my opinion, practice has the following advantages:
First, understanding practice can cultivate our comprehensive thinking ability. The normal operation of power system needs to consider many factors. For example, the towers supporting transmission lines are divided into cable-pulling, vertical, stretching and leaping types, just to adapt to different environments. Insulators and fittings are indispensable for transmission lines, in order to eliminate the influence of gravity and wind.
Secondly, understanding practice can cultivate our ability to think and solve problems flexibly. The input high voltage line of the visited substation has to pass through three relays, two transformers and three switches with different gears, so that the working states of the two transformers can be controlled, which is convenient for inspection and maintenance.
Third, the internship cultivates our strong ability to read pictures and practice. Through internship, we have a more detailed understanding of how employees with the same major as us work. Although our knowledge is not very detailed due to the limited professional knowledge, we have a perceptual knowledge of what we will do in the future, which is more conducive to future theoretical study, and perceptual knowledge has risen to rational knowledge.
Practical content
Water injection station
I just heard that water will be injected into the underground after oil exploitation, but I never thought there would be so much knowledge about water injection before visiting the water injection station. What makes me even more unbelievable is that water injection needs unpolluted water. The measure to replenish and maintain reservoir pressure by injecting water into the reservoir with water injection wells is called water injection. After the oilfield is put into development, with the increase of exploitation time, the energy of the reservoir itself will be continuously consumed, resulting in the continuous decline of reservoir pressure. A large amount of underground crude oil is degassed, and the output of oil wells will be greatly reduced or even stopped, resulting in a large number of dead oil remaining underground. In order to make up for the underground deficit caused by crude oil production, maintain or improve the reservoir pressure, and achieve high and stable oil production, it is necessary to inject water into the oil field. The function of the water injection station is to turn all kinds of low-pressure water sent by the water supply system or treated to meet the requirements of injected water quality into high-pressure water needed for oilfield development through pumps. It is sent to the water injection trunk line through the high-pressure valve group, and then sent to the water injection well through the water distribution chamber to inject the oil layer. The water source of oil field water injection station is generally the water refined by refinery and the water from nearby rivers. The former needs to be purified before being transported to major oil fields and injected underground, while the latter can be directly injected underground. The water injection station mainly includes water storage tank, water supply pipeline, water injection pump house, water pump unit, high and low pressure water valves, power supply and distribution and lubrication system. Composition of cooling water system. The water injection mode, namely injection-production system, refers to the position of water injection wells in the reservoir and the arrangement relationship between water injection wells and production wells. According to the characteristics of the oilfield, the following water injection methods can be selected: edge water injection, which is divided into three types: edge water injection, edge water injection and edge water injection; Cutting and water injection; Regional water injection can be divided into five points, seven points, seven points, four points and nine points.
Substation and power supply training center
Our internship time is only five days, but the internship time in the substation is as long as one day, and the internship in the power supply training center takes up half a day, which shows the importance of power knowledge to our electrical specialty.
Substation is the place where the voltage and current of electric energy are converted, concentrated and distributed in the power system. Generally speaking, the voltage of electricity generated by power stations does not exceed one or two thousand volts. If direct long-distance transmission, the line current will be very large, which makes the power loss on the line very large, very uneconomical and the transmission power of the line is very low. Therefore, a transformer should be used to boost the voltage to tens of thousands or even hundreds of thousands of volts (depending on the distance and power). To reduce the line current. In order to connect power lines with different distances and powers to the power grid and increase the overall security, it is necessary to connect different levels of lines in multiple substations. Similarly, after the high-voltage power is delivered to the destination, it needs to be reduced to 10 kV and 6 kV to meet the needs of different users. 400V (that is, 380/220V) and other grades. So many substations are needed in practical application. The functions of substation can be summarized as the following five points: changing voltage level, collecting current, distributing electric energy, controlling the flow direction of electric energy and adjusting voltage. In order to ensure the power quality and equipment safety, voltage regulation, tidal current (the direction and distribution of voltage, current and power at each node and branch of the power system), transmission and distribution lines and main electrical equipment need to be protected in the substation. Substation is composed of main wiring, main transformer, high and low voltage distribution device, relay protection and control system, power consumption and DC system, telecontrol and communication system, necessary reactive power compensation device and main control room. Among them, the main wiring, main transformer and high and low voltage distribution devices belong to the primary system. The relay protection and control system, DC system, telecontrol and communication system are secondary systems. The main wiring is the most important part of the substation. It determines the function, operation quality, maintenance conditions and power supply reliability of the substation. Generally divided into single bus, double bus, one and a half circuit breaker connection, ring connection and other basic forms. The main wiring of the substation in Shengli Oilfield we visited adopts single bus sectional structure. The main transformer is the most important equipment in the substation. Its performance and configuration directly affect the advanced nature, economy and reliability of substation. The main transformer of substation usually adopts three-phase transformer. In addition, there are specific requirements for the selection and location of other equipment and the overall layout of the substation. Substation relay protection subsystem protection (including transmission line and bus protection) and component protection (including transformer, reactor and reactive power compensation device protection). Substation control methods are generally divided into two categories: direct control and selective control. The former refers to one-to-one button control. For substations with many control pairs, if the direct control mode is adopted, the number of control screens is too large and the control monitoring surface is too large, which is difficult to meet the operation requirements. At this time, a selective control method is needed. The selective control method has the advantages of large control capacity, centralized control and small control panel area. Disadvantages are poor intuition and many intermediate conversion links.
Two high-voltage power supplies are introduced into the substation, which are controlled by three relays. When a fault occurs, the high-voltage power supply can be input through different standby devices for maintenance. After the input voltage is transformed, the voltage is reduced from 1 10kv to 10kv. Transformer is the core equipment of substation, and the control room of substation is equipped with control equipment, which controls all instruments and equipment. There is also an advanced alarm function. At present, most substations use sulfur hexafluoride gas as insulation medium. Substations are also equipped with lightning protection equipment, mainly lightning rods and lightning arresters. Lightning rod is used to prevent substation from being directly struck by lightning and introduce lightning current into the earth. When lightning strikes the line near the substation, the lightning wave will enter the substation along the wire, resulting in overvoltage. In addition, the operation of the circuit breaker will also cause overvoltage. The function of lightning arrester is to automatically discharge the ground when the overvoltage exceeds a certain limit, and then automatically discharge the voltage protection equipment.
Power supply training center is a place to train electric power professionals. The training center we visited has trained many excellent electric power talents. Internship in the power supply training center, let us realize the basic skills that a senior electrician must have. We personally visited the examination room and deeply felt the atmosphere of the school. Finally, we have benefited a lot from safe rescue. The advanced simulated human rescue system gives us a preliminary understanding of the steps of electric shock rescue.
smeltery
The refinery is near our school. This visit is really the first time.
As we all know, crude oil mined underground cannot be used as raw material, and oil is a mixture. The role of the refinery is to separate the components in the mixture and divide them into components with different uses. With the more and more extensive exploitation, the salt content and water content of crude oil are also increasing gradually, so the requirements for water removal and desalination in refining process are getting higher and higher. The technological principle used in water and salt removal is that the density of water is greater than that of oil because of different hydrated oils. After standing for a period of time, the oil and water in the desalting tank will be separated. But this is only a preliminary oil-water separation, and there is still a small amount of water in the oil, accounting for about 0.3%. There are many ways to remove this water, such as water injection to make water droplets bigger, or external electric field method, which uses the nature of water as electrolyte. After this step, the composition of water in oil only accounts for about 0.03%. Because of the salt,
After the water in the oil is removed, it can be further refined. In the next refining, the hydrogen component in crude oil is separated by distillation. Distillation methods can be divided into atmospheric distillation and vacuum distillation. The principle is the same. Because the oil contains sulfur, the equipment used in the refinery must have certain anti-corrosion ability. Distilled components can generally be divided into gasoline, diesel oil, wax oil and asphalt.
transformer factory
Transformer is based on the principle of electromagnetic induction. Electrical appliances that transmit electric energy or signals from one circuit to another are important components of electric energy transmission or signal transmission. Transformer is a new type of electromagnetic device. Voltage transformer can convert AC power of one voltage into AC power of another voltage with the same frequency. The main components of voltage transformer are an iron core and two winding transformers sheathed on the iron core.
The basic principle of transformer is electromagnetic induction principle. Now take a single-phase double-winding transformer as an example to explain its basic working principle (as shown in the above figure): when voltage 1 is applied to the primary winding, current 1 flows and alternating magnetic flux 1 is generated in the iron core. These fluxes are called main magnetic fluxes, and under their action, the potential 1 2 is induced by the windings on both sides respectively.
F frequency
N- turns
M- main magnetic flux value
Because the number of turns of the secondary winding is different from that of the primary winding, the induced potentials E 1 and E2 are different, and the voltages E 1 and E2 are also different when the internal resistance and voltage drop are omitted.
When the secondary side of the transformer is unloaded, only the current (0) of the main flux flows through the primary side, which is called excitation current. When the secondary side is loaded with load current 2, it also generates magnetic flux in the iron core, trying to change the main magnetic flux. However, when the primary side voltage is unchanged, the main magnetic flux remains unchanged, and the primary side will flow through two parts of current, one is excitation current 0, and the other is used to balance 2, so this part of current follows 2.
The above balancing function is essentially a magnetic potential balancing function, and the transformer realizes the energy transfer on the primary side and the secondary side through the magnetic potential balancing function.
Electric machinery repair shop
Rotating principle of single-phase and three-phase asynchronous motors
The premise of three-phase asynchronous motor rotation is to have a rotating magnetic field, which is generated by the stator winding of three-phase asynchronous motor. We know that the interphase voltage of the phase power supply is 120 degrees in phase, and the three windings in the stator of the three-phase asynchronous motor are also 120 degrees in spatial orientation, so that when the three-phase power supply is connected to the stator winding, the stator winding will generate a rotating magnetic field, and the generation process is shown in figure 1. The generation process of rotating magnetic field is described by four moments. Every time the current changes, the rotating magnetic field rotates once in space, that is, the rotating speed of the rotating magnetic field is synchronized with the current change. The rotating speed of the rotating magnetic field is n=60f/P, where f is the power frequency and p is the magnetic pole logarithm of the magnetic field. The unit of n is: revolutions per minute. According to this formula, we know that the rotation speed of the motor is related to the number of magnetic poles and the frequency of using power supply. So there are two ways to control the speed of AC motor: 1, changing the magnetic pole method; 2. Frequency conversion method. The first method was often used before, but now the stepless speed regulation of AC motor is realized by frequency conversion technology.
Looking at figure 1, we can also find that the rotating direction of the rotating magnetic field is related to the phase sequence of the current in the winding. The phase sequences A, B and C are arranged clockwise, and the magnetic field rotates clockwise. If any two of the three power lines are connected reversely, for example, phase B current is fed into phase C winding and phase C current is fed into phase B winding, and the phase sequence becomes C, B and A, then the magnetic field will inevitably rotate counterclockwise. Using this characteristic, we can easily change the rotation direction of three-phase motor. After the rotating magnetic field is generated by the stator winding, the rotor bar (squirrel cage bar) will cut the magnetic lines of the rotating magnetic field to generate induced current, and the current in the rotor bar will interact with the rotating magnetic field to generate electromagnetic force, and the electromagnetic torque generated by the electromagnetic force will drive the rotor to rotate at the speed of n 1 in the direction of the rotating magnetic field. In general, the actual rotation speed of the motor n 1 is lower than that of the rotating magnetic field n. Since it is assumed that n=n 1, there will be no relative movement between the rotor bar and the rotating magnetic field, so the magnetic field lines will not be cut and electromagnetic torque will not be generated, so the rotation speed of the rotor n 1 must be lower than that of n. Therefore, we call the three-phase motor an asynchronous motor.
practical experience
This internship lasted for a week, neither too long nor too short. Although my knowledge in related fields is still lacking, I am still very insightful. The repentance of the masters in the internship gave us a basic understanding of the future work and laid a solid foundation for the future work. To this end, I want to say to our host: "Thank you! We will definitely thank you for every word in the future and will work harder in the future. "
The internship is over, and it's time for me to start a new life. In my small college life, I still need to do a lot of things, such as continuing to learn English, continuing to study professional courses and continuing to pay attention to the industry. Whether I am a professional manager or start my own business in the future, the accumulation during college will definitely be the wealth of my life! The above is the arrangement and feelings of this internship, which makes us clear the professional direction and lays the foundation for future study.