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P ri n c e Mo ha m m ad Bi n F ah d Un i v er si t y College of Engineering Department of Mechanical Engineering Internship Report at [Sabic-Sharq] Reporting Period: [14/7/2012 - 25/7/1012] Submitted b: [Khalid AL-Hussain] [200700263] [submission date (27/7/2012)] Mechanical Engineering Department Summer 2012 Summary: I was assigned these two weeks to study about transformers and VVF. My supervisor noticed that it's hard to cover the requirements in two month. Therefore, it seems that I will have a beneficial pressure, so he asked me to do other things. My assignments in these two weeks are about transformers and Basics trainings. Back ground: According to my plan, I have to learn more about transformers in the fifth week, but my supervisor asked me to seek for other details because of the short period. The week after, I was assigned to see the basic trainings in the company. Though it's hard to cover the majority of heavy, I was motivated to try to learn as much as I can from them. Moreover, I am joining a small group in the basic training. Progress: My assignment in these two weeks: Plan work Transformers, Generators, GIS Basic Training Period 14/7/2012-18/7/2012 21/7/2012-25/7/2012 Week 5: Transformers: The main purpose of transformers is either steeping down or stepping up. This depends on the on what is needed for the load. Usually, transformers feed substations, three phase motors, transmission lines, etc. there are two types of transformers. The first type is the dry type transformer. The second type transformer is liquid filled type. Dry type of transformer: The dry type of transformer has limited size around 10 MVA because it relies on air to provide cooling and its losses are high. Further, It can be designed to operate at much higher temperature than Liquid-filled (temperature rises as high as 150oC, whereas oil filled as 100oC to avoid acceleration of breakdown of oil). Liquid filled type: This type of transformer is relying on oil. There is sealed type and non- sealed type. Sealed type: The sealed type has a temperature gauge. When the temperature is increasing, the size of the oil will be increased and thus the air will go out with the moisture. The nitrogen gas and oil and oil will be inside the tank and that's why we call t sealed. On the other hand, the non-sealed is not closed as the sealed one and it has there is a breather. Brief description about oil filled type equipments: The breather of the transformer absorbs the moisture by silica jell. The radiator of the sealed type is for cooling the oil. The bushings are above the terminal box to hold the cables, and insulate between the cables and the box to avoid short circuit. Tap changer which is located in the primary windings to switch and control the voltages. There are two types of tap changers. ON load tap changer and off load tap changer. Gas insulated switch gear: It is the upstream of the substations. A gas (SF6) insulated substation may have underground feed lines and be nearly invisible to the average person. Distribution circuits supplied by gas insulated substations normally have an alternate feed from another substation, to allow maintenance work on the gas insulated site. For instance, Sceco is feeding Sharq Company and the GIS will feed transformer to feed substations. (See figure 1) Generators: The generator has an exciter which is series to the load will produce a magnetic field to the stator windings. Then, the induced voltage in the stator winding that ends currents will be delivered to the load. There is a prime mover will produce steam for the turbine to rotate and ultimately the generator will rotate. Therefore, the generator converts the mechanical energy into electrical energy. There are other sources of generations such as hydro-electric, nuclear, fossil fuels, and diesel engine. (See figure2) Week 6: There is a basic training that I have to attend in order to enhance my knowledge about my major. It was interesting training that I've ever seen in my university life. Furthermore, the instructor was expert to teach this course. Fluorescent lights: There are two types of fluorescent lights. The first is t is preheat type, when the circuit is energized the current will flow from cathode A and then to cathode b through the starter and there will heat the gas inside the lamp and thus an arc will occur across the fluorescent lamp. The second is the rapid. The rapid start ballast will deliver a small voltage to heat the cathodes. There isn't starter needed and cathodes will heat the gas, so the gas will be increased and higher current and lower resistance. Mercury Vapor and Sodium: The ballast will deliver a voltage to the electrodes. The starter resistor will control the current flowing. An arc will be struck between the starting electrode and the two main electrodes. Therefore, the current will be high and resistance and that makes the mercury vapor increased. Ultimately, the lamp is working. Sodium vapor doesn't have the starting resistor and electrodes, but only two main electrodes. However, there is an igniter that will deliver high voltage and high frequency to the electrodes and heat the sodium vapor and arc will occur to make the lamp work. Single Phase Motor: The supply voltage will deliver current which will go into two loads. The first load has Capacitor, Centrifugal switch and starting winding. The second load has running winding. The current will flow through the capacitor and centrifugal switch and then starting winding. The starting winding will produce a magnetic field to make the rotor rotate. When the rotor reaches the required speed, the centrifugal switch will open. The running winding will make the rotor to continue rotating. The purpose of having the capacitor in the circuit is maintain the wattage, voltage , and also to make phase shift between the running period and starting period is 90. Plan: I was supposed to learn about transformers and VVF this week. But the supervisor asked me to do more as a result of the short period. The supervisor is a good person who is helping for my future. Conclusion: In conclusion, the generator will generate power to the GIS, and the GIS will feed the transformers that will step down voltages for the substations. The Basic training course was helpful for me to enhace and improves my knowledge. The engineer must seek for the information by himself to learn. Appendices: GIS in ABB: Figure 1 Generators performance: Figure 2