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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