A RESEARCH PROJECT
BY
NNAEMEKA ORIOHA
EE/2017/167
SUBMITTED TO
DEPARTMENT OF ELECTRICAL ELECTRONIC ENGINEERING FACULTY OF ENGINEERING CARITAS UNIVERSITY, AMORJI-NIKE, ENUGU.
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF BACHELOR OF ENGINEERING (B.ENG)
AUGUST 2017
APPROVAL PAGE
This project has been read and approved by the undersigned as with the requirement at the department of Electrical Electronic Engineering of Caritas University Amorji Nike Enugu for the award of Bachelor of Engineering (B.Eng.) in Electrical Electronic Engineering.
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Engr. Ejimorfor Date
(Project supervisor)
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Engr. Ejimofor Date
(Head of Department)
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External Supervisor
DECLARATION
I declare that this project material is an original work done by me under the supervision of Engr. Ejimorfor, department of electrical electronic engineering faculty of engineering caritas university, amorji-nike, enugu
DEDICATION
This project is dedicated to Almighty God and to my parents Engr. & Mrs. Chukwu A. Orioha and to my beloved brothers and sisters whose ever loving kindness and support has seen me through my years of studies.
ACKNOWLEDGEMENT
I wish to express my immense gratitude to God Almighty for his mercy, guidance and protection towards me for seeing me through the rigors of this work. I am greatly indebted to my supervisor Engr. Ejimofor for his kind gesture and whose critics lead to the achievement of this work. I also will remain grateful to the tremendous contribution of my lecturers Engr. Ojobor (the Dean of Engineering Faculty), Engr. Ejimofor (Head of Electrical Electronic Engineering Department), Engr. Mbah, Engr. Ochi, and all the staff of Electrical Electronic Engineering both academic and non academic staff for their intellectual upbringing. My special appreciation goes to my loving parents Engr. & Mrs. Chukwu A. Orioha, my grandparent, my uncles and aunties, my brothers and sisters whose moral and financial support cannot be over emphasized. Also my sincere gratitude and special regards to my friends too many to mention whose encouragement also lead to the success of this work.
This paper to develop an automatic tripping mechanism for the three phase supply system. The project output resets automatically after a brief interruption in the event temporary fault while it remains in tripped condition in case of permanent fault. The electrical substation which supply the power to the consumers, have failures due to some faults which can be temporary or permanent. These faults lead to substantial damage to the power system equipment. In India it is common, the faults might be LG (Line to Ground), LL (Line to Line), 3L (Three lines) in the supply systems and these faults in three phase supply system can affect the power system. To overcome this problem a system is built, which can sense these faults and automatically disconnects the supply to avoid large scale damage to the control gears in the grid sub-stations. This system is built using three single phase transformers which are wired in star input and star output, and 3 transformers are connected in delta connections, having input 220 volt and output at 12 volt. This concept low voltage testing of fault conditions is followed as it is not advisable to create on mains line. 555 timers are used for handling short duration and long duration fault conditions. A set of switches are used to create the LL, LG and 3L fault in low voltage side, for activating the tripping mechanism. Short duration fault returns the supply to the load immediately called as temporary trip while long duration shall result in permanent trip.
CHAPTER I
INTRODUCTION
1.1 1.1 Background
In this chapter, it explains briefly on the background and system overview of
this project. Also in this chapter it explains the objectives of the project, the scope of
study and the thesis outline.
1.2 System Overview
An electromagnetic or induction instrument used to indicate the phase sequence in three-phase electric circuits. The phase sequence determines the direction of rotation of three-phase electric motors; the correct operation of some measuring instruments and automatic control devices also depends on the phase sequence. Phase-sequence indicators are usually constructed as miniature asynchronous electric motors in which an aluminum disk serves as the rotor. The disk rotates when acted upon by a magnetic field excited by currents in three windings when the windings are connected to the conductors of the circuit being tested. A certain order of phase sequence is marked on the terminals of the phase-sequence indicator. If the disk rotates in the direction of an arrow marked on the disk, the phase sequence corresponds to the marks on the terminals of the instrument. General-purpose phase-sequence indicators can be used to determine the power factor and the phase shift between voltage and current.
In indicator there is a led light source. It gives us the presence of the current source by indicate its light. If the phase of the indicator is not equal to the supply voltage then it can not give us the presence of current source by its led light off. If the phase of indicator is equal with the mane supply phase then its remaining bright and continuous gives us the indication of current source.
Phase sequence' is the order, or sequence, in which each of the line voltages of a three-phase system reach their peak values. If 'normal' phase sequence is considered to be A-B-C (or R-S-T, etc.), then 'reverse phase sequence' would be A-C-B.
Phase sequence detection and controlled power supply system provide mainly used to detect the phase sequence of any machine or any other electrical equipment which works on three phase supply.
In this system the extra feature we introduced is controlling of supply voltage. We can also say that the over voltage and under voltage protection is also introduced in this system.
As we know that in three phase supply there is three phase r y b. It is mandatory that these three phase are in correct order, because if it is not in correct manner than there is damage in windings of machines.
Machine whose phase sequence is to be detect is connected to the input of our system, now if the phase sequence is correct the array of green led’s ring are glowing in clock wise direction. When the sequence is wrong than the array of red led’s ring is glowing in anti clock wise direction.
If the voltage of input is less than the required one, means that when under voltage condition comes on that time the system is amplify the input voltage and comes it to the normal voltage range. Than the phase sequence detection is starts.
If the input voltage is much over than the required range, means that when over voltage condition come on that time system trip the ckt. Means that cut out the supply by the use of relay, and we protect our equipments. So our main aim is to provide a simpler and efficient system which gives a better phase sequence detection, in comparison of conventional lamp method and synchronoscope method.The best use of this system in sub-station, where after maintenance of m/c it is very difficult to connect the right phase r y b. So at that place we easily used this system.
Phase sequence is very important if, for example, you want to ensure that your three-phase motors rotate in the correct direction. So, after disconnecting them for maintenance, you can confirm the phase sequence of your incoming conductors by using a phase-sequence meter, before you reconnect that motor.
In a three-phase ac system, a power source with three wires delivers ac potentials of equal frequency and amplitudes with respect to a zero-potential wire, each shifted in phase by 120° from one wire to the next. Two possibilities exist for establishing a phase sequence. In the first, voltage on the second wire shifts by 120° relative to the first, and, in the second, a –120° shift occurs with respect to the first wire. Phase order determines the direction of rotation of three-phase ac motors and affects other equipment that requires the correct phase sequence: a positive 120° shift. You can use a few low-cost passive components to build a phase-sequence indicator.
1.3 Objectives
The objective of this project is to indicate the order of succession in time off the different voltage peaks of a multiphase supply. In addition the knopp sequence indicaor enables one to make continuity tests. It is valuable instrument in diverse fields involving polyphase power apparatus, being employed by line and installations crews for public utility systems and industrial plant electrical departments. It is, furthermore, helpful in the testing department of public utility systems for laboratory and field testing.
Various studies have shown that anywhere from 70%, to as high as 90%, of faults on most overhead lines are transient. A transient fault, such as an insulator flashover, is a fault which is cleared by the immediate tripping of one or more circuit breakers to isolate the fault, and which does not recur when the line is re-energized. Faults tend to be less transient (near the 80% range) at lower, distribution voltages and more transient (near the90% range) at higher, sub transmission and transmission voltages. Lightning is the most common cause of transient faults, partially resulting from insulator flashover from the high transient voltages induced by the lightning.
Other possible causes are swinging wires and temporary contact with foreign objects. Thus, transient faults can be cleared by momentarily de-energizing the line, in order to allow the fault to clear.Autoreclosing can then restore service to the line.
The remaining 10 - 30% of faults are semi-permanent or permanent in nature. A small branch falling onto the line can cause a semi-permanent fault. In this case, however, an immediate de-energizing of the line and subsequent auto reclosing does not clear the fault. Instead, a coordinated time-delayed trip would allow the branch to be burned away without damage to the system. Semi-permanent faults of this type are likely to be most prevalent in highly wooded areas and can be substantially controlled by aggressive line clearance programs. Permanent faults are those that will not clear upon tripping and reclosing.
An example of a permanent fault on an overhead line is a broken wire causing a phase to open, or a broken pole causing the phases to short together. Faults on underground cables should be considered permanent. Cable faults should be cleared without auto reclosing and the damaged cable repaired before service is restored. There may be exceptions to this, as in the case of circuits composed of both underground cables and overhead lines.
Although auto reclosing success rates vary from one company to another, it is clear that the majority of faults can be successfully cleared by the proper use of tripping and auto reclosing. This de-energizes the line long enough for the fault source to pass and the fault arc to de-energize, then automatically recloses the line to restore service. Thus, autoreclosing can significantly reduce the outage time due to faults and provide a higher level of service continuity to the customer. Furthermore, successful high-speed reclosing auto reclosing. on transmission circuits can be a major factor when attempting to maintain system stability. For those faults that are permanent, auto reclosing will reclose the circuit into a fault that has not been cleared, which may have adverse affects on system stability (particularly at transmission levels).
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