I hereby certify that this intern "Manufacturing Process of 500 KVA, 3 Phase Distribution Transformer at Basic Power Engineering Ltd" has been done by the current student under my direct supervision and that they have done this work themselves in the laboratories. Sanuarul Haque Id no been accepted as satisfactory in partial fulfillment of the requirement for Bachelor of Electrical and Electronics Engineering on 27 June 2021. All praise is to the Supreme Being; the creator and ruler of the universe Allah Almighty whose mercy keeps us alive and to pursue my education in Bachelor of Electrical and Electronic Engineering and complete the Internee Report titled as.
In the process of carrying out this internship report, I would like to express my gratitude and respect to some generous persons for their immense help and cooperation. The report includes the step by step manufacturing process of core cutting, HT, LT winding, core and coil assembly, filling, bushing, oil filling etc. I have tried to describe the entire calculation process of 500kVA 3 phase distribution transformer with its test procedure along with test reports which were observed by me.
In this report, I have given a very brief overview of what I saw and learned during my internship. This report will give the reader knowledge about Basic Power Engineering Limited and Distribution Transformer.
Background
Objective
Broad of Objective
Specific objectives
Scope of the Study
Data Collection
Primary Data
Secondary Data
Limitations of the Study
Every organization has its own secrecy that is not revealed to anyone outside the organization. While collecting data at Basic Power Engineering Limited, staff did not disclose enough information due to the confidentiality rule of the organization.
- Company Name
- Company Overview
- Major Works Involved
- Supply Chain
- Vision
- Mission
- Quality and Environmental Policy
- Scope
- Achievements and Awards
- Departments of Basic Power Engineering Limited
Basic Power Engineering Limited contributes to the country by saving foreign exchange by producing various energy products. Basic Power Engineering Limited, a future company, has been running its operations since January 2007 under the prominent successful leadership of the company directors [3] to meet the domestic electricity needs of almost every new organization in the country. Basic Power Engineering Limited is now the largest transformer and switchgear manufacturing company in Bangladesh.
The company has a wide range of distribution transformers, HT high voltage switchgear, LT low voltage switchgear, PFI power factor improvement panels, DB distribution panels, etc. The company attaches utmost importance to customer satisfaction in all aspects and now enjoys worldwide recognition by adopting an internationally recognized quality system. Basic Power Engineering Limited, we believe that establishing an effective quality and environmental management system will help our company achieve its vision of becoming a highly respected manufacturer and producer of various indoor and outdoor electrification products/items.
The company is strongly committed to leading in this industry by providing satisfaction to our customers and complying with all applicable environmental laws and other requirements that we endorse [2]. Since its inception in 2007, Basic power Engineering Limited has achieved distinction as the Leading Power Engineering Company in Bangladesh through its dedication and service.
- Basic Function of Transformer
- Uses of Transformer
- Other uses and application of Transformer
- Efficiency of a Transformer
- Classifications of Transformer
- Mainly two types of construction are in common use for the
- Technical Specification of 400kVA, 3-∅ Distribution Transformer
- Major Components of a Transformer
- Core
- Copper wire for HT and LT side
- Insulation Paper
- Bushings
- Tap Changer
- Channel
- Pressboard/Supporter
- Transformer Tank
- Radiator
- Transformer Oil
- Oil Level Indicator
- Conservator Tank
- Breathers
- Horn Gap
If only a fraction of the flux produced by one coil couples the other, the coils are said to be loosely coupled. Because of the high permeability of the core, most of the flux switches to the other coil and induces a time-varying emf (voltage) in that coil. The frequency of the induced emf in the other coil is the same as that of the current in the first coil.
Taking the ratio of the two equations (1) and (2) for Vs and Vp gives the basic equation for increasing or decreasing the voltage. Now, by appropriate choice of the ratio of turns, a transformer therefore makes it possible to "step up" an alternating current voltage by making Ns greater than Np, or "step down" by making Ns less than Np. It can increase or decrease the level of the level of voltage or current (when voltage increases, current decreases and vice versa because P=VI, and power is the same) in AC circuit.
The amount or intensity of power loss in a transformer determines the efficiency of the transformer. Therefore, the ratio of the output power of the secondary winding to the input power of the primary winding can be stated as the Efficiency of the transformer. In a core-type transformer, each winding can be equally spaced and wound on both legs of the rectangular core.
In a shell transformer, the two windings are usually wound over the same leg of the magnetic core [5]. In oil type transformer, terminal means to bring the electrical connection from inside to outside the tank. The bushings are the things that the electrical wires connect to on top of the transformer.
The switch replaces the number of turns in one winding and there by changing the proportion of turns of the transformer. The bearing surface of the tank, on which the bushings are clamped, must be fairly flat. The oil level indicator continuously shows the fluid level in the primary reservoir of the transformer, Radiator Path.
The level of oil in the transformer can rise and fall due to temperature. Horns are normally paired on either side of the insulator, one connected to the high voltage section and the other to ground.
Basic Calculation of a Transformer
Core Calculation
Transformer Manufacturing Process
- Core Cutting
- Core Assembling
- Coil Windings
- Core Coil Assembling
- Tap changer
- Heat Chamber
After calculating the measurement of the core, we cut the core using another machine to get our desired shape. The core cut at an angle of 900 in rectangular shape and 450 for MITRED shape also cuts "V". After arranging the core, we tighten the core with 4 channels and tie the rods and screw them shown in fig.
After the core is tightened, the upper two channels and core C are open to place the two coils (LT and HT) in the core. Before installing the core, there is a 6 mm insulating paper wrapped in two parts (3 mm + 3 mm) above the cotton tape; which is used to insulate between the core and the coil and gives the bottom separator inside the three cores which are separated between the coil and the channel shown in figure 7. There are two windings on the transformer core which are shielded from each other.
The windings are thus designed to ensure reduced axial stresses under short-circuit conditions and also to withstand impulses and surges. For Power Transformers, both low-voltage and high-voltage windings are of the disc type, which provides the highest resistance to short-circuit forces. The sudden loading and withdrawal of load creates a tensile stress on the winding in the form of buckling forces or bursting forces.
The construction of the CCA (Core Coil Assembly) by providing adequate radial and axial supports prevents the tension from causing damage to the windings. The head of the leg is cotton tight and then again pressure plate is placed on top of the coil for insulation between the coil and the upper channel. After placing the press plate, place the C core into the core legs to complete the core design.
It controls the output voltage by changing the number of turns and thereby changing the turns ratio of the transformer. Then the transformer is ready for the next step: attaching bushing materials and moving to the heating chamber. If the inside of the transformer is not dry enough, a decrease in dielectric strength occurs due to heat and power losses.
Testing Process of Transformer
- Oil Test
- Measurement of Voltage Ratio
- Resistances Test
- Measurement of No-Load Loss
- Measurement of Full Load Loss
- Megger Test
- High Voltage Test
At the time of oil testing, we take the oil in a pot and put it in the oil testing machine. Then we connect the three-phase wire to the transformer and match the measured ratio with the calculated ratio. Notes: The voltage ratio between the HT and LT sides of the transformer for each tap position is fine. The polarity of the transformer is subtractive.
For resistance test, we first need to run the meter to measure the resistance on the HT side. Then we just hold the probe from the clamp on the meter to the HT cable like - AB, BC, CA and find the result for this side. To test the no-load first, we connect the three-phase power supply to the LT terminals and we need a wattmeter and a current clamp. When we first perform the megger test of a transformer, we hold the probe of the HV side with ground, then the LV side with ground, and then the HV side with LV side for 30 seconds.
To carry out the high voltage test on the high voltage winding, we need to short connect the three phase terminal on the HV side, the LV side and the case/tank to the main earth. At first we put 28kV from the high voltage test rig and then there was a barrier. If the transformer remains stable after maintaining this voltage for 1 minute, it proves that the transformer is safe from voltage surges that may be caused by lightning or other surges.
Recommendation
They do not have enough technicians and manpower, as a result they cannot deliver large quantities of products at a time.
Conclusion
