Power transformers are the unsung heroes of the electrical grid, silently facilitating the transmission and distribution of electricity across vast distances. In this blog post, we will delve into the world of power transformers, exploring their introduction, intricate workings, and the crucial accessories that ensure their optimal performance.
Transformer is a static device which transforms AC electrical power from one voltage to another voltage keeping the frequency same by electromagnetic induction principle.
Input to a transformer and output from a transformer both are alternating quantities (AC).Electrical energy is generated and transmitted at an extremely high voltages. The voltage is to be then reduced to a lower value for its domestic and industrial use. When the transformer changes the voltage level, it changes the current level also.
Working Principle
The primary winding is connected to the single – phase ac supply, an ac current starts flowing through it. The ac primary current produces an alternating flux (Ф) in the core. Most of this changing flux gets linked with the secondary winding through the core.
The varying flux will induce voltage into the secondary winding according to the faraday’s laws of electromagnetic induction. Voltage level change but frequency i.e. time period remains same. There is no electrical contact between the two winding, an electrical energy gets transferred from primary to the secondary.
A simple transformer consists of two electrical conductors called the primary winding and the secondary winding. Energy is coupled between the windings by the time varying magnetic flux that passes through( links) both primary and secondary windings.
Essential Accessories of Power Transformer
1.Buchholz relay
This relay is designed to detect transformer internal fault in the initial stage to avoid major breakdown. The upper float rotates & switches contacts close & thus giving alarm.
2.Oil Surge Relay
This relay can be checked by pressing test switch provided on top side. Here only one contact is provided which gives trip signal on operation of float. By shorting contact externally by link, trip circuit can also be checked.
- Explosion Vent
It consists of a bent pipe with Bakelite diaphragm at both ends. A protective wire mesh is fitted on the opening of transformer to prevent the pieces of ruptured diaphragm from entering the tank.
- Pressure Relief Valve
When the pressure in the tank rises above pre- determined safe limit, this valve operates & performs the following functions: –
- Allows the pressure to drop by instantaneously opening the port.
- Gives visual indication of valve operation by raising a flag.
- Operates a micro switch, which gives trip command to breaker.
- Oil Temperature Indicator
It is dial type thermometer, works on the vapour pressure principle. It is also known as magnetic oil gauge (MOG). It has a pair of magnet. The metallic wall of conservator tank separates magnets without any through hole.Magnetic field comes out and it is used for indication.
- Winding Temperature Indicator
It is also similar to OTI but has some changes. It consists of a probe fitted with 2 capillaries. Capillaries are connected with two separate bellows(operating/compensating). These bellows are connected with temperature indicator.
- Conservator
As expansion and contraction occurs in transformer main tank, consequently the same phenomena takes place in conservator as it is connected to main tank through a pipe.
- Breather
This is a special air filter incorporating a dehydrating material, called, Silica Gel. It is used to prevent the ingress of moisture and contaminated air into conservator.
- Radiators
Small Transformers are provided with welded cooling tubes or pressed sheet steel radiators. But large transformers are provided with detachable radiators plus valves. For additional cooling, exhaust fans are provided on radiators.
- Tap Changer
As load on the transformer increases, secondary terminal voltage decreases.There are two type of tap changer.
A.Off Load Tap Changer
In this type, before moving the selector, transformer is made OFF from both ends. Such tap changers have fixed brass contacts, where taps are terminated. The moving contacts are made of brass in the shape of either roller or segment.
B.On Load Tap Changer
In short we call it as OLTC. In this, taps can be changed manually by mechanical or electrical operation without making off the transformer. For mechanical operation, interlocks are provided for non-operation of O.L.T.C. below lowest tap position and above highest tap position.
11.RTCC (Remote tap change control cubicle)
It is used for tap changing by manually or automatically through Automatic Voltage Relay (AVR) which is set +/- 5% of 110 Volt (Reference taken from secondary side PT voltage).
Power Transformer: An introduction, Working and Essential Accessories-Video Tutorial
Future technology of Transformer
The future of transformer technology is marked by advancements in smart grids, digitalization, and enhanced energy efficiency. These transformations aim to make power distribution more reliable, sustainable, and responsive to the growing demands of modern society.
Digitalization will enable the development of smart transformers, incorporating sensors and communication technologies for real-time monitoring, predictive maintenance, and efficient management of power distribution networks.
AI will contribute to predictive analytics and decision-making processes in transformer maintenance. Smart transformers will leverage AI algorithms to analyze data, detect potential issues, and optimize performance.
Future transformers are expected to play a crucial role in integrating renewable energy sources into the grid. They will facilitate the efficient transmission and distribution of power generated from renewable sources, ensuring a smooth transition to a more sustainable energy landscape.
Frequently Ask Question(FAQ)
1.What is transformer?
A power transformer is a static device that transfers electrical energy between two or more circuits through electromagnetic induction. It plays a crucial role in stepping up or stepping down voltage for efficient electricity transmission and distribution.
2.Which standard applicable for transformer?
IS 1180 : 2014- For Distribution Transformer (used for auxiliary purpose i.e. output voltage of 433V)
IS 2026 : 2011- For rest of the special purpose Transformer types (Windmill, Solar, Furnace etc.)
3.Can transfromer work on DC?
The direction of current flow is changed in AC. When AC flows through the primary, current is induced in the secondary due to mutual induction. There is no mutual induction in DC as its direction does not change. So a transformer cannot work in DC.
4.What is the purpose of cooling systems in power transformers?
Cooling systems, such as radiators or fans, prevent overheating during the transformer’s operation. Efficient cooling is essential for maintaining the transformer’s operational integrity and preventing damage to its components.
5.Waht is the role of Oil in transformer?
Transformer oil, or insulating oil, enhances insulation and serves as a cooling medium. It prevents electrical breakdown and dissipates heat generated during the transformer’s operation.
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