1. A SEMINAR ON Different Types Of Transformers Used For 210MW Unit Thermal Power Plant PRESENTED BY : VAIBHAV BHOPE PRITAM BIJWAL SUMIT VINCHURKAR SANTOSH VIJEKAR NIKHIL WANDHARE NIKHIL SHRIWAS AKASH SHEGOKAR CHETAN ANGARWAR VIKASH SINGH AKSHAY SAHARE

2. Overview Introduction Single line diagram Classification of transformer Parts of transformer Cooling system Protection of Transformer 3. TRANSFORMER Transformer is a static device which transform electric power of one circuit to another circuit without changing its frequency. Working Principle of transformer : The working principle of transformer depends upon Faradays law of electromagnetic induction. Actually mutual induction between two or more winding is responsible for transformation action in an electrical transformer. Faradays laws of Electromagnetic Induction: According to Faradays law, Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil". 4. Single line diagram 5. Types of Transformers used in 210MW unit 1) Generator Transformer 2) Station Transformer 3) Distribution Transformer 4) Unit auxiliary Transformer 5) Instrument Transformer 6) Rectifier Transformer 7) Neutral ground Transformer 8)Transformer used for general purposes and for different processes. i ) Welding Transformer ii ) Specially designed Transformer used for X ray, Radio, Telecommunication, T.V., High frequency heating, and Industrial heating for different processes. 6. Generator Transformer Rating MVA = 240 MVA Primary Side = 15.75 KV (d) Secondary Side = 400 KV (Y) Oil Qty = 43 KL Cooling = OFWF Vector Group = Yd11 %Z = 11.90 7. Functions This is step up transformer of high voltage capacity. This is connected after the generator to step up voltage from 15.75kv to 400kv. The main function of this transformer is to step up voltage so as to reduce transmission losses, line drop and increases Transmission efficiency . 8. Station Transformer Rating MVA = 40 MVA Primary Side = 220 KV (Y) Secondary Side = 6.6 KV (Y) Oil Qty = 30 KL Cooling = ONAF Vector Group = Yy0 %Z = 11 9. Functions Transformer at the generating station is required for starting of the generating units when they are either newly constructed or taken of the bar for overhaul. These Power transformers are called station transformer, which receives power from the grid and feed power-to-power station distribution system. 10. Unit Auxiliary Transformer Rating MVA = 20 MVA Primary Side = 15.75KV (d) Secondary Side = 6.6 KV (Y) Oil Qty = 6.4 KL Cooling = ONAF Vector Group = Dy1 %Z = 9.0 11. Functions The Purpose of Unit auxiliary Transformer is to feed power to generator auxiliaries of that unit These transformers are connected to generators and are used as stepping down transformers. The HV side transformer voltage corresponds to the voltage of the generating unit and the LV side voltage is stepped down to 6.6KV Rated KVA of Unit Auxiliary Transformers is approximately 15% of the generating rating Usually these transformers are outdoor transformers One Unit auxiliary transformer is present for every generating unit. 12. A Rectiformer is a rectifier and transformer designed and built as a single entity for converting alternating current into direct current. It is piece of power systems equipment rather than an electronics component. Rectiformers are used for supplying power to different field of ESP (electrostatic precipitator). 13. For metering and protection to maintain instrument accuracy. For sensing H.T. side current at the secondary side Used in protection relay, trip coils and pilot wires. Used in current power measurement, temperature sensing etc. Current Transformer (CT) Potential Transformer (PT) 14. Distribution transformer This is step down transformer connected according to applications such as boiler ,turbine , station service board. The main function of this transformer is to provide convenient amount of power in the various boards. 15. NGT The subject of grounding covers the problems relating to the conduction of electric current to the earth and through the ground. The earth rarely serves as a part of the return circuit, being used mainly for fixing the potential of circuit neutrals. The ground connection improves service continuity and protects lives and equipment. 16. (a) Arcing rounds are reduced or eliminated. (b) The neutral grounding stabilises the neutral point. (c) By employing resistance or reactance in earth connection, the earth fault current can be controlled. (d) The over voltage surge due to lightening are discharged to earth hence less damages to the equipment. Useful amount of earth fault current is required to operate earth fault relay. (e) Improved service reliability due to limitation of arcing ground and prevention of unnecessary tripping of circuit breakers. (f) Life of eqipment, machines and installation is improved due to limitation of voltages. (g) Greater safety to personnel and equipment due to operation of fuses or relay on earth fault and limitation of voltages. Hence it is economical to ground neutral point. Advantages of Neutral Grounding Transformer 17. Constructional Features Main Tank Laminated core Core winding Bushing Tap changer Conservator Breather Explosion vent / Pressure relief valve 18. Cooling system is required for transformer to take away the heat generated in transformer due to losses and maintaining insulation healthy. Cooling system of transformer is provided by considering design and KVA rating of a transformer. Cooling system of transformer is as follows. i. Air natural cooling system. ii. Oil natural cooling system with or without radiator. iii. Cooling of transformer improved by force airflow by blowers/Air blast by fans iv. Oil forced natural cooling system (OFN): - circulation of oil by pump to radiator, which has natural cooling. v. OFB : Forced oil circulation of oil by pump to radiator, which has force, cooled by air blower. vi. OFW : Forced circulation of Oil through oil cooler and water-cooling is by water. Generally Oil temp is maintained in between 45 to 55 Dc. & Winding temp in between 55to 80 c.(depends upon insulation class) 19. Types of Cooling ONAN ONAF 20. OFAF OFWF 21. Maintenance Transformer Oil Level Checking Breather condition monitoring Oil testing D. G. A. Oil Filtration Bushing Cleaning Drying Out (after 7 Yrs)