Discussion on Transformer Working Principle.pptx

All About Transformer

1. DISCUSSION ON TRANSFORMER NAME PLATE DATA Engr. Shirajul Islam BSc.(EEE), MSc. (ETE, CUET) [email protected] 01845324741

2. PARTS OF TRANSFORMER MAIN TANK RADIATORS CONSERVATOR EXPLOSION VENT LIFTING LUGS AIR RELEASE PLUG OIL LEVEL INDICATOR TAP CHANGER WHEELS HV/LV BUSHINGS FILTER VALVES OIL FILLING PLUG DRAIN PLUG CABLE BOX

3. LV Bushing

4. HV Bushing

5. Radiator

6. Conse r v ator

7. V al v e

8. EXPLOSION VENT

9. Tap Changer

10. AIR RELEASE PLUG

11. LV Bushing Box

12. Buch h olz Relay

13. Name Plate of 33/11 kV Transformer

14. 132/33 kV Transformer Name Plate Data

15. Information in Name Plate Transformer Capacity Voltage Ratio (including Tap position) Rated Current Rated Frequency No. of Phase Type of Cooling % Impedance Temperature Rise Insulation Level Vector Group

16. Weight Information No Load Loss Full Load Loss Current Transformer information Tap Changer Information Standard applied Year of Manufacturing Makers Serial Number Information in Name Plate (Cont…)

17. Transformer Capacity For Distribution Transformer 100 kVA, 200 kVA, 500 kVA, etc. For Power Transformer 5 MVA, 10/14 MVA, 20/28 MVA, 28/35 MVA, etc. 28/35 MVA, 35/50 MVA, 50/75 MVA, 80/120 MVA etc.

18. Voltage Ratio (including Tap position) For Distribution Transformer: (11±2×2.5%)/0.415 kV For Power Transformer (33±8×1.25%)/11 kV (132±8×1.25%)/33 kV (132 +8×1.25% - 12×1.25% )/33 kV

19. Rated Current Rated Current at each Tap Position. (i.e. Rated current at each voltage ratio) For example a 11/0.415 kV, 200 kVA Distribution Transformer Tap P os i ti o n HT Winding LT Winding Voltage (V) Current (A) Voltage (V) Current (A) 1 11,550 10.00 415 278.57 2 11,275 10.25 3 11,000 10.50 4 10,725 10.78 5 10,450 11.06

20. T y p e o f C oolin g Cooling methods T r ansf or m e r C o nsu l t i n g S e r vic e s I n c . Cooling medium A - air cooling, O - oil cooling, K, L - cooling with synthetic fluid, W - water cooling Cooling mode N - natural cooling, F - forced cooling, D - directed cooling (directed oil flow) E.g. ONAN - oil natural, air natural, (OA) ONAF - oil natural, air forced, (FA) ODAF - oil directed, air forced (FOA)

21. ONAN, OA Oil natural, air natural ONAF, FA Oil natural, air forced C) OFAF, FOA - Oil forced, air forced T y p e o f C oolin g

22. ODAF, FOA - Oil directed, air forced -The oil is pumped and directed through some or all of windings OFWF, FOW - Oil forced, water forced ODWF, FOW - Oil directed, water forced T y p e o f C oolin g

23. Rated Frequency & Phase 50 Hz or 60 Hz 1 Phase or 3 Phase

24. The percentage impedance of a transformer is the voltage drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage. For example impedance voltage at: Minimum Tap ( Tap-1, 13.49% ) Rated Tap ( Tap-9, 12.86% ) Maximum Tap ( Tap-21, 12.67% ) % Impedance or impedance voltage

25. Calculation of Percentage Impedance In order to determine equivalent impedance, one winding of the transformer is short- circuited, and just enough voltage is applied to the other winding to create full load current to flow in the short-circuited winding. % Impedance or impedance voltage

26. Calculation of Percentage Impedance Example Calculation If a 2,400/240 volt transformer has a measured impedance voltage of 72 volts on the high voltage windings, its impedance (Z), expressed as a percent, is: Z%=(Impedance Voltage/Rated Voltage)*100 percent Z = (72/2400)*100 = 3 percent

27. The Effect of Higher and Lower Percentage Impedances The percentage impedance of a transformer has a major effect on system fault levels. It determines the maximum value of current that will flow under fault conditions. It is easy to calculate the maximum current that a transformer can deliver under symmetrical fault conditions.

28. Fault Level Calculation For example, consider a 2000 kVA transformer with an impedance of 5%. The maximum fault level available on the secondary side is: 2 MVA x 100/5 = 40 MVA

29. Temperature Rise Winding temperature rise Top oil temperature rise Maximum hat spot temperature rise in core Maximum hot spot temperature rise in copper

30. Insulation Level BIL or Basic Insulation Level Definition: When lightning impulse over voltage appears in the system, it is discharged through surge protecting devices before the equipment's of the system gets damaged . Hence, the insulation of such equipment must be designed to withstand a certain minimum voltage before the lightning impulse over voltage gets discharged through surge protecting devices.

31. Basic Insulation Level (Cont..) Therefore, operating voltage level of surge protecting devices must be lower than the said minimum voltage withstanding level of the equipment. This minimum voltage rating is defined as BIL or basic insulation level of electrical equipment.

32. The lightning impulse voltage is fully natural phenomena and hence it is highly uncertain in nature. So it is impossible to predict the shape and size of lightning surge. After studying and working lots on the nature of lightning surges, the standardizing bodies have decided and introduces a basic shape of impulse wa ve which is used for high voltage impulse testing purpose of electrical equipment's.

33. Basic Insulation Level (Cont..)

34. Impulse Voltage As per American Standard the impulse wave shape is 1.5/40 microsecond. As per IEC Standard this is 1.2/50 microsecond. This representation of the wave has a special significance.

35. Such as 1.2/50 microsecond impulse wave represents a unidirectional wave which rises to its peak value from zero in 1.2 microseconds and then falls to 50% of peak value in 50 microseconds. Impulse Voltage

36. Vector Group What is vector group? The vector group indicates the windings configurations and the difference in phase angle between them. For example: a wye HV winding and delta LV winding with a 30-degree lead is denoted as "Yd11".

37. Different Vector Group

38. Different Vector Group (Cont..)

39. Different Vector Group

40. Transformer connection is divided to 4 groups 24 types. Dy1 Yd1 Yy0 Dd0 Dy3 Yd3 Yy2 Dd2 Dy5 Yd5 Yy4 Dd4 Dy7 Yd7 Yy6 Dd6 Dy9 Yd9 Yy8 Dd8 Dy11 Yd11 Yy10 Dd10

41. Transformer Connection Yd11

42. Transformer Connection Yd11 (Cont.)

43. Transformer Connection Yd11 (Cont.)

44. Weight Information Mass of Core, Coil, Oil, Transportation mass, Total mass, Volume of Oil. No Load Loss For example ≤ 54 kW for a 132/33 kV, 80/120 MVA Transformer. Full Load Loss For example ≤ 350 kW for a 132/33 kV, 80/120 MVA Transformer.

45. Current Transformer information CT Ratio, Class Burden, purpose etc. Tap Changer Information Model No., Vacuum or Oil etc. Standard applied IEC, BS, IEEE, ANSI, IS etc. Year of Manufacturing Makers Serial Number

46. Parallel Operation of Transformer The Transformer is said to be in Parallel Operation when its primary winding is connected to a common voltage supply, and the secondary winding is connected to a common load.

47. Conditions of Parallel Operation When two or more transformers run in parallel, they must satisfy the following conditions for satisfactory performance. These are the conditions for parallel operation of transformers. Same voltage ratio of transformer. Same percentage impedance. Same polarity. Same phase sequence.

48. Why Parallel Operation of Transformers is required? It is economical to install numbers of smaller transformers in parallel than installing a bigger rated electrical power transformers. This has mainly the following advantages: To maximize electrical power system efficiency. To maximize electrical power system availability. To maximize power system reliability. To maximize electrical power system flexibility.

49. Working Principle of Transformer What is a transformer? Electrical transformer is a static electrical machine which transforms electrical power from one circuit to another circuit, without changing the frequency. Transformer can increase or decrease the voltage with corresponding decrease or increase in current.

50. Working Principle of Transformer

51. Its Classification and construction Types of Transformers Transformers can be classified on different basis, like types of construction, types of cooling etc. On the basis of construction: Core type transformer and Shell type transformer

52. Types of Transformers

53. Types of Transformers On the basis of their purpose Step up transformer: Step down transformer: On the basis of type of supply Single phase transformer Three phase transformer

54. Types of Transformers On the basis of their use Power transformer: Distribution transformer: Instrument transformer: Current transformer (CT) Potential transformer (PT) On the basis of cooling employed Oil-filled self cooled type Oil-filled water cooled type Air blast type (air cooled)

55. Selection of fuses for the Protection of Distribution Transformers Rules governing fuse selection are: The rated voltage of the fuse U rf (in kV) must be greater than or equal to the rated voltage of the system. i.e. U rf ≥ U r The short-circuit breaking capacity I 1 (in kAmp) must be greater than or equal to the short- circuit current of the system I ksystem . i.e. I 1 ≥ I k

56. The fault current on the transformer secondary to be interrupted must be greater than or equal to I 3 . i.e. I k ≥ I 3 The resistance of a cold fuse must be multiplied by a coefficient that depends on the cubicle characteristics.

57. Thank You