1. EVENT LOGGER Contd..  Process of Data Down Load  Data Down Load to Station Monitoring System

2. EVENT LOGGER Contd..  Data Down Load for ABB make Relay INDACTIC 425

3. EVENT LOGGER Contd..  Data Down Load for Siemens make Relay 7SA522--series

4. DISTURBANCE RECORDER  What is Disturbance Recorder?  Why is it required for Sub-Station?  Functions of disturbance Recorder  Records the sequential data events.  Provides the status of power systems  Pre and post fault data of parameters  Information of the disturbances  Analysis of values in wave form or vectorial form.

5. DISTURBANCE RECORDER Contd…  Basic Principle of Disturbance recorder:  Initiation of Digital or Analog pulse due to disturbance  Sampling of the pulse for data acquisition.  Buffer is used to distinguish the pre and post fault condition of disturbance  Time stamped for correct sequence  DI signal filter is used for correct memory storage  Data becomes ready for communicable

6. DISTURBANCE RECORDER Contd…

7.  Application and Settings of Disturbance recorder:  Setting through HMI or PC  Selection of Binary Inputs and logical out puts for the relay action.  Application for Trip Analysis and event analysis.  Selection of Electrical Equipments for correct action.

8. FAULT LOCATOR  What is Fault Locator?  Why is it required for Sub-Station?  Functions of fault Locator  Records the fault data.  Pre and post fault data of parameters  Locates and indicates the distance of fault occurrence.

9. SUB STATION OPERATIONAL CONCEPTS Equi-Potential Concept: Synchronization Charging: Parallel Network Charging Power flow Calculation Parallel Operation of Transformer Interlock Scheme MF for Indicating meters: Under frequency Load Shedding Concept System Islanding Pole Discrepancy concept LBB Concept Auto reclose Concept Concepts on Ground

10. OPERATIONAL CONCEPTS Equi-Potential Concept:

11. Operation for Change to Transfer Bus Equi-potential Concept B A A C B 52B 89A 52L C D B B A 52T 52L C D PT1 PT2

12. Parallel Operation for Bus Change Over B A A C B 52B 89A 52L C D B B 52T 52L C D PT1 PT2

13.  Synchronization Charging OPERATIONAL CONCEPTS Contd.. 29M 52L 29L 29T 25 PT1 PT2

14. Power flow Calculation Thumb rule Current = (600 x MVA)/ KV Actual rule Current = (577 x MVA) / KV OPERATIONAL CONCEPTS Contd..

15. Parallel Operation of Transformer CONDITIONS FOR PARALLEL OPERATION Same vector group.,Same voltage ratio Same frequency, Same polarity Same phase rotation LOAD SHARING For two Transformers PA = P (QA.ZB) / (ZA.QB + ZB.QA), PB = P (QB.ZA) / (ZA.QB + ZB.QA) For 3 Transformers PA = P (QA.ZB ZC) / , PB = P (QB.ZC ZA) / , Pc = P (QC.ZA.ZB) /  Where  = (QA.ZB ZC + QB.ZC ZA + QC.ZA.ZB) OPERATIONAL CONCEPTS Contd..

16. Parallel Operation of Transformer

17. Concepts on Contacts and Position of Switch N I T 1 5 3 10 8 4 6 2 7 9

18. Circuit Breaker :- N ot allowed to operate if adjacent isolators are in operation Applications for CBs, isolators and earth switches Can be electrical, mechanical or electromechanical or combined Inter lock Concept: Isolators No operation on power current or interconnection of different voltage system. No operation when CB in series in close, adjacent Earth switch on close condition Making or breaking of paralleling circuits is permitted Earth Switch Earth switches may only be operated if the isolators on both sides are open. Only an open CB is not enough

19. L1 B1 52B1 B2 52B2 Ring Bus System DIFFERENT BUS ARRANGEMENT.. 29M 52L 29L Single Bus System

20. Main and Transfer Bus 29M 52L 29L 29T 29M1 29T1 52B 29M1 29M2 52B 29 L1 52 L 29 L2 22 B 29MB1 29MB2 Two Bus System

21. Two Bus and Transfer System 29MA 52A 29LA 29TA 52T 29TB 52B 29LB 29MB One and Half System

22. Arrangement for Main and Transfer Bus Scheme 29M 52L 29L 29T 29M1 29T1 52B 29E 52B 29E 29T I/L All Bay 29 T Open N I T 52B52L

23. OPERATIONAL CONCEPTS Contd.. MF for Indicating meters Example1 :- Meter data CTR=-/1, PTR=11KV/110 Line CTR=400/1, PTR=33KV/110, So MF=1200 Example2:- Meter data CTR=-/5, PTR=-/110 Line CTR=400/1, PTR=11KV/110, So MF=200000

24. OPERATIONAL CONCEPTS Contd.. Under Frequency Load Shedding Load

25. OPERATIONAL CONCEPTS Contd.. System Islanding Scheme Load

27. Pole Discrepancy Concepts Applicable to the Individual pole operated Breaker. A A C C B B

28. BAA C B 52L 89A 52L C D B B A 52T 52L C D PT1 PT2 LBB Concepts D

29. Auto reclose Concept

30. . Auto reclosing principles SETTING CRITERIA Dead Time  Auto- reclosing requires a dead time which exceeds the de- ionising time  Time required for the de-ionising of the fault path depends on:- arcing time, fault duration, wind conditions, circuit voltage, capacitive coupling to adjacent conductors, etc.  Single phase dead time of 1.0 sec is recommended for both 400kV and 220kV system.

31. Minimum Dead Time (IEEE)

32. SETTING CRITERIA Reclaim Time  The time during which a new start of the auto-reclosing equipment is blocked.  If reclosing shot has been carried out and the line is energized and a new fault occurs before the reclaim time has elapsed, the auto-reclosing equipment is blocked and a signal for definite tripping of the breaker is obtained.  After the reclaim time has elapsed, the auto-reclosing equipment returns to the starting position and a new reclosing sequence can occur.  The reclaim time must not be set to such a low value that the intended operating cycle of the breaker is exceeded, when two faults incidents occur close together.  If the breaker is closed manually, the auto reclosing equipment is blocked and cannot start again until the reclaim time has elapsed.  For the breaker to be used for auto-reclosing, it is essential that it has the operating mechanism and breaking capacity necessary for it to be able to perform the auto-reclosing sequences required.  The recommended operating cycle at 400kV and 220kV is as per the IEC standard. Reclaim time of 25 sec is recommended

33. Concept on Ground in the system Gound fault in Unground system V R N V Y V B V RY V YB V BR N V Y1 V RY1 V R1 V R V Y

34. Meaning of Equipment Codes 89:- 52:- 86:- 67:- 21:- 30:- 51:- 95:- 99:- 81:- 89:- Isolator/ Air Break Switch 52:- Circuit Breaker 67:- Directional O/C Relay 21:- Distance Protection Relay 30:- Annunciation Relay 51:- Non- Directional O/C Relay 95:- Supervision Relay 99:- Over Flux Relay 81:- Frequency Relay 86:0 Master Relay

35. Meaning of The Drawing Fig-A 1.89A can be operated when Breaker is OPEN 2.Isolator 89B can be operated when Breaker and Earth Switch are open. Fig-A.

36. Explain the Protections provided to the Transformer Non- Directional Back Up Relay, Temp. Relay Current Balance Relay, Differential Relay, REF Relay, Under Voltage, Over Voltage, Voltage/Frequenc y Relay

37. Positioning of Equipments 220 KV system LAParallel ( Line – Earth) CVTParallel ( Line – Earth) WAVE TRAPSeries CTSeries EARTH SWITCHParallel ( Line – Earth) LINE ISOSeries CBSeries BUS ISOLATORSeries

38. CT ratio Calculation S2S1 I 1 2 R1 = I 2 2 R2 I2/I1 = (R1/R2) 1/2 I2= 200x 2/1.732 I2=231 200/1

39. Abbreviation of Terms 1.MCOV 2.NDC 3.ONAN 4.HSV 5.BIL 6.ALF 7.IEC 8.ISF 9.IS 10.TOV MCOV= Maximum Continuous Operating Voltage NDC:- Nominal Discharge Current ONAN= Oil Natural Air Natural HSV= Highest System Voltage BIL= Basic Insulation Level ALF= Accuracy Limiting Factor IEC= International Electro technical Commission IS= Indian Standard TOV= Temporary Over Voltage ISF= Instrument Safety Factor

40. CT Connection on secondary Which Connection of CT Secondary is correct. S2S1S3 S4 R S2S1S3 S4 R Fig-1 Fig-2 Answer Fig-1

41. Explain the operations for Main Bus-1 Maintenance Work, considering the safety aspects in mind B A A C B 52B 89A 52L C D B B A 52T 52L C D PT1 PT2

42. Calculate MF of the meter One MWh Meter has data CTR=-/1, PTR=33KV/110 With Line CTR=400/1, Line PTR=33KV/110, Meter reading Advance is 20000. Calculate Million Unit energy Consumed. MF of MWh meter is 400x20000= 8,000000 Mwh So Million Unit Consumed= 8,000000x1000 unit= 8,000 Million Unit

43. Situation for AC source mixed L A B -Ve+ Ve 1 St 55 th 110 th THEORY –A +ve Terminal of 1 st Cell, got connected to the phase of 1 ph AC source, What will happen to the Status of Bulb glowing Bulb A will glow brighter and flicker may be fused

44. Delta Connection Load and One Terminal is Earthed Draw the Vector diagram B Y R Vbr Vry Vby Vr Vb Vy Vby Vbr Vry

45. Questions for discussion 1. What is the difference between earthing and neutral 2. Why Wave Trap is connected in Rph and Bph but not in Yph 3. Why “MW Meter” shows both +ve and –Ve reading ( i.e. Export and Import) while current (Ammeter) only shows one side reading 4. Why single break Isolator is preferable to double break isolator 5. Why auto transformer ratings are generally rated with ratio less than 2, but two windings transformer are rated more than 2 6. When two transformers are operating in different tap position is there any chance of operation of E/F or REF relay in any of the transformer 7. Why O/C relays are connected to R & B Phase but E/F relay is connected to Y Phase 8. What will happen to a CT of a feeder if its secondary was opened when feeder is idle charged and drawing no load 9. Why it is not advisable to use AR scheme for Gang operated breaker system 10. Does it need to provide Wave trap on each phase of the transmission line at the sub-station

46. Questions for discussion 11. Why the use of combined instrument transformer is not gaining popularity in India. 12. Why the spring-spring mechanism is gaining popularity in Breaker Technology 13. Which circuit is important for supervision of breaker trip coil status?(Pre-close supervision, post-close supervision) 14 Why DC Voltage is preferable for the protection and control circuit in System Network 15. What are the reasons for variation of voltage due to increase of load in the system 16. Most of the Power transformers are of Y connected, why not ∆ connected 17. We know that Voltage is directly proportional to frequency, but sometimes voltage decreases but not the frequencies why? 18. In case of 3ph, 4wire system, and the neutral is disconnected. Why the meter showing the value above 350volts in 2 phases? 19. Why REF protection is not considered as 100% protection to the equipment winding 20. Why PT of different rating is used [110V /√3 and 110V]

47. 21. Why PS class core is best suitable for the application to Differential Relay 22. Can performance of REF relay be reduced if its residual current circuit is obtained in series with E/F relay in the scheme 23. Which protection is better, either REF protection or Differential protection for Transformer 24. Why REF relay is grouped under high impedance relay? 25. What is the significance of INTER position for a NIT switch on a feeder bay control panel. 26. Why Guard terminal is used during the measurement of IR value of electrical equipment. 27. Explain the concept for which the IR value at 30 sec becomes more than the IR value at 15 sec, for good insulator system. 28.Can the Magnetic Balance Test be considered as a signature test for transformer fault diagnosis? 29. Questions for discussion

48. Draw 3 Over current + E/F Relay circuit and 2 O/C + 1 E/F Relay circuit

49. Develop REF circuit for a 3 winding Transformer

50. Auto reclose Concept

51. Ground fault in Un grounded System. V R N V Y V B V RY V YB V BR N V Y1 V RY1 V R1 V R V Y