ISOLATOR of different types used in power system.pptx

isolator

1. ODISHA POWER TRANSMISSION CORPORATION LTD… … By: Sri K. C. Bisoi Dy. Manager (Elect.) PTC, Chandaka ISOLATOR

2. ODISHA POWER TRANSMISSION CORPORATION LTD… … Introduction The open contacts of circuit breaker cannot be visible physically from outside There must be some arrangement so that one can see open condition of the section of the circuit before doing any maintenance work for safety practices Isolator is a mechanical switch which isolates a part of circuit from system as when required Electrical isolators separate a part of the system from rest, for safe maintenance works IEC 129 or IS 9921

3. ODISHA POWER TRANSMISSION CORPORATION LTD… … Working principle The minimum necessary condition for operation of Isolator is “During operation the current flowing through it must be ZERO”. An isolator must not make or break load or fault current. It is also known as “OFF LOAD Switch” It is a mechanical switch which separates a part of the electrical power system normally at off load condition Electrical isolation of various equipment from the live parts for maintenance work. It provide alternate path for power supply at time of maintenance work Isolating faulty equipment Transfer of load from one bus to another

4. ODISHA POWER TRANSMISSION CORPORATION LTD… … Classification Horizontal Break Center break Double Break Vertical Break Pantograph

5. ODISHA POWER TRANSMISSION CORPORATION LTD… … Horizontal Break Center Break Isolators The contact arm is divided into two parts one carries male contact and other female contact. The contact arm moves due to rotation of the post insulator upon which the contact arms are fitted. Rotation of both post insulators stacks in opposite to each other causes to close the isolator. Counter rotation of both post insulators stacks open the contact arm and isolator becomes in off condition. The normal operation of isolator is motorized but for emergency hand driven mechanism is also provided.

6. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 400 KV Center break isolator Isolator open (On Load) Isolator Close

7. ODISHA POWER TRANSMISSION CORPORATION LTD… … Double Break Isolators Horizontal Break These have three stacks of post insulators The central post insulator carries a tubular/ flat male contact which can be rotated horizontally with rotation of central post insulator. This contact is also called moving contact. The female type contacts are fixed on the top of the other post insulators which fitted at both sides of the central post insulator. The female contacts are generally in the form of spring loaded finger contacts.

8. ODISHA POWER TRANSMISSION CORPORATION LTD… … The rotational movement of male contact causes to come itself into female contacts and isolators becomes closed. The rotation of male contact in opposite direction make to it out from female contacts and isolators becomes open. Rotation of the central post insulator is done by a driving lever mechanism at the base of the post insulator and it connected to operating handle or motor of the isolator through a mechanical tie rod . Horizontal Break Double Break Isolators 132KV Double Isolator Double break Isolator open Double break Isolator Close

9. ODISHA POWER TRANSMISSION CORPORATION LTD… … Vertical Break The operating contact and arm moves in vertical plane to open or close the isolator. The fixed contact is mounted on one pole of the isolator The moving contact on other pole, which moves with insulator, by the operating rod. Isolator operation Isolator Operation

10. ODISHA POWER TRANSMISSION CORPORATION LTD… … Pantograph Isolator It require less ground area. The base of the isolator is the frame on which stands the post isolator carrying the head piece with the pantograph and the gear box. The actuating force is transmitted to the gear box by a rotating insulator. The suspended contact is mounted on the bus bar situated above the disconnector. Isolator operation

11. ODISHA POWER TRANSMISSION CORPORATION LTD… … Classification based on S/S Layout Single Isolator Double Isolator Beam mounted isolator Tandem/off set isolator Isolator with single E/S, double E/S or without E/S. Single Isolator Double Isolator

12. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Tandem Isolator Beam mounted Isolator Isolator with single E/S Isolator with out E/S

13. ODISHA POWER TRANSMISSION CORPORATION LTD… … Earth Switches It used to provide permanent earthing of the equipment, circuit under maintenance. Generally E/S are provided with the isolators so that the equipment or circuit which was isolated by the isolator for maintenance can be earthed by earth switch provided in the same isolators. An interlock is provided for locking the main blades and earth switches. 132 KV Earth Switch Earth Switch Opening Earth Switch Closing

14. ODISHA POWER TRANSMISSION CORPORATION LTD… … Major Components 1. Contacts It shall be heavy duty, self aligning & high pressure line type contacts made of high purity, high conductivity, corrosion resistant, hard drawn electrolytic copper of adequate thickness & contact area. The contact area are silver plated >25 micron thickness Arching contact are made up of hard drawn electrolytic copper (make before and break after) The contact springs are not for current carrying so it should not be damaged due to over heating.

15. ODISHA POWER TRANSMISSION CORPORATION LTD… … Major Components 2. Blades All metal parts are of non rusting/corroding material All current carrying parts shall have high conductivity electrolytic copper/ alumunium Isolator & E/S shall be so constructed that it shall be locked in closed/open position and not to be disturbed in case operating shaft becoming disconnected. Isolator & E/S are designed in such a way that 1000 operations or a life time of five years can be achieved before any maintenance.

16. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 3. Fixed Contact The contacts which are fixed at both end in case of double isolator 4. Moving contacts The contact which is fixed at center and moving in horizontal plane to be closed with the fixed contact 5. Insulator stack The post insulators are of creepage distance as follows : 21mm/KV for normal area 25mm/KV for polluted area 31mm/KV for most polluted area

17. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 6. Elevator Plate The plate on which the insulator is placed which is above the Base Chanel. 7. Base Chanel The poles of disconnector placed on a complete galvanized base provided with holes and designed for mounting on structure. These are made up of hard drawn copper Make before and break after: it closes before closing of main contact and it breaks after main contact is fully opened. The arching due to charging current in line, breaking of bus transfer current. 8. Arching Contact

18. ODISHA POWER TRANSMISSION CORPORATION LTD… … Testing Types of Testing Type Test Routine Test Special Test

19. ODISHA POWER TRANSMISSION CORPORATION LTD… … Type Test A) Power frequency withstands voltage test on the equipment and its auxiliary equipment . The isolator under test should withstand the voltage at power frequency (50 Hz). B) Temp . rise test Temperature rise tests are used to make sure that the product does not get overheated during operation. The maximum temperature rise can be determine after continuous full load run. The ambient temperature and time of test should be stated in the test certificate. 400KV 220KV 132KV 33KV Across the Isolating distance 610KV 530KV 315KV 80KV To earth 520KV 460KV 275KV 70KV

20. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … C) Rated short time withstand current test The isolator under test should carry the rated short time current for 3sec. D) Short circuit making capacity of Earth Switch The earth s witches to which a rated short circuit making current has been assigned shall be capable of making at any applied voltage, up to and including that corresponding to their rated voltage, any current up to and including their short circuit making current. 400KV 220KV 132KV 33KV Short Time Current 40/63KA 40KA 31.5KA 25KA

21. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … E) Mechanical Endurance test The mechanical endurance test shall consist of 1000 operating cycles without voltage on, without current in the main circuit F) Lightening impulse voltage test The isolator design in such a way that it can withstand the rated lightening impulse voltage without any abnormality. LIWV ( KVp ) 400KV 220KV 132KV 33KV Across isolating distance 1425 ([phone] To Earth 1425 1050 650 170

22. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … G) Switching impulse voltage test The isolator design in such a way that it can withstand the rated switching impulse voltage without any abnormality. H) Pollution test This tests are intended to provide information on the behaviour of external insulation under pollution. Tests are performed to prove that a test voltage equal to Vm /will be withstood at the specified degree of pollution SIWV ( KVp ) 400KV 220KV 132KV 33KV Across isolating distance 900([phone] To Earth 1050 460 275 70

23. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … I) Partial Discharge test partial discharge  (PD) is a localised dielectric breakdown of a small portion of a solid or liquid  electrical insulation  under  high voltage stress. PD usually begins within voids or cracks, within a solid  dielectric With the partial discharge measurement, the dielectric condition of high voltage equipment can be evaluated, and electrical treeing in the insulation can be detected and located. Partial discharge measurement can localize the damaged part of an insulated system.

24. ODISHA POWER TRANSMISSION CORPORATION LTD… … Special Test 1) Test to prove satisfactory operation under ice condition Under Ice loading condition, If the earthing switch/isolator is manually operated, the test may be considered as satisfactorily completed if the apparatus can be operated manually, and if it does not, sustain damage (which may later interfere with its mechanical or electrical performance). If the isolator or earthing switch is electrically, pneumatically or hydraulically operated, the test may be considered as satisfactorily completed if the apparatus can be operated fully by the operating device supplied at its rated voltage or pressure, and if it does not, sustain damage ( which may later interfere with its mechanical or electrical performance ).

25. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd …  

26. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 2) Test to prove satisfactory operation at minimum and maximum ambient temperature The Isolator or earth switch in the closed position with its operating devices and auxiliary equipment are placed in a test chamber. For Minimum Ambient Temp. The temperature shall be lowered and maintained at the minimum ambient temperature. The apparatus shall then complete 10 operating cycles satisfactorily . For Maximum Ambient Temp. The temperature shall be raised to and maintained at the maximum ambient temperature of 40°C . for a period long enough to reach temperature balance. The apparatus shall then complete 10 operating cycles satisfactorily .

27. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 3 ) Rotor blocked test This test have been conducted for ensuring the proper close and proper opening of the isolator/Earth switch. When the isolator/Earth Switch is perfectly closed then the operating handle should be locked/blocked with some arrangement. Similarly for opening of isolator/Earth switch. Once the isolator get closed, further movement/rotation of operating rod are not allowed.

28. ODISHA POWER TRANSMISSION CORPORATION LTD… … Routine Test 1. Power frequency voltage dry test of the main circuit The isolator and Earth switch are subjected to withstand the power frequency voltage given below for 1 minute. The disconnector or earthing switch shall be considered to have passed the test successfully, if, during the test, no disruptive discharge occurs . power frequency withstand voltage 400KV 220KV 132KV 33KV Across isolating distance 610KV 530KV 315KV 80KV To Earth 520KV 460KV 275KV 70KV

29. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 2. Voltage tests on control and auxiliary circuits Auxiliary and control circuits of Isolator and earth switches shall be subjected to 1 minute power-frequency voltage withstand tests : The test voltage of 2000 V is applied to the auxiliary and control circuits of the Isolator/earth switch. Then there should not be any disruptive discharge occurs during the test. Normally , the test voltage of motors and other devices used in the auxiliary and control circuits shall be the same as the test voltage of 2000 V.

30. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … 3. Measurement of main contact resistance The measurement shall be made with DC supply by measuring the voltage drop or resistance across the terminals of each pole. 4. Mechanical operation test With out Voltage/ Current the main contact of isolator/ earth switch are open or close correctly when there operating devices are energized. It shall also be verified that operation will not cause any damage to the isolator/ Earth Switch. The test shall be carried out: A t rated supply voltage :- 50 operating cycles At specified maximum supply voltage :- 10 operating cycles A t specified minimum supply voltage :- 10 operating cycles

31. ODISHA POWER TRANSMISSION CORPORATION LTD… … Technical specification for isolators in OPTCL Type 400KV 220KV 132KV 33KV 1 Main Switch Double end break centre post rotating, gang operated 2 Service Outdoor 3 Applicable standard IS : 9921 / IEC-62271-102 4 No. of Phases 3 phase 5 Design Ambient temperature 50°C 6 Type of operation Electrically Ganged Mechanically Ganged 7 Rated voltage (kV) In KV In KV In KV In KV a) Nominal 400 220 132 33 b) Maximum 420 245 145 36

32. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Type 400KV 220KV 132KV 33KV 8 Rated current (Amps) 3150 2000 1250 --- 9 Short time current for 3 sec. (KA) 63 40 31.5 25 10 Rated frequency 50 HZ + 5% 11 System earthing Effectively earthed 12 Temperature rise As per relevant IS/IEC standards 13 Lightening Impulse withstand voltage ( KVp ) (a) Across Isolating distance 1665 1200 750 195 (b) To earth 1425 1050 650 170 14 1 minute power frequency withstand voltage a) Across Isolating distance 610 530 315 80 (b) To earth 520 460 275 70

33. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Type 400KV 220KV 132KV 33KV 15 Switching Impulse withstand voltage ( kVp ) a) Across Isolating distance 1245 530 315 80 b) To earth 1050 460 275 70 16 Max. RIV for frequency between 0.5 MHz and 2 MHz (micro-volt) 1000 at 267kV 1000 at 156kV 500 at 92kV --- 17 Corona Extinction Voltage (kV) 320 156 105 --- 18 Operating mechanism a) Isolator Motor b) Earth switch Motor Manual 19 Auxiliary voltage a) Control & Inter lock 220V DC 80% to 110% b) Motor voltage 3 Phase 415V AC 50Hz c) Heater, lamp & socket Single phase 240 V 50HZ

34. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Type 400KV 220KV 132KV 33KV 20 Safe duration of overload a) 150% of rated current 5 minute b) 120% of rated current 30 minute 21 Minimum creepage distance of Insulator (25mm/kV ) 10500mm 6125mm 3625mm 900mm 22 Mounting structure Tubular Tubular/Lattice Lattice Lattice 23 Operating time Less than 12 secs 24 Insulator Data a) Bending Strength ( kgf ) 800 800 800 600 b) Height (mm) 3650 2300 1 500 508 c) Bottom PCD (mm) 300 254 184 76

35. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Type 400KV 220KV 132KV 33KV 24 Bus Bar height from Plinth level (mm) 8000 5900 4600 3700 25 Phase Spacing (mm) 7000 4500 3000 1500 26 Minimum clearances (mm) a) Phase to Phase 4000 2100 1300 320 b) Phase to earth 3500 2100 1300 320 c) Sectional clearance 6500 5000 4000 3000

36. ODISHA POWER TRANSMISSION CORPORATION LTD… … Maintenance Grease all the rotating bearings of insulator stack. Open the hood on the center rotating post and grease all the sliding part including the spring studs. Clean the contacts and apply white petroleum jelly Check the condition of arching horns Clean the operating mechanism cubicle Check the outgoing connections from the main isolator contacts and tighten bolts if necessary.

37. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … During annual maintenance it is recommended to measure the contact resistance of Isolator in on position. Use of any type switch cleaning liquid (preferably CRC 2-26 or Carbon tetra chloride) for cleaning the Aux. contact of Isolator, Fuse terminals and TB Ensure vermin proof arrangement of the Isolator mechanism box which can prevent entry of insects, reptiles and rats .

38. ODISHA POWER TRANSMISSION CORPORATION LTD… … Contd … Ensure Aux. AC supply and operation of space heater which should be available with aux. socket arrangements and door switched lighting and proper functioning of Ensure Aux. AC supply and operation of space heater with its thermostat Also AC supply must be available with aux. socket arrangements and door switched lighting. In case of saline affected area where possibility of corona is more, clean Post insulators surface using water or any other cleaning agent.

39. ODISHA POWER TRANSMISSION CORPORATION LTD… … Conclusion A complete live closed circuit must not be opened by isolator operation and also a live circuit must not be closed and completed by isolator operation to avoid huge arcing in between isolator contacts. As no arc quenching technique is provided in isolator it must be operated when there is no current flowing through the circuit. No live circuit should be closed or open by isolator operation.

40. ODISHA POWER TRANSMISSION CORPORATION LTD… … References IS : 9921 OPTCL Material, “Transmission and Distribution System” CPRI material, “Testing & Maintenance of Electrical Equipment” Search Engine: Google IEEE YouTube

41. ODISHA POWER TRANSMISSION CORPORATION LTD… … Any Q?

42. ODISHA POWER TRANSMISSION CORPORATION LTD… … Thank You