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D.L.F. Type Air Blast Breaker H.B.B. Make

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The breaker design is based on a multiple break principle with controlled voltage distribution comprising the following main parts. :-

  • Arc extinction units.
  • Control units.
  • Supporting insulators.
  • Air receivers.
  • Apparatus Cubicle.

A complete 220 kV. triple pole breaker consists of three identical poles and control cabinet containing the controls.

Constructional and Operational Features:

In the closed position of the breaker the nozzle type contacts are closed. The interrupting chamber, insulators column and compressed air tank are under service pressure.

An opening command to the control block unlatches the opening spring charged mechanism and the primary control valve is changed over. Compressed air rushes under the driving piston, the pressure on both side is balanced and the compressed air acting on the lower side of the control valve piston pulls the control rod upwards. The inrushing of compressed air actuates the blast valve piston and at the same time arrives under the exhaust valve disc. The blast valve and the exhaust valve open and ventilate the interior of the nozzle shaped contacts, which pushes the driving mechanism and pulls the contact in to the open position.

A closing command unlatches the 'Close' spring charged mechanism in the control block so that the primary control valve is changed over. The space under the driving piston is thereby ventilated and the control rod is pulled down in to its end position. The trapped compressed air lifts the exhaust cover and the cylinder of the driving mechanism tube closes the moving contact very rapidly during the closing movement of the contact the retarding valve causes a momentary impulse type opening of the blast valve so that probable pre-closing arc is immediately pulled in to the nozzle of the fixed contact by the inrushing compressed air.

Yearly Maintenance

20 B-01 Y Cleaning :
  • Do as described in Sub-Para 20 A-01 Y
20 B-02 Y Air Leakage :
  • Do as described in Sub-Para 20 A-02 Y
20 B-03 Y Earthing :
  • Do as described in Sub-Para 20 A-03 Y
20 B-04 Y Lubrication :
  • Do as described in Sub-Para 20 A-04 Y
20 B-05 Y Foundation :
  • Do as described in Sub-Para 20 A-05 Y
20 B-06 Y Heaters :
  • Do as described in Sub-Para 20 A-06 Y
20 B-07 Y Wiring Connection :
  • Do as described in Sub-Para 20 A-07 Y
22 B-08 Y Jumper & Clamps :
  • Do as described in Sub-Para 21-08 Y
20 B-09 Y Tripping of Breakers :
  • Do as described in Sub-Para 20 A-09 Y
20 B-10 Y Tripping of Breaker at 50% D.C. Voltage : :
  • Do as described in Sub-Para 20 A-10 Y
20 B-11 Y Contact Resistance :
  • Do as described in Sub-Para 20 A-11 Y
20 B-12 Y Record, if any other defect also attended.
20 B-13 T Tripping Based Maintenance :

Record number of short circuit current tripping and identify the pole which has cleared the fault current.

Replacement Of Interrupting Chamber Contacts :

Fixed contact nozzle (5130) and moving contact nozzle (5350) should be replaced after the number of operations as given below :-
Breaking current (In KA) Rated Current 5 10 20 40 50
No of operations.   2500 1000 200 50 12 8

For replacement of contacts see Maint. Manual.
20 B-14 T Cleaning of Insulators :

Interrupting chamber insulators should be cleaned internally when ever contacts are being replaced in the following manner :-

  • Clean with trichloro ethylene/Acetone and allow to dry. Use only chamois or sheep skin leather or mulmul cloth.
  • Clean the rim of insulator (gasket base).
  • Prevent from getting diet inside by covering.
20 B-15 T Treatment on Contact Surfaces :

Treat the contact surfaces, contact flange (5007) and finger holder (5090) :

  • Bare contact surfaces (Aluminium) should be greased as per remark of respective manual.
  • Silver plated contact surfaces (Aluminium or copper) should only be greased with contact grease or DC 55 m. grease.
20 B-16 T Replacement of O-Rings :
  • Do ensure that all the gaskets and O-rings which are removed from breaker are replaced with new.
  Maintenance To Be Done After 10 Years Or After Every 5000 Operations (Which Ever Is Earlier)
  • Necessary special tools to be procured as per HBB manual.
20 B-17 TN Replacement of Gasket Rings :

All the gasket rings should be replaced if.

  • They are damaged or have become brittle.
  • They are distinctly deformed in cross section.
  • They are 10 years old.

For embedding and glueing gasket rings, proper adhesive (Dunlop Maxi fix) should be applied at 4 to 8 points after cleaning the groove and gasket with Trichloro Ethylene/Acetone.
20 B-18 TN Regressing Of Sliding Gasket And Sealed Sliding Surfaces :
  • Sliding gaskets should be smeared all round with silicon grease DC 55 m before mounting.
  • Sealed sliding surfaces should be cleaned, if necessary with cleaning medium. After wards silicon grease DC 55m should be applied in a thin layer.
20 B-19 TN Checking Of Interrupting Chamber Contacts :
  • Do as described in Sub-Para 20 B-13 T
20 B-20 TN Cleaning Of Insulators :
  • Do as described in Sub-Para 20 B-14 T
20 B-21 TN Treatment Of Contact Surfaces :
  • Do as described in Sub-Para 20 B-15 T
20 B-22 TN Replacement Of Gaskets & O-Rings :

Replace gaskets at the following places and see Necessary reference of Maint. manual for details.

  • Control rod drive.
  • Control block.
  • Magnetic valve block.
  • Auxiliary Switch Drive.
  • Interrupting Chamber.
  • Ventilating valve.
  • Exhaust valve.
  • Driving mechanism.
  • Blast valve.
  • Control cubicle.
  • Auxiliary switch drive.
  • Pressure reducing valve.
  • Supporting Insulator Column.
20 B-23 TN Checking Of Control Rod :

Check if the glass fibre of control rod has become dirty and dielectric strength reduced. If yes then clean it with petrol or trichloroethylene. Do not use acetone as it removes the protective layer.

Check the distance between drive holder assembly which should be 32 mm.
20 B-24 TN Maintenance Of Closing Resistors :

Check Resistor Contact (6240). Polish away all the possible sears and dusts due to burning or pitting of the contacts by means of emery paper. After wards clean the resistor contacts and the interior of the insulators as described in 22 B-14.

  • Check contact nozzle (6110) and polish away all the possible scars and dents due to burning or pitting of the contacts by emery paper.
    After wards clean the contact nozzle carefully the metal dust due to polishing. should not remain behind.
  • Apply slight smear of DC 55m grease on resistor contact and contact nozzle.
  • Replace the O-Rings when ever required.
20 B-25 TN Check The Air Receiver For Emalite Paint :
20 b-26 TN Refilling And Checking Of Abcb :
  • Fill the ABCB with air as per instruction manual.
  • Measures loss of pressure during operation.
  • Check phase discrepancy operation.
  • Check all indicators, alarm/interlocks.
  • Contact heaters.
  • Note down and compare the results of leakage in 24 hours.
20 B-27 TN Measurement Of Timings :

The measurement of switching times is made with a time recorder. Various times applying to the number of interrupting chamber per pole are recorded. Following times are required to be measured :

  • Closing time.
  • Opening time.
  • Open Close open time.
  • Close open time.

Take advice of firm if necessary.

Trouble Shooting :

In case of emergency and break down following procedure will be followed :-

Sl. No. Trouble Probable Cause Action to be taken Remarks
1. Leakage of air 1. Air pipe Leaking.  

Check all flanges, threaded, and soldered connections as well as joints. Resold the joints or replace joints fittings.

Before beginning any work the breaker has to be disconnected from the net work and earthed. The auziliary supply to be disconnected and compressed air drained.
2. Static gasket leaking. Replace damaged gasket.
3. Pressure reducing valve leaking. Replace damaged gasket.
4. Control valve/exhaust valves leaking. Replace defective gaskets. (Sliding gasket and impact gasket.)
2. Faulty execution of operating commands. 1.  Loose connections in control circuit. Check and tighten loose connections in control cubicle.
2. Wrong wiring. Compare wiring with wiring diagram and rectify.
3. Defective coils Determine reasons for over load rectify the defect and replace coil.
4. Operation in wrong pressure ranges. Check adjustment of micro switches and re-adjust them.
5. Refilling starts at wrong pressure range or not at all. FOX contacts of pressure switch 8800 are disturbed, check and adjust micro switches also.
6. Coil in reducing val>
7. Control voltage has sunk appreciably. check and rectify electrical circuit of reducing valve.
3. Oil leakage from Capacitor 1. Damage of gasket. Replace capacitor and send the defective unit to manufacture for repair.
2. Damage Insulator

Replace capacitor.
4. Air leakage in open position only. (For 33 kv. volta's ABCB.) 1. Leakage from conduit insulators Replace conduit insulators.
2. Leakage from outer timing valve.

Replace gaskets/valve sets.
5. Leakage from pressure relaying valve 1. Defective gasket. Replace gaskets
2. Defective diaphram. Replace diaphram.