The reliability of the power supply in the system can be improved only if prescribed standards are followed in erection, execution, construction and maintenance of the line works and equipments. At present more number of interruptions are recorded in rural as well as in urban areas even though many remedial measures are taken by the engineers and staff. It is observed that the majority of the line faults are occurring on the newly erected 11KV overhead system and DTR’s HT points. Non-maintenance of tree clearances to the power lines, lesser phase to phase and phase to earth clearance are also causes for the power breakdowns.

Improper alignment of poles, more sag between consequent poles, non-providing of stays at angle/cut point, clearances between the line conductor and channel cross arm, improper concreting of the pole/stay/studs are causing damage to the equipment particularly at the time of heavy gale and wind conditions.

The power interruptions are also due to failure of insulating materials (Worn-out cases), cut conductors, improper jumpering, DTR failures or failure of solid core insulator.

In some of the HT services failure of CTPT sets, cable and end terminations, low clearance of the bushing (to the cover) in the CTPT set incoming side are some of the reasons for power interruptions.

Due to the improper maintenance of the lines and by the concerned, the interruptions are observed in odd times also. The existing man power is unable to meet the crisis in emergencies. So the essential commodities of the consumer are not properly served in time leading discomfort to their routine life and revenue loss to the organization. In addition to the above, a bad image created on the Distribution Company also.

Interruptions & Breakdowns – 30 Reasons

  1. Low clearances at the middle point of the line due to horizontal to vertical formation.
  2. Less phase to phase clearance and phase to earth clearance in the line.
  3. Less HT / LT clearance.
  4. Less tree clearance and entangling of plant creepers to lines.
  5. Falling of foreign material on the line during construction activities, nearby.
  6. Falling of advertisement Boards on the line (while heavy gale).
  7. Jumper cut at the cut point.
  8. Kite sticks, bird faults, bird nest on the overhead line.
  9. Less clearance between middle phase conductor and the pole/top clamp /tilting of the cross arms.
  10. Loose contacts at male, female contacts of the AB Switches/directing of the AB Switches /failure of nylon bushes /springs.
  11. Coming Brass patties on the AB Switch in contact of the structure.
  12. Failure of cable end terminations/straight through joints & less clearance of phase to phase at end-Joints.
  13. CTPT low megger values resulting in failure.
  14. CTPT incoming side less clearance between the bushing to the closing cover (Non providing mono plast).
  15. Low IR values of the supporting insulators in Ring main unit.
  16. Failure of DTRs.
  17. Unbalanced load in single-phase system.
  18. Failure of insulators, discs or LAs /solid core insulators
  19. Providing of higher size L.T Fuse wire/HG Fuse wire and more arcing horn gap.
  20. Slipping of conductor/ Snapping due to pole damages or Leaning.
  21. Weak joints in the conductor (poor binding).
  22. Conductor standing only on the steel wire support (as more no. of aluminum strands are cut in case of ACSR).
  23. Clearance between the power lines and Guarding / Street light brackets.
  24. Failure of insulation in the LT cables.
  25. Rusted M.S bolts and nuts at DTR bushing clamps resulting loose contact and consequent opening of jumper / cable.
  26. RMU’s with back side doors opened or gaps at the entry of the cables (results in rat / squirrel / lizard faults).
  27. Improper relay settings in the breaker.
  28. Failure of CTs in the feeder breaker.
  29. Poor quality materials used in the turnkey works.
  30. Construction of buildings / structures close to the lines or underneath.

Quality and reliability of power supply can be improved by identifying and addressing the above defects at the earliest by the field engineers and line staff.

“Reliable power supply not only improves Company’s revenue but also consumer satisfaction as well”

By Er. P Raghavendra Rao, AMIE, CE (India)