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Abstract from Model Code for Safe Operation and Maintenance of Transmission and Distribute System

(Abstract of clause 12.03.04 to 12.11.02)
[Published by-Ministry of Irrigation and Power (Central Electricity Board) PMIP-27 / 2,000-1979 (DSK-II)]
Sr. No. Subject
12.3.4 The undertaking shall prepare forms of inspection reports with due regard to the particulars of their installation, voltage, defects likely to occur on the lines and the Inspecting Officers shall report on the defects and remedies there of to next senior officer on these forms.
12.3.5 Inspection and maintenance work on steel towers and structures shall include:
(a) Weekly Inspection:
(i) Foreign matter, branches and/or trees being on or so close to supply lines as to constitute potential danger to the lines shall be removed.
(ii) Patrolman's pathways shall be cleared.
(iii) Accumulation of material below or near structures, thus creating fire hazard shall be removed.
(iv) Good and healthy condition of suspension insulators and strain discs shall be ensured.
(v) Any bolts responsible for undue vibration of Tower members shall be tightened.
(b) Quarterly Inspection:
(i) Signs of rusting or loose bolts, pins, etc., or damaged members.
(ii) Condition of footings and anchors, particularly in locations subject to soil erosion, movement of settling.
(iii) Broken strands and corroded ground connections.
(iv) Condition of insulators to detect broken skirts and excessive dirt.
(v) Existence of number plates, danger notices, anticlimbing devices-these are liable to be tampered by village urchins.
(vi) Anything unusual.
(c) Annual Inspections:
(i) Footings for cracking and spalling.
(ii) Existence of safety and protective devices according to I.E. Rules.
(iii) Splices with field glasses.
(iv) Damper supports and grading shields. These should be tightened at the same time.
(v) Clamps, pole heads and other hardware. These should be tightened at the same time.
(vi) Chipped paint or rusty spots. (These should be painted at the same time).
(vii) Broken insulators, chipped and glass burned spots shall be replaced at the same time.
(viii) Earth resistance.
(ix) Anything unusual.
(d) Three to Five Year Interval:
(i) Tighten all bolts and apply good paint on the structure.
(ii) Brush rusty spots and apply good paint on the structure.
(iii) Check buried metal work or corrosion, apply two coats of black emulsified asphalt paint on the tower legs 18 inches (45.72 cm.) above and below the ground line and over the top of concrete footings where used.
(iv) Adjust sag and clearances where necessary.
(v) Conductors and overhead ground wires at supporting clamps at 5 year intervals for signs of weakening and burns and reinforce as necessary.
12.3.6 The following precautions shall be taken for inspection of equipment on or in the vicinity of live lines:
(a) Inspection shall be carried out by authorised persons only.
(b) No tool shall be taken up the line support.
(c) No employee shall climb above the anti-climbing device until under observation by a safety man at the ground level.
(d) Inspection shall be carried out from within the body of the tower.
12.3.7 Line patrolmen shall avoid-
(a) Patrolling lines alone in darkness of under bad weather conditions.
(b) Walking into fallen wires or metal fences which may be energised by fallen conductors.
(c) Stumbling hazards poisonous snakes, plants, etc.
(d) Throwing lighted cigarette ends, matches, etc., to avoid fire hazards.
12.3.8 In case an employee has noticed a fallen aerial wire, he shall immediately inform the departments concerned and arrange to protect till the arrival of repair gang
12.3.9 For Testing of H.V. and E.H.V. Apparatus and lines, the provisions of paragraph No. 11.19.1 shall apply.
 

(Additional Provision Relating to Distribution System)

12.3.10 Inspection and maintenance work on wood poles and single pole lines shall include :-
  (a) Inspection of poles for rot at ground line, hollow rot, splitting, damage due to twisting or ranking. All grass weeds and any other inflammable material shall be kept at least 2 ft. (60.96cm) away from the base of the pole.
  (b) Inspection of cross arms for rotting, splitting and twisting, loose, broken or missing pins, loose or missing braces.
  (c) Checking of insulators for unscrewed, cracked, chipped or broken condition.
  (d) Checking of conductors for broken strands twisted spans, loose, connections, clearances from tree twigs, limbs, kite strings, etc,
  (e) Checking of earthing connections for structures shall be discouraged.
  (f) Public tying cattle to poles or structures shall be discouraged.
  (g) Urching attempting to climb poles or structures shall be discouraged.
12.4. Work on Overhead Lines:
12.4.01 The provisions of paragraphs 11.03.05 and 11.04 shall apply to all such work.
12.4.02 Before any work is begun on overhead lines, the leader of the working party shall ensure that each person, who is to work on the poles, towers, conductors or other components is clearly informed and thoroughly understands on which components the work is to be carried out.
12.4.3 All persons, while at work on towers, poles and high structures shall make proper use of their safety belts and no man shall work alone at any high structure. Before any wood pole is climbed, it shall be sounded and no pole, the condition of which is doubtful, shall be climbed, without the permission of the lender of the working party.
12.4.4 Safety straps shall not be placed above the top cross arm when it is at the top of the pole.
12.4.5 Broken insulators or other sharp edged material shall not be left in vacant plots or in a location where the hazard of cutting fit would be caused for men or animals.
12.4.6 When stringing wires across streets and highways, avoid interfering with traffic or causing injury to workmen of pedestrians. Danger sings shall be erected on both sides of the work site and where conditions warrant, flag men shall be stationed.
12.4.7 All employees working on live wires, wherever possible, shall work from below the wires.
12.4.8 Each working party shall be provided with a portable earthing conductor, fitted with clips, and the leader of the working party shall satisfy himself that the line conductors are discharged to earth attaching the earthing conductor and then to all the line conductors near the point where he is to work. The portable earthing conductors shall be issued by, and shall be returned to the leader of the working party, who shall ascertain that all portable earthing conductors issued have been returned before he declares the line safe to be made alive.
12.1.9 No work shall be begun on any High or Extra High Voltage overhead line unless the temporary earths have been attached at the point or points where work is to be carried out and short circuited at a point on each side of the section of the line on which the work is to be carried out.
12.4.10 Work may be carried out by a competent person on any pole or tower supporting live high voltage conductors provided that he does not ascend beyond a position in which it is possible for him to bring any part of his body of any working tool within the following distances of any exposed high voltage conductor:-
12.4.11
Rated Voltage Clearance
Not exceeding 11 KV 0.9144 metres (3 ft. 0 in.)
Exceeding 11 KV but not exceeding 33 KV. 1.219 metres (4 ft. 0 in.)
Exceeding 33 KV but not exceeding 66 KV. 1.8288 metres (6 ft. 0 in.)
12.4.12 In the event of the event of the near approach of lighting storm, all work on overhead lines shall cease immediately and the employees concerned shall descend from the towers or poles and shall keep clear of the line until the danger has passed and inform the Senior Authorised Person.
12.4.13 If the leader of the working party, together with the working party, lives the line at any time, so that the part of the line on which work is in progress is out of sight of such person and the party, the person shall verify that local earths are in position before work is restarted on the line.
12.4.14 Before climbing elevated structures the employee shall ensure himself that the structure is sound enough to sustain his weight safety.
12.4.15 When two or more linemen are ascending a pole or structure the second man should not start climbing until the first man is in a safe position or when descending the lower man should reach the ground first before the other man start descending.
12.5 Additional Provision Relating to Transmission System:
12.5.1. Work on single or multiple circuit overhead lines with all conductors dead.
  • The work shall be carried out under a suitable clearance.
  • The employee in charge at each tower shall be provided with a green flag which fits the socket for that circuit on the tower on which work is to be carried out and shall place the green flag in position before allowing any man to ascend the tower.
  • The conductors shall be efficiently connected to each by the Authorised Person or a Competent Person working under his direct supervision at the point of work unless they are to be broken, or let down for examination. During this time the conductors shall be earthed at the nearest tower on each side of the point of work where they are still secured in the clamps, but in no case shall the earths be more than six spans apart.
  • When work is to be carried out on lines of all insulated construction and an earthing point is not provided at the point of work. The line shall also be earthed at the nearest line earthing point on either side of the point of work.
12.5.2 Work on double circuit overhead lines with one circuit live.

Where work similar to that covered under paragraph 12.5.1 is to be carried out on double circuit overhead lines with one of the circuits live, the provisions of paragraph 12.5.1 shall apply, and the following additional precautions shall be taken :-

  • After placing in position the green flag, which shall fit the socket on the dead side of the tower and before any other employee is allowed access to the tower, the Authorised Person or the Competent Person working  under the direct supervision of the Authorised Person at the point of work shall climb the tower on the DEAD side, and shall efficiently connect to earth all three conductors on that side. He shall then affix red pennants to the Cross arms supporting the live conductors at the junction of these cross arms with the tower body. The conductors shall remain efficiently earthed, and the red pennants shall remain in position, throughout the progress of the work, and the earths and pennants shall be removed by the Authorised Person  or Competent Persons working under his direct supervision only after all other member of the working party have descended the tower on completion of the work. While affixing or removing earths and red pennants, the persons concerned shall be under observation by another employee at ground level.
  • The Authorised Person in charge shall see that danger notices are fixed to make it clear to all concerned on which portion it is safe to work and shall issue to each person, who is to work on the poles or towers, an armlet or wristlet bearing the distinguishing number or symbol of the overhead line on which he is to work. The armlet of wristlet shall be worn by the person to whom it is issued during the whole period that he is engaged on the work. He shall not bring any part of his body or any working tool within the distance, specified under para : 12.4.11 above, or any live conductor. On the conclusion of the work, the armlets or wristlets shall be collected by the Authorised Person.
  • Work on TEE-OFF tower shall only be carried out in the presence of a Senior Authorised Person and special care shall be taken at terminal and large angle towers.
12.5.3 Work on triple circuit lines with horizontal spacing between circuits with one or more other circuits live.
  • The work shall be carried out as per provisions of paragraphs 12.5.1 and 12.5.2
  • Separate means or access to each individual circuit, as provided, shall be used for work on any circuit.
  • Unless the clearances from the nearest point of work to the remaining live circuits are strictly in accordance with the provisions of paragraph Nos. 12.4.11 care shall be taken to provide screens as per provisions of paragraph 11.4.5.
12.5.4 Work on quadruple circuit lines with one or more other circuits live.
  • Work shall be carried out as per provisions of paragraphs 12.5.1 and 12.5.2.
  • Both the circuits on the side of the tower on which work is to be carried out shall switched out, isolated and earthed.
12.6 Additional Provision Relating to Distribution Systems :
12.6.1 Work on pole mounted sub-stations :
  • The work shall be carried out under a permit-to-work, sanction-for-test or self-protection guarantee.
  • Before changing or replenishing oil in, or painting, the transformer all exposed live parts of the transformer shall be disconnected.
  • While working on poles which have lightening arresters installed on them, the workmen shall avoid touching lightning arresters and the lightning arrester ground wires.
  • Open flame shall not be brought near an open transformer.
12.6.2 Erection of lines on existing poles :-
  • The new line shall be earthed and remain as such till the completion of the work.
  • Unless the existing line is dead and earthed, every employee handling the new line shall use insulating gloves and boots or galoshes.
  • No employee shall be on any cross arm on which the new line is to be erected while such a line a being pulled up.
12.7 Work on Clearing an Obstruction Causing Delay or Inconvenience to Important Services
12.7.1 A permit-to-work shall be obtained and in cases of damage or likelihood of damage during work, the work shall be carried out by the senior Authorised Person under his personal supervision.
12.7.2 Temporary earths shall be installed at the point of work.
12.7.3 For any other work that may be required to be carried out, provisions of paragraph 12.6.1 and 12.6.2 shall be followed.
12.8 Painting and Other Work on Towers:
12.8.1 The work shall be carried out as per provisions of paragraphs 12.6 to 12.11 in so far as applicable, except that earths and pennants may be removed in sequence as the work proceeds down the tower.
12.8.2 The following additional precautions shall be observed in case of towers carrying live conductors :-
  • No employee shall climb above the anti-climbing device unless under observation by a safety man;
  • No tool above 30.48 cm (12 inches) in length shall be taken up the tower;
  • In so far as practicable, the work shall be carried out from within the body of the tower;
  • No employee shall work in a manner that his access way or arms or any tool extend beyond the limitations fixed under paragraph 11.4.4 and 11.4.5 respectively.
12.9 Washing of Live Insulators:
12.9.1 Work shall be carried out under special authorizations of the Control Engineer (Transmission and/or Distribution) and under the personal supervision of the Senior Authorised Person.
12.9.2 The water used shall normally have a specific resistance of not less than 2000 Ohms/Cm3, and samples shall be submitted annually to an approved testing laboratory.
12.9.3 The jets used shall be such that the water breaks into a spray before reaching the insulator.
12.9.4 The nozzle of the hose shall be connected to earth by an earthing lead not less than 0.645 sq. cm (0.1 sq. inch) in cross-section and the operator shall wear rubber gloves.
12.9.5 The operator shall be not less than 6.096 meters (20 ft.) away from the insulator being washed and care shall be taken in observing this to see that no other live insulator or live conductor at a lesser distance is inadvertently sprayed.
12.10 Testing of Insulators on Live Lines:
12.10.1 The work shall be carried out under a sanction for test to he issued by the Control Engineer (Transmission and/or Distribution) and work shall be carried out under the direct supervision of the Senior Authorised Person.
12.10.2 Testing shall be carried out only under suitable weather conditions. It shall not be carried out if the humidity is above 70 percent shall be discontinued if a thunder storm approaches.
12.10.3 Not more than 3 men shall climb the tower, one of these shall be responsible for seeing that the others maintain the necessary clearance from live conductors. The second man shall apply the testing apparatus, the third man shall take observation either at conductor level or ground level.
12.10.4 No tool other than an approved testing apparatus shall be taken up the tower.
12.10.5 If a line trips out or is found to be dead while such work is known to be in progress, the Control Engineer (Transmission and/or Distribution) shall be immediately informed and the line shall not be closed until the Control Engineer has been in communication with the person in charge of the work.
12.11 Telephone Line and Carrier Current:
12.11.1 The following general precautions shall be observed :-
  • Every communication line supported on poles carrying high voltage or extra high voltage electric lines shall, for the purposes of working thereon, be deemed to be a high voltage electric line and every person working on such communication line shall take similar precautions to those provided under para 12.4:
  • When working on the telephone lines supported on poles carrying medium and low voltage lines, the employees shall avoid contact with the supply line and grounded metal fixtures in the case of wood pole.
  • Earths shall be installed on both sides of the point of work, when repairing a break in telephone lines.
12.11.2 The following precautions shall be observed in connection with the use of portable telephone :-
  • Telephone test sets shall not be used on circuits known to carry excessive voltages unless specially designed for this purpose.
  • Operators for telephone systems shall stand on an insulated platform or rubber insulation mat while speaking to protect himself against leakage of induced voltage on communication equipment.
  • The operator, while speaking, shall not touch any metal frame of the telephone equipment to avoid the risk of electric shock due to leakage or discharge of high induced voltage.
Note :- The telephone apparatus is specially hazardous when transmission lines are being energized or reenergized, and during electrical storms, and should not be left on.