1[OVERHEAD LINES, UNDER GROUND CABLES AND GENERATING STATIONS]
Rulle-74: Material and strength:
(1) All conductors of overhead lines other than those specified in sub-rule (1) of rule 86 shall have a breaking strength of not less than 350 kg.
(2) Where the voltage is low and the span is of less than 15 metres and is on the owner’s or consumer’s premises, a conductor having an actual breaking strength of not less than 150 kg may be used.
Rule-75: Joints:
Joints between conductors of overhead lines shall be mechanically and electrically secure under the conditions of operation. The ultimate strength of the joint shall not be less than 95 per cent of that of the conductor, and the electrical conductivity not less than that of the conductor.
2[Provided that no conductor of an overhead line shall have more than two joints in a span.]
Rule-76: Maximum stresses: Factors of safety:
(1)
(a) The owner of every overhead line shall ensure that it has the following minimum factors of safety:
(i) For metal supports ………. 1.5
(ii) For mechanically processed concrete supports ………. 2.0
(iii) For hand-moulded concrete supports ………. 2.5
(iv) For wood supports ………. 3.0
The minimum factors of safety shall be based on such load as would cause failure of the support to perform its function (assuming that the foundation and other components of the structure are intact). The aforesaid load shall be:
(i) Equivalent to the yield point stress or the modulus of rupture, as the case may be, for supports subject to bending and vertical loads,
(ii) The crippling load for supports used struts.
The said owner shall also ensure that the strength of the supports in the direction of the line is not less than one-fourth of the strength required in the direction transverse to the line.
Provided that in the case of latticed steel or other compound structures, factors of safety shall not be less than 1.5 under such broken wire conditions as may be specified by the State Government in this behalf.
(b) The minimum factor of safety for stay-wires, guard-wires or bearer wires shall be 2.5 based on the ultimate tensile strength of the wire.
(c) The minimum factor of safety for conductors shall be 2, based on their ultimate tensile strength. In addition, the conductor’s tension at 320C, without external load, shall not exceed the following percentages of the ultimate tensile strength of the conductor:
Initial unloaded tension ………. 35 per cent.
Final unloaded tension ………. 25 per cent.
Provided that in the case of conductors having a cross section of a generally triangular shape, such as conductors composed of 3-wires, the final unloaded tension at 32’C shall not exceed 30 per cent of the ultimate tensile strength of such conductor.
(2) For the purpose of calculating the factors of safety prescribed in sub-rule (l):
(a) The maximum wind pressure shall be such as the State Government may specify in each case;
(b) For cylindrical bodies the effective area shall be taken as two-thirds of the projected area exposed to wind pressure;
(c) For latticed steel or other compound structures the wind pressure on the lee side members shall be taken as one-half of the wind pressure on the windward side members and the factors of safety shall be calculated on the crippling load of struts and upon the elastic limit of tension members;
(d) The maximum and minimum temperatures shall be such as the State Government may specify in each case.
(3) Notwithstanding anything contained in sub-rules (1) and (2), in localities where overhead lines are liable to accumulations of ice or snow the State Government may, by order in writing, specify the loading conditions for the purpose of calculating the factor of safety.
Rule-77: Clearance above ground of the lowest conductor:
(1) No conductor of an overhead line, including service lines, erected across a street shall at any part thereof be at a height of less than:
(a) For low and medium voltage lines ………. 5.8 metres
(b) For high voltage lines ………. 6.1 metres
(2) No conductor of an overhead line, including service lines, erected along any street shall at any part thereof be at a height less than:
(a) For low and medium voltage lines ………. 5.5 metres
(b) For high voltage lines ………. 5.8 metres
(3) No conductor of in overhead line including service lines, erected elsewhere than along or across any street shall be at a height less than:
(a) For low, medium and high voltages lines up to
and including 11,000 volts, if bare ………. 4.6 metres
(b) For low, medium and high voltage lines up to
and including 11,000 volts, if insulated ………. 4.0 metres
(c) For high voltage lines above 11,000 volts ………. 5.2 metres
(4) For extra-high voltage lines the clearance above ground shall not be less than 5.2 metres plus 0.3 metre for every 33,000 volts or part thereof by which the voltage of the line exceeds 33,000 volts.
Provided that the minimum clearance along or across any street shall not be less than 6.1 metres.
Rule-78: Clearance between conductors and trolley wires:
(l) 3[No conductor of an overhead line crossing a tramway or trolley bus route using trolley wires shall have less than the following clearances above and trolley wire:
(a) Low and medium voltage lines ………. 1.2 metres.
Provided that where an insulated conductor suspended from a bearer wire crosses over a trolley wire the minimum clearance for such insulated conductor shall be 0.6 metre.
(b) High voltage lines up to and including 11,000 volts ………. 1.8 metres.
(c) High voltage lines above 11,000 volts ………. 2.5 metres.
(d) Extra-high voltage lines ………. 3.0 metres
(2) 4[In any case of a crossing referred to in sub-rule (1), whoever lays his line later in time, shall provide the clearance between his own line and the line which will be crossed in accordance with the provisions of said sub-rule.
Provided that if the later entrant is the owner of the lower line and is not able to provide adequate clearance, he should bear the cost of modification of the upper line so as to comply with this rule.]
Rule-79: Clearances from buildings of low and medium voltage lines and service lines:
(1) Where a low or medium voltage, overhead line passes above or adjacent to or terminates on any building, the following minimum clearances from any accessible point, on the basis of maximum sag, shall be observed:
(a) For any flat roof, open balcony, veranda roof and lean-to-roof:
(i) When the line passes above the building a vertical clearance of 2.5 metres from the highest point, and
(ii) When the line passes adjacent to the building a horizontal clearance of 1.2 metres from the nearest point, and
(b) For pitched roof:
(i) When the line passes above the building a vertical clearance of 2.5 metres immediately under the lines, and
(ii) When the line passes adjacent to the building a horizontal clearance of 1.2 metres.
(2) Any conductor so situated as to have a clearance less than that specified in sub-rule (1) shall be adequately insulated and shall be attached at suitable intervals to a bare earthed bearer wire having a breaking strength of not less than 350 kg.
(3) The horizontal clearance shall be measured when the line is at a maximum deflection from the vertical due to wind pressure.
5[Explanation- For the purpose of this rule, expression “building” shall be deemed to include any structure, whether permanent or temporary]
Rulle-80: Clearances from buildings of high and extra-high voltage lines:
(1) Where a high or extra-high voltage overhead line passes above or adjacent to any building or part of a building it shall have on the basis of maximum sag a vertical clearance above the highest part of the building immediately under such line, of not less than:
(a) For high voltage lines up to and including 33,000 volts 3.7 metres
(b) For extra-high voltage lines 3.7 metres plus 0.30 metre for every additional 33,000 volts or part thereof.
(2) The horizontal clearance between the nearest conductor and any part of such building shall, on the basis of maximum deflection due to wind pressure, be not less than-
(a) For high voltage lines up to and including 11,000 volts 1.2 metres
(b) For high voltage lines above 11,000 volts and up to and including 33,000 volts 2.0 metres
(c) For extra-high voltage lines 2.0 metres plus 0.3 metre for every additional 33,000 volts for part thereof.
6[Explanation- For the purpose of this rule expression “building” shall be deemed to include any structure, whether permanent or temporary]
Rule-81: Conductors at different voltages on same supports:
Where conductors forming parts of systems at different voltages are erected on the same supports, the owner shall make adequate provision to guard against danger to linesman and others from the lower voltage system being charged above its normal working voltage by leakage from or contact with the higher voltage system and the methods of construction and the clearances between the conductors of the two systems shall be subject to the prior approval of the Inspector.
Rule-82: Erection of or alternation to buildings, structures, flood banks and elevation of roads
(1) If at any time subsequent to the erection of an overhead line (whether covered with insulating material or bare), any person proposes to erect a new building or structure or flood bank or to raise any road level or to carry out any other type of work whether permanent or temporary or to make in or upon any building or structure of flood bank or road, any permanent or temporary addition or alternation, he and the contractor whom he employs to carry out the erection, addition or alteration, shall if such work, building, structure, flood bank, road or additions and alterations thereto, would, during or after the construction result in contravention of any of the provisions of rule 77, 79 or 80, give notice in writing of his intention to the supplier and to the Inspector and shall furnish therewith a scale drawing showing the proposed building, structure, flood bank road, any addition or alteration and scaffolding required during the construction.
(2)
(a) On receipt of the notice referred to in sub-rule (1) or otherwise, the supplier shall examine whether the line under reference was lawfully laid and whether the person was liable to pay the cost of alteration and if so, send a notice without undue delay, to such person together with an estimate of the cost of the expenditure likely to be incurred to so after the overhead line and require him to deposit, within 30 days of the receipt of the notice with the supplier, the amount of the estimated cost.
(b) If the person referred to in sub-rule (1) disputes the suppliers estimated cost of alteration of the overhead line or even the responsibility to pay such cost the dispute may be referred to the Inspector by either of the parties whereupon the same shall be decided by the Inspector.
(3) No work upon such building, structure, flood bank, road and addition or alternation thereto shall be commenced or continued until the Inspector has certified that the provisions of rule 77, 79 or 80 are not likely to be contravened either during or after the aforesaid construction.
Provided that the Inspector may, if he is satisfied that the overhead line has been so guarded as to secure the protection of persons or property from injury, or risk of injury, permit the work to be executed prior to the alteration of the overhead line or in the case of temporary addition or alteration, without alteration of the overhead line.
(4) On receipt of the deposit, the supplier shall after the overhead line within one month of the date of deposit or within such longer period as the Inspector may allow and ensure that it shall not contravene the provisions of rule 77, 79 or 80 either during or after such construction.
(5) In the absence of an agreement to the contrary between the parties concerned, the cost of such alteration of the overhead line laid down shall be estimated on the following basis, namely:
(a) The cost of additional material used on the alteration giving due credit for the depreciated cost of the material which would be available from the existing line;
(b) The wages of Labour employed in affecting the alteration;
(c) Supervision charges to the extent of 15 per cent of the wages mentioned in clause (b); and
(d) Any charges incurred by the supplier in complying with the provisions of section 16 of the Act in respect of such alterations.
(6) Where the estimated cost of the alteration of the overhead line is not deposited the supplier shall be considered as an aggrieved party for the purpose of this rule.
Rule-82A: 7[Transporting and Storing of material near overhead lines:
(1) No rods, pipes or similar materials shall be taken below or in the vicinity of any bare overhead conductors or lines if they are likely to infringe the provisions for clearances under rules 79 and 80, unless such materials are transported under the direct supervision of a competent person authorised in this behalf by the owner of such overhead conductors or lines.
(2) Under no circumstances rods, pipes or other similar materials shall be brought within the flash over distance of bare live conductors or lines; and
(3) No material or earth work or agricultural produce shall be dumped or stored or trees grown below or in the vicinity of bare overhead conductor’s lines so as to reduce the requisite safety clearances specified under rules 79 and 80.]
Rule-83: Clearances: General:
For the purpose of computing the vertical clearance of an overhead line, the maximum sag of any conductor shall be calculated on the basis of the maximum sag in still air and the maximum temperature as specified by the State Government under rule 76(2) (d). Similarly, for the purpose of computing any horizontal clearance of an overhead line the maximum deflection of any conductor shall be calculated on the basis of the wind pressure specified by the State Government under rule 76(2)(a) or may be taken as 350, whichever is greater.
Rule-84: Routes: Proximity to aerodromes:
Overhead lines shall not be erected in the vicinity of aerodromes until the aerodrome authorities have approved in writing the route of the proposed lines.
Rule-85: Maximum interval between supports:
All conductors shall be attached to supports at intervals not exceeding the safe limits based on the ultimate tensile strength of the conductor and the factor of safety prescribed in rule 76.
Provided that in the case of overhead lines carrying low or medium voltage conductors, when erected in, over, along or across any street, the interval shall not, without the consent in writing of the Inspector, exceed 65 metres.
Rule-86: Conditions to apply where telecommunication lines and power lines are carried on same supports:
(1) Every overhead telecommunication line erected on supports carrying a power line shall consist of conductors each having a breaking strength of not less than 270 kg.
(2) Every telephone used on a telecommunication line erected on supports carrying a power line shall be suitably guarded against lightning and shall be protected by cut-outs.
(3) Where a telecommunication line is erected on supports carrying a high or extra-high voltage power line arrangement shall be made to safeguard any person using the telephone against injury resulting from contact, leakage or induction between such power and telecommunication lines.
Rule-87: Lines crossing or approaching each other:
(1) Where an overhead line crosses or is in proximity to any telecommunication line, either the owner of the overhead line or the telecommunication line, whoever lays his line later, shall arrange to provide for protective devices or guarding arrangements, in a manner laid down in the Code of Practice or the guidelines prepared by the Power and Telecommunication Coordination Committee and subject to the provisions of the following sub-rules:
(2) When it is intended to erect a telecommunication line or an overhead line which will cross or be in proximity to an overhead line or a telecommunication line, as the case may be, the person proposing to erect such line shall give one month’s notice of his intention so to do along with the relevant details of protection and drawings to the owner of the existing line.
(3) 8[Where an overhead line crosses or is in proximity to another overhead line, guarding arrangements shall be provided so as to guard against the possibility of their coming into contact with each other.
Where an overhead line crosses another overhead line, clearances shall be as under:
9[Minimum clearances in metres between lines crossing each other.
Sl. No.
|
Nominal System Voltage
|
11-66 kV
|
110-132 kV
|
220 kV
|
400 kV
|
800 kV
|
1
|
Low & Medium
|
2.44
|
3.05
|
4.58
|
5.49
|
7.94
|
2
|
11-66 kV
|
2.44
|
3.05
|
4.58
|
5.49
|
7.94
|
3
|
110-132 kV
|
3.05
|
3.05
|
4.58
|
5.49
|
7.94
|
4
|
220 kV
|
4.58
|
4.58
|
4.58
|
5.49
|
7.94
|
5
|
400 kV
|
5.49
|
5.49
|
5.49
|
5.49
|
7.94
|
6
|
800 kV
|
7.94
|
7.94
|
7.94
|
7.94
|
7.94
|
Provided that no guarding are required when an extra high voltage line crosses over another extra-high voltage, high voltage, medium or low voltage line or a road or a tram subject to the condition that adequate clearances are provided between the lowest conductor of the extra-high voltage line and the top most conductor of the overhead line crossing underneath the extra-high voltage line and the clearances as stipulated in rule 77 from the topmost surface of the road is maintained.]
(4) A person erecting or proposing to erect a line which may cross or be in proximity with an existing line, may normally provide guarding arrangements on his own line or require the owner of the other overhead line to provide guarding arrangements as referred to in sub-rule, (3).
(5) In all cases referred to in the preceding sub-rules the expenses of providing the guarding arrangements or protective devices shall be borne by the person whose line was last erected.
(6) Where two lines cross, the crossing shall be made as nearly at right angles the nature of the case admits and as near the support of the line as practicable, and the support of the lower line shall not be erected below the upper line.
(7) The guarding arrangements shall ordinarily be carried out by the owner of the supports on which it is made and he shall be responsible for its efficient Maintenance.
(8) All work required to be done by or under this rule shall be carried out to the satisfaction of the Inspector.
Rule-88: Guarding:
(1) Where guarding is required under these rules the provisions of sub-rules (2) to (4) shall apply.
(2) Every guard-wire shall be connected with earth at each point at which its electrical continuity is broken.
(3) Every guard-wire shall have an actual breaking strength of not less than 635 kg and if made of iron or steel, shall be galvanised.
(4) Every guard-wire of cross-connected system of guard-wires shall have sufficient current carrying capacity to ensure the rendering dead, without risk of fusing of ground-wire or wires till the contact of any live wires has been removed.
(5) Lines crossing trolley-wires In the case of a crossing over a trolley-wire the guarding shall fulfil the following conditions, namely:
(a) Where there is only one trolley-wire, two guard-wires shall be erected as in diagram (i);
(b) Where there are two trolley-wires and the distance between them does not exceed 40 cm, two guard-wires shall be erected as in diagram (ii);
(c) Where there are two trolley wires and the distance between them exceeds 40 cm but does not exceed 1.2 metres, three guard-wires shall be erected as in diagram (iii);
(d) Where there are two trolley-wires and the distance between them exceeds 1.2 metres, each trolley-wire shall be separately guarded as in diagram (iv);
(e) The rise of the trolley boom shall be so limited that the trolley leaves the trolley-wire, it shall not foul the guard-wires; and
(f) Where a telegraph-line is liable to fall or be blown down upon an arm, stay-wire or span-wire and so slide down upon a trolley-wire, guard hooks shall be provided to prevent such sliding.
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Rule-89: Service-lines from Overhead lines:
No Service-line or tapping shall be taken off an overhead line except at a point of support. 10[Provided that the number of tapings per conductor shall not be more than four in case of low and medium voltage connections.]
Rule-90: Earthing:
(1) All metal supports and all reinforced and pressurised cement concrete supports of overhead lines and metallic fittings attached thereto shall be permanently and efficiently earthed. For this purpose a continuous earth wire shall be provided and securely fastened to each pole and connected with earth ordinarily at three points in every km., the spacing between the points being as nearly equidistance as possible. Alternatively, each support and the metallic fitting attached thereto shall be efficiently earthed.
(IA) 11[Metallic bearer wire used for supporting insulated wire of low and medium voltage overhead service lines shall be efficiently earthed or insulated.]
(2) Each stay-wire shall be similarly earthed unless insulator has been placed in it at a height not less than 3.0 metres from the ground.
Rule-91: Safety and protective devices:
(1) Every overhead line, (not being suspended from a dead bearer wire and not being covered with insulating material and not being a trolley-wire) erected over any part of street or other public place or in any factory or mine or on any consumers’ premises shall be protected with a device approved by the Inspector for rendering the line electrically harmless in case it breaks.
(2) An Inspector may by notice in writing require the owner of any such overhead line wherever it may be erected to protect it in the manner specified in sub-rule-(l).
(3) 12[The owner of every high and extra-high voltage overhead line shall make adequate arrangements to the satisfaction of the Inspector to prevent unauthorised persons from ascending any of the supports of such overhead lines which can be easily climbed upon without the help of a ladder or special appliances. Rails reinforced cement concrete poles and pre-stressed cement concrete poles without steps, tubular poles, wooden supports without steps, I sections and channels shall be deemed as supports which cannot be easily climbed upon for the purpose of this rule.]
Rule-92: Protection against lightning:
(1) The owner of every overhead line 13[sub-station or generating station] which is so exposed as to be liable to injury from lightning shall adopt efficient means for diverting to earth any electrical surges due to lightning.
(2) 14[The earthing lead for any lightning arrestor shall not pass through any iron or steel pipe, but shall be taken as directly as possible from the lightning- arrestor to a separate earth electrode and/or junction of the earth mat already provided for the high and extra-high voltage sub-station subject to the avoidance of bends wherever practicable.
Note: A vertical ground electrode shall be connected to this junction of the earth mat.]
Rule-93: Unused overhead lines:
(1) Where an overhead line ceases to be used as an electric supply line, the owner shall maintain it in a safe mechanical condition in accordance with rule 76 or shall remove it.
(2) Where any overhead line ceases to be used as an electric supply line, an Inspector may, by a notice in writing served on the owner, require him to maintain it in a safe mechanical condition or to remove it within fifteen days of the receipt of the notice.
1. Subs. by GSR 466, Date. 18.7.1991, with effect from: 17.8.1991.
2. Ins. by GSR 730, Date. 7.9.1989, with effect from: 30.9.1989.
3. Rule 78 renumbered as sub-rule (1) by GSR 528, Date. 11.7.1986, with effect from: 19.7.1986.
4. Sub-rule (2) ins. by GSR 528, Date. 11.7.1986, with effect from: 19.7.1986.
5. Added by GSR 844, Date. 31.7.1985, with effect from: 7.9.1985.
6. Added by GSR 844, Date. 31.7.1985. with effect from: 7.9.1985.
7. Ins. by GSR 358, Date. 30.4.1987, with effect from: 9.5.1987.
8. Subs. by GSR 256, Date. 28.2.1983, with effect from: 26.3.1983.
9. Subs. by GSR 466, Date. 18.7.1991, with effect from: 17.8.1991.
10. Added by GSR 45, Date. 1.1.1993, with effect from: 23.1.1993.
11. Subs. by GSR 732, Date. 18.6.1985, with effect from: 3.8.1985.
12. Ins. by GSR 466, Date. 18.7.1991, with effect from: 17.8.1991.
13. Ins. by GSR 466, Date. 18.7.1991, with effect from: 17.8.1991.
14. Subs. by GSR 1050, Date. 9.11.1985.
