cte extract

CONFIDENTIAL

For Official Use Only

INDIAN STANDARDS AND INDIAN ELECTRICITY RULES EXTRACTS

CHIEF TECHNICAL EXAMINER’S ORGANISATION NEW DELHI

R. Sharma (BSNL Electrical Zone Patna) 2

INDEX INTERNAL S.NO IS / IE RULES SUBJECT REFER

-ENCE CPWD SPEC. PAGE

PAGE NO

1. IS 732-1963 Code of practice for Electrical Wiring

installations (system Voltage not exceeding 650 Volts)

3 1

2. IS 732-1963 Code of practice for Electrical Wiring

installations (system Voltage not exceeding 650 Volts)

3 2

3. IE RULE 1956 / 50 Medium pressure wiring 5 2

4. IE RULE 1956 / 51 Regarding Medium and High pressure wiring 5 2

5. IE RULE 1956 / 32(1)(2)

Identification of earthed and Neutral conductors. 6 2-3

6. IE RULE 1956 / 51(1) Fixed type metallic boxes 7 3

7. IS 375-1963 ® Marking and arrangement for switch-gear bus-

bars, main connections and auxiliary wiring 23 3

8. IE RULE 1956 / 33 Earthed termination on consumer premises. 27 3

9. IE RULE 1956 / 33 Connection with Earth. 27 3-4

10. IE RULE 1956 / 33 Connection with Earth. 27 4

11. IS 347 / 1952 Varnish Shellac for general purposes 28 4-5

12. IS2309 / 1969 Code of practice for the protection of buildings and allied structures against lightning.

31 4-6

13. IS RULE 1956 Safety procedure. 40 6

14. IS CODE 5216 / 1969 Guide for safety procedures and practice in

electrical works. 40 7-8


INDEX EXTERNAL S.No IS / IE RULES SUBJECT REFER

-ENCE CPWD SPEC. PAGE

P. NO

1. IS 1954 (Part-I)1976

For working voltages upto and including 1100 Volts. 3 1-2

2. IS 1954(Part-II)1967

For working Voltage from 3.3 KV up to and including 11 KV.

3 2-5

3. IS 692-1973 Paper insulated lead sheathed cables for electricity supply.

3 5-6

4. IS 732-1963 Code of practice for electrical wiring installations (System voltage not exceeding 650 Volts).

3 6-7

5. IS 3961 (PART-II)1967

Paper insulated lead sheathed cables. 3 7

6. IS 3961 (PART-II)1967

PVC insulated and PVC sheathed heavy duty cables. 3 7

7. IS 5819--1970 Recommended short circuit rating of high voltage PVC cables.

3 8-9

8. IS 1255-1967 Code of practice for installation and maintenance of paper insulated power cables ( up to & including 53 KV).

4-6 9-10

9. IS 1255-1967 --do—Section II 10 10-11 10. IS 2713 - 1964 Tubular steel poles for O.H. Lines. 10 11-13 11. IS 705-1970 Reinforced concrete poles for OH power &

Telecommunication lnes. 10 13-15

12. IS 876-1970 Wood poles for O.H power and Telecommunications lnes.

10 15-16

13. IS 1678-1960 Prestresssed concrete poles for OH power, traction and Telecommunications lines.

10 16-18

14. IE RULE 1956/76 Strength of Supports. 10 19 15. IE RULE 1956/90 Earthing of poles. 10 19 16. IS 2141-1979 Galvanized stay strand. 11 19-22 17. IS 1445-1966 Porcelain Insulators for O.H. power lines (below 1000

V) 11 17-22

18. IS 731/1971 Porcelain Insulators for overhead lines (3.3 KV and below).

11 22-35

19. IE RULE 88 Repairing Guard Wire. 11 35 20. IS 398-1961 Hard drawn stranded "A" and steel-cord "A" conductors

for over head power transmission purpose. 11 35

21. -do-(Part 8) ---do-- 11 36-37 22. IS 3070-1974

PART(I) Non-Linear resistor types lighting arrestors. 11 38-42

23. IS 3070-1966 Expulsion type Lighting Arrestors. 11 42-44


(PART II) 24. IE RULE 92 Regarding Earthing the lightning arrestors. 12 45 25. IE RULE 77 Clearance above ground of the lowest conductor. 12 45-46 26. IE RULE 79 Clearance from building of low and medium voltage

lines and service lines. 12 46

27. --do-- 80 --do—of high & extra high . 12 47 28. --do—81 Conductors at different voltage on same supports. 12 47 29. --do-- 86 Conditions to supply where Telecommunications lines

and power lines are carried on same supports. 12 47

30. --do—87 Lines crossing or approaching each other. 12 48 31. IS 2551-1963 Danger Notice Plates. 16 48 32. IS 270-1962 Galvanized steel barbed wire for fencing. 16 49-51 33. IE RULE 76 Guard of service Line. 16 51 34. IS 1255-1967 Care of practice for installation and maintenance of paper

insulated power cables (up to and including 33 KV Section 11.7).

26 51

35. IS 429-1954 Methods for testing weights and uniformity of coating on Galvanized iron and steel wires and steel sheets.

52-53


INTERNAL IS 732-1963 Electrical wiring installation (system voltage not exceeding 650 Volts) Layout of Wiring ’Power’ and heating, Sub-Circuits shall be kept separate and distinct from ’lighting’ and ’fan’ Sub-Circuits. All wirings shall be done on the distribution system with main and branch distribution boards at convenient physical and electrical load centre and without isolated fuses. All types of wiring, whether concealed or unconcealed should be capable of easy inspection. The unconcealed wiring when run along the walls should be as near the ceiling as possible. In all types of wirings, due consideration shall be give for neatness and good appearance. 3.5.2. Balancing of circuits in three wire of polyphase installation shall be as enclosed in earthing metal of incombustible insulating material that it is not possible to have ready access to them unless the points between which a voltage exceeding 250 Volts may be precast are 2 Mt. or more apart, in which case means of access shall be marked to indicate the voltage present. 3.6 Position of wiring run and points:-

All runs of wiring and the exact positions of all points and switch boxes shall be first marked on the plan of the building or on the building itself and approved by the Engineer-in-Charge or the owner before actual commencement of work.

3.7 Voltage and frequency supply:-

All current consuming devices shall be suitable for the voltage and frequency of supply to which the are to be connected. 3.8 Drawings:-

On completion of the work, a wiring diagram shall be prepared and submitted to the

Engineer-in-Charge or the owner. All wiring diagrams shall indicated clearly the main switch board, the runs of various mains and their controls. All circuits shall be clearly indicated and numbered in the wiring diagrams and all points shall be given the same number as the circuit to which they are electrically connected. I.S 732-1963

Conventional symbols for electrical Installation:

These have clearly been shown in appendix D of the specification, which are much more sufficient and clearly shown.

Electrical Wiring Installation (System voltage not exceeding 650 Volts.

The installation shall be designed as to enable equipment to work with a variation in the declared supply voltage of + 5 percent in respect of low voltage and medium voltage and 12.5 percent in respect of high voltage.


Medium pressure wiring: I.E Rule 50

The supply of energy to each motor or group of motors or other apparatus meant for operating one particular machine, is controlled by a suitable linked switch or a circuit breaker or an emergency tripping device with manual reset of requisite capacity placed in such a portion as to be adjacent to the motor or a group of motors or other apparatus readily accessible to and easily operated by the person in charge and so connected in the circuit of that but its means all supply of energy can be cut off from the motor or a group of motors or apparatus and from any regulating switch, resistance or other devices associated there with.

I.E. Rule 51 1 (a) All conductors (other than those of O.H. Lines) shall be completely enclosed in mechanically strong metal casing or metallic covering which is electrically and mechanically continuous and adequately protected against mechanical damage unless the said conductors are accessible only to an authorised person or are installed and protected to the satisfaction of the Inspector as to prevent danger. I.E. Rule 32 (I) An indication of a permanent nature shall be provided by the owner of the earthed or earthed neutral conductor or the conductor which is to be connected there in, to enable such conductor to be distinguished from any line conductor. I.E. Rule 32 (ii) No cutout link or switch other than a linked switch arranged to operate simultaneously on the earthed or earthed neutral conductor and live conductors shall be inserted or remain or remain inserted in any earthed or earthed neutral conductors of a two wire system or in any earthed neutral conductor or a multi-wire system or in any conductor connected thereto with the following exceptions: a) A link for testing purposes or b) A switch for use in controlling a generator or transformer. I.E. Rule 51 (1) D (ii) If there are any attachments or bare connections at the back of the switch board, the space (if any) behind the switch board shall be either less then 0.229 Mtr. (9 inches) or more than 0.762 Mtr. (30 inches) in with, measured from the farthest outstanding part of any attachment or conductor. If the space behind the switch board exceeds 0.762 Mtr. (30 inches) in with, there shall be a passage way from either and of the switch board clear to a height of 1.829 Mtr (6 Feet). Switch gear, bus-bars. Main connections and Auxiliary Wiring, marking arrangements for (revised).


I.S. 375-1963

Bus-bar markings: A sufficient brief has been given in the specifications itself which is more sufficient as required.

I.E. Rule 33. The supplier shall provide and maintain on the consumers premises for the consumer’s use a suitable earthed terminal in an accessible position at or near the point of commencement of supply. Provided that in case of medium, high or extra high voltage installation, the consumer shall in addition to aforementioned earthing arrangement provide his own earthing system with an independent electrode. I.E. Rule-61 The following provisions shall apply to the connection with earth of system at low voltage in cases where the voltage normally exceeds 125 volts and of systems at medium voltage. (a) The neutral conductor of a three phase four wire system and the middle conductor of a two

phase, three wire system shall earthed by not less then two separate and distinct connections with earthed both at the generating station and at the sub-station, it may also be earthed at one or more points along the distribution system or service line in addition to any connection with earth which may be at the consumer’s premises.

Connection with earth, I.E. Rule-67

The following provision shall apply to the connections with earth of three phase system for use at high or extra high voltage.

In the case of star connected systems with earthed neutral or delta connected systems with earthed artificial neutral point.

(a) The neutral point shall be earthed by not less than two separate and distinct connections

with earth each having its own electrode at the generating station and at the sub-station and may be earthed at any other point provided that no interference of any description is caused by such earthing.

(b) In the event of an appreciable harmonious current flowing in the neutral connection so as to cause interference with communication circuits, the generator or transformer neutral shall be earthen through a suitable impedance.

Varnish, shellac, for General purposes I.S. 347-1952 Shellac solutions: Weigh accurately a quantity of the material equivalent to 10.00 g. of dry shellac and dilute to 100 ml. With could 95 percent (by volume) ethyl alcohol (IS 321- 1952 filled the


solution in an ordinary funnel using a medium grade filtrate and then collect 5 ml, or more of the clear filtrate for the test. Protection of building and allied structures against lighting (First Revision). I.S. 2309-1969

C.I. (General): While every structure, theoretically has a chance of being struck by lightning, the degree of this chance varies depending upon a number of associated factors such as lightning incidences, surroundings, types of terrain etc. For a certain class of structures which form a source of danger such as the housing explosive factories or stores or flamable materials, complete protection against lightning shall be provided. In other cases covered by this code it may be necessary to decide whether this protection is called for, under a given set of circumstances. C. 1 – 2 There would be other factors which are not capable of such assessment in relative terms. Yet these may over-ride all other considerations for exchange a requirement that there should be no avoidable risk to life or the over-whelming importance or value of the structure. In such cases, however, it may be desirable to make a decision on an assessment in terms of the chances of the structure being struck and of the consequences if it is struck. For this various factors denoting chances of the structure being struck by lightning and the total effect of these factors shall be assessed. As an aid to making judgment a set of indices is given for the various which are capable of being assessed. C. 1 - 3 Structures containing explosives or flammable material are excluded from this method of assessment. Factors Capable of Assessment: (1) Usage of structure: The lightning hazard to human being within a structure or building is a very important factor in deciding how for to go in providing lightning protection schools, hospitals, factories, railway stations etc. are places where a large number of people congregate and, therefore, are structures of greater importance than small building and houses. (2) Type of Construction:

The type of construction of the structure has a large influence upon the extent of protection. A steel framed building to some extent is self protecting and may not require any additional protection, while brick building or building with thatched roof require greater degree of protection. (3) Contents or consequential effects:


In addition to direct loss due to destruction of buildings by lightning, fire, resulting from lightning, killing of livestock etc., there may be indirect losses which some- times accompany the destruction of buildings and their contests.

(4) Degree of Isolation:

The relative exposure of a particular building will be an element in determining whether the expense of protection is warranted. In closely built-up towns and cities the hazard is not as great as in the open country. In the latter farm barns in many cases are the most prominent targets for lightning in a large area. (5) Type of terrain:

In hilly or mountainous area a building is more susceptible to damage than a building in

plains and flat terrain. In hilly areas itself, a building upon high ground is usually subject to greater hazard than the one in a valley or other wise sheltered area.

(6) Height of structures:

Height of structure is an important factor for the purpose of lightning protection. Taller structures are subject to greater hazards than smaller structure and, therefore, lightning protection is more desirable in tall structures.

(7) Lightning prevalence:

The need for protection varies from place to place, although not necessarily in direct proportion to the thunder storm frequency. I.E Rule 1965 (Safety procedure) Safety procedure has been sufficiently detailed in the specifications. Guide for safety procedures and practices in electrical works I.S Code 5216-1969 In all electrical works, it is very necessary that certain elementary safety practices are observed. It has been found that a quite large number of accidents occur due to the neglect to these practices. 7.2 Fires and fire extinguishers:

In the event of fire on electrical mains or apparatus, the effective part shall immediately be completely isolated from its source of supply of electrical energy.


7.2.2 Fire extinguishers which are not insulated should never be employed in fighting fires near exposed live conductors. Only such fire extinguishers should be used on electrical main and apparatus which are marked as suitable for the purpose when using fire hose it should be ensured that the jet of water does not come into contact with live conductors.

7.2.3 It is dangerous to throw a steam of water a wet blanket or a stream from ordinary sodas

operated type extinguishers on live mains or apparatus. When found necessary to use them, have all the neighbouring mains or apparatus made dead. Carbon-di-oxide, carbon-tetra-chloride and other special type of extinguishers, sand or dry blanket may be used on live conductors and static apparatus.

7.3 Lightning:

Inadequate lightning of working areas is by itself a source of danger particularly when is undertaken at night. Never, therefore, allow any work in park or badly illuminated or ill ventilated places. 7.4 Safety posters:

Suitable safety posters in the form of "Do" and Don’t" instructions for the guidance of the working staff should be exhibited at important locations such as generating stations, receiving stations, sub-stations and factories.

Electric shock Chart:- It should be exhibited at important locations and the staff should also be trained so that in cases of any accident the preliminary first aid can be given to the person affected. Sufficiently, it has been mentioned in appendix C of the Specification on safety procedure which should also be kept in mind. EXTERNAL For working voltages up to and including 1000 volts. I.S 1554 Part – I – 1976 (1) Insulation:

The conductor shall be provided with PVC insulation applied by extrusion. (2) Thickness of insulation:

The average thickness of the insulation shall be not less than the nominal value (T I) specified in Table I . (3) Tolerance on thickness of insulation:


The smallest of the measured values of the thickness of the insulation shall not fall below

the nominal value (T I in mm) specified in Table 1 by more than 0.1 mm + 0.1 T. (4) Application of insulation:

The insulation shall be so applied that it fits closely on the conductor and it shall be easily possible to remove it without damage to the conductor. Inner Sheath ( Common Covering) 1. The laid up cores shall be provided with an inner sheath applied either by extrusion or by

wrapping. It shall be ensured that it is as circular as possible. 2. The inner sheath shall be so applied it fits closely on the laid up cores and it shall be

possible to remove it without damage to the insulation. 3. The values of thickness of inner sheath shall be given in table 3 single core cables shall

have no inner sheath.

Outer sheath. The outer sheath shall be applied by extrusions. It shall be applied. (a) Over the insulation in cases of unarmoured single core cables. (b) Over the inner sheath in case of unarmoured twin-three and Multi core cables, and (c) Over the armouring in case of armoured cables. 2. Colour of the outer sheathe shall be black.

Thickness of outer sheath

Unarmoured cables : The thickness of PVC outer sheath of unarmoured cables, determined by taking the average of a number of measurements shall be not less than the nominal value (Ts) specified in table 6 and the smallest of the measured values shall not fall be low the nominal value (Ts) specified in table 5 by more than 0.2mm + 0.2 ts. PVC insulated (Heavy duty ) electrical cables for working voltages from 3.3 KV upto and including 11 KV . I.S 1554 (Part-II)-1970 1. Composition of insulation :- The insulation shall consist of :- (a) Compound polying (chloride etc) (b) Suitable Co-polymers of which major constituent shall be vinyl chloride or (c) Mixtures of polying chloride and suitable co-polymers which have been suitable

compounded and crossed so as to comply with the requirements of this standard.


2. Thickness of insulation:- The average thickness of the insulation when measured in accordance with 10.8 shall be

not less than the standard value specified in table 1. 3. Tolerance in thickness of insulation :-

The smallest of the measured values of thickness of insulation tl ( in mm ) shall not fall below the standard values specified in table 1 by more than 0.1 +0.1 mm. 4. Insulation resistance:-

The insulation resistance of cable shall be such that specific insulation resistance of the material shall bot be less than the values given below at specified temperatures:-

26 D.C 3.3 x 10 13 ohm cm 60 D.C 3.45 x 10 13 ohm cm 70 D.C 1x10 11 ohm cm

Identification of cores:- The core identification shall be as follows:- Voltage Grade Method of identification 1.9/33 ) (a) Different colouring of the PVC insulation or 3.3/3.3) (b)Colored strips applied on the cores or 3.8/6.6) (c)By numerals (1,2,3) either by applying numbered strips applied in the cores or 6.6/6.6) (d) Colored strips applied on the cores or 6.35/11) (e) By numerals (1,2,3,) either by applying numbered strips or by

printing on the cores. Table 1 Thickness of insulation.

Thickness of Insulation for single core of three core cables rated voltage in KV or conductor 1.9/3.3 3.8/6.6 6.6/6.6 6.35/11

Nominal area

mm mm mm mm mm mm mm mm mm 25 2.3 3.6 4.2 4.2

35 2.3 3.6 4.2 4.2 50 2.3 3.6 4.2 4.2 70 2.3 3.6 4.2 4.2 95 2.3 3.6 4.2 4.2 120 2.3 3.6 4.2 4.2


150 2.3 3.6 4.2 4.2 185 2.3 3.6 4.2 4.2 225 2.3 3.6 4.2 4.2 240 2.3 3.6 4.2 4.2 300 2.5 3.6 4.2 4.2

400 2.7 3.6 4.2 4.2 500 3.0 3.6 4.2 4.2 625 3.4 3.6 4.2 4.2 800 3.4 3.6 4.2 4.2 1000 3.4 3.6 4.2 4.2 Inner Sheath In cables consisting of three cores, the individual cores shall be laid up and then be summarised by common covering applied either by extension or wrapping a filling material containing unvulcanized rubber or a thermoplastic material approved or plastic tape may be applied over the common covering when a wrapped common covering is employed, it shall be ensured that the circulating of the cable is maintained. The values of the thickness of the common covering and wrapping are given in table 2 single core cables shall have no inner sheath. Table –2 Thickness of inner sheath. Calculated dia over standards Cable cores. Thickness of inner sheath Over Up to & including mm mm mm -- 15 0.3 45 25 0.3 25 35 0.4 35 45 0.5 45 55 0.6 55 65 0.7 65 -- 0.7 Outer sheath 1. Extruded PVC outer sheath shall be provided over armour. The composition of the

sheathing compounds shall be as given in 1 (insulation). The colour of the PVC sheath shall be black.

2. Thickness of sheath:- The thickness of the sheath arrived out by taking the average of a number of measurements shall not be less than the standard value specified in table 4 when measured in accordance with 10.8.

Tolerance on the thickness of sheath, t s:-


The smallest of the measured values of thickness of sheath t s(in mm ) shall not fall below the

standard value specified in table 4 by more than 0.2 + 0.2 t smm:

Table 4 – Thickness of outer sheath. Calculated diamater of the sheath. Thickness of sheath Over Up to & including (1) (2) (3) mm mm mm -- 15 1.8 15 25 2.0 25 35 2.2 35 40 2.4 40 45 2.6 45. 50 2.8 50 55 3.0 55 60 3.2 60 65 3.4 65 70 3.6 70 75 3.8 75 80 4.0

Item 3 & 4 Lead sheathed cable I.S 692 – 1973 Lead or lead alloy sheath 1. After impregnation in accordance with I.E. the cable shall be covered with a metallic

sheath of lead alloy as specifically agreed to between the purchaser and the manufacturer. 2. The sheath shall be extruded directly on the cable in the form of a seamless tube. It shall

be reasonably close- fittings, impervious to moisture and free from in holes, joints mended places and other defects. Stop marks of the press are not considered as defects.

3. Thickness of sheath:- The minimum thickness of sheath when measured in accordance with 24.7 shall not fall below the nominal value specified in the relevant table by an amount not more than 5 percent + 0.1 mm. For this purpose, the calculated minimum value shall be rounded off to an accuracy of 0.0 mm.

Bedding

Armoured cables shall have a protective beading overload or lead alloy sheath. Unless extruded type is required by the purchaser, the bedding shall be of lapped type. Lapped Bedding:- Except in ’SL’ cables the lapped bedding shall consist of two paper tapes applied over compounded lead of lead alloy sheath without overlap but breaking joint, covered with a layer of compound and followed by


(a) Two layers of cotton tapes (b) One layer of cotton tapes followed by a layer of hessian tape. (c) Two layers of hessian tapes. (d) One layer of jute or (e) One or more layers of synthetic fibrous materials. Additional compound shall be applied over each Separate layer of natural fibrous materials. Test for the thickness of lead and leed alloy sheath A ring of in case of cables less than 12.5mm dia. Over sheath, a flattened circumferential strip shall be carefully cut from the sample. The samples shall be taken not less than 300 mm from the end of a factory length and it shall be determined by measurements at a sufficient number of points around the circumferences of the ring sample of along the surface of the flattened strip sample to ensure that the minimum thickness is included. The measurement shall be made with micrometer having one flat nose and either a flat rectangular nose 0.8 mm wide and 2.4 mm long or a ball nose, when the tests are made on the ring sample, the flat rectangular nose or that the ball nose shall be applied to the side of the ring . Electrical wiring installations (system voltage not exceeding 650 volts IS 732-1963 The installation shall be designed as to enable equipment to work with a variation in the declared supply voltage of + 5 percent in respect of low voltage and medium voltage and + 12.5 percent in respect of high voltage. Part- I Paper insulated lead sheathed cables I.S. 3961(Part-I-1967) 0.2 This standard has been drawn up to provide to the users general guidance for loading of

cables. The overloading of cables will reduce the life expectancy of the cable and at the same time under loading it will mean uneconomic utilization of its capacity. Depending upon the loading cycle met within practice, the installation engineer may decide the economic loading of cables.

0.3 The current ratings given in the standard have been drawn up on certain assumptions pertaining to soil conditions prevalent in this country, permissible temperature, rise of insulating materials, conductor etc. It is, however, to be expected that these conditions may be somewhat different in different places in a vast country like ours. In such cases the installation engineer is expected to keep in mind the loading conditions, the soil and atmospheric conditions in the area etc. before deciding on the choice of the proper size of the cable

PVC Insulated and PVC sheathed heavy duty cables.I.S 3961 (Part-II)-1967 The size of the cable with the proper current carrying capacity can be adopted as per the tables of cables. Current rating tables should be adopted before the selection of the cables.


Proceelain Insulators for O.H. Power Lines (below 1000 Volts) I.S.1445 –1966 General requirements. 4.1 The porcelain shall be sound, free from defects, thoroughly vitrified and smoothly glazed. 4.2 The design of the insulator shall be such that stresses due to expansion and contraction in

any part of the insulator shall not lead to its deterioration. 4.3 The glaze, unless, otherwise specified, shall be brown in colour except for the screw

threads and the parts on which the porcelain is supported during fixing which may be left unglazed. All other surfaces of the insulator shall be effectively glazed.

4.4 The insulators shall be in one piece. The pin insulator shall have a top groove and have dimension as shown in figures in the I.S.

Temperature limits I.S 5819-1970

The short circuit ratings are based on the following temperature limits: Voltage grade of cable

Conductor temperature 0 C Armour temperature 0 C

Maximum for continuous operation

Maximum for short circuit

Prior to short circuit

Maximum to short circuit

3.3 KV 6.6 KV (earthed) 70 150 60 150 6.6 KV (unearthed)

11 KV (earthed) 60 140 50 140 Table 1 - Short Circuit ratings of aluminium conductor for high voltage PVC cable (applicable to single core & three core cables)

Short Circuit Rating for 1 Sec duration 3.3 KV 6.6 KV earthed 6.6 KV

unearthed 11 KV

(T=150 0 C) (T=150 0 C) (T=150 0 C) (T=150 0 C)

Cross Section (mm 2 )

(T o =70 0 C (T o =70 0 C (T o =70 0 C (T o =70 0 C mm2 25 1.80 1.80 1.80 1.83 35 2.52 2.52 2.52 2.56 50 3.60 3.60 3.60 3.65 70 5.04 5.04 5.04 5.11 95 6.84 6.84 6.84 6.76 120 8.64 8.64 8.64 8.76 150 10.8 10.8 10.8 11.0 185 13.3 13.3 13.3 13.5


225 16.2 16.2 16.2 17.5 240 17.3 17.3 17.3 17.5 300 21.6 21.6 21.6 21.9 400 28.8 28.8 28.8 29.2 500 36.0 36.0 36.0 36.5 625 45.0 45.0 45.0 45.6 800 57.6 57.6 57.6 58.4 1000 72.0 72.0 72.0 73.0 T= Maximum short circuit temperature of conductor. T o = Temperature of conductor prior to short circuit for any other multiply the above ratings by 1 /8

Code of practice for installation and maintenance of paper INSULATED POWER CABLES (up to and including 33 KV)

I.S. 1255-1967 Single core cables. Three single core cables forming one three phase circuit shall normally be laid in close Tri-foil formation and shall be bound together at intervals of approximately 1 metre. The relative position of the three cables shall be changed at cash joint, complete transpositions being affected in every three consecutive cable lengths. Where there is not possible and cables are laid side by side, the current rating is lower. The joints shall be clearly marked in an approved manner to indicate the circuit and phases. Where there are a number of parallel cables perhaps, the following manner of cable laying is preferable:- RYB BYR RYB BYR and so on 123 321 123 321 Where the cables are laid on trays for different systems then the systems be laid in changed phases sequence as below: RYB BYR 123 321 RYB BYR 123 321 and so on RYB BYR 123 321 When only three single core cables are laid for a single system, them, the triangular disposition as below is suitable:- B R 3 Y


1 2 In the case of a number of systems, but only one cable per system, the following arrangement would be disadvantageous: B B B B B R 3 Y Y 3 R R 3 Y Y 3 R R 3 y

2 2 1 1 2 2 1 1 2


Section II I.S 1255-1967

Jointing of cables 1. It is not intended to deal in this code with complicated work if jointing of cables in much

detail, as in all cases it would be best to follow strictly the instructions furnished by the suppliers of cables and joint boxes. However, following recommendations are given for general guidance,

2. Jointing work should be commenced as soon as two or three lengths have been laid. This will reduce the time available for moisture to enter the ends of the cable if they are not perfectly sealed, plumbed caps over the ends of the cable can contain pin holes which it is practically impossible to see with the naked eye but which could cause moisture to enter after a period of time. It is, therefore, always advisable to protect the factory plumbed cap by laying the end solid in bitumen until such time as the jointing is commences. Joint position:- During the preliminary stages of laying the cable, consideration should be given to proper location of the joint position so that when the cable is actually laid the joint are made in the most suitable places. Circumstances do not always permit ideal conditions but joint in carriage ways and drives under costly paving under concrete or asphalt surface and in proximity to telephone cables and gas or water mains should be a avoided wherever possible. There should be sufficient overlap of cables to allow for the removal of cable ends which may have been damaged. This point is extremely important as otherwise it may result in a short piece of the cable having to be let in. Joint holes:- Whenever practicable, joint holes should be of sufficient dimensions as to allow joints to work with as much freedom of movement and comfort as possible. For this purpose, the depth of the holes should be at least 0.3 m below the cables proposed to be jointed. The sides of the holes should be draped with small tarpaulin sheets to prevent loose earth from falling on the joint during the course of markings. If the ground has been made up by tapping of if running sand is met with the holes should be well shored well shored up with timber so as to prevent collapse. The two lengths of cable meeting at a joint are laid with as overlap of about 1m, when putting in. This enables the jointer to adjust the position of his slightly to allow for any obstructions that may be encountered. When two or more cables are laid together, the joints are arranged to be staggered by two or three yards, lso as to reduce the excess with of trench and also to isolate the joints from each other and reduce the possibility of one joint failure affecting the other joints. Sump holes:- When jointing cables in water logged ground or under monsoon conditions, a sump hole should be excavated tt one end of the joint holes in such a position so that the accumulating water can be pumped out or baled out without causing interference to the jointing operation. Tents:- A test should be used in all circumstances where jointing work is being carried out in the open. It is a mistake to think that tents are only provided as a protection


against rain. It is equally important to prevent dust from being blown in the exposed joint and jointing materials, especially on the compound and tapes. It follows, therefore, that the tent should be erected in such a manner as to reduce to a minimum the amount of dust or foreign matter likely to be blown in. This is generally achieved by having only one entrance to the tent and the back facing the direction of the wind. The tent cover should be weighted or tied down on the three remaining sides.

Tubular steel poles for overhead power Lines. I.S.2713-1964 Steel tubular poles Tubular steel poles shall be of the following two types: (a) Stepped or (b) Swaged. Manufacture:- (1) Stepped poles shall be made from one length of tube, the diameter being reduced in

parallel steps by passing the tubes through a series of dies. (2) Swaged poles shall be made of tubes of suitable lengths, swaged together when hot,

The upper edge of each joint shall be chamfered off at an angle of about 45 Degree. Chemical composition: The materials when analysed in accordance with I.S. 228-1959 Methods of chemical Analysis of pig Iron, Cast Iron and plain carbon and Low Alloy Steels (Revised), shall not show sulphur and phosphorous contents of more than 0.060 percent each. Physical requirements:- The material when tested in accordance with I.S. 1894-1962 Methods for tensile testing of steel tubes shall show a tensile strength of 55.0 to 65.0 Kg/mm 2 and a minimum percentage along ation of 950 divided by the actual tensile in kg/mm 2 on a gauge length of 5.65/A where As is the cross sectional area of the test piece.

(2)The tensile test shall be conducted on 3 percent of tubes selected from each lot of tubular poles of one size. Freedom from Defects:- Poles shall be well-finished, cleaned and free from harmful defects. Lands of the poles shall be cut square Poles shall be reasonably straight, smooth and cylindrical. Dimensions and Sectional properties:- (1) The dimensions of poles shall be as given in Table I for stepped poles and tube for

swaged poles. Useful properties of these poles calculated on the basis of dimensions are also given in Tables I & II .

(2) A few sectional properties which are useful in designing the poles are given in Tables III & IV Appendix A.


Tolerances:- (1) Outside diameter:- The poles shall be as nearly circular as possible and their outside

diameters shall not vary from the appropriate values, except at the joint or step, by more than + 1.0 per cent.

(2) Thickness:- The thickness of any section shall not fall below the percentage of tolerance given under 11.2.1 and 11.2.2. of this India Standard Specification.

2.1 In the case of electrically welded tubes, the thickness of any section shall not fall below

the thickness specified by more than 10 per cent. 2.2 In the case of seamless tubes, the thickness of any section shall not fall below the

following tolerances:- (a)Where the ratio of the thickness to the outside diameter is more than 3 per cent + 25 percent of the specified thickness . (b)Where the ratio of the thickness to the outside diameter is equal to or less than 3 per cent- 15 per cent of the specified thickness. Weight:- The main weight for bulk supplies shall be not more than 5 per cent below the calculated value. The weight any single pole shall not fall below the calculated weight by more than 1/1600 or its length. Reinforced concrete poles for overhead power and Telecommunication Lines (IS 785-1964) 1. Classification:- Reinforced concrete poles shall be classified into 11 classes as

given in Table I :-

Table I Minimum ultimate transverse load and maximum length for different classes of reinforced concrete poles. Class of pole Max. overall length (m) Minimum ultimate transverse load At 600 mm from top 1 17.0 3000 2 17.0 2300 3 17.0 2000 4 17.0 1400 5 16.0 1100 6 12.5 1000 7 12.0 800 8 12.0 700 9 11.0 500 10 0.00 300 11 7.5 200


1.1 Provided handling and erection stresses are specially checked and adequately catered for in the design the ultimate transverse loads specified in table 1 may be reduced, if so desired by the purchaser, but in no case shall be the minimum ultimate transverse load be less than 120 Kg.

Transverse:- The direction along with the line bisecting the angle made by the conductors at the pole. In the case of a strength run this will be the horizontal direction normal to the run of the conductors. Ultimate transverse Load: The load which causes failure when applied at a point 600 mm below the top and perpendicular to the axis of the pole along the transverse direction with the but of the pole clamped so as to obtain the specified lever arm. Working load: The maximum sustained load in the transverse direction, including wind pressure as a single force applied at a point 600 mm below the top with the butt end of the pole so as to obtain the specified lever arm. Overall length of poles: The minimum overall length of all classes of poles shall be 6 M and the maximum overall length as given in table Intermediate lengths shall be in steps of 0.5 m. Tolerances:- The tolerance on the overall length of the poles shall be of + 15 mm. The tolerance on cross – sectional dimensions shall be + 3 mm . The tolerance on the uprightness of the pole shall be 0.5 per cent. Material:-The cement used in manufacture of reinforced concrete poles shall be either ordinary or raped hardening Portland cement confirming I.S. 269-1958 or Portland blast furnace slag cement confirming to I.S. 455 – 1962. Aggregate:-Aggregates used for the manufacture of reinforced concrete poles shall conform to I.S. 383 –1963 Where specified, a sample of the aggregates shall be submitted with the tender to the purchaser for approval. The whole of the aggregate pass through a sieve having apertures not exceeding three quarters of the minimum distance between the main reinforcing bars but in no case shall the maximum size of the aggregate exceed 20 mm. Reinforcement: Reinforcing bars and wires used for the manufacture of reinforced concrete poles shall be one of the following :- (a) Mild steel and medium tensile steel bars and hard drawn …. Wire conforming to I.S.

432-1960. (b) Annealed wire with an ultimate tensile strength not less than 32 Kg. Per sq. mm. (c) The surface of all reinforcement shall be free from loose scale, oil, grease, clay of other

material that may have deteriorating effect on the bond between the reinforcement and the concrete. Slight hard rust my, however, be permissible.

Concrete: Concrete used for the manufacture of reinforced concrete poles shall comply with the requirements specified in I.S 456-1964. Where ordinary concrete conforming to


the requirements of I.S 456-1964 is used, the cement aggregate ratio for concrete shall be not less than 1:3 . Wood poles for overhead power and Telecommunications Lines. I.S. 876-1961 Wood pole _ Long, solid, fairly straight stem of a three approximately circular in cross- section. Specimens of Timber: Timber suitable for wood poles shall be classified into three groups as indicated below based on the modulus of rupture of shall clear specimens (Sec. I.S. 1708-1960) Methods of testing small clear specimens of Timber) tested in the green state, that is, above 25 per cent moisture content. Group –A- Very strong timber having a modulus of rupture in bending of 850 Kg./Cm2 and over represented by sal (shorea robsta) Group-B- Strong timber having a modulus of rupture in bending 630 to 850 Kg/Cm2, represented by teak (Tectona grounds) Group- C Moderately strong timber having a modulus of rupture in bending 450 Kg/Cm2 to 630 Kg /Cm2 represented by choir (pinus longifulia). Preservation :- Sap wood of all species of timber is permissible. Therefore, poles shall be treated with a preservative so as to impregnate completely the sap wood and as much of heartwood of non-durable species as possible. The pressure and the preservative treatment shall be as given in Appendix C. Dimension:- Dimensions of wood poles of different timber specifics and different of strength classes (sec. 3 and 4) shall be given in Table I.

(1) For poles of intermediate lengths, the sizes given for next longer pole shall be used.

Measurement:- Length:- Length of poles shall be measured between the extreme ends of poles. Poles shall be not more than 7.5 cm. Shorter of more than 15 cm. Longer than the specified length. Circumference:- Circumference of the pole shall be measured at the top and at the mark representing ground level and shall be as given in Table I.


Prestressed concrete poles for overhead power, traction and Telecommunication Lines. Telecommunication Lines. I.S. 1678 – 1960

Classification : The prestressed concrete poles shall be classified into 11 classes conforming to minimum ultimate transverse load and maximum overall length given in Table I.

Table I Minimum ultimate transverse load and maximum length for different classes of prestresed concrete poles. Class of poles Maximum overall length. Minimum ultimate Transverse load. Mtr Kg. 1 17.0 3000 2 17.0 2300 3 17.0 1800 4 17.0 1400 5 16.0 1100 6 12.5 1000 7 12.0 800 8 12.0 700 9 11.0 450 10 9.0 300 11 7.5 200 Overall length of poles:- The minimum overall length of all classes of poles shall be 6 m and maximum overall length shall be as specified in Table 1. Further the lengths shall be in intervals of 0.5 m. Tolerance: The tolerance of overall length of the poles shall be + 15 mm. The tolerance on cross-sectional dimensions shall be + 3 mm. The tolerance on cross-sectional dimensions shall be + 3 mm. The tolerance on uprightness of the pole shall be 0.5 per cent. Material:- Cement: The cement used in the manufacture of prestressed concrete poles shall be ordinary or rapid hardening Portland cement conforming to I.S. 269-1958 or Portland blast-furnace slag cement conforming to I.S. 455- 1953. Aggregates: Aggregates used for the manufacture of prestressed concrete poles shall conform to I.S. 383-1952. Where specified, a sample of the aggregates shall be submitted with the tender to the purchaser for approval. The maximum size of aggregates shall in no case exceed 20 mm.


High Tensile Steel : The high tensile steel wire and bars used for the manufacture of prestressed concrete poles shall conform to the relevant Indian Standards Specifications. The diameter of smooth wire used for pretensioning system. Where prestress is developed by bond shall not exceed 5 mm. Other reinforcement: Reinforcing bars and wires used for the manufacture of prestressed concrete poles shall be of the following:- (a) Mild steel and medium tensile steel bars and hard drawn steel wire conforming to I.S.

432-1960. (b) Annealed wire with an ultimate tensile strength of not less than 32 Kg/mm2. The cold

drawn steel wire shall satisfy cold bend test specified in I.S. 432-1960. Depth of planting :- The minimum depth of planting of pole below ground level shall be in accordance with Table II, the actual depth being determined on the basis of ground conditions. Table II Minimum depths of planting of prestressed concrete poles in the ground. Length of poles Minimum depth in grounds

(1) (2) m. m.

6.0 to 7.5 1.20 8.0 to 9.0 1.50 9.5 to 11.0 1.80 11.5 to 13.00 2.00 13.5 to 14.5 2.20 15.00 to 16.5 2.30 17.0 2.40 I.E. Rule 76 Supports Maximum stresses: Factors of safety (1) (a) The owner of every overhead line shall ensure that it has the following minimum factors of safety. The minimum factors of safety for supports based on crippling load shall be as follows:- (1) For metal supports 2.0 (2)For mechanically processed concrete

supports. 2.5 (3)For hard moulded concrete supports 3.0


(4)For wood supports 3.5 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 directions transverse to the line.

Provided that in the case of latticed steel or other compound structures, the 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. The said owner shall also ensure that the strength of the supports in the direction of the lines 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 broke wire condition as may be specified by the State Government in this behalf.

I.E. Rule 90 Earthing

1) All metal supports of overhead lines and metallic fitting attached thereto, shall be permanently and efficiently earthed. For this purpose a continuous earth wiring shall be provided and securely fastened to each pole and connected with earth ordinarily at four points in every 1.609 Km. (mile), the spacing between the points may as nearly equidistance as possible . Alternatively, each support and the metallic fitting attaching thereto shall be efficiently earthed.

(2)Each stray wire shall be similarly earthed unless insulator has been placed in it at a height not less than 3.048 meters (10 ft.) from the ground.

Galvanized stay strand. I.S. 2141-1979 Stray

Material: The wire shall be drawn from steel made by the open hearth basic oxygen or electric furnace process and of such quality that when drawn to the size of wire specified and coated with zinc finished strand and the individual wires shall be inform quality and have the properties and characteristics as specified in this specification. The wire shall be not contain sulphur and phosphorous exceeding 0.060 per cent each.

Tensile grade: The wire shall be of following grades: Grade Tensile designation Minimum tensile strength N/mm2. 1. 1770 1770 2. 1570 1570 3. 1100 1100 4. 700 700 5. 450 450


Tests on wires before manufacturing 1. Ductility test: The wire shall be subjected to the wrapping test in accordance with I.S.1755-

1961, method for wrapping test of wore. When wrapped eight times round its own, diameter and on being subsequently strengthened the wire shall not break or split.

Tolerance on wire diameter. The diameter of the test piece shall be determined with a micrometer by taking two measurements at three places along a length of not less than 250 mm and the average of these six measurements shall be taken as being the diameter of the galvanised wire.

Test on complete strands 1. Tensile and elongation test:

The and of the strands shall be suitably prepared by either filling in the interstices with finer wire or other suitable means, to minimize failure at the testing machine grips. The load shall be applied at a steady rate not exceeding 100 N/mm2 per second. An initial load of 10 per cent of the specified breaking load shall be applied to the test piece, at which stage the distance apart of the testing of machine grips shall be 30 times of the strand subject to a minimum of 100 mm.

2. The elongation shall be determined as the percentage increase in separation between the

grips from the position after application of the initial load to the position at the initial failure in the test piece. Elongation test shall made on lengths of strand which do not contain wire joints. The percentage elongation of the strands shall not be less than that specified below:

Grade Minimum percent elongation

1 2 2 3 3 4 4 10 5 12

3. It the test piece breaks within 25 mm. Of the grips of the testing machine and shows less

than the specified elongation, the tests shall be disregarded and further tests made until the break occurs more than 25 mm. From the grips. Additional test pieces shall be taken from the same coil or drawn when the previous tests are to be disregarded.

Making:

The size. Construction, tensile designation, lay, coating, lengths, mass, manufactures name or trade make, lot number and coil number along with the order number of purchaser and any other making which may be specified by the purchaser shall be legibly stamped upon a metallic tag securely attached when galvanized stay strands are supplied in coil. In case galvanized stay strands are supplied in coil the information may be strencilled on both sides of the reels or strencilled on one side of the real and metallic tag giving the information may be attached on other side of the coil.


Porcelain Insulators for O.H. power Lines (below 1000 V) I.S. 1445-1966

General requirements 4.1 The porcelain shall be sound, free from defects, thoroughly verified and smoothly glazed. 4.2 The design of the insulator shall be such that tresses due to expansion and contraction in

any part of the insulator shall not lead to its deterioration. 4.3 The glaze, unless otherwise specified, shall be brown in colour except for the screw

threads and the parts or which the porcelain is supported during fixing which may be left unglazed. All other surfaces of the insulator shall be effectively glazed.

4.4 The insulators shall be in one piece. The pin insulator shall have a top groove and have dimensions as shown in figures in the I.S.

Porcelain Insulators for overhead lines (3.3 KV and above) I.S. Specifications. I.S. 731-1971 Insulator above 1000 Volts. General Specifications:

4.1 The porcelain shall be sound free from defects, thoroughly verified and smoothly glazed. 4.2 Unless, otherwise specified, the glaze shall be brown in colour. The glaze shall cover all

the porcelain parts of the insulator except those areas which serve as supports during fixing or are left unglazed for the purpose of assembly.

4.3 The design of the insulator shall be such that stresses due to expansion and contraction in any part of the insulator shall not lead to deterioration. The porcelain shall not engage directly with hard metal.

4.4 Cement used in the construction of the insulator shall not cause fracture by expansion or loosening by contraction and proper care shall be taken to locate the individual parts correctly during cementing. The cement shall not give rise to chemical reaction with metal fitting and its thickness shall be as uniform as possible.

Classification:

Overhead line insulators are divided into two types according to their construction. Type A- An insulator unit in which the length of the shortest puncture patch through solid insulating material is at least equal to half the length of the shortest flashover path through air outside the insulator. Type B- An insulator or an insulator unit in which the length of the shortest puncture patch through solid insulating material is less than half the length of the shortest flash over path- through air outside the insulator.

Basic Insulation Levels: 1. The basic insulation levels of the insulators shall be given in table IA and Table I B. 2. In this, standards, power frequency voltages are expressed as peak values divided by 2

and impulse voltages are expressed as peak values. 3. The withstands and flash over voltages are referred to the reference atmospheric

conditions.


Mechanical Loads: 1. The insulators shall be suitable for the minimum failing loads specified in table 2. The

loads shall be transverse in the case of pin and line post insulators and axial in the case of string insulators units.

Table 2 A.

Test voltage for all insulators up to and including 72.5 KV. Rated voltage and for insulators for non effectively earthed system above 72.5 KV.

Highest system voltage

Visible discharge test

Wet power frequency withstand test

Power frequency puncture withstand

Impulse voltage withstand test

Power frequency puncture withstand

KV (rms) KV (rms) KV (rms) KV (peak)

KV (rms) KV (rms)

3.6 3 21 78 1.3 times the actual 45 7.2 5.5 27 90 wet flash over voltage 60 12 9 35 105 of the unit. 75 24 18 55 140 125 36 27 75 180 170 72.5 53 140 310 325 123 88 230 - 550 145 105 275 - 650 245 154 460 - 1050 Even though highest system voltage of 123 KV. is not standard value in I.S. 585-1962 voltages and frequency for AC transmission and distribution system a number of older power systems are retaining the nominal system voltage of 110 KV which corresponds to the highest system Voltage of 123 KV. The test voltage for this highest system voltage are, therefore, given for the benefit of such power system . Table I B Test voltages for insulators for use on affectively earth system above. 72.5 KV Highest Visible Wet. Power Power frequency Impulse Voltage System Discharge frequency puncture with withstand Voltage test withstand stand test on test. Test. String insulator Tests. KV (rms) KV (rms) KV (rms) KV(rms) KV (peak) --------------------------------------------------------------------------------------------------------------------------------123 88 185 1.3 times 450 145 105 230 the actual wet 550 245 154 395 flashover voltage 900 420 266 680 of unit. 1550


Table 2 Minimum Failing loads string Insulator units. Pin Insulator. Line Post Insulator. Failing Load. Recommended pin Ball shank dia. --------------------------------------------------------------------------------------------------------------------------------- KN KN KN mm 5 10 45 11 or 16 10 -- 70 16

90 16 120 11 or 20 160 24 190 24

--------------------------------------------------------------------------------------------------------------------------------- Creepage Distance:- No minimum creepage distance are specified for clear atmospheric conditions. Highest Moderately Heavy polluted atmospheres System polluted Voltage atmospheres Total Protected KV. mm mm mm 3.6 75 130 -- 7.2 130 230 -- 12 230 320 -- 24 430 560 -- 36 580 840 420 72 1100 1700 850 123 1850 2800 1400 145 2250 3400 1700 245 3800 5600 2800 420 6480 9660 4830 Note:- For insulator used in an approximately vertical position the values given in Col.2 or 3 and 4 shall Apply. For insulators used in an approximately horizontal position, they values given in Col. 2 shall apply, but the values in Cal. 3 and 4 may be reduced by as much as 20 percent. Tests: 1. Routine Tests: The following tests shall be carried out as routine tests:-

(a) Visual examination. (b) Mechanical routine test ( for string insulator units only). (c) Electrical routing test (for type B string insulators and rigid insulators.

2. Visible discharge tests: The test room shall be darkened and a period of five minutes shall be allowed for the observer to become accustomed to darkness. A power frequency test voltage of the specified value given in table IA or table 18 shall be applied in accordance with Appendix B and maintained at this value for five minutes. During this time observations shall be made there shall be no sign of visible corona.


3. Impulse Voltage withstand test: (1) The insulator shall be tested dry under the conditions prescribed in Appendix B. (2) The impulse generator shall be adjusted to produce a standard 1.2150 impulse wave of

peak value equal to the specified value of the impulse withstand voltage corrected for atmospheric conditions in accordance with Appendix A.

(3) Five such impulse voltage waves shall be applied to the insulator. If there is no flashover or puncture the insulator shall be considered to have passed test. If during the application of these five waves puncture occurs or if there is more than one flashover, the insulator shall be considered to have failed to comply with the standard. If only one flashover occurs a new series of ten impulse waves shall be applied. The insulator shall be considered to have passed this test only if during this new series of tests there is no flashover of puncture.

(4) The insulator shall be capable of passing the impulse voltage withstand test with voltages of both positive and negative polarity. However, when it is evident which polarity will give the lower breakdown voltage, it shall surface to test the polarity.

(5) To provide information when specially requested the 50 percent impulse flashover voltage for positive and negative polarities may be determined by a suitable procedure.

(6) The impulse flashover voltages to be recorded shall be at the positive and negative 50 percent impulse flashover voltage as measured above and corrected in a accordance with Appendix A.

(7) The insulator shall not be damaged by these tests, but slight marks on the surface of the insulating parts of chipping of the cement of other material used for assembly shall be permitted.

4. Wet power frequency voltage withstand test:

(1) The insulator shall be arranged as prescribed in Appendix B. (2) Before the commencement of the test, the insulator shall be exposed to the artificial

rain produced in accordance with 3.3 of I.S. 2071-1962 for at least one minute before application of voltage and then throughout the test.

(3) The test voltage to be applied to the insulator shall be the specified value of the wet power frequency withstand voltage adjusted for atmospheric conditions at the time of test.

(4) A voltage of about 75 percent of the test voltage as determined in 3 shall be applied and then increased gradually to reach the test voltage in a time not less than five seconds. The test voltage shall be maintained at this value for one minute.

The insulator shall not flashover or puncture during the application of the test voltage.

5. To provide information when specially requested the wet flashover voltage of the insulator may be determined by increasing the voltage gradually from about 75 percent of the wet withstand voltage to reach the flashover voltage in not less than five seconds. The flashover voltage shall be the arithmetic mean of five consecutive reading and the value after correction to standard atmospheric conditions shall be recorded.

6. Temperature Cycle Test: Insulators with their integral parts, if any, shall be quickly6 and completely immersed without being placed in an intermediate container in a water both maintained at temperature of 70 D.C higher than that of the cold bath used in the nest of the test and left submerged for 15 minutes. They shall then be withdrawn and quickly and


completely immerged being placed in an intermediate container in the cold water bath where they shall remain for 15 minutes. This heating and cooling cycle shall be performed three times in succession. The time taken to transfer from either bath to the other shall be as short as possible and never exceed 30 seconds. The quantity of water in the test tanks shall be sufficiently large for the immersion of the insulators so as not to cause a temperature variation of more than + 5D.C in the water. On completion of the third cold cycle the insulator shall be examined to verify that they not cracked. Type A insulators shall then be subjected to the mechanical test prescribed in 10.14. Type B insulator shall be subjected for one minute to the power frequency test prescribed in 10.15 . The insulators shall withstand the appropriate test without cracking or puncture of mechanical wreckage.

7. Electromechanical finding load test (on type B string insulators only).

(1) This test shall be applied to string insulator units of such types where electrical discharge will serve to indicate mechanical failure. For other time the insulators shall be submitted to the mechanical failing load test.

(2) The insulator units shall be subjected individually to a power frequency voltage and to a tensile load applied simultaneously between the metal parts.

(3) For insulator with ball and socket couplings, the coupling pieces of the testing machine shall be in accordance with I.S. 2486 as regards their essential dimensions.

(4) The voltage shall be 50 percent to 60 percent of the specified wet power frequency withstand voltage of the string insulator unit and it shall be maintained at this value throughout the test.

(5) The tensile load shall be gradually increased form a value of 75 percent of specified electromechanical failing load until it reached.

(6) The insulator passes the test if the specified electromechanical failing load is reached without puncture.

(7) To provide information when specially requested, the load may be increased until the failing load as defined in 2.12 is reached the value recorded.

8. Mechanical failing load test. (String insulator units) (1) String insulator units of type A and those of the B to which the electromechanical

failing load test is not applicable shall be subjected individually to a tensile load applied between the metal parts.

(2) For insulators with ball and socked coupling, the coupling pieces of the testing machine shall be in accordance with I.S. 2846. (part II) 1963 as regards their essential dimensions.

(3) The load shall be gradually increased from a value of 75 per cent of the specified mechanical failing load until the specified mechanical failing load is reached.

(4) The insulator passes the tests if the specified mechanical failing load is reached. (5) To provide information when specially requested, the load may be increased until

the failing load is defined in 2.13 is reached and the value recorded. 9. Rigid insulators:

Rigid insulators shall be mounted on a rigidly fixed pin capable of withstanding without appreciate deformation the loads to which it will be subjected during the test, insulators


provided with integral metal fittings for mounting shall be mounted for lest using these fittings. The insulator shall be subjected to a load equal to 75 per cent of the specified mechanical failing load applied perpendicular to the axis of the insulator in the plane of the side groove. The wire rope shall be such that localized stresses in the side groove of the insulator are avoided. If the insulator is provided with means of clamping the conductor, the load shall be applied to this clamp till the mechanical failing load is reached. (1)The insulator passed the test if the specified mechanical failing load is reached. (2)To provide information when specially requested the load may be increased until the failing load as defined in 2.13 is reached and the value recorded.

10. Twenty four hours test- mechanical test (for string insulator only) (1) The insulator shall be subjected for 24 hours to a tensile load, applied axially which

shall be two- thirds of the specified minimum failing load. (2) The insulator shall then pass the power frequency routine test given in 10-15.

11. Puncture test (for insulators type B only) The puncture test may be either a power frequency puncture test or by agreement between manufacturer and purchaser, an impulse over voltage test.

12. Power frequency puncture test:- The insulators after having been cleaned and dried, shall be completely immersed in a thank containing a suitable insulating medium to prevent surface discharge on them. If the tank is made of metal, its dimensions shall be such test the shortest distance between a by part of the insulator and the side of the tank is not less than 1.5 times the diameter of the largest insulator shed. The immersion medium shall be at about room temperature. (2)The test voltage shall be applied between those parts which normally have the operating voltage between them. During immersion in the insulating medium, precautions shall be taken to avoid air pockets under the sheds of the insulator. (3) The voltage shall be raised as rapidly as is consistent with its value being indicated by

the measuring instrument to the specified puncture voltage. No puncture shall occur below the specified puncture voltage.

(4) To provide information when specially requested the voltage may then be raised until puncture occurs and the puncture voltage is recorded.

13 Porosity test:- (1)Porcelain fragments from the insulators or by agreement, from representative pieces of porcelain fired adjust to them shall be immersed in a 1 percent alcohol solution of function (1 g fuchsion in 100 g methylated spirit) under a pressure of not less than 15x106N/M2 for a time such that the products of the test duration in hours and the test pressure in N/m2 is not less than 180x106. (2)The fragments shall then be removed from the solution, washed, dried and again broken. (3)Examination with naked eye of the freshly broken surface shall not reveal any penetration into small cracks formed during the initial breaking shall be neglected.

14. Galvanising test: This test comprises firstly variation of the uniformity of the coating of zinc (test by immersion in copper sulphate) and secondly verification of the weight of zinc per unit surface (test by chemical dissolution). This second test is optional and shall be carried out only if so agreed by the manufacturer and the purchaser. (2)The uniformity of zinc coating of galvanised material fittings shall satisfy the requirements.


15. Visual Examination Test:- A visual examination shall be made on each insulator. The colour of the insulator shall approximate to the colour specified on the drawing. Some variation in the colour shade is permitted and shall not justify rejection of the insulator. The insulator shall be free from physical distortion of shape within tolerances specified.

The areas specified as glazed on the drawing shall be covered by a smooth hard glaze free from cracks and other defects prejudicial to satisfactory performance is service. Out of those areas specified as glazed on the drawing the total area not covered by the glaze shall not exceed (1+DF)/2000 cm 2 Also the area of any single glaze defect shall not exceed (0.5 + DF)/20.000 cm 2 Where D is the greatest diameter of the insulator in centimetres.

16. Mechanical Routine Test:- A Type of string insulator units shall be subjected for at least 1 minute to a tensile load equal to 60 per cent of the specified mechanical failing load.

(1)Type B string insulator shall be subjected for at least 10 seconds to a tensile load equal to 40 percent of the specified electro mechanical failing load. (2)Insulators which break whose metal parts are fractured or become detached ruing the test shall be rejected.

17. Electrical Routine Test:- Type B string insulator units and rigid insulators shall be subjected to a power frequency voltage. For string insulator units, the voltage shall be applied between the metal part, but the nominal metal work of inter linked insulators may be replaced by other suitable fittings.

(1)Rigid insulators shall be placed head down area in a tank containing water to a depth sufficient to cover the side conductor grooves and the voltage shall be applied between the tank and water practically filling the in hole or …………..of each insulator, Alternatively, metal electrodes may be used provided the electric stress in the porcelain is not reduced. (2)The test voltage shall be such as to produce frequent flashover (every few seconds). (3)The time of application of the test voltage shall be at least 5 consecutive minutes. (4)Insulators which puncture during the test shall be rejected.

Sampling procedure:

Sample Size: The number of insulators to be selected at random from the lot shall be in accordance with col 2 of the Table 5 if required additional insulators as given in col. 3 of Table shall also be sealed at random.


Table 5 sample size and criterion of conformity. C-1 Lot size First sample size. Second Sample size. Acceptance Rejection Number. Number. ------------------------------------------------------------------------------------------------------------------------ (1) (2) (3) (4) (5) ---------------------------------------------------------------------------------------------------------------------- N N1 N2 C1 C2

101 to 500 ‘ 5 10 0 2 501 to 800 7 14 0 3 801 to 1300 10 20 0 3 1301 to 3200 15 30 1 4 3201 to 8000 25 50 2 5 8001 & above 35 70 2 7 Note: All the insulators selected as in C-1 as above shall be subjected to the appropriate acceptance test. C-2 Conformity Test:- The lot shall be considered as conforming to the requirements of the acceptance tests of the number of failures found in the first sample N1 is less than or equal to C1. If the number of failures is greater than or equal to C2, the lot shall be considered as not conforming to the requirements of the acceptance tests and shall be rejected. If the number of failures is between C1 and C2 and a second sample of N2 insulators shall be selected and subjected to acceptance tests. If the number of failures in the two sample combined is loss than C2, the lot shall be considered as conforming to the requirements of acceptance to tests otherwise it shall be considered to have failed. Guard Wire I.E. Rule 88 (1) Every guard wire shall have an actual breaking strength of not less than 635.02 Kg.

(1400 Lbs) and if made of iron or steel, shall be galvanized. (2) Every guard wire shall be connected with earth at each point at which its electrical

continuity is broken.

Hard drawn stranded aluminium and steel-cord aluminium conductors for overhead power transmission purposes (Revised). I.S 398-1976. 9.1 The wires used in the construction of a galvanized steel reinforced aluminium conductor shall before stranding, satisfy all the relevant requirements of this standard. 9.2 The lay ratio of the different layers shall be within the limits given in table 4. 9.3 The ratio of the nominal dia of the aluminium wires to the nominal dia. of the galvanized steel wires in any particular construction of galvanized steel reinforced Aluminium conductors, shall conform to the appropriate value given in table 4.


9.4 In all constructions, the successive layers shall have opposite directions of lay, the outermost layer being right handed. The wire in each layer shall be evenly and closely strained. 9.5 In conductors having multiple layers of aluminium wires the lay ratio of any aluminium layers shall not be greater than the lay ratio of the aluminium layer immediately beneath it. Hard drawn stranded aluminium and steel cored aluminium conductors for over head powers transmission purposes. I.S. 398 – (Part –I 1976). Table 1 Aluminium wires used in the construction of aluminium stranded

conductors. diameter work. Cross

section area of nominal diameter work.

Mass Resistance at 20.c Max

Breaking load Min

Nom. Min Max. Befvore stranding

After stranding

mm. mm. mm.

mm 2

Kg/Km

Omega/m KN KN

2.21 2.19 2.23

3.836 10.37 7.553 0.68 0.65

3.10 3.07 3.13 7.548 20.40 3.843 1.24 1.18 3.18 3.15 3.21 7.942 21.47 3.651 1.29 1.23 3.99 3.95 4.03 12.50 33.80 2.332 1.98 1.88 4.39 4.35 4.43 15.14 40.91 1.914 2.40 2.28 4.65 4.60 4.70 16.98 45.90 1.712 2.70 2.56

Note 1:- The resistance has been calculated from the maximum value of resistivity and the cross sectional area based on the minimum diameter.

Note 2:- The resistance of individual wires shall be such that the completed stranded conductor meets the requirements of the maximum resistance specified in Table 2 calculated by applying the relevant stranding constants given in Table 4.


Table – 2 Aluminium stranded conductors

Nominal area

Sranding Dia.

Sectional area

Overall Dia.

Mass Approx Aluminium

wire resistance at

calculated 20 0 C

Maximum breaking

load

mm 2 mm mm 2 mm Kg/Km �.P KN

25 7/2.21 26.85 6.63 74 1.093 4.52 50 7/3.10 52.83 9.30 145 0.5561 8.25 100 7/4.39 106.0 13.17 290 0.2770 15.96 150 19/3.18 150.9 15.90 415 0.1956 23.28 240 19/3.99 237.6 19.95 654 0.1244 35.74 300 19/4.65 322.7 23.25 888 0.09171 48.74 Note: 1 :- For this basis of calculation sec. Appendix A. Note:2 :- The sectional area of a stranded conductor has been taken as the sum of the cross-sectional are a of the individual wires.

Table 3 lay ratios for aluminium stranded conductors.

Number of wires in conductor. Lay Ratio 6 wire layer 12 wire layer. Min. Max. Min. Max. 7 10 14 -- -- 19 10 16 10 14

Table 4 stranding Constants. Number of wires in conductor. Stranding constants Mass Electrical Resistance. 7 7.091 0.1447 19 19.34 0.5357


Resistance Test:-The electrical resistance of one specimen cut from each of the samples taken 11.1.1 or 11.1.2 shall be measured at ambient temperature. The measured resistance shall be corrected to the value at 20 0 C by means of the formula. R 20 =R T /(1+ �W-20)) Where R 20 = Resistance corrected at 20.C R T = Resistance measured at T.C = Constant mass temperature co-efficient of resistance�� = 0.004) and T = Ambient temperature during measurement. The resistance corrected at 20 Degree shall be not more than the maximum value specified in table 1.

Non-Linear Register Type Lighting Arrestors I.S. 3070 (Part-I_ 1974).

Lightning Arrestor: A device designed to protect electrical apparatus from high transient voltage and to limit the duration and frequency the amplitude of follow-current. The term ’Lightning Arrestor’ includes any external series which is essential for the proper functioning of the device as installed for service, regardless of whether or not it is supplied as an integral part of the device. Note:- Lightning arrestors are usually connected between the electrical conductors of a network and earth although they may some times be connected across the windings of apparatus or between electrical conductors. Protective characteristics of an arrestor:- The combination of the following.

(a) Lightning voltage impulse spark over voltage/time curve as determined in 7.7.3. (b) The residual voltage/discharge current curve as determined in 7.8 (c) For 10,000 A arrestors rated 100 KV and higher the switching- voltage impulse spark

over voltage/ time curve as determined in 7.7.4. Normal Service Conditions:- Lightning arrestors which conform to this standard shall be suitable for operation when installed outdoor and exceed to direct sun under the following normal service conditions:-

(a) Ambient temperature within the range of – 10.c to + 50.c (b) Altitude not exceeding 1000 m. (c) Frequency of the AC power supply not less than 48 HZ and exceeding its rated

voltage. Rating: Lightning arrestors shall be rated in terms of the following: (a) Voltage (b) Frequency & (c) Nominal Discharge Current,


Standard Voltage ratings:- Standard values of rated voltage for arrestors(in Kilovolt r.m.s.) shall be:- 0.175, 0.280, 0.500, 0.660, 3.4.5, 7.5, 9,10.5 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 51, 51, 54,, 60, 75, 84, 96, 102, 108, 120, 126, 138, 150, 174, 186, 186, & 198. Standard rating frequencies: The standard rated frequencies are 50 Hz and 60 Hz. Standard Nominal discharge currents:- The standard nominal discharge currents are 10,000 A, 5000 A, 2500A, and 1500A having an 8/20 wave-shape. Note:- For the 10,000A arrestor there are two types light duty and heavy duty, which are different rated by the amplitude of the long duration, impulse current which they are capable of withstanding.

Test requirements and performance characteristics: Lightning arrestors are classified by their standard nominal discharge currents. They shall meet the test requirements and performance characteristic listed in Table 1.

Marking:- Each lightning arrestor shall be provided with a name plate or plates legibly and indelibly marked with at least the following formation:-

(a) Rated voltage. (b) Rates frequency, of other than one of the standard frequencies. (c) Nominal discharge current (Specifying for 5000 A arrestor whether series A or series

B). (d) Long-duration discharge class (for 10,000 A heavy duty arrestors). (e) Pressure-relief class ( for arrestors fitted with pressure-relief devices). (f) The manufacture’s name or trade make, type the identification. (g) They year of manufacture. (h) Number and order of assembly of the units (if arrestor consists of more than one units).

Note:- The work ’rated’ need not appear on the name plate, recognised abbreviation may be used to express the above quantities.

Tests

General:- (1) Except when specified otherwise all tests shall be made on the same arrestors, arrestor sections or arrestor units. They shall be new, clean, completely assembled and arranged as nearly as possible as in service and shall be fitted with grading rains, if used. (2)The measuring equipment shall meet the requirements of I.S. 2070-1962 and the values obtained shall be accepted as accurate for the purpose of compliance with the relevant test clauses.


(3) Power- frequency voltage tests:- All power frequency tests shall be made with an alternation voltage having a frequency between the limits of 48 Hz and 62 Hz and an approximately sinusoidal wave shape.

(4) Wet test:- It is generally recognised that et tests are not intended to reproduce actual operating conditions but to provide a criterion based on accumulated experience that satisfactory service operation will be obtained. These should be carried out in accordance with I.S. 2070-1962.

(5) The test should give reproducible results in the same and in different laboratories. (6) Wet tests shall be made only on arrestors designed for use outdoors. Where such a

test is specified, the test abject shall be subjected to a spray of water of prescribed resistivity provided by a properly located nozzle or nozzles. The spray consisting of shall drops. Shall fall on the test abject at an angle approximately 45 D to the vertical and horizontal components of the precipitation rate.

(7) The vertical component of the spray shall be measured with a collecting vessel having a horizontal opening area 100 cm2 to 750 cm2 when both vertical and horizontal components are required, the horizontal component shall be measured with a collecting vessel having a similar vertical opening directed towards the nozzles. The collecting vessel should be located on the side of the test object facing the nozzles and as close to the test object as is possible without collecting splashes from it.

(8) For test objects of height greater than 50 cm, measurements of the rate of precipitation shall be made near the and the middle and values obtained for any one position shall not differ by more than 25 per cent from the average for the three positions, for test objects of 50 cm, height of less, the measurements shall be made near the middle only.

(9) The test object shall be sprayed for at least one minute before the application of voltage (alternatively more consistent results may be obtained if the test object is thoroughly wetted with water of the prescribed resistivity and temperature before the application of voltage). The characteristics of the spray shall be as follows:- (a)Precipitation rate vertical component 3mm / mix + 10 per cent. (b) Resistivity of water 10,000 cm + 10 percent. (c)Temperature of water (in Celsius degree)

Ambient temp + 15 Degree. (d) Type of nozzle. (e) Water pressure.

10. Polluted Housing Test:- The development of artificial pollution testing has not yet reached the stage at which it is possible for formulate a mandatory test for lightning, arrestors. Useful information may be gained however for existing test methods and certain general principles may be laid down in their application to lightning arrestors. Proposals embracing these principles, together with reference to several such methods are given in appendix B to stipulate further investigation in the expectation that from experience gained in such investigation it will be possible to devise an agreed method on which a mandatory test may be based.


Expulsion type Lightning Arrestors: I.S. 3070 (Part-II 1966)

Normal service conditions:- Lightning arrests which conform to this standard shall be suitable for operation under the following normal service conditions:- (a) Ambient temperature:- (1) Maximum ambient air temperature 45 Degree C. (2) Maximum daily average air temperature 35 Degree C. and (3) Maximum yearly average ambient air temperature 30 Degree C. (b) Altitude not exceeding 1000 metres. (c) Frequency of the alternating current power supply not less than 40 and not more than

60 cycles per second. (d) Power frequency voltage applied between the line and the earth terminals of the

arrestors not exceeding its rated voltage. (e) Maximum and minimum prospective fault currents at the arrestor locations within the

range of minimum-maximum power frequency current interrupting rating of the arrestors. Possible changes in the prospective fault current which may result from changes in the system, such as changed in system capacity or neutral earthing shall be considered.

(f) Short-circuit power factor of the system at the point of installation of the arrestor not lower than the appropriate test circuit power factor, or higher than the appropriate X/R ration.

(g) Rate of rise of transient recovery voltage ( or natural frequency) and the amplitude factor of the system shall not exceed the rated, rate of rise of transient recovery voltage and the rated amplitude factor.

Classification:- Expulsion type lightning arrestor shall be classified as (a) Thirty kilo Amperes discharge capacity distribution class. (b) Sixty five kilo Amperes discharge capacity distribution class and (c) Transmission-class. Ratings:- Expulsion type lightning arrestor shall be rated in terms of the following:- (a) Voltage. (b) Frequency. (c) Impulse withstand current. (d) Power frequency current interrupting rating (minimum to maximum), transient recovery

voltage and short circuit power factor. Voltage:- The rated voltage in KV rms of transmission class expulsion type arrestors (expulsion protector fuses ) shall be 9, 12, 15, 18, 21, 24, 30,36, 60, 75, 968/20. Frequency:- The rated frequency shall be the standard frequency of 50 c/s.


Marking:- Each lightning arrestor shall be provided with a name plate or plated legibly and indelibly marked with a least the following information:- (a) Name of trade mark of the manufacturer and country of manufacture. (b) Type, designation and or serial number, (c) Rated voltage. (d) Rated discharge current. (e) Power frequency current interrupting rating (minimum and maximum values). (f) Arcing gap spacing, if adjustable by user and (g) External series gap spacing ( if used) (if the external series gap spacing is adjustable,

the minimum and maximum value shall be stated). Voltage withstand test of arrestor insulation:- Dry and wet tests shall be made in accordance with 8 on the assembled insulating members of those arrestors which have both line and earth terminals attached directly to them . The arcing chamber and series gap electrodes shall be removed to permit these tests. The test piece shall withstand without flash over the application of the appropriate power frequency voltage for one minute as specified in Cal. 2 of table 4 for distribution class of table 5 for transmission class arrestors. In wet tests, the piece shall be subjected to precipitation as specified in 3.3 of I.S. 2071-1962. The test voltage shall be applied between the line and earth terminals of the arrestor. E.I Rule 92: 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 subject to the avoidance of bonds wherever possible. India Electricity Rules :- I.E. Rules 77: 1. No conductor of an overhead line including service lines, erected across a street

shall at any part thereof at a height less than:- (a) For low and medium voltage lines- 5.791 m (19 ft.) (b) For high voltage lines- 6.096 mt. (20 ft.)

2. No conductor of an overhead line, i/c service lines erected along any street shall at any part thereof be at a height less than: (a) For low and medium voltage lines- 5.485 M (18 ft) (b) For high voltage lines- 5.791 M (19 ft).

3. No conductor of as overhead line i/c service lines, erected also where than along of across any street shall be at a height less than:- (a) For low medium and high voltage line up to and i/c 11,000 volts, if bare-4.572 m

(15ft.)


(b) For low, medium and high voltage lines up to and i/c 11,000 voltage. If insulated – 3.963 m (13 ft).

(c) For high voltage lines above 11,000 volts/ - 5.18 mt. (17 ft). 4. For extra high voltage lines, the clearance above ground shall not be less than

5.182 mt. (17 ft) plus 0.305 metres (1 ft) 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 at street shall not be less than 6.096 mets. (20 ft.)

I.E. Rule 79. Clearance from buildings of low and medium voltage lines and service lines.

1. Where a low or medium voltage overheads line passes and or adjacent to or terminates of any building, the following minimum clearance from any accessible point, on the basis of maximum sag shall be observed :- (a) For any flat roof open balcony, veranda roof, and loan to roof. (i)When the line passes above the building a vertical clearance of 2.435 metres (8 ft.) from the nearest point and (b) For pitched roof. (i)When the line passes above the building a vertical clearance of 2.439 mts. (8 ft.) immediately under the lines and (ii) When the line passes adjacent to the building a horizontal clearance of 1.219 mts. (4 ft.) (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 317.51 Kg. (700 Lbs). (3)The horizontal clearance shall be measured when the line is at a maximum deflection from the vertical due to wind pressure.

I.E. Rule- 80 (1) Clearance from buildings of high and extra high voltage lines.

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 line, up to and i/c 33,000 V- 3,658 mts.

I.E. Rule 81 CONDUCTOR OF DIFFERENT VOLTAGES ON SAME SUPPORT: Where conductors forming parts of system, 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 contact with the higher voltage system and the methods of construction and clearance between the conductors of the two system shall be subject to the prior approval of the Inspector. I.E. Fule 86

Conditions to apply where Telecommunication lines and power lines are carried on same supports:-

1. Every overheads Telecommunication line erected on supports carrying a power line shall consist of conductors each having a breaking strength of not less than 272.16 Kg. (600 Lbs.)

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 from contact, leakage or indication between such power and Telecommunication on lines.

I.E. Rule 87. Where two lines cross the crossing shall be made as nearly right angles as the nature of the case admits.

Danger Notice Plates I.S 2551-1963

2.1 Two sizes of danger notice plates are recommended:- (a) For medium voltage installation 200 x 150 mm (b) For high voltage & extra high 250 x 200 mm

2.2 The plate shall be made from mild steel at least 1.6mm thick and vitreous enamelled

white with letters, figures and the conventional skull and bones in signal red colour. Colours for ready mixed paints on the front side. The rear side of the plate shall also be enamelled.

NOTE:- 1- All letterings should be centrally spaced. NOTE:-II- All dimensions for the words in district language are mainly for guidance, however, care should be taken to space them centrally between the edges and the area of the skull and bones. NOTE:-III The location of the fixing holes shall be left to the choice of the user. NOTE:-IV- The corners of the plates should be rounded off. Danger plate for high and extra voltage as per I.S.


Galvanised Steel barbed wire for fencing I.S. 278-1962 Materials: 1. The wire shall be manufactured from steel made by the open hearth and electric

process shall not contain sulphur and phosphorous exceeding 0.065 per cent each. 2. The wires shall be coated with zinc of grade 98 of I.S. 205 –1956 specification for

zinc (revised). 3. The general conditions relating to testing, inspection and supply of materials shall

be in accordance with I.S. 1387-1959 General requirements for the supply of materials and metal products.

Manufacture and sizes (Types) 1.1 The galvanised steel barbed wire shall be of the following types:- Type Nominal dia. of wire. Nominal distances Between two barbs. Line wire Power wire Mm mm mm 1. 2.50 2.24 75 2. 2.50 2.24 150 3. 2.24 2.24 75 4. 2.24 2.24 150 1.2 The barbed wire shall be formed by twisting together two live wires, one containing

the barbs. The sizes of the line and point wires and barb spacings shall be as specified in figures.

1.3 Tolerances:- The permissible deviation from the nominal diameter of the line wire and the point wire shall not exceed + 0.08 mm.

1.4 The barbs shall carry four points and shall be formed by twisting two point wires, each two turns, tightly round one live wire making altogether four complete turns. The barbs shall be so finished that the four points are set and locked at right angles to each other (see figure below). The barbs shall have a length of not less than 13 mm and not more than 18 mm. The points shall be sharp and cut at an angle not greater than 35 degree to the axis of the wire forming the barbs.

Details of barbed wire

6.5 Coating Test- The uniformity of zinc coating shall be tested by the method specified in I.S. 429-1954 Methods for Testing weight and uniformity of Coating on Galvanised Iron and steel wires and steel sheets. The line and point wires shall withstand the number of dips specified below:-


Size of Wire 1-Minute Dip ½ Minute Dip Mm Line Wire (2.50 3 1 (2.24 3 1 Point Wire 2.24 1 --

6.6 If 20 per cent of more of the samples tested for zinc coating specified under 6.5 fail to comply with the requirements, additional tests shall be made on samples cut from four other reels selected at random from each lot of 50 reels or fraction thereof presented for inspection. If any one of the additional samples fail to stand the test, the entire let presented by the samples shall be rejected, as not complying with this standard. But if all the retest samples pass the test, the consignment shall be accepted.

Weight (Barbed Wire) The lengths per 100 Kg. Of the barbed wire shall be as given below:- Type Nominal Meter Min. Meter Maximum Meter. 1 1000 934 1066 2 1134 1066 1200 3 1575 1490 1668 4 1890 1778 2000

Making (Barbed Wire)

1. Every reel of barbed wire shall be marked legibly with attest the name of the manufacturer, diameters of the line and point wires, barb spacing and length and weight of the reel. 1.2 barbed wire may also be marked with ISI certification mark.

Coiling and Packing. 1. Unless otherwise agreed to between the supplier and the purchaser the barbed wire

shall be supplied in metal or wooden reels weighting maximum gross weight of 15 kg.

2. Each reel of barbed wire shall be wound and fastened compactly. I.E. Rule 76.

1. The minimum factor of safety for stay wires, guard wires or bearer wires shall be 2.5

based on the ultimate to tensile strength of the wire.

I.S. 1255 – 1967. Testing paper insulating for the presence of moisture:


Before jointing paper insulated cable, the power insulation should be tested for the presence of moisture by immersion in hot compound or paraffin wax at a temperature between 120 to 140 Degree Cel. The presence of moisture is indicated by the formation of bubbles when a piece of paper is immersed in hot compound, only a single strip of paper gripped by a pair of tweezers should be used for the test since if several thickness of paper are immersed, the escape of a occluded air between the layers may be mistaken for the presence. Of moisture. Particular attention should be paid to the paper next to the sheath and to that next the conductor, as it is in these positions that moisture is most likely to be found. The samples of paper should be handled as little as possible to avoid contamination particularly by perspiration. Methods for testing weights and uniformity of coating on Galvanised iron and steel wires and steel sheets. Determination of uniformity of coating (Presence Test) 5. SAMPLING

5.1 Steel sheets- samples shall be drawn as specified in the material specifications.

5.2 Wires- A length of more than 12 in. (or 305 mm) shall be cut from one or both ends of the selected coil. If the ends of the coil are obviously damaged, a length between one and two yards shall be cut off before the samples are taken. The sample shall be wound on a mandrel so that a length of at least 12 in. (or 305 mm) is fully coiled. In case of galvanised line wire for telegraph and telephone purposes; the mandrel shall have a diameter eight tames that of the wire if the wire is tested before being used for armouring, stranding or any other similar process, and eight times that of the wire if the wire is tested after being subjected to any such process. The sample shall then be unwound, roughly straightened and a length of 6 in. ( or 152 mm) cut from the middle of the portion that has been coiled and uncoiled.

5.3 The samples shall be clean. If necessary, they shall be washed with solvent naphtha or any suitable solvent, then with alcohol and finally dried thoroughly.

18. 6. REAGENTS

6.0 The following reagents are required. 6.1 Copper sulphate solution – Sp-gr 1.170 at 60 Degree F. Dissolve

approximately 33 g of crystalline copper sulphate (Cu SO4, SH20) in 100 ml of distilled water, shake the solution with an excess of copper carbonate of copper hydrate. Filter or allow to settle before use.

6.2 Rectified spirit (conforming to I.S. 323-1952) or petrol.


7. PROCEDURE

7.1 Subject the clean sample to as many successive dips as specified in the material specification in the copper sulphate solution having a uniform temperatures of 30 Degree + 1 Degree F- After each dip withdraw the sample, rinse it immediately in clean running water, wipe dry with a clean soft cloth, and except after the final dip, return immediately to the solution.

7.2 At the end of the specified number of dips when the sample is finally rinsed and wiped dry, it shall not show any red deposit of copper upon the base metal. In the case of wire, any deposit of metallic copper within one inch of the cut end of the sample shall be disregarded.

Note:- The depth of the solution shall be not less than 4 in. ( or 102 mm) and the internal diameter of the container shall in no case be less than 5 in. (63.5 mm) and in the case of wire samples of diameter larger than 1.252 in. (3 SWG) the internal diameter of the of the container shall be not less than 10 times the diameter of the sample. The container in which tests are to be made shall be of material inert to copper sulphate. Not more than three samples shall be immersed in the solution at one time and care shall be taken that the samples do not come in contact with one another or the sides of the container. There shall be no agitation of the solution during the immersion period. The solution shall be changed for unused solution after six samples have been tested in it.

cte extract

Documents