Handbook on Earthing system for power supply installations.pdf

CAMTECH/E/10-11/Earthing-PSI/1.0

ds oy dk;Z ky;hu mi;ks x gs rq 1

(For Official Use Only)

Hkkjr ljdkj GOVERNMENT OF INDIA js sy ea =ky; MINISTRY OF RAILWAYS a

IkkWoj lIykbZ la LFkkiukvks a dh dh vfFkZax Á.kkyh Á.kkyh ij gLriqfLrdk Lrdk Handbook on Earthing System For Power Supply Installations Yk{; lewg% g% VhvkjMh vuq j{k.k deZpkjh pkjh TARGET GROUP: TRD Maintenance Staff

dSeVs eVsd@bZ@10&11@vfFkZ ax&ih,lvkbZ@1-0 @1-0 CAMTECH/E/10-11/EARTHING-PSI/1.0

uoEcj 2010 November 2010

egkjktiqj , Xokfy;j Xokfy;j & 474 005 Handbook on Earthing Earthing System for for Power Supply Installation Installation Maharajpur, GWALIOR - 474 005

November 2010

2

CAMTECH/E/10-11/PSI/1.0

IkkWoj lIykbZ la LFkkiukvksa dh dh vfFkZx a Á.kkyh ij gLriqfLrdk Lrdk Handbook on Earthing System For Power Supply Installations

xq.koRrk uhfr jsyks yks es a es ;k=h a ;k=h vkSj eky ;krk;kr dh c<+ rh ek¡x dks iw jk djus ds ds fy, xq.koRrk Áca/k/k Á.kkyh es a vuql/kku] a/kku] fMtkbuks a vkSj ekudks a esa mRd`"Vrk rFkk lr~r lq/kkjks a ds ds ek/;e ls lkafof/kd fof/kd vkSj fu;ked vis{kkvks {kkvks a dks iw iw jk djrs gq gq, lqjf{kr] vk/kqfud vkSj fdQk;rh jsy ÁkS|ksfxdh fxdh dk fodkl djuk A QUALITY POLICY “To develop safe, modern and cost effective Railway Technology complying with Statutory and Regulatory requirements, through excellence in Research, Designs and Standards and Continual improvements in Quality Management System to cater to growing demand of passenger and freight traffic on the railways”. November 2010

Handbook Handbook on Earthing System System for Power Supply Supply Installation Installation


3

ÁkDdFku ÁkDdFku VhvkjMh ds lcLVs’ku ,oa fLofpax LVs’ku ’ku ¼ikWoj lIykbZ la LFkkiukvks a½ dh vfFkZax] x] midj.kks a ds lqpk# :Ik ls dk;Z dk;Z djus ,oa deZ deZpkfj;ks a ,oa midj.kks a dh lqj{kk ds fy;s cgqr egRoiw.kZ gSA ;g QkYV dja sV dks fuEu bEihMsUl Ul iFk Ánku djrk gS vkSj xzkmaM QkYV gksus us ij lqj{kk ;a =ks a dk Rofjr ,oa lqfuf’pr ifjpkyu lqfuf’pr djrk gSA dSeVsd us **IkkWoj lIykbZ la LFkkiukvksa dh vfFkZax Á.kkyh** ij ;g gLriqfLrdk cukbZ gS ftles a vfFka Zx dh la jpuk] d"kZ.k lcLVs’ku ’ku dh vfFkZ ax O;oLFkk] vuqj{k.k 'kSM~;w y] y] vuqj{k.k eqDr vfFkZ ax] ,DlksFkfeZ FkfeZd oSfYMax] D;k djs a vkSj D;k u djs a vkfn vkfn dk fooj.k fn;k x;k gSA eq> vk’kk s vk’kk gS fd ;g gLriqfLrdk VhvkjMh foHkkx es a dk;Z djus okys gekjs vuqj{k.k deZpkfj;ks a ds fy, mi;ksxh xh fl) gksxh A dSeVsd d]] Xokfy;j fnukad 24] fnlEcj] 2010

,l lh-lh ?ky ?ky ky ,l lh -lh -fla -fla?ky dk;Zdkjh funs’’kd kd

Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

4


FOREWORD

Earthing for substation and switching station (power supply installation) of TRD plays very important role in smooth functioning of equipment, safety of personnel and equipment. It provides low impedance path to fault currents and ensures prompt and consistent operation of protective devices during ground faults. CAMTECH has prepared this handbook on earthing system for power supply installation containing construction of earthing, earthing arrangement at traction substation, maintenance schedules, maintenance free earthing, exothermic welding and do’s & don’t. I hope this handbook will prove to be useful for the maintenance personnel working in TRD department.

CAMTECH, Gwalior

Date:24.12.2010

November 2010

S.C. Singhal Executive Director



5

Hkwfedk f fedk edk edk lcLVs’kuks ’kuks a ,oa fLofpax LVs’kuks ’kuks a es a Ik;kZIr vfFkZax dk Áko/kku ifjpkyu deZpkjh;ks a ,oa midj.kks midj.kks a dh dh lqj{kk ds fy;s fy;s vko’;d vko’;d gSA ;g Á.kkyh ifjpkyu dk dk;Z djus ds ds fy;s fy;s Hkh Hkh vko’;d gSA vfFkZax ds }kjk }kjk fo|q r midj.kks a dks dks i` i`Foh ds lkekU; lkekU; Hkkx ls tks tk M+ M s k+ tkrk t krk gS ftldk Áfrjks/k/k dkQh de gks rk gSA dSeVsd }kjk **IkkWoj lIykbZ la LFkkiukvks a dh vfFkZax Á.kkyh** ij ;g gLriqfLrdk gekjs vuq j{k.k deZpkjh;ks a dks vuqj{k.k Qzh vfFkZax ,oa ,Dlks ,DlksFkfeZ FkfeZd cSfYMax ds fo"k; es a voxr voxr djkus ds d mn~ s mn~ns’; ’; ls cukbZ cukbZ xbZ gSA ;g Li"V fd;k tkrk gS fd ;g gLriqfLrdk vkjMh,lvks] jsyos yos cksMZ MZ ;k ,lh VªsD’ku D’ku esuq uqvy }kjk fofuZfn"V fdlh Hkh fo/kku dks foLFkkfir ugha djrhA djrhA ;g gLriqfLrdk ds oy ekxZn’kZu gs rq gS ,oa ;g ,d oS/kkfud nLrkost+ t+ ugha ugha gS gSA eS]a dk;Z{ks { = ks ds d mu s mu lHkh deZpkfj;ks a dk dk vkHkkjh gw ¡ ftUgksus us bl bl gLriqfLrdk dks cukus cukus es es a gekjh gekjh lgk;rk dh A rduhdh mUu;urk vkSj lh[kuk ,d lrr~ izfØ;k gSA vr% bl gLriqfLrdk es a tksM+ M+u @ s @ lq/kkjus ds fy;s fy;s ges a fy[kus fy[kus es a Lora Lora = eglw l djs a A A bl fn’kk es a ge vkids ;ks ;ksxnku xnku dh ljkguk djs axAs dSeVsd] d] Xokfy;j fnukad 30] uoEcj] 2010

ih;w""k k xqIrk la- funs’kd ’kd ¼fo|qr½


November 2010

6


PREFACE

Provision of adequate earthing in substations and switching stations is essential for the safety of operating personnel as well as of equipment. It is also necessary for functioning of the system operation. By means of earthing, electrical equipment are connected to the general mass of the earth, which has a very low resistance. This handbook on earthing system for power supply installation has been prepared by CAMTECH with the objective of making our maintenance personnel aware of maintenance free earthing and exothermic welding. It is clarified that this handbook does not supersede any existing provisions laid down by RDSO, Railway Board or AC traction manual. This handbook is for guidance only and it is not a statutory document. I am sincerely thankful to all field personnel who helped us in preparing this handbook. Technological up-gradation & learning is a continuous process. Please feel free to write to us for any addition/ modification in this handbook. We shall highly appreciate your contribution in this direction.

CAMTECH, Gwalior Date: 30

November 2010

th

( Peeyoosh Gupta)

November 2010 Jt. Director Electrical e - mail id : [email protected] Handbook Handbook on Earthing System System for Power Supply Supply Installation Installation


7

h fo"k; lwp ph h ØØ - la laØ

1-0

2-0

fooj.k fooj.k çkDdFku Hkwfedk f edk fo"k; lw ph ph la’kks/ku /ku ifpZ; aks dk dk izdk’ku ÁLrkouk 1-1 lcLVs’ku dh vfFkZax ds mn~n’; s’; 1-2 vfFkZax Á.kkyh 1-3 ifjHkkf"kd 'kCnkoyh 1-4 xzkÅfUMax rFkk vfFkZax es a vUrj 1-5 mPpre vuqK;s vFkZ Áfrjks/k 1-6 vfFkZax dh lkekU; vko’;drk;s a 1-7 feV~Vh dh Áfrjks/kdrk /kdrk fu/kkZfjr djus okys okys dkjd lcLVs’ku ’ku ij vfFkZax O;oLFkk 2-1 vFkZ bYkSDVªksM 2-2 vfFkZax eSV fMt+ kbu dks ÁHkkfor ÁHkkfor djus okys okys dkjd 2-3 fMt+ k;u ÁfØ;k 2-4 vfFkZax eSV 2-5 xM+ h gqbZ jsy 2-6 flLVe vfFkZax 2-7 midj.k vfFkZax 2-8 vfFkZax pkyd dk lkbZt 2-9 fLofpax LVs’kuks a ij ij vfFkZax O;oLFkk


i`"B laiii v vii xi

01 01 02 02 06 07 07 09 15 15 17 17 18 20 21 22 29 29 November 2010

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CONTENTS Sr.No.

1.0

Description

Page No.

Foreword Preface Contents Correction Slip

iv vi viii xii

INTRODUCTION

01

1.1

PURPOSE OF SUBSTATION SUBSTAT ION EARTHING

01

1.2

EARTHING SYSTEM

02

1.3

TERMINOLOGY

02

1.4

DISTINCTION BETWEEN GROUNDING AND EARTHING

06

1.5

MAXIMUM PERMISSIBLE EARTH RESISTANCE

07

1.6

GENERAL REQUIREMENT FOR EARTHING

07

1.7

FACTORS WHICH DETERMINE RESISTIVITY RESISTIVIT Y OF SOIL

2.0

09

EARTHING ARRANGEMENTS AT SUBSTATION

15

2.1

EARTH ELECTRODES

15

2.2

PARAMETERS AFFECTING THE DESIGN OF EARTHING MAT

17

2.3

DESIGN PROCEDURE

17

2.4

EARTHINGMAT

18

2.5

BURRIED RAIL

20

2.6

SYSTEM EARTHING

21

2.7

EQUIPMENT EARTHING

22

2.8

SIZE OF EARTHING CONDUCTOR

29

2.9

EARTHING ARRANGEMENT ARRANGEME NT AT SWITCHING STATION

29

November 2010



ØØ - la laØ 3-0

4-0

5-0

6-0

fooj.k fooj.k

9

i`"B la-

ijEijkxr vFkZ bysDVª DVªksM dk vuqj{k.k 3-1 =Sekfld vuq j{k.k 3-2 v)Z okf"kZd vuqj{k.k 3-3 okf"kZd vuq j{k.k 3-4 vFkZ bySDVªkM s ds Áfrjks Áfrjks/k dk ekiu 3-5 gLr pkfyr vFkZ Vs LVj dk fooj.k vuqj{k.k eqDr Dr vfFkZ ax 4-1 vFkZ Áfrjks/k/k 4-2 mi;ksx 4-3 vuqj{k.k eqDr Dr vfFkZ ax Á.kkyh ckWfUMax] x] xzkmfUMax@ vfFkZax ds fy, fy, ,DlksFkfeZ FkfeZd oSfYMax la;kstu 5-1 lkekU; vko’;drk;s a 5-2 osfYa fYaMx Mx lkexzh 5-3 osfYa fYaMx Mx VwYl dh fof’k"Vrk;s a 5-4 osfYa fYaMx Mx vkSt kj + D;k djs a vkS vkSj D;k u djs a 6-1 D;k djs a 6-2 D;k u djs a ifjf’k"V&1 ,SDlksFkfeZ FkfeZd osfYa fYaMx Mx çfØ;k ds Nk;kfp= Nk;kfp= ifjf’k"V&2 jsy es a fNnz djus dh dh çfØ;k ds Nk;kfp= Nk;kfp= ifjf’k"V&3

32 32 33 34 34 36 38 38 39 39 49 50 51 52 54 57 57 58 59 62 63

jsy es a fMªfyax djus dh dh e’khu dh fof’k"Vrk;s a lanHkZ nHkZ Handbook on Earthing Earthing System for for Power Supply Installation Installation

68 68 November 2010

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Sr. No. 3.0

3.5

5.0

6.0

Page No.

MAINTENANCE SCHEDULE OF CONVENTIONAL EARTH ELECTRODE 3.1 3.2 3.3 3.4

4.0

Description

QUARETLY SCHEDULE HALF YEARLY SCHEDULE YEARLY SCHEDULE MEASUREMENT MEASUREMENT OF EARTH ELECTRODE RESISTANCE DETAILS OF EARTH TESTER (HAND DRIVEN)

32 32 33 34 34 36

MAINTENANCE FREE EARTHING

38

4.1 4.2 4.3

38 39 39

EARTH RESISTANCE APPLICATION MAINTENANCE FREE EARTHING SYSTEM

EXOTHERMIC WELDING CONNECTION FOR BONDING, GROUNDING/ EARTHING

49

5.1 5.2 5.3 5.4

50 51 52 54

GENERAL REQUIREMENTS REQUIREMENT S WELDING MATERIAL SPECIFICATION OF WELDING TOOLS WELDING TOOLS

DO’S & DON’TS

57

6.1

DO’ S

57

6.2

DON’T

58

ANNEXURE-1

Photographs of Exothermic Welding Procedure

59

ANNEXURE-2

Photographs of Process of Hole Drilling in Rail

62

ANNEXURE-3

63

Specification of Rail Drilling Machine REFERENCES

November 2010


68


11

la’kks ’kks/ku /ku ifpZ; aks dk dk izdk’ku k’ku bl gLriqfLrdk ds fy;s Hkfo"; es a izdkf’kr gksus okyh la’kks ’kks/ku /ku ifpZ; aks dks dks fuEukuq lkj la[;ka [;kafdr fdr fd;k tk;sxkA xkA ------dSeVsd@bZ d@bZ@10-11@ @vfFkZ ax x -ih,lvkbZ@ @1@ lh,l # XX fnuka fnukad d ------11@vfFkZ @11-0 -00@

tgkWa “XX” lEcfU/kr la’kks ’kks/ku iphZ dh dze la[;k [;k gS ¼ 01 ls izkjEHk gksdj vkxs dh dh vks j½ izdkf’kr la’kks ’kks/ku /ku ifpZ;k¡ dz la -la -la-

izdk’ku dk’ku dh rkjh[k rkjh[k

la la’kks ’kksf/kr f/kr Ik`""B B la[[;k ;k rFkk en la[;k [;k [;k ;k


fVIi.kh fVIi.kh

November 2010

12


ISSUE OF CORRECTION SLIP The correction slips to be issued in future for this handbook will be numbered as follows: CAMTECH/E/10-11/Earthing-PSI/1.0/ CAMTECH/E/10-11/Earthin g-PSI/1.0/ C.S. # XX date--Where “XX” is the serial number of the concerned correction slip (starting from 01 onwards).

CORRECTION SLIPS ISSUED Sr. No.

November 2010

Date issue

of Page no. and Item no. modified

Remarks



1.0

1

ÁLrkouk @INTRODUCTION Provision of adequate earthing in substations and switching stations is essential for the safety of operating personnel as well as of equipment. It is also necessary for functioning of the system. By means of earthing electrical equipment are connected to the general mass of the earth, which has a very low resistance.

1.1

lcLVs’ku ’ku dh vfFk vfFkZ a Zx ds mn~n’;@ s’;@ ’; ;@PURPOSE

OF

SUBSTATION EARTHING The object of an earthing system in a substation is to provide, under and around the substation a surface that shall be at a uniform potential and as near to zero or absolute earth potential as possible. The provision of such a surface of uniform potential under and around the substation ensures human safety from electric shock in case of short circuit or development of any abnormal condition in the equipment installed. The primary requirements of a good earthing system in a substation are: a.

It stabilizes circuit potential with respect to ground and limits the overall potential rise.

b.

It protects life and property from over voltage.

c.

It provides low impedance path to fault currents to ensure prompt and consistent operation of protective devices during ground faults.

d.

It keeps the maximum voltage gradient along the surface inside and around the substation within safe limits during ground fault.


November 2010

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1.2


vfFkZax Á.kkyh @EARTHING SYSTEM All the non current carrying parts of the electrical equipment in the substation are connected to the earthing mat. Under normal conditions the ground rods contribute a little towards lowering the ground resistance. It maintains a low value of resistance under all weather conditions. The mat is connected to the following equipment in sub station: a. The neutral neutral point of system through through its own independent earth. b. Equipment frame work and other other non current carrying parts. c. All extraneous metallic associated with equipment.

frameworks

not

d. Lightning arrestors through their independent earths. e. Handles of operating pipes. f.

1.3

Fence if it is within 2m from earth mat.

ifjHkkf"kd 'kCnkoyh@TERMINOLOGY The following terms are commonly used in earthing system:

1.3.1

Hkw@ Earth The conductive mass of the earth, whose electrical potential at any point is conventionally taken as zero.

November 2010



1.3.2

3

vFkZ bY bYkS kSDVª M@ ksM@ M Earth electrode A galvanized iron (GI) pipe or group of pipes in intimate contact with and providing an electrical connection to earth.

1.3.3

vFkZ Z fxzM@Earth grid vFk A system of grounding electrodes consisting of inter-connected connectors buried in the earth to provide a common ground for electrical devices and metallic structures.

1.3.4

vFkZ ZZ eSV@Earth Mat vFk A grounding system formed by a grid of horizontally buried conductors and which serves to dissipate the earth fault current to earth and also as an equi-potential bonding conductor system.

1.3.5

vfFkZax midj.k midj.k@ @ Equipment Earthing It comprises earthing of all metal work of electrical equipment other than parts which are normally live or current carrying. This is done to ensure effective operation of the protective gear in the event of leakage through such metal work, the potential of which with respect to neighboring objects may attain a value which would cause danger to life or risk of fire.

1.3.6

flLVe flLVe vfFkZ ax@ x x @

System Earthing

Earthing done to limit the potential of live conductors with respect to earth to values which the insulation of the system is designed to withstand and this to ensure the security of the system.


November 2010

4

1.3.7


LVsi ,oa Vp Vp oksYVrk YVrk @Step & Touch Potential Step & touch potential refer to the potential experienced by a person standing on a surface when earth mat buried up to 750 mm below, surface has risen to ground potential rise (GPR). Touch potential is the difference between GPR & the surface potential at the point where person is standing, while his hand is in contact with grounded structure. Step potential is the difference in surface potential experienced by a person bridging a distance of one meter with his feet without contacting any other grounded object as shown in figure - 1

Figure 1

If resistance offered by each foot is R, then for step potential the resistance is 2R while for touch potential is R/2. November 2010



1.3.8

5

eS’k oksYVrk@ YVrk@Mesh Voltage (E mesh) The maximum touch voltage to be found within a mesh of an earthing grid.

1.3.9

fu/kkZfjr oksYYVrk@ Vrk@Nominal Voltage Voltage for which an installation is designed.

1.3.10

ykbZo fgLlk@Live part A conductor or conductive part intended to be energized in normal use.

1.3.11

MSM@Dead The term used to describe a device or circuit to indicate that a voltage is not applied.

1.3.12

U;wVª V ªy pkyd@Neutral conductor A conductor connected to the neutral point of a system and is capable of contributing to the transmission of electrical energy.

1.3.13

fo|qr lIykbZ la LFkkiuk k@ LFkkiu kk k@ Power Supply Installation The electrical equipment and associated structure provided at traction substation or switching station are connected to the 25 kV Over Head Equipment.

1.3.14

Hkw foHko foHko dk cc<

November 2010

6


xz kÅ kkk ÅfUMa Å Å fUMa x rFkk vfFkZax es a vUrj@DISTINCTION

1.4

BETWEEN GROUNDING AND EARTHING 1.4.1

xzkÅfUMax x @ @Grounding Grounding implies connection of current carrying parts to ground. It is mostly either generator or transformer neutral. Hence it is generally called neutral grounding. grounding. Grounding is for equipment safety. s afety. There are three requirements for grounding: a.

b. c. 1.4.2

Shall provide a low impedance path for the return of fault current, so that an over current protection device can act quickly to clear the circuit. Shall maintain a low potential difference between exposed metal parts to avoid personnel hazards. Shall control over voltage.

vfFkZax x @ Earthing Earthing implies connection of non current carrying parts to ground like metallic enclosures. Earthing is for human safety. Under balanced operating conditions of power systems, earthing system does not play any role. But under any ground fault condition, it enables the ground fault current to return back to the source without endangering human safety as as shown in figure - 2 GENERATOR

Figure 2

TRANSFORMER

NEUTRAL GROUNDING

NEUTRAL GROUNDING

EARTHING

November 2010



1.5

mPpre mPpre

vuqK; s

7

vFkZ

Áfrjks/k@ /k@MAXIMUM

PERMISSIBLE EARTH RESISTANCE At each power supply installation the combined resistance of the earthing system shall not be more than the following values:i) Traction Sub Station - 0.5 Ohms ii) Switching Station iii)

1.6

- 2.0 Ohms

BT and AT station

- 10 Ohms

vfFkZax dh x dh lkekU; vko’;drk;s a x GENERAL REQUIREMENTS FOR EARTHING Earthing shall generally be carried out in accordance with the requirement of I.E. rules, 1956, as amended from time to time and the relevant regulation of the electricity supply. Codes /Standard given below may also be referred : i) IS:3043-1987 IS:3043-1987 - Code of practice for earthing (latest) ii) National Electricity Code - 1985 of Bureau of Indian Standards iii) IEEE guide for safety in a.c. substation grounding No. ANSI/IEEE standard 801986. iv) Indian Electricity Rule – 1956 (Latest edition) In cases where direct earthing may prove harmful rather than providing safety, relaxation may be obtained from the competent authority. Earth electrodes shall be provided at substations, switching stations and consumer premises in accordance with the requirements. 



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November 2010

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







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November 2010

As far as possible all earth connections shall be visible for inspection. All connections shall be carefully made. If they are not properly made or are inadequate for the purpose for which they are intended, loss of life or serious personnel injury may result. Each earth system shall be so devised that the testing of individual earth electrode is possible. It is recommended that the value of any earth system resistance shall not be more than specified value. The minimum size of earthing lead (discharge rod cable) used on installations shall have a nominal 2 cross-section area not less than 40 mm multi stranded copper to be able to withstand short circuit current. It is recommended drawing showing the main earth connection and earth electrode be prepared for each installation. No addition to the existing load whether temporary or permanent shall be made, which may exceed the assessed earth fault or its it s duration until it is ascertained that the existing arrangement of earthing is capable of carrying the new value of earth fault current resulting due to such addition. All materials, fittings etc. used in earthing shall confirm to Indian Standard specification wherever these exist. In the case of material for which Indian Standard specifications does not exists, the material shall be approved by the competent authority. Handbook Handbook on Earthing System System for Power Supply Supply Installation Installation


1.7

9

feV~ ~Vh V~ h dh Áfrjks/kdrk /kdrk fu/kkZfjr djus o okys kys dkjd dkjd@ @ feV Vh FACTORS WHICH DETERMINE RESISTIVITY OF SOIL The resistivity of soil for earthing system depends upon the following factors: Type of soil Moisture content Chemical composition of salt dissolved in the contained water Concentration of salt Temperature of material Grain size and distribution of grain size Size and spacing of earth electrodes

  

   

1.7.1

feV~ ~Vh V~ h dh Áfrjks//kdrk kdrk de djus dh feV fof/k;k¡@Methods of Reducing Resistivity of Soil feV~ ~Vh V~ h dh Áfrjks/kdrk /kdrk ds Ádkj@Types feV

of

soil

resistivity S.No

Type of soil

Resistivity in Ohm-cm 500 - 5000

1

Loamy garden soil

2

Clay

3

Clay, Sans and Gravel mix

4000 - 25000

4

Sand and Gravel

6000 - 10000

5

Slates, Slab sand stone

1000 - 50000

6

Crystalline Rock


800 - 5000

20000 - 100000

November 2010

10

1.7.2


feV~Vh mipkj@Soil Treatment a.

When the soil resistance is high, even the multiple electrodes in large number may also fail to produce low resistance to earth. To reduce the resistivity of soil immediately surrounding the electrode some salt substances are made available as a solution with water. The substances are used salt sodium chloride (NaCl), Calcium chloride (CaCl2) Sodium carbonate (Na2CO3), copper sulphate (CuSO4) and soft cock and charcoal in suitable proportion.

b. Nearly 90% of resistance between electrode and soil is with in a radius of two meters from electrode/ rod. Treating this soil will result in required reduction in earth resistance by excavation of one meter diameter around top of the electrode/ rod to 30 cm deep and applying artificial soil treatment agency and watering sufficiently. c.

General practice to treat the soil surrounding the ground electrode with common salt, charcoal and soft cock in order to bring down the earth resistance. These conventional methods are effective in soils of moderately high resistivity up to 300 ohm-meter. When the soil resistivity exceeds this value, these conventional methods of chemical treatment will be inadequate to get desired value of earth resistance.

November 2010



1.7.3

11

feV~Vh Vh mipkj es a csc ssUVks UVksukbZ ukbZV dk mi;ksx x @Use

of

Bentonite in Soil Treatment 









1.7.4

Bentonite is clay with excellent electrical properties. It swells to several times its original volume when suspended in water. It binds the water of crystallization and the water absorbed during the mixing process is retained over a long period. Bentonite suspension in water when used to surround the earth electrode virtually increases the electrode surface area. Use of bentonite around the earth electrode results in reduction of ground resistance by about 25- 30 %. Bentonite has a tremendous capacity to absorb water and retain it over along period. Even during the summer months, bentonite suspension retains the moisture where as the natural soil dries up. Bentonite may be used to advantage in rocky terrain.

feV~Vh Vh mipkj es eghu jk[k dk mi;k mi;ks sx mipkj es a eghu x s @Use of fly ash in soil treatment

As per CPRI studies reveals that fly ash from thermal stations has equivalent chemical composition and hence can be used for the electrical installations in areas of high ground resistivity. Fly ash can also be used as a chemical treatment material to reduce soil resistivity.


November 2010

12

1.7.5


vFkZ Áfrjks//kdrk kdrk ij vknz rk rk dk ÁHkko @Effect

of

Moisture Content on Earth Resistivity

Moisture content is expressed in percentage by 3 weight of dry soil. Dry earth weights about 1440 kg/m . Therefore about 144 kg (10%) of water is required per cubic meter of soil to have 10% of moisture content. About 20% moisture the resistivity is very little affected below 20% moisture the resistivity increases very abruptly with decrease in moisture. Moisture content of about 17% to 18% by weight of dry soil is the optimum requirement. Availability of moisture assists formation of electrolyte by dissolving salt content in soils and there by enhance the conductivity of soil. More water content can not improve soil resistivity. Moisture content(% by weight)

0 2.5 5 10 20 30 1.7.6

Resistivity(Ohm-cm) Top Soil Sandy Loam 6

1000x10 250000 165000 53000 12000 6400

1000x10 150000 43000 18500 6300 4200

6

rki dk ÁHkko@ ÁHkk o@Effect of Temperature The temperature coefficient of resistivity for soil is negative, but is negligible for temperatures above 0 freezing point. At about 20 C the water in the soil begins to freeze and introduce a tremendous increase in the temperature coefficient. The resistivity changes 9% per degree C. Below 0 degree C resistivity raises abnormally.

November 2010



13

Effect of Temperature on Resistivity Resi stivity 0

C 20 10 0 0 -5 -15 1.7.7

0

F 68 50 32(Water) 32(Ice) 23 14

Resistivity(Ohm-cm) 7,200 9,900 13,000 30,000 79,000 330,000

vFkZ Áfrjks/kdrk /kdrk dk tax x ij ÁHkko@Effect

of Soil

Resistivity on Corrosion

Resistivity plays an important role in so far as the corrosion performance of earthing rods is concerned. It is observed that soils having resistivity of less than 25 ohm-meter are severely corrosive in nature while corrosion rate is of less importance in soils of resistivity over 200 ohm- meter. The methods adopted to safe guard earthing conductors against corrosion depends upon a. Material of the conductor b. Corrosivity of the soil c. Size of the grounding system Range of soil resistivity (Ohm-metre)

Class of soil

Less than 25

Severely corrosive

25 – 50

Moderately corrosive

50 -100

Mildly

Above 100

Very mildly corrosive


November 2010

14

1.7.8


lrg ij iRFkj iR Fkjj pw jk dh d h irZ i rZ ds iRFk d Qk;ns s Qk;ns@Advantages of Crushed Rock Used as a Surface Layer • It provides high resistivity surface layer • It serves as impediment to the movement of reptiles and there by help in minimizing the hazards which can be caused by them • It prevents the formation of pools of oil from oil insulated and oil cooled electrical equipment • It discourages the growth of weeds • It helps retention of moisture on the underlying soil and thus helps in maintaining the resistivity of the subsoil at lower value. • It discourages running of persons in the switchyard and saves them from the risk of being subjected to possible high step potentials.

1.7.9

iRFkj pw jk dh eghu irZ dk ÁHkko@Effect of Thin Layer of Crushed Rock

In outdoor switchyard, a thin layer of crushed rock is spread on the surface. The resistivity of gravel (ρ ( ρ) is 2000 ohm-meter while that of soil is 100 ohm-meter. Since ρ of gravel is high, only a high voltage can force the current through the body to cause injuries. The gravel act like insulator & throws the electric field generated by GPR back to soil. 1.7.10

vFkZ bYkSDVªksM yxkus dk dk LFkku@ LFkk u@Location of Earth Electrode

The location of earth electrode should be chosen in one of the following types of soil in the order of preference given on next page: November 2010



15

a. Wet marshy ground. b. Clay, loamy soil and arable land c. Clay and loam mixed with varying proportions of sand, gravel and stones. d. Damp and wet sand, peat. Dry sand, gravel chalk limestone, granite, very stone ground and all locations where virgin rock is very close to the surface should be avoided.

2.0

lcLVs’ku ’ku

ij ij vfFkZax x O;oLFkk@EARTHING

ARRANGEMENTS AT SUB STATION 2.1

vFkZ bY bYkS kSDVª M@ Earth Electrodes ksM The earth electrodes are made of mild steel galvanized perforated pipe of not less than 40 mm nominal bore, of about 4 m length provided with a spike at one end and welded lug suitable for taking directly MS flat of required size at the other end. The pipe is embedded as far as possible vertically into the ground, except when hard rock is encountered, where it may be buried inclined to the vertical, the inclination 0 being limited to 30 from the vertical. The connection of MS flat to each electrode is made through MS links by bolted joints to enable isolation of the electrode for testing purpose. Earth electrodes shall be embedded as apart as possible from each other. Mutual separation between two electrodes shall not be less than 6.0 m i.e. twice the length of the electrode as shown in figure- 3 In high embankments, it may be difficult to achieve earth resistance even after chemical treatment of electrodes. In these locations, use electrodes longer than 4 m so as to reach the parent soil is recommended.


November 2010

16


As far as possible, earth electrodes for traction substation/ switching stations shall be installed within and adjacent to perimeter fence. 0 5

0 0 5 3

5 7 1 L L E W E B O D T E A M E M R A A R

X O B ) C H C R T ( R A E

0 5

E D O R H T T C R E A L E E

A I D S E m L m 2 O 1 H

n r e t v e i r t e d b r e o f m l i o o g t n i e s d p e l i o t h P h

0 0 2

0 0 2 X O B ) C H C T R R ( A X E 0 R 8 O F D I L

0 5 1

0 5 1

0 0 0 0 2 5

D 0 N 0 A 2 S K C F I H O T R m E m Y A 0 L 5

L E V E L D N U O R G

m m m 8 m m m X 0 1 2 m X 1 m X 5 m m 7 m m X 0 0 0 2 1 8

0 5 3

0 5 l k a t , c u l o c q a r e s o f l e t o a a s o n c r r r e e y a t l a h A L c

S E H L T O R G O H R F N E A A L I I G D L N E I M I C I R m S A T m T P N 2 A 1 S E

5 7

5 7

5 7

5 7

D E D L G E 4 . N m W 8 m O 8 4 T L A X L m F m m . S 0 m . 5 5 1 7 M

0 5 1

0 5 1

0 51 0 0 0 3

Figure -3 November 2010



2.2

17

vfFkZ kZx a eSV fMt+ kbu ÁHkkfor ÁHkkfo r djus dj us okys okys dkjd@ dkjd@ vfF kbu dks ÁHkkfor PARAMETERS AFFECTING THE DESIGN OF EARTHING MAT Several variable factors are involved in the design of earthing mat conductor. Earthing mat for each substation has to be designed individually. The earthing mat has to be designed as per the site conditions to have low overall impedance and a current carrying capacity consistent with the fault current magnitude. The following parameters influence the design of earthing mat: 1. Magnitude of fault current 2. Duration of fault 3. Soil resistivity 4. Resistivity of surface material 5. Shock duration 6. Material of earthing mat conductor 7. Earthing mat geometry

2.3

fMt+ k;u +k+ ;u ÁfØ;k@ DESIGN PROCEDURE fMt The following steps are involved in the design of earthing mat: i.

The layout of the sub station, determine the area to be covered by the earthing mat.

ii.

Determine the soil resistivity at the sub station site. The resistivity of the earth varies within extremely wide limits, between 1 and 10,000 ohm-meter. The resistivity of the soil at many station sites has been found to be nonuniform. Variation of the resistivity of the soil with depth is more predominant as compared to the variation with horizontal distances. To design


November 2010

18


the most economical and technically sound grounding system for large stations, it is necessary to obtain accurate data on the soil resistivity and on its variation at the station site. Resistivity measurements at the site will reveal whether the soil is homogeneous or nonuniform. In case the soil is found uniform, conventional methods are applicable for the computation of earth resistivity. When the soil is found nonuniform, either a gradual variation or a two-layer model may be adopted for the computation of earth resistivity.

2.4

vf vfFk FkZ Zx eS aZx eSV @ EARTHING MAT ff Fk x An earthing mat is formed by means of bare mild steel rod of appropriate size buried at a depth of about 600 mm below the ground level and connected to earth electrodes. The connection between the earth electrodes and the mat shall be by means of two separate and distinct connections made with 75 mm x 8 mm MS flat. The connection between the MS flat and the MS rod shall be made by welding, while that between the earth electrode and the MS flats through MS links by bolted joints. The earth electrodes are provided at the outer periphery of the mat. As far as possible the earthing mat conductors shall not pass through the foundation block of the equipment. All crossings between longitudinal conductors and transverse conductors are jointed by welding. The longitudinal and transverse conductors of the earthing grid shall be suitably spaced so as to keep the step and

November 2010



19

touch voltage within the acceptable limit. However the overall length of the earthing grid conductors shall not be less than the calculated length as shown in figure– 4.

M S FLAT

MS ROD

EARTH ELECTRODE

E C N E F F O E R T E M 1 N I H T I W R O T C U D N O C D I R G D E I R U B

TRACTION SUB.-STN. FENCIG

75 mm X 8mm MS FLATS FROM POWER TRANSFORMER SECONDARY WINDING TERMINAL

WELDED AT CROSSING

BURIES RAIL

Figure - 4

75 mm X 8mm MS FLATS TO NON TRACK CIRCUITED RAIL NEUTRAL POINT OF IMPEDANCE BOND


November 2010

20


The size of the earthing grid conductors are decided based on the incoming system voltage and fault level. The fault level considered is taking into account the anticipated increase in fault current during the life span of the station. The system voltage, fault level and conductor size are given below: Sr. No

Fault level (MVA)

Diameter of grid conductor (GI rod) in mm

66

upto 4000 above 4000 upto 5000 above 5000 upto 6000

32 36 40

2

110


32 36 40

3

132

upto 7000 above 7000 upto 10000

32 36

220


32 36 40

1

4

2.5

System voltage (KV)

xM+ xM h + gqbZ jsjsy y@ @BURIED RAIL A steel rail of section 52 kg/m (the one used for the railways track) and length about 13 m is buried near the track at the traction substation at a depth of about one meter to form part of the earthing system. Two separate and distinct connections are made by means of 75 mm x 8 mm MS flat between the earthing mat and the buried rail. The buried rail are connected by means of two separate and distinct connections made with 75 mm x 8 mm MS flat to the traction rail(s) in a singlerail track circulated section and to the neutral points(s)

November 2010



21

of the impedance bond(s) in a double-rail track circuited section. In case where the feeding post is located separately away from the traction substation, the buried rail is provided at the feeding post (where one terminal of the secondary winding of the traction transformer of the substation is grounded).

2.6

flLVe vf fFk FkZ a Zx@ SYSTEM EARTHING flLVe vf fFk x Zx @ One terminal of the secondary winding (25 kV winding) of each traction power transformer are earthed directly by connecting it to the earthing grid by means of of one one 75 mm x 8 mm MS flat , and to the buried rail by means of another 75 mm x 8 mm GI flat as shown figure in - 5

Figure- 5

One designated terminal of the secondary of each potential, current and auxiliary transformer are connected to the earthing grid by means of two separate and distinct earth connection made with 50 mm x 6 mm MS flat as shown in figure in 6,7& 8.

Figure - 6

Figure - 7


Figure - 8 November 2010

22

2.7 2.7.1


midj.k v vf f fFk Zax @ EQUIPMENT EARTHING fFkZ Fk x@ ikWoj VªkUlQkeZj dh vf vfFk FkZ Zx@ x a @ Earthing of ff Fk

Power

Transformer The metallic frame work (tank) of each power transformer is directly connected to the main earthing mat by means of two separate distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side and 75 mm x 8 mm MS flat for the primary side. One connection is made with the nearest longitudinal conductor, while the other is made to the nearest transverse conductor of the mat.

Figure - 9

In addition there is a direct connection from the tank to the earth side of lightning arrestors. The transformer tank rails are earthed either separately or by bonding at each end of the track as shown in figure- 9. 2.7.2

lfdZV zcsdj rFkk buVªIVj x @ Vj dh vfFkZax

Earthing of

Circuit Breakers and Interrupter

The supporting structures of each circuit breaker unit are connected to the earthing mat by means of two separate distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side and 75 mm x 8 mm MS flat for the primary side. One connection is made with the nearest longitudinal conductor, while the other is made to the nearest transverse conductor of the mat. Cubicles, doors and cable glands are also connected to the earthing mat as shown in figure – 10 & 11. November 2010

Figure -10 & 11 .



2.7.3

23

vkblksy yssVj Vj dh vf vfFk FkZ Zax@ x@ Earthing of Isolators of Isolators ff Fk A flexible earth conductor is provided between the handle and earthing conductor attached to the mounting bracket and the handle of switches is connected to earthing mat by means of two separate distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side and 75 mm x 8 mm MS flat for the primary side .One connection is Figure -13 made with the nearest longitudinal conductor, while the other is made to the nearest transverse conductor of the mat as shown in figure – 12 & 13

2.7.4

ykbfVax vjs v js LVj js dh vf vfFk FkZ Zax@ x Earthing of Lightning ff Fk Zx @ Arrestor

In addition to the earth electrodes provided for the main earthing mat, an independent earth electrode is provided for each lightning arrester. This earth electrode is connected to the ground terminal of the lightning arrester, as well as to the main earthing mat by means of two separate distinct Fi ure -1 -14 connections made with 50 mm x 6 mm MS flat for the 25 kV side lightning arresters, and with 75 mm x 8 mm MS flat for the primary side lighting arresters. The earth electrode is provided as close as possible to the lightning arrester and the


November 2010

24


connection shall be as short and straight as possible avoiding unnecessary bends. For lightning arresters provided for the traction power transformers, there is also be a connection as direct as possible from the ground terminal of the lighting arrester to the frame of the transformer of the being protected. This connection is also be made by two separate and distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side lightning arresters, and with 75 mm x 8 mm MS flat for the primary side lighting arresters as shown in figure- 14 2.7.5

djs aV ,oa iksVs VfU’k;y sfU’k;y VªkUlQW W keZ kW eZj UlQ vf vfFk FkZ Zx@ x a @Earthing of Current Transformer ff Fk

dh and

Potential Transformer

The supporting structures of Current Transformer and Potential Transformer unit of bases, all bolted cover plates to which the bushings are attached connected to the earthing mat by means of two separate distinct connections made with 50 mm x 6 mm MS flat for the 25 kV side and 75 mm x 8 mm MS flat for the primary side. One connection is made with the nearest longitudinal conductor, while the other is made to the nearest transverse conductor of the mat as shown in figure – 15 & 16 Figure -15& 16

November 2010



2.7.6

25

daVVªªksy :e ds vUnj dh v vf fFk FkZ Zax@ x@ Earthing inside ff Fk Control Room

An earthing ring shall be provided inside the control room by means of 50 mm x 6 mm MS flat which shall be run along the wall on teak wood blocks fixed to the wall at a height of about 300 mm from the floor level as shown in figure- 17. The earthing ring is connected to the main earthing grid by means of two separate and distinct connections made with 50 mm x 6 mm MS flat. The earthing ring is also be connected to independent earth electrode by means of two separate and distinct connections made with 50 mm x 6 mm MS flat as shown in figure – 18.

Figure - 17

Figure- 18

The metallic framework of control and relay panels, LT AC and DC distribution boards, battery chargers, remote control equipment cabinets and such other equipment are connected to the earthing ring by means of two separate and distinct connection made with 8 SWG galvanized iron wire. The connections are being taken along the wall and in the floor. All recesses shall be covered with cement plaster after finishing the work. Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

26


Connection between the MS flats is made by welding as shown in figure – 19, 20, 21& 22.

Figure- 19

Figure- 21

November 2010

Figure - 20

Figure- 22



2.7.7

27

vU; midj.kks a dh dh v vf f fFk Zax@ x@ Earthing of other fFkZ Fk Equipment a.

vFkZ LØhu dh vfFkZax@ x@ x Earthing of Earth Screen The area covered by outdoor substation are shielded against direct strokes of lightning by an overhead earth screen comprising 19/2.5 mm galvanized steel standard wire strung across the pinnacles of the metallic Figure- 23 structures. The earth screen wires are strung at a height as indicated in the approved traction substation layouts (not less than 2.5 m above the live conductor) and shall be solidly connected to the traction substation earthing grid at each termination by means of 50 m x 6 mm GI flat as shown in figure – 23.

b.

QsfUla fUlax LraHkks Hkks a vkSj isuyks uyks a dh vf vfFk FkZ Zax@ @ ff Fk x Z a x Earthing of fencing uprights and panels

Each metallic fencing upright is connected to the traction substation main earthing grid by means of two separate and distinct connections made with 50 Fi ure- 24 24 mm x 6 mm MS flat. In Figure- 24 addition, all the metallic fencing panels shall be connected c onnected to the uprights Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

28


by means of two separate and distinct connections made with 6 SWG G I wire. The entire metallic door panels are also be connected to the supporting uprights by means of two distinct connections made with Figure- 25 6 SWG I wire as shown in figure- 24 & 25 All metallic part of structures, masts and metallic frames is connected to the traction substation main earthing mat by means of two separate Figure- 26 and distinct connections made with 50 mm x 6 mm MS flats shown in figure- 26. 2.7.8

vkW;y fQYVjs’ku ’ku IykaV ds V ds fy, 240 oksYV YV ,lh 50 V gVZt ds ikW ikWbVa dh vf vfFk FkZ Zx@ x a @ Earthing at the point ff Fk of 240 V ac 50 Hz supply for oil filtration plant

The 240 V ac 50 Hz distribution board for power supply to oil filtration plant is connected to the main earthing grid by means of two distinct connections made with 50 mm x 6 mm MS flat as shown in figure - 27 November 2010

Figure- 27



2.8

vf vfFk FkZ Zx a pkyd dk lkbZ Zt@SIZE ff Fk lkb

29

OF EARTHING

CONDUCTOR Size of earthing conductor depends on system voltage and fault level as given below: Sr. No 1

2.9

Equipment (KV) Equipment on the primary side of traction power transformer

System voltage and Ground fault level conductor size 66 KV, upto 3000 MVA 50mm x 6mm 110 KV, upto 5000 MVA 132 KV, upto 6000 MVA 220 KV, upto 10000 MVA

66 KV, above 3000 upto 6000 MVA 110 KV, above 5000 upto 10000 MVA 132 KV, above 6000 upto 12000 MVA 220 KV, above 10000 pto 20000 MVA

75mm x 8mm

2

Equipment on the secondary side of traction power transformer

50mm x 6mm

3

Fencing uprights/steel uprights/ste el structures

50mm x 6mm

4

Doors/fencing Doors/fenci ng panels

6 SWG G I wire

Lofpa fLofpa kuks a ij vf vfFk FkZ Zx a O;oLFkk@EARTHING ff x LVs’’kuks ff Fk ARRANGEMENT AT SWITCHING STATION A minimum number of three earth electrodes (excluding the one to be provided separately for the remote control cubicle earthing) are provided at each switching station, and they are interconnected by means of 50 mm x 6 mm MS flat forming a closed loop main earthing ring. This ring is connected by two separate


November 2010

30


and distinct connections made with 50 mm x 6 mm MS flat, to the non-track circuited rail in a single rail track circuited section and to the neutral point of the impedance bond in a double rail track circuited section of the nearest track, so as to limit the potential gradient developing in the vicinity of the switching station in the event of a fault. 2.9.1

flLVe vfFk FkZ a Zx x@ @ System Earthing flLVe vf ff Fk One designated terminal of the secondary of each potential transformer, current transformer and auxiliary transformer are connected to the main earthing ring by means of two separate and distinct connections made with 50 mm x 6mm MS flat as shown in figure -28 &29.

Figure- 28

Figure- 29

2.9.2 midj.k v vf fFk FkZ Zax@ x@ Equipment earthing ff Fk All masts, structures, fencing uprights and all outdoor equipment pedestals including auxiliary transformer tank is connected to the earthing ring by means of two separate and distinct Figure- 30 November 2010

Figure- 31



31

connections made with 50mm x 6mm MS flat. All fencing panels are connected to the supporting uprights by means of two separate and distinct connections made with 6 SWG G.I. wire. All the metallic door panels are connected to the supporting uprights by means of two separate and distinct connections made with 6 SWG G.I. wire as shown in figure- 30&31 The metal casing of potential and current transformers are connected to the mast/ structures by means of two separate and distinct connections made with 50mm x 6mm MS flat as shown in figure – 32&33.

Figure- 32

Figure- 33

The ground terminal of lightning arrester shall be connected directly to the earth electrodes by means of two separate and distinct connections made with 50mm x 6mm MS flat. The earth electrode shall be so placed that the earthing leads from the lightning arrester may be Fi ure- 34 34 brought to the earth electrodes by as short and straight a path as possible as shown in figure – 34. Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

32

3.0


ijEijkxr

vFkZ Z vFk

bys sDVª Ds VªksM by

dk

vuqj{k.k

MAINTENANCE SCHEDULE FOR CONVENTIONAL EARTH ELECTRODE

3.1

=S = = = = Seekfld S kfld vuqj{k.k@ QUARTERLY SCHEDULE Sr. Items

Inspection

Action to be taken

1

Earth flat connections to structures, equipment, rail and earth electrodes with nut and check nuts

Check for proper continuity and tightness

2

Bolts and nuts of the connections

Check for Rust and dirt should rust and be cleaned and apply dirt grease

3

MS links by bolted Check for joints between tightness earth electrode and 75mmx 8mm MS flat

4

Projection of the earth electrode

November 2010

If found broken or loose, it should be immediately replaced /tightened

If found broken or loose, it should be immediately replaced/ tightened

Check for It should be 175± 10 ground mm above the level and ground level proper soil



3.2

33

v)Z okf"kZ okf"kZd vuqj{k.k@HALF YEARLY SCHEDULE Carry out following work in addition to quarterly schedule: Sr.

Items

Inspection

Action to be taken

1.

2.

Measure earth resistance Measure earth resistance combined

By earth resistance meter. It should be permissible limit TSS – 0.5 Ω Switching station – 2.0 Ω AT Station – 10.0Ω 10.0Ω

3.

Sump

Individual earth electrode and record the value Combined earth resistance with earthing flats, connected to the equipment, structures and earth electrode Check up general condition including dryness.

If the surrounding area is too dry, water should be poured into the sump to keep the soil moist.


November 2010

34

3.3


okf"kZd vuqj{k.k@ YEARLY SCHEDULE Carry out following work in addition to quarterly and half yearly schedule:

3.4

Sr.

Item

Inspection

Action to be taken

1.

Earth pits

Check up the electrode for proper earth continuity.

Remove the hardened top layer of the earth pit for a depth of 1 meter, mix with coke and loamy soil (nonsandy) and ram the earth. Repair the earth. Repair sides and top cover of the earth pits. Avoid use of salt as far as possible to avoid rusting of earth pipe.

vFkZ byS SDVª DS VªksM ds Áfrjks Áfrjks/k/k dk ekiu@ by MEASUREMENT OF EARTH ELECTRODE RESISTANCE Fall of potential method

In this method two auxiliary earth electrodes, besides the test electrode, are placed at suitable distances from the test electrode as shown in figure–35. A measured current is passed between the electrode ‘A’ to be tested and an auxiliary current electrode ‘C’ and the potential difference between the electrode ‘A’ and the auxiliary potential electrode ‘B’ is measured. The resistance of the test electrode ‘A’ is then given by: R

= V/I = Resistance of the test electrode in

Where, R ohms, V = Reading of the voltmeter in volts, November 2010



35

I = Reading of the ammeter in amperes In most cases, there will be stray currents flowing in the soil and unless some steps are taken to eliminate their effect, they may produce serious errors in the measured value. If the testing current is of the same frequency as the stray current, this elimination becomes very difficult. It is better to use an earth tester incorporating a hand driven generator. These earth testers usually generate direct current, and have rotary current reverser and synchronous rectifier mounted on the generator shaft so that alternating current is applied to the test circuit and the resulting potentials are are rectified for measurement by a direct reading moving coil ohm meter. The presence of stray currents in the soil is indicated by a wandering of the instrument pointer, but an increase or decrease of generator handle speed will cause this to disappear. At the time of test, where possible, the test electrode shall be separated from the earthing system. The auxiliary electrode consists of 12.5 mm diameter mild steel rod driven up to one meter into in to the ground.

A

AMMETER

CURRENT SOURCE

V

VOLTMETER

X = 1m

A

TEST ELECTRODE

B

POTENTIAL ELECTRODE

C

CURRENT ELECTRODE

Figure 35 Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

36

3.5


gLr pkfyr vFkZ Vs LVj dk fooj.k@ fooj.k @DETAILS OF EARTH TESTER (Hand Driven) Earth resistance meter are employed for measurements of earth resistance in Traction sub station, switching stations and other electrical installations. An Earth resistance meter comprises a hand driven magneto type D.C. Generator, a current reverser, rotary rectifier and ohm meter. The current reverser and rotary rectifier are driven along with D.C. Generator by driving systems which incorporate a clutch mechanism for unidirectional rotation and a governor for speed control. The function of current reverser is to change the direction of flow of current in the soil and that of rotary rectifier is to maintain unidirectional current in the potential coils of the ohm meter. The ohm meter consists of a current coil and a potential coil mounted on a common spindle and placed in the magnetic field of a permanent magnet. The current coil is connected in series with the earth electrodes and current electrodes. The potential coil is connected across the earth electrode and the potential electrode through the rotary rectifier. While measuring the earth resistance the terminals C1, P1 are connected to the main earth electrode P2 to the potential electrode and C2 to the current electrode. The potential and current electrodes are temporary electrodes placed in the ground 50 to 75 feet apart and 50 to 75 feet & from the earth electrode as shown in below figure- 35 A When the megger is operated an ac current is produced in the coil. The voltage drop produced in the earth electrode is applied across the potential coil. The

November 2010



37

current coil produces a torque in the clock wise direction, and the potential coil produces a torque in anti-clock wise direction. The current applied to the current coil is inversely proportional to the earth resistance and the voltage drop applied across the potential coil is directly proportional to the earth resistance the torque opposes each other and brings the moving system to rest when they are equal. The pointer indicates the earth resistance values on a calibrated scale.

Cu rrent Term inal: or C2 Poten tial tial Terminal: P1 or P2

C1

C2

P1

P2

50 - 70 feet

Test Earth Electrode

50 - 70 feet

Potential Electrode

Current Electrode

Figure – 35 A Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

38

4.0


vuqj{k.k eqDr vfFkZaxx@ @MAINTENANCE FREE EARTHING In conventional earthing system GI pipe is used as earth electrode. It is provided with charcoal and salt as conducting media, which provides a reasonable earth. Corrosion of metallic parts is comparatively fast. It also requires maintenance by way of watering of earth pits and chiseling of corrosion prone parts and their replacement. Required monitoring may not always be feasible in certain crowded and inaccessible areas. With technological developments in this field, modern maintenance free and durable earthing system employs steel conductors as electrode which are copper claded and utilize graphitic compounds and non corrosive salts as “ Ground Enhancing Material” which do not lead to corrosion. Such earth pits also do not require the usual watering schedules to maintain the earth resistance with in limits. Maintenance free earths are to be constructed as per RDSO’s specification no.RDSO/ PE/ SPEC/ 0109-2008 (REV‘0’). Where the earth pits are not easily accessible for schedule maintenance, maintenance free earth pits shall be provided. In areas where clusters of earth pits are required to keep the earth resistance low, provision of maintenance free earth pits should be made during initial installation.

4.1

k@ @EARTH RESISTANCE vFkZ Áfrjks//k k The earth resistance value at earth bus bar should be less than 0.5 ohms for major electrical equipment & installation.

November 2010



39

4.2 mi;ksx@ x@APPLICATIONS This earthing system may be used in following locations. Sub stations & switching stations Remote Terminal Units Transformer & Generator neutral earths Lightning arrester earths Equipment earths including panels     

4.3

vuqj{k.k eqDr vfFkZax Á.kkyh@MAINTENANCE FREE EARTHING SYSTEM This earthing system includes earth electrode installation in suitable pit, construction of earth pit with cover for the installation, connection of earth electrode with equi-potential earth bus and connection of equipment to equi- potential earth bus.

4.3.1

vFkZ bySDVªksM@ M@Earth Electrode The material for earth electrode used in this type of earthing, has a good electrical conductivity and it does not corrode in a wide range of soil conditions. There are basic two types of earth electrodes used in this earthing system. i.

jkWM Vkbi vFkZ M@Rod type earth vFkZ bySDVªksM@ electrode

The copper bonded stainless steel rod (low carbon high tensile steel alloy) earth electrode shall conform to the standard BS 4360 Grade 43A or EN10025:2-004 S275IR molecularly bonded by 99.99% pure high Handbook on Earthing Earthing System for for Power Supply Installation Installation

November 2010

40


conductivity copper on outer surface with copper coating thickness 250 micron or more. The earth rod shall have following characteristics/ specifications. a. The minimum length of earth electrode shall be 3.0 meters long. The length of electrode may be increased in multiple of 1.0 meter met er to reduce earth resistance. b. To increase the length, pieces of similar rod shall be either exothermally welded to basic 3.0 meter electrode or connected using socket of suitable size. These sockets shall be molecularly bonded by 99.99% pure high conductivity copper on inner & outer surface with copper coating thickness 250 micron or more. c. The diameter of earth electrode shall not be less than 17 mm. d. The copper bonding thickness on stainless steel rod shall be 250 microns or more, hot dipped or electroplated. e. Copper bus bar of size 250 mm x 50 mm x 6 mm having electrical conductivity of 101% IACS minimum 99.9% copper content shall be exothermically welded to rod with 4 holes of 12 mm dia. (2 on each side) for connecting earthing conductor. f. Current carrying capacity of earth electrode should be such as to have more than 15kA for one second.

November 2010



41

la l fs Unzr ikbi vFkZ bySDVªksM@ M@Concentric l l l ads d a fUnz

ii.

pipe earth electrode 



MS pipe with 25 - 50 mm diameter, class B, ISI mark as per IS: 1239, length 2000 mm or 3000 mm is used as primary conductor as shown in table -1 MS pipe with 40 - 100 mm diameter, class B, ISI mark as per IS: 1239, length 2000 mm or 3000 mm is used as secondary conductor (electrode) as shown in table -1 Table - 1

Sr.

Current capacity

1 2 3 4 5

3kA 5kA 15kA 40kA 50kA

Primary conductor diameter

Secondary conductor (Electrode) dimensions (dia x length)

25 mm 25 mm 25 mm 40 mm 50 mm

40 mm x 2000 mm 40 mm x 3000 mm 50 mm x 3000 mm 60 mm x 3000 mm 100 mm x 3000 mm

NOTE – For more than 50kA applications, multiple electrodes of 50kA capacity are installed and connected. 

For hermetically filling inside the cavity between secondary conductor and primary conductor, crystalline compound is to be injected in the electrode assembly. It is a combination of high conductivity metal alloys, copper & aluminium powder, conductive carbon/cement and bonding material etc. mixed in different proportion. The mixture is forced (pressurized) filled inside the earth electrode in the paste form and after solidification of the same, the end caps are welded.


November 2010

42








The metal alloys shall help in conducting the current and conductive carbon gives anti corrosive property. Bonding material provides strength to the mixture. Resistivity of the mixture shall be less than 0.2 ohm - meter. Resistivity shall be tested by making a 20 cm cube of the material and checking resistance across the opposite face of the cube. Complete electrodes shall be molecularly bonded by 99.99% pure, high conductivity copper on outer surface with copper coating thickness 300 micron or more. Its surface shall be cleaned and free from any visible oxide layer or foreign material. Copper bus bar of size 250 mm x 50 mm x 6 mm having electrical conductivity 101% , minimum 99.9% copper content shall be preferable to exothermically welded to earth electrode or connected with the help of two number stainless steel nut bolts of appropriate size having 4 holes of 12 mm dia ( 2 on each side) for connecting earthing conductor as shown in figure - 36 25 x 3mm Copper Strip (To be duplicated)

300 x 25 x 6mm Copper bus

Ground Level

To Equipment Exothermic Welding

Exothermic Welding Exothermic Welding

Earth Electrode (Dimension as per design)

Earth Ehancement 5 ft x 5ft x 10ft pit or 300mm bore

Figure - 36 November 2010

(Earth Electrode Installation)



4.3.2

43

vFkZ bugsUles Ules aV lkexzh @Earth Enhancement Material

Figure 36A Earth enhancement material is a superior conductive material that improves earthing effectiveness especially in area of poor conductivity as shown in figure 36A. It improves conductivity of the earth electrode and ground contact area. It has following characteristics: a.

It should low resistivity bellow 0.2 ohm- meters.

b.

It shall not depend on the continuous presence of water to maintain its conductivity.

c.

It should be a little alkaline in nature with pH value >7 but <9.

d.

It should have better hygroscopic properties to absorb moisture. It should absorb and release the moisture in dry weather condition and help in maintaining the moisture around the earth electrode.


November 2010

44


e.

It has a capacity to retain >10% moisture at 0 105 C.

f.

It should have water solubility <5%.

g.

It should not decompose or leach out with time.

h.

It shall be thermally stable between -10 C to + 0 60 C ambient temperature.

i.

It should be non toxic, non reactive, non explosive and non corrosive.

j.

It shall not pollute the soil or local water table and shall meet environmental friendly requirement for landfill.

k.

It should expand & swell considerably and shall remove entrapped air to create strong connection between earth electrode and soil.

l.

It should be diffused into soil pores and shall create conductive roots enlarging conductive zone of earth pit.

m.

It shall be permanent & maintenance free and in its “set form”, shall maintain constant earth resistance with time.

n.

It shall not replacement.

o.

It shall not cause burns, irritation to eye, skin etc.

p.

Minimum quantity of material to be required:

0





November 2010

require

periodic

earth

charging

or

enhancement

For 5ft x 5ft x 10ft earth pit – min 75 kgs per pit. For 300 mm bore type earth pit – min 50 kgs per pit Handbook Handbook on Earthing System System for Power Supply Supply Installation Installation


45

cSdfQy lkexzh@Backfill material

4.3.3

The excavated soil can be used if it is free from sand, gravel and stones. Small proportion of sand in the soil may be permissible. Material like sand, salt, coke breeze, cinders and ash are not used because of its acidic and corrosive nature. While backfilling the soil shall be thoroughly compacted with at least 5 kg compactor, in case the soil is dry small quantity of water may be sprinkled only to make it moist enough suitable for compacting. Large quantity of water may make the soil muddy which is not suitable for compacting and after drying the soil may contain voids which may permanently increase earth resistance. 4.3.4

le foHko foHk c l ,oa vFkZ vFkZ pkyd@Equi- Potential Bus foH koo cl & Earth Conductor 



A copper bus bar of size 300 mm x 25 mm x 6 mm to be installed in this equipment room as equi potential bus connected with copper strip of size 25 mm x 3 mm (suitable length) from instrument to the bus bar. The connecting terminal of the earth electrodes to the bus bar must be connected by copper strip of 25 mm x 3 mm (suitable length) buried inside a trench of 300 mm width x 600 mm (depth from the nearest wall). It is duplicate earth conductor. The maximum specific resistance of the copper -7 strip earthing conductor shall be 17.241 x 10 0 ohm cm at 20 C and having electrical conductivity of 101% IACS i.e. minimum 99.9% copper content.


November 2010

46








4.3.5

0

At a temperature of 20 C, its density shall be 8.89 3 gm/cm . A single length of copper strip shall be used for each duplicate earthing conductor and no joint shall be permitted. The joint shall be made by exothermic welding of at least 10 mm overlapping portion of the strips. It shall be connected to earth electrode and earth bus bar with the help of exothermic welding or at least two number stainless steel nut bolts of appropriate size.

vFkZ bdkbZ dk fuekZ.k@Construction of unit Earth 







Make 5ft x 5ft x 10ft earth pit. If it not possible to make such a pit due to non availability of clear space a minimum 300 mm bore up to 10ft deep can be made using earth auger or any other method. Each pit larger than specified size can be made, if required. Sleeve the soil digged and remove the gravels and stones. If soil quality is good then add some quantity of earth enhancement material in the soil for using as backfill. If the soil seems unusable (containing large quantity of gravel, stones, murum, sand etc) then replace the soil with black cotton soil. Insert the electrode at the center of the earth pit and arrange to keep it vertical in the pit’

November 2010













4.3.6

47

Arrange for adequate quantity of water supply for the earth pit (600 liters). Fill the pit with the backfill and keep on adding the earth enhancement material surrounding the electrode and simultaneously watering the pit with a steel bar or pipe, keep on poking the soil gel and stirring intermittently for removing the air pockets and proper settlement of the pit. The procedure to be repeated till completion of the filling of the earth pit along with the packing material and sufficient watering adequate ramming. The pit should be very compactly rammed and watering for 2-3 days and addition of soil if required be done. Construct inspection chamber with cover for the installation. Measure the earth resistance as per IS 3043:1987 code of practice.

cgq vFkZ fiVks a }kjk }kjk vFkZ fjax dk fuekZ.k@ Construction of Ring Earth by providing multiple earth pits 

Wherever it is not possible to achieve required earth resistance with one earth electrode/ pit due to difficult/ rocky soil conditions, provision of ring earth consisting of more than one earth pit is required. The number of pits required can be decided based on the resistance achieved for the earth pits already installed.


November 2010

48








4.3.7

The distance between two successive earth electrodes shall be min. 3.0 mtrs/length of electrode which ever is higher, and max. up to twice the length of the earth electrode. These earth pits shall inter linked using 25 x 3 mm copper strip to from a loop preferably using exothermic welding or with the help of at least two numbers of stainless steel nut bolts of appropriate size. The interconnecting strips shall be buried not less than 800 mm (0.8 m) below the ground level. This interconnecting strip shall also be covered with earth enhancing compound.

fujh{k.k d{k@Inspection chamber 







A 300 mm x 300 mm x 300 mm (inside dimension) concrete box (wall thickness min. 50 mm) with smooth cement plaster finish shall be provided on the top of pit. A concrete lid of 25 to 50 mm thick, with pulling hooks, painted black shall be provided to cover the earth pit. PVC sleeve of appropriate size shall be provided in concrete wall to take out earthing connections. The masonry work shall be white washed inside and outside. Care shall be taken regarding level of the floor surrounding the earth so that the connector is not too deep in the masonry or projecting out of it. On backside of the cover, date of test and average resistance value shall also be written with yellow paint on black background with date.

November 2010



5.0

49

ckWfUMax] x] xzkmfUMax@ x@ vfFkZ Zx a ds fy, fy, ,DlksFkfeZ FkfeZd vfFk oSfYMa fYMax la;ks ;kstu@ t tu u@ u @EXOTHERMIC WELDING CONNECTION FOR BONDING, GROUNDING/ EARTHING The Exothermic welding connection process for grounding/ earthing covers the requirements and acceptance principle for weld material, welding tool and tool kit, bonds/ track bond wires for making permanent electrical bond connection between two conductors as per RDSO specification no. TI/ SPC/ OHE/ EXOTHRM BOND/ 0100 (04/10). These weld materials including tool kit shall be useful in following railway application on 25kV electric traction system. (a) Traction bond connection to rail & OHE structures enroute. (b) Traction rail continuity connection. (c) Earthing connections like at TSS, SP/ SSPs, SCADA/ RTU and other important electrical installation. (d) Bus bar connections etc. (e) Copper to copper, copper to steel connection. (f) Important bonds which are not disturbed during track relaying. (g) Sections where 90UTS rails have been provided. (h) Theft prone areas.


November 2010

50

5.1


lkekU; vko’;drk;s a@GENERAL REQUIREMENTS 

















Welding material along with tool kit shall be capable of providing a permanent bonding connection involving copper or aluminium or steel. The final bond shall be achieved in such a way that homogeneous molecular bonding of two involved metals takes place perfectly. Exothermic welding process should be a steady burn, no pops and no drastic color changes (white hot color during burn, turns orange as the reaction stops and the molten metal grows orange). Welding connection shall be without voids or pinhole, and no porosity should be detected. The process shall be consistent and continuous. It shall be permanent, solid metal, maintenance free connection and shall not be affected by high current surge. It shall not loosen or corrode at the point of weld. There shall be no additional contact surface or mechanical pressures involved. It shall be vibration proof and corrosion free electrical connection. It shall not brittle with age and shall be able to sustain physical impacts, which may be experienced under the field conditions. Electrical resistance and other properties shall not deteriorate with ageing and under severe Indian climatic conditions. It shall have a current carrying capacity equal to or greater than that of the conductors

November 2010





5.2

51

Life of the joints shall not be less than 10 years irrespective of life of conductors, equi-potential earth bus bars or ground rods used.

os o fYa fs Y aMx M o o o sfY a x lkexzh@WELDING MATERIAL 

The weld material shall be designed for two specific types of jointing applications Rail welding application Earthing & bonding application.  









It shall not contain phosphorous or any caustic, toxic or explosive substance. For rail welding application, the welding material shall not contain tin besides the above cited elements. Its components shall not volatile or sensitive to shock, nor capable of spontaneous ignition by friction. The reaction of the welding material shall be completed within 10 seconds and on completion of jointing & bonding process. The resulting weld nugget shall free of dissolved gases or low boiling point elements, e.g., small voids or blisters on the surface. Weld materials shall provide a final bond with minimum tensile strengths of 40,000 psi tested using ASTM ES-94a (Test Methods for Tension Testing of Metallic Material). The weld material for traction bond and stud welding for rail application shall be free from tin. As presence of metallic tin allows for wetting of rail surface and provides for unnecessary penetration that can lead to metallurgical damage to the rail.


November 2010

52




5.3

The weld material for earthing & bonding application shall be tested as provision of IEEE-837 by NABL/ILAC Member labs.

osfYa fYaM Mx x VwYl Y l dh fof’k"Vrk;s rk;s a@SPECIFICATION x fof’k"V OF WELDING TOOLS 













It shall be suitable for bonding as per the sizes specified for bonding equi-potential earth bus bars (EEBB) to ground rod, protective conductor etc. The tools shall be lightweight and whole kit containing bonding material, weld materials. The tools shall be easily portable by one person from one spot to another. It shall be possible to remove it immediately after jointing or whenever whenever required. In-built protection shall be available against any flash generation during weld process, which is injurious to staff. Tools required for high temperature working shall be of graphite or suitable material so as to be capable of working at temperatures sufficiently higher than the temperature conditions achieved during jointing. Any ignition tool included in the tool kit shall be portable and easy to operate. Ignition time shall be very quick and shall work efficiently even under damped weather conditions. For integrity and safety of the connection, the weld metal, moulds and clamps should be of the same manufacturer.

November 2010



















53

Tool kit shall give consistent quality bond for at least 100 joints for non-tensioned joints. Power operated tools, if any, for carrying out weld work shall have the provisions for its working on 110/ 230V a.c. and portable battery. Suitable means and guidance shall be provided to prevent equipment failures connected through rails due to flow of electric current during weld process. Complete jointing process including preparatory work shall not take more than 2 to 3 minutes per bond under normal working conditions, to avoid requirement of traffic line blocks. If any melting of metal is involved in the jointing process, it shall quickly solidify so that system is immediately available for charging. Once ignition is started it shall not result in imperfect bond/joint. Weld material shall not contain hazardous ingredients sufficient to constitute a hazard & weld process shall not result in any surface irregularities. Welding materials shall have a minimum shelf life of five years, when stored in a reasonable storage condition, so that material can be used without any testing within this period for optimum results.


November 2010

54

5.4


osfYa fYaMx M Mx x x vkSt kj@ +

WELDING TOOLS

Welding tools shall be suitable for bonding as per the size specified in drawing for bonding equipotential earth bus bar(EEBB) to ground rod, protective conductor etc. 78

Tool for Splice Connection

0 6 1

3 2

8 2

40

78

Tool for Splice Connection 100

28

40

23

0 8 1

Tool for Tee Connection 3 2

November 2010

8 2


8 7


55

100

Tool for Tee Connection

0 8 1

3 2

8 2

50

100 23

Tool for Tee Connection

50

3 8 2 2

0 0 1

28

103

Tool for Horizontal to horizontal grd rod cross connection

0 0 2

3 2

8 2

50


November 2010

56


103


5 5 1

5 4

103

2 3

0 5


3 0 1 28 23

8 2

Note: These drawing (Para (Para 5.4) may may differ as per site condition and requirement.

November 2010



57

6.0 D;k djs a vkS vkSj D;k u djs a@ DO’S & DON’TS 6.1

D;k djs a@

DO’S:

1.

Use IS (3040) approved MS flat and earthing wire for earthing purpose.

2.

Ensure that the electrodes are embedded below permanent moisture level.

3.

All joints between the MS flat, MS rod or between MS flat and MS rod should be welded.

4.

Ensure that all welded joints are treated with red oxide and afterwards coated with bituminous compound.

5.

Ensure good and reliable electrical connection between earthing leads and earth electrodes.

6.

Consider all parameters while designing earth system.

7.

Ensure that all materials, fittings etc. used in earthing system shall confirm to IS specifications wherever they exist.

8.

Ensure safety while working on electrical installations.

9.

Ensure that as far as possible all earth terminals shall be visible.


November 2010

58

6.2


D;k u djs a@

DON’T

1.

Don’t make series connections for earth path.

2.

Don’t embed the earth electrode in concrete.

3.

Don’t solder any joint between MS flat.

4.

Don’t touch or tamper with any electrical gear or conductor unless you have made sure that it is dead and earthed. High Voltage apparatus may give shock or flashover without touching.

5.

Don’t disconnect earthing connections or render ineffective the safety gadgets installed on mains and apparatus till you are at work.

6.

Don’t expose your eyes to an electric arc. Painful injury may result even with short exposure.

7.

Don’t use paint, enamel and grease on the electrodes.

8.

Don’t use neutral conductor as earth wire.

9.

Don’t use water pipe line for earthing.

November 2010



59

ifjf’k"V&1@

Annexure - 1

,SDDlks lks FkfeZ FkfeZd ososfYa fYaMx Mx çfØ;k ds Nk;kfp=@ D Nk;kfp=@

Photographs of

Exothermic Welding Procedure

Preparation of surface on the rail and MS

Selection of zig as per rail size

Adjustment of zig

Final fitment of zig on the rail


November 2010

60


Placement of retaining plate inside the zig

Filling of exothermic material in the zig

Firing of exothermic material by the lighter gun

Exothermic welding in progress November 2010



61

Removing of waste material after welding

View of welded joint


November 2010

62


ifjf’k"V&2@Annexure - 2 jsy es a fNnz dh çfØ;k ds Nk;kfp=@ Nk;kfp=@ Photographs fNnz djus dh of Process of Hole Drilling in Rail

Fixing of zig on the rail

Drilling process in progress

Providing coolant during drilling

Hole view after drilling

Hollow core drill

November 2010



63

ifjf’k"V&3@Annexure - 3 jsy es a fMª fMªfya ya x djus dh dh e’khu dh fof’k"Vrk;s a@ ff Specification of Rail Drilling Machine Rail Drilling Machine (2- stroke engine)

Weight:

-

13 kg

Ext. dimension dimensions: s: (L x W x H):

-

330 x 480 x 270

Power output:

-

1.4 kW

Speed:

-

267 rpm or 212 rpm

Hole diameter:

-

8 – 36 mm

Drive:

-

2 stroke engine

Tool holding fixture:

-

Weldon shaft 19 mm

Max. rail thickness :

-

50 mm

Cooling system:

-

Internal cooling system for hollow Core with automatic coolant valve opening.

Kit includes Pack and charger:

- Drilling machine, coolant tank with pump, metal case, tool kit, battery.


November 2010

64


Rail Fastening Devices

Description Rail fastening device for normal rails.

Rail fastening device for grooved rails.

Weight

3 kg 4 kg

Rail fastening device for clamping rail drilling machine to the flange of the rails.

4 kg

High Performance Hollow Core Drills S. No. 1 2 3 4 5 6 7 8 9 10 11 12 November 2010

Required diameter of drill in mm 16 16 17 17 18 18 19 19 20 20 22 22



Material

: Powder metal HSS-XE steel

Coating

: TIALN Multilayer coating

Diameter range

: 16 – 22 mm

Drill length

: 70 mm to 90 mm

Drill performance

65

: Approx. 100 times drilling

Features Rail Drilling Technology has the following features:

•

Light, easy to handle and compact drilling machines with a choice of drive motors

•

Two-stroke petrol engine with a spindle speed of 267 rpm for the drill range up to 24 mm

•

A slow drill with a spindle speed of 212 rpm for drills from 24 to 34 mm.

•

Direct current disc drive engine of 48 V DC, 1.4 kW, battery powered with a spindle speed of 390 rpm.

•

Alternating current motor of 230 V/AC, 1.5 kW with a spindle speed of 220 or 280 rpm.

•

Compact storage of the drilling tools in transportable metal cases.

•

Short drilling times because of spindle speeds adapted to each diameter.

•

Simple and fast installation of the machine on the rails with quick loosening devices.


November 2010

66


•

Drilling unit can remain fixed to the rails by means of rail foot clamping unit while rail traffic is being maintained.

•

Easily changeable rail profile template for all track profiles.

•

Special templates for special uses. E.g. hinged profiles for grooved rails.

•

Drilling holes at exact intervals with drilling gauges and special templates for axle counters, fishplates and insulated rail joints.

•

Drilling program for all applications in the rail sector with the internationally accepted standard tool

November 2010



67

lannHkZ HkZ 1- Hkkjrh; ekud “vfFkZax ds fy, fy, dksM vkWQ çsfDVl fDVl ” vkbZ,l 3043&1937 A 2- ,lh lcLVs’ku ’ku xzkmfUMax es a lqj{kk ds fy, fy,

IEEE 80

xkbMA

3- lcLVs’ku ’ku xzkmfUMax es a LFkkbZ dusD’kuks D’kuks a vgZdkjh ekud IEEE 837 A 4- Hkkjrh; fo|q fo|qr fu;ekoyh 1956 uohure la’kks ’kks/kuks /kuks a lfgrA lfgrA 5- ,lh d"kZ.k vuqj{k.k ,oa çpkyu çpkyu eSuqvy okWY;w e II ¼ikVZ II½ 1994A 6- vuqj{k.k eqDr vfFkZax ij vkjMh,lvks Lis lhfQds’ku laRDSO/PE/SPEC/PS/ 0109 – 2008 (Rev. 0) A 7- ,DlksFkfeZ FkfeZd oSfYMax ij vkjMh,lvks Lis lhfQds’ku ’ku laTI/SPEC/OHE/EXOTHRM Bond/ 0100(04/10) A 8- bjdSeVsd Xokfy;j es a fnukad 12 uoEcj 2010 dks vk;ksftr ftr lsehukj ehukj es a fofHkUu jsyks y aks ls vk;s gq;s izfrfuf/k;ks a }kjk fn;k x;s lq lq>ko A


November 2010

68


REFERENCES

1. Indian standard code of practice for earthing IS: 30431937 2. IEEE guide for safety in ac sub station grounding IEEE 80 3. Standard for qualifying permanent connections used in substation grounding IEEE 837. 4. Indian Electricity Rules 1956 with latest amendments. 5. Manual of AC Traction maintenance and operation volume II (PART II) 1994. 6. Maintenance free earthing RDSO specification no. RDSO/PE/SPEC/PS/0109-2008( RDSO/PE/SPEC/PS/01092008( REV ‘0’) 7. Exothermic welding RDSO specification no. TI/ SPC/ OHE/ EXOTHRM BOND/ 0100 (04/10). 8. Suggestions given by participants from various Railways th during seminar conducted on 12 November 2010 at IRCAMTECH/ Gwalior.

******

November 2010



69

gekjk mn~ mn ~ns’; mnns vuqj{k.k izkS|ksfxdh fxdh vkSj dk;Ziz.kkyh dk mUu;u djuk rFkk mRikndrk vkSj jsyos yos dh dh ifjlEifRr ,oa tu’kfDr tu’kfDr ds fu"iknu fu"iknu es a lq lq/kkj djuk ftlls vUrfoZ"k;ks a es es a fo’oluh;rk] miyC/krk] mi;ksfxrk fxrk vkSj n{krk izkIr dh tk ldsA ;fn vki bl lanHkZ nHkZ es a dks dksbZbZ fopkj vkSj fo’ks"k"k lq>ko nsuk uk pkgrs gks a rks rks d` d`Ik;k ges a bl bl irs ij ij fy[ks aA lEidZ lw =

%

Ik=kpkj dk irk

%

funs’kd ( fo|qr ) Hkkjrh; jsy mPp vuqj{k.k izkS|ksfxdh fxdh dsUnz] egkjktiq j] Xokfy;j e- izfiudksM 474 005

Qksu

%

0751&2470803 0751&2470740

QSDl

%

0751&2470841

bZ&esy

:

[email protected] direlca [email protected] om


November 2010

70


OUR OBJECTIVE To upgrade maintenance technologies and methodologies and achieve improvement in productivity and performance of all Railway Railwa y assets and manpower which inter-alia would cover reliability, availability, utilisation and efficiency.

If you have any suggestions and specific comments please write to us.

Contact person

Director Electrical

Postal address

Indian Railways Centre for Advanced Maintenance Technology, Maharajpur, Gwalior, Pin Code - 474 005

Phone

0751 – 2470740 0751 – 2470803

Fax

0751 – 2470841

E-mail

[email protected]

November 2010


Handbook on Earthing system for power supply installations.pdf

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