Explained about all activities and methods.

1. OHE BASICS
OHE means Over Head Electrification. It consist of,
1. Catenary wire (copper cadmium 19 strands 65 sq.mm)
2. Contact wire (Hard drawn copper solid round 107 sq.mm)
3. Dropper wire is bet catenary and contact wire.( 5 mm hard drawn copper ) and supported by OHE
cantilevers.
Feeding post-
Means a supply control post, where the incoming feeder lines from grid sub-station are terminated.
Neutral section-
Means a short section of insulated and dead overhead equipment which separates the areas fed by
adjacent sub-stations or feeding posts.

2. OHE BASICS
Power Block-
Means blocking of a section of line to electric traffic only.
Supply control post-
Means an assembly of interrupters, isolator switches, remote control equipment and other
apparatus provided for controlling power supply to overhead equipment. It includes feeding
posts, sectioning and paralleling posts and sub-sectioning posts.
Tower wagon-
Means a self-propelled vehicle which is used for the maintenance and repairs of overhead
equipment.

3. OHE BASICS
Bond
An electrical connection across a joint in or between adjacent lengths of rail.
i) Bond, continuity : A rail bond used for maintaining continuity of the rail circuit at crossings and junctions.
ii) Bond, Cross – A rail bond used for connecting together two rails of a track or rails of adjacent tracks.
iii) Bond, Impedance : A special rail bond used to bridge an insulated rail joint in actrack circuited sections in
areas equipped for electric traction.
iv) Bond Rail – An electrical connection across a joint between two adjacent lengths of rail as part of the
track return.
v) Bond, Structure – An electrical connection between the steel work of track structures, bridge or station
building, to which the traction overhead equipment is attached.

4. OHE BASICS
Cantilever (Assembly)
It is an insulated swivelling type structural member, comprising of different sizes of steel tubes, to support and to keep the
overhead Catenary system in position so as to facilitate current collection by the pantograph at all speed without
infringing the structural members. It consists of the following structural members.
i) Stay arm – It comprises of dia. 28.4/33.7 mm (Small) size tube and an adjuster at the end to keep the bracket tube in
position. It is insulated form mast by stay arm insulator.
ii) Bracket tube – It comprises of dia 40/49 mm (large) or dia 30/38 mm (standard) bracket tube and insulated by bracket
insulator. Catenary is supported from this member by Catenary suspension bracket and Catenary suspension clamp.

5. OHE BASICS
Crossings
The electrically live member / conductor passing over another electrically live member /
conductor, without physical contact.
i) Power line crossing – An electrical overhead transmission or distribution line or underground
cable placed across railway tracks whether electrified or not for transmission of electrical energy.
ii) Crossing OHE – Crossing of two conductors of OHE crossing without physical contact.

6. OHE BASICS
Electrical Clearance- The distance in air between live equipment and the nearest earthed part.
Encumbrance-The axial distance on vertical plane between the Catenary and the contact wire at
support.
Feeder-A conductor connecting (a) a substation with a feeding post, or (b) a feeding post with the
OHE.
Height of contact wire-The distance from rail level to the under side of contact wire.

7. OHE BASICS
Interrupter
It is a single phase Vacuum breaker used as load switch to close the circuit on Fault, but does not
open on fault. It is operated either by remote control or manually at site.
Different methods of connection of interrupters are:
a)Bridging Interrupter: An interrupter which is provided at the neutral section to extend
the feed from one substation to the overhead equipment normally fed by the other
substation in emergencies or when the latter is out of use. This normally remains in
the open position.

8. OHE BASICS
b)Sectioning Interrupter: An interrupter which connects adjacent sub-sectors together to maintain
continuity of supply. This normally remains in closed position.
c)Paralleling Interrupter : An interrupter which connects overhead equipment’s of two different
tracks. This normally remains in closed position to reduce the voltage drop.
Mast
A single vertical post embedded in the foundation or otherwise rigidly fixed in vertical
position to support the overhead equipment with cantilever assembly. It may be rolled
section or fabricated. The uprights of portals and TTCs are also called masts.
Note : Pre-stressed concrete spun poles for traction overhead equipment are under
development.

9. OHE BASICS
Jumper - A conductor or an arrangement of conductors for electrical continuity not under
tension, which forms electrical connection between two conductors or equipment’s.
Return conductor - A conductor which carries return current from the tracks to the sub-station in
the booster transformer system.
Regulating Equipment - A device for maintaining the tension of OHE conductors constant under
all ambient temperature conditions.
Note : Such OHE is called regulated OHE.

10. OHE BASICS
Suspension Distance - The horizontal distance from the centre of the eye of Catenary suspension
bracket to the face of the mast for a single cantilever assembly or the face of cross arm channel in
case of multiple cantilever assembly.
Span -The distance between the centre line of the adjacent supporting masts for overhead
equipment/ lines. Clear span in case of portal structure, is the distance between the inner faces
of portal uprights.
Stagger - Stagger of the contact wire is the horizontal distance of the contact wire from the
vertical plane through the centre of track.
Section Insulator - A device installed in the contact wire for insulating two elementary electrical
sections from each other while providing a continuous path for the pantograph without break of
current.

11. OHE BASICS
Supply Control Post - It is general term which refers to an outdoor assembly of control gear, such
as interrupters, isolators, potential transformers, auxiliary transformers, etc including remote
control equipment installed in a cubicle, for controlling power supply to overhead equipment.
a) Feeding Post (FP) – It is a supply post where the incoming 25 kV feeder lines from substation
are terminated and connected to the overhead equipment through interrupters.
b) Sectioning and Paralleling Post (SP) - It is the supply control post situated mid-way between
two feeding posts at the neutral section and provided with bridging and paralleling interrupters.
c) Sub-sectioning and Paralleling Post (SSP) – It is a supply control post where sectioning and
paralleling interrupters are provided.
d) Sub-sectioning Post (SSP) – (for single line section) : It is a supply control post where a
sectioning interrupter is provided.

12. OHE BASICS
Sector - A section of Overhead equipment of a track which can be energized by closing a feeder
circuit breaker at the substation.
a) Sub-sector – The smallest section of overhead equipment which can be isolated remotely by
opening of interrupters.
b) Elementary Section – The smallest section of overhead equipment which can be isolated from
the rest of the system by manual operations.
Tension Length - Length of conductor which is stretched between the two anchor points
Versine - The versine is the maximum offset of the rail on which spans have been measured of
the curved track form the chord connecting two points, each opposite adjacent masts.

13. OHE BASICS
Electrical Clearance
Clearance - The clearance between 25 kV live parts and earthed parts of fixed structures or moving
loads shall be as large as possible. The electrical clearances to be maintained under the worst
conditions of temperature, wind, etc are given below:
a) Maximum vertical distance between any live part of overhead equipment or pantographs and parts
of any fixed structures (earthed or otherwise) or moving loads:
i) Long duration 320 mm
ii) Short duration 270 mm
b) Minimum lateral distance between any live part of overhead equipment or pantographs and parts
of any fixed structures (earthed or otherwise) or moving loads:
i) Long duration 320 mm
ii) Short duration 220 mm

14. OHE DESIGN
General Power Supply Diagram:
General Power supply Diagram shows the basic scheme of switching station and sub-section wise.
OHE DRAWINGS
Pegging Plan
OHE Layout Plan (LOP)
Cross Section Drawings(CSD)
Structural Erection Drawings (SED)
Profile/Clearance Study Drawings
As Erected Drawings
Switching Station Drawings

15. OHE FOUNDATIONS
Foundation Design Basis:
Foundations are designed on the basis of FBM code, type and bearing capacity of soil, shoulder
width and the extent of projection above ground level.
Selection of the type and size of foundation is done from the “Volume Chart and equivalent chart
for foundations”

16. OHE FOUNDATIONS
TYPES OF FOUNDATIONS
a)Side bearing foundations or “B” type foundations - are used for masts where earth is normal
and fully consolidated, the soil bearing capacity is 11.000 or 21,500 kgf/m2 and 300mm wide
shoulder is available beyond the outer edge on the foundation on banks.

17. OHE FOUNDATIONS
TYPES OF FOUNDATIONS
b)Side gravity foundations or “BG” type foundations-may be used for masts where soil bearing
capacity is 8000 and 11000 kgf/m2, or adequate shoulder width is not available i.e less than
300mm beyond the edge of foundation.

18. OHE FOUNDATIONS
TYPES OF FOUNDATIONS
c)Pure gravity foundations or “P” type foundations - are used for portals and are designed for soil
bearing capacity of 8000 and 11000 kgf/m2.

19. OHE FOUNDATIONS
TYPES OF FOUNDATIONS
d)New pure gravity foundations or “MG” type foundations may be used for masts where soil
bearing capacity is 5500, 8000 and 11000 kgf/m2 or where adequate shoulder width is not
available. In such cases, it should be ensured that foundation is not exposed.

20. OHE FOUNDATIONS
TYPES OF FOUNDATIONS
e)WBC and NBC type of foundations are used in Black cotton soil. Primarily WBC foundations are
to be adopted where swelling / shrinkage is not expected to take place at the founding level and
NBC foundations have to be provided where swelling / shrinkage is expected to occur.

21. OHE FOUNDATIONS
CLASSIFICATION OF FOUNDATIONS

22. OHE FOUNDATIONS
Preparatory Works for Foundation:
Ensuring of approved LOP & CSD for the particular section at site. Copy of Volume chart & Boom
combination chart
Marking of location number, chainage, type of mast, implantation on rail.
Collection of Coarse aggregates (metal), Fine aggregates (sand) & Cement near to the location.
Arranging required size of shutters.
Ensuring working condition of the Vibrator & availability of other T&P’s like scroll box, shovel,
spade, crow bar, pick axe, motor pan etc.

23. OHE FOUNDATIONS
IF ROCK IS ENCOUNTERED RESORTED TO “BLASTING”
First, inform the condition to Railway representative.
Carry out joint inspection with railway representative to assess the intensity of the blasting and
obtain Railway’s approval in writing.
Chalk out a blasting programme and arrange ‘line block’ accordingly.
According to intensity of blasting, request for caution order from railway.

24. OHE STRUCTURES
MAST - A single vertical post embedded in the foundation or otherwise rigidly fixed in vertical
position to support the overhead equipment with cantilever assembly. It may be of rolled
section or fabricated.
6” x 6” BFB – Broad Flanged Beam (152mm x 152mm)
8’’ x 6’’ RSJ – Rolled Steel Joist ( 203mm x 152mm)
“B” Series Mast (B 150, B 175, B 200, B250)
SWS Masts (S1, S3, S4, S5, S6, S7, S8 & S9)
AT Mast (T150)
All OHE masts are 9.50 metres in length.
The Drillings for fixing various SPS will be according to the drilling schedules.

25. OHE STRUCTURES
PORTALS - On multiple track sections, where adequate track centres are not available
and tracks cannot be slewed, Portals are used. Each portal consists of two fabricated
uprights and one fabricated boom consisting of with or without one central piece and two
end pieces.

26. OHE STRUCTURES

27. OHE STRUCTURES

28. OHE STRUCTURES
METHODOLOGY FOR MAST ERECTION BY RAIL CRANE
List of Mast to be erected for the km either in ascending/descenting order based on the
approved OHE Layout plan to be prepared.
Summary of total mast required for the KM to be mark on the schedule.
Availability of mast to be verified before loading.
Request for placing BFR to be given to the Customer in advance.
Masts to be loaded on the BFR- type wise as per the summary of schedule.
Masts should be secured on the BFR to avoid falling of structure on movement.
Clean the core hole of OHE foundation from any foreign materials at least one day in
advance.

29. OHE STRUCTURES
Erection:
Avail the line block from railways in prescribed format request.
After getting granted traffic block, start the erection as per schedule.
Provide 16 mm dia 1.5 m long sling on one third length of the mast from top and lock
with 5T capacity ‘D’ Shackle..
Crane operator to lower the Rail crane hook near the sling of the mast.
Mast lifting from BFR and placing on core hole of the foundation
Lean the structure away from the track and provide necessary packing & wedge.
Moving the formation to next location.
Note: On reaching to the erection spot one mast can be erected in 5min time
with rail crane. Labour requirement: 5

30. OHE STRUCTURES
METHODOLOGY FOR MANUAL MAST ERECTION BY DERRICK ARRANGEMENT
Preparatory Work:
List of Mast to be erected for the km/section to be prepared based on the approved OHE
Layout plan.
Availability of mast to be verified before making erection schedule.
Shifting of mast to locations by tractor trailer or dip trolley.
Mobilizing the T&P resources –Derrick, Hook chook, Manila ropes, “D” Shackles, Crow
bar, Wire slings etc.
For erection of 9.5m long mast 2 derrick pieces has to joined together (3mx 2nos), For
erection TTU & Uprights 3 derrick pieces has to be joint together (3mx3).

31. OHE STRUCTURES
METHODOLOGY FOR MANUAL MAST ERECTION BY DERRICK ARRANGEMENT
T&P Requirement:-
Extendable derrick : 1No,
1.5-2.0T capacity Hook Chook with 20 mtr long wire rope:1No,
16 mm dia,25m long polypropylene rope :5Nos,
Crow bar:5Nos,
’D’ Shackle (5Tonne capacity):2Nos.
16mm dia, 1.5m long sling:2Nos.

32. OHE STRUCTURES
METHODOLOGY FOR MANUAL MAST ERECTION BY DERRICK ARRANGEMENT
Erection:
Bring the assembled derrick near to the foundation and place parallel to the track. Lift bottom side of the
derrick and place above the foundation(adjacent to core hole).
Tie the poly propylene rope on four corners of the top plate of derrick.
Insert the hook chook wire rope on the single sleeve pulley and place the pulley hook on the derrick
where the provision has been made.
Place the mast on the foundation center portion of the mast should rest on foundation and also parallel
to the track.
Lift the derrick by pulling the poly propylene rope and place the derrick in vertical position. Tie the ropes
on four corners by driving crow bar inside the ground.
Attach the hook chook on the bottom side of the derrick with the help of sling & ‘D’ Shackle.

33. OHE STRUCTURES
METHODOLOGY FOR MANUAL MAST ERECTION BY DERRICK ARRANGEMENT
Erection
Provide the 1.5 mtr sling on middle of the mast and attach the hook chook wire rope hook on
the sling with the help of ‘D’ Shackle.
Tie one poly propylene rope on top of the mast for alligning.
Take load on the hook chook – Mast will get lift from the foundation.
Hold the bottom portion of the mast and continue the load taking through hook chook till the
mast is attaining the position of 45 to 60 degree from the top of foundation .
Push the bottom side of the mast in side the core hole.
Release the load of hook chook and ensure mast bottom is resting on foundation core hole.

34. OHE STRUCTURES
METHODOLOGY FOR MANUAL MAST ERECTION BY DERRICK ARRANGEMENT
Erection
Lean the mast toward country side and arrest the movement with wedges.
Remove the hook chook , sling from the derrick.
Lower the derrick by loosening the poly propylene rope carefully.
Shift the T&P’s to the next location through dip trolley.
Note: with 10 workers we can erect one mast in 30 min.

35. OHE INSULATORS
In OHE there are different types of insulators are being used.
Stay arm insulators:
These insulators are equipped with stay arm tube in cantilever, these insulators are having two different types.
Porcelain insulator ( 850 mm CD & 1050 mm CD)
Composite type insulator. (850 mm CD & 1050 mm CD)
Bracket insulators
This insulators is equipped with bracket tube in cantilever, these insulators are having two different types.
9 - ton insulators (Cut-in-insulators)
In an insulated overlap the two OHEs are made electrically separated by provision of cut-in-insulators in the
catenary and contact wire.
In section insulator arrangement this insulator is erected in the catenary wire.
In termination of wires where the platform involves, this insulators is used in the edge of the platform.

36. OHE INSULATORS
25 KV support Insulator / Pedestal insulators
This type of insulators are used in single pole isolators, double pole isolators and in bus bar
arrangements.
25 KV tie rod insulators
This type of insulators are used in single pole isolators, double pole isolators arrangements.
Section Insulator:
A device installed in the contact wire for insulating two elementary electrical sections from each other
while providing a continuous path for the pantograph without break of current.

37. OHE JUMPERS
Jumpers:
A jumper is a conductor or an arrangement of conductors, not in tension, used for electrical
connection between two conductors or equipments.
Types of Jumpers are:
a)In span Jumpers or “H” Jumpers
b)Turnout /Un-insulated overlap Jumpers or “G” Jumpers
c)Potential Equalizing Jumper of “F” Jumpers

38. OHE ISOLATOR
ISOLATOR:
Function of isolator is to make and break the Electrical continuity of an
Elementary section. The picture shows the view of the Single Pole Isolator. In
major yards where loading and unloading of materials are involved Double Pole
Isolators with Earthling Heels are being used.

39. OHE TRANSFORMER
AUXILIARY TRANSFORMERS
230 V single phase power supply required for operation of substation equipment, lighting of
the station yard, tunnels and working of colour light signals, is obtained through 25 kV / 230
V, 100/10/5 Kva, 50.Hz. single phase LT supply transformer.
It is provided at substations feeding and switching posts, stations, block-huts and at other
outdoor locations e.g. level crossings with gate signals.
Capacity:
LT supply transformers are of 5/10/25 kVA capacity. More than one transformer are provided
at large station, yard etc.
Protection:
LT supply transformers are protected only by a 25 kV dropout fuse on the primary side and 63A fuse wire
of 20 SWG tinned copper wire on the secondary side.

40. OHE TRANSFORMERS
Mounting arrangement:
The LT supply transformer is mounted on steel platform erected on the OHE mast and
connected to the 25 kV OHE through rigid aluminum bus-bar or 50 mm2 copper jumper
wire.
Substation LT supply:
At substation, in order to provide power to single phase transformer oil centrifuging /
filtration plant, 100 kVA`, 25 kV/ 230V, 50 Hz single phase transformers are provided.

41. OHE TRANSFORMERS
Booster Transformers
Booster Transformers wherever necessary for suppression of inductive interference of P&T
communication lines running in close vicinity and parallel to 25 kV OHE may be provided
separately for each running tracks. The primary winding of the booster transformer is connected
in series with the OHE at insulated overlaps.
The Booster transformers are located at an approximately spacing of 2.66 km between each
other.

42. OHE TRANSFORMERS
The location of the booster transformer should be decided considering the following aspects.
a) At feeding posts and sectioning and paralleling posts the booster transformers should be
located equidistant on either side so that the mid-point falls in front of these switching stations.
b) In exceptional circumstances where the booster transformers are not placed equidistant from
the feeding post or sectioning post, it must be ensured that the distance of the booster
transformer from FP or SP does not exceed 1.33 km.
c) The booster transformer should not be located:
In the vicinity of the stop signals to avoid bridging of insulated overlap by locomotives
pantograph.
Within the station limits except for very big stations

43. OHE RETURN CONDUCTORS
Route
In deciding the route of return conductors the obstructions in route should be taken into
consideration. Besides, adequate physical and electrical clearances should be maintained from
fixed structures.
The general objectives is to run the return conductor as close as possible to the associated
overhead equipment so as to secure maximum compensation. Subsidiary lines such as sidings,
loops etc are not provided with return conductors
The return conductor will be normally run on the traction masts on the same side as the
overhead equipment.

44. OHE RETURN CONDUCTORS
Clearance:
The static and dynamic clearance to any part of the return conductor from an earthed structure
should be 150 mm and 80 mm respectively.
The clearance between the return conductor and the overhead equipment should not be less
than 400 mm under the worst conditions.
At over-bridges return conductors may be run straight through, if possible, as on normal
structures.

45. OHE RETURN CONDUCTORS
Return conductors in complicated areas:
In station areas, having complicated track layout. It may not be practicable to position the return
conductor sufficiently close to the associated overhead equipment to secure the required
compensation. In such cases, the route of the return conductor should be decided on the merits
of each case. Care being taken to avoid running of return conductor over platforms.
Tension lengths of return conductors:
Return conductors are normally terminated at the masts where the return conductors are
connected to the rail. They may be anchored back to back at such masts.

46. OHE RETURN CONDUTORS
Connections to booster transformers : - At all booster stations, the return conductors for each
track should be provided with a cut-in-insulator. The return conductor is connected in series with
the secondary winding of the booster transformer.
(i) The mid-point of return conductor shall be connected to the buried rail. The mid-point is
defined as a mid point between two consecutive booster transformers.
(ii) Mid-point of the return conductor before feeding posts shall be connected to the buried rail
on either side of the insulated overlap and in case of sectioning posts shall be connected on
either side of the neutral section.

47. OHE RETURN CONDUCTORS
(iii) In exceptional circumstances, where mid-point does not fall in front of feeding posts and
sectioning posts, the two rail links between return conductor and rail should be provided in front
of feeding posts and sectioning post on either side of the insulated overlap / neutral section. In
these cases, mid-point should not be connected to rail.

48. Power Quality Issues in Railway
Electrification
Since the beginning of railway electrification, power quality has been a main problem in railway
networks because of their special characteristics.
Many ways of power quality improvement have been investigated an applied to ac and dc
traction systems through railway electrification history.

49. Power Quality Issues in Railway
Electrification
System Imbalance:-
Most trains are single phase and a single-phase load produces a current NSC as much as a PSC. If
these NSCs are not attenuated, then the NSC ratio is 1, and since a traction load is large, it may
harm the power system and must be compensated.
Harmonic:-
Urban dc traction systems using 12-pulse rectifiers generate large amounts of the 11th- and 13th-
order harmonics, and for ac traction systems, trains use ac/dc/ac converters causing different
harmonics flowing into the three-phase power system. There also may be a dc component
injected into the ac system

50. Power Quality Issues in Railway
Electrification
Reactive Power:-
Modern ac converters of traction motors use pulse width modulation (PWM), which generates
zero reactive power and for power quality compensators, the power factor is 1 as well.
Voltage Problems:-
The most frequent problems of voltages are associated with their magnitudes. As noted before,
unbalanced currents produce unbalanced voltages.

51. Power Quality Issues in Railway
Electrification
Impacts on signaling and communication:-
Track circuits are designed to work with a special frequency that must not have any interference
with the power frequency. However, in the presence of harmonics, communication signals may
be affected by harmonic frequencies.
Impact on upstream network:-
Decrease utilization factor,
Malfunction of a protective system,
Incorrect operation of transmission line control system.

52. Power Quality Issues in Railway
Electrification
Power Quality Improvement methods:
Configuration based classification:-
In the first decades of the 20th century, some countries such as Italy, U.S., and Switzerland designed
three-phase trains to achieve a symmetric three-phase load, which included two pantographs for two
phases and running rails as the third phase.
Power Source-Based Classification:-
The delta–wye-type transformer is the most conventional in the power industry, but in case of
traction application.

53. Power Quality Issues in Railway
Electrification
Power Quality Improvement methods:
Equipment-Based Classification:-
There are some electric equipment for the improvement of power quality problems such as
passive and active filters used for harmonic elimination.
Active power quality conditioner (APQC), and hybrid power quality conditioner (HPQC)
compensate both the current NSC and reactive power as well as perform harmonic elimination.

54. Power Quality Issues in Railway
Electrification
Power Quality Improvement methods:
Theory Based Classification:-
Steinmetz Law:-
A single-phase resistive load between a and b phases which is equal to G can be symmetrized by
an inductive load between a and c phases equal to G/√3 and a capacitive load between b and c
phases equal to −G/√3

55. Power Quality Issues in Railway
Electrification
Power Quality Improvement methods: