OHE & PSI
RAILWAY PROJECTS
By: Anubhav Kumar Jain
(Manager)
Mo. : 7310109435
RAILWAYS
1
IN THIS SESSION WE WILL DISCUSS ABOUT
Introduction of traction System
Type of traction system
Need of traction System
Sectioning and power supply arrangement of traction system .
Different Activity of PSI.
Different Activity of railway electrification
Importance of Bonding and earthling in railway electrification .
OHE & PSI
Railway Traction
System
History of electric Traction
In 1879 the first
electric train run was
run on 31st May in the
Industrial fair at Berlin
by Earnest Warner
Siemens,3HP dc series
motor was used and
speed was 6-7 KMPH
In 1907,M/S Siemens
manufactured 1 phase
Traction system,15 KV,
25C/S,162/3rd C/S.
This system is also
developed in
Americain 11KV,25C/S
In 1936 the first steps
to wards 50 c/s
traction as known
today was taken by
Germany when they
electrified 35 miles
Hattenthal Railways in
black forest
History of electric Traction in India
Electric traction took
birth in India in 1925
when 10 miles
between Bombay VT
– Kurla of the
Central Railway was
Electrified with 1500
volt DC.
SheoraphuliTarakeswar branch
line on 3000 V dc
system. This work of
142 RKM or 423
TKM was completed
in Aug. 1958.
In 1960 first
electrification on
single phase , 25kv
50 c/s traction
system was done
RKSN-DPS section
Why 25 KV have been adopted
In the initial stage 15KV, 16⅔
c/s had attended perfection.
Later on when it was wanted
to change this system to 50c/s
Industrial frequency so as not
to change the equipment of
15KV two consideration taken
into account :-
To have same drawl of power
so that no of trains need not
be changed
To have same inductance
drop so that protection
equipment need not be
changed.
Why 25 KV have been adopted
Let V1 I 1 cosθ1 XL1 are the voltage, current power factor and impedance for 15KV 16⅔ c/s and V2 I2 cosθ2 XL2
are the voltage, current power factor and impedance for 25KV, 50c/s
Now for transmitting same power in same power factor.
V1 I1 cosθ1 = V2 I2 cosθ2
V1/ V2= I2/ I1 [cosθ1 = cosθ2]
For same percentage of Impedance drop
I1 X L1/ V1= I2 XL2/V2
I1/I2= V1 XL2/ V2 XL1
V2/V1= V1 2πf2/ V2 2πf1
[V2]2 = [V1]2 f2/ f1
V2= V1√ [f2/ f1]
V2= 15√ [50x3/ 50]
V2= 15√3=25KV [16⅔= 50/3]
Type Electric Traction Systems
• Direct Current (DC) electrification system
• Alternating Current (AC) electrification system
• Composite system.
DC Electrification System
• In this type of system, three-phase power received from the power
grids is de-escalated to low voltage and converted into DC by the
rectifiers and power-electronic converters.
AC Electrification System
• The Single phase 25KV at 50Hz is the most commonly used
configuration for AC electrification. It is used for heavy haul systems
and main line services since it doesn’t require frequency conversion.
This is one of the widely used types of composite systems wherein
the supply is converted to DC to drive DC traction motors.
Composite System
• Composite System (or multi-system) trains are used to provide
continuous journeys along routes that are electrified using more
than one system. One way to accomplish this is by changing
locomotives at the switching stations. These stations have overhead
wires that can be switched from one voltage to another. Another
way is to use multi-system locomotives that can operate under
several different voltages and current types. In Europe, it is common
to use four-system locomotives. (1.5 kV DC, 3 kV DC, 15 kV 16⅔ Hz
AC, 25 kV 50 Hz AC).
Principal of traction system
• There has to be a closed electrical circuit in order for the current to
flow and the train to move. The circuit can be completed through
the train wheels to the rails/rail with With Return Wire and then by
connecting them back to the feeder substation.
AC Electrification System
AC Electrification System
Current Rating of 25Kv Traction system
• The Catenary wire comprises 19 strands of cadmium copper, having
about 80% conductivity and 65 sq. mm cross-sectional area. The
contact wire is a solid hard drawn grooved copper of 12.24 mm dia
and 107 sq. mm cross-sectional area.
• Total effective cross-sectional area of both the Wire =
(107x 98%)+(65x80%) (Cross-section x Conductivity)
=156.8
• Conductivity of 1mm cross-sectional area Copper = 4 A
• Total conductivity of 25KV Traction system (contact wire-107 Sqmm
+ Catenary wire- 65 Sqmm ) = (156.8 x 4) A
= 600 A (Equivalent)
• The total current carrying capacity is 600 Amps.
Current Rating of TSS
• No voltage load :
•
Primary side
= 132 KV
•
Secondary side =
27KV
•
Secondary voltage at rated output
•
Rated out put
= 21.6 KV
•
Rated secondary current
= 25 KV
= 21.6 MVA = 800 A
27 KV
Drawings for Railway Electrification OHE
1. L-section.
2. ESP- Engineering scale plan.
3. Pre –pegging plan.
4. PSD- Power supply diagram.
5. SIP- signal Interlocking Plan.
6. Sectioning diagram.
7. Pegging Plan.
8. LOP- Layout plan.
9. CSD- Cross section Drawing.
10. SED- structure errection Drawing
11. AED- As erected Drawing.
Drawings for Railway Electrification PSI
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Traction Sub Station Drawings
Location Plan and Schematic Diagram
GAD and Bus bar Layout
Fencing Layout
Structure Assembly Layout
Foundation & Stub Details Drawing
Cable Trench Layout
Cable run Layout
Earthing Layout
Control Room Building
Baffle wall Drawing
Transformer Oil drainage arrangement
Oil soak pit drawing
As-Built Drawings
• Switching Station Drawings
• Location Plan and Schematic
Diagram
• GAD and Bus bar Layout
• Fencing Layout
• Structure Assembly Drawing
• Foundation Layout
• Cable Trench Layout
• Cable run Layout
• Earthing Layout
• As-Built Drawings
Sectioning of OHE
The overhead equipment is divided electrically into sections using neutral
sections, insulated overlaps, uninsulated overlaps and section insulators .
Under normal working conditions, electrical continuity is maintained by
bridging the insulated overlaps by means of interrupters or isolators. (OTHER
THAN SWITCHING STATION SINGLE POLE ISOLATOR IS TO BE PROVIDED )
Isolation of small sections of OHE for maintenance and repairs is possible.
Sectioning of OHE should be kept to a minimum in consistence with
operational requirements.
Excessive sectioning, results in having a large number of insulators,
overlaps, terminations, isolating switches, fee der wires, section insulators
etc. These can reduce reliability while increasing the need for maintenance.
Main Principles of Sectioning
a)Main running lines and loops should be electrically separate from
secondary lines and yard lines.
b)On double track section, OHEs of Up and Down tracks should be
electrically separate unless it is inevitable. The OHEs of Up and
Down lines should be supported on separate structures.
c) Lines for different activities should be electrically separate. In yards,
reception, dispatch, common exit and entry lines, engine run around
lines, loco shed lines and sidings should be separated from each other.
d) Electric locomotive lines used for locomotive pit lines, and sidings
where open wagons are loaded or unloaded, should be specially isolated
at both ends through short neutral sections and shall be provided with
earthing arrangement for the dead section at both ends, for the safety of
personnel working close to OHE.
Stations with loop line:
CL OF STN.
120 m
120 m
FIG.3.12.2
The first
loop line
adjacent to
the main
line is
normally
designed
to be in the
same
elementary
section as
the main
line.
Stations provided with emergency cross
over and loops
CL OF STN.
850 m
B
A
120 m
850 m
FIG.3.12.4
120 m
• Where
space is
available,
the
insulated
overlap
and the
isolator
should be
provided
between
the points
A and B as
shown in
Fig.
3.12.4.
Stations having a group of common
loops on one side
CL OF STN.
120 m
B
A
120 m
COMMON LOOP
120 m
FIG.3.12.7
• Sectioning
arrangement
shown
in
Fig.3.12.7
should
be
followed.
Power supply arrangement
FIG.1.3.4
A SAMPLE OF GENERAL SUPPLY DIAGRAM
OBBREVIATIONS:- 1. BM
: MAIN INTERRUPTOR.
2. BS
: YARD INTERRUPTOR.
3. CB
: CIRCUIT BREAKER.
4. UVR : UNDER VOLTAGE RELAY.
FROM TRACTION SUB STATION
: INTERRUPTOR.
5.
CB
CB
6.
: CIRCUIT BREAKER.
TO LOCO SHED
BM
BM
BM
BM
BM
BM
BM

CB
BM
BM
BM
BS
DN
DN
BM
BM
BM
UP
UP
NEUTRAL SECTION / INSULATED OVERLAP
SUB SECTOR
TO YARD
BM
SUB SECTOR
SUB SECTOR
SECTOR
FEEDING
POST
(F.O)
SUB SECTIONING
& PARALLELING POST
(S.S.P)
BM 
SUB SECTIONING
& PARALLELING POST
(S.S.P)
 U.V.R
SECTIONING
& PARALLELING POST
(S.P)
The power supply system includes
• Receiving 2 phases of 220/132/110/66 power in TSS premises
• Traction Sub Station-TSS
• Feeding Post (FP)
• Sectioning and Paralleling Post (SP)
• Sub Sectioning and Paralleling Post (SSP)
Traction Sub Station-TSS
The traction substations are normally separated from 50 to 60km
depending on the traffic density. 21.6 MVA transformers are used
presently, Neutral sections are provided in between two adjacent
substations to prevent the bridging of different phases while passing the
electric locomotive. The level of voltage is reduced from 220/132/110/66
kV to 25 KV for the end-use of locomotives by 21.6 MVA signal phase
power transformers placed at traction sub stations.
FUNCTIONING OF TRD SYSTEM
132 kV side
Transformer
25 kV side
Low Voltage CB
Feeder CB
Interrupter
TSS Main Components
• 132 KV side
• 132 KV Double pole isolator
• 132 KV current transformer
• 132KV Circuit
breaker
• 120 KV lightening arrestor
• 21.6 MVA/132/27 KV traction
transformer
• 132 KV porcelain insulators
•
•
•
•
•
•
25 KV side (LV)
25 KV current transformer
42 KV lightening arrestor
Capacitor bank & series reactor
25 KV circuit breaker
25 KV single pole
isolator
• 25 KV potential transformer( for
protection)
• 25 KV bus coupler interrupter.
• 25 KV porcelain insulators
Traction Sub Station-TSS
Traction Sub Station-TSS
Incoming ac BUS
DPI
Incoming ac BUS
X connection DPI
DPI
DPI
DPI
CT
CT
HV CB
HV CB
LA
LA
TRACTION
TRANSFORMER
TRACTION
TRANSFORMER
Bushing CTs
6/29/2022
31
25 KV FEEDING
ARRANGEMENT
TRACTION
TRANSFORMER
Bushing CTs
CT
42 kV LA
25kV CB
SP Isolator
AT 10 kVA
AT 25 kVA
Bus Coupler
Interrupter
DP Isolator
PT
DP Isolators
IOL
6/29/2022
CT
PT
25kV Feeder CB
SP Isolator
25 kV
Interrupter
PT
LA
DN line
Up line
32
Execution of TSS
S.NO
1
2
3
4
5
6
7
8
9
10
11
12
DESCRIPTION
132KV Equipment Foundation
25KV Equipment Foundation
Fencing Foundation
Baffle wall
Building
Fencing Panel Erection
Structure Erection
Equipment's Erection
CR Room Equipment's Erection
Earthing
Cabling
Testing
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.
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 equipments of
two different tracks. This normally remains in closed
position to reduce the voltage drop.
FP- Feeding Post
The 25kV AC power from the substation is normally led by two feeder
Wires to a feeding post. Normally both feeders supply power to the OHE.
For Single line section there will be a minimum of Two interrupters and
for Double line section there will be a minimum of four interruptors. As
the interruptor will require periodical maintenance, arrangements are
made for its total isolation by a double pole isolator. The two incoming
feeders from the traction substation are kept separate at the feeding
post.
Arrangement
FP-Sectioning
Feeding Post
TSS
FP
SSP
Sub Sector
SP
Sub Sector
Sector
37
FP- components
• 25 KV interrupter
• 25 KV double pole isolator
• 25 KV potential transformer
• 42 KV lightening arrestor
• 25 KV porcelain insulator
SP- Sectioning and Paralleling post
The layout of the SP is similar to the feeding post ( FP) except that in SP
there are no incoming feeders. Being the tail end of the feed from the substation the sectioning post is also to act as a paralleling post for the feeds
on either side. Bridging interrupters are provided at the sectioning post in
case the feed has to be extended because of any difficulty at a sub-station.
To prevent short circuit between adjacent sections, Neutral Sections are
provided. The portion of the OHE between a Feeding Post and the next
neutral zone on one side is called a section of the traction supply. A
Sectioning and Paralleling Post (SP) is provided near the neutral zone, that
has two paralleling Interrupters to keep the two portions of the OHE (one in
each direction) supplied in parallel. For bridging, Since the neutral section
remains ‘dead’ warning boards are provided in advance to warn and remind
the Driver of an approaching electric locomotive /EMU to open locomotive
CircuitBreaker (DJ) before approaching ‘neutral section’.
SP- Sectioning and Paralleling post
SP- Sectioning and Paralleling post
LA 42 kV
LA 42 kV
Neutral
Section
LA 42 kV
DPI
Paralleling Intr
LA 42 kV
AT
PT
Bridging
Interrupter
09/03/2016
SP
41
Sectioning and Paralleling post- components
• 25 KV interrupter
• 25 KV double pole isolator
• 25 KV potential transformer
• 42 KV lightening arrestor
• 25 KV porcelain insulator
• 10 KVA 25 KV/240 V
SSP- Sub-Sectioning and Paralleling post
Depending on the distance between an FP and SP (Feeding post to a
Neutral section) 1 to 3 Sub sectioning and paralleling posts are created.
This is the simplest of all posts as its purpose is only to sectionalize/
parrallel the different sections of the overhead equipment. Paralleling
interrupters are provided at SSP to parallel the Up & Down track OHE, in
order to reduce the voltage drop and to facilitate movement of traffic in
case one subsector or one or more elementary section is faulty or taken up
for maintenance.
SSP- Sub-Sectioning and Paralleling post
SSP- Sub-Sectioning and Paralleling post
DPI
PT
LA 42 kV
LA 42 kV
IOL
DPI
Paralleling INTR
IOL
LA 42 kV
LA 42 kV
PT
AT
Sectioning
Interrupter
09/03/2016
SSP
45
Sub-Sectioning and Paralleling post- components
• 25 KV interrupter
• 25 KV double pole isolator
• 25 KV potential transformer
• 42 KV lightening arrestor
• 25 KV porcelain insulator
• 10 KVA 25 KV/240 V
TESTINGand
ANDother
JOINT CHECKING
OF SUB STATIONS AND SWITCHING
Safety
Eqipments
STATIONS :
• Sub station has equipment on 132 & 25 Kv which includes transformers, lighting
arrestors, circuit breakers, isolators, interrupters, etc. The sectioning stations
have specified earthing requirements for equipment, entire system on 132 as
wlll as 25 kv side and on LT i.e. control room area. Certain safety equipment are
to be provided in these locations availability of which are to be ensured.
i) TRACTION SUB STATION
• Shock treatment chart
• Fire bucket stand
• Fire extinguishers
• List of doctors within the vicinity of traction sub station
• P&T phone
• Discharge rod
• First aid box
ii) SWITCHING STATIONS
• Shock treatment chart
• Fire bucket stand
• Fire extinguishers
• Discharge rod
47
2 X 25 KV SYSTEMS
Experience of Indian Railway
 In 1986 Indian Railway decided to
award a consultancy contract to
JEC
through
RITES
Traction System.
for
2x25kV
2 X 25 KV SYSTEMS
Experience of Indian Railway
 The
2X25kV
commissioned
System
in
has
BINA-
been
KATNI-
ANUPPUR- BISHRAMPUR / CHIRMIRI
Section in 1995 for regular running
of Train Services.
2 X 25 KV SYSTEMS
Experience of Indian Railway
 The consultancy contact for Design of
2X25kV System was awarded by RITES to
Japan Electrical Consulting Co. Ltd. (JEC).
 JEC
designed
specifically
the
2x25kV
as
requirements/conditions
Section of Indian Railway.
per
of
System
the
BINA-KATNI
2 X 25 KV SYSTEMS
Experience of Indian Railway
 This
was
later
extended
to
KATNI-
ANUPPUR-BISHRAMPUR/CHIRMIRI Section.
 In
this
section
4
Nos.
TSS
have
been
provided with spacing of TSS at an average
of 80Km.
BRIEF DESCRIPTION OF THE 2 X 25 KV SYSTEMS
• In 2x25 kV system, power is fed from the TSS at 50 kV and utilization is achieved at 25 kV by
providing Auto-transformers of adequate capacity and by providing one additional conductor
normally referred as feeder wire (similar to the return conductor in BT/RC system). Centre point
of the Auto Transformer is connected to the earth/Rail. This arrangement facilitates +25 kV
Voltage between OHE and rail and -25 kV voltage between earth/Rail and the Feeder Wire.
2 X 25 KV SYSTEMS
Advantage of 2X25kV system
• (a) The 2X25 kV AT feeding system is suitable to meet larger power supply needs with the inherent advantage of
less voltage drop in feeder circuit for a given spacing of traction substations. To meet the larger power supply
requirements, 2X25kV system is used in various countries including DFCCIL in India. File No.RDSOTI0LKO(PSI)/1/2022-O/o PED/TI/RDSO Page 4 of 27
• (b) Power is generally obtained from 220 kV or 132 kV three phase networks from the power utility to reduce
voltage unbalance on the transmission network. In the 2X25kV TSS, the three phase supply is utilized at the
Traction Sub-station.
• (c) The 2X25 kV Auto Transformer (AT) system is having feeding voltage of 50 kV from the substation which is
dropped to 25 kV by the AT installed at about 10 to 18 Km spacing along the track for supply to overhead
equipment and rolling stocks. A pilot project for this system was provided in Bina-Katni Section. The design of the
system was done with the help of Japanese Consultants.
• (d) Better voltage regulation even at higher load currents.
• (e) Minimized rail currents resulting in reduction in rail potential rise. Return current through ground also reduces
considerably.
• (f) In 2X25kV system, the return current flows through the feeder wire. Since the direction of current in the
feeder wire is opposite to the direction of current in the catenary wire, it minimizes the effect of the
electromagnetic Interference in the proximity of the traction line.
• (g) Preferred solution across the globe to meet higher power requirement for Traction Purpose.
TYPE OF TRACTION SUB STATION (TSS) IN 2X25kV SYSTEM
• Mainly Two Types of Traction Sub-Station are used in 2X25kV System.
• Traction Sub-Station with Scott connected Transformer.
• Traction Sub-Station with three Single Phase Transformer (V connection or Open Delta).
Scott Connected Transformer Scheme
• In this scheme two Scott connected Transformers & four Auto-transformers are to be installed at
a TSS along with associated switchgear for Control & protection. The two windings of a Scott
transformer i.e. Main and Teaser windings are of equal power rating and feed either side of the
TSS independently. The supply of both the windings is at a phase difference of 90 degree and
separated by neutral section provided near TSS. Out of two Scott transformers, only one is in
operation and the other is on standby.
Scott Connected Transformer Scheme
Scott Connected Transformer:
• Scott- connected transformer of 60/84/100 MVA (ONAN/ONAF/OFAF) is used to feed power to
the traction system. It has a voltage input of 220kV or 132kV, 3 phase, 50 Hz and two
independent secondary winding for output at 50 kV. The Transformer has two secondary
windings, known as the main winding and teaser winding. The two windings are identical in
voltage and current rating but are in phase difference of 90 degree. These two windings of equal
power rating i.e. Main & Teaser windings, feed power on either side of the TSS. The feed of
different phase is separated by neutral section provided near TSS. The Scott Connected
Transformer in ONAN Mode shall feed the 30MVA Power to each side of the TSS.
Auto Transformers:
Auto- transformers are used at TSS, SP and SSP. The transformer winding of 50kV with Centre tapped neutral with both
the terminals of the Autotransformer winding connected to feeder and contact /Catenary wire. The neutral terminal of
the ATs is connected to rail. Two adjacent ATs feeding on the network share train loads on the section between them
and transfer the load current on 25 kV circuit to 50 kV circuit, consisting of contact wire and AT feeder. This reduces the
voltage drop on feeding network remarkably. Furthermore, it minimizes the return current on the rail, which results in
reducing induced voltage on nearby telecommunication lines. In the Scott connected arrangement for 2 Line section,
12.3 MVA Auto transformers are to be installed at the TSS and 8MVA Auto transformers to be used at the SP & SSP, as
adopted by DFCCIL in Western Corridor. Further, the Scott connected arrangement for 3 Line and 4 line sections have
been provided with 12.3 MVA auto transformers at TSS and 16.5 MVA auto transformers at SP/SSP. Moreover, no
independent AT post has been proposed in any scheme.
V Connected Transformer Scheme:
• In this scheme, three single phase transformers are connected to different pairs of three phase
of incoming supply forming an open delta connection on the primary side. Out of the three
single File No.RDSO-TI0LKO(PSI)/1/2022-O/o PED/TI/RDSO Page 5 of 27 phase transformers, first
transformer feeds the OHE on one side of the TSS, second transformer (mid one) remains as
standby and third transformer feeds the OHE on the other side of the TSS. The power supply on
either side of TSS is at a phase difference of 120 degree and therefore separated by a neutral
section provided near TSS.
V- Connected Transformer:
• In the above arrangement, three 38/53/63 MVA (ONAN/ONAF/OFAF) Transformers are provided
at TSS along with associated switchgear for Control and Protection. Each single phase
transformer has a voltage input of 220kV or 132kV, 50 Hz and two independent secondary
windings, to be connected externally in such a manner (two inner terminals of these secondary
windings are connected with each other and also connected to earth/Rail) so as to give an
output voltage of 2X25kV. The outer terminals of the windings are connected to Feeder wire and
overhead contact/catenary wire respectively. Two transformers shall be in operation at a time
and one shall be on standby. In the V connected Scheme, each transformer in ONAN mode shall
feed the 38MVA Power in either side of the TSS.
V- Connected Transformer:
Auto Transformers:
• i. Auto- transformers are used at SP and SSP. The transformer winding is 50 kV with Centre
tapped neutral with both the terminals of the winding connected to AT feeder and the contact
wire. The neutral terminals of the ATs are connected to rail.
• ii. Two adjacent ATs feeding on the network share train loads on the section between them and
transfer the load current on 25 kV circuit to 50 kV circuit, consisting of contact & catenary wire
and AT feeder. This reduces the voltage drop on the feeding network remarkably. Furthermore,
it minimizes the return current on the rail, which results in reducing the induced voltage on
nearby telecommunication lines.
• iii. Auto transformers are not used at the TSS. However, these have been provided at SP/SSP of
16.5 MVA capacities. Moreover, no independent AT post has been proposed.
Spacing of the TSS & Switching post (SP/SSP)
• Two-line section – Considering the load requirement of 0.5MVA/TKM in ONAN mode on the
main line section, the spacing of TSS in Scott connected scheme of 60-70 Km is suggested. In the
proposed V connected scheme, the transmission of full power from the transformer is not at 50
kV and therefore the spacing of the TSS in V connected scheme for 2 Line system has been kept
same as in Scott connected scheme i.e. 60-70 KM with power requirement of around
0.6MVA/TKM in ONAN mode.
• Three line sections – In the 3 Line section, the loading in MVA/TKM basis will be less than the 2
line system as all the three lines will not be fully loaded at a time. Therefore, the load
requirement of around 0.4 MVA/TKM in ONAN Mode for 3 Line section has been considered and
accordingly the spacing of TSS in Scott connected scheme is suggested as 50-60 KM. In the
proposed V connected scheme for 3 line, the transmission of full power from the transformer is
not at 50 kV and therefore the spacing of the TSS in V connected scheme for 3 Line system has
been kept same as in Scott connected scheme i.e. 50-60 KM with power requirement of around
0.5 MVA/TKM in ONAN mode.
• Four line section– In the 4 Line section, the loading in MVA/TKM basis will be less than the 3 line
system as all the four lines will not be fully loaded at a time. Therefore, the load requirement of
less than 0.4 MVA/TKM in ONAN Mode for 4 Line section has been considered and accordingly
the spacing of TSS in Scott connected scheme is suggested as 40-50 KM. In the proposed V
connected scheme for 4 line, the transmission of full power from the transformer is not at 50 kV
and therefore the spacing of the TSS in V connected scheme for 4 Line system has been kept
same as in Scott connected scheme i.e. 40-50 KM with a power requirement of around 0.5
MVA/TKM in ONAN mode.
Scott connected vs V Connected Scheme
• i. Considering the three phase utilization equally in the Scott Connected scheme, it is better in
reducing the unbalancing at point of common coupling with the utility as compared to
VConnected scheme. The point of common coupling is already defined in the clause no. 2.2 of
RDSO Instruction no. TI/IN/0019 (09/09).
• ii. The Voltage Unbalance in Scott Connected Transformer Scheme is least and therefore the
Railways should preferably provide Scott Connected Transformer wherever the voltage
unbalance problem is seen. The detailed study regarding this is available in clause no. 2.1.13 of
Chapter 1, Part-II in Volume-1 of Treatise on Electric Traction Distribution, which can be readily
referred (page no. 125 of Volume-1).The problem of unbalancing has been raised by few power
utilities and therefore Scott or V connected arrangement should be chosen judiciously after
coordinating with the power utilities.
• iii. Scott Connected Transformer is more complex and costlier than the V connected
Transformer but Scott connected Transformer effectively checks the voltage unbalance. iv.
Initially, in Bina-Katni Section of IR, the Scott Connected Transformers were imported; however,
Transformers for V connected scheme were supplied by an Indian Manufacturer.
• v. The maintenance/Overhauling of the Scott Connected Transformer is more complex in
comparison to Single Phase Transformer. V connected scheme is economical in comparison to
Scott Connected scheme.
• vi. Since, no AT is to be used at the TSS of V connected scheme; it is simpler than Scott
Connected scheme.
Traction Sub StationTSS
SITE PHOTOGRAPHS
SITAPUR AEE OFFICE
SITAPUR TYPE-II BLOCK-1
SITAPUR PSI DEPOT
SITAPUR TYPE-II BLOCK-2
SITAPUR TYPE-II BLOCK-3
SITAPUR TYPE-IV BLOCK-1
PHARDHAN PSI DEPOT
SITAPUR TYPE-II BLOCK-4
SITAPUR TYPE-III BLOCK-1
SITE PHOTOGRAPHS
SITAPUR AEE OFFICE
SITAPUR TYPE-II BLOCK-1
SITAPUR PSI DEPOT
SITAPUR TYPE-II BLOCK-2
SITAPUR TYPE-II BLOCK-3
SITAPUR TYPE-IV BLOCK-1
PHARDHAN PSI DEPOT
SITAPUR TYPE-II BLOCK-4
SITAPUR TYPE-III BLOCK-1
SITE PHOTOGRAPHS
SITAPUR AEE OFFICE
SITAPUR TYPE-II BLOCK-1
SITAPUR PSI DEPOT
SITAPUR TYPE-II BLOCK-2
SITAPUR TYPE-II BLOCK-3
SITAPUR TYPE-IV BLOCK-1
PHARDHAN PSI DEPOT
SITAPUR TYPE-II BLOCK-4
SITAPUR TYPE-III BLOCK-1
SITE PHOTOGRAPHS
SITAPUR AEE OFFICE
SITAPUR TYPE-II BLOCK-1
SITAPUR PSI DEPOT
SITAPUR TYPE-II BLOCK-2
SITAPUR TYPE-II BLOCK-3
SITAPUR TYPE-IV BLOCK-1
PHARDHAN PSI DEPOT
SITAPUR TYPE-II BLOCK-4
SITAPUR TYPE-III BLOCK-1
Choice &Location of site
The choice and location of sub-station sites are of prime importance. A farsighted policy is essential in the selection of sub-station sites. The site
selected should permit bringing in and taking out the feeders, both incoming
HT and outgoing 25 kV.
Adequate access from a public road is desirable for traction sub-stations to
facilitate handling of plant. A Railway siding will be an advantage if it can be
conveniently provided. The site for substations must be free from water
logging , should preferably be a site which requires less or no filling for
leveling . It is further desirable to locate the site near overlaps, if OHE already
exists. Though teeing-off method is simple and cheap but it does not afford
the facilities necessary on an important higher voltage network.
Where outdoor switchgear is installed, it is necessary to provide a room for
the control equipment, protective relays, instruments and testing
equipment. This building should have a room set apart for the maintenance
personnel who will be required to work under varying conditions in an
emergency.
TYPICAL SCHEMATIC OF TRACTION POWER SUPPLY FEEDING ARRANGEMENT
INCOMING EHV SUPPLY
(220/132/110/166kv
DP
ISOLATOR
CT
CIRCUIT BREAKER
LIGHTNING
ARRESTER
TRACTION
TRANSFORMER
25 kv
CT
TO BURIED RAIL &
NEAREST RUNNING
TRACK
25 KV SP ISOLATOR
NORMALLY CLOSED
42 kv LIGHTNING
ARRESTER
25 kv CIRCUIT BREAKER
25 kv CT
25 kv SP ISOLATOR
100 kva, 25 kv/240 VLT SUPPLY
25 kv SP ISOLATOR TRANSFORMER
25 kv CT
25 KV/110V PT
(PROTECTION)
25 kv FEEDER CIRCUIT BREAKER
25 kv SP ISOLATOR
25 kv BUS COUPLER
INTERRUPTOR
(NORMAL OPEN)
25 kv INTERRUPTOR
25 kv SP ISOLATOR
25 kv PT
SUB SECTIONING &
PARALLELING STATION (SSP)
42 KV LA STATION TYPE:
HEAVY DUTY
SUB - SECTOR
SECTIONING AND PARALLELING POST (sp) S P
SUB - SECTOR
SUB - SECTOR
SECTOR
BRIDGING
INTERRUPTOR
 This code of practice caters for general arrangements
of system and equipment earthing at 220/25 kV or
132/25 kV or 110/25 kV or 66/25 kV traction
substations, 25 kV switching stations, booster
transformer stations and auxiliary transformer
stations.
 Low voltage (LT) electrical power distribution
system, 25 kV overhead equipment system as well as
signal and tele-communication equipment do not
come within the purview of this code.
• The following terms wherever occurring in this code
shall, unless excluded or repugnant to the context,
have the meaning attributed thereto as follows:
Combined Earth Resistance:
• The resistance of an earth electrode(s) with respect to
earth, with the earth electrode(s) connected to the
metal work of electrical equipment other than parts
which are normally live or carry current and the
mast/structures but without connection with the
traction rail(s).
Earth:
• The conductive mass of the earth, whose electrical
potential at any point is conventionally taken as zero.
Earth electrode:
• A conductor (mild steel pipe) or group of conductors
in intimate contact with and providing an electrical
connection to earth.
Earthing grid:
• A system of a number of interconnected, horizontal
bare conductors buried in the earth, providing a
common ground for electrical devices and metallic
structures, usually in one specific location.
BURIED GRID CONDUCTOR WITHIN 1 METRE OF FENCE
M.S.FLAT
SPACING AS PER CALCULATION
M.S.ROD
75mmX8mm MS FLATS
FROM POWER
TRANSFORMER
SECONDARY WINDING
TERMINAL
BURIED RAIL
WELDED AT
CROSSING
75 mmX8 mm M.S.FLATS
TO NON TRACKCIRCUITED
RAIL NEUTRAL POINT OF
IMPEDANCE BOND
Equipment earthing:
• 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.
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 thus to ensure
the security of the system.
Step Voltage (Estep):
• The potential difference between two points on the
earth’s surface separated by distance of one pace, that
will be assumed to be one meter in the direction of
maximum potential gradient.
Traction Rail:
• Traction Rail means a non-track circuited rail of a
wired track, not required for signaling purposes and
which may be earthed.
In non-track circuited
sections, both the rails of a wired track are traction
rails and in single rail track circuited sections, the
traction rail is the non-track circuited rail.
Touch Voltage (Etouch):
• The potential difference between a grounded metallic
structure and a point on the earth’s surface separated
by a distance equal to the normal maximum
horizontal reach of a person, approximately one
metre.
Object of Earthing
• The object of an earthing system is to provide as
nearly as possible a surface under and around a station
which shall be at a uniform potential and as nearly
zero or absolute earth potential as possible.
The
purpose is to ensure that generally all parts of the
equipment, other than live parts are at earth potential
and that attending personnel are at earth potential at all
times.
• Also by providing such an earth surface of uniform
potential under and surrounding the station, there can
exist no difference of potential in a short distance big
enough to shock or injure an attendant when short
circuits or other abnormal occurrences takes place.
The primary requirements of a good earthing system
are:
• It should stabilize circuit potentials with respect to ground and
limit the overall potential rise.
• It should protect men and materials from injury or damage due
to over voltage.
• It should provide low impedance path to fault current to ensure
prompt and consistent operation of protective devices during
ground faults.
• It should keep the maximum voltage gradient along the surface
inside and around the substation within safe limits during earth
faults.
Earth Resistance
• At each power supply installation, an earthing system as
specified in this Code shall be provided. The combined
resistance of the earthing system shall be not more than the
following values:S.N.
Name of the station
The limit of combined
earth resistance in Ohm
1.
Traction substation
0.5
2.
Switching station
2.0
3.
Booster transformer station
10.0
4.
Auxiliary transformer station
10.0
Earth Electrodes
1. The earth electrode shall normally be 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.
TYPICAL ARRANGEMENT OF AN EARTH ELECTRODE
• The pipe shall be 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 being limited to 30 degree
from the vertical. The connection of MS flat to each
electrode shall be made through MS links by bolted
joints to enable isolation of the electrode for testing
purposes.
2. Earth electrodes shall be embedded as far apart as
possible from each other. Mutual separation between
them shall usually be not less than 6.0 m (which is twice
the length of the electrode).
3. If the value of earth resistance specified can not be
achieved with a reasonable number of electrodes
connected in parallel such as in rocky soil or soil of high
resistivity, the earth surrounding the electrodes shall be
chemically treated.
The earth electrode shall be
surrounded in an earth-pit by alternate layers of finely
divided coke, crushed coal or charcoal and salt at least
150 mm all-round.
Though substantial reduction in earth resistance can be
achieved by coke treated electrode, yet as this method
results in rapid corrosion not only of electrode but also of
steel frame work to which it is bonded, coke treatment
shall be used only where absolutely necessary and such
electrodes shall not be situated within 6.0 m of other
metal work.
4. In high embankments, it may be difficult to achieve
specified earth resistance even after chemical treatment
of electrodes. In those locations, use of electrodes longer
than 4 m so as to reach the parent soil is recommended.
5. As far as possible, earth electrodes for traction sub-
stations/switching stations shall be installed within
and adjacent to perimeter fence. At large sites, apart
from securing a sufficiently low resistance and
adequate current carrying capacity a reasonable
distribution of electrodes is also necessary.
Earthing grid:
1. An earthing grid is formed by means of bare mild steel
rod buried at a depth of about 600 mm below the ground
level and connected to earth electrodes. The connection
between the earth electrode and the grid 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
shall be provided at the outer periphery of the grid.
As far as possible the earthing grid conductors shall
not pass through the foundation block of the
equipments.
All crossings between longitudinal
conductors and transverse conductors shall be jointed
by welding.
The transverse and longitudinal
conductors of the earthing grid shall be suitably
spaced so as to keep the step and touch potentials
within acceptable limits; the overall length of the
earthing grid conductors shall not be less than the
calculated length.
2.
The size of the earthing grid conductor shall be
decided based on the incoming system voltage and
fault level. The fault level considered shall take into
account the anticipated increase in fault current
during the life span of the station. The size shall be
as given below:
S.
System
No. Voltage kV
1
2
3
4
Fault level MVA
Diameter of the grid
conductor (MS rod)
mm
66
Upto 4000
Above 4000 upto 5000
Above 5000 upto 6000
32
36
40
110
Upto 6000
Above 6000 upto 8000
Above 8000 upto 10000
32
36
40
132
Upto 7000
Above 7000 upto 10000
32
36
220
Upto 12000
Above 12000 upto 16000
Above 16000 upto 20000
32
36
40
Buried rail
1. A steel rail of section 52 kg/m (the one used for the
railway track) and length about 13 m shall be 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 shall be made
by means of 75 mm x 8 mm MS flat between the
earthing grid and the buried rail.
The buried rail shall also be connected by means of
two separate and distinct connections made of 75 mm
x 8 mm MS flat to the rail(s) in a single-rail track
circuited section and to the neutral point(s) of the
impedance bond(s) in a double-rail track circuited
section.
2. In cases where the feeding post is located separately
away from the traction substation, the buried rail shall
be provided at the feeding post (where one terminal of
the secondary winding of the traction power
transformer of the substation is grounded).
System earthing
1. One terminal of the secondary winding (25 kV winding)
of each traction power transformer shall be earthed
directly by connecting it to the earthing grid by means of
one 75 mm x 8 mm MS flat, and to the buried rail by
means of another 75mm x 8 mm MS flat.
2. One designated terminal of the secondary of each
potential, current and auxiliary transformer shall be
connected to the earthing grid by means of two separate
and distinct earth connections made with 50 mm x 6 mm
MS flat.
Equipment earthing
• The metallic frame work of all outdoor equipments
such as transformers, circuit breakers, interrupters
and isolators, as well as steel structures shall be
connected to the earthing grid by means of two
separate and distinct connections made with MS flat;
one connection shall be made with the nearest
longitudinal conductor, while the other shall be made
to the nearest transverse conductor of the grid.
S.
Equipment
System voltage and fault level
No.
conductor
1
Equipments on 66 kV, upto 3000 MVA
the primary side 110 kV, upto 5000 MVA
of traction power
132 kV, upto 6000 MVA
transformer
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
220kV, above 10000 upto 20000 MVA
2
Equipments on the secondary side of traction power
transformer
Ground
conductor size
50mm X 6mm
50mm X 6mm
50mm X 6mm
50mm X 6mm
75mm X 8mm
75mm X 8mm
75mm X 8mm
75mm X 8mm
50mm X 6mm
3
Fencing uprights steel structures
50mm X 6mm
4
Doors/fencing panels
6 SWG G.I.
Wire
Earthing inside 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. The
earthing ring shall be 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 shall also
be connected to an independent earth electrode by means
of two separate and distinct connections made with 50
mm x 6 mm MS flat.
The metallic framework of control and relay panels, LT ac
and dc distribution boards, battery chargers, remote control
equipment cabinets and such other equipments shall be
connected to the earthing ring by means of two separate and
distinct connections made with 8 SWG galvanized steel wire.
The connections shall be taken along the wall and in recess
in the floor. All recesses shall be covered with cement plaster
after finishing the work. Connections between the MS flats
shall be made by welding.
Earthing of lightning arrestor
• In addition to the earth electrodes provided for the
main earthing grid an independent earth electrode shall
be provided for each lightning arrestor. This earth
electrode shall be connected to the ground terminal of
the lighting arrestor as well as to the main earthing
grid by means of two separate and distinct connections
made with 50 mm x 6 mm MS flat for the 25 kV side
lightning arrestors, and with 75 mm x 8 mm MS flat
for the primary side lightning arrestors.
• The earth electrode shall be provided as close as
possible to the lightning arrestor and the connections
shall be as short and straight as possible avoiding
unnecessary bends. For lightning arrestors provided
for the traction power transformers, there shall also be
a connection as direct as possible from the ground
terminal of the lightning arrestor to the frame of the
transformer being protected; this connection shall also
be made by means of two separate and distinct
connections made with 50 mm x 6 mm MS flat for 25
kV side arrestors, and with 75 mm x 8 mm MS flat for
primary side lightning arrestor.
Earth Screen
•
The area covered by outdoor substation equipments shall
be shielded against direct strokes of lightning by an
overhead earth screen comprising 19/2.5 mm galvanized
steel stranded wire strung across the pinnacles of the
metallic structures.
•
The earth screen wires shall be stung at a height as
indicated in the approved traction substation layouts (not
less than 2.5 m above the live conductors) and shall be
solidly connected to the traction substation earthing grid at
each termination by means of 50 mm x 6 mm MS flat.
Earthing of fencing uprights and panels
•
Each metallic fencing upright shall be connected to the
traction substation main earthing grid by means of two
separate and distinct connections made with 50 mm x 6
mm MS flat. In addition, all the metallic fencing panels
shall be connected to the uprights by means of two
separate and distinct connections made with 6 SWG G.I.
wire.
•
All the metallic door panels shall also be connected to the
supporting uprights by means of two separate and distinct
connections made with 6 SWG G.I. wire.
• Earthing at the point 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 shall be connected to the
main earthing grid by means of two separate and
distinct connections made with 50 mm x 6 mm MS
flat.
1. A minimum number of three earth electrodes (excluding
the one to be provided separately for the remote control
cubicle earthing) shall be provided by each switching
station, and they shall be interconnected by means of 50
mm x 6 mm MS flat forming a closed loop main earthing
ring.
2. This ring shall be connected by two separate and distinct
connections made with 50 mm x 6 mm MS flat, to the
traction 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 fault.
2. System earthing
• One designated terminal of the secondary of each
potential, current and auxiliary transformer shall
be connected to the main earthing ring by means of
two separate and distinct connections made with
50 mm x 6 mm MS flat.
3. Equipment earthing
a) All masts, structures, fencing uprights, and all outdoor
equipment pedestals including auxiliary transformer
tank shall be connected to the earthing ring by means
of two separate and distinct connections made with 50
mm x 6 mm MS flat. All fencing panels shall be
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 shall be
connected to the supporting uprights by means of two
separate and distinct connections made with 6 SWG
G.I. Wire.
b) The
metal
casing
of
potential
and
current
transformers shall be connected to the mast/structures
by means of two separate and distinct connections
made with 50 mm x 6 mm MS flat.
c) The ground terminal of lightning arrestor shall be
connected directly to the earth electrode by means of
two separate and distinct connections made with 50
mm x 6 mm MS flat. The earth electrode shall be so
placed that the earthing leads from the lightning
arrestor may be brought to the earth electrode by as
short and straight a path as possible.
4. Earthing inside remote control cubicle
• An earthing ring shall be provided inside the remote
control cubicle by means of 50 mm x 6 mm MS
flat; the earthing ring shall be run along the wall on
teak wood blocks fixed to the wall at a height of
300 mm from the floor level. The earthing ring
shall be connected to the main earthing ring as well
as to an independent earth electrode by means of
two separate and distinct connections made with 50
mm x 6 mm MS flat.
• The metal casing of LT ac and dc distribution board,
battery chargers, terminal board, remote control
equipment cabinets and other such equipments shall
be connected to the earthing by means of two
separate and distinct connections made with 8 SWG
G.I. Wire. The connections shall be taken along the
wall and in recesses in the floor. All recesses shall
be covered with cement plaster after finishing the
work.
Connections of earth strips to each other
shall be made by welding.
9. Earthing of Neutral of Local Power Supply
System
• At traction substations and switching stations
where power supply at 415 V/240 V, ac, 50 Hz, is
taken from the local supply authority and having
neutral earth at some distant point in the premises
of the supply authority, the neutral of such supply
shall also be earthed by means of two separate
and distinct connections made with 6 SWG GI.
Wire by connecting to an independent earth
electrode.
11.
Earthing Arrangement
Transformer Station
at
Auxiliary
a) The combined earth resistance at the auxiliary
transformer station shall be not more than 10
Ohm.
Normally one earth electrode is
sufficient for an auxiliary transformer station.
The earth electrode shall be connected to the
mast on which the auxiliary transformer is
mounted by means of two separate and
distinct connections made with 50 mm x 6 mm
MS flat.
In addition the mast shall be connected to the nearest traction
rail or to the neutral point of the nearest impedance bond in a
double rail circuited section by means of a 50 mm x 6 mm MS
flat.
b)
The earthing terminal on the transformer tank shall be
connected to the mast on which the transformer is mounted by
means of two separate and distinct connections made with 50
mm x 6 mm MS flat. One terminal of the secondary winding
of the auxiliary transformer shall be connected to the earthing
terminal on the transformer tank and as well as to the mast by
means of 50 mm x 6 mm MS flat. These connections shall be
as short and straight as possible and avoiding unnecessary
bends.
12. Method of Jointing
•
All the joints between the MS flats, MS rods or
between MS flat and MS rod shall be made by
welding only. No soldering shall be permitted.
For protection against corrosion, all the welded
joints shall be treated with red lead and
afterwards
compound.
thickly
coated
with
bitumen
13.
Painting of MS Flats
•
For protection against corrosion, all the
exposed surfaces of earthing connections (MS
flats) above ground level shall be given all
around two coats of painting to colour grass
green, shade-218 of IS:5.
14.
Crushed Rock Surface Layer
•
At the traction substations and switching
stations, a surface layer of crushed rock shall
be provided to a thickness of about 100 mm.
If considered necessary from the point of view
of containing the step and touch voltages
within
the
acceptance
limits,
higher
thicknesses may be provided depending on
calculation based on site conditions.
125
126
LV Side 25KV. & Gantry
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127
Supply From TSS TO OHE
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128





6/29/2022
DOUBLE POLE ISOLATOR
CURRENT TRANSFORMER ( CT )
CIRCUIT BREAKER (CB)
LIGHTING ARRESTER (ACLA)
TRACTION POWER TRANSFORMER
129
132 / 27.5 KV AC TRACTION SUB STATION
HVCB
HVCT
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HV DP ISO
130
HVC.B.
HVL A
Power Transformer
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131
HVC.T.
6/29/2022
132
Metering (3-PHASE-4 WIRE (3 ELEMENT) METER )
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133
HV.DOUBLE POLE ISOLATOR
RDSO SPEC. No : ETI/PSI/122 (3/89)
TYPE :
6/29/2022
Manually operated single or Double break upright
mounting with the moment of blade(s) in a horizontal
plane with or without earthing switch and suitable for
out Door in stallion.
 No of Pole
: Two/ Three
 Nominal system Voltage : 66, 110,1 32, 220 kV
 Highest System Voltage : 72.5, 123, 145, 245 kV
 Rated current
: 1250, 1250, 1250, 1250 A
 Rated short time withstand
Current For one second
: 31.5,31.5,25, 31.5 kA ( rms )
 Isolating Distance in air : 1200,1800,1800,2800mm
134
HV.DOUBLE
POLE
HV.DOUBLE POLE
ISOLATOR
ISOLATOR
RDSO SPEC. No : ETI/PSI/122 (3/89)
6/29/2022
135
HV.CURRENT
TRANSFORMER
( CT )
HV.CURRENT
TRANSFORMER
( CT )
RDSO SPEC. No : ETI/PSI/117 (7/88)
Type : Single phase, oil filled, self cooled , outdoor type
Rated (System) voltage :
Frequency
220,132,110,66 KV
: 50 Hz +- 3%
Rated primary current : 200-100, 400-200, 400-200, 800- 400A
Rated secondary current : 5 A
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136
HV.CURRENT
TRANSFORMER
HV.CURRENT
TRANSFORMER ( CT )
RDSO SPEC. No : ETI/PSI/117 (7/88)
6/29/2022
137
• Current transformer is used to step down the
current of power system to a lower level to make it
feasible to be measured by small rating Ammeter
(i.e. 5A ammeter). A typical connection diagram of
a current transformer is shown in figure below.
BREAKER (CB)
HV.CIRCUIT HV.CIRCUIT
BREAKER (CB)
RDSO SPEC. No : TI/SPC/PSI/CB 0000
Rated (System) voltage : 66,100/110,132, 220 kV.
Rated Normal Current : 1250,1600,1600, 2000A
Rated Short Circuit
breaking Current
: 31.5,40,40,50 KA
Rated breaking Capacity : 2284,4920,5800,12250 MVA
Frequency
: 50 Hz
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139
HV.CIRCUIT BREAKER (CB)
RDSO SPEC. No : TI/SPC/PSI/3CB 0000
6/29/2022
140
HV.LIGHTING
HV.LIGHTING
ARRESTERARRESTER (ACLA)
6/29/2022
141
TRACTION POWER TRANSFORMER
RDSO Spec. No.ETI/PSI/118 (10/93)
Type
:
ONAN cooled single phase , step Down Power
Transformer Double limb wound , Core Type out door
Installation .
Winding : Uniformly insulated concentratric
Frequency : 50 Hz
Rated Primary Voltage
: 66, 110,132, 220 kV
Rated Secondary Voltage : 27kV
Rated Power : 21.6 MVA
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142
TRACTION POWER
TRANSFORMER
RDSO Spec. No.ETI/PSI/118 (10/93)
6/29/2022
143
TRACTION POWER TRANSFORMER
HV BUSHING
BUCHHLOZ RELAY
RADIATOR
TAP CHANGER
MARSHALLING BOX
132/25 KV TRANSFORMER







6/29/2022
DOUBLE POLE ISOLATOR
SINGAL POLE ISOLATOR
CURRENT TRANSFORMER ( CT )
POTENSIAL TRANSFORMER (PT)
CIRCUIT BREAKER (CB)
LIGHTING ARRESTER (ACLA)
AUXILARY TRANSFORMER (AT)
145
42 kV LIGHTING ARRESTER
 System
 Nominal system -
Single phase ac traction
25 kV (phase to earth)Possible
variation in the traction supply
 Voltage
22.5 to 27.5 kV sometime touching 30kV
 Rated frequency - 50 Hz
Type of lighting arrested. - Non-linear metal oxide
resistor type without gap.
 Line
6/29/2022
discharge class - Class 3
Continuous operating voltage capability - 35 kV (rms)
 Max. discharge voltage at At
Nominal discharge current - 125 kVp
 Nominal discharge current (8/20 wave) - 10 k Amps.
 Pressure relief class - class ‘A”
 Power frequency voltage withstand for
arrested insulation. - 105 kV (rms)
146
25 kV
LIGHTING ARRESTER
(ACLA)
25 kV LIGHTING
ARRESTER
(ACLA)
RDSO SPEC. No : ETI/PSI/71(Rev.)I (1/87)
6/29/2022
147
25 kV INTERRUPTER
RDSO SPEC. No.ETI/PSI/159 (10/94)
6/29/2022

System

Nominal system
voltage




Rated frequency
Number of poles
Class
Rated voltage class
: Single phase ac traction
system
: 25 kV variation from 19kV
to 27.5kV – occasionally
touching 30kV
: 50 Hz +/- 3%
: One
: Outdoor
: 52kV
148
Interrupter
OHE
Insulated Overlap
Interrupter Close
The uncharged side of OHE is ON.
Interrupter Open
The charged side of OHE is OFF.
25 kV INTERRUPTER
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150
AUXILARY TRANSFORMER (AT)
RDSO SPECIFICATION No. ETI/PSI/15 (08/03)
Type
: Double wound, single phase, ONAN (oil natural
air natural) cooled, step-down transformer for
out door installation.
Rated voltage of
primary winding :
a) Nominal Voltage 25 kV
b) Minimum Voltage 19 kV
c) Maximum Voltage 27.5 kV
Rated voltage of
secondary winding :
240 V
Rated frequency.
:
50 HZ +/- 3%
Rated power at rated
nominal voltage
: 5,10,25,50KVA
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151
AUXILARY TRANSFORMER
(AT)
RDSO SPECIFICATION No. ETI/PSI/15 (08/03)
6/29/2022
152
25 kv CIRCUIT
BREAKER
(CB)
25 kv CIRCUIT
BREAKER
(CB)
RDSO SPEC. No : TI/SPC/PSI/CB 0000
Rated (System) voltage : 25kV.
Rated Normal Current :1600A
Rated Short Circuit
breaking Current
: 20 KA
Rated breaking Capacity :550 MVA
Frequency
: 50 Hz
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153
25 kv CIRCUIT BREAKER (CB)
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154
25 kV a c Single Pole Isolator (SP)
RDSO Specification No. ETI/OHE/16 (1/94)
Type
:
Number of phases
Number of poles
Isolating distance
Rated voltage
Rated current
Type- I
: One
: One or two (as specified by the purchaser)
: 500 mm (min.) (In air)
: 25 kV (nominal) 30 kV maximum
:
: 1250 A ( Isolator used at Sectioning and
Manually operated, horizontally mounted on
pole, vertical break type and suitable for
outdoor.
paralleling post & Sub-sectioning and
paralleling post).
Type – II
: 1600 A ( Isolator used at Feeding post &
Traction substation)
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Rated frequency
: 50 Hz. +/-3%
155
25 kV a c Single Pole Isolator (SP)
RDSO Specification No. ETI/OHE/16 (1/94)
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156
Dynamic Reactive Power Compensation Equipment (DRPC)
RDSO :TI/SPC/PSI/DRPC/0050
System
:Single phase ac Traction System
Nominal System voltage : 25 kV ( phase to earth)
Variation in the Traction :19 kV- 27.5 kV (up to 30kV at instant
Equipment Voltage class:52 kV
Rated Frequency
: 50 Hz
Average power factor of : Between0.7 and0.8 lagging
the traction system
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157
Dynamic Reactive Power Compensation Equipment (DRPC)
RDSO :TI/SPC/PSI/DRPC/0050
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158
TRANSFORMER
( CT )
CURRENTCURRENT
TRANSFORMER
( CT )
Type
:
CTR
:
Burden
:
Insulation Level :
6/29/2022
OCT – 47 AD/01
1500 / 750 /5
60 VA
35/ 250 kV.
159
25kV CURRENT TRANSFORMER ( CT )
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160
25 kV POTENTIAL TRANSFORMER (PT)
6/29/2022
Type
PTR
Burden
:
:
:
Type
PTR
Burden
:
:
:
I
27.5 kV./ 100v.
30VA
II
27.5 kV./ 110v.
100VA
161
25 kV POTENTIAL TRANSFORMER (PT)
6/29/2022
162
• Potential Transformer (P.T.) is used to step down the
voltage of power system to a lower level to make is
feasible to be measured by small rating voltmeter i.e.
110 – 120 V voltmeter. A typical connection diagram
of a potential Transformer is showing figure below.
Mode of operation
Analog Inputs
Analog-Digital-Conversion
yes
Protection program
Fault detection
no
Routine program
Command and information output
HISTORY OF PROTECTIVE RELAYS
ON IR
UP TO 1984
Electro-Magnetic type Relays
1984 TO 2000
Static / Microprocessor based relays
Since 2001
Numerical type Relays
Protection Scheme at TSS
UP Line
DOWN Line
Feeder Protection
DPR, WPC, Inst. OCR, PTFF & Auto
reclosure relay
Feeder Protection
DPR, WPC, Inst. OCR, PTFF &
Auto reclosure relay
OCR2
IDMT
REF
OCR2
IDMT
REF
DFR
TTr1
DFR
TTr2
OCR1
IDMT + HF
REF
110/100/22kv
Incoming Supply
OCR1
IDMT + HF
REF
110/100/22kv
Incoming Supply
166
Transformer OCR Protection
ORC1
190% of Full Load Current of Transformer
IF=0
110KV
ORC2
180% of Full Load Current of Transformer
R
25KV
I2
I1
IF=0
OHE
167
summary of transformer protection IDMT & definite
time OCR relays setting is as under
Relay element
HV side
LV side
REF
Current setting
in % of
transformer
rated current
10
Time setting
% Current
setting of
transformer
rated current
Instantaneous i.e. 10
20ms
500-600ms as per 180
curve for bus fault
Time setting
Instantaneous i.e.
20ms
250-300ms as per
curve for bus fault
IDMT
190
Stage-1 OCR
120
360 sec
110
300 sec
Stage-2 OCR
150
180 sec
140
120 sec
Stage-3 OCR
180
120 sec
170
60 sec
Post over load
110
5 sec
100
5 sec
168
Comparison of existing & new Panels
Existing TSS C&R Panel using static relays
Width : 1850 mm
Length: 1700 mm
Height : 2300 mm
New developed C&R Panel with numerical relays
Width : 1200 mm
Length: 2200 mm
Height : 2300 mm
Front view
Front view
Reduction in size and weight:

16% reduction in area and volume.

Panel weight is considerably reduced due reduction in
size and reduction in relay module by integration of
protection function.
169
Comparison of existing & new Panels
Existing TSS C&R Panel using static relays
New developed C&R Panel with numerical relays
Lay out of equipments on the panel:
• All protective relays except master trip relay are
provided on front panel which provide simplicity in
accessibility to operator.
• Increase space between panel equipment.
• Panel door provided on rear side.
Rear view
Rear view
170
Comparison of existing & new Panels
Existing shunt cap. C&R Panel using static
relays
Front view
New developed shunt cap C&R Panel with numerical
relays
Front view
171
WE RESPECT OUR VALUES
BUSINESS
ETHICS
TEAM
WORK
CUSTOMER
CENTRICITY
VALUES
PRIDE
RESPECT
QUALITY
Thank You