INTERNSHIP REPORT (FINAL)

INTERNSHIP REPORT
AT ELECTRICAL AND MECHANICAL DEPARTMENT OF
POWER TRANSMISSION AND DISTRIBUTION IC
LARSEN & TOUBRO LIMITED
SUBMITTED BY
B.SINDHUJA
M.G.VISHALI
Electrical and Electronics Engineering
RMD Engineering College
During the period09-06-2014 to 20-06-2014

CONTENTS
 Acknowledgement
 Introduction – BMRCL Project
BMRCL Specifications
 Electrification of metro rail stations
Earthing philosophy
 Assignment- vendor offer review report
 Diesel Generator sizing
Load details and Switchgear sizing
 L.V Feeder cable sizing
 Distribution Transformer sizing
Electrical calculations-Lighting calculations
 Cable schedule

ACKNOWLEDGEMENT
The industrial exposure that we have experienced as trainees in
Industrial Electrification Business Unit of Power transmission and
Distribution Independent Company (PT&D IC) of L&T Construction
has helped us a lot not only in improving our theoretical knowledge but
also to understand the working of a large industry and Practical
engineering.
We are sincerely grateful to the management of PT & D IC and
Mr. D. Maheswaran, GM & Head Engineering (IE&SS)- PT&D IC, for
giving us an opportunity to undergo a ten days Internship program in
their organization.
We would like to express our deepest gratitude towards Mr. Krishnan
C. Menon for associating us in this training. We also express our sincere
gratitude & thanks to Ms. Priyanka Dharamshi and Mrs. R.Sandhiya
for the guidance and encouragement at various stages during our
internship.
Last but not the least; we would like to thank L&T Construction for
providing us this opportunity and exposure to the real Industry.

BANGALORE METRO RAIL PROJECT
What is METRO Rail?
• An urban electric passenger transport system
• High capacity & high frequency of service
• Totally independent from other traffic road or pedestrian
Revolution in traction systems
Electric trains came to existence with DC over headlines of 1.5kV & 3kV DC in late 19th
Century.
Usage of high voltage DC would lead to electrocution and considered unsafe. Hence was
restricted to low speed to overcome the same
AC traction system came to existence in mid 20th century with 15kV system feeding the DC
Series motors through AC-DC rectifiers.
Due to the technical difficulty in rectifier technology 25kV AC Induction motor traction
system came to existence in late 20th century.
There was revolution in DC traction system as it was more appealing for metro due to its
aesthetic aspects. Due to high demand of Metro 750V DC Third rail traction system came to
existence. “Third rail” Terms the rail other than two running rails which feeds power to the
traction motors
Advantages & Disadvantages of 25kV over 750V DC Traction system
• 25kV AC Traction system is safer.
• Used for high speed trains for longer distances
• Cost effective compared to DC third rail
• But causes imbalance in 3-phase supply

Comparisonbetweenvarious metro rails in India
** These projects are executed in different phases and some phases are handed over and are
under commercial operation.
Characteristics of railway electrification
Two forms in which Power is supplied to moving trains:
1. Overhead line or catenary wire suspended from poles or towers along the track or from
structure or tunnel ceilings
2. Third rail mounted at track level and contacted by a sliding "pickup shoe“ usually use
the running rails as the return conductor but some systems use a separate fourth rail for
this purpose.
Third rail : A third rail is a method of providing Electric power to a railway train, through a
semi-continuous rigid conductor placed alongside or between the rails of a railway track.
The conductor rail is supported on ceramic insulators (known as "pots") or insulated brackets,
typically at intervals of around 10 feet (3 metres).
Delhi
Metro
(Line -1, Line
2, Line 3, Line
4, Line 5 &
Line 6)
Kolkata
Metro
(Line -1)
Bangalore
Metro
(Reach-1,
Reach- 2,
Reach – 3 &
Reach -4)
Jaipur
Metro
Chennai
Metro
Hyderabad
Metro
Total
No. of
Stations
142 24 42 11 40 64
Line
Length
189 kms 28kms 42 kms 9.25 kms 42 kms 72 kms
Traction
System
25 kV AC 750 VDC 750 VDC 25 kV AC 25 kV AC 25 kV AC
Type of
Station
Both U/G &
Elevated
Both U/G
& Elevated
Both U/G &
Elevated
Both U/G
&
Elevated
Both U/G
&
Elevated
Elevated
Project
Status
Completed** Completed Completed**
Under
Execution
Under
Execution
Under
Execution

Usually use the running rails act as the return conductor but some systems use a separate fourth
rail for this purpose.
Benefits of Third Rail system:
• Eradicates Electromagnetic interference on electrical components
• Reduces maintenance costs.
• Offers high efficiency - a 750V dc system gives efficiency of 92-94%.
• More Rugged than an overhead contact wire
• Longer life expectancy.
• High reliability because it is fed on both sides by rectifiers from adjacent substations
• Lower comparative initial costs than an AC system.
• Cheaper Rolling stock
• Since no transformers are installed on board– Reduced Weight of the vehicles and
Increased Passenger Capacity
METRO TERMINOLOGIES RELEVANT TO POWER DISTRBUTION
• RSS (Receiving Sub-Station)
• TSS (Traction Sub-Station)
• ASS (Auxiliary Sub-Station)
• Depot
• Viaduct

• Chainage
Key Features ofBMRCL
Owner Bangalore Metro Rail Corporation Limited
Number of lines
2 (Now)
2 (Phase I Target- March 2015)
4 (Phase II Target - December 2019)
Number of stations
16 (Now)
41 (Phase I Target - March 2015)
102 (Phase II Target- December 2019)
Chief executive Pradeep Singh Kharola, MD
Operation
Began operation 20 October 2011 (2011-10-20)
Train length 3 coaches
Headway 10 – 15 minutes
Technical
System length
42.3 km (Phase I)
114.39 km (Phase II)
Track gauge 1,435 mm standard gauge
Electrification 750V DC Third rail
Speed 40 km/h (Average) , 80 km/h (Top)
Other features of BMRCL
• Tunnel air conditioning
• Uses Composite DC Third rail
• Air conditioned coaches
• Automatic Train Protection System
• Derailment protection guards

• Wi-Fi enabled (the first metro in India to have this feature)
• Emergency voice communication
• Powerheart Automated external defibrillator to protect its commuters against death from
sudden cardiac arrest
• Earthquake proof & rainwater harvesting
• The minimum fare is 10 and maximum fare of 15 for Reach-1
Levels of Underground station:
1. Concourse – level below the ground, that has escalators, ,ticket counters, DG rooms etc
2. Platform - level below concourse that has tracks for commutation
3. Undercroft- bottom most level , it consists of cable trays .
L&T’s scope of work
Electrical and Mechanical( E&M) works including Hydraulic, Fire safety systems, UPS, DG Sets
for Seven Underground stations and associated tunnel sections of North-South and East-West
Corridors of Bangalore Metro Rail Project-Phase-1
The seven underground stations under L&T ‘s scope are
1. City Railway,
2. Sir M Vishveshwaraya,
3. VidhanaSoudha,
4. Cubbon Park,
5. Chickpete,
6. KR Market and
7. Kempegowda
I. ELECTRICAL WORKS: -- E&M
Package
• Design, Preparation of Working or
shop drawings
• Provision of :
1. Power & control cables
2. Main, sub main LV switchboards &
rest other distribution boards
3. Interlocks & protection schemes for
power distribution

4. Normal & emergency lighting arrangement
5. Plug & sockets for lighting in tunnel & station areas
6. Earthing system –Main Earth bus in ASS, Clean Earth system & Clean Earth Bus
7. Lightning protection system
• Interface & coordination with BMS contractor for development of suitable control
schemes
• Ascertain power supply feeding arrangements for ECS, TVS, Lifts & Escalators ets
• Supply & Lying of GI conduits with accessories for PA, communication, Signaling
systems.
II. HYDRAULIC WORKS:
• Provision of:
1. Pumping arrangements
2. Automatic control & monitoring of operation of pumps
3. Feeding arrangement of various pumps
4. Pipeline network with control valves, water treatment to suit ECS requirements
III. FIRE FIGHTING & PROTECTION WORKS
1. Complete Fire suppression system in UG stations and associated tunnel sections &
ancillary buildings including hydrants, hose reels, sprinkler system, fire hose cabinets,
portable extinguishers, gas based flooding system etc
2. Fire Detection & Alarm system including monitoring & control through SCADA.
Designated contractors
 General Consultants: RITES-OC-PBI-SYSTRA
 Detail Design consultants: Mott MacDonald
 Civil works: CEC & SOMA
 Traction : ABB
 Telecom: Thales
 Signaling: Alstom
 HVAC: Bluestar
 Tunnel fans: ETA
 Elevators, Lifts, Escalators: Johnson
Other interfaces excluding E&M
 Lifts and escalators
 Railways electrification( DC Traction)

 Auxiliary substation( up to the provision of bus ducts from transformer to LV main
switch board)
 SCADA and UPS
 Track work and Rolling stock
 Signaling and telecommunication
EARTHING PHILOSOPHY
Earthing:
To understand the earthing codes and practices, we have been provided with the Indian Standard
3043 (Code of Practice for Earthing). We understand various earthingphilosophies followed in
industries and are briefly described here.
In electricity supply systems, an earthing system or grounding system is circuitry which connects
parts of the electric circuit with the ground, thus defining the electric potential of the conductors
relative to the Earth's conductive surface. The choice of earthing system can affect
the safety and electromagnetic compatibility of the power supply. In particular, it affects the
magnitude and distribution of short circuit currents through the system, and the effects it creates
on equipment and people in the proximity of the circuit. If a fault within an electrical device
connects a live supply conductor to an exposed conductive surface, anyone touching it while
electrically connected to the earth will complete a circuit back to the earthed supply conductor
and receive an electric shock.
Earthing methods
The choice of these methods governs the measures necessary for protection against indirect-
contact hazards.
The earthing system qualifies three originally independent choices made by the designer of an
electrical distribution system or installation:
 The type of connection of the electrical system (that is generally of the neutral conductor)
and of the exposed parts to earth electrodes.
 A separate protective conductor or protective conductor and neutral conductor being a single
conductor
 The use of earth fault protection of overcurrent protective switchgear which clear only
relatively high fault currents or the use of additional relays able to detect and clear small
insulation fault currents to earth
In practice, these choices have been grouped and standardised as explained below.
Each of these choices provides standardisedearthing systems with three advantages and
drawbacks:
 Connection of the exposed conductive parts of the equipment and of the neutral conductor to
the PE conductor results in equipotentiality and lower overvoltages but increases earth fault
currents

 A separate protective conductor is costly even if it has a small cross-sectional area but it is
much more unlikely to be polluted by voltage drops and harmonics, etc. than a neutral
conductor is. Leakage currents are also avoided in extraneous conductive parts
 Installation of residual current protective relays or insulation monitoring devices are much
more sensitive and permits in many circumstances to clear faults before heavy damage
occurs (motors, fires, electrocution). The protection offered is in addition independent with
respect to changes in an existing installation
Classification OfEarthing BasedOn System Earthing
 TT system (earthed neutral)
 TN systems (exposed conductive parts connected to the neutral)
 IT system (isolated or impedance-earthed neutral)
TT system (earthed neutral)
One point at the supply source is connected directly to earth. All exposed- and extraneous-
conductive-parts are connected to a separate earth electrode at the installation. This electrode
may or may not be electrically independent of the source electrode. The two zones of influence
may overlap without affecting the operation of protective devices.
TN systems (exposedconductive parts connected to the neutral)
The source is earthed as for the TT system (above). In the installation, all exposed- and
extraneous-conductive-parts are connected to the neutral conductor. The several versions of TN
systems are shown below.
TN-C systemThe neutral conductor is also used as a protective conductor and is referred to as a
PEN (Protective Earth and Neutral) conductor. This system is not permitted for conductors of
less than 10 mm2 or for portable equipment.
The TN-C system requires an effective equipotential environment within the installation with
dispersed earth electrodes spaced as regularly as possible since the PEN conductor is both the

neutral conductor and at the same time carries phase unbalance currents as well as 3rd order
harmonic currents (and their multiples).
The PEN conductor must therefore be connected to a number of earth electrodes in the
installation.
Caution: In the TN-C system, the “protective conductor” function has priority over the “neutral
function”. In particular, a PEN conductor must always be connected to the earthing terminal of a
load and a jumper is used to connect this terminal to the neutral terminal.
Fig.: TN-C system
TN-S system
The TN-S system (5 wires) is obligatory for circuits with cross-sectional areas less than 10
mm2 for portable equipment.
The protective conductor and the neutral conductor are separate. On underground cable systems
where lead-sheathed cables exist, the protective conductor is generally the lead sheath. The use
of separate PE and N conductors (5 wires) is obligatory for circuits with cross-sectional areas
less than 10 mm2 for portable equipment.
Fig.: TN-S system
TN-C-S system
The TN-C and TN-S systems can be used in the same installation. In the TN-C-S system, the
TN-C (4 wires) system must never be used downstream of the TN-S (5 wires) system, since any
accidental interruption in the neutral on the upstream part would lead to an interruption in the
protective conductor in the downstream part and therefore a danger.

Fig: TN-C-S system
Fig.: Connection of the PEN conductor in the TN-C system
IT system(isolated or impedance-earthed neutral)
IT system(isolated neutral)
No intentional connection is made between the neutral point of the supply source and earth
Fig: IT system (isolated neutral)
Exposed- and extraneous-conductive-parts of the installation are connected to an earth electrode.
In practice all circuits have a leakage impedance to earth, since no insulation is perfect. In

parallel with this (distributed) resistive leakage path, there is the distributed capacitive current
path, the two paths together constituting the normal leakage impedance to earth .
Fig: IT system (isolated neutral)
In a LV 3-phase 3-wire system, 1 km of cable will have a leakage impedance due to C1, C2, C3
and R1, R2 and R3 equivalent to a neutral earth impedance Zct of 3,000 to 4,000 Ω, without
counting the filtering capacitances of electronic devices.
Fig: Impedance equivalent to leakage impedances in an IT system
IT system(impedance-earthed neutral)
An impedance Zs (in the order of 1,000 to 2,000 Ω) is connected permanently between the
neutral point of the transformer LV winding and earth (see Fig. E11). All exposed- and
extraneous-conductive-parts are connected to an earth electrode. The reasons for this form of
power-source earthing are to fix the potential of a small network with respect to earth (Zs is
small compared to the leakage impedance) and to reduce the level of overvoltages, such as
transmitted surges from the MV windings, static charges, etc. with respect to earth. It has,
however, the effect of slightly increasing the first-fault current level.

Step Potential
Step potential is the step voltage between the feet of a person standing near an energized
grounded object. It is equal to the difference in voltage, given by the voltage distribution curve,
between two points at different distances from the electrode. A person could be at risk of injury
during a fault simply by standing near the grounding point.
Touch Potential
Touch potential is the touch voltage between the energized object and the feet of a person in
contact with the object. It is equal to the difference in voltage between the object and a point
some distance away. The touch potential or touch voltage could be nearly the full voltage across
the grounded object if that object is grounded at a point remote from the place where the person
is in contact with it. For example, a crane that was grounded to the system neutral and that
contacted an energized line would expose any person in contact with the crane or its uninsulated
load line to a touch potential nearly equal to the full fault voltage.

Reducing Step and Touch Potential Hazards
One of the simplest methods of reducing Step and Touch Potential hazards is to wear Electric
Hazard Shoes. When dry, properly rated electric hazard shoes have millions of ohms of
resistance in the soles and are an excellent tool for personnel safety. On the other hand, when
these boots are wet and dirty, current may bypass the soles of the boots in the film of material
that has accumulated on the sides of the boot. A wet leather boot can have a resistance on the
order of 100 ohms. Furthermore, it cannot be assumed that the general public, who may have
access to the outside perimeter of some sites, will wear such protective gear.
Another technique used in mitigating Step and Touch Potential hazards is the addition of more
resistive surface layers. Often a layer of crushed rock is added to a tower or substation to provide
a layer of insulation between personnel and the earth. This layer reduces the amount of current
that can flow through a given person and into the earth. Weed control is another important factor,
as plants become energized during a fault and can conduct hazardous voltages into a person.
Asphalt is an excellent alternative, as it is far more resistive than crushed rock, and weed growth
is not a problem. The addition of resistive surface layers always improves personnel safety
during a GPR event.
Also it is the industrial practice to have underground earthmat which is properly designed to
bring touch and step potential to tolerable limits. There are provided in switchyards, Power
generation stations, Metro rail stations, etc.
BMRCL Equipment Details
I. DG SETS
 It has Diesel engine integrated with alternator, engine mounted radiator, battery, battery
charger and day service tank.
 Piping with fuel handling system, lube oil system, air filters, exhaust piping and
residential silencer.
 Power and Control cabling system
 Contains steel base frame, integral sound proof enclosure (acoustic enclosure) and anti
vibrating mounting pads.
 Satisfies the requirements of NFPA110.
Rating
 750 & 1010 kVA, 415V DG Sets.
 Power Factor-0.9 lagging (average) but at rated condition, load power factor is 0.8
lagging or better.
 Operating mode –Used only for standby purposes supplying the rated loads for 8 hours
with the rest period not less than 30 minutes.

 Overload capacity-Reserve capacity-10% for one hour in twelve hours.
 Ambient conditions-Maximum temperature 45º,Maximum Humidity-75%RH
attitude:1000m(Above mean sea level)
 Service Interval-running full load-less than 300 hours without maintenance adjustments
and for 10,000 hours between major overhauls.
 Shaft Speed-Not more than 1500 rev/min
 Motor Starting-Largest motor set is require to start-18KW-Star-Delta starter
 Loads-Operating in conjunction with non-linear and harmonics generating electronic
loads in UPS Systems.
Cold Conditions
 Start automatically-full rated loads (30sec) on failure of supply.
 Jacketed water heating facility before starting pre-lubrication array.
Housing
 Sound proof enclosure reduces the noise level of 75 dB at one meter distance from DG
set enclosure.
Diesel Engine
 Four stroke, multi cylinder –dynamically balanced with electronic fuel injection systems,
turbo charged and intercooled suitable for heavy duty emergency operations.
 Critical speed-Crankshaft-15% rated speed.
 Engine-10% over load for one hour in 12 hour running period.
 Engine fitted with heavy dynamically balanced flywheel for constant speed generator-
BS649 requirements.
 Engine Speed maintained-BS 5514
 DG set parallel to another DG set-installation of an auto synchronizing panel suitable for
PCC operation.
 DG set provides continuous operation at ambient temperature for 8 hours.
Basic Engine
 Connecting rod-heavy duty-forged special steel for handling power tariff.
 Pistons are provided with piston rings and forced lubrication is employed to avoid any
hotspot development.
 Cylinder-lubrication-inner side with close tolerance-efficient output.

Air Intake System
 Intake-air-force from engine room.
 Ventilation system-DG sound proof enclosure.
 Twin heavy duty air intake-BS72266
Turbo Charger
 Driven by exhaust gas from cylinder.
Intercooled System
 Compressed air-turbo charger-after cooled air heat exchange.
 Enhance engine performance level and pre mature requirements of maintenance.
Exhaust System
 High noise reduction muffler-correct position-exhaust pipeline.
 Two silencers in series, one is located inside and other one is fitted on the roof of the
generator building.
 Minimum wall thickness of pipes and silencers-3mm.
 Installation thickness-checked in tender-Max temperature is 50ºC on outside of pipe and
supporting should be provided o withstand back pressure.
 Silencer reduces sound level of 25dB by one meter form DG set.
Engine Cooling System
 Engine cooled-water jacket-heavy duty air blast radiator.
 Separate oil cooling is provided by cooling engine oil.
Lubricating System
 Engine lubrication-closed circuit-wet sump, forced feed system
 Forced lubrication uses lubrication filter with a minimum time period of 300 hours or
more.
 Lubricating oil pressure is monitored and on any fall below the recommended value,
alarm is used and engine is safely shut down.
Fuel System
 High speed diesel oil-IS 1460.
 2 stage fuel filtration. The Fuel system-engine speed governor of electronic type.

Governor
 Governor control- isochronous type –constant speed of engine at different load-maximum
rating of machine.
 Requirements
 Steady state speed - + 1% of nominal speed.
 Transient frequency change on application-rejection of 60% of load.
 Max speed drop : 8%
 Performance of governor under all load conditions – class A in BS5514:part
4(ISO 3040)
Starting System and Battery Charging
 Starting system compromise-24V heavy duty sealed maintenance free, has lead acid
battery and electric starting motor.
 Provision to start engine from remote locations-from control panel or control room.
 Automatic change over-battery charging-engine driven alternator at all times-generator
set is running.
 Automatic changer with automatic selection unit.
Alternator
 Four pole, three phase, salient pole, self excited, revolving field, brushless type, self
regulating and manufactured –IEC 60034.
 Screen protected, fan ventilated, Neutral dip proof-IP23.
 Capable of maintaining short circuit I, three times full load for a period of 3 seconds.
 Alternator winding-insulation-Class H.
 Transient performance-Clause 13.18.7.
 Three neutral sides CT for differential protection.
 Test temperature rise test of winding-100% of rated current.
Mounting and Package Generator
 Fully painted anti corrosive plate.
 Noise level restricted to 70dB at 1m from canopy.
 Anti vibrationmounting is spring type between bedplate and floor prevents the vibration
from being transmitted.

Metering
 Parameter monitoring
 Electrical-system DC voltages, AC voltages, AC current, frequency, real power,
reactive power, power factor.
 Engine-Lubricating oil pressure, exhaust temperature, RPM
Protections
 Alarms.
 Over speed, alternator winding temperature, start failed alarm, low oil pressure.
 Engine protection/shut off parameters.
 Over speed, low oil pressure, over ranking.
 Electrical protection.
 Loss of excitation, over and under frequency, over current, over and under voltages.
OPERATIONS
 Manual start/stop-generator set.
 Local and remote selection for the operation of generator set.
 Engine speed/voltage control.
 Fuel transfer control.
Provisions for PLC I/Ps &O/Ps
 DG Battery voltage
 DG Output voltage
Generator Control Unit
 Manual start/stop of generators from LPGCP
 Metering & alarm
 Auto start/stop of generator for generator switch gears
 Performance data transmission
 Load management/load based auto start/stop/paralleling
 Protection of generator sets

 Active and reactive load sharing for generator sets
 Automatic paralleling /Synchronizing of generator sets
Control Unit: - Electrical and System Protection
Features
 Over current, earth fault and under voltage
 Under frequency, reverse power and standby earth fault
 Differential, alternator bearing/winding temperature high
Protection Of Operations
 High water/oil temperature, low lubrication oil and high pressure.
 High and low speed, alternator over pressure.
Fuel Tanks
 Integral fuel day tank-capacity to run for 8 hours.
 Tank constructed with mild steel BS 2594.
Fuel Filters
 Supply line fuel filter-BS 4552
Fuel Pipe Work and Valves
 Not limited to service filling pipe.
 Bulk fuel tank to service tank pipes
 Service tank vent pipe.
 Generate fuel supply and return pipes.
Fire Protection
 Multi sensor detectors
 Ventilator in generator building.

II. LIGHTING
 Operate at power factor not less than 0.95 lagging.
 Conduit terminations with aluminum fittings and special accessories to prevent corrosion
action.
 All wiring within light fitting –heat resisting low smoke, zero halogen wires for normal
luminaries and fire survival wires for emergency luminaries.
 All light fittings-BS 4533
 Specification for general requirements and tests-BS 4533
 Photometric data for luminaries-BS 5225
 Requirements for electrical installations, IEE wiring regulations 17th edition-BS 7671.
Fluorescent Luminaries
 Supplied with HF, electronic ballasts.
 Diffuses light subjected polycarbonate/glass, injection moulded, glass-not combustion-
self extinguishing.
 High intensity discharge luminaries
 Installation of interior luminaries.
 After installation remove dirt and debris from enclosures
 Clean photometric control surfaces
Exterior Luminaries
 Poles shall be set in the ground to a depth of 1030 m or one fifth of length.
 Pole internal copper conductor, PVC installed IS 694.
 Control gear-galvanized steel case mounted on or inside pole.
Emergency Lighting
 Emergency lighting installation-NFPA 101 and NEPA 130, BS 5266,BS 4553,part 101
and part 102.22.
Emergency Luminaries
 Clearly marked with labels visible to persons standing on floor beneath them.

Lamp Parameters
 Linear fluorescent lamp
 Metal ballide
 High pressure sodium
 Compact fluorescent
 LED
Light Emitting Diode (Led) BasedFitting
 LED based luminaries, in addition to LED module, provision for heat transfer-control
gear, optical conditioning, mechanical support and protection as well as aesthetic switch
elements.
III. SWITCHGEARS
Standards
 BS 1432, specification for copper for electrical purposes: high conductivity
copper rectangular conductors with rolled edges.
 IEC 60439-1/EN 60439-1: Specifications for low voltage switch gear.
Switch Boards
 Low Voltage Main Switch Boards(LVBs)
 IEC 60255/EN 60255:Electrical protection relays
 BS 381 C/BS 4800: Colours for identification, coding and special purposes.
 BS 921 :Rubber mats
 BS 1432: Copper for electrical purposes.
 BS 7211-Thermosetting insulating cable
 BS 5685 –Electricity meters
General Requirements
 Totally Type Tested Assemblies (TTTA).
 All type tests-IEC 60439-1 or EN 60439-1
 LV main switch boards-fault containment tests-IEC 11641
 Protecting earthing configuration TN-S

 Service life-30years
 Separate current transformer for each device.
Quality Control
 Work man ship
 All suitable items of LVSBs-completely interchangeable.
 Tropicalisation
 Encloses required degree of protection,`
 Current transformer winding are epoxy resin capsulated against
ingress of mixture.
LVSB Construction
 LVSB is constructed by using 2mm CRCA thick sheet steel.
 LVSB front and back access has maximum height of 2.3m
 Degree of IP for LVSB –IP54.
 Equipment is arranged within each component
 It requires normal maintenance
 SB-Rated sort time with stand current of 65KA for 1 second.
 BS 951 & BS7430- the component parts of SB.
Busbars
 Bus bars and bus connections – not exceed 90ºC.
 Short time withstand current rating is 65KA for 1sec at 415V
 Bus bar and bus bar connections-IEC 60439-1 or EN 60439-1
 Separate insulating covers-BS EN 60216,IEC 60085 &IEC 60216-1
Polarity
 2 pole, phase pole and neutral pole reacting top to bottom/left to right.
 3 Pole, Red, Yellow, Blue And Neutral/Phase.

Internal and Control Wiring
 All internal and control wiring-low smoke halogen(LSZH)-BS 7211
 Control wiring-single core with min of 1.5mm2.
 Bus wires are fully insulated.
 Control Wires Are Protected By Msb.
Instrumentation
 Instruments-similar in appearance throughout LVSB
 Direct reading electrical meters -1S 13779/IEC 1036,687,1286
 Meter is in continuous operation - 0ºC and 50ºC
 Meters operation with CT/PT-RS 485/RS 232.
Relays
 All control, interlock and alarm relays –EN60255 or IEC60255.
 The relays are microprocessor based with auxiliary contacts – RS232/485.
 The relays are provided with dust proof cases and flush mounting.
 The relays are not affected by mechanical shock or vibration or by external magnetic
fields.
Operating Coils
 The fine wire operating coils with wire wound resistors are vacuum impregnated with
insulating varnish.
Air Circuit Breakers (ACB)
 All ACBs are from IEC-609472 or EN-60947-2
 Frequency-50hz
 Ambient temperature-45 ºC.
 All ACBs are withdrawable type.
 ACB mechanically robust construction.
 Overload and short circuit characteristics are front adjustable.

Safety Shutters
 Shutters cover each 3 phase group of stationary isolating restarts.
Transformer Incomers
 Four pole horizontal draw out automatic ACB with normal current rating are present.
 Two way tripping relays are provided.
 Circuit breakers close/trip control switch is of piston grid type.
 Control relay and wiring for automatic changeover interlocking/voltage sensing relay for
automatic changeover are present.
Moulded Case Circuit Breakers (MCCB)
 MCCB comply with and be type tested-IEC 60947-2 or EN 60947-2.
 Each MCCB are fixed or withdrawable type.
 The trip units are easily replaceable in same MCCB without changing MCCB.
 All MCCBs arrange padlocking in OFF positions with locks provided.
 The degree of protection is IP3X to IEC 60529 or EN 60529.
 They have an electrical endurance of 1000 operating cycles.
 The MCCB in low voltage main switch board store energy motorized and suitable for
remote closing by BMS.
Contractors
 They comply with IEC 60947-4-1 or EN 60947-4-1.
 They are electro magnetically controlled, double air-break type. they are silver or silver
faced.
 They are modular in design and mechanically interlocked.
 The making and braking capacity of contractors IEC 947-4
 They are capable of being integrated into automated system without interposing
components in minimum operating condition.

IV. UNINTERRUPTIBLE POWER SUPPLY (UPS)
 UPS maintain continuous AC power supply to loads-emergency category loads.
 Noise from UPS during operation should not exceed 55 dB at a distance from enclosure,
over load range of 10% to 100% of rated full load ISO 3756/BS 4196:Part 6.
 The design life is about 20 years.
 They are modular in construction to facilitate unit replacement and all electronic cards
shall permit plug in type replacement.
 They are dust and vermiform proof with IP-33 to IEC 60529.
 The UPS are provided with RS 232 & 485 for remote monitoring to extend alarm and
status indications, communications and metering to BMS system located in station
control room.
 The system has operating efficiency, front access and self diagnosing features.
 The heat producing devices are mounted on ample heat sinks.
 The UPS as a whole are mounted on heavy duty fabricated steel base frame.
 The UPS has low impedance with less than 50V, touch voltage and ripple content.
 The UPS output voltage is in synchronization with main supply voltage feeding the static
bypass switch.
 The UPS are equipped with interlocking system to prevent parallel operation.
 The UPS are capable of supplying non linear types of loads.
 The UPS interface for remote monitoring of status and alarms.
 The surge protective devices are used for protection.
Modes
 Normal mode (mains up)
 Stored energy mode (mains down)
 Battery recharge(mains restored)
 Automatic bypass mode (static bypass switch)
 Built in/manual bypass (maintenance)
The UPS on taking unbalanced load shall be provided with H class insulation.

ELECTRIFICATION OF METRO RAIL STATION
Schematic layout diagram
The SLD is the single line schematic layout that gives the plan and layout of every equipment
electrification, its cable layout, earthing layout etc.
The SLD for the city railway station was studied.
The Schematic layout diagram includes the following.
 General schematics
 Panel wise schematic- with distribution boards
 Circuit Breaker Interlocking
 Lighting layout for concourse, platform and undercroft
 Ancillary building layout
 Chiller pump room – basement
 Refuse,toilet, mess ,DG room – ground floor
 Power socket layout
 Cable tray layout
 Lighting layout
 Protection layout
 Earth strip layout
 Main earth distribution
 Clean earth distribution
 Main earth mat location
 Clean earth pit location
 Earth details
There are two substations ASS I and ASS II that powers the main distribution board. Diesel
generators are used as backup during power failure. UPS system is used for powering up the
emergency loads.The various Distribution boards used are
DB 100 , DB 200 ------- main supply
DB 110, DB 210 -------- small power
DB 120, DB 220 -------- lighting
DB 150, DB 250 -------- Bclassified loads (Essential loads)
DB 151, DB 251 --------- escalator
DB 180, DB 280 --------- UPS
DB 130, DB 230 --------- Air handling unit
DB 140, DB 240 --------- Ventilation loads
DB 290, DB 390 --------- DG set

Classification of supply
All power supply equipment will have feeds from two auxiliary substations (ASS) so that failure
of any ASS or single component will not result in a supply disconnection. Certain loads will
have back up supply from the diesel generator and/or from the UPS.
‘A’ Classification (Emergency)
Derived from the station UPS, with 30 minutes standby. The station UPS is provided with dual
incoming supplies from ASS and backed up from the diesel generator set with auto changeover.
The devices under this class are
 Station And Tunnel Emergency Lights
 Fire Alarm Panel Supply
 Control Circuits
 Station Control Room
 Signage Points All Over Station
 SCADA System
 Signaling And Telecom Equipments
‘B’ Classification (Essential)
Supply from both sub stations (with automatic changeover at substation level) and backed up
with diesel generator set. The devices under this class are
 ECS And TVS Equipments
 Fire Fighting Pumps
 Seepage Pumps
 Lifts
 Automatic Fare Collection
 Escalators
 Sewage Pumps
 Cross Passage Pumps
 Ramp Sump Pumps
‘C’ Classification (Semi Essential)
Supply from substation with automatic changeover at substation level. No generator
back-up is provided. The devices under this class are
 Chiller Plant Room Equipments
 AHU’s And Associated Filters
 Water Treatment Pumps
‘D1’ Classification (Normal)
Dual supply from both sub stations at distribution board level (no generator back-up),
manual changeover is provided in the event of failure of any substation. Manual
transfer switches are provided. The devices under this class are

 Normal Lighting
 Small Power Sockets
 Advertisement Points
 Storm Water Pumps
Supply from any one substation only, no generator back-up and no manual changeover. The
devices under this class are
GSM/CDMA Room
Cables used in metro electrification:
The type of cable used for normal supply is generally XLPE with NO SMOKE & ZERO
HALOGEN characteristics. Fire resistant cables are used for UPS supplies and they power up the
emergency loads .
Fire resistant and fire retardant cable sheaths are design to resist combustion and limit the
propagation of flames. Low smokes cables have a sheath designed to limit the amount of smoke
and toxic halogen gases given off during fire situations.
Flame Retardant - designed for use in fire situations where the spread of flames along a cable
route needs to be retarded
Fire Resistant (FR) - cables are designed to maintain circuit integrity of those vital emergency
services during the fire
Low Smoke and Fume (LSF) - burns with very little smoke and fumes compared to standard
PVC, fumes may contain halogens
Low Smoke Zero Halogen (LSZH) - when burns there is very little smoke and fumes (compared
to standard PVC the fumes contain no halogens
Alternative names for LSZH - LSZO (Low Smoke Zero Halogen), 0HLS (Zero Halogen Low
Smoke), LSHF (Low Smoke Halogen Free)
Fire Survival (FS) cables - Fire survival cables are used to maintain circuit integrity for
designated period of time (3 hrs. in general) under fire. Same is used for all emergency feeders in
a Metro station.

A comparison of common insulating materials is as follows:
Material Advantages Disadvantages
PVC
 Cheap
 Durable
 Widely available
 Highest dielectric losses
 Melts at high temperatures
 Contains halogens
 Not suitable for MV / HV cables
PE
 Lowest dielectric losses
 High initial dielectric
strength
 Highly sensitive to water treeing
 Material breaks down at high temperatures
XLPE
 Low dielectric losses
 Improved material
properties at high
temperatures
 Does not melt but thermal
expansion occurs
 Medium sensitivity to water treeing (although
some XLPE polymers are water-tree resistant)
EPR
 Increased flexibility
 Reduced thermal
expansion (relative to
XLPE)
 Low sensitivity to water
treeing
 Medium-High dielectric losses
 Requires inorganic filler / additive
Paper /
Oil
 Low-Medium dielectric
losses
 Not harmed by DC testing
 Known history of
reliability
 High weight
 High cost
 Requires hydraulic pressure / pumps for
insulating fluid
 Difficult to repair
 Degrades with moisture

VENDOR OFFER REVIEW REPORT
S.no SPECIFICATIONS
Powerica - DG
750 KVA
REMARKS
Generator Control Unit
1. Auto/manual selection Manual push botton In Compliance
2.
Separate selection facility
(key operated)
- Details required
3.
Auto mode – controlled by SG
room
Remote control In compliance
4.
Manual mode-lockable selector
switch
- Details required
5. Starting with cranking cranking 3 attempts In compliance
6. Fail to start alarm Overcrank shutdown In compliance
7. Stopping when CB is open Alarm provided In compliance
8. Cooldown time cycle
(0 – 300 ms) prior to
starting
(0-600 ms) prior to
stopping
In compliance
9. Isochronous paralleling Available in PCU In compliance
10.
Auto control of V,F, phase angle
and sequence
within ±1.0% for any
load between no load
and full load
In compliance

Metering
1, Digital type display
320*240 pixels LEd
with LCD backlight In Compliance
2,
Electrical parameter mounting for
 System DC voltage
 Ac voltage
 AC current
 Frequency
 KW
 KVAR
 PF
Digital genset
metering system
In Compliance
11.
Paralleling based on
microprocessor
Sensor based In compliance
12. Load sharing and management
Integrated load
sharing control
system
In compliance
13.
Protection against over voltage,
earth fault, under voltage, over
current, under and differential
frequency
AmpSentry protective
relay
In compliance
14. Protection against reverse power - Details required
15.
Protection against high winding
temperature
- Details required

3,
Engine monitoring for
 RPM
 Oil pressure
 Running hours
 Service hours
 No of starts
SAE-J1939CAN
Engine controller
In Compliance
4,
 Jacket water temperature
Not specified Not applicable in India
5,
 Exhaust temperature
- Details required
Protection
6,
Alarm
 Start failure
Overcrank shutdown
with warning
In Compliance
7,
Winding temperature shut down
alarm
- Details required
8, Over speed alarm Data available Details required
9,
Service tank level( high & low)
alarm
- Details required
10,
Low oil pressure
High coolant temperature
Data available Details required
11,
Electrical Protection
 Over current
 Under voltage
 Over voltage
 Under and over frequency
 Reverse power
 Loss of excitation
 Breaker failure to close
present With shut
down mechanism
In compliance

12, Single phase protection - Details required
Operation
13, Remote selection of operation In PCC not in GCU In compliance
14, Engine speed control Within +/- 0.25% In compliance
15, Alt. voltage control Within +/- 1.0% In compliance
16, No load and manual test facility
Clock interfaced test
facility
In Compliance
17,
Volt free contacts for remote
signaling of alarm
- Details required
18,
Signal isolators for remote
signaling
- Details required
19, Anti condensation heater control -
Not required for
Indian climate. Details
required
20, Fuel transfer pump control -
Level is sensed, no
control, Details
required

GENERAL REQUIREMENT
16. Steel base frame ISMC-300 In Compliance
17. Integral sound proofenclosure
Composite type,
75 db at 1m length
In Compliance
18. Power factor
Avg 0.8
0.9 at rated load
In Compliance
19.
Continuous operation for 8 hours,
with rest not more than 30 mins
Not specified Details required
20. Ambient conditions Temp 40 deg C
No mention about
humidity
21. Service interval Not specified Details required
22. RPM 1500 RPM In Compliance
23. Wake up time 30 seconds Not specified Details required
24. Pre lubrication arrangement Not specified Details required

Engine Details
25. Strokes 4 In Compliance
26. Multi cylinder 12 In Compliance
27. Turbo charged Not specified Details required
28.
Critical crank shaft speed within
15% of rated
150
10% of rated
In Compliance
29.
Sustain 10% overload in 12 hour
running
30. lubricating oil filters
4 paper element filters
of 30 microns size
In Compliance
31. air cleaner
2 air cleaners with
filtering capacity of 15
microns with an
efficiency of 99.7%
In Compliance

32. starter
2 starters of 24 volts
,9 KW
In Compliance
33. battery charger
Battery charging
alternator of 35 amps
with 2.33/3500 drive
ratio
In Compliance
34. Flywheel
SAC 14 ( dimensions
= 589,89,142 mm)
In Compliance
35. Bearings
Replaceable Ball
bearings
In Compliance
36. Air filter type Paper element In Compliance
37. Twin heavy duty air intake filters Not specified Details required
38. Silencer
 2 silencer of
562 mm dia.
 Muffler, 3mm
thick
 Details required
about material
used, (
galvanized steel
is required)
 about dBA at 1
m length
 about insulation
and thickness

39. Radiator
Air blast
Oil cooled
In Compliance
40. Lubricating system Min. life 300 hrs. In Compliance
41. Fuel system P/T type
Details required about
2 stage fuel filtration
42.
Governor
 Isochronous
type
 Steady state
band of +/-
0.25%
 Class A1
about frequency
change on load
rejection.
43. Starting system
 Maintainable
 Battery
charging with
24V lead acid
battery
 Automatic
changeover
 With stop push
button
about starting
time off engine
from the receipt
of command
 No mention
about trickle
boostfacility

ALETERNATOR
44. General requirement
4 POLE, 3 PHASE,
750 KVA
Stamford make
45.
Short circuit current bearing must
be thrice of full load current in 3
seconds
46. Voltage regulation +/- 0.5% In Compliance
47. Ingress protection IP-23 In Compliance
48. Insulation Class H In Compliance
49.
Transmission voltage deviation
folowin step load of, must be
55% is +/- 8% and 60% is +/-
10%
-
Details required
50.
Mounting and packaging
 With steel base
plate and anti
corrosive paint
 In Compliance
No mention
about anti
vibration
mounting
51. Fuel tank
 Integral fuel
tank -8 hours ,
990 lit
 Drain at lowest
point ,inlet at
top
Direct level indicator
In Compliance
52. Fuel filter
 Element type
 In Compliance
 No mention
about firesensor

Diesel Generator Sizing
A 415V, 3phase 50Hz, Diesel Generator sets are been provided at each underground Metro
stations for the back-up electrical power supply to essential and emergency services in the event
of failure of regular electrical power supply. There are three modes of operation:
 Normal mode - TVF is off
 Congested mode - TVF is on
 Fire mode - TVF running in reverse ,up going escalators on
Normal mode is when the train is freely travelling between the stations, the tunnel ventilation
fans are off during normal mode.
Congested mode of operation is when there is no fire in the station but the train is struck in the
tunnel area between two stations and the tunnel ventilation fans and the tunnel booster fans are
required to work due to sudden congestion of the tunnel area.
During the fire mode, both the tunnel ventilation fans and the fire fighting pumps are on. The
tunnel ventilation fans are operated in reverse mode to extract the smoke during fire.
Among the three modes of operation the maximum demand load on the station is during
congested operation mode, hence the same is considered to arrive at the DG rating.
Steps for calculating the DG size:
Step 1: Decide the maximum load. It is known from the modes that the congested mode will have the
maximum load as the tunnel fans will have to work.
Step 2: Estimate the engine size in KW. The factors to be considered here is the specification
given by the client and the cost.
Step 3: Estimate the alternator size in KVA.
Step 4: Check the criteria for the Transient voltage dip (TVD).
TVD < 15 % at the starting of the Tunnel ventilation fan motor.
TVD =
𝑋 𝑑
′
𝑋 𝑑
′
+𝐶
𝑋 𝑑
′
= Transmissionreactance of the alternator (given)
C = rated KVA (to be calculated) =
𝑇𝑜𝑡𝑎 𝑙 𝑟𝑎𝑡𝑖𝑛𝑔 𝑜𝑓 2 𝐷𝐺 𝑖𝑛 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙
𝑆𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝐾𝑉𝐴 𝑙𝑜𝑎𝑑 𝑤𝑒𝑛 𝑇𝑉𝐹 𝑖𝑠 𝑠𝑡𝑎𝑟𝑡𝑒𝑑
Starting KVA when TVF is started = (starting KVA of 180 KW motor) + (base
KVA load when motor is started)
Base KVA = Max. load KVA – motor load in KVA (0.86 pf TVF motor)

Step 5:
Downstream load calculation.
The downstream load distribution is calculated and tabulated in the below format.
The individual board load for every distribution board is considered.
Later the loads have been summarized at main board level as shown below.
Distributio
n board
start
Board
load
Loads
connecte
d
In KW
Workin
g status
Suppl
y class
Power
factor
Load
frequenc
y
Diversit
y factor
MD
factor
Total
connecte
d load in
KW
Full load
current in
amps
KVAR
Total
connecte
d load in
KVA
Switch
board
Load
dissipation
Connected load in
KW
Total CL
KW
Connected load in
KVA
Total CL
KVA
Overall
DF
Total
MD in
KW
Total MD
KVA
remarks
ASS I ASS II ASS I ASS II

 The distribution board column indicates the various DB’s like DB 100, DB 200 etc, and their respective individual loads are
considered.
 Status basically specifies the mode.
S = standby
W = working
 Supply class gives the classification of the supply
‘A’ Classification (Emergency)
‘B’ Classification (Essential)
‘C’ Classification (Semi Essential)
 Power factor points to that of the systems.
 Total connected load refers to every load that is powered by the system.
 Load Factor =
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑚𝑎𝑛𝑑 𝑜𝑣𝑒𝑟 𝑎 𝑝𝑒𝑟𝑖𝑜𝑑
𝑃𝑒𝑎𝑘 𝑙𝑜𝑎𝑑 𝑖𝑛 𝑡ℎ𝑎𝑡 𝑝𝑒𝑟𝑖𝑜𝑑
 Diversity Factor =
𝐼𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎 𝑙 𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑚𝑎𝑛𝑑𝑠 𝑜𝑓 𝑣𝑎𝑟𝑖𝑜𝑢𝑠 𝑠𝑢𝑏 𝑑𝑖𝑣𝑖𝑠𝑖𝑜𝑛𝑠 𝑜𝑓 𝑎 𝑠𝑦𝑠𝑡𝑒𝑚
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑚𝑎𝑛𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑤ℎ𝑜𝑙𝑒 𝑠𝑦𝑠𝑡𝑒𝑚
Diversity factor on working mode will be 1 and on standby mode will be 0.
 Maximum demand Factor =
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑑𝑒𝑚𝑎𝑛𝑑
𝐶𝑜𝑛𝑛𝑒𝑐𝑡𝑒𝑑 𝑙𝑜𝑎𝑑

LOAD DETAILS AND SWITCHGEAR SIZING
Basis of Calculations-
1. Lighting and small power loads are considered as per the actual loads based on the layout drawings and distribution board
details.
2. Equipment data (i.e.) the preliminary data for ECS and TVS system are provided by the GC.
3. Advertisement and Commercial loads are to be received from the designer. These loads are usually assumed.
4. The references are taken from National Building Code of India, Outline Design criteria (ODC).
Load calculations-
1. The sizing of LT panels is done in terms of switchgear rating and number of feeders.
2. Feeder quantity and sizing is based on grouping of loads according to classification of supply.
The downstream calculations and the upstream calculations are done for ASS I and ASS II under the following conditions:
 Load details for ASS I:
 When both ASS I and ASS II are working, feeding their respective loads.
 Load details for ASS II
 When both ASS I and ASS II are working, feeding their respective loads.
The load details are calculated panel wise when
 ASS I is working ,ASS II is failed
 ASS II is working , ASS I is failed

Downstream load tabulations
Later the loads have been summarized at main board level as shown below.
DB Name Power factor CL load in KW CL load in KVA
CL load in
KVAR
Full load current
in amps
Distribution
board start
Board
load
Loads
connecte
d
In KW
Workin
g status
Supply
class
Power
factor
Load
frequency
Diversity
factor
MD
factor
Total
connected
load in
KW
Full load
current in
amps
KVAR
Total
connected
load in
KVA

Fault Level calculations of switchgear
When a short circuit occurs in an electric system, heavy current flows through all the sections of the system which are in the
path between the power source and the equipment. The short circuit current is limited only by the impedance of the system.
This heavy current can damage the components of the electric system if they are not properly rated. If circuit breakers are not able to
interrupt the high short circuit currents in a system, arcing and explosions may occur
The Rating of the components is done based on the maximum short circuit current.The short circuit current is calculated from the
fault level KVA of the System. The Fault Level in a distribution system is a very important parameter. The kVA at the instant of a
Fault should be correctly calculated and the components of the distribution system such as bus bars, circuit breakers, isolators, etc
should be properly sized
Short Circuit Current (kA) for switchgear will be selected based on the 3 phase fault level (kA) of the board. Which can be arrived
based on short circuit analysis of the system.
Tabulation for the same is as follows.
Distri
bution
board
start
Boar
d
load
Loads
connect
ed
In KW
Worki
ng
status
Supp
ly
class
Pow
er
fact
or
Loa
d
freq
.
HZ
DF
MD
fact
or
Total
connect
ed load
in
KW
Full
load
curre
nt in
amps
KVA
R
Total
connect
ed load
in KVA
design
current
Appr,
Break
er
rating
3 ph
Fault
level
KA

LV Feeder cable sizing
Reference standards
IS 5819-(1970) recommended Short circuit rating of high voltage PVC cables
Assumptions
 Voltage drop due to source during the steady state-compensated by OLTC power
transformer and 100% voltage is maintained at source.
Designinputs
Load details
 Load dissipation
 Voltage drop at above source during steady state (%)
System Inputs
 System voltage (v)
 Frequency (f)
 Short circuit current withstand capacity at switchboard (𝐼𝑓)
 Duration of fault withstand capacity (t)
 Apparent power of load (s)
 Load power factor (cos φ)
 Length of the cable (L)
 Efficiency (η)
 Maximum allowable steady state voltage drop at load terminals (𝑉𝑑𝑎)
 Source reactance (𝑋𝑠)
Environmental details
 Ambient temperature (T)
Cable data
 Voltage grade (𝑉𝑐)
 Number of cores
 Cross sectional area (A)
 Conductor material (copper/aluminum)
 Insulation
 Current carrying capacity
 𝐼𝑐air
 𝐼𝑐gnd
 Resistance of the conductor (𝑅 𝑐)
 Reactance of the conductor (𝑋𝑠)
 Short circuit current withstanding capacity of conductor (𝐼𝑠𝑐)
 Number of runs selected (n)

Checking thermal ampacity
Calculation of derating factor for laying in ground
Derating factor for variation in ground temperature = G1
Derating factor for thermal resistivity of soil = G2
Derating of depth of laying = G3
Touching or spacing or trefoil spacing = G4
Overall derating factor = K-Gnd = G1*G2*G3*G4
Calculations of Derating factor for laying in air
Derating factor for air temperature = A1
Derating factor grouping = A2
Overall derating factor = K-Air = A1*A2
Calculations
The derated current carrying capacity of cable in air
𝐼𝐶𝐷𝑅𝐴 =𝐼𝑐 𝐴𝑖𝑟 ∗ 𝐾 − 𝐴𝑖𝑟 (A)
The derated current carrying capacity of cable in ground
𝐼𝐶𝐷𝑅𝐺 = 𝐼𝐶 𝐺𝑛𝑑 ∗ 𝐾 − 𝐺𝑛𝑑 (A)
Derating capacity of the cable selected
𝐼𝐶𝐷𝑅𝐴 ∗ 𝑅𝑢𝑛𝑠
The current carrying capacity required for full load current
𝐼𝐿 =
𝑆
√3.𝑉
Checking short circuit withstand capability
Short circuit withstand capability of selected size of cable =
𝐼𝑆𝐶 ∗𝑛
√ 𝑡
Resistance of cable for length selected R=
𝑅 𝐶∗𝐿
1000 ∗𝑛
Reactance for length of the cable X=
𝑋 𝐶∗𝐿
1000 ∗𝑛
3 phase fault current at load terminal =
𝑉
√3(𝑅+𝑗(𝑋+𝑋 𝑆 )

Checking for steady state voltage drop
From phasor diagram,
𝑉𝑃ℎ= 𝑉𝐿 + 𝐼𝑅𝑐𝑜𝑠𝑄 + 𝐼𝑋𝑐𝑜𝑠(90 − 𝑄)
Steady state voltage drop 𝑉𝑑 = 𝐼( 𝑅𝑐𝑜𝑠𝑄 + 𝑋𝑠𝑖𝑛𝑄)
% 𝑉𝑑 for this length =
𝑉 𝑑∗100 ∗√3
1000∗𝑉
Total voltage drop = % 𝑉𝑑 + 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑑𝑟𝑜𝑝 𝑎𝑡 𝑠𝑜𝑢𝑟𝑐𝑒 𝑑𝑢𝑟𝑖𝑛𝑔 𝑠𝑡𝑒𝑎𝑑𝑦 𝑠𝑡𝑎𝑡𝑒( 𝑔𝑖𝑣𝑒𝑛)
RESULT
The cable is selected based on the calculated values
 Thermal ampacity (derated current)
 Short circuit withstand capacity
 Steady state voltage drop
DISTRIBUTION TRANSFORMER SIZING
Purpose
To select the optimum sizing of the distribution transformer
Reference
 IS 2026 – part I – gives the specification of power transformer
 IS 325 – gives the specifications of 3 phase induction motor
Assumptions
 Voltage drop due to source during the steady state-compensated by OLTC power
transformer and 100% voltage is maintained at source.
I
Q
𝑉𝑃ℎ
IXsin(90-Q)IX
IXcos(90-Q)
V
IR

Designinputs
 HV side voltage (𝑉𝐻 )
 LV side voltage (𝑉𝐿 )
 Frequency (f)
 Total maximum demand (MD)
 Total connected load (TCL)
 Design margin (DM)
 System power factor
 LV side phase voltage (VPh)
Largest rating motor data
 Power rating
 Type of motor and starter
 Full load power factor and Starting power factor
 Ratio of starting current to full load current
 Full load efficiency
 Motor cable details ( dimensions, type and material used)
 Number of runs
 Length of cable (Lm)
 Resistance of cable (Rm)
 Reactance of cable (Xm )
 Source parameters (KVA) and source fault (MVA)
Steady State capacity calculations
Transformer capacity required =
𝑀𝐷
1−𝐷𝑀
Based on this the size of the transformer is selected.
Checking on capacity for transient conditions
Base load
BL= MD – P*MD/TCL/Cos φ
Base load current
Im1 =
BL ∗ 1000
√3 V
Full load current of motor
Ifl =
P ∗ 1000
√3VL ∗ cosφ ∗ η
Starting current of motor
Ist = 1.2 ∗ K ∗ Ifl

Total starting KVA required = STLM + BL = transformer overload withstanding capacity
(200%)
Overload withstand capacity of transformer = transformer overload withstanding capacity
(200%) + selected size
Checking for voltage drop during largest motor starting
 Base impedance at 1 MVA and given KV (Ω )
 Source fault MVA
 Source reactance (Xs)
Transformer parameters
 % impedance (Z)
 Transformer reactance (XT)
 Net source reactance (XT + Xs = Xs0)
Phasor diagram
Calculations
From phasor diagram
Vph = (VmcosQ + IsRm)2
+ (𝑉𝑚 𝑠𝑖𝑛𝑄 + 𝐼𝑆 𝑋 𝑚 + 𝐼𝑠 𝑋𝑠𝑜 + 𝑋𝑠𝑜( 𝐼 𝑚2 − 𝐼 𝑚1))2
motor starting current
Is =
Ist Vm
VPh
bus voltage
Vb = (VmcosQ + IsRm)2
+ (𝑉𝑚 𝑠𝑖𝑛𝑄 + 𝐼𝑆 𝑋𝑡)2
VmcosQ
Vph
Vb
Vm
VmsinQ
IXX0
𝐼sXm
Is

So far from these equations
Vph
2
= (VmcosQ +
Ist RmVm
VPh
)2
+ (𝑉𝑚 𝑠𝑖𝑛𝑄 +
𝐼𝑆 𝑉𝑚(𝑋 𝑚 + 𝑋𝑠𝑜
𝑉𝑃ℎ
+ 𝐼 𝑚1 𝑋𝑠𝑜
(𝑉𝑃ℎ − 𝑉𝑏)
𝑉𝑏
)2
RESULT:
Using the rating of transformer KVA thermal loading on transformer during motor starting ,
voltage available at motor during motor starting, voltage available at bus during motor starting,
the transformer size is selected.
Electrical Calculations – Lighting Calculations
The lighting calculations has been carried out based on the outline design requirements from
BMRCL, Design basis reports and design review discussions with general consultants. DIALUX
software has been used for lighting calculations. The lighting fixtures have been selected to suit
the architectural ceiling plan.
General inputs:
 Height of the room in m
 Mounted height m
 Maintenance factor
We determine the following
 The minimum lux in the corners 𝐸 𝑚𝑖𝑛 [lx]
 The maximum lux which is the concentrated intensity of light 𝐸 𝑚𝑎𝑥[lx]
 The average lux in the room 𝐸 𝑎𝑣𝑔 [lx]
 Reflection factor 𝜌[%]
 Utilization factor u0
For the surfaces: work plane, floor, ceiling and walls
From the determined parameters we decide the luminaries’ parts list.

CABLE SCHEDULE
The majestic interchange station was considered for cable scheduling during the internship period. Cable scheduling was done for power cables,
normal earth and clean earth. The routing sequence of the cables was found out from the schematic layout diagram using true view software and
the length of the cables are measured by using ZWCad software.
The routing sequence is tabulated as follows.
From
From
(code) To
To
(code)
Cable ID
Length
in km
Insulation
type
Core Area
No of
core and
size
No of
runs
Routing
sequence
The beginning and ending points of the cable connecting every equipment in the station is considered and their ‘from’ and ‘to’ codes are
generated. The cable ID is thus generated using the ‘from’ and ‘to’ codes to distinctly identify every cable, to ease the cable laying process
during construction. The details of the cables namely, their length, insulation type (XLPE), Core type, Area , Number of cores, core sizes and the
number of runs are tabulated as shown above.
The Routing Sequence is done by comparing the earthing layout with the combined service layout and according to the client inputs regarding
the selection of trays for the respective cables in their route.
From the routing sequence the cable scheduling is done for calculating the free space available and proposing new sizes when there is
contradiction. The cable schedule tabulation is shown below.
Route
tag
Space
Req.
Spec.
Free
space
%
Total
Space
Req.
Tray
Size
Provided
No of
trays
Space
Avail.
Excess
space
avail.
Free
Space
%
Proposed
Tray
Size
No of
Trays
Props.
Space
avail.
props
Free
space
avail.
Props.
Type
Route tag: This gives the distinct tag given to every tray route.

Space required: Space required is calculated from the routing sequence and the size of that cable.
Specified free space %: This is given by the client with the idea of future expansion.
Total space required: It is the sum of the space required and the free space specified.
Tray size provided: This gives the size of the trays provided by the client.
Number of trays: It gives the number of trays provided.
Space available: This is given by the product of tray size and the number of cables. This gives the area available for placing the cables.
Excess space available: This is difference between the total space required and the space available.
Free space % : It gives the percentage of free space that is available.
Number of trays proposed and their area:If the free space % is in negative then new tray size or a new number of trays is proposed. If the free
space available is too large, the proposed tray number or size can be reduced.
Type : this specifies the type of the tray that is given. It can be perforated or ladder .
Ladder cable trays Perforated
Thus cable scheduling is a very important work when laying cables. This is done to avoid overcrowding of cables in any tray a nd to avoid
increased free space.

“There is NO Substitute for Hard Work.”
Thomas Edison (1847-1931);
Inventor, Businessman
THANKYOU
B. SINDHUJA
M.G.VISHALI

INTERNSHIP REPORT (FINAL)

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