PowerPoint Presentation
9/18/2014mydocumentsNTPI_excitationControl1E.M.F.-RelationNSEMF,
E [volts] = B * l * v.
B = webers / meter Sq.L = length in MetersV = Velocity in
Meters/SecondcurrentcurrentARMATURELOADRotating Armature
Generator
Rotating Field Generator
Typical Supply System
The Power System - It ComprisesGeneration Units that produce
electricityHigh Voltage Transmission Lines that transport
electricity over long distancesLow Voltage Transmission Lines That
delivers electricity to ConsumersSubstations, which are the part of
the electricity transmission and distribution system where the
voltages are transformed to lower levels for distributing power to
end user.
Major PlayersCentral Utilities such as NTPC, NHPC, Nuclear Power
Corporation, Damodar Valley Corporation andNEEPCO.State Electricity
Boards which are state-owned utilities like Orissa, Haryana, AP,
Uttar Pradesh, Karnataka etc.Licensees such as BSES and
CESC.Independent Power Projects (IPPs)Four basic energy sources
Electric Power GenerationFossil fuel such - coal, oil and natural
gas
Hydro electricity
Nuclear Power and
Renewable Energy bio-fuels, solar, biomass, wind and tidal.
TransmissionIn India, the power plants typically produce 50
cycle/second (Hertz) alternating current (AC) with voltages between
11 kV and 25 kV. Higher voltage means lower current but the
insulation thickness and size increases.Hence an optimum voltage is
selected.Electric power is brought from the power plant to the
consumer through an extensive transmission and distribution
(T&D) system. comprising distribution networks, state grids and
regional grid.
Stages of TransmissionAt the plant, the 3-phase voltage is
generated and stepped up to a higher voltage for transmission on
conductors strung on cross country towers.High voltage(HV) and
Extra High Voltage (EHV) transmission in the next stage to
transport A.C. power from the power plant over long distances at
voltages like 220kV, 400kV and 760 kV. For longer distances and
higher powers, higher voltages are economical.In special cases HVDC
(High voltage direct current transmission + 500 kV DC) is
preferred.Example 1500 MW Chandrapur Padghe HVDC in
Maharashtra.Stages of Transmission .Sub- Transmission network at
132 kV. 110kV, 66 kV or 33 kV constitutes the next link towards the
end user.Network planning concept >(n-1)Major Players: Most of
the states restructured their State Electricity Boards and have
unbundled them in three entities- Generation, Transmission and
Distribution.
DistributionDistribution at 11KV (6.6 KV in US) constitutes the
last link to the consumers which is connected directly or through
step-down transformers.11/0.4 KV or 6.6/0.110 KV Transformers.
These transformers bring the voltage levels down to 400 V / 110 V.
for 3 phase, 4 wire secondary distributions.The single phase
residential lighting load is connected between any phase and
neutral (230 V/110 V) and 3-phase load is connected across 3-phase
lines directly.
Power Distribution SystemElectricity is carried through a
transmission network of high voltage lines. Usually, these lines
run into hundreds of kilometres and deliver the power into a common
power pool called the grid.The grid is connected to load centres
(cities) through a sub-transmission network of usually 33 kV (or
sometimes 66 kV) lines. These lines terminate into a 33 kV (or 66
kV) substation, where the voltage is stepped-down to 11 kV for
power distribution to load points through a distribution network of
lines at 11 kV and lower.
The power network concern to the end-user is the distribution
network of 11 kV lines or feeders downstream of the 33 kV
substations. Each 11 kV feeder which emanates from the 33 kV
substation branches further into several subsidiary 11 kV feeders
to carry power close to the load points (localities, industrial
areas, villages, etc.). At these load points, a transformer(DTC),
further reduces the voltage from 11 kV to 415 V to provide the
last-mile connection through 415 V feeders (also called LT feeders)
to individual customers, either at 240 V (as single-phase supply)
or at 415 V (as three-phase supply). The utility voltage of 415 V,
3-phase is used for running the motors for industry and
agricultural pump sets and 240 V, single phase is used for lighting
in houses, schools, hospitals and for running industries,
commercial establishments, etc.
Components of T&D SystemTransformers.Circuit Breakers
.Isolators.Surge Diverters. (L.A.) Horn Gaps.Drop Out Fuses
(D.O.)Current Transformers (C.T.)Potential transformers
(P.T.)Reactors.Capacitors.Cables .Conductors.CCGT-UTRAN-SWITCHGEAR
DISTRIBUTION - 18/09/2014 - P 17Current Transformer.Measurement of
current is the essence in all transducers.
The current carrying conductor is threaded through a donut
shaped device.
A C.T. produces an alternating current or
alternating voltage proportional to the current being
measured.
CCGT-UTRAN-SWITCHGEAR DISTRIBUTION - 18/09/2014 - P 18
3-phase C.T.sCCGT-UTRAN-SWITCHGEAR DISTRIBUTION - 18/09/2014 - P
19LIVE TANK C.T.
CCGT-UTRAN-SWITCHGEAR DISTRIBUTION - 18/09/2014 - P 20DEAD TANK
C.T.
CCGT-UTRAN-SWITCHGEAR DISTRIBUTION - 18/09/2014 - P 21
E.H.V.-C.T.
DRYSHIELD
TYPE
CCGT-UTRAN-SWITCHGEAR DISTRIBUTION - 18/09/2014 - P
22C.V.T.E.H.V.BUS / LINECapacitorswindingsWhen a C.T.is to be
changed, proper matching is MUST
LIGHTNING ARRESTERS
The earthing screen and ground wires can well protect the
electrical system against direct lightning strokes but they fail to
provide protection against travelling waves, which may reach the
terminal apparatus. The lightning arresters or surge diverters
provide protection against such surges. A lightning arrester or a
surge diverter is a protective device, which conducts the high
voltage surges on the power system to the ground
EHV LIGHTNING ARRESTERSystem Voltage : 0.5 ~ 245kVRated Voltage
(kV) : 0.5 ~ 216kVNominal discharge current (kA) : 5 ~ 10 kVHigh
current capability (4/10us) kA : 65 ~ 100Energy Class : D, 1, 2
& 3Energy absorption Capability kJ/kV : 2 ~ 8Short Circuit
(Pressure relief) kA : 40Standard in accordance with : IEC 60099-4
& IS 3070 Part III
Working Principle of L.A. Surge Arrester consists of highly
non-linear varistor elements housed in a non porous electrical
porcelain housing . When an electric surge due to natural lightning
or switching action appears across the arrester, the block stack
allows the entire energy to earth by posing a very low resistance
and instantaneously recovers to its original insulation property
after the passage of surge, getting ready for next
operation.Lightening Arrester / Surge Diverter
L.A. FunctioningIt consists of a spark gap in series with a
non-linear resistor. One end of the diverter is connected to the
terminal of the equipment to be protected and the other end is
effectively grounded. The length of the gap is so set that normal
voltage is not enough to cause an arc, but a dangerously high
voltage will break down the air insulation and form an arc. The
property of the non-linear resistance is that its resistance
decreases as the voltage (or current) increases and vice-versa.
This is clear from the volt/amp characteristic of the resistor
shown in Fig.The action of the lightning arrester or surge diverter
is as under:(i) Under normal operation, the lightning arrester is
off the line i.e. it conducts no current to earth or the gap is
non-conducting(ii) On the occurrence of over voltage, the air
insulation across the gap breaks down and an arc is formed
providing a low resistance path for the surge to the ground. In
this way, the excess charge on the line due to the surge is
harmlessly conducted through the arrester to the ground instead of
being sent over the line.
(iii) It is worthwhile to mention the function of non-linear
resistor in the operation of arrester. As the gap sparks over due
to over voltage, the arc would be a short-circuit on the power
system and may cause power-follow current in the arrester. Since
the characteristic of the resistor is to offer low resistance to
high voltage (or current), it gives the effect of short-circuit.
After the surge is over, the resistor offers high resistance to
make the gap non-conducting.Horn Gap Protection
Working of Horn Gap ProtectionHorn shaped metal rods A and B
separated by a small air gap. The distance between horns gradually
increases towards the top as shown. The horns are mounted on
porcelain insulators. One end of horn is connected to the line
through a resistance and choke coil L while the other end is
effectively grounded. The resistance R restricts the follow current
to a small value. The choke coil offers small reactance at normal
power frequency but a very high reactance at transient frequency.
Thus the choke does not allow the transients to enter the apparatus
to be protected. The gap between the horns is so adjusted that
normal supply voltage is not enough to cause an arc across the
gap.Under normal conditions, the gap is non-conducting i.e. normal
supply voltage is insufficient to initiate the arc between the gap.
On the occurrence of an over voltage, spark-over takes place across
the small gap G. The heated air around the arc and the magnetic
effect of the arc cause the arc to travel up the gap. The arc moves
progressively into positions 1,2 and 3. At some position of the arc
(position 3), the distance may be too great for the voltage to
maintain the arc; consequently, the arc is extinguished. The excess
charge on the line is thus conducted through the arrester to the
ground.Kingston/load dispatch/20Aug0933Integration of WR-ER-NR-NER
NRWRSRNERERHVDC Back to Back400/220 kV AC linesHVDC Bi Pole400 kV
AC linesPower system in India
Power ratings of lines Normally for continuous operation the
transmission lines on various voltage are designed to carry maximum
power loads at the designed maximum conductor temperature of 65
deg. C. as followsAt 132 kv with 'Panther' ACSR = 75 MVAAt 220 kv
with 'Zebra' ACSR = 200 MVAAt 400 kv with 'Moose' ACST = 500
MVACurrent ratings of EHV Conductors.Sl. No.Size of Conductor (Code
Name)Current carrying Capacity in AmperesAt maxim. designed
Temperature of 650 CAt maxim. designed temperature of 750 CNew
Conductor (Up to one year)Old Conductor (Beyond 10 years)New
Conductor (Up to one year)Old Conductor (Beyond 10 years)1.'Dog'
ACSR141.12150.20229.65245.062.'Panther'
ACSR179.89200.60340.83371.423.'Zebra'
ACSR201.26249.51496.46553.704.'Moose'
ACSR133.60218.89530.51603.78Surge Impedance LoadingThe
characteristic impedance of a transmission line is expressed in
terms of the surge impedance loading (SIL), or natural loading,
being the power loading at which reactive power is neither produced
nor absorbed:
in which V is the phase voltage in volts.Loaded below its SIL, a
line supplies reactive power to the system, tending to raise system
voltages. Above it, the line absorbs reactive power, tending to
depress the voltage. The Ferranti effect describes the voltage gain
towards the remote end of a very lightly loaded (or open ended)
transmission line. Underground cables have a very low
characteristic impedance, resulting in an SIL that is typically in
excess of the thermal limit of the cable. Hence a cable is almost
always a source of reactive power.
Ferranti EffectFerranti effect is an increase in voltage at the
receiving end of a long transmission line. This occurs when the
line is energized but is a very lightly loaded or the load is
disconnected. The capacitive line charging current produces a
voltage drop across the line inductance that is in-phase with the
sending end voltages. Therefore both line inductance and
capacitance are responsible for this phenomenon.The Ferranti Effect
will be more pronounced the longer the line and the higher the
voltage applied. The relative voltage rise is proportional to the
square of the line length.The Ferranti effect is much more
pronounced in underground cables, even in short lengths, because of
their high capacitance.
ACSR CONDUCTORS
ALL ALUMINIUM CONDUCTORS (AAC)
This conductor is manufactured from electrolytically refined
(E.C.GRADE) aluminium, having purity of minimum 99.5% of aluminium.
This conductor is used mainly in urban areas
The spacing is short and the supports are close. All aluminium
conductors are made up of one or more strands of aluminium wire
depending on the end usage. These conductors are also used
extensively in costal because it has a very high degree of
corrosion resistance.AAA CONDUCTOR
ALL ALUMINIUM ALLOY CONDUCTORS (AAAC)
This conductor is made from aluminium-magnesium-silicon alloy of
high electrical conductivity.It contains enough magnesium silicide
to give it better mechanical properties after treatment. These
conductors are generally made out of aluminium alloy 6201. AAAC
CONDUCTOR has a better corrosion resistance and better strength to
weight ratio and improved electrical conductivity than ACSR
CONDUCTOR on equal diameter basis.
TYPICAL S/S SCHEMESIMILAR WILL BE FOR LOWER VOLTAGES
Single Bus System
Single Bus System is simplest and cheapest one. In this scheme
all the feeders and transformer bay are connected to only one
single bus as shown. Advantages of single bus systemThis is very
simple in design.This is very cost effective schemeThis is very
simple to operateDisadvantages of single bus systemOne major
difficulty of these type of arrangement is that, maintenance of
equipment of any bay is not possible without interrupting the
feeder or transformer connected to that bay.
Advantages of single bus system with bus sectionalizerIf any of
the sources is out of system, still all loads can be fed by
switching on the sectional circuit breaker or bus coupler
breaker.If one section of the bus bar system is under maintenance,
part load of the substation can be fed by energizing the other
section of bus bar.Disadvantages of single bus system with bus
sectionalizerAs in the case of single bus system, maintenance of
equipment of any bay is not be possible without interrupting the
feeder or transformer connected to that bay.The use of isolator for
bus sectionalizing does not fulfill the purpose. The isolators have
to be operated off circuit and which is not possible without total
interruption of bus bar. So investment for bus-coupler breaker is
required.
Double Bus SystemIn double bus bar system two identical bus bars
are used in such a way that any outgoing or incoming feeder can be
connected to any of the bus.By closing any of the isolators one can
put the feeder to associated bus. Both buses are energized and
total feeders are divided into two groups, one group is fed from
one bus and other from other bus. But any feeder at any time can be
transferred from one bus to other. Advantages of Double Bus
SystemDouble Bus Bar Arrangement increases the flexibility of
system.The arrangement permits breaker maintenance without
interruption.
One & Half Breaker SystemThis is an improvement on the
double breaker scheme to effect saving in the number of circuit
breakers. For every two circuits only one spare breaker is
provided. The protection is however complicated . As shown in the
figure that it is a simple design, two feeders are fed from two
different buses through their associated breakers and These two
feeders are coupled by a third breaker which is called tie breaker.
During failure of any feeder breaker, the power is fed through the
breaker of the second feeder and tie breaker.Therefore each feeder
breaker has to be rated to feed both the feeders, coupled by tie
breaker.
Main & Transfer Bus This is an alternative of double bus
system. The main conception of Main and Transfer Bus System is,
here every feeder line is directly connected through an isolator to
a second bus called transfer bus. The isolator in between transfer
bus and feeder line is generally called bypass isolator. The main
bus is as usual connected to each feeder. There is one bus coupler
which couples transfer bus and main bus .through a circuit breaker.
If necessary the transfer bus can be energized by main bus power by
closing the bus coupler breaker. Then the power in transfer bus can
directly be fed to the feeder line by closing the bypass isolator.
If the main circuit breaker associated with feeder is switched off
or isolated from system, the feeder can still be fed in this way by
transferring it to transfer bus.
Ring Bus It provides a double feed to each feeder circuit. One
breaker under maintenance or otherwise does not affect supply to
any feeder. But this system has two major disadvantages. One as it
is closed circuit system it is impossible to extend in future and
hence it is unsuitable for developing system. Secondly, during
maintenance or any other reason if any one of the circuit breaker
in ring loop is switch off, reliability of system becomes very poor
as the closed loop becomes opened. Since, at that moment for any
tripping of any breaker in the open loop causes interruption in all
the feeders between tripped breaker and open end of the loop.
760 / 400 KV Lines 760 / 400 KV Sub Stations.220/132 KV
Lines.220/132 KV S/S 33/22 KV Lines 33/ KV S/S 11 KV Lines 11 KV
11/ 0.440 KV DTCs
Supply SchemesRadial Feeders.Ring Mains.Major cities have
220/132 KV ring mains.220/132/33 KV s/s can be fed from two
sides.Even 11/0.440 KV DTCs can be fed from two ends.DTCs ideal
connected load is 70% of its capacity.When one DTC fails, the loads
can be shifted to adjoining DTCs. Special ComponentsReactors- For
long +400 KV lines, reactors are used to limit switching surge
voltages.Capacitor Banks EHV Capacitor banks are used to improve
power factor and voltage.H.V.D.S.- This system eliminates 440 Volts
, L.T. lines which prevents theft.Consumers are directly fed from
the smaller DTCs (25 KVA) . Losses in LT line are 625 times of HT
line as the current is 25 times more in L.T.line.Power FactorThe
System load consists of active KW component and reactive KVAR
component.Vector sum of these two is the KVA load.
TRANSMISSION CONDUCTORSHigh-voltage overhead conductors are not
covered by insulation. The conductor material is an aluminium
alloy, made into several strands and possibly reinforced with steel
strands. Improved conductor material and shapes are regularly used
to allow increased capacity and modernize transmission circuits.
Conductor sizes range from 12mm2 to 750mm2, with varying resistance
and current-carrying capacity. Thicker wires would lead to a
relatively small increase in capacity due to the skin effect, that
causes most of the current to flow close to the surface of the
wire. Because of this current limitation, multiple parallel cables
(called bundle conductors) are used when higher capacity is needed.
Bundle conductors are also used at high voltages to reduce energy
loss caused by corona discharge.EHV SUB TRANSMISSION DISTRIBUTION
VOLTAGESLower voltages such as 66kV and 33kV are usually considered
subtransmission voltages but are occasionally used on long lines
with light loads. Voltages less than 33kV are usually used for
distribution. Voltages above 230kV are considered extra high
voltage. Since overhead transmission wires depend on air for
insulation, minimum clearances to be observed to maintain safety.
Adverse weather conditions of high wind and low temperatures can
lead to power outages. Wind speeds as low as 43km/h can permit
conductors to encroach operating clearances, resulting in a
flashover and loss of supply.Oscillatory motion of the physical
line can be termed gallop or flutter depending on the frequency and
amplitude of oscillation.
Double Circuit Tower & Typical ACSR
Underground transmissionElectric power can also be transmitted
by underground power cables instead of overhead power lines.
Underground cables take up less right-of-way than overhead lines,
have lower visibility, and are less affected by bad weather.
However, costs of insulated cable and excavation are much higher
than overhead construction. Faults in buried transmission lines
take longer to locate and repair. Underground lines are strictly
limited by their thermal capacity, which permits less overload or
re-rating than overhead lines. Long underground cables have
significant capacitance, which may reduce their ability to provide
useful power to loads.
High-voltage direct current
High-voltage direct current (HVDC) is used to transmit large
amounts of power over long distances or for interconnections
between asynchronous grids. over very long distances, it is more
economical to transmit using direct current instead of alternating
current. For a long transmission line, the lower losses and reduced
construction cost of a DC line can offset the additional cost of
converter stations at each end. Also, at high AC voltages,
significant (although economically acceptable) amounts of energy
are lost due to corona discharge, the capacitance between phases
or, in the case of buried cables, between phases and the soil or
water in which the cable is buried.HVDC is also used for long
submarine cables because over about 30 kilometres AC can no longer
be applied. In that case special high voltage cables for DC are
built. Submarine connections up to 600 kilometres are currently in
use.CONTROL ON POWER FLOW HVDC links are sometimes used to
stabilize against control problems with the AC electricity flow.
The power transmitted by an AC line increases as the phase angle
between source end voltage and destination end increases, But too
great a phase angle will allow the generators at either end of the
line to fall out of step. Since the power flow in a DC link is
controlled independently of the phases of the AC networks at either
end of the link, this stability limit does not apply to a DC line,
and it can transfer its full thermal rating. A DC link stabilizes
the AC grids at either end, since power flow and phase angle can be
controlled independently.
Capacity
The amount of power that can be transmitted is limited. The
limits vary depending on the length of the line. For a short line,
the heating of conductors due to line losses sets a thermal limit.
If too much current is drawn, conductors may sag too close to the
ground, or conductors and equipment may be damaged by overheating.
For intermediate-length lines about 100 km , the limit is set by
the voltage drop in the line. For longer AC lines, system stability
sets the limit to the power that can be transferred. Capacity of
very long lines.The power flowing over an AC line is proportional
to the cosine of the phase angle of the voltage and current at the
receiving and transmitting ends. Since this angle varies depending
on system loading and generation, it is undesirable for the angle
to approach 90 degrees. Very approximately, the allowable product
of line length and maximum load is proportional to the square of
the system voltage. Series capacitors or phase-shifting
transformers are used on long lines to improve stability.
High-voltage direct current lines are restricted only by thermal
and voltage drop limits, since the phase angle is not material to
their operation.
Power Line Carrier CommunicationSpecial coupling capacitors are
used to connect radio transmitters to the power-frequency AC
conductors. Frequencies used are in the range of 24 to 500 kHz,
with transmitter power levels up to hundreds of watts. Several PLC
channels may be coupled onto one HV line. Filtering devices at
substations prevent the carrier frequency current from being
bypassed through the station apparatus and to ensure that distant
faults do not affect the isolated segments of the PLC system. These
circuits are used for control of switchgear, and for protection of
transmission lines. For example, a protective relay can use a PLC
channel to trip a line if a fault is detected between its two
terminals, but to leave the line in operation if the fault is
elsewhere on the system.While utility companies use microwave and
fiber optic cables for their primary system communication needs,
the power-line carrier apparatus is useful as a backup channel or
for very simple low-cost installations that do not warrant
installing fiber optic lines.
Power line carrier communication (PLCC) is mainly used for
telecommunication, tele-protection and tele-monitoring between
electrical substations through power lines at high voltages, such
as 110 kV, 220 kV, 400 kV. The major benefit is the union of two
applications in a single system, which is particularly useful for
monitoring electric equipment and advanced energy management
techniques.The modulation generally used in these system is
amplitude modulation. The carrier frequency range is used for audio
signals, protection and a pilot frequency. The pilot frequency is a
signal in the audio range that is transmitted continuously for
failure detection.
The voice signal is compressed and filtered into the 300 Hz to
4000 Hz range, and this audio frequency is mixed with the carrier
frequency. The carrier frequency is again filtered, amplified and
transmitted. The transmission power of these HF carrier frequencies
will be in the range of 0 to +32 dbW. This range is set according
to the distance between substations. PLCC can be used for
interconnecting private branch exchanges (PBXs).
Wave TrapTo sectionalize the transmission network and protect
against failures, a "wave trap" is connected in series with the
power (transmission) line. It consist of a resonant circuit, which
blocks the high frequency carrier waves (24 kHz to 500 kHz) and
permits the power frequency current (50 Hz - 60 Hz) to pass
through. Wave traps are used in switchyard of most power stations
to prevent carrier from entering the station equipment. Each wave
trap has a lightning arrester to protect it from surge voltages.A
coupling capacitor is used to connect the transmitters and
receivers to the high voltage line. This provides low impedance
path for carrier energy to HV line but blocks the power frequency
circuit by being a high impedance path. The coupling capacitor may
be part of a capacitor voltage transformer used for voltage
measurement.Wave Trap details
A Line enters the sub station
Symbols
Distribution Details Feeders route the power from the substation
throughout the service area. They are either overhead distribution
lines mounted on wooden poles, orUnderground cable sets. Feeders
operate at the primary distribution voltage in primary distribution
system and secondary distribution voltage in the secondary
distribution systemPrimary Voltage 11KV, 22kv , 33 kvSecondary
Voltage 440 VoltsFeederA feeder consists of all primary or
secondary voltage level segments of distribution lines between two
substations orBetween a substation and an open point . The most
common primary distribution voltages in use are 11 kV, 22 kV and 33
kV. The main feeder, may branch into several main routes.
Configuration of Feeders
Feeders are connected in a configuration, which depends on the
type of network required in the distribution system. Three types of
network are normally available in the electrical distribution
system: Radial Loop Cross-loop network.Layout of FeedersRadial
feeder emanates from one point and ends at the other.In radial
network, load transfer in the case of breakdown is not possible.A
radial feeder can be loaded to its maximum capacity, but, in the
case of breakdown, quite a large area may remain in dark until the
fault is detected and repaired.In loop arrangement, two feeders are
connected to each other so that in thecase of breakdown, the faulty
section can be isolated and the rest of theportion can be switched
on. In loop system, the feeder is normally loaded to 70% of its
capacity so that in the event of breakdown it can share the load of
other feeders also.A cross-loop network provides multiple paths and
the flexibility further increases. In case of breakdown in any
line, the faulty system can be isolated and supply can be resumed
very quickly. In this type of network, feeders should normally be
loaded to 70% of their current carrying capacity. This system is
highly reliable, but more expensive.Various Feeder Layouts
Comparison of Feeder Layouts
Ring mainsIn big cities, the concept of 33 kV ring main is very
popular and two ring mains are laid: one outer and one inner. The
outer ring main is laid using the panther conductor and the inner
ring main is laid using the dog conductor.The use of these two
types of ring mains provides excellent flexibility to the system
and at the time of breakdown, supply can be immediately switched on
from another 132 kV substation. While making any distribution
planning for metros, the aspect of outer and inner 33 kV ring mains
is extremely essential and should be included for providing
uninterrupted supply.OUTER & INNER RING MAIN FOR REDUNDANCY
Arial Bunched cables 1. Elimination of cable trenching work in
grounds having high water table making trenching difficult andAlong
narrow streets which causes serious public inconvenience.2.
Utilization of existing assets such as poles and structures for
supporting the cable, which reduces cost of installation.3.
Elimination of cable faults due to dig in damages caused by other
agencies.4. Speedy service connections in LT
distribution.H.V.D.S.Significantly high losses take place in the
secondary distribution system. (440 Volts)This is due to higher
current densities and ease of pilferage at low voltages.. One of
the latest innovations in efforts to reduce technical and
commercial losses is the use of High Voltage Distribution
System(HVDS) or LT-less system.For 100 KVA load; HT =6 Amps; LT =
150 Amps.Typical HVDS No L.T. Line
HVDS - Advantagesuse of small size ACSR or aluminium alloy
conductor Better voltage profile; reduced line losses; and reduced
commercial losses.Improved Reliability and Security of SupplyThe
use of HT distribution leads to improved reliability and security
of supply for the following reasons:The faults on HT lines are far
less compared to those of LT lines.Number of small distribution
transformers is high in HVDS.The failure of one transformer does
not affect supply to other consumers connected to other
transformers. In the event of failure of distribution transformers,
only a small number of consumers (2 to 3 power consumers or 10 to
15 domestic consumers) would be affected. On the other hand, a
large distribution transformer supplies power through LV
distribution lines to even remotely located consumers in LVDS.
Hence, the failure of an existing large size distribution
transformer would affect a group of 40 to 50 powe consumers and/or
100 to 200 domestic consumers.THANK YOUELEMENTSELEMENTS OF SUPPLY
SYSTEMSr.No.IN A POWER
STATION1SWITCHGEARSIN-DOOROUT-DOOREHVHTLT2TRANSFORMERSSTEP-UPSTATIONUATAUXILLARYLIGHTING3CABLESSINGLE-Ph3-Ph.ArmouredPVCPILCX.L.P.E.H.T.L.T.4TERMINATION5CIRCUIT
BREAKERSO.C.B.M.O.C.B.A.B.C.B.S.F.-6V.C.B.M.C.B.6ISOLATORS7SWITCHES8BUS-BARS-INSULATORS-GANTRIESE.H.V.H.T.L.T.PORCELAINPVC9EARTHING
ARRANGEMENTSOLIDRESISTANCEREACTANCE10EARTHING TRANSFORMERS11NEUTRAL
GROUNDING TRANSFORMER12PANELS13D.C. SUPPLY
SYSTEM.---D.C.D.B.14STATION BATTERIES AND CHARGERS
TRANSFORMERSTRANSFORMERSPROTECTIONSOVER-CURRENTEARTH-FAULTR.E.F.
[RESTRICTED EARTH FAULT]FOR INTERNAL FAULTSBUCHHOLZ RELAYFOR
INCIPIENT INTERNAL FAULTSDIFFERENTIAL PROTECTION
CTPRIMARYTANKSECONDARIESBASE
INSULATOR
Sheet3
ELEMENTSELEMENTS OF SUPPLY SYSTEMSr.No.IN A POWER
STATION1SWITCHGEARSIN-DOOROUT-DOOREHVHTLT2TRANSFORMERSSTEP-UPSTATIONUATAUXILLARYLIGHTING3CABLESSINGLE-Ph3-Ph.ArmouredPVCPILCX.L.P.E.H.T.L.T.4TERMINATION5CIRCUIT
BREAKERSO.C.B.M.O.C.B.A.B.C.B.S.F.-6V.C.B.M.C.B.6ISOLATORS7SWITCHES8BUS-BARS-INSULATORS-GANTRIESE.H.V.H.T.L.T.PORCELAINPVC9EARTHING
ARRANGEMENTSOLIDRESISTANCEREACTANCE10EARTHING TRANSFORMERS11NEUTRAL
GROUNDING TRANSFORMER12PANELS13D.C. SUPPLY
SYSTEM.---D.C.D.B.14STATION BATTERIES AND CHARGERS
TRANSFORMERSTRANSFORMERSPROTECTIONSOVER-CURRENTEARTH-FAULTR.E.F.
[RESTRICTED EARTH FAULT]FOR INTERNAL FAULTSBUCHHOLZ RELAYFOR
INCIPIENT INTERNAL FAULTSDIFFERENTIAL PROTECTION
CTPRIMARYTANKSECONDARIESBASE
INSULATORINSULATOR
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