INDUSTRIAL TRAINING REPORT

ON

PTA(power plant maintenance & utility)

AT

INDIAN OIL CORPORATION LIMITED,PANIPAT

From:4th july 2011 to 12th august 2011

Submitted By:

Gaurav Varshney

287084

B.tech(3RD Year)

Faculty of engg. & tech.(MRIU),faridabad

INDEX

ACKOWLEDGEMENT

BRIEF INFO

PETROCHEMICALS

PRODUCTS

TRANSFORMER

UNINTERRUPTED POWER SUPPLY

COAXIAL CABLES

CIRCUIT BREAKER

RELAYS

CAPTIVE POWER PALNTS

ACKOWLEDGEMENT

In every step of achiving any concept,there is need of guidance, inspiration & help for better result.

I am hereby thankful to following persons for not only their valuable instructions that they given me to prepare this project report but also for their cooperation during the training period.

1.Mr.Y.G.Rao(Sr. Training Officer)2.Mr.M.D.Sahola3.Mr.Sanjay kumar4.Mr.Pawan Rawat

I am equally thankful to all other workers who tried their best to help me & provided me informations required for training and my friends who directly or indirectly helped me for completion of this project report.

BRIEF INFO

Panipat Refinery (Near Delhi)

Panipat Refinery has doubled its refining capacity from 6 MMT/yr to 12 MMT/yr with the commissioning of its Expansion Project. Panipat Refinery is the seventh refinery of IndianOil. It is located in the historic district of Panipat in the state of Haryana and is about 23 km from Panipat City. The original refinery with 6 MMTPA capacity was built and commissioned in 1998 at a cost of Rs. 3868 crore (which includes Marketing&Pipelines installations). The major secondary processing units of the Refinery include Catalytic Reforming Unit, Once Through Hydrocracker unit, Resid Fluidised Catalytic Cracking unit, Visbreaker unit, Bitumen blowing unit, Sulphur block and associated Auxiliary facilities. In order to improve diesel quality,a Diesel Hydro Desulphurisation Unit (DHDS) was subsequently commissioned in1999. Referred as one of India’s most modern refineries, Panipat Refinery was built using global technologies from IFP France; Haldor-Topsoe, Denmark; UNOCAL/UOP, USA; and Stone &Webster, USA. It processes a wide range of both indigenous and imported grades of crude oil. It receives crude from Vadinar through the 1370 km long Salaya-Mathura Pipeline which also supplies crude to Koyali and Mathura Refineries of IndianOil. Petroleum products are transported through various modes like rail, road as well as environment-friendly pipelines. The Refinery caters to the high-consumption demand centres in North-Western India including the States of Haryana, Punjab, J &K, Himachal, Chandigarh, Uttaranchal, as well as parts of Rajasthan and Delhi. 

The LPG produced from the refinery is pumped through a dedicated pipeline to IndianOil’s Kohand Bottling plant where bottling and bulk

despatches are done. Panipat Refinery has also developed new products like 96 RON petrol, and sub-Zero diesel for the Indian army. It is already operating above 100% capacity for the last four years.

Petrochemicals

India is amongst the fastest growing petrochemicals markets in the world. Taking this into consideration and to enhance its downstream integration, IndianOil is focusing on increasing its presence in the domestic petrochemicals sector besides the overseas markets through systematic expansion of customer base and innovative supply logistics. Petrochemicals have been identified as a prime driver of future growth by IndianOil. The Corporation is envisaging an investment of Rs 30,000 crore in the petrochemicals business in the next few years. These projects will utilise product streams from the existing refineries of IndianOil, thereby achieving better exploitation of the hydrocarbon value chain. Beginning with a low-investment, high-value projects such as Methyl Tertiary Butyl Ether (MTBE) and Butene-1 at Gujarat Refinery, Vadodara, IndianOil has set up a world-scale Linear Alkyl Benzene (LAB) plant at Gujarat Refinery and an integrated Paraxylene/Purified Terephthalic Acid (PX/PTA) plant at Panipat. A Naphtha Cracker complex with downstream polymer units is also in operation at Panipat. 

These initiatives are designed to catapult IndianOil among the top three petrochemicals players in Southeast Asia in the long term. In order to penetrate the petrochemicals market effectively, a separate Strategic Business Unit (SBU) has been created in IndianOil for marketing of petrochemicals. This SBU has five exclusive sub-groups, classified product wise (LAB, PTA, Polymers) and function wise (Logistics & Exports), in addition to regional/field set-ups to offer reliable customer service. This SBU has already established IndianOil's LAB business both in India and abroad. Today, IndianOil is a major supplier to the key players in the detergent industry, both national and international. Similarly, in PTA business, all major domestic customers are catered to by IndianOil. A robust logistics model has been the key to IndianOil's success story and facilities have been put in place for seamless product dispatches to customers by rail, road and sea. 

Paraxylene/Purified Terephthalic Acid (PX/PTA), Panipat: 

The most technologically advanced plant in the country, the PX/PTA plant marks IndianOil’s major step towards forward integration in the hydrocarbon value chain by manufacturing Paraxylene (PX) from captive Naphtha and thereafter, converting it into Purified Terephthalic Acid (PTA). The integrated Paraxylene/Purified Terephthallic Acid (PX/PTA) complex was built at a cost of Rs. 5,104 crore within the Panipat Refinery in Haryana. The PTA Plant is the single largest unit in India with a world-scale capacity of 5,53,000 MTPA, achieving economy of scale. The process package for the PTA plant was prepared by erstwhile M/s Dupont, UK (now M/s. Invista) and that of the Paraxylene Unit was prepared by M/s UOP, USA. M/s EIL and M/s Toyo Engineering were the Project Management Consultants (PMC) for executing the PTA and PX respectively. The Paraxylene plant is designed to process 5,00,000 MTPA of heart-cut Naphtha to produce about 3,60,000 MTPA of PX. Naphtha is sourced from IndianOil’s Panipat and Mathura refineries, for which Naphtha splitter units are set up at the respective refineries. The PTA unit produces 5,53,000 MTPA of Purified Terephthalic Acid from Paraxylene. 

Naphtha Cracker Plant, Panipat: 

The world-class Naphtha Cracker at Panipat, built at a cost of Rs 14,400 crore, is the largest operating cracker capacity in India. 

The feed for the unit is sourced internally from IndianOil's Koyali, Panipat and Mathura refineries. The Naphtha Cracker comprises of the following downstream units - Polypropylene (capacity: 600,000 tonnes), High Density Polyethylene (HDPE) (dedicated capacity: 300,000 tonnes) and Linear Low Density Poly Ethylene (LLDPE) (350,000 tonnes Swing unit with

HDPE), Mono Ethylene Glycol(MEG) plant (capacity: 325,000 tonnes). 

The cracker will produce over 800,000 tonnes per annum of ethylene, 600,000 tonnes per annum of Propylene, 125,000 tonnes per annum of Benzene, and other products viz., LPG, Pyrolysis Fuel Oil, components of Gasoline and Diesel. 

The Polypropylene (PP) unit is designed to produce high quality and high value niche grades including high speed Bi-axially Oriented Polypropylene (BOPP) (used for food packaging and laminations), high clarity random co-polymers (used for food containers and thin walled products) and super impact co-polymer grades (used for batteries, automobile parts, luggage and heavy duty transport containers). Polyethylene is used for making injection moulded caps, heavy duty crates, containers, bins, textile bobbins, luggage ware, thermoware, storage bins, pressure pipes (for gas and water), small blow-moulded bottles, jerry cans, etc.

ProductsIndianOil is not only the largest commercial enterprise in the country it is the flagship corporate of the Indian Nation. Besides having a dominant market share, IndianOil is widely recognized as India’s dominant energy brand and customers perceive IndianOil as a reliable symbol for high quality products and services. 

Benchmarking Quality, Quantity and Service to world-class standards is a philosophy that IndianOil adheres to so as to ensure that customers get a truly global experience in India. Our continued emphasis is on providing fuel management solutions to customers who can then benefit from our expertise in efficient sourcing and least cost supplies keeping in mind their usage patterns and inventory management. 

IndianOil is a heritage and iconic brand at one level and a contemporary, global brand at another level. While quality, reliability and service remains the core benefits to our customers, our stringent checks are built into operating systems, at every level ensuring the trust of over a billion Indians over the last four decades. 

Our Retail Brand template of XtraCare(Urban), Swagat(Highway) and Kisan Seva Kendras(Rural) are widely recognized as pioneering brands in the petroleum retail segment. IndianOil’s leadership extends to its energy brands - Indane LPG, SERVO Lubricants, Autogas LPG, XtraPremium Branded Petrol, XtraMile Branded Diesel, XtraPower Fleet Card, IndianOil Aviation and XtraRewards cash customer loyalty programme.

Diesel/Gas oilPetroleum derived diesel (called as petrodiesel) is a mixture of straight run product (150 °C and 350 °C) with varying amount of selected cracked distillates and is composed of saturated hydrocarbons (primarily paraffins including n , iso , and cycloparaffins), and aromatic hydrocarbons (including napthalenes and alkylbenzenes). 

Diesel is used in diesel engines, a type of internal combustion engine. Rudolf Diesel originally designed the diesel engine to use coal dust as a fuel, but oil proved more effective. Diesel engines are used in cars, motorcycles, boats and locomotives. Automotive diesel fuel serves to power trains, buses, trucks, and automobiles, to run construction, petroleum drilling and other off-road equipment and to be the prime mover in a wide range of power generation & pumping applications. The diesel engine is high compression, self-ignition engine. Fuel is ignited by the heat of high compression and no spark plug is used. 

The Indian Standard governing the properties of diesel fuels is IS 1460:2005 (5th Rev). Important characteristics are ignition characteristics, handling at low temperature, flash point. 

Diesel fuel often contains higher quantities of sulphur. In India , emission standards (equivalent to Euro II, Euro III, Euro IV) have necessitated oil refineries to dramatically reduce the level of sulphur in diesel in view of the auto fuel policy brought in force by Govt of India. 

BIS has brought out specification for "Diesel with 5% Biodiesel" that may be marketed in near future. 

Natural Gas

Over the years, Natural Gas has emerged as the 'fuel of choice' across the world. It is steadily replacing traditional fossil fuels due to its environment friendly characteristics which help in meeting the stipulated automobile emission norms. When compared with coal and oil, natural gas has a low carbon footprint due to its clean combustion features. Natural Gas has significant cost advantages too over crude oil and fuels such as Naphtha and commercial LPG. Demand for Natural Gas in India is primarily driven by the fertiliser and power sectors, which account for almost two-third of the country’s gas consumption. Gas-based power plants are quicker to build and incur lesser initial capital expenditure and are better suited to meet peak power demand.

Drawing on its vast experience and carefully nurtured skill sets, IndianOil has made successful forays in diverse areas such as Natural Gas, Petrochemicals, Exploration & Production, Renewable Energy, etc. With 12.5% equity in Petronet LNG Limited (PLL), IndianOil has marketing rights for 30% quantity of the LNG (Liquefied Natural Gas) procured by PLL from RasGas, Qatar under the long term agreement. Demand for Natural gas in India is growing and cannot be met by the current indigenous production. Hence, IndianOil is in the process of sourcing more quantities of LNG to meet the increasing requirements.

The Corporation entered the Natural Gas business in March 2004. Since then, by leveraging its inherent strengths and countrywide reach, IndianOil has significantly enhanced its customer base. In the year 2009-10, it clocked sales of 1.683 MMTPA (million metric tonnes per annum). 

Within the gas business, City Gas Distribution is a rapidly growing segment. Green Gas Ltd., IndianOil's joint venture with GAIL (India) Ltd., is already operational in Agra and Lucknow in the state of Uttar Pradesh and is further expanding to cater to the increased demand in various sectors. The consortium of IndianOil and Adani Energy has been successful in securing licenses to build city gas distribution networks in several cities. IndianOil is in the process of forming more strategic alliances for City Gas Distribution in other parts of the country.

IndianOil has the capabilities to supply regassified LNG to customers presently located in the Northern and Western regions of India. With the expansion of the pipeline network in Southern region as well as other parts of the country, IndianOil can supply gas to customers located near those pipelines. As a committed supplier, IndianOil is completely

responsible for delivery of gas to the customer’s premises. The transportation services of the company engaged in transportation of gas are hired to ensure deliveries. This model is used the world over wherein multiple gas suppliers operate through one transportation system. 

The “LNG at Doorstep” initiative involves making LNG available to the customers not connected by gas pipeline. Gas is transported through a cryogenic system, stored in a cryogenic holding tank at the target location and re-gassified on-site through vaporizers for use as a fuel. The entire operation is concealed, which eliminates the possibility of adulteration and pilferage. Introduced in August 2007, this initiative has been well received and is attracting more customers located away from the pipelines.

T ransforme r

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the

secondary winding and electrical energy will be transferred from the

primary circuit through the transformer to the load. In an ideal

transformer, the induced voltage in the secondary winding (Vs) is in

proportion to the primary voltage (Vp), and is given by the ratio  of the

number of turns in the secondary (Ns) to the number of turns in the

primary (Np) as follows:

Induction coils

Faraday's ring transformer

The first type of transformer to see wide use was the induction coil,

invented by Rev. Nicholas Callan of Maynooth College, Ireland in 1836. He

was one of the first researchers to realize that the more turns the

secondary winding has in relation to the primary winding, the larger is the

increase in EMF. Induction coils evolved from scientists' and inventors'

efforts to get higher voltages from batteries. Since batteries

produce direct current (DC) rather than alternating current (AC), induction

coils relied upon vibrating electrical contacts that regularly interrupted the

current in the primary to create the flux changes necessary for induction.

Between the 1830s and the 1870s, efforts to build better induction coils,

mostly by trial and error, slowly revealed the basic principles of

transformers.

By the 1870s, efficient generators that produced alternating

current (alternators) were available, and it was found that alternating

current could power an induction coil directly, without an interrupter. In

1876, Russian engineer Pavel Yablochkov invented a lighting system

based on a set of induction coils where the primary windings were

connected to a source of alternating current and the secondary windings

could be connected to several "electric candles" (arc lamps) of his own

design.The coils Yablochkov employed functioned essentially as

transformers.

In 1878, the Ganz Company in Hungary began manufacturing equipment

for electric lighting and, by 1883, had installed over fifty systems

in Austria-Hungary. Their systems used alternating current exclusively and

included those comprising both arc and incandescent lamps, along

with generators and other equipment.

Lucien Gaulard and John Dixon Gibbs first exhibited a device with an open

iron core called a "secondary generator" in London in 1882, then sold the

idea to theWestinghouse company in the United States.They also

exhibited the invention in Turin, Italy in 1884, where it was adopted for an

electric lighting system. However, the efficiency of their open-core bipolar

apparatus remained very low.

Induction coils with open magnetic circuits are inefficient for transfer of

power to loads. Until about 1880, the paradigm for AC power transmission

from a high voltage supply to a low voltage load was a series circuit.

Open-core transformers with a ratio near 1:1 were connected with their

primaries in series to allow use of a high voltage for transmission while

presenting a low voltage to the lamps. The inherent flaw in this method

was that turning off a single lamp affected the voltage supplied to all

others on the same circuit. Many adjustable transformer designs were

introduced to compensate for this problematic characteristic of the series

circuit, including those employing methods of adjusting the core or

bypassing the magnetic flux around part of a coil.[11]

Efficient, practical transformer designs did not appear until the 1880s, but

within a decade the transformer would be instrumental in the "War of

Currents", and in seeing AC distribution systems triumph over their DC

counterparts, a position in which they have remained dominant ever

since.

Basic principles

The transformer is based on two principles: first, that an electric current can produce a magnetic field (electromagnetism), and, second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.

Current passing through the primary coil creates a magnetic field. The primary and secondary coils are wrapped around a core of very high magnetic permeability, such as iron, so that most of the magnetic flux passes through both the primary and secondary coils.

Induction law

The voltage induced across the secondary coil may be calculated

from Faraday's law of induction, which states that:

where Vs is the instantaneous voltage, Ns is the number of turns in the

secondary coil and Φ is the magnetic flux through one turn of the coil. If

the turns of the coil are oriented perpendicular to the magnetic field lines,

the flux is the product of the magnetic flux density B and the

area A through which it cuts. The area is constant, being equal to the

cross-sectional area of the transformer core, whereas the magnetic field

varies with time according to the excitation of the primary. Since the

same magnetic flux passes through both the primary and secondary coils

in an ideal transformer, the instantaneous voltage across the primary

winding equals

Taking the ratio of the two equations for Vs and Vp gives the basic

equation for stepping up or stepping down the voltage

Np/Ns is known as the turns ratio, and is the primary functional

characteristic of any transformer. In the case of step-up transformers, this

may sometimes be stated as the reciprocal, Ns/Np. Turns ratio is commonly

expressed as an irreducible fraction or ratio: for example, a transformer

with primary and secondary windings of, respectively, 100 and 150 turns

is said to have a turns ratio of 2:3 rather than 0.667 or 100:150.

Detailed operation

The simplified description above neglects several practical factors, in

particular the primary current required to establish a magnetic field in the

core, and the contribution to the field due to current in the secondary

circuit.

Models of an ideal transformer typically assume a core of

negligible reluctance with two windings of zero resistance.When a voltage

is applied to the primary winding, a small current flows,

driving flux around themagnetic circuit of the core. The current required

to create the flux is termed the magnetizing current; since the ideal core

has been assumed to have near-zero reluctance, the magnetizing current

is negligible, although still required to create the magnetic field.

The changing magnetic field induces an electromotive force (EMF) across

each winding.Since the ideal windings have no impedance, they have no

associated voltage drop, and so the voltages VP and VSmeasured at the

terminals of the transformer, are equal to the corresponding EMFs. The

primary EMF, acting as it does in opposition to the primary voltage, is

sometimes termed the "back EMF".This is due toLenz's law which states

that the induction of EMF would always be such that it will oppose

development of any such change in magnetic field..

Energy losses

An ideal transformer would have no energy losses, and would be 100%

efficient. In practical transformers energy is dissipated in the windings,

core, and surrounding structures. Larger transformers are generally more

efficient, and those rated for electricity distribution usually perform better

than 98%.

Experimental transformers using superconducting windings achieve

efficiencies of 99.85%.The increase in efficiency can save considerable

energy, and hence money, in a large heavily-loaded transformer; the

trade-off is in the additional initial and running cost of the

superconducting design.

Losses in transformers (excluding associated circuitry) vary with load

current, and may be expressed as "no-load" or "full-load" loss.

Winding resistance dominates load losses, whereas hysteresis and eddy

currents losses contribute to over 99% of the no-load loss. The no-load

loss can be significant, so that even an idle transformer constitutes a

drain on the electrical supply and a running cost; designing transformers

for lower loss requires a larger core, good-quality silicon steel, or

even amorphous steel, for the core, and thicker wire, increasing initial

cost, so that there is a trade-off between initial cost and running cost.

(Also see energy efficient transformer).

Equivalent circuit

The physical limitations of the practical transformer may be brought

together as an equivalent circuit model (shown below) built around an

ideal lossless transformer. Power loss in the windings is current-dependent

and is represented as in-series resistances Rp and Rs. Flux leakage results

in a fraction of the applied voltage dropped without contributing to the

mutual coupling, and thus can be modeled as reactances of each leakage

inductance Xp and Xs in series with the perfectly coupled region.

Autotransformer

In an autotransformer portions of the same winding act as both

the primary and secondary. The winding has at least three taps where

electrical connections are made. An autotransformer can be smaller,

lighter and cheaper than a standard dual-winding transformer however

the autotransformer does not provide electrical isolation.

Autotransformers are often used to step up or down between voltages in

the 110-117-120 volt range and voltages in the 220-230-240 volt range,

e.g., to output either 110 or 120V (with taps) from 230V input, allowing

equipment from a 100 or 120V region to be used in a 230V region.

A variable autotransformer is made by exposing part of the winding coils

and making the secondary connection through a sliding brush, giving a

variable turns ratio.Such a device is often referred to by the trademark

name Variac.

Polyphase transformers.

Three-phase step-down transformer mounted between two utility poles.For three-phase supplies, a bank of three individual single-phase transformers can be used, or all three phases can be incorporated as a single three-phase transformer. In this case, the magnetic circuits are connected together, the core thus containing a three-phase flow of flux.A number of winding configurations are possible, giving rise to different attributes a phase shifts

Leakage transformers A leakage transformer, also called a stray-field transformer, has a significantly higher leakage inductance than other transformers, sometimes increased by a magnetic bypass or shunt in its core between primary and secondary, which is sometimes adjustable with a set screw. This provides a transformer with an inherent current limitation due to the loose coupling between its primary and the secondary windings. The output and input currents are low enough to prevent thermal overload under all load conditions—even if the secondary is shorted.

Applications

A major application of transformers is to increase voltage

before transmitting electrical energy over long distances through wires.

Wires have resistance and so dissipate electrical energy at a rate

proportional to the square of the current through the wire. By

transforming electrical power to a high-voltage (and therefore low-

current) form for transmission and back again afterward, transformers

enable economical transmission of power over long distances.

Consequently, transformers have shaped the electricity supply industry,

permitting generation to be located remotely from points of demand. All

but a tiny fraction of the world's electrical power has passed through a

series of transformers by the time it reaches the consumer

Transformers are also used extensively in electronic products to step

down the supply voltage to a level suitable for the low voltage circuits

they contain. The transformer also electrically isolates the end user from

contact with the supply voltage.

Signal and audio transformers are used to couple stages of amplifiers and

to match devices such as microphones and record players to the input of

amplifiers. Audio transformers allowed telephone circuits to carry on

a two-way conversation over a single pair of wires. A balun transformer

converts a signal that is referenced to ground to a signal that

has balanced voltages to ground, such as between external cables and

internal circuits.

Uninterrupted Power Supply

An uninterruptible power supply, also uninterruptible power

source, UPS or battery/flywheel backup, is an electrical apparatus that

provides emergency power to a load when the input power source,

typically the utility mains, fails. A UPS differs from an auxiliary

or emergency power system orstandby generator in that it will provide

instantaneous or near-instantaneous protection from input power

interruptions by means of one or more attachedbatteries and associated

electronic circuitry for low power users, and or by means of diesel

generators and flywheels for high power users. The on-battery runtime of

most uninterruptible power sources is relatively short—5–15 minutes

being typical for smaller units—but sufficient to allow time to bring an

auxiliary power source on line, or to properly shut down the protected

equipment.While not limited to protecting any particular type of

equipment, a UPS is typically used to protect computers, data

centers, telecommunicationequipment or other electrical equipment

where an unexpected power disruption could cause injuries, fatalities,

serious business disruption or data loss. UPS units range in size from units

designed to protect a single computer without a video monitor (around

200 VA rating) to large units powering entire data centers, buildings, or

even cities.

Applications

N+1

In large business environments where reliability is of great importance, a

single huge UPS can also be a single point of failure that can disrupt many

other systems. To provide greater reliability, multiple smaller UPS

modules and batteries can be integrated together to provide redundant

power protection equivalent to one very large UPS. "N+1" means that if

the load can be supplied by N modules, the installation will contain N+1

modules. In this way, failure of one module will not impact system

operation.

Multiple redundancy

Many computer servers offer the option of redundant power supplies, so

that in the event of one power supply failing, one or more other power

supplies are able to power the load. This is a critical point – each power

supply must be able to power the entire server by itself.

Redundancy is further enhanced by plugging each power supply into a

different circuit (i.e. to a different circuit breaker).

Redundant protection can be extended further yet by connecting each

power supply to its own UPS. This provides double protection from both a

power supply failure and a UPS failure, so that continued operation is

assured. This configuration is also referred to as 2N redundancy. If the

budget does not allow for two identical UPS units then it is common

practice to plug one power supply into mains power and the other into the

UPS.

Outdoor use

When a UPS system is placed outdoors, it should have some specific

features that guarantee that it can tolerate weather with a 'minimal to

none' effect on performance. Factors such as temperature, humidity, rain,

and snow among others should be considered by the manufacturer when

designing an outdoor UPS system. Operating temperature ranges for

outdoor UPS systems could be around −40 °C to +55 °C.

Outdoor UPS systems can be pole, ground (pedestal), or host mounted.

Outdoor environment could mean extreme cold, in which case the outdoor

UPS system should include a battery heater mat, or extreme heat, in

which case the outdoor UPS system should include a fan system or an air

conditioning system.

Internal systems

UPS systems can be designed to be placed inside a computer chassis.

There are two types of internal UPS. The first type is a miniaturized

regular UPS that is made small enough to fit into a 5.25-inch CD-ROM slot

bay of a regular computer chassis. The other type are re-engineered

switching power supplies that utilize dual power sources of AC and/or DC

as power inputs and have an AC/DC built-in switching management

control units.

Coaxial cable

Coaxial cable, or coax, is an electrical cable with an inner conductor

surrounded by a flexible, tubular insulating layer, surrounded by a tubular

conducting shield. The term coaxial comes from the inner conductor and

the outer shield sharing the same geometric axis. Coaxial cable was

invented by English engineer and mathematician Oliver Heaviside, who

patented the design in 1880.

Coaxial cable is used as a transmission line for radio frequency signals. Its

applications include feedlines connecting radio

transmitters andreceivers with their antennas, computer network

(Internet) connections, and distributing cable television signals. One

advantage of coax over other types of radio transmission line is that in an

ideal coaxial cable the electromagnetic field carrying the signal exists only

in the space between the inner and outer conductors. This allows coaxial

cable runs to be installed next to metal objects such as gutters without

the power losses that occur in other types of transmission lines. Coaxial

cable also provides protection of the signal from externalelectromagnetic

interference.

Coaxial cable differs from other shielded cable used for carrying lower

frequency signals, such as audio signals, in that the dimensions of the

cable are controlled to give a precise, constant conductor spacing, which

is needed for it to function efficiently as a radio frequencytransmission

line.

General Description

Coaxial cable conducts electrical power using an inner conductor (usually

a flexible solid or stranded copper wire) surrounded by an insulating layer

and all enclosed by a shield layer, typically a woven metallic braid; the

cable is often protected by an outer insulating jacket. Normally, the shield

is kept at ground potential and a voltage is applied to the center

conductor to carry electrical power. The advantage of coaxial design is

that the electric and magnetic fields are confined to the dielectric with

little leakage outside the shield. Conversely, electric and magnetic fields

outside the cable are largely kept from causing interference to signals

inside the cable. This property makes coaxial cable a good choice for

carrying weak signals that cannot tolerate interference from the

environment or for higher power signals that must not be allowed to

radiate or couple into adjacent structures or circuits.

Common applications of coaxial cable include video and CATV distribution,

RF and microwave transmission, and computer and instrumentation data

connections.

The characteristic impedance of the cable (Z0) is determined by

the dielectric constant of the inner insulator and the radiuses of the inner

and outer conductors. A controlled cable characteristic impedance is

important because the source and load impedance should be matched to

ensure maximum power transfer and minimum Standing Wave Ratio.

Other important properties of coaxial cable include attenuation as a

function of frequency, power and voltage handling capability, and shield

quality.

Circuit Breaker

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage

Operation

All circuit breakers have common features in their operation, although

details vary substantially depending on the voltage class, current rating

and type of the circuit breaker.

The circuit breaker must detect a fault condition; in low-voltage circuit

breakers this is usually done within the breaker enclosure. Circuit

breakers for large currents or high voltages are usually arranged with pilot

devices to sense a fault current and to operate the trip opening

mechanism. The trip solenoid that releases the latch is usually energized

by a separate battery, although some high-voltage circuit breakers are

self-contained with current transformers, protection relays, and an

internal control power source.

Once a fault is detected, contacts within the circuit breaker must open to

interrupt the circuit; some mechanically-stored energy (using something

such as springs or compressed air) contained within the breaker is used to

separate the contacts, although some of the energy required may be

obtained from the fault current itself. Small circuit breakers may be

manually operated; larger units have solenoids to trip the mechanism, and

electric motors to restore energy to the springs.

The circuit breaker contacts must carry the load current without excessive

heating, and must also withstand the heat of the arc produced when

interrupting (opening) the circuit. Contacts are made of copper or copper

alloys, silver alloys, and other highly conductive materials. Service life of

the contacts is limited by the erosion of contact material due to arcing

while interrupting the current. Miniature and molded case circuit breakers

are usually discarded when the contacts have worn, but power circuit

breakers and high-voltage circuit breakers have replaceable contacts.

When a current is interrupted, an arc is generated. This arc must be

contained, cooled, and extinguished in a controlled way, so that the gap

between the contacts can again withstand the voltage in the circuit.

Different circuit breakers use vacuum, air, insulating gas, or oil as the

medium in which the arc forms. Different techniques are used to

extinguish the arc including:

Lengthening / deflection of the arc

Intensive cooling (in jet chambers)

Division into partial arcs

Zero point quenching (Contacts open at the zero current time crossing of

the AC waveform, effectively breaking no load current at the time of

opening. The zero crossing occurs at twice the line frequency i.e. 100

times per second for 50Hz and 120 times per second for 60Hz AC)

Arc interruption

Miniature low-voltage circuit breakers use air alone to extinguish the arc.

Larger ratings will have metal plates or non-metallic arc chutes to divide

and cool the arc. Magnetic blowout coils or permanent magnetsdeflect the

arc into the arc chute.

In larger ratings, oil circuit breakers rely upon vaporization of some of the

oil to blast a jet of oil through the arc.Gas (usually sulfur hexafluoride)

circuit breakers sometimes stretch the arc using a magnetic field, and

then rely upon the dielectric strength of the sulfur hexafluoride (SF6) to

quench the stretched arc.Vacuum circuit breakers have minimal arcing (as

there is nothing to ionize other than the contact material), so the arc

quenches when it is stretched a very small amount (<2–3 mm). Vacuum

circuit breakers are frequently used in modern medium-voltage

switchgear to 35,000 volts.

Air circuit breakers may use compressed air to blow out the arc, or

alternatively, the contacts are rapidly swung into a small sealed chamber,

the escaping of the displaced air thus blowing out the arc.

Circuit breakers are usually able to terminate all current very quickly:

typically the arc is extinguished between 30 ms and 150 ms after the

mechanism has been tripped, depending upon age and construction of the

device.

Standard current ratings

Type

Instantaneous tripping current

B above 3 In up to and including 5 In

C above 5 In up to and including 10 In

D above 10 In up to and including 20 In

K above 8 In up to and including 12 In

For the protection of loads that cause frequent short duration

(approximately 400 ms to 2 s) current peaks in normal operation.

Z

above 2 In up to and including 3 In for periods in the order of tens of seconds.

For the protection of loads such as semiconductor devices or

measuring circuits using current transformers.

High-voltage circit breakers

Electrical power transmission networks are protected and controlled by

high-voltage breakers. The definition of high voltagevaries but in power

transmission work is usually thought to be 72.5 kV or higher, according to

a recent definition by theInternational Electrotechnical Commission (IEC).

High-voltage breakers are nearly always solenoid-operated, with current

sensing protective relays operated through current transformers.

In substations the protective relay scheme can be complex, protecting

equipment and buses from various types of overload or ground/earth

fault.

High-voltage breakers are broadly classified by the medium used to

extinguish the arc.

Bulk oil

Minimum oil

Air blast

Vacuum

SF6

Some of the manufacturers are ABB, GE (General Electric) , Tavrida

Electric, Alstom, Mitsubishi Electric, Pennsylvania

Breaker, Siemens, Toshiba, Končar HVS, BHEL, CGL, Square D (Schneider

Electric).

Due to environmental and cost concerns over insulating oil spills, most

new breakers use SF6 gas to quench the arc.Circuit breakers can be

classified as live tank, where the enclosure that contains the breaking

mechanism is at line potential, ordead tank with the enclosure at earth

potential. High-voltage AC circuit breakers are routinely available with

ratings up to 765 kV. 1200KV breakers are likely to come into market very

soonHigh-voltage circuit breakers used on transmission systems may be

arranged to allow a single pole of a three-phase line to trip, instead of

tripping all three poles; for some classes of faults this improves the

system stability and availability.

Sulfur hexafluoride (SF6) high-voltage circuit-breakers

A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur

hexafluoride gas to quench the arc. They are most often used for

transmission-level voltages and may be incorporated into compact gas-

insulated switchgear. In cold climates, supplemental heating or de-rating

of the circuit breakers may be required due to liquefaction of the SF6 gas.

Relays

A relay is an electrically operated switch. Many relays use

an electromagnet to operate a switching mechanism mechanically, but

other operating principles are also used. Relays are used where it is

necessary to control a circuit by a low-power signal (with complete

electrical isolation between control and controlled circuits), or where

several circuits must be controlled by one signal. The first relays were

used in long distance telegraph circuits, repeating the signal coming in

from one circuit and re-transmitting it to another. Relays were used

extensively in telephone exchanges and early computers to perform

logical operations.

A type of relay that can handle the high power required to directly control

an electric motor is called a contactor. Solid-state relays control power

circuits with no moving parts, instead using a semiconductor device to

perform switching. Relays with calibrated operating characteristics and

sometimes multiple operating coils are used to protect electrical circuits

from overload or faults; in modern electric power systems these functions

are performed by digital instruments still called "protective relays".

Simple electromechanical relay

A simple electromagnetic relay consists of a coil of wire surrounding a soft

iron core, an iron yoke which provides a low reluctance path for magnetic

flux, a movable ironarmature, and one or more sets of contacts (there are

two in the relay pictured). The armature is hinged to the yoke and

mechanically linked to one or more sets of moving contacts. It is held in

place by a spring so that when the relay is de-energized there is an air

gap in the magnetic circuit. In this condition, one of the two sets of

contacts in the relay pictured is closed, and the other set is open. Other

relays may have more or fewer sets of contacts depending on their

function. The relay in the picture also has a wire connecting the armature

to the yoke. This ensures continuity of the circuit between the moving

contacts on the armature, and the circuit track on the printed circuit

board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates

a magnetic field that attracts the armature, and the consequent

movement of the movable contact(s) either makes or breaks (depending

upon construction) a connection with a fixed contact. If the set of contacts

was closed when the relay was de-energized, then the movement opens

the contacts and breaks the connection, and vice versa if the contacts

were open. When the current to the coil is switched off, the armature is

returned by a force, approximately half as strong as the magnetic force,

to its relaxed position. Usually this force is provided by a spring, but

gravity is also used commonly in industrial motor starters. Most relays are

manufactured to operate quickly. In a low-voltage application this reduces

noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed

across the coil to dissipate the energy from the collapsing magnetic field

at deactivation, which would otherwise generate a voltage

spike dangerous to semiconductor circuit components. Some automotive

relays include a diode inside the relay case. Alternatively, a contact

protection network consisting of a capacitor and resistor in series

(snubber circuit) may absorb the surge. If the coil is designed to be

energized with alternating current (AC), a small copper "shading ring" can

be crimped to the end of the solenoid, creating a small out-of-phase

current which increases the minimum pull on the armature during the AC

cycle

A solid-state relay uses a thyristor or other solid-state switching device,

activated by the control signal, to switch the controlled load, instead of a

solenoid. An optocoupler (alight-emitting diode (LED) coupled with a photo

transistor) can be used to isolate control and controlled circuits.

Applications

Relays are used to and for:

Control a high-voltage circuit with a low-voltage signal, as in some

types of modems or audio amplifiers,

Control a high-current circuit with a low-current signal, as in

the starter solenoid of an automobile,

Detect and isolate faults on transmission and distribution lines by

opening and closing circuit breakers (protection relays),

Time delay functions. Relays can be modified to delay opening or delay

closing a set of contacts. A very short (a fraction of a second) delay

would use a copper disk between the armature and moving blade

assembly. Current flowing in the disk maintains magnetic field for a

short time, lengthening release time. For a slightly longer (up to a

minute) delay, adashpot is used. A dashpot is a piston filled with fluid

that is allowed to escape slowly. The time period can be varied by

increasing or decreasing the flow rate. For longer time periods, a

mechanical clockwork timer is installed.

Captive power plants 

Captive power plants are those power plants which operate

independent of wheeling to grid ! They are mostly meant by in-house

power generation for industry and not selling the power to grid of

electricty boards !

for example a DG set for a small industry is a captive power plantor a

large thermal plant for a cement industry or smelter is also a captive

power plant ! Captive power plants are associated with specific

industrial complexes, and their output is almost entirely consumed by

that industrial plant. 

Another term that may sometimes be synonymous is 'cogeneration' in

which the power plant produces multiple forms of energy (e.g., electric

power and steam), and where both are raw-materials for a related

industrial process. Probably the most classic example is that of a paper

mill. Boilers produce steam. The steam passes through a turbine that

spins a generator to produce electricity. Exhaust steam from the

turbine is then used as a source of heat to dry freshly-made paper

before is is finally condensed into water and returned to the boiler. The

boiler itself burns the bark that itself cannot be used to make paper

and would otherwise be a waste material. In addition, the process of

making pulp produces a chemical waste called "black liquor' that can

also be burned as a fuel in a boiler.

Captive power plants don't necessarily have to be islands that are

disconnected from 'the grid'. In fact, it is often the case that the

demand of the industrial process exceeds the capacity of the captive

plant, and power must be taken from the grid to make up the

difference. Also, there must be some provision to 'bootstrap' the

integrated process into operation - often this means relying on grid

power to start-up the plant following an outage. And it is possible that

there are times when the captive plant will produce more power than

can be consumed in the industrial process, and rather than throttle

back the excess is sold to the grid.

Captive Cogeneration Power Plant Project at IOCL Panipat

Larsen & Toubro Limited (L&T) has won a large scale turnkey contract valued at Rs. 1150 crore from Indian Oil Corporation Limited (IOCL) for setting up a captive cogeneration power plant in Panipat, Haryana. The

contract involves project management, engineering, procurement and construction of the power plant for IOCL's naphtha cracker project at its petrochemical complex in Panipat. 

The power plant comprises five gas turbines, five heat recovery steam generators, three steam turbines, two utility boilers and sophisticated control systems to ensure uninterrupted supply of power and steam to the naphtha cracker complex. To be commissioned within 32 months, the plant will have an installed capacity of 227 MW of power and over 800 tph of process steam. L&T bagged this prestigious order against keen competition from reputed EPC contractors on the strength of its track record in executing similar projects meeting stringent quality requirements. Engineers India Limited, who is the Project Management Consultant to IOCL, had invited offers under the International Competitive Bidding route. This is the second major contract won by L&T for IOCL's Panipat Naphtha Cracker Project. L&T and the Toyo consortium had earlier bagged the turnkey contract for naphtha cracker and associated units. L&T has participated in the setting up of several major power generations projects in India and abroad.