CHAPTER 1

ELECTRIC GRID

1.1 Introduction

The electric grid delivers electricity from points of generation to consumers, and the

electricity delivery network functions via two primary systems: the transmission system and

the distribution system. The transmission system delivers electricity from power plants to

distribution substations, while the distribution system delivers electricity from distribution

substations to consumers. The grid also encompasses myriads of local area networks that use

distributed energy resources to serve local loads and/or to meet specific application

requirements for remote power, village or district power, premium power, and critical loads

protection

Fig.1:- general layout of grid

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An electrical grid is an interconnected network for delivering electricity from suppliers to

consumers

When referring to the power industry, "grid" is a term used for an electricity network which

may support all or some of the following three distinct operations:

1. Electricity generation

2. Electric power transmission

3. Electricity distribution

The sense of grid is as a network, and should not be taken to imply a particular physical

layout, or breadth. "Grid" may be used to refer to an entire continent's electrical network, a

regional transmission network or may be used to describe a subnetwork such as a local

utility's transmission grid or distribution grid.

Electricity in a remote location might be provided by a simple distribution grid linking a

central generator to homes. The traditional paradigm for moving electricity around in

developed countries is more complex. Generating plants are usually located near a source of

water, and away from heavily populated areas. They are usually quite large in order to take

advantage of the Economies of scale. The electric power which is generated is stepped up to a

higher voltage—at which it connects to the transmission network. The transmission network

will move (wheel) the power long distances—often across state lines, and sometimes across

international boundaries—until it reaches its wholesale customer (usually the company that

owns the local distribution network). Upon arrival at the substation, the power will be stepped

down in voltage—from a transmission level voltage to a distribution level voltage. As it exits

the substation, it enters the distribution wiring. Finally, upon arrival at the service location,

the power is stepped down again from the distribution voltage to the required service

voltage(s).

This traditional centralized model along with its distinctions are breaking down with the

introduction of new technologies. For example, the characteristics of power generation can in

some new grids be entirely opposite of those listed above. Generation can occur at low levels

in dispersed locations, in highly populated areas, and not outside the distribution grids. Such

characteristics could be attractive for some locales, and can be implemented if the grid uses a

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combination of new design options such as net metering, electric cars as a temporary energy

source, or distributed generation.

Electrical power is a little bit like the air you breathe: You don't really think about it until it is

missing. Power is just "there," meeting your every need, constantly. It is only during a power

failure, when you walk into a dark room and instinctively hit the useless light switch, that you

realize how important power is in your daily life. You use it for heating, cooling, cooking,

refrigeration, light, sound, computation, entertainment... Without it, life can get somewhat

cumbersome.

Power travels from the power plant to your house through an amazing system called the

power distribution grid.

Fig.2:- general view of electrical network.

The grid is quite public -- if you live in a suburban or rural area, chances are it is right out in

the open for all to see. It is so public, in fact, that you probably don't even notice it anymore.

Your brain likely ignores all of the power lines because it has seen them so often. In this

article, we will look at all of the equipment that brings electrical power to your home. The

next time you look at the power grid, you will be able to really see it and understand what is

going on!

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1.2 Structure of grid

The structure, or "topology" of a grid can vary considerably. The physical layout is often

forced by what land is available and its geology. The logical topology can vary depending on

the constraints of budget, requirements for system reliability, and the load and generation

characteristics.

Classic North American electricity distribution grids were simple "radial" trees, sending

power from a source (red dot representing power generation or a substation) to delivery

points (blue dots representing homes, businesses, or other subnetworks).

The cheapest and simplest topology for a distribution or transmission grid is a radial

structure. This is a tree shape where power from a large supply radiates out into progressively

lower voltage lines until the destination homes and businesses are reached.

Most transmission grids require the reliability that more complex mesh networks provide. If

one were to imagine running redundant lines between each limb and branch of a tree that

could be turned in case any particular limb of the tree were severed, then this image

approximates how a mesh system operates. The expense of mesh topologies restrict their

application to transmission and medium voltage distribution grids. Redundancy allows line

failures to occur and power is simply rerouted while workmen repair the damaged and

deactivated line.

Other topologies used are looped systems found in Europe and tied ring networks.In cities

and town , the grid tends to follow the classic "radially fed" design. A substation receives its

power from the transmission network, the power is stepped down with a transformer and sent

to a bus from which feeders fan out in all directions across the countryside. These feeders

carry three-phase power, and tend to follow the major streets near the substation. As the

distance from the substation grows, the fanout continues as smaller laterals spread out to

cover areas missed by the feeders. This tree-like structure grows outward from the substation,

but for reliability reasons, usually contains at least one unused backup connection to a nearby

substation. This connection can be enabled in case of an emergency, so that a portion of a

substation's service territory can be alternatively fed by another substation.

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a. The Power Plant

Electrical power starts at the power plant. In almost all cases, the power plant consists of

a spinning electrical generator. Something has to spin that generator -- it might be a

water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most

cases, the thing spinning the generator is a steam turbine. The steam might be created by

burning coal, oil or natural gas. Or the steam may come from a nuclear reactor like this

one at the Shearon Harris nuclear power plant near Raleigh, North Carolina:

Fig.3:- Shearon Harris nuclear power plant near Raleigh, North Carolina:

No matter what it is that spins the generator, commercial electrical generators of any size

generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to

understand single-phase power first.

Single-phase power is what you have in your house. You generally talk about household

electrical service as single-phase, 120-volt AC service. If you use an oscilloscope and look at

the power found at a normal wall-plate outlet in your house, what you will find is that the

power at the wall plate looks like a sine wave, and that wave oscillates between -170 volts

and 170 volts (the peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120

volts). The rate of oscillation for the sine wave is 60 cycles per second. Oscillating power like

this is generally referred to as AC, or alternating current. The alternative to AC is DC, or

direct current. Batteries produce DC: A steady stream of electrons flows in one direction

only, from the negative to the positive terminal of the battery.

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The power plant, therefore, produces AC. On the next page, you'll learn about the AC power

produced at the power plant. Most notably, it is produced in three phases

The Power Plant: Three-phase Power

The power plant produces three different phases of AC power simultaneously, and the three

phases are offset 120 degrees from each other. There are four wires coming out of every

power plant: the three phases plus a neutral or ground common to all three. If you were to

look at the three phases on a graph, they would look like this relative to ground:

Fig.4:- 3-phase AC power

There is nothing magical about three-phase power. It is simply three single phases

synchronized and offset by 120 degrees.

Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are

120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any

given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in

industrial applications) and things like 3-phase welding equipment therefore have even power

output. Four phases would not significantly improve things but would add a fourth wire, so 3-

phase is the natural settling point.

And what about this "ground," as mentioned above? The power company essentially uses the

earth as one of the wires in the power system. The earth is a pretty good conductor and it is

huge, so it makes a good return path for electrons. (Car manufacturers do something similar;

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AC has at least three advantages over DC in a power distribution grid:

1. Large electrical generators happen to generate AC naturally, so conversion to DC

would involve an extra step.

2. Transformers must have alternating current to operate, and we will see that the power

distribution grid depends on transformers.

3. It is easy to convert AC to DC but expensive to convert DC to AC, so if you were

going to pick one or the other AC would be the better choice.

they use the metal body of the car as one of the wires in the car's electrical system and attach

the negative pole of the battery to the car's body.) "Ground" in the power distribution grid is

literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks,

groundwater, etc., of the earth.

b.Transmission Substation

The three-phase power leaves the generator and enters a transmission substation at the

power plant. This substation uses large transformers to convert the generator's voltage (which

is at the thousands of volts level) up to extremely high voltages for long-distance

transmission on the transmission grid.

Fig.5:- A typical substation at a power plant

You can see at the back several three-wire towers leaving the substation. Typical voltages for

long distance transmission are in the range of 155,000 to 765,000 volts in order to reduce line

losses. A typical maximum transmission distance is about 300 miles (483 km). High-voltage

transmission lines are quite obvious when you see them. They are normally made of huge

steel towers like this:

Fig.6:-High voltage transmission tower

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All power towers like this have three wires for the three phases. Many towers, like the ones

shown above, have extra wires running along the tops of the towers. These are ground wires

and are there primarily in an attempt to attract lightning.

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Fig.7:- The transmission lines entering the substation and passing through the switch tower

C. Distribution BusThe power goes from the transformer to the distribution bus:

Fig.8:- Distribution bus

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In this case, the bus distributes power to two separate sets of distribution lines at two different

voltages. The smaller transformers attached to the bus are stepping the power down to

standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in the other

direction at the higher voltage of the main transformer. The power leaves this substation in

two sets of three wires, each headed down the road in a different direction:

1.3 Geography of transmission networks

Transmission networks are more complex with redundant pathways. A wide area

synchronous grid or "interconnection" is a group of distribution areas all operating with

alternating current (AC) frequencies synchronized (so that peaks occur at the same time).

This allows transmission of AC power throughout the area, connecting a large number of

electricity generators and consumers and potentially enabling more efficient electricity

markets and redundant generation. Interconnection map shows Indian geography of

transmission network.

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The next time you are driving down the road, you can look at the power lines in a completely

different light. In the typical scene pictured on the right, the three wires at the top of the poles

are the three wires for the 3-phase power. The fourth wire lower on the poles is the ground

wire. In some cases there will be additional wires, typically phone or cable TV lines riding on

the same poles.

As mentioned above, this particular substation produces two different voltages. The wires at

the higher voltage need to be stepped down again, which will often happen at another

substation or in small transformers somewhere down the line. For example, you will often see

a large green box (perhaps 6 feet/1.8 meters on a side) near the entrance to a subdivision. It is

performing the step-down function for the subdivision.

Fig.9:- Indain Electric Transmission Network

Electricity generation and consumption must be balanced across the entire grid, because

energy is consumed almost immediately after it is produced. A large failure in one part of the

grid - unless quickly compensated for - can cause current to re-route itself to flow from the

remaining generators to consumers over transmission lines of insufficient capacity, causing

further failures. One downside to a widely connected grid is thus the possibility of cascading

failure and widespread power outage. A central authority is usually designated to facilitate

communication and develop protocols to maintain a stable grid. For example, the North

American Electric Reliability Corporation gained binding powers in the United States in

2006, and has advisory powers in the applicable parts of Canada and Mexico. The U.S.

government has also designated National Interest Electric Transmission Corridors, where it

believes transmission bottlenecks have developed.

High-voltage direct current lines or variable frequency transformers can be used to connect

two alternating current interconnection networks which are not synchronized with each other.

This provides the benefit of interconnection without the need to synchronize an even wider

area.

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1.4 Redundancy and defining "grid"

A town is only said to have achieved grid connection when it is connected to several

redundant sources, generally involving long-distance transmission.

This redundancy is limited. Existing national or regional grids simply provide the

interconnection of facilities to utilize whatever redundancy is available. The exact stage of

development at which the supply structure becomes a grid is arbitrary. Similarly, the term

national grid is something of an anachronism in many parts of the world, as transmission

cables now frequently cross national boundaries. The terms distribution grid for local

connections and transmission grid for long-distance transmissions are therefore preferred, but

national grid is often still used for the overall structure.

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CHAPTER 2

MODERN TRENDS IN GRID SYSTEM

2.1 Deregulation

The three components of a complete grid: generation, transmission, and distribution of

electrical power, can all be found in most large utilities. A utility can be completely self-

sufficient, but finds it advantageous to have the opportunity to buy and sell power to and

from neighboring utilities. This improves their reliability, and that of their neighbors. Utilities

are often awarded a "monopoly" status (at least at the distribution level) simply because it

doesn't make sense to have competing utilities installing their hardware in the same location

as another utility. The idea of a monopoly becomes less compelling as one considers the

generation of electrical power. Wildly varying costs for the production of electricity, and the

opportunity to encourage free market competition spurs many legislatures to move towards

deregulation of the electric utilities (also known as "liberalization" in some parts of the

world.) The idea of de-regulation usually involves the separation of the generation,

transmission, and distribution operations into separate financial entities. Generation assets in

particular can often be sold-off in piecemeal fashion to the highest bidders. With the aging

infrastructure present at many utilities, and the pressure to de-regulate, there are numerous

opportunities to re-engineer the system.

2.2 Demand response

Demand response is a grid management technique where retail or wholesale customers are

requested either electronically or manually to reduce their load. Currently, transmission grid

operators use demand response to request load reduction from major energy users such as

industrial plants.

2.3 Smart grid

Numerous efforts are underway to develop a "smart grid". In the U.S., the Energy Policy Act

of 2005 and Title XIII of the Energy Independence and Security Act of 2007. are providing

funding to encourage smart grid development. The hope is to enable utilities to better predict

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their needs, and in some cases involve consumers in some form of time-of-use based tariff.

Funds have also been allocated to develop more robust energy control technologies.

2.4 Micro grid

Decentralization of the power transmission distribution system is vital to the success and

reliability of this system. Currently the system is reliant upon relatively few generation

stations. This makes current systems susceptible to impact from failures not within said area.

Micro grids would have local power generation, and allow smaller grid areas to be separated

from the rest of the grid if a failure were to occur. Furthermore, micro grid systems could

help power each other if needed. Generation within a micro grid could be a downsized

industrial generator or several smaller systems such as photo-voltaic systems, or wind

generation. When combined with Smart Grid technology, electricity could be better

controlled and distributed, and more efficient.

2.5 Super grid

Various planned and proposed systems to dramatically increase transmission capacity are

known as super, or mega grids. The promised benefits include enabling the renewable energy

industry to sell electricity to distant markets, the ability to increase usage of intermittent

energy sources by balancing them across vast geological regions, and the removal of

congestion that prevents electricity markets from flourishing. Local opposition to siting new

lines and the significant cost of these projects are major obstacles to super grids

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CHAPTER 3

GRID FAILURE

3.1 Reasons of grid failure

During large magnetic storms, the intense currents flowing in the ionosphere induce currents

in the Earth's surface called GICs (ground induced currents). Some rocks carry current better

than others. Igneous rocks do not conduct electricity very well so the currents tend to take the

path of least resistance and flow through man-made conductors that are present on the surface

(like pipelines or cables). Regions of North America have significant amounts of igneous

rock and thus are particularly susceptible to the effects of GICs on man-made systems.

Currents flowing in the ocean contribute to GICs by entering along coastlines. GICs can enter

the complex grid of transmission lines that deliver power throughout the U.S. and other parts

of the world through their grounding points. The GICs are direct current (DC) flows. Under

extreme space weather conditions, these GICs can cause serious problems for the operation of

the power distribution networks by disrupting the operation of transformers that step voltages

up and down throughout the network.

Fig.10:- Burning of transformer

The transformer is not a power source. It functions like a lever to convert a small voltage

pushing a large electric current into a large voltage pushing a small electric current or vice

versa. The power in an electric circuit is equal to the voltage multiplied by the current. For a

perfect transformer, all the power that enters comes back out. If the transformer is not perfect,

a portion of the power that enters is converted to heat.

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The transformer is intended for use only with an alternating current while the current induced

in the power lines as a result of space weather disturbances is a direct current. The

transformer, which usually operates with 99% efficiency, begins to malfunction. Magnetic

flux ceases to be concentrated inside the iron core of the transformer and impinges on regions

that were not designed to withstand this. Power begins to be converted into heat. The

transformer moans and creaks loudly and overheats. Oil fires and melt-down of transformer

components can occur. This happens not just to one transformer but at the same time to all

affected transformers on the grid. Some transformers may burn up. Others experience

significantly shortened lifetimes following damage during magnetic storm events but don't

fail outright.

3.2 Electric breakdown

Fig:- 11 Electrical breakdown in an electric discharge showing the ribbon-like plasma filaments from a Tesla coil.

The term electrical breakdown has several similar but distinctly different meanings. The

term can apply to the failure of an electric circuit. Alternately, it may refer to a rapid

reduction in the resistance of an electrical insulator that can lead to a spark jumping around or

through the insulator. This may be a momentary event (as in an electrostatic discharge), or

may lead to a continuous arc discharge if protective devices fail to interrupt the current in a

high power circuit

3.3 Failure of electrical insulation

The second meaning of the term is more specifically a reference to the breakdown of the

insulation of an electrical wire or other electrical component. Such breakdown usually results

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in a short circuit or a blown fuse. This occurs at the breakdown voltage. Actual insulation

breakdown is more generally found in high-voltage applications, where it sometimes causes

the opening of a protective circuit breaker. Electrical breakdown is often associated with the

failure of solid or liquid insulating materials used inside high voltage transformers or

capacitors in the electricity distribution grid. Electrical breakdown can also occur across the

strings of insulators that suspend overhead power lines, within underground power cables, or

lines arcing to nearby branches of trees. Under sufficient electrical stress, electrical

breakdown can occur within solids, liquids, gases or vacuum. However, the specific

breakdown mechanisms are significantly different for each, particularly in different kinds of

dielectric medium. All this leads to catastrophic failure of the instruments.

3.4 Disruptive devices

A disruptive device is a device that has a dielectric, whereupon being stressed beyond its

dielectric strength, has an electrical breakdown. This results in the sudden transition of part of

the dielectric material from an insulating state to a highly conductive state. This transition is

characterized by the formation of an electric spark, and possibly an electric arc through the

material. If this occurs within a solid dielectric, physical and chemical changes along the path

of the discharge will cause permanent degradation and significant reduction in the material's

dielectric strength. A spark gap is a type of disruptive device that uses a gas or fluid dielectric

between spaced electrodes. Unlike solid dielectrics, liquid or gaseous dielectrics can usually

recover their full dielectric strength once current flow (through the plasma in the gap) has

been externally interrupted.

3.5 Mechanism

Electrical breakdown occurs within a gas (or mixture of gases, such as air) when the

dielectric strength of the gas(es) is exceeded. Regions of high electrical stress can cause

nearby gas to partially ionize and begin conducting. This is done deliberately in low pressure

discharges such as in fluorescent lights (see also Electrostatic Discharge) or in an

electrostatic precipitator.

Partial electrical breakdown of the air causes the "fresh air" smell of ozone during

thunderstorms or around high-voltage equipment. Although air is normally an excellent

insulator, when stressed by a sufficiently high voltage (an electric field strength of about 3 x

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106V/m ), air can begin to break down, becoming partially conductive. If the voltage is

sufficiently high, complete electrical breakdown of the air will culminate in an electrical

spark or arc that bridges the entire gap. While the small sparks generated by static electricity

may barely be audible, larger sparks are often accompanied by a loud snap or bang. Lightning

is an example of an immense spark that can be many miles long. The color of the spark

depends upon the gases that make up the gaseous media.

Fig.12:- Electric discharge showing the lightning-like plasma filaments from a Tesla coil

If a fuse or circuit breaker fails to interrupt the current through a spark in a power circuit,

current may continue, forming a very hot electric arc. The color of an arc depends primarily

upon the conductor materials (as they are vaporized and mix within the hot plasma in the

arc). Although sparks and arcs are usually undesirable, they can be useful in everyday

applications such as spark plugs for gasoline engines, electrical welding of metals, or for

metal melting in an electric arc furnace.

Voltage-Current relation

Before breakdown, there is a non-linear relation between voltage and current as shown in

figure. In region 1, there are free ions that can be accelerated by the field and induce a

current. These will be saturated after a certain voltage and give a constant current, region 2.

Region 3 and 4 are caused by ion avalanche as explained by the Townsend discharge

mechanism.

Corona breakdown

Partial breakdown of the air occurs as a corona discharge on high voltage conductors at

points with the highest electrical stress. As the dielectric strength of the material surrounding

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the conductor determines the maximum strength of the electric field the surrounding material

can tolerate before becoming conductive, conductors that consist of sharp points, or balls

with small radii, are more prone to causing dielectric breakdown. Corona is sometimes seen

as a bluish glow around high voltage wires and heard as a sizzling sound along high voltage

power lines. Corona also generates radio frequency noise that can also be heard as 'static' or

buzzing on radio receivers. Corona can also occur naturally at high points (such as church

spires, treetops, or ship masts) during thunderstorms as St. Elmo's Fire. Although corona

discharge is usually undesirable, until recently it was essential in the operation of

photocopiers (Xerography) and laser printers. Many modern copiers and laser printers now

charge the photoconductor drum with an electrically conductive roller, reducing undesirable

indoor ozone pollution. Additionally, lightning rods use corona discharge to create

conductive paths in the air that point towards the rod, deflecting potentially-damaging

lightning away from buildings and other structures.

Corona discharge ozone generators have been used for more than 30 years in the water

purification process. Ozone is a toxic gas, even more potent than chlorine. In a typical

drinking water treatment plant, the ozone gas is dissolved into the filtered water to kill

bacteria and viruses. Ozone also removes the bad odours and taste from the water. The main

advantage of ozone is that the overdose (residual) decomposes to gaseous oxygen well before

the water reaches the consumer. This is in contrast with chlorine which stays in the water and

can be tasted by the consumer.

Corona discharges are also used to modify the surface properties of many polymers. An

example is the corona treatment of plastic materials which allows paint or ink to adhere

properly.

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CHAPTER 4

POWER OUTAGE

4.1 Introduction

Fig.13:- Fault due to trees

Tree limbs create a short circuit in electrical lines during a storm. This will typically result in

a power outage to the area supplied by these lines.

A power outage (also known as a power cut, power failure, power loss, or blackout) is a

short- or long-term loss of the electric power to an area.

There are many causes of power failures in an electricity network. Examples of these causes

include, faults at power stations, damage to power lines, substations or other parts of the

distribution system, a short circuit, or the overloading of electricity mains.

Blackout.

Power outages are categorized into three different phenomena, relating to the duration and

effect of the outage:

A dropout is a momentary (usually less than one second) loss of power typically

caused by a temporary fault on a power line. Power is quickly (and sometimes

automatically) restored once the fault is cleared.

A brownout or sag is a drop in voltage in an electrical power supply. The term

brownout comes from the dimming experienced by lighting when the voltage sags.

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A blackout refers to the total loss of power to an area and is the most severe form of

power outage that can occur. Blackouts which result from or result in power stations

tripping are particularly difficult to recover from quickly. Outages may last from a

few hours to a few weeks depending on the nature of the blackout and the

configuration of the electrical network.

Dropout.

Power failures are particularly critical at sites where the environment and public safety are at

risk. Institutions such as hospitals, sewage treatment plants, mines, etc., will usually have

backup power sources, such as standby generators, which will automatically start up when

electrical power is lost. Other critical systems, such as telecommunications, are also required

to have emergency power. Telephone exchange rooms usually have arrays of lead-acid

batteries for backup and also a socket for connecting a generator during extended periods of

outage.

4.2Effects of power outages

Different types of electrical apparatus will react in different ways to a sag. Some devices will

be severely affected, while others may not be affected at all.

The heat output of any resistance device, such as an electric space heater will vary

with the true power consumption, which is proportional to the square of the applied

voltage. Therefore a significant loss of heat output will occur with a relatively small

reduction in voltage. Similarly, an incandescent lamp will dim due to the lower heat

emission from the filament. Generally speaking, no damage will occur but

functionality will be impaired.

Commutated electric motors, such as universal motors, whose mechanical power

output also varies with the square of the applied voltage, will run at reduced speed and

reduced torque. Depending on the motor design, no harm may occur. However, under

load, the motor will draw more current due to the reduced back-EMF developed at the

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lower armature speed. Unless the motor has ample cooling capacity, it may eventually

overheat and burn out.

An induction motor will draw more current to compensate for the decreased voltage,

which may lead to overheating and burnout.

An unregulated direct current linear power supply (consisting of a transformer,

rectifier and output filtering) will produce a lower output voltage for electronic

circuits, with more ripple, resulting in slower oscillation and frequency rates. In a

CRT television, this can be seen as the screen image shrinking in size and becoming

dim and fuzzy. The device will also attempt to draw more current in compensation,

potentially resulting in overheating.

A switching power supply may be affected, depending on the design. If the input voltage is

too low, it is possible for a switching power supply to malfunction and self-destruct

4.3 Protecting the grid from powere outages.

In power supply networks, the power generation and the electrical load (demand) must be

very close to equal every second to avoid overloading of network components, which can

severely damage them. In order to prevent this, parts of the system will automatically

disconnect themselves from the rest of the system, or shut themselves down to avoid damage.

This is analogous to the role of relays and fuses in households.

Under certain conditions, a network component shutting down can cause current fluctuations

in neighboring segments of the network, though this is unlikely, leading to a cascading failure

of a larger section of the network. This may range from a building, to a block, to an entire

city,to an entire electrical grid

Modern power systems are designed to be resistant to this sort of cascading failure, but it may

be unavoidable (see below). Moreover, since there is no short-term economic benefit to

preventing rare large-scale failures, some observers have expressed concern that there is a

tendency to erode the resilience of the network over time, which is only corrected after a

major failure occurs. It has been claimed that reducing the likelihood of small outages only

increases the likelihood of larger ones. In that case, the short-term economic benefit of

keeping the individual customer happy increases the likelihood of large-scale blackouts

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4.4 Mitigation of power outage frequency

The effects of trying to mitigate cascading failures near the critical point in an economically

feasible fashion are often shown to not be beneficial and often even detrimental. Four

mitigation methods have been tested using the OPA blackout model

Increase critical number of failures causing cascading blackouts - Shown to decrease

the frequency of smaller blackouts but increase that of larger blackouts.

Increase individual power line max load – Shown to increase the frequency of smaller

blackouts and decrease that of larger blackouts.

Combination of increasing critical number and max load of lines – Shown to have no

significant effect on either size of blackout. The resulting minor reduction in the

frequency of blackouts is projected to not be worth the cost of the implementation.

Increase the excess power available to the grid – Shown to decrease the frequency of smaller

blackouts but increase that of larger blackouts

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CHAPTER 5

FAILURE PROTECTION AND RESTORATION OF GRID

5.1 Grid input

At the generating plants the energy is produced at a relatively low voltage between about

2.3 kV and 30 kV, depending on the size of the unit. The generator terminal voltage is then

stepped up by the power station transformer to a higher voltage (115 kV to 765 kV AC,

varying by country) for transmission over long distances.

5.2 Losses

Transmitting electricity at high voltage reduces the fraction of energy lost to resistance. For a

given amount of power, a higher voltage reduces the current and thus the resistive losses in

the conductor. For example, raising the voltage by a factor of 10 reduces the current by a

corresponding factor of 10 and therefore the I2r losses by a factor of 100, provided the same

sized conductors are used in both cases. Even if the conductor size (cross-sectional area) is

reduced 10-fold to match the lower current the I2r losses are still reduced 10-fold. Long

distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. At

extremely high voltages, more than 2 MV between conductor and ground, corona discharge

losses are so large that they can offset the lower resistance loss in the line conductors.

Transmission and distribution losses in the USA were estimated at 7.2% in 1995 . In general,

losses are estimated from the discrepancy between energy produced (as reported by power

plants) and energy sold to end customers; the difference between what is produced and what

is consumed constitute transmission and distribution losses.

As of 1980, the longest cost-effective distance for electricity was 7,000 km (4,300 mi),

although all present transmission lines are considerably shorter.

In an alternating current circuit, the inductance and capacitance of the phase conductors can

be significant. The currents that flow in these components of the circuit impedance constitute

reactive power, which transmits no energy to the load. Reactive current flow causes extra

losses in the transmission circuit. The ratio of real power (transmitted to the load) to apparent

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power is the power factor. As reactive current increases, the reactive power increases and the

power factor decreases. For systems with low power factors, losses are higher than for

systems with high power factors. Utilities add capacitor banks and other components (such as

phase-shifting transformers; static VAR compensators; physical transposition of the phase

conductors; and flexible AC transmission systems, FACTS) throughout the system to control

reactive power flow for reduction of losses and stabilization of system voltage.

5.3 Safety devices

a. Fuses

Fig.14:- A miniature time delay fuse

In electronics and electrical engineering a fuse (from the Latin "fusus" meaning to melt) is a

type of sacrificial overcurrent protection device. Its essential component is a metal wire or

strip that melts when too much current flows, which interrupts the circuit in which it is

connected. Short circuit, overload or device failure is often the reason for excessive current.

A fuse interrupts excessive current (blows) so that further damage by overheating or fire is

prevented. Wiring regulations often define a maximum fuse current rating for particular

circuits. Overcurrent protection devices are essential in electrical systems to limit threats to

human life and property damage. Fuses are selected to allow passage of normal current and of

excessive current only for short periods.

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A fuse was patented by Thomas Edison in 1890 as part of his successful electric distribution

system

Fig.15:- 200 A Industrial fuse. 80 kA breaking capacity.

Operation

A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the

circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by

a non-conducting and non-combustible housing. The fuse is arranged in series to carry all the

current passing through the protected circuit. The resistance of the element generates heat due

to the current flow. The size and construction of the element is (empirically) determined so

that the heat produced for a normal current does not cause the element to attain a high

temperature. If too high a current flows, the element rises to a higher temperature and either

directly melts, or else melts a soldered joint within the fuse, opening the circuit.

When the metal conductor parts, an electric arc forms between the un-melted ends of the

element. The arc grows in length until the voltage required to sustain the arc is higher than

the available voltage in the circuit, terminating current flow. In alternating current circuits the

current naturally reverses direction on each cycle, greatly enhancing the speed of fuse

interruption. In the case of a current-limiting fuse, the arc voltage builds up quickly enough to

essentially stop the fault current before the first peak of the AC waveform. This effect

significantly limits damage to downstream protected devices.

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The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and

predictable characteristics. The fuse ideally would carry its rated current indefinitely, and

melt quickly on a small excess. The element must not be damaged by minor harmless surges

of current, and must not oxidize or change its behavior after possibly years of service.

The fuse elements may be shaped to increase heating effect. In large fuses, current may be

divided between multiple strips of metal. A dual-element fuse may contain a metal strip that

melts instantly on a short-circuit, and also contain a low-melting solder joint that responds to

long-term overload of low values compared to a short-circuit. Fuse elements may be

supported by steel or nichrome wires, so that no strain is placed on the element, but a spring

may be included to increase the speed of parting of the element fragments.

The fuse element may be surrounded by air, or by materials intended to speed the quenching

of the arc. Silica sand or non-conducting liquids may be used.

High voltage fuses

Fig. 16:- A set of pole-top fusible cutouts with one fuse blown, protecting a transformer- the white tube on the left is hanging down

Fuses are used on power systems up to 115,000 volts AC. High-voltage fuses are used to

protect instrument transformers used for electricity metering, or for small power transformers

where the expense of a circuit breaker is not warranted. For example, in distribution systems,

a power fuse may be used to protect a transformer serving 1-3 houses. A circuit breaker at

115 kV may cost up to five times as much as a set of power fuses, so the resulting saving can

be tens of thousands of dollars. Pole-mounted distribution transformers are nearly always

protected by a fusible cutout, which can have the fuse element replaced using live-line

maintenance tools.

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Large power fuses use fusible elements made of silver, copper or tin to provide stable and

predictable performance. High voltage expulsion fuses surround the fusible link with gas-

evolving substances, such as boric acid. When the fuse blows, heat from the arc causes the

boric acid to evolve large volumes of gases. The associated high pressure (often greater than

100 atmospheres) and cooling gases rapidly quench the resulting arc. The hot gases are then

explosively expelled out of the end(s) of the fuse. Such fuses can only be used outdoors.

Fig.17:- A 115 kV high-voltage fuse in a substation near a hydroelectric power plant

Older medium-voltage fuse for a 20 kV Network

b.Circuit breaker

Fig.18:- A 2 pole miniature 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

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made in varying sizes, from small devices that protect an individual household appliance up

to large switchgear designed to protect high voltage circuits feeding an entire city.

origin

An early form of circuit breaker was described by Edison in an 1879 patent application,

although his commercial power distribution system used fuses.[1] Its purpose was to protect

lighting circuit wiring from accidental short-circuits and overloads.

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 the circuit. Contacts are made

of copper or copper alloys, silver alloys, and other materials. Service life of the contacts is

limited by the erosion due to interrupting the arc. Miniature and molded case circuit breakers

are usually discarded when the contacts are worn, but power circuit breakers and high-voltage

circuit breakers have replaceable contacts.

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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 of the arc

Intensive cooling (in jet chambers)

Division into partial arcs

Zero point quenching

Connecting capacitors in parallel with contacts in DC circuits

Finally, once the fault condition has been cleared, the contacts must again be closed to restore

power to the interrupted circuit.

Types of circuit breaker

Fig.19:- Front panel of a 1250 A air circuit breaker.

Many different classifications of circuit breakers can be made, based on their features such as

voltage class, construction type, interrupting type, and structural features.

Low voltage circuit breakers

Low voltage (less than 1000 VAC) types are common in domestic, commercial and industrial

application, include:

MCB (Miniature Circuit Breaker)—rated current not more than 100 A. Trip characteristics

normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above

are in this category.

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MCCB (Molded Case Circuit Breaker)—rated current up to 1000 A. Thermal or thermal-

magnetic operation. Trip current may be adjustable in larger ratings.

Low voltage power circuit breakers can be mounted in multi-tiers in LV switchboards

or switchgear cabinets.

Magnetic circuit breaker

Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with

the current. Certain designs utilize electromagnetic forces in addition to those of the solenoid.

The circuit breaker contacts are held closed by a latch. As the current in the solenoid

increases beyond the rating of the circuit breaker, the solenoid's pull releases the latch which

then allows the contacts to open by spring action. Some types of magnetic breakers

incorporate a hydraulic time delay feature using a viscous fluid. The core is restrained by a

spring until the current exceeds the breaker rating. During an overload, the speed of the

solenoid motion is restricted by the fluid. The delay permits brief current surges beyond

normal running current for motor starting, energizing equipment, etc. Short circuit currents

provide sufficient solenoid force to release the latch regardless of core position thus

bypassing the delay feature. Ambient temperature affects the time delay but does not affect

the current rating of a magnetic breaker.

Thermal magnetic circuit breaker

Thermal magnetic circuit breakers, which are the type found in most distribution boards,

incorporate both techniques with the electromagnet responding instantaneously to large

surges in current (short circuits) and the bimetallic strip responding to less extreme but

longer-term over-current conditions

High-voltage circuit breakers

Fig.20:- 400 kV SF6 live tank circuit breakers

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Fig.21:- 115 kV bulk oil circuit breaker

Electrical power transmission networks are protected and controlled by high-voltage

breakers. The definition of high voltage varies but in power transmission work is usually

thought to be 72.5 kV or higher, according to a recent definition by the International

Electrotechnical Commission (IEC). High-voltage breakers are nearly always solenoid-

operated, with current sensing protective relays operated through current transformers. In

substations the protection relay scheme can be complex, protecting equipment and busses

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) , AREVA, Mitsubishi Electric,

Pennsylvania Breaker, Siemens, Toshiba, Končar HVS, BHEL and others.

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, or dead tank with the enclosure at earth potential. High-

voltage AC circuit breakers are routinely available with ratings up to 765 kV.

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High-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.

C. Lightning arrestor :

In order to protect the grid and transmission line from lightning a special kind of wire is

placed over them such that all the current may pass through these wires and protect the grid

from the lightning effect.

5.4 Types of protection

Generator sets – In a power plant, the protective relays are intended to prevent

damage to alternators or of the transformers in case of abnormal conditions of

operation, due to internal failures, as well as insulating failures or regulation

malfunctions. Such failures are unusual, so the protective relays have to operate very

rarely. If a protective relay fails to detect a fault, the damage to the alternator or to the

transformer may have important financial consequences for the repair or replacement

of equipment and the value of the energy that otherwise would have been sold.

High voltage transmission network – Protection on the transmission and distribution

serves two functions: Protection of plant and protection of the public (including

employees). At a basic level protection looks to disconnect equipment which

experience an overload or a connection to earth. Some items in substations such as

transformers may require additional protection based on temperature or gassing

among others.

Overload – Overload protection requires a current transformer which simply

measures the current in a circuit. If this current exceeds a pre-determined level, a

circuit breaker or fuse should operate.

Earth fault – Earth fault protection again requires current transformers and senses an

imbalance in a three-phase circuit. Normally a three-phase circuit is in balance, so if a

single (or multiple) phases are connected to earth an imbalance in current is detected.

If this imbalance exceeds a pre-determined value a circuit breaker should operate.

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Distance – Distance protection detects both voltage and current. A fault on a circuit

will generally create a sag in the voltage level. If this voltage falls below a pre-

determined level and the current is above a certain level the circuit breaker should

operate. This is useful on long lines where if a fault was experienced at the end of the

line the impedance of the line itself may inhibit the rise in current. Since a voltage sag

is required to trigger the protection the current level can actually be set below the

normal load on the line.

Back-up – At all times the objective of protection is to remove only the affected

portion of plant and nothing else. Sometimes this does not occur for various reasons

which can include:

o Mechanical failure of a circuit breaker to operate

o Incorrect protection setting

o Relay failures

A failure of primary protection will usually result in the operation of back-up

protection which will generally remove both the affected and unaffected items of

plant to remove the fault.

Low-voltage networks – The low voltage network generally relies upon fuses or low-

voltage circuit breakers to remove both overload and earth faults.

5.5 control and load balancing

To ensure safe and predictable operation the components of the transmission system are

controlled with generators, switches, circuit breakers and loads. The voltage, power,

frequency, load factor, and reliability capabilities of the transmission system are designed to

provide cost effective performance for the customers

The transmission system provides for base load and peak load capability, with safety and

fault tolerance margins. The peak load times vary by region largely due to the industry mix.

In very hot and very cold climates home air conditioning and heating loads have an effect on

the overall load. They are typically highest in the late afternoon in the hottest part of the year

and in mid-mornings and mid-evenings in the coldest part of the year. This makes the power

requirements vary by the season and the time of day. Distribution system designs always take

the base load and the peak load into consideration.

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The transmission system usually does not have a large buffering capability to match the loads

with the generation. Thus generation has to be kept matched to the load, to prevent

overloading failures of the generation equipment.

Multiple sources and loads can be connected to the transmission system and they must be controlled to provide orderly transfer of power. In centralized power generation, only local control of generation is necessary, and it involves synchronization of the generation units, to prevent large transients and overload conditions.

In distributed power generation the generators are geographically distributed and the process

to bring them online and offline must be carefully controlled. The load control signals can

either be sent on separate lines or on the power lines themselves. To load balance the voltage

and frequency can be used as a signaling mechanism.

In voltage signaling, the variation of voltage is used to increase generation. The power added

by any system increases as the line voltage decreases. This arrangement is stable in principle.

Voltage based regulation is complex to use in mesh networks, since the individual

components and setpoints would need to be reconfigured every time a new generator is added

to the mesh.

In frequency signaling, the generating units match the frequency of the power transmission

system. In droop speed control, if the frequency decreases, the power is increased. (The drop

in line frequency is an indication that the increased load is causing the generators to slow

down.)

5.6 Restoring power after power outage

Restoring power after a wide-area outage can be difficult, as power stations need to be

brought back on-line. Normally, this is done with the help of power from the rest of the grid.

In the total absence of grid power, a so-called black start needs to be performed to bootstrap

the power grid into operation. The means of doing so will depend greatly on local

circumstances and operational policies, but typically transmission utilities will establish

localized 'power islands' which are then progressively coupled together. To maintain supply

frequencies within tolerable limits during this process, demand must be reconnected at the

same pace that generation is restored, requiring close coordination between power stations,

transmission and distribution organizations.

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CHAPTER 6

PLANNING AND MANAGEMENT OF GRID

6.1 Load management

Load management is the process of balancing the supply of electricity on the network with

the electrical load by adjusting or controlling the load rather than the power station output.

This can be achieved by direct intervention of the utility in real time, by the use of frequency

sensitive relays triggering circuit breakers, or by time clocks, or by using special tariffs to

influence consumer behavior.

Electrical energy is a form of Energy that cannot be stored in bulk. It must be generated,

shipped to the point where it is needed, and immediately consumed. Consequently, for the

generation and distribution of electrical power, load management is a subject that is

continually on the minds of the electrical network operators (also known as Transmission

system operators). Sometimes the load on a system can approach the maximum generating

capacity or the rate at which the load is increasing can increase the rate at which generating

output can be increased, even though there is ultimately enough capacity. When this happens,

the network operators must either find additional supplies of energy or find ways to curtail

the load. If they are unsuccessful within the time allowed, the system will become unstable

and blackouts can occur.

The Load Management may involve sophisticated load analysis in which models are built to

describe the physical properties of the distribution network (i.e. topology, capacity, and other

characteristics of the lines), as well as the load behavior. The analysis may include scenarios

that account for weather forecasts, the predicted impact of proposed load-shed commands,

estimated time-to-repair for off-line equipment, and other factors.

Monitoring of the load and the effect a Load control program or Demand response price

event might have, is typically done in real-time by human operators, using a SCADA system.

If the actual outcome differs from the predicted outcome, the human can intervene to make

corrections, applying more or less load shed as necessary but automatic systems are

commonplace.

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The accuracy of the load forecast requires ongoing diligence in order to refine the

demographics, monitor growth patterns, and maintain knowledge of the amount of dis

patchable load.

Load Management might be achieved in the utility using any combination of tools and

programs including: construction and operation of new power plants (especially peak

generation units), participation in a power pool, demand side management programs (such as

operation of a load control system and customer programs to improve energy conservation),

as well as demand response programs. New technologies are always under development—

both by private industry and public entities

6.2 Grid connection

In electrical grids, a power system network integrates transmission grids, distribution grids,

distributed generators and loads that have connection points called busses. A bus in home

circuit breaker panels is much smaller than those used on the grid, where busbars can be 50

mm in diameter in electrical substations. Traditionally, these grid connections are

unidirectional point to multipoint links. In distributed generation grids, these connections are

bidirectional, and the reverse flow can raise safety and reliability concerns . Features in smart

grids are designed to manage these conditions.

A premises is generally said to have obtained grid connection when its service location

becomes powered by a live connection to its service transformer.

A power station is generally said to have achieved grid connection when it first supplies

power outside of its own boundaries. However, a town is only said to have achieved grid

connection when it is connected to several redundant sources, generally involving long-

distance transmission.

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Fig.22:- connection of electrical transformer at grid.

6.3 Use of the Reserve Service and Frequency Service in practice

An example illustrating how the Reserve Service and Frequency Service are used in order to

cope with intermittency/variability is given below:

1. Consider, if a 660 MW turbine generator set (the standard size of large steam turbine)

trips (large power stations usually consist of 2 or 4 sets each of 660 MW). This can

happen for all sorts of reasons: a coal crusher might break down, boiler tubes might

fail, an alternator might start to overheat, insulation might fail on the alternator. In the

event of certain failures, the generating set would automatically trip out and the grid

has suddenly loses 660 MW. On a typical day, this might be 1.3% of the total national

grid output. Due to the immediate increased load on the remaining generating sets,

grid frequency immediately starts to drop from the standard 50 Hz. (An alternative

scenario, leading to the same frequency drop, could be a sudden and unexpectedly

large surge in power demand as happens at the end of certain tv programmes, when

people all rush to switch on electric kettles etc)

2. As soon as this happens, the under frequency relays on Frequency Response

customers begin to trip off their load as the frequency falls, ultimately to shed total

load equal to 660 MW. These relays are set at a range of frequency between 48.5 and

49.5, so the 660 MW of generation that has been lost is not instantly matched by these

relays shedding 660 MW of load simultaneously but progressively as the frequency

37

drops, until exactly enough is shed to exactly match the remaining power station

capacity. This will then stabilise the frequency at its now lower level—perhaps

49.3 Hz. This all happens in less than a second. These Frequency Response

participants are only contracted to have their shed loads for up to 20 minutes.

3. At the same time, the NG Control Room issues start up signals to sufficient of its

Standing Reserve Service participants for the shortfall (in this case, 660 MW) which

by contract have to become available within 20 minutes. The NG control room is

monitoring the situation and if sufficient Standing Reserve capacity does not come on,

then it can order more until it has exactly matched what the Frequency Response

relays have shed. (These relays are monitored in real time by NGT's telemetry

systems)

4. Due to differing circumstances on the ground, different Standing Reserve participants

will have different start up times and reliabilities which again NG monitors using

telemetry. However, when sufficient Standing Reserve has become available, which

would be in less than 20 minutes, the Frequency Response loads (steel furnaces, cold

stores etc) are gradually and automatically re-connected by the relays. The original

NG Frequency Response relays are then re-armed by NG.

5. Up to an hour or so later, the output of the Standing Reserve diesels and gas turbines,

(which are nearly all in the hands of those not involved in commercial power

generation) will have been augmented, and then replaced with new levels of large gas

or coal fired power stations which together will have driven the frequency back to its

correct level close to 50 Hz. The diesels can then be stood down, ready for the next

emergency.

6. The replacement generation sources would have come from increased outputs from

other power stations on spinning reserve, resulting in increased output. At the same

time new levels of spinning reserve will have been created, which might have been

stations on hot standby/warming now switched to running. Increased levels of stations

on hot standby will also be called for.

The foregoing is a brief description of how the National Grid organises itself and the dispatch

of power stations to cope with sudden, unforeseen and dramatic changes in load or

generation.

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The point to note is that complicated as this may sound, this has been going on for many

years as the loads imposed on the grid, and supply of power from power stations is by itself

extremely intermittent already, simply due to the sudden and unpredictable failure of these

large 660 MW generating sets, or sometimes the entire power stations; and the sudden

changes in load which can happen at the end of a major TV program, or events such as the

last eclipse of the sun. These latter can cause surges of several GW which whilst larger in

magnitude than the sudden loss of 2 × 660 MW sets, are not instantaneous and so are not as

severe a shock to the national grid system.

It should be noted that however reliable a power station is, grid operators have to assume that

it can fail, and that it will fail, so its replacement must always be running and available.

The value of providing this service is considerable.

6.4 Voltage Control

There are a number of ways that voltage control is undertaken on the National Grid 400, 275,

132 kV system. This can be done by:

Over/under excitation of generators

Switching in/out of shunt reactors

Switching out of overhead line and underground cable circuits

Tap staggering of both supergrid and grid transformers

Under/over excitation of synchronous compensators

Declutching open cycle gas-turbines into the synchronous compensation mode

Static variable compensators

Manually-switched capacitor banks

Synchronous compensation of generators

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CHAPTER 7

CASE STUDIES

7.1 Grid failure in western india

Grid failure causes acute power crisis in western India

30 July 2002

VADODARA: The whole state of Gujarat was plunged into darkness on Tuesday evening

because of a cascade tripping in the entire western grid at around 8.15 pm. The states of

Maharashtra, Madhya Pradesh, Chattisgarh and Goa were also affected by the breakdown,

sources in the Gujarat Electricity Board here said. At the Sabarmati power station in

Ahmedabad, there was a loud blast caused by the tripping. The plant is run by the

Ahmedabad Electricity Company (AEC). The crisis plunged the entire state, including the

cities of Ahmedabad, Vadodara, Rajkot and Surat into darkness. Officials of the Gujarat

Electricity Board said that the problem was caused due to overdrawing of power by the states.

The officials said that power would be restored by first using the gas-based power stations.

The executive director of AEC Dipak Dalal said that the power sub-station in Vatva was

saved from the tripping and the engineers were now trying to take power from Vatva to

Sabarmati to start the auxillary systems. "Our priority will be to first supply power to V S

Hospital and Civil Hospital", he said. Meanwhile, minor incidents of stone throwing were

reported from the Dilli Chakla area of Ahmedabad on Tuesday evening as miscreants took

advantage of the cover of darkness. Police said that the stone throwing was contained as

additional forces were rushed to the spot. Police in Ahmedabad were on tenterhooks as the

power crisis could lead to a renewal of clashes in areas which are prone to riots.

7.2 grid failure in northern india

03 january 2010

Many parts of northern India, including Punjab and Haryana, plunged into darkness in the

wee hours on Saturday as the northern grid collapsed due to thick fog. The northern grid

tripped at around 3.02 am following a technical snag in transmission lines that reduced power

to zero at many sub stations, Power Grid CMD S K Chaturvedi said, adding that Delhi and

NCR were not affected as precautionary measures like cleaning of transmission lines were

taken in advance.

40

Besides, Punjab and Haryana, parts of Jammu and Kashmir and the Union Territory of

Chandigarh were also affected due to the grid failure.

Although restoration work was on, authorities said, it would take another three to four hours

for power supply to resume.

Power failure also threw train schedule out of gear in Punjab and Haryana and many trains

were stranded midway, stopping abruptly due to disruption in electricity supply.

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CHAPTER 8

ROLE OF EPRI

1.1 About EPRIThe Electric Power Research Institute, Inc. (EPRI) conducts research and

development relating to the generation, delivery and use of electricity for the benefit

of the public. An independent, nonprofit organization, EPRI brings together its

scientists and engineers as well as experts from academia and industry to help address

challenges in electricity, including reliability, efficiency, health, safety and the

environment. EPRI also provides technology, policy and economic analyses to drive

long-range research and development planning, and supports research in emerging

technologies. EPRI's members represent more than 90 percent of the electricity

generated and delivered in the United States, and international participation extends to

40 countries. EPRI's principal offices and laboratories are located in Palo Alto, Calif.;

Charlotte, N.C.; Knoxville, Tenn.; and Lenox, Mass.

8.2 Technology Strategy

The Technology Strategy is the guiding framework for EPRI's overall research and

development (R&D) portfolio. It encompasses the long-term visions and broad

societal goals defined by the Electricity Technology Roadmap; the mid- to long-term

targets for innovation identified via scenario planning and energy-economy modeling

activities; and the near- to mid-term technical and business objectives of

EPRI'smembers. The Office of Innovation is responsible for the continuous updating

of EPRI's Technology Strategy and, through the Technology Innovation program, for

funding the collaborative work required to achieve the mid- and long-term science

and technology objectives. The Research Advisory Committee (RAC) represents the

primary

membership sponsor of and advocate for the Technology Strategy and the strategic

component of EPRI's science and technology portfolio. In this context, the RAC

provides guidance to EPRI management and staff on emerging issues and

opportunities over a time horizon extending to 10 to 20 years.

42

EPRI's current strategic R&D portfolio reflects recent work addressing the potential

roles of the electric sector and electricity-based technologies in achieving substantial

reductions in greenhouse gas emissions by 2030. Findings, summarized in The Power

to Reduce CO2 Emissions: The Full Portfolio, are informing EPRI's ongoing effort to

initiate major demonstration projects addressing the smart grid, advanced coal

generation, energy efficiency and demand response, large-scale renewables, carbon

capture and storage, and large-scale energystorage. The Environment, Generation,

Nuclear, and Power Delivery & Utilization Sectors, with guidance from their advisory

structures, are responsible for planning and implementing the collaborative R&D

required to meet the near-term technical and business objectives of electricity industry

stakeholders.

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