FERRANTI EFFECT

A long transmission line can be considered to compose a considerably high amount of capacitance and inductance distributed across the entire length of the line. Ferranti Effect occurs when current drawn by the distributed capacitance of the line itself is greater than the current associated with the load at the receiving end of the line(during light or no load). This capacitor charging current leads to voltage drop across the line inductor of the transmission system which is in phase with the sending end voltages. This voltage drop keeps on increasing additively as we move towards the load end of the line and subsequently the receiving end voltage tends to get larger than applied voltage leading to the phenomena called Ferranti effect in power system. It is illustrated with the help of a phasor diagram below.
Thus both the capacitance and inductor effect of transmission line are equally responsible for this particular phenomena to occur, and hence Ferranti effect is negligible in case of a short transmission line as the inductor of such a line is practically considered to be nearing zero. In general for a 300 Km line operating at a frequency of 50 Hz, the no load receiving end voltage has been found to be 5% higher than the sending end voltage.
Now for analysis of Ferranti effect let us consider the phasor diagrams shown above.
Here, Vr is considered to be the reference phasor, represented by OA.

This is represented by the phasor OC.

Now in case of a long transmission line, it has been practically observed that the line electrical resistance is negligibly small compared to the line reactance, hence we can assume the length of the phasor Ic R = 0, we can consider the rise in the voltage is only due to OA - OC = reactive drop in the line.

Now if we consider c0 and L0 are the values of capacitance and inductor per km of the transmission line, where l is the length of the line.

Since, in case of a long transmission line, the capacitance is distributed throughout its length, the average current flowing is,

Thus the rise in voltage due to line inductor is given by,

From the above equation it is absolutely evident, that the rise in voltage at the receiving end is directly proportional to the square of the line length, and hence in case of a long transmission line it keeps increasing with length and even goes beyond the applied sending end voltage at times, leading to the phenomena called Ferranti effect in power system.

TYPES OF DAMS

BASED ON FUNCTIONS

1.Storage Dam: 
They are constructed to store water during the rainy season when there is a large flow in the river.
2.Diversion Dam: 
A diversion dam is constructed for the purpose of diverting water of the river into an off-taking canal (or a conduit).
3.Detention Dam:
 Detention dams are constructed for flood control. A detention dam retards the flow in the river on its downstream during floods by storing some flood water.
4.Debris Dam: 
A debris dam is constructed to retain debris such as sand, gravel, and drift wood flowing in the river with water.
5.Coffer Dam: 
It is an enclosure constructed around the construction site to exclude water so that the construction can be done in dry.

BASED ON STRUCTURES

1.Gravity Dam:
 These are the dams which resist the horizontal thrust of the water entirely by their own weight.
2.Arch Dam:
These are designed so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes into its foundation or abutments.
3.Buttress Dam:
 A buttress dam or hollow dam is a dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports.
4.Embankment Dam: 
These are typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock.

Transformer

Transformers Help To Move Electricity Efficiently Over Long
Distances

To solve the problem of sending electricity over long distances, William Stanley developed a
device called a transformer. The transformer allowed electricity to be efficiently transmitted over
long distances. This increased delivery range made it possible to supply electricity to homes and
businesses located far from the electric generating plant.
The electricity produced by a generator travels along cables to a transformer, which changes
electricity from low voltage to high voltage. Electricity can be moved long distances more
efficiently using high voltage. Transmission lines are used to carry the electricity to a substation.
Substations have transformers that change the high voltage electricity into lower voltage
electricity. From the substation, distribution lines carry the electricity to homes, offices, and
factories, which require low voltage electricity.

SAFETY IS FIRST

1.Be Safety Conscious

Electricity can be very harmful if you are not safety conscious.
While working with electrical circuits can be dangerous if you don’t take certain safety precautions.
Electrical shock can not only injure you but also kills you. Practice safety when working on any
circuit and slow down! When you hurry through a project, there is a greater chance for an
accident to occur.

2. Shut the Power Off
Always shut off the power to a circuit or device that you will be working on. This is the first thing
you should do before working on any electrical circuit. I don’t know anyone who has been
shocked by a circuit that is not energized.

3. Test the Circuit
After turning a circuit off, it's a good idea to check it with a tester to be sure that, indeed, it is off.
Never assume that the circuit is off!

4. Ladders
Ladders are necessary to accomplish some electrical jobs. Never use an aluminum ladder on
any electrical project. Always use an insulated fiberglass ladder to keep you safe.

5. Wet Locations
Avoid wet areas when working with or on anything electrical. If there is a reason that you have
to be in that situation, wear rubber boots and gloves to lesson your chance of getting shocked.
Tools and appliances should be plugged into a GFCI outlet or GFCI extension cord.
Don't forget to dry your hands before grabbing any cord to plug it in or unplug it. Wet hands and
a frayed cord don't mix. You reach down to grab the cord and just like that, you've been shocked!
Believe it or not, it happens.

6. Warning Labels
Finally, if you are working on the service panel or
a circuit, be sure to place a warning label on the
face of the panel. This will warn someone not to
turn on the circuit that you are working on.
There’s nothing worse than turning off the power,
checking that it’s off and starting to work on the
circuit, only to have someone come behind you
and turn the circuit back on. Always think and ask
questions before turning on a breaker that is shut
off. Maybe someone is working on the other end.