I am going to share something that relates to power systems

In generally The load on the power station will be varied because of Variable load

We have such a doubt called what is Variable load ????

We all know that suppose in a house we do not use the all applications in all time . And different appliances have different power ratings and the example​ of appliances are ( e.g Electric Bulb , Motors, Fans, Etc )

It has  Various Effects on the Power System

Effects Of Variable Load On Power Station :

Need Of Additional Equipment :

The variable load on a power station necessitates to have additional equipment. By way of illustration, consider a steam power station. Air, coal and water are the raw materials for this plant. In order to produce variable power, the supply of these materials will be required to be varied correspondingly. For instance, if the power demand on the plant increases, it must be followed by the increased flow of coal, air and water to the boiler in order to meet the increased demand. Therefore, additional equipment has to be installed to accomplish this job. As a matter of fact, in a modern power plant, there is much equipment devoted entirely to adjust the rates of supply of raw materials in accordance with the power demand made on the plant.

Increase In Production Cost :

The variable load on the plant increases the cost of the production of electrical energy. An alternator operates at maximum efficiency near its rated capacity. If a single alternator is used, it will have poor efficiency during periods of light loads on the plant. Therefore, in actual practice, a number of alternators of different capacities are installed so that most of the alternators can be operated at nearly full load capacity. However, the use of a number of generating units increases the initial cost per kW of the plant capacity as well as floor area required. This leads to the increase in production cost of energy

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Diesel Power Station Explanation

I am here to discuss about the Diesel Power Station which may be used as a emergency purpose of power generation

Important Link

The Main Sources Of Energy

The majority power is generated by the

Hydroelectric Power Station

Nuclear Power Station

Thermal Power Station

Diesel Power Station :

Layout

A generating station in which diesel engine is used as the prime mover for the generation of electrical energy is known as diesel power station.

In a diesel power station, diesel engine is used as the prime mover. The diesel burns inside the engine and the products of this combustion act as the “working fluid” to produce mechanical energy. The diesel engine drives the alternator which converts mechanical energy into electrical energy.

As the generation cost is considerable due to high price of diesel, therefore, such power stations are only used to produce small power. Although steam power stations and hydroelectric plants are invariably used to generate bulk power at cheaper cost, yet diesel power stations are finding favour at places where demand of power is less, sufficient quantity of coal and water is not available and the transportation facilities are inadequate.

These plants are also used as standby sets for continuity of supply to important points such as hospitals, radio stations, cinema houses and telephone exchanges.

The plant consists of following parts

The Main Parts Of Diesel Power Station :

1. Fuel Supply System :

It consists of storage tank, strainers, fuel transfer pump and all day fuel tank. The fuel oil is supplied at the plant site by rail or road. This oil is stored in the storage tank. From the storage tank, oil is pumped to smaller all day tank at daily or short intervals. From this tank, fuel oil is passed through strainers to remove suspended impurities. The clean oil is injected into the engine by fuel injection pump.

2) Air Intake System

This system supplies necessary air to the engine for fuel combustion. It consists of pipes for the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from air which may act as abrasive in the engine cylinder.

3) Exhaust System

This system leads the engine exhaust gas outside the building and discharges it into atmosphere. A silencer is usually incorporated in the system to reduce the noise level.

4) Cooling System

The heat released by the burning of fuel in the engine cylinder is partially converted into work. The remainder part of the heat passes through the cylinder walls, piston, rings etc. and may cause damage to the system. In order to keep the temperature of the engine parts within the safe operating limits, cooling is provided. The cooling system consists of a water source, pump and cooling towers. The pump circulates water through cylinder and head jacket. The water takes away heat from the engine and itself becomes hot. The hot water is cooled by cooling towers and is recirculated for cooling.

5) Lubricating System

This system minimises the wear of rubbing surfaces of the engine. It comprises of lubricating oil tank, pump, filter and oil cooler. The lubricating oil is drawn from the lubricating oil tank by the pump and is passed through filters to remove impurities. The clean lubricating oil is delivered to the points which require lubrication. The oil coolers incorporated in the system keep the temperature of the oil low

6) Engine Starting System

This is an arrangement to rotate the engine initially, while starting, until firing starts and the unit runs with its own power. Small sets are started manually by handles but for larger units, compressed air is used for starting. In the latter case, air at high pressure is admitted to a few of the cylinders, making them to act as reciprocating air motors to turn over the engine shaft. The fuel is admitted to the remaining cylinders which makes the engine to start under its own power.

Advantages Of Diesel Power Station :

1. The design and layout of the plant are quite simple
2. It occupies less space as the number and size of the auxiliaries is small.
3. It can be located at any place.
4. It can be started quickly and can pick up load in a short time.
5. There are no standby losses.
6. It requires less quantity of water for cooling.
7. The overall cost is much less than that of steam power station of the same capacity.
8. The thermal efficiency of the plant is higher than that of a steam power station.
9. It requires less operating staff.

Disadvantages

1.   The plant has high running charges as the fuel (i.e., diesel) used is costly.
2. The plant does not work satisfactorily under overload conditions for a longer period.
3. The plant can only generate small power.
4. The cost of lubrication is generally high.
5. The maintenance charges are generally high.

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Switch Gear And Classification Of Switch Gear

What is meant By Switch Gear :


The apparatus used for switching , controlling and protecting an electrical circuit (or) equipments is known as switch gear

Examples are

Swich

FUSE

Relay

Functions of Switchgear Equipment

Normal conditions:

For the purpose of operation and maintenance

Abnormal conditions:

for clearance of fault quickly 

Classification of Switchgear

I. Based on location, switchgear are classified as

•Indoor

Generally up to 36kVA

•Outdoor

Generally greater than 36 kVA

II. Based on working voltages they are classified as

•Low voltage switchgear (up to 3.6 kV)

•Medium  voltage switchgear ( from 3.6 kV to 12 kV)

•High  voltage switchgear (> 12 kV)

1. A Switch is 

a)Fuse

b)Circuit breaker and fuse

c)Circuit breaker

d)None

2. A Switchgear is  installed

a)Outdoor only

b)Outdoor or Indoor 

c)Indoor only

d)No need to install

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The Main Sources Of Energy On Earth

Sources Of Electrical Energy :

Since electrical energy is produced from energy available in various forms in nature, it is desirable to
look into the various sources of energy. These sources of energy are :
(i) The Sun 
(ii) The Wind 
(iii) Water 
(iv) Fuels 
(v) Nuclear energy.


Out of these sources, the energy due to Sun and wind has not been utilised on large scale due to
a number of limitations. At present, the other three sources viz., water, fuels and nuclear energy are
primarily used for the generation of electrical energy.

The Sun

The Sun is the primary source of energy. The heat energy radiated by the Sun can
be focussed over a small area by means of reflectors. This heat can be used to raise steam and
electrical energy can be produced with the help of turbine-alternator combination. However, this
method has limited application because :

(a) it requires a large area for the generation of even a small amount of electric power
(b) it cannot be used in cloudy days or at night
(c) it is an uneconomical method.

Nevertheless, there are some locations in the world where strong solar radiation is received very
regularly and the sources of mineral fuel are scanty or lacking. Such locations offer more interest to the solar plant builders.


The Wind
This method can be used where wind flows for a considerable length of time.
The wind energy is used to run the wind mill which drives a small generator. In order to obtain the thectrical energy from a wind mill continuously, the generator is arranged to charge the batteries.

These batteries supply the energy when the wind stops. This method has the advantages that
maintenance and generation costs are negligible. 
However, the drawbacks of this method are


(a) variable output,
 (b) unreliable because of uncertainty about wind pressure and 
(c) power generated is quite small.


Water

When water is stored at a suitable place, it possesses potential energy because of the
head created. This water energy can be converted into mechanical energy with the help of water
turbines. The water turbine drives the alternator which converts mechanical energy into electrical
energy. This method of generation of electrical energy has become very popular because it has low
production and maintenance costs.

Fuels

The main sources of energy are fuels viz., solid fuel as coal, liquid fuel as oil and gas
fuel as natural gas. The heat energy of these fuels is converted into mechanical energy by suitable
prime movers such as steam engines, steam turbines, internal combustion engines etc. The prime
mover drives the alternator which converts mechanical energy into electrical energy. Although fuels continue to enjoy the place of chief source for the generation of electrical energy, yet their reserves are diminishing day by day. Therefore, the present trend is to harness water power which is more or less a permanent source of power.



Nuclear Energy


Towards the end of Second World War, it was discovered that large amount
of heat energy is liberated by the fission of uranium and other fissionable materials. It is estimated that heat produced by 1 kg of nuclear fuel is equal to that produced by 4500 tonnes of coal. The heat produced due to nuclear fission can be utilised to raise steam with suitable arrangements. The steamcan run the steam turbine which in turn can drive the alternator to produce electrical energy. However,.there are some difficulties in the use of nuclear energy. The principal ones are 
(a) high cost of nuclear plant 
(b) problem of disposal of radioactive waste and dearth of trained personnel to handle the plant.

Comparision Of Energy Sources

Principles of Power Systems PDF By V.K Mehta

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Nuclear POwer Station

Nuclear Power Station :

Nuclear energy is available as a result of fission reaction. In a typical system, Uranium 235 is
bombarded with neutrons and Heat energy is released. In chain-reaction, these release more neutrons,
since more Uranium 235 atoms are fissioned. Speeds of Neutrons must be reduced to critical speeds
for the chain reaction to take place. Moderators (= speed-reducing agents like graphite, heavy water,
etc). are used for this purpose. Nuclear fuel rods (of Uranium 235) must be embedded in speed￾reducing agents. Further, control rods (made of cadmium) are required since they are strong neutron￾absorbers and help in finely regulating this reaction so that power control of the generator is precisely
obtainable. When control rods are pulled out and are away from fuel rods, intensity of chain reaction
increases, which increases the power output of the system. While if they are pushed in and closer to
the fuel rods, the power-output decreases. Thus, the electrical load demand on the generator decides

(automatically) the control-rod positions through a very sophisticated control system.

block diagram of nuclear power station

Advantages :-
1. Quantity of fuel required is small for generating a given amount of electrical energy, compared
to that with other fuels.

2. It is more reliable, cheaper for running cost, and is efficient when operated at rated capacity.

Disadvantages :-
1. Fuel is expensive and not abundantly available everywhere. 2. It has high capital cost.

3. Maintenance charges are high. 4. Nuclear waste disposal is a problem.

Hydro Electric Power Generation

Hydro Electric Power Generation :

Water-reservoir at higher altitudes is a pre-requisite for this purpose. Power-house is located
at a lower level. The difference in these two levels is known as “Head.”


Based on the “Heads”, the Hydroelectric stations are categorized below:

1. Low head up to 60 metres. 
2. Medium head between 60 and 300 metres.

3. High heads above 300 metres

showing simple hydro plant

In this method of generation, water from higher height is passed through penstock as controlled
in the valve-house, into the water turbine. Thus, potential energy of water stored at higher altitudes is
first converted into Kinetic energy. As the water reaches the turbine, it gains speed after losing the
Potential energy. Kinetic energy of this speedy water drives the water turbine, which converts this
into mechanical output. It drives the coupled generator, which gives Electrical energy output.
A schematic diagram of such a system is shown in fig.


The valve house has a controlling valve (=main sluice valve) and a protecting valve (= an
automatic, isolating, “butterfly” type valve). As is obvious, power control is done by the main sluice
valve, while “butterfly” valve comes into action if water flows in opposite direction as a result of a
sudden drop in load on the generator. Otherwise, the penstock is subjected to extreme strains and it

has a tendency to burst due to pressure of water as a result of sudden load reduction.

Note: Variation of Head (low-, medium-, or high-head) will affect the block-schematic

After doing the work (of imparting its energy to the water turbine), the water is allowed to pass
into the tail-race reservoir.
The water turbines are essentially low-speed prime movers. In that, the best operating speed is
dependent on the head. Alternators coupled to water turbines thus have large number of poles (since
P= 120 f/N). Such alternators have the Salient-Pole type rotor.
There are different types of water turbines suitable for different cases (i.e. Heads, Power
rating, Load-variation curve, etc). Since, this is only an elementary treatment, these aspects will not

be discussed here.

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