Megawatt and Mega VARs:

Megawatt:

The megawatt is equal to one million (10⁶) watts. Many events or machines produce or sustain the conversion of energy on this scale. For example: lightning strikes, large electric motors, large warships, such as aircraft carriers, cruisers, and submarines, engineering hardware, and some scientific research equipment, such as supercollider’s, and in the output pulses of very large lasers. A large residential or commercial building may consume several megawatts in electric power and heat.

The productive capacity of electrical generators operated by a utility company is often measured in MW.

Mega VARs:

Mega VAR stands for Mega Volt*Amps Reactive. Although reactive power is not 'real' (i.e. it is not considered power at the source or destination), it still consists of current flowing in the transmission lines. When current flows in the line, power (real power) is lost due to I²R losses. When you are talking about Mega VARs, this power loss is significant and is a direct loss for the power company. This reactive power is usually caused by a company having a large inductive load (lots of motors). If it is bad enough, sometimes companies will put large capacitor banks in or near their factory to try and balance things out. If they don't, the power company may ask them to pay for the losses.

Here cosθ is known as power factor. It is the ratio of real power to apparent power. It lies between the number 0 and 1.

Kilowatt-hour (KWH):

A kilowatt-hour is the amount of energy equivalent to a steady power of 1 kilowatt running for 1 hour. Generally it is known as unit.

Hence,

1 unit electricity = 1 KWH power.

Generator cooling system:

Normally generators are cooled by hydrogen gas. A cooling system consist some hydrogen cylinders, two pressure regulating valves, two isolation valves and a manifold.

Figure: Generator cooling system.

Working principle:

Ø Hydrogen gas is supplied from gas cylinders.

Ø Gas pressure is maintained at 100-125 psig by the 1^st pressure regulating valve.

Ø Gas pressure is maintained at lower value of 30 psig by 2^nd pressure regulating valve.

Ø Two insulation valves are used for insulation the supply.

Ø Finally hydrogen enters into generator through a manifold and cools the entire temperature.

Transformer

A transformer is an electrical device that takes electricity of one voltage and changes it into another voltage.

Types of transformer:

Ø Step up

Ø Step down

Ø Isolating

Ø Variable etc.

In Ashuganj power station, step up transformers are used to up the voltage and minimize transmission loss.

Step up transformer:

The transformer in which voltage is increased is called step up transformer. Here the secondary has more turns than the primary winding.Figure: Transformer.

Main parts of transformer:

Ø Transformer shell

Ø Inner core

Ø Oil reservoir

Ø Cooling system

Ø Bushing

Transformer shell:

It is a shell generally made of cast iron or steel. It holds all the equipments inside of shell. In this sense it is an outer casing of transformer.

Inner core:

Inner core means the main core of parallel plates arranged into the transformer shell. There are two types of windings, primary and secondary.

Figure: transformer core and windings.

Oil reservoir:

It is a reservoir which keeps the oil reserved for cooling of transformer.

Cooling system:

In cooling system, oil is used to cool the inner core of transformer by absorbing internal heat. Then this oil is cooled by circulating air. In air cooling system, there are fans and radiators to cool the hot oil. Oil flow through the radiators and air is blown across the radiators to cool the oil. Then the cooled oil is returned to transformer oil reservoir.

Bushing:

Bushings are insulated bars or wires that connected the transformer with other electrical equipments. It is usually filled with oil to provide extra insulation. To prevent faults, non-conducting gaskets are used with the bushing of transformer.

Introduction

Introduction:
This is the era of development. Electricity has played a vital role for the socioeconomic
development of the country. Now almost all the devices are operated by
electricity. So to generate electricity, power plant is very necessary.
Power plant:
Power plant is an assembly of equipment that produces and delivers mechanical and
electrical energy. A power plant is also referred to as a generating station or
powerhouse. It is an industrial facility for the generation of electric power.
River water screening System:
Water is the most important thing in a steam power plant. Water supplies generally are
divided into two major categories: surface water and ground water. Surface water is
available from rivers lakes and other impoundments as well as the sea. Ground water is
present is below the earth’s surface.
In Ashuganj Power plant, water is collected from the river Meghna. This water
comes through 3 channels. One channel is for CCPP, ST-1 & ST-2 and one channel is
for ST-3, ST-4 & ST-5 and other channel is for demi water.
This water is used mainly for generation of steam, for condenser, cooling of
overall system, cooling of lubricating oil, for chillers etc. So to use the water efficiently
water screening system is essential. There are three steps of water screening system.
They are described in below:
1. Heavy-duty Bar: It’s the first stage of screening system. In this stage water
is screened by trust rack. Heavy wastes like wooden piece, dead animals,
water hyacinth etc. are removed in this stage.
2. Rotating Bar: In this stage water is screened by scrapers. Smaller waste
than heavy-duty bar waste are removed in this stage.
Figure: Water screening system with Rotating and Band screening bar.
3. Band Screening Bar: It is a process where 57 baskets are arranged in such
a way that screens the water by passing water through net to remove very
small wastes like small pieces of stones, sand etc. It is the most effective and
modern screening process. A tray is placed below the baskets (net) that takes
the waste which is separated from nets by spraying water