By: Syed Muhammad Ali Shah
Electrical Engineer from UET Lahore
Submittedto: Captain Shoaib
A power plant (also referred to as a generating station, power
plant, powerhouse or generating station) is an industrial facility for the generation of electric
The center of nearly all power stations is a generator, a rotating machine that converts
mechanical power into electrical power by creating relative motion between a magnetic field and
a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly
on which fuels are easily available, cheap enough and on the types of technology that the power
company has access to.
Most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate
electricity, and some use nuclear power, but there is an increasing use of cleaner renewable
sources such as solar, wind, wave and hydroelectric.
Types of powerplants
In short there are following types of power plants
Thermal power plant (fossil fuels, coal, oil, natural gas)
Hydro power plant
Nuclear power plant
Solar power plant
Wind power plant
Wave water plant
Nishat Power Plant
Nishat power plant is indeed a “Thermal Power Plant”. This uses Furnas oil as a source of fuel.
It has 11 engines to drive same number of alternators (synchronous generators). It is a combine-
cycle power plant which uses the waste smoke of engines to run STG (steam turbine generator).
One alternator produces 17MW and STG produces 15MW, so the power plant has the total
capacity of 200MW. It uses 4MW to derive its own auxiliaries. So the dispatch to wapda is
Systems of Nishat PowerPlant
This is a power plant which has the following systems in it.
Lube oil system
Compressed air system
Programmable logic control (PLC) system
Power Transformers basics
Power Transformer protection
Heat recovery system generator (HRSG)
Heat recovery system generator operation
Steam Turbine operation
Steam Turbine instrumentations
First of all oil tankers are placedindecantingarea,where the supervisortakesthe sample of oil
tankersand sendthissample toChemical-labforchecking.Afterclearance fromchemical lablabreports
are sendto decantingareastaff anddecantingprocessstarted.
Chemical lab has chemical engineers which usually check the following requirements.
Water contents test
Stability and compatibility test
Oil Transfer Pump
Oil from “Storage tanks” come to FT House by using suction pump, from where it is
pumped to “Buffer tanks”. There are two buffer tanks; each has the capacity of 200m3.
Temperature of oil in Buffer tank is approximately 65 to 70 degrees centigrade.
Oil from Buffer tanks pump back to FT House to pass through “Separator”. There are six
separators. It works on the principal of centrifugal force, where impurities move towards
the wall of separator and pure oil is collected from center. From separator oil is pumped
into “Day tank”. There are two Day tanks, each has the capacity of 500m3. Temperature
of oil in Day tank is approximately 85 to 90 degrees centigrade.
Oil from Day tank is pumped into feeder unit, where there is a check of its density,
viscosity, pressure and flow rate. The pressure is maintained to 5 bars. The important
sensors in this unit are given below
By pass Buckle valve
After this the oil is send to engine.
Oil in Engine
Clean leak Dirty leak Tank
HFO from feeder unit go into “Clean leak Dirty leak Tank”. Here it comes into
and go out, it has only the function to maintain temperature to 94 degree centigrade. Than
it goes through three way valve, where we can also have a control to take Diesel(LFO) in
the line instead of HFO in case of maintenance.
Fuel shut off valve
This is an emergency valve to disconnect fuel supply.
Than we have a flow meter, to check rate of flow of fuel
Here we have a mixing tank, it allows the fuel
To settle down
To obtain the same temperature
Allows the engine to run for one or two minutes in case of emergency when fuel
is disconnected due to some fault.
Oil from clean leak apartment in “clean leak dirty leak tank” also comes into it.
Unburnt oil is also pumped back into it.
This increases the pressure of oil.
This rises the temperature of fuel to 109 degree centigrade.
Now there are two duplex filters, one is under use other one is standby mode. It cleans
the fuel and allows going into the Combustion chamber.
Now there is a pump which rises the pressure of fuel to 1400 bars.
Injector allows the fuel to inject into combustion chamber with the pressure of 450 bars.
Oil from open channels
From open channels, oil go into dirty apartment of “Clean leak Dirty leak Tank”.
Fromwhere it is wasted as sludge.
Oil from close channels
From close channels, oil go into clean apartment of “Clean leak Dirty leak Tank”. from
where there is a three way valve to control whether we want to move this into “Buffer tanks” or
in “Mixing Tank”.
We start from decanting area. After checking the specificities of lube oil, it is unloaded from the
tankers, where it goes into “New lube oil tank” by passing through lube oil pump unit.
If due to leakage or after the service of engine, lube oil is required to collect into Sump of
engine, it is pumped from the lube oil pump unit. Lube oil comes into, lube oil pump unit from
New lube oil tank
There are basically two very important processes regarding to lube oil system
Lube oil separator
Lube oil temperature maintenance unit
Lube oil separator
Lube oil from sump after passing through stainer pumped into separator chamber,
which works on the principle of centrifugal. Impurities go towards the walls of separator
while cleaned oil from the center go again into the sump.
Lube oil temperature maintenance unit
Lube oil from the sump is pumped into a unit with a pressure of 4.3 bar , where
there is a “three way valve” and a “steam heater”. P.L.C controls the opening of three
way valve in such a way, that the temperature of lube oil is maintained at 63 degree
centigrade. After this there are two, parallel “Candle filters” which cleans the lube oil.
Now the lube oil is ready to go into “Oil gallery”, where it is used to lubricate the inner
parts of engine. But one more thing, before going into oil gallery, there are two pipes
known as “Turbo A and Turbo B”, which have the oil from candle filters but with the
pressure of 1.9 bar. After lubrication, lube oil comes back into the sump.
Used Lube Oil and Service Lube Oil Tank
There is a pipe connection in separator unit, from which we can control whether
the oil is allowed to go in “Used lube oil tank” or “Service tank
If the oil is dirty and completes its life it is pumped into used lube oil tank, from where it
If the engine is allowed to have a maintenance than engine is made empty with lube oil.
This is pumped into service tank. From where it goes into lube oil pump unit, where it is
ready to be used for engine.
Pre Lube oil
There is a line in parallel to pump, when the engine is just started than lube oil of
this line is under use.
Compressed Air System
There are 6 compressed air pumps to have an air with the pressure of 30 bars.
There are 2 “instrument air units” to have an air with pressure 7 bars.
30 bars Compressed Air
First there is are 3 units, each having two compressed air pumps. Each pump followed by
a separator unit, which removes “oil/ water contents” from the compressed air. Than
there is a “mechanical valve. After that the lines of two pumps becomes common, and
this line now becomes common with the other two units. Finally the compressed air is
stored in “Air bottles.
Actually two from the six pumps are on operation; other four are on standby
When compressed air has pressure 25 bars, the pumps are on.
When pressure becomes 30 bars, the pumps are off.
There are three air bottles in Hall-A and two in Hall-B.
Each one have the following parameters
Capacity of 2800 liters
Compressed air in it has temperature 75-76 degree centigrade
There are two uses of compressed air
When ignition is not started, this air compresses the piston to achieve a specific rpm,
after that, fuel is injected for combustion.
For control purposes
Cut off fuel supply
7 bars Compressed Air
There are two “Instrument air units” which compressed the air to 7 bars. Each unit have a
compressed air pump, than the separator and a valve. These units have their own air storage
There is also a line from 30 bars compressor unit to air bottles of bars, with the “pressure
controlled pump”, which control pressure from 30 bars to 7 bars.
This air is used by air consumers.
There are two important terms used in cooling system
“HT water” which means high temperature water above 70 degree centigrade
“LT water” which means low temperature water.
Water from “Heat Exchanger” go into cooling towers, where it showers from the top, and its
temperature reduces to 36 degree centigrade. The cooled water is than pumped back into the heat
Actually it is an open water system, and it does not mix with water which flows into close
system (water which cools different parts of system).
Three Way valve
There is a three way valve controlled by PLC system for the temperature of HT to maintain at
There is a line from the three way valve known as HT line. HT pump pumps the water into the
“Engine Liner” for its cooling and than the water go for the cooling of “Engine Head”.
Temperature of “engine lining and head” are very high, so they are cooled by HT water of
temperature 90 degree centigrade. The outgoing water has the temperature of 91 degree
centigrades. And now the HT water reaches again at three way valve.
If outgine water from the engine header has temperature greater than 91 degree centigrade, than
PLC decides through three way valve and allow the water to go towards heat exchanger for
cooling. After cooling of water if required it passes through LFO to decrease its temperature.
Than there is a line of HT which meets the line of LT to maintain the temperature of LT around
43 degree centigrade. The LT water is pumped into 2nd side of Turbo-cooler, than it passes
through Lube-oil Heat exchanger, finally it passes through 1st side of Turbo-cooler. Now the
water line again reach at the point just after the three way valve.
Sometimes condensate is very much cooled, so to maintains its temperature, the water that is
going for cooling in heat exchanger is passed through it, which warms the condensate.
When the engine is just started its temperature is not too high. To keeps its temperature above 53
degree centigrade, a line which takes water from HT from one point and drops it into the HT line
at another point, resulting the circulation of HT into the engine which continuously increses its
temperature at the appropriate point.
There is an expansion vessel, its water also circulate in the circuit. It has following purposes;
For make-up water in case of leakage
Its reading also tells, whether there is any water leakage in the circuit.
Steam Turbine Generator (STG)
Feed Water Tank
Temperature of water in Feed Water Tank is 166 degrees centigrade. Whenever its level
decreases less than 20m3, TDS pure water tank fills it.
Main Parts of Boiler
There are four main parts of a boiler
1) LP Evaporator
3) HP Evaporator
4) Super Heater
Water from Feed Water Tank comes in LP evaporator, and then returns back to Feed
Water Tank. This circulation of water between Feed Water Tank and LP Evaporator is in
order to maintain the temperature of Feed Water Tank to 165 degrees centigrade.
There are Feed Water Pumps which pump the water from Feed Water Tank to Economizer
through Feed Water Assembly. When water level in boiler is:
50% than half valves of Feed Water Assembly are open
More than 50% than valves of Feed Water Assembly start towards closing
Less than 50% than valves of Feed Water Assembly start towards opening.
This Feed Water Assembly Valves are controlled by PLC. The temperature in this section
is about 250 degrees centigrade. The water than goes into Steam Drum.
High temperature water from Steam Drum comes now in HP Evaporator. The
temperature of this section is around 275 degrees centigrade. The water is converted into
steam and sends back to Steam Drum.
Steam from Steam Drum comes now in Super Heater. Here the temperature is around 300
degrees centigrade, so if any of moisture is there in steam, it is converted into steam. So
we get a “Dry Steam”.
From all the boilers, the lines of their Dry Steam fall into Steam Header, where it is collected.
Steam from Steam Header passes through Cyclone Separator in order to remove, if any of
water content is there in it.
Then there are two isolating valves, which allows the steam to go either in Turbine or in
Emergency Stop Valve
Then there is an Emergency Stop Valve to stop the steam flow.
Lube Oil System
There is a Sump in which Lube Oil is present or it comes after lubricating different parts of
There are three different pumps which pump the oil from sump in different situations.
When turbine is just started, Lube Oil is pumped with the help of DC Pump.
When turbine is in normal running condition, Lube Oil is pumped with the help of
When turbine’s rpm go below 5200, than Lube Oil is pumped with the help of Auxiliary
NRV valve (no return valve)
This is a valve followed by each pump, so whenever any of the pump is in operation, the
NRV valve of the other pump makes it confirm for the Lube Oil not to flow in that pump
in opposite direction.
All the three pumps meet at a common point.
Lube Oil Cooler
Lube oil passes through Lube Oil Cooler, where it is cooled.
Lube Oil Filter
After cooling lube oil passes through Lube Oil Filter where impurities are removed from
Then there are two lines emerging from that point.
1) One going towards Control Pump, which after passing through “Control valve”
reaches “Emergency stop valve” and then lubricates “Throatier Valves”.
2) Second line lubricates different parts of Turbine.
Heat Engine is a mechanical machine which converts chemical energy of fuel into mechanical
Parts of Heat Engine
Turbo charger cooler
Set of Pistons
Working of Heat Engine
Different systems for the proper working of heat engine are given below:
After refining, maintaining temperature and appropriate pressure fuel is injected into
combustion chamber of engine. Fuel is injected at the pressure of 450 bars. Pressure
and temperature are maintained to increase efficiency. This is a complete system as
already been discussed.
To increase the efficiency of engine, air is filtered and compressed by turbo charger,
then cooled by “charger coolers”, which than mix with fuel to produce combustion.
This is a complete system as already been discussed.
Lube oil system
To lubricate different parts of fuel, lube oil is used. This is a complete system as
already been discussed.
To cool different parts of engine, water system is there for this purpose. This is a
complete system as already been discussed.
Different protections of Engine are given below:
Lube Oil level
Lube Oil pressure
Lube Oil temperature
Lube Oil properties
OMD (Oil Mist Detector)
Over speed (Electrical 10% + Mechanical 15%)
Barring temperature safety
High exhaust safety