Chapter 1

DAMS OVERVIEW

Some of the major dams in Pakistan are

1.1)Tarbela Dam

It is one of the biggest dam in Pakistan. It was constructed on Indus or Sindh River. It

is adjacent from Attock, Rawalpindi, Abbotabad. It was constructed in 1976. Its water

is used for power generation and irrigations purpose. It is 143 meter high & 2750

meter in width. Terbela Dam is one of the leading source for electric capacity. 

1.2)Mangla Dam

Location: Mirpur Azad Kashmir, 99 km from Islamabad. Mangla is constructed on

river Jehlum. With economic aid from word bank it was constructed in 1967. It is 138

meter high and 3140 meter wide. Elevation of 865 feet SPD. Ten Francis type

turbines in the power house are present

1.3)Khanpur Dam

 Khanpur Dam is located in KPK province but very neat to Islamabad. Many people

don’t know that it is also a picnic point very near to Twin Cities at short distance of

just 25 Miles. You can go there from short link roads by crossing Margala Hills or

from Abottabad Road. It is mainly used as water reservoir and is used for supply of

drinking water to Islamabad and Rawalpindi. Its water is also used for agriculture

purposes in nearby areas. It was built in era of Field Marshal Muhammad Auyb

Khan. 

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Chapter 2

Mangla power house specifications

Water storage: 6.65 million acre feet (2.88MAF of additional water available)

The water to power house is provided through five steel lined tunnels of 30/26 ft

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Chapter 3

Work Observed

3.1) Auto Transformer

This is a transformer with only one winding instead of primary and secondary windings found

on a simple power transformer. A/T is the most important part of the grid station. It is used to

step-up or step-down the voltage or power.

Auto Transformer

Advantages of A/T

Single winding is required instead of Double. It is less expensive than simple transformer of

the same rating. Copper required is very less. High efficient than two winding transformer.

Small size and low cost. Resistance and leakage reactance is less compared to two winding

transformer.

3.2) Potential Transformer

It is primarily a step - down transformer & step down voltage in known ratio. The

main of these transformer contain of a large number of turn of well wire coupled

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across the line, The secondary way consist of a rare turns and offers for measuring

instruments & relay a voltage which is recognised portion of the line voltage.

Potential Transformer

3.3) Circuit Breaker

I observe circuit breaker of grid station. It has three types of circuit breakers oil, SF6

and vacuum. First I observe the SF6 circuit breaker. There are number of C.B. The

name of circuit breaker shows that circuit breaker combine the SF6 gas Sulphur

hexafluoride gas for are extinction. In normal condition is fixed and moving contract

are tough with each other and circuit breaker is in closed position, and current will be

flow from supply to circuit breaker has hollow moving and fixed contact in abnormal

condition. The SF6 circuit breaker in 132kv grid station has 1600A capacity .It has

rated voltage 145kv.

The 1600A capacity of C.B means that it can handled the current of 1600A without

disconnect the supply it can easily handle 1600A current will be increase from rated

capacity e.g. 1600A it will tripped or disconnect the supply that is used for any circuit.

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Its voltage rating also shows that C.B can works maximum 145kv .but as far as

voltage will increase the C.B will be opened its fixed and moving contact. It has rated

frequency 50/cycle. Its efficiency will be maximum at voltage that has 50/cycle

frequency. It has total break time at rated breaking contact is three cycle. Its means

that when the fault will held the circuit breaker will disconnected supply after

completing three cycle from its maximum rated voltage. Its rated gas pressure is

5Kg/cm at 20 c. it means that gas has 20 c temperature and 5Kg/cm pressure in this

C.B. It is made of Mitsubishi electric corporation japan. Its rated voltage is 145KV. It

has also similar frequency rating that is 50c/s. Its normal current is 200 A. Its total

mass is 1500 Kg. I visit other C.B. it is made of Siemens. Its date of energization was

16/5/2002. Its rated voltage is 145KV. It has also similar frequency rating that is

50c/s. Its normal current is 200 A. Its total mass is 1500 Kg.

Circuit Breaker

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3.4) Generators and Transformers Ratings at Mangla Power Station

3.5) Protective Relays

The protective relay is device that connect between main circuit and circuit breaker. It

gives the trip signal to circuit breaker for disconnect the supply path during

abnormality effect. All type of relays used for short circuits. They supplied by CTs

and PTs. Failures in the system are indicated by changes in current in voltages. For

every types of fault and some difference in these quantities each relay designed to

recognize difference and operate in response to it.

The difference may be in term of magnitude, frequency ,phase angel ,rate of

change ,harmonic, wave shape duration of condition the relay fault current and its trip

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coil energized and trip signal to circuit breaker to disconnect the supply from supply

source to load current. It has main three components such as sensing element,

comparison, and control element the sensing element sense the actuating quantity and

gives the response.

Electromechanical Relays

3.6) Rectifiers & Battery Room

Relays operate on D.C

We need rechargeable batteries for the D.C

To recharge batteries we need to convert A.C to D.C so we use Rectifier.

All batteries are connected in parallel and each is of 2 V.

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Battery Room

3.7) Shunt Reactor

Shunt Reactor is used to keep voltage level constant in the line.

It is usually plugged between two phases or between phase or neutral.

Long Transmission line which have less load, we need to compensate or

absorb the reactive power due to line capacitance’s leading current.

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Shunt Reactor

3.8) Isolator

Isolator is always positioned before Circuit Breaker as Additional Protection.\

It does not used to break the load current.

Because there is no system to eliminate arc.

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Isolators

3.9) Bus Bar

Bus bar is a constant voltage supplier conductor.

Bus bars are the nerve-centres of the power system where various circuits are

connected together.

These are the nodes of the electrical circuit.

Under the normal power flow condition the sum of incoming currents is equal

to the sum of outgoing currents.

3.10) Current Transformers (CT)

Current transformers are commonly used to measure currents of high magnitude.

These transformers step down the current to be measured, so that it can be measured

with a normal range ammeter. A Current transformer has only one or very few

number of primary turns. The primary winding may be just a conductor or a bus bar

placed in a hollow core (as shown in the figure). The secondary winding has large

number turns accurately wound for a specific turns ratio. Thus the current transformer

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steps up (increases) the voltage while stepping down (lowering) the current.

 Now, the secondary current is measured with the help of an AC ammeter. The turns

ratio of a transformer is NP / NS = IS / IP

Current Transformer

3.11)Earthing

To connect the metallic (conductive) Parts of an Electric appliance or installations to

the earth (ground) is called Earthing or Grounding.

In other words, to connect the metallic parts of electric machinery and devices to the

earth plate or earth electrode (which is buried in the moisture earth) through a thick

conductor wire (which has very low resistance) for safety purpose is known

as Earthing or grounding.

To earth or earthing rather, means to connect the part of electrical apparatus such as

metallic covering of metals, earth terminal of socket cables, stay wires that do not

carry current to the earth. Earthing can be said as the connection of the neutral point

of a power supply system to the earth so as to avoid or minimize danger during

discharge of electrical energy.

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3.12) Fire Protection System

Fires in electric power generating plants can have pricey & even deadly implications.

Yet, the vendors & operators of many plants have paid little if any effectiveness to

fire subdual systems since they were installed 10 or even 20 years ago. In about one-

third of the cases in which fire suppression systems fail to operate as expected, the

cause is insufficient examination, testing and maintenance.

Fire pumps

Hydrants

Sprinkler/water spray systems

Hose houses

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