report on the Mahi power plant

PT&IV AT MAHI HYDEL POWER PLANT
SESSSION 2014-2018 PAGE 1
CHAPTER 1
INTRODUCTION
 Mahi Hydel Power Station
The Mahi River is flowing in the southern part of Rajasthan near Banswara. The
power potential of this river has been exploited by constructing following#two#Power#
Houses:-
Mahi Power House-I (2x25MW) Mahi Power House -II (2 x 45MW)
FRL 281.5M(923ft.) Up Stream reservoir level 220.5M(723.5ft)
Live storage capacity 65.45TMCuft Live storage capacity 1.53Million
cubic(54.4MCft)
Mahi Hydel Power Station is R.V.U.N.Ltd. Major Hydel generating station situated on
river Mahi near Banswara city, comprising of 2-phases of installed capacity 140MW.
T/G supplier : BHEL (Bharat Heavy Electrical Ltd.)

HYDEL POWER STATIO-NS:
Fig.1.1 Mahi Dam
Stage Unit No. Capacity(MW)
Cost(Rs.
Crore)
Synchronizing
Date
I 1 25
68
22.1.1986
2 25 6.2.1986
II 1 45
119
15.2.1989
2 45
17.9.1989
S. No. Name of
Project
Capacity Date of commissioning
1. RMC
Mahi-I
2x0.4 MW Nov., 93
2. RMC
Mahi-II
1x0165 MW March, 91

Quick facts:
Development of the multistate MAHI BAJAJ SAGAR Project started with laying of the
foundation stone in 1960. The project is named after national leader Shri Jamnalal Bajaj.
Major construction activities started in 1972 and the project was dedicated by Prime
Minister Indira Gandhi in Jan 1983. Releases from Mahi Reservoir are to Power House I
(2 x 25 MW), 8km from Banswara city, for sale into Rajasthan. The share of Gujarat
state is routed to Power House II (2x45 MW) 40km from Banswara town on the bank of
the ANAS River, a major tributary of the Mahi.
Mahi Hydel Power Station (140 MW):
Two power houses are operating under this power station having total installed
capacity of 140 MW (2x25 & 2x45 MW). During last three years there had been
appreciable increase in the power generation from this plant due to heavy rains in the
region. However, during the year 2003-04 heavy rains were witnessed in the
catchment‟s area of river Mahi and 191.63 MU have been generated from this power
station.
PLANT SPECIFICATION’S:- (2 X 25 MW)
Capacity of machines 2 x 25 MW.
Type of turbine FRANCIS TYPE [VERTICALSHAFT]
Date of commissioning of Unit I 22-1-1986
Date of commissioning of Unit II 06-2-1986.
Date of dedication of Nation 13-2-1986
Types of generator UMBRELLA Type.
Capacity of generator 27.778 MVA. At 11 kV, 0.9pf, lag
Rated Speed 150 rpm.
Turbine output at rated head of 40m 25.825 MW.

Capacity of power transformer 11/132 kV,31.5 MVA, 3-Ø.
Diameter of Penstock pipe 4.2m
Length of Penstock pipe 9m
Length of Tail Race tunnel 1462m
Tail Race level max. (from sea level) 238 m
Tail Race level min. (from sea level) 231 m
Capacity of Reservoir (at 281.5 m) 80 TMC
FIG:-1.2 Mahi Power House-I
ELEMENTARY DESCRIPTION OF “MAHI HYDRO POWER STATION”

Definition‟s: A generating station which utilizes the potential energy of water at a high
level for the generation of electrical energy is known as a hydro electric power station.
It contains the following of the elements:-
1.Dam:
A dam is barrier which stores water and creates water head. Dams are built of concrete or
stone masonry, earth or rock hill. The type of arrangement depends upon the topography
of the sight.
2. Penstock:
Penstock is open or closed conduits which carry water to the turbines. They are generally
made of reinforced concrete or steel. Concrete penstock is suitable for low or medium as
greater pressure causes rapid deterioration of concrete.
Number of penstock = 2
Diameter = 4200 mm
Length = 92m (each)
Intake level = 250.32m
Outlet level = 230.15m
Plates = 16mm (thick.)
3. Reservoir:
It is constructed behind the dam to store water. From here the water takes to turbine
through the penstock. The generation depends upon the head of the water behind dam.
Generally the required head is about 281m
4. Water turbines:

Water turbines are used to convert the energy of falling water into electrical energy. Here
the water turbine used is FRANCIS type turbine; it is a reaction turbine in which water
enters the runner partly with pressure energy and partly with velocity head.
5. Generating Units:
An alternator is connected with the shaft of turbine. The alternator used is of 3-phase silent
pole type, it is used for low speed. When shaft of water turbine starts to rotate then
generator also rotate and electricity is produced.
HYDROPOWER GENERATING STATIONS:-
Hydropower generating stations convert the energy of moving water into electrical energy
by means of a hydraulic turbine coupled to a synchronous generator. The power that can
be extracted from a waterfall depends upon its height and rate of flow. Therefore, the size
and physical location of a hydropower station depends on these two factors.
The available hydropower can be calculated by the following equation:
Where,
P = Available water power (kW)
q = Water rate of flow (m3/s)
h = Head of water (m)
9.8 = Coefficient used to take care of units.
The mechanical power output of the turbine is actually less than the value calculated by
the preceding equation. This is due to friction losses in the water conduits, turbine casing,
and the turbine itself. However, the efficiency of large hydraulic turbines is between 90
and 94 percent. The generator efficiency is even higher, ranging from 97 to 99 percent,
depending on the size of the generator.

Hydropower stations can be divided into three groups based on the head of water:
1. High-head development
2. Medium-head development
3. Low-head development
High-head developments have heads in excess of 300 m, and high-speed turbines are used.
Such generating stations can be found in mountainous regions, and the amount of
impounded water is usually small. Medium-head developments have heads between 30 m
and 300 m, and medium speed turbines are used. The generating station is typically fed by
a large reservoir of water retained by dikes and a dam. A large amount of water is usually
impounded behind the dam. Low-head developments have heads fewer than 30 m, and
low-speed turbines are used. These generating stations often extract the energy from
flowing rivers, and no reservoir is provided. The turbines are designed to handle large
volumes of water at low pressure.
One-line diagram of electric-power system
FIG-System of paralleled generators and transformer.

CHAPTER 2
GENERATOR TYPE AND DRIVES
GENERATOR TYPES AND DRIVES:-
A large amount of electricity is required to power machinery that supplies to Drives.
Fig:- Generator
The generator is the power source for the electrical system .A generator
operates most efficiently at its full-rated power output, and it is not practical to have one
large generator operating constantly reduced load.
If#one#generator#is shut down because of damage or scheduled maintenance, there is still
a source of power for lighting until the defective generator has been repaired. In addition,
generators are widely spaced in the engineering spaces to decrease the chance
that all electrical plants would be disabled
.

2.1 PERMANENT MAGNET GENERATOR (P M G):
The PMG provides a 3-Ø low voltage supply to the turbine governed at a frequency
directly related to the speed of the set. Provision has been made for synchronizing its
voltage to that of main generator during its excitation, if required for turbine governor
operation.
PMG:-* Type- APV107M6 ,Pole- 40, Frequency- 50Hz,3-Ø
N=150 rpm, 1.0 KVA, 110V, star connected
* Stator winding resistance between terminals at 20° at 20°c is 2-359 .
* Field winding resistance (at 20°c) 0- 80.
* Air gap 5 mm.
2.2 COLLECTOR RINGS AND BRUSH GEARS:
The collector rings are attached to and are insulated from the fabricated steel shaft
mounted on the spider. The leads from the collector to the field run along the shaft and
joined at suitable points to facilitate dismantling of the rotor. The brush gear for the
collector is mounted on insulated studs on the top bracket and is easily accessible for
inspiration purpose. A DC generator is a rotating machine that changes mechanical
energy to electrical energy. The power output depends on the size and design of the dc
generator. A typical dc generator is shown in figure.

CHAPTER-3
GENERATORS
AC GENERATORS:-
AC generators are also called alternators. In an ac generator, the field rotates, and the
armature is stationary. To avoid confusion, the rotating members of dc generators are
called armatures; in ac generators, they are called rotors. The general construction of ac
generators is somewhat simpler than that of dc generators. An ac generator, like a dc
generator, has magnetic fields and an armature. In a small ac generator the armature
revolves, the field is stationary, and no commutator is required. In a large ac generator, the
field revolves and the armature is wound on the stationary member or stator. The principal
advantages of the revolving-field generators over the revolving-armature generators are
two essential parts of a dc generator: are as follows: The yoke and field windings, which
are the load current from the stator is stationary, and connected directly to the external
circuit the armature, which rotates without using a commutator.
3.1 GENERATOR:-
ADV850M55, 27.778MVA, 25MW,11kV ±15% 3-Ø, 50 Hz, 1458 Amp., 0.9 p.f. lag, 40
poles, 150 rpm., run away speed 350 rpm,11.55 kV max.-10.45 kV min.
* Air gap at pole center- 20 mm.
* Stator resistance per phase (at 20°c) - 0.0182 
* Stator connection- STAR.
* Field winding resistance (at 20°c) -0.08534 
* Flywheel effect of generator (GD)² –3.4*10ˆ6 kg m²
* Synchronize reactance (Xd) -0.789 p.
* Transient reactance Xd (sat.) – 0.265 p.v.
* Sub transient reactance Xd´ (sat.) – 0.183 p.v.

* S/C ratio – 1.33
* Excitation at no load rated voltage – 745 amp.
* Max. I²t -154722/19
* Excitation at rated voltage -1217 amp.
* S/R brushes –total 30 no. (15 per ring)
* Brushes size – 25.4*38.1 mm.
* Brushes grade – Moge
* Brushes force – 1.7 kg.
3.1 STATOR:
The stator core and winding are housed in a fabricated steel frame made in four sections.
The stator core is built of vanished segmental silicon steel laminations held in the frame by
dovetailed key bars, welded to the frame. The core is divided into the packets by narrow
radial steel spears, thus forming ventilating ducts leading from the stator core to the
outside periphery. The core is clamped between the bottom frame plate and segmental
flanges on the top by means of through bolts.
The stator winding is of the double layer three turned diamond pulled coil type, assembled
in open slots. Each coil is made of a number of insulated copper strands, with a semi-rebel
transposition in the end of Epoxy Movolac glass Mica paper tapes and flexible Mica flakes
taps in the end winding. All the coils are identical and interchangeable. Temperature
sensors of resistance type are inserted between coil sides in all three phases to provide a
continuous indication of coil temperature.
3.2 ROTOR:
The rotor is of the friction held type and is built up of thin sheet steel laminations rigidly
clamped between steel and plates by a large number of through bolts. The clamping force
in the rim is such that the fractional forces between the laminations prevent them from
slipping relative to one another at any speed up to and including runway. The spider which
supports the rim is of fabricated steel construction with dished arms from a central hub.
The lower plane is machined to fit on top of the generator shaft. The driving torque is
transmitted from the shaft to the spider by radial keys. This method of construction

permits the lifting of rotor independent of the shaft. The weight of the rim and poles is
supported on the heavy steel bars welded on the outer end of the spider arms. Each pole
carries a field coil made from straight lengths of copper straps, dovetailed and brazed at
the ends. At intervals down each coil, the copper is increased in width to from fins for
improved cooling. The inter turn insulation is of epoxy resign bonded asbestos paper and
the insulation between the coil and pole body is epoxy glass fabric bored. In addition, each
pole is equipped with six damper bars of circular cross section made of high conductivity
copper embedded in semi-closed slots in the pole face, which are brazed at each end into
copper punching clamped between pole and end plates. Axial flow aero-fill type fans are
mounted at each end of the rotor. A polished steel segmental brake track is bolted to the
bottom of the spider hub.
3.3 VENTILATION:
The generator has a closed circuit system of ventilation. Four twin sets of air coolers are
located at the corners of generator housing and the cooled air is discharged into the space
between the coolers and generator barrel from which part of this air will then return to fan
below the rotor through. The ducts in the foundation below the air coolers and the
remainder of the cooled air will return to the fan above the rotor. The air is then circulated
through the closed system by the combined action of the rotor poles and of the fans. The
fan consists of a large number of specially shaped Aluminum blades. The fans are
surrounded by suitable shaped air guides to ensure proper distribution of air.
The exciter has a separate centrifugal fan mounted above commutator for cooling the
exciter and collector. The water supply to each of the air coolers is controlled by separate
valves so that any one of the coolers can be isolated, if necessary. The inlet and outlet
connections are made to the bus pipes running around the machine.
3.4 AIR COOLER:
Each of the twin shades of air coolers consists of a nest of admiralty Brass cubes wound
with copper wire covered in a mild steel frame. The tube ends are roller expanded into
Brass plates on which are mounted the inlet and return end water boxes fabricated from
mild steel. The thickness of water box includes generous corrosion allowance and these
are internally subdivided to provide for multiple water passes for requisite flow pattern.
The inlet water box is filled with vent valve and with drain valve. The differential thermal

expansion between tubes and frame is absorbed by the action of neoprene packing
between the frame and the tube plate. The coolers are provided with support foot plates at
the bottom for baling down to the concrete foundations. A drip tray is provided below the
cooler for collecting any condensate.
3.5 OIL COOLER
Each of the four plug-in-type oil coolers consists of a bank of 'U' shapes admiralty Brass
tube with Copper wire carried in a Steel frame with inlet end terminating in a rolled Brass
tube plate and the other 'U' end supported in a tube support fixed frame. The tube rollers
expanded into the tube plate. The water box which is of mild steel fabrication is belted to
the tube plate and amply proportional to reduce turbulence and pressure drop. The
differential thermal expansion between tube and frame is absorbed by the 'U' shaped tubes.
3.6.0BEARINGS: -
Thrust bearing type –spring matters supported:
» Guide bearing type – Pivoted type
» Normal operating temperature of bearing pads:60°c
This type of Bearing is taking the whole machinery weight. It located at below the rotor-
stator frame housing of core &winding. It has construction of four sectional steel frames.
3.6.1 SHAFT AND THRUST BLOCK:
The generator shaft and thrust block is a one piece steel forging. The bottom surface of
the thrust block forms rotating thrust bearing surface and is machined to be accurately
perpendicular to the axis of the shaft. It is ground to an optical finish. The journal surface
is machined and ground on the circumference of the thrust block. Over the top of support
into the reservoir. The air space above the oil surface is vented to atmosphere by means of
an oil vapor seal fitted to prevent the escape of oil vapor into the generator air circuit.
The bearing parts are self lubricated. The hot oil coming out of the bearing is cooled by
means of oil to water heat exchangers inserted into the bearing housing itself. The cool oil
will again sucked by rotating parts of the bearing. During starting when the hydro-
dynamic oil film is not likely to be formed, provision is made to inject oil at high pressure

through the thrust pads. The system is designed to come into operation automatically on
starting and also stopping the machine. The thrust bearing housing is designed to give the
best possible accessibility to the thrust bearing. Openings with removable covers are
provided in the wall of housing, so that the thrust pads and the thrust face can be inspected
after the housing has been drained and the rotor jacked up. A special tackle is provided to
enable the thrust pads to be withdrawn through the openings, if necessary. It is possible to
inspect the pads and spring units without dismantling the bearing or removing the
generator rotor. It is used to prevent the bubbling of rotor. It situated at D.C. exciter
portion or PMG part.
Fig-3.1 SHAFT
3.6.2 THRUST AND GUIDE BEARING ASSEMBLY:
The thrust bearing of the spring supported type in which the stationary part consists of
white metal segmental thrust pads supported on mattress of helical springs. The bearing

operates immersed in oil.The thrust pads are stress relieved mild steel and are paced with a
high quality white metal. Each pad rests on pre-compressed spring finished to standard
overall length. The springs are assembled on a heavy steel spring plate which is fixed to
the bottom bracket by screws and dowels. The thrust pads are prevented from rotation by
means of pad stop secured to the spring plate. Radial movement of the pads is prevented
by dog clamps which also prevents them from rising with the thrust collar when jacking
up the rotor. The guide bearing comprises white metal faced pads arranged inside a
cylindrical support in the thrust bearing housing and bearing on a journal surface
machined on the thrust collar.
Fig-3.2 GUIDE BEARING
A pivot bar double curvature is screwed to the back of each guide bearing pad, to enable
the pad to rock slightly to take up a suitable position and to facilitate the formation of the
oil film when running. The clearance between individual pads and pivot bar. The lower
part of the plates are permanently immersed, in oil and by centrifugal action, the oil is
pumped between the pads and spills.

3.6.3 THRUST AND GUIDE BEARING BRACKET:
The thrust and guide bearing bracket below the rotor is a fabricated bridge type
construction. It is designed to support the hydraulic thrust form the turbine in addition to
the weight of the rotating parts of the generator and turbine. The bracket arms rest on sole
plates grouted into the concrete foundation. Shims are provided for leveling purpose. Jack
screws are provided for using leveling and centering the whole bracket. Sheet covers are
bolted to the underside of the bracket seal and machine enclose from the turbine pit. The
complete bracket is designed such that it can be lifted through the stator bore.
3.6.4 TOP BRACKET:
The top bracket is also of fabricated steel construction and support the stationary part of
the PMG, brush gear and DC exciter. The bracket arm rest on machined facings at the top
of stator frame and shims are provided for leveling purpose. Jacking screws are provided
for adjusting the bracket during leveling and centering. The bracket also supports the steel
flooring on top generator pit.
3.6.5 BRAKES AND JACKS:
Fig- 3.3 OIL PRESSURE PUMP

The generator equipped with combined brake and jack units on the lower bearing bracket.
They are designed to operate on air pressure as brakes and with high pressure oil as jacks
for raising the rotor. A portable high pressure oil pump is furnished to supply the
necessary high pressure oil for jacking. In order that the rotor might be held in the raised
position for an extended period of time, a locking device is provided on the brake units.
Each brake is provided with a limit switch. The brakes are capable of bringing the unit to a
dead stop from 33% speed within 5 min with the turbine gates closed and without field
excitation.
3.6.6 H.S. LUBRICATION FOR THRUST BEARING:
It is large size of bearing at middle of the machinery. It connects to generator &
turbine part. It is oil filled for cooling purpose, it also used as lubricant. For oil film
generate H.S. Lub (High Sped Lubrication) motor.(H.S. Lub Motor figure) It is oil filled,
water cooled, air cooled fully packed chamber & oil pressure (40 kg.) adopted bearing.
Maintain of 40 kg. Pressure by two 5 HP (Horse Power), 120 kg. weighted Induction
Motor’s. Each motor can generate to 40kg pressure but both running at a time for safety
point of view. Each 25-25 MW units we use that pair of motors different. They will run in
whole generation of power.

Fig- 3.4 H.S. LUBRICATION MOTOR
BRAKE & JACK: -
Polished steel segmental to the button of spider hub.
SHAFT & THRUST BLOCK:-
Thrust bearing type “Spring supported”.
THRUST PADS: -
Stress relieved mild steel faced length high quality White metal.
THRUST & GUIDE BEARING BRACKET: - Fabricated bridge Type.
TOP BRACKET: - Fabricated steel-PMG, brush gear.
BRAKES &JACKS:-Brake air pressure-4 kg/cm², recently -7 kg/cm².
PMG:- 3-Ø Low voltage, supply to turbine govern at a frequency directly related to
the speed of the set.

H.S.Lub:- Oil film unit between the thrust body and the runner during start/stop.
(Hydro-dynamic oil film).This will take the whole weight & Balance of Shaft & connected
equipments.
3.7 Analysis of industrial oils and greases:-
Many different oils and greases are used in industry, including fuel oils, engine
oils, lubricating oils and hydraulic oils. We analyses industrial oils from all sorts of plants,
including mechanical and rotating, moving plant / vehicles, hydraulic systems, pumps,
engines and bearings. When analyzing industrial oils, we first look at the quality of the oil
to ensure it is the correct oil and that it is doing its job. If not, we look at the potential to
'repair' oil via additives, etc.Industrial oils can also be used to ascertain equipment
condition, maintenance requirements and diagnose faults. This is possible because oil, like
blood, flows freely in plants, picking up information on its journey, and oil analysis can
unlock this information. Techniques employed include microscopic analysis of wear
metals and particles in the oil, ICP (plasma), spectroscopy (emissions), infrared, ferro-
graphy, etc.

Fig-3.5 GREES PRESSURE UNIT

CHAPTER-4
Automatic Voltage Regulator
Automatic Voltage Regulator: [ A V R ]
AVR type V × B 32 automatically regulate the output voltage of the generator by
providing it with a controlled field supply via an exciter generator. The equipment is
active over the whole load range with negligible dead band. Other facilities in addition to
generator output voltage regulation. Manual control of excitation is available in the event
of failure of automatic control. The basic system as shown in figure consists of a closed
loop generator voltage control employing a thyristor converter. Output stage and an open
loop manual control of excitation and when necessary potentiometer 70 volts set the
required generator output voltage. The output of manual circuit is single phase full wave
rectifier DC voltage
The auto control output is a full controlled thyristor converter fed on a single
phase AC supply. The converter output is the exciter field current. The converter output
level is determined by the thyristor control signal regenerated as already described. The
manual control stage is a diode bridge fed from a manually controlled single phase auto
transformer whereas of a step down transformer. The auto change over contactor select the
output from the thyristor converter or from the diode bridge as the late may be.
Fig:- AVR Panel

4.1WORKING OF AVR:
Relays may be fitted with a variety of contact systems for providing electrical
outputs for tripping and remote indication purposes. The most common types encountered
are as follows:
(a). Self-reset
The contacts remain in the operated condition only while the controlling quantity is
applied, returning to their original condition when it is removed.
(b). Hand or electrical reset
These contacts remain in the operated condition after the controlling quantity is
removed. They can be reset either by hand or by an auxiliary electromagnetic element.
The majority of protection relay elements have self-reset contact systems, which, if
so desired, can be modified to provide hand reset output contacts by the use of auxiliary
elements. Hand or electrically reset relays are used when it is necessary to maintain a
signal or lockout condition. Contacts are shown on diagrams in the position corresponding
to the un-operated or de-energized condition, regardless of the continuous service
condition of the equipment. For example, an under voltage relay, which is continually
energized in normal circumstances, would still be shown in the de-energized condition. A
'make' contact is one that closes when the relay picks up, whereas a 'break' contact is one
that is closed when the relay is de-energized and opens when the relay picks up.
A protection relay is usually required to trip a circuit breaker, the tripping
mechanism of which may be a solenoid with a plunger acting directly on the mechanism
latch or an electrically operated valve. The power required by the trip coil of the circuit
breaker may range from up to 50 watts for a small 'distribution' circuit breaker, to 3000
watts for a large, extra-high voltage circuit breaker.
The relay may therefore energize the tripping coil directly, or, according to the coil
rating and the number of circuits to be energized, may do so through the agency of another
multi-contact auxiliary relay. The basic trip circuit is simple, being made up of a hand trip
control switch and the contacts of the protection relays in parallel to energize the trip coil

from a battery, through a normally open auxiliary switch operated by the circuit breaker.
This auxiliary switch is needed to open the trip circuit when the circuit breaker opens since
the protection relay contacts will usually be quite incapable of performing the interrupting
duty. The auxiliary switch will be adjusted to close as early as possible in the closing
stroke, to make the protection effective in case the breaker is being closed on to a fault.
Where multiple output contacts or contacts with appreciable current-carrying capacity are
required, interposing, contactor type elements will normally be used. In general, static and
microprocessor relays have discrete measuring and tripping circuits, or modules. The
functioning of the measuring modules is independent of operation of the tripping modules.
Such a relay is equivalent to a sensitive electromechanical relay with a tripping contactor,
so that the number or rating of outputs has no more significance than the fact that they
have been provided. For larger switchgear installations the tripping power requirement of
each circuit breaker is considerable, and further, two or more breakers may have to be
tripped by one protection system. There may also be remote signaling requirements,
interlocking with other functions (for example auto-re-closing arrangements), and other
control functions to be performed. These various operations may then be carried out by
multi-contact tripping relays, which are energized by the protection relays and provide the
necessary number of adequately rated output contacts.

CHAPTER-5
TURBINE
TURBINE:
Each of vertical shaft Francis type turbine comprises of a shaft tube, spiral casing
,and stay ring, guide apparatus, shaft ,runner, guide bearings ,shaft seal and ancillary
item, The turbine equipment for each unit includes one electro hydraulic governor and oil
pressure unit. The machine has been designed to run has synchronous condenser also by
depressing the water in the runner chamber. Further descriptions of the major component
of the turbine are given as below.
5.1 DRAFT TUBE:
The draft tube consists of cone and knee liner. The draft tube cone consists of
upper cone and lower cone which is further split into equal halves for transportation
facility. The top segments of upper cone made of stainless steel plate and are welded.
To mild steel plate in the bottom portion. An allowance of 50 mm is kept in the
total height of the cone so as to maintain the elevation and level of total flange of upper
cone. The top flange of upper cone supports runner with shaft on it when it is decoupled
from generator shaft. A trapping for vacuum gauge is provided on it. Machine door is
provided in upper cone for providing access to runner is assembled condition.The test
cock is provided below the main whole door to check the water level before opening the
main whole door. The draft tube knee liner is of welded structural steel construction and
rigidly held in concrete with help of anchors and turn buck-less. Leveling bolts have been
provided at the base of knee liner for leveling it during installation. The top draft tube knee
liner is welded to lower cone at site. Drainage box with removable grill is provided on
the draft tube concrete wall. Drainage wall is connected to draft tube drain valve. It is
placed in dewatering pit and can be operated from floor at elevation 227.0 m.
The leakage water from shaft seal and middle journal of guide vane, is connected
inside to cover and drained through stay vane hales. Additional facility is provided for
automatic draining of top cover through ejector in case level of water rises in top cover.
For measuring top cover pressure a tapping is provided which is further connected to

pressure gauge. The pivot ring houses the lower bush for lower steam of guide vane, It is
fabricated in to pieces and attached to stay ring along guide vane P C D.
Top face of pivot ring is provided with belted stainless steel is provided with
bolted stainless steel plate. Lower labyrinth is also bolted with pivot ring. Four tapped
holes are provided, in pivot ring for measuring the labyrinth deceases. Hales are plugged
with both upper and lower labyrinth rings are machined to provide 1.2 to 1.5 mm
clearance to runner. The guide vanes are case solid from cast steel. The upper and middle
journals sheets, kept pressed by distance ring and cover plate against stainless steel sleeve
bolted on shaft.The branch pipe line also has flow switch with electrical contacts for low
flow alarm and starting inter lock and a tapping for pressure gauge. The shaft sealing can
be inspected are repaired when the runner is stationary by applying isolating seal located
at the bottom of housing. It comprises of a wedge sectioned, nitrite rubber ring normally
held clear of the shaft.
5.2 SPIRAL CASING & INLET PIPE:
It is a welded construction from bailer quality steel plates. It is of logarithmic form
and circular cross section to maintain a constant velocity throughout its length. The plates
are gradually reduced in thickness to suit the load and shop welded to each other in group
of two to four segments considering ease of handling & transport limitations. Three make
up segments are supplied with fitting allowances which are to be welded after making
proper edge preparation for site welding as shown in dewatering.The spiral casing at inlet
section is welded to inlet pipe at site. The inlet pipe is provided with fitting allowances for
welding it to the penstock. The spiral casing has all necessary lifting lugs, feet, pads, eyes
belts, and jacking screw for leveling during erection.
5.3 RUNNER:
The runner is cast stainless steel with stream lined vanes and complete with central
coupling flange for coupling with the shaft. The runner is provided with top and bottom
labyrinth rings. These rings are accurately machined to give 1.2 to 1.5 mm clearance with
labyrinth rings in top cover and pivot ring. The runner cone is fabricated from steel plates
in one piece. It has fit in the recess on the face of runner coupling flange held in position
by studs and nuts. On coupling flange 12 unloading holes are provided for balancing the

pressure on the upper & lower side of runner. The runner is statically balanced in the
works.
Fig- 5.1 FRANCIS TURBINE “RUNNER”.
5.4 TURBINE SHAFT:
The turbine shaft is of forged steel with forged bearing skirt and coupling flanges.
It is bored throughout the length to ascertain soundness. The shaft is coupled to the
generator shaft by fitted bolts. The coupling holes in runner end of turbine shaft and
runner are accurately drilled using special jig to achieve interchangeability of runner.The
bearings surfaces is fine machined and polished and the shaft is aligned with generator
shaft at works. A fine machined band is provided on the shaft for checking alignment at
site. Stainless steel sleeve is bolted on the shaft for providing wearing surfaces for shaft
seal.

5.5 SHAFT SEALING:
The shaft sealing prevents leakage of water through clearance between shaft and top
cover.
It is located below turbine guide bearing and supported on the top cover by bolts. The
sealing elements are in two layers of sealing ring in the form of rubber. Applied when
required through isolating valve. The seal is released through isolating valve. The seal is
released through isolating valve.
5.6 GUIDE BEARING:
The guide bearing is pivoted pad type with self contained oil bath lubrication and
external oil coolers. It consists of 8 Babbitt lines pads arranged along the outer
circumference of skirt of the shaft .Each pad is adjustable by means of lockable screw
bearing on thrust disc at the back of pad and is kept pivoted against spherical ends of the
studs. The bearing body is bolted with top cover. The centre piece located inside shaft
caller is built up by welding and matching around the shaft. Under stationary condition,
the pads are kept immersed in oil bath approximately up to centre line of bearing when the
shaft rotates, the oil flows through the holes in the skirt due to centrifugal force and rises
along the bearing body lubricating pads.
The guide bearings comprise of two chambers, chamber 1 is cool oil which is
inside the shaft and in lower portion. Chamber 2 is outside the skirt of shaft around the
pads and it consists of hot oil. The flow of oil from chamber 1 to chamber 2 takes place
through hale provided on the skirt of the shaft. The difference between the oil level in
chamber 1 and chamber 2 is the total energy available which assume the circulation of oil
from chamber 2 of guide bearing to the oil cooler and back from oil cooler remains in
between to two oil level in the chambers of guide bearing. The oil cooler is out side the
generator barrel in a pit and is connected to the guide bearing by oil pipes.
A visual oil level indicator and two level relays with electrical contacts are
provided on the oil tank for cooler for indicating the oil level in the guide bearing and for
monitoring high and low level the procedure for setting the levels is given on the above
referred drawing. The exact limit of oil level is to be decided after the mechanical run of
the machine. Oil levels on the coolers can be regulated by means of plugs provided in
holes of skirt of shaft.

Guide bearing temperature is monitored by two thermometers with alarm and trip
contacts and two RTD‟s for temperature recordings on the turbine gauge panel. RTD
monitors the guide bearing oil temperature. Pad and oil temperature are set to operate an
alarm at 5˚cabove normal and trip at 10˚c above normal temperature.
5.7 GUIDE VANE SERVOMOTERS:
Two servomotors are provided for turning the regulating ring. They are identified
as:
1. Guide vane servomotor with stopper.
2. Guide vane servomotor without stopper.
Fig- 5.2 PRESSURE PUMP & SERVOMOTOR.
Each servomotor comprises of, basically a cylinder housing a cast iron piston, with cast
iron piston rings to minimize the leakage thorough it. The end faces of the cylinder are
closed with the help of covers through one of which the sleeve is provided by rubber cup
sealings. The piston rod is made in two parts which are connected together with a turn
buckle having right hand possible to adjust the length of the piston rod by rotating the turn
buckle. Lock nuts are provided on its both ends for locking the position of turn buckle
after its final setting.

Near the end of its stroke for closing, the piston is decelerated by throttling the oil through
special vanes. These vanes protected the system from impact and hydraulic hammer. The
oil drained into the tank of oil leakage unit. Emptying of servomotor is also carried out
through the oil leakage unit. A scale has been provided on servomotor with stopper on
which the servo stroke is indicated. One tapping each in opening and closing pipe line
provided for connecting to pressure gauge.
Stopper is provided on servomotor to hold the guide vanes is closed position. The
stopper is provided with contact switches to indicate closed or open position on the panel.
The stopper is designed for hydraulic load which may occur in closed position of guide
vane. No pressure is allowed inside the servomotor when stopper is closed.
5.8 FEED BACK CONNECTION:
The feedback mechanism is intended for the restoration of the governor main slide
valve to the mean position in the process of governing the guide vane servomotor. It
consists of rope drive, which transmits the moments of servomotor connecting rod through
the system of rollers to the main slide valve. On the feedback gear a motor switch is also
installed.
5.9 EJECTOR:
The ejector system is used for automatic draining of top cover as an additional
facility over normal gravity draining through holes in two stay vanes. For this purpose
high pressure water tapped from penstock is passed through an ejector, which sucks water
from top cover, and discharge in gutter from where it goes in drainage pit.

5.10FLOWMETER:
Fig:- 5.3 Flow Meter
The measuring turbine discharge suitable tapping points are provided on spiral casing. The
general scheme for the measure meant for these measurements is as. The electronics
differential pressure transmitter with transducer is suitable for measuring static or dynamic
fluid pressure. The two pressure p1 and p2 are applied the diaphragm of the pressure
transducer. The differential pressure transducer converts the fluid pressure into electrical
signal utilizing for strain gauge, bonded on one side diaphragm, arranged in form of
Wheatstone bridge.
5.11 VACCUM BREAKING VALVES:
These valves are mounted on top cover with an isolating valve. These will be use
supplying air under ATM pressure below the top cover to break the vacuum in case of
sudden closer of guide apparatus; these are spring loaded valve and oil pipe lines and
periodic pumping of the oil to the sump of oil pressure unit. The oil leakage unit consists
of a tank and mounted on it is a pump and electric motor in the tank a level relay is
mounted for automatic controlling of the pump and alarm check.

5.12 OIL LEAKAGE UNIT:
It is intended for collection of oil leakage from servomotors for draining oil from
servomotor, controlling valves and oil pipe lines and periodic pumping of the oil to the
sump of oil pressure unit. The oil leakage unit consists of a tank and mounded on it is a
pump electric motor in the tank a level relay is mounted for automatic controlling of the
pump and

CHAPTER:-6
POWER TRANSFORMER
6.1 TRASNFORMER CONSTRUCTION:
There are two basic types of core assembly, core form and shell form. In the core
form, the windings are wrapped around the core, and the only return path for the flux is
through the center of the core. Since the core is located entirely inside the windings, it
adds a little to the structural integrity of the transformer‟s frame. Core construction is
desirable when compactness is a major requirement. Figure Z-6 illustrates a number of
core type configurations for both single and multi-phase transformers.
Fig:- 6.1 Core Type Transformer

Fig:-6.2 Power Transformer
This manu-aclontaions a generalized overview of the fundamentals of transformer
theory and operation. The transformer is one of the most reliable pieces of electrical
distribution equipment. It has no moving parts, requires minimal maintenance, and is
capable of withstanding overloads, surges, faults, and physical abuse that may damage or
destroy other items in the circuit. Often, the electrical event that burns up a motor, opens a
circuit breaker, or blows a fuse has a subtle effect on the transformer. Although the
transformer may continue to operate as before, repeat occurrences of such damaging
electrical events, or lack of even minimal maintenance can greatly accelerate the evenhml
failure of the transformer.
The fact that a transformer continues to operate satisfactorily in spite of neglect
and abuse is a testament to its durability. However, this durability is no excuse for not
providing the proper care. Most of the effects of aging, faults, or abuse can be detected and
corrected by a comprehensive maintenance#and#testing#program.

Fig.6.3 Transformer Tank With Vaccume Filling
6.2 COSERVATOR TANK:
Conservator or expansion type tanks use a separate tank to minimize the contact
between the transformer oil and the outside air (see figure). This conservator tank is
usually between 3 and 10 percent of the main tank‟s size. The main tank is completely
filed with oil, and a small conservator tank is mounted above the main tank level. A sump
system is used to connect the two tanks, and only the conservator tank is allowed to be in
contact with the outside of transformer oil flow.
[A]. By mounting the sump at a higher level in the conservator tank, sludge and water can
form at the bottom of the conservator tank and not be passed into the main tank. The level
in the main tank never changes, and the conservator tank can be drained periodically to
remove the accumulated water and sludge.

Fig:-6.4 Conservator Tank In Transformer
[B]. Although this design minimizes contact with the oil in the main tank, the auxiliary
tank‟s oil is subjected to a higher degree of contamination because it is making up for the
expansion and contraction of the main tank. Dangerous gases can form in the head space
of the auxiliary tank, and extreme caution should be exercised when working around this
type of transformer. The auxiliary tank‟s oil must be changed periodically, along with a
periodic draining of the sump.
6.3 TRANSFORMER OIL TESTING:
Oil is analyzed from high voltage electrical systems and plant, including
generators, transformers, switchgear and cables that contain insulating oil. Aside from
power stations and electricity distributors, many large industrials have their own high

voltage network that can benefit from oil analysis. Train operators and airports are other
examples of users.
Fig:-6.5 Transformer Oil Testing
Basic tests are used to look at the oil's quality; they include testing for water, acidity,
electric strength, resistively, color, fibers, odors and oxidation. To evaluate the condition
of the plant from the oil, more complicated techniques of high-pressure liquid and gas
chromatography are used to determine the combination of gasses and debris in the oil.
[A]. Insulating fluid plays a dual function in the transformer. The fluid helps to draw the
heat away from the core, keeping temperatures low and extending the life of the
insulation. It also acts as a dielectric material, and intensifies the insulation strength
between the windings. To keep the transformer operating properly, both of these qualities
must be maintained.
[B].The oil‟s ability to transfer the heat, or its “thermal efficiency,” largely depends on its
ability to flow in and around the windings. When exposed to oxygen or water, transformer
oils will form sludge and acidic compounds. Sludge deposits restrict the flow of oil around

the winding and cause the transformer to overheat. Overheating increases the rate of
sludge formation (the rate doubles for every 10 “C rise) and the whole process becomes a
“vicious cycle.”
[C]. The oil‟s dielectric strength will be lowered any time there are contaminants. If leaks
are present, water will enter the transformer and condense around the relatively cooler
tank walls and on top of the oil as the transformer goes through the temperature and
pressure changes caused by the varying load. Once the water condenses and enters the oil,
most of it will sink to the bottom of the tank, while a small portion of it will remain
suspended in the oil, where it is subjected to hydrolysis. Acids and other compounds are
formed as a by-product of sludge formation and by the hydrolysis of water due to the
temperature changes.
[D]. The two most detrimental factors for insulating fluids are heat and contamination. The
best way to prevent insulating fluid deterioration is to control overloading (and the
resulting temperature increase), and to prevent tank leaks. Careful inspection and
documentation of the temperature and pressures level of the tank can detect these
problems before they cause damage to the fluid. However, a regular sampling and testing
routine is effective tool for detecting the onset of problems before any damage is
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6.4 BUSHINGS:
Theleads from the primary and secondary windings most be safely brought through the
tank to form a terminal connection point for the lie and load connections. The bushing
insulator is constructed to minimize the stresses at these points, and to provide a
convenient connection point. The bushing is designed to insulate a conductor from a
barrier, such as a transformer lid, and to safely conduct current from one side of the barrier
to the other. Not only must the bushing insulate the live lead from the tank surfaces, but it
must also preserve the integrity of the tank‟s seal and not allow any water, air, or other
outside contaminants to enter the tank.

Fig:- 6.6 Bushing
[A]. There are several types of bushing construction; they are usually distinguished by
their voltage ratings, although the classifications do overlap:
1. Solid (high alumina) ceramic-(up to w5kv).
2. Porcelain-oil filled (25 to 69Kv).
3. Porcelain-compound (epoxy) filled (25 to 69kV).
4. Porcelain--synthetic resin bonded paper-filled (34.5 to 115kV).
5. Porcelain-oil-impregnated paper-filled (above 69kV, but especially above 275kv).

[B]. For outdoor applications, the distance over the outside surface of the bushing is
increased by adding “petticoats” or “watersheds” to increase the creep age distance
between the line terminal and the tank. Contaminants will collect on the surfaces of the
bushing and form a conductive path. When this creep age distance is bridged by
contaminants, the voltage will flashover between the tank and the conductor. This is the
reason why bushings must be kept clean and free of contaminants.
[C]. Transformer bushings have traditionally been externally clad in porcelain because of
its excellent electrical and mechanical qualities. Porcelain insulators are generally oil-
filled beyond 35 kV to take advantage of the oil‟s high dielectric strength. There are a
number of newer materials being used for bushings, including: fiberglass, epoxy, synthetic
rubbers, Teflon, and silica compounds. These materials have been in use for a relatively
short tile, and the manufacturer‟s instructional literature should be consulted when
working with these bushings.
[D].Maintenance. Bushings require little maintenance other than an occasional cleaning
and checking the connections. Bushings should be inspected for cracks and chips, and if
found, should be touched-up with Glyptic paint or a similar type compound. Because,
bushings are often called on to support a potion of the line cable‟s weight, it is important
to verify that any cracks have not influenced the mechanical strength of the bushing
assembly.
[E]. Testing. Most bushings are provided with a voltage tap to allow for power factor
testing of the insulator. If they have no tap, then the power factor test must be performed
using the “hot collar” attachment of the test set. The insulation resistance-dielectric
absorption test can also be performed between the conductor and the ground connection.
6.5 LIGHTNING (surge) ARRESTERS:
Most transformer installations are subject to surge voltages originating from lightning
disturbances, switching operations, or circuit faults. Some of these transient conditions
may create abnormally high voltages from turn to turn, winding to winding, and from
winding to ground. The lightning arrester is designed and positioned so as to intercept and
reduce the surge voltage#before#it#reaches#the#electrical#system.

Fig:-6.7 Lightining Arresters
[A]. Construction. Lightning arresters are similar to big voltage bushings in both
appearance and construction. They use a porcelain exterior shell to provide insulation and
mechanical strength, and they use a dielectric filler material (oil, epoxy, or other materials)
to increase the dielectric strength (see Figure). Lightning arresters, however, are called on
to insulate normal operating voltages, and to conduct high level surges to ground. In its
simplest form, a lightning arrester is nothing more than a controlled gap across which
normal operating voltages cannot jump. When the voltages exceeds a predetermined level,
it will be directed to ground, away from the various components (including the
transformer) of the circuit. Some arresters use a series of capacitances to achieve a
controlled resistance value, while other types use a dielectric element to act as a valve
material that will throttle the surge current and divert it to ground.

[B]. Mechanism.Lightning arresters use petticoats to increase the creep age distances
across the outer sm. face to ground. Lightning arresters should be kept clean to prevent
surface contaminants from forming a flashover path. Lightning arresters have a metallic
connection on top and bottom. The connectors should be kept free of corrosion.
[C]. Testing. Lightning arresters are sometimes constructed by stacking a series of the
capacitive/dielectric elements to achieve the desired voltage rating. Power factor testing is
usually conducted across each of the individual elements, and, much like the power factor
test on the transformer‟s windings, a ratio is computed between the real and apparent
current values to determine the power factor.

6.6 CURRENT TRANSFORMER’S:
Fig:-6.8 Current Transformer
(A) CONNECTION’s
(B) TOP VIEW OF C.T.
(C) POSITION ON TRANSFORMER (Location)
(D) C.T. OPEN FOR MENTINANCE
The primary winding of a current transformer is connected in series with the power circuit
and the impedance is negligible compared with that of the power circuit. The power
system impedance governs the current passing through the primary winding of the current
transformer. A current transformer is specified as being 600 A, 5 A class C200. Determine
its characteristics. This designation is based on ANSI Std. C57.13–1978. 600 A is the
continuous primary current rating, 5 A is the continuous secondary current rating, and the
turns ratio is 600/5=120. C is the accuracy class, as defined in the standard. The number
following the C, which in this case is 200, is the voltage that the CT will deliver to the
rated burden impedance at 20 times rated current without exceeding 10 percent error.
Therefore, the rated burden impedance is This CT is able to deliver up to 100 A secondary
current to load burdens of up to 20 with less than 10 percent error. Note that the primary

source of error is the saturation of the CT iron core and that 200 V will be approximately
the knee voltage on the CT saturation curve.
A typical wye CT connection is shown in Fig. The neutral points of the CT‟s are tied
together, forming a residual point. Four wires, the three-phase leads and the residual, are
taken to the relay and instrument location. Additional relays are often connected in the
residual, as the current in this circuit is proportional to the sum of the phase currents.
Fig:-6.9 Typical setup for wye-connected CT’s protecting a line or piece of equipmen
6.7 TRANSFORMERCOOLING;-
6.7.1 WATER COOLING(SPRINKLER):-
This type of cooling system pressure pumps used for water pressure flow. At cooling place
use pipe lines with sprinkler equipment as shown in figure.

Fig:-6.10 Water Sprinkler System For Cooling Substation
6.7.2 CO2 SPRINKLER:- This system use at around the transformer for fir-fighting.
The color of the pipes is Yellow painted. At nosel of the pipe, glass flask filled
with either. When burn or temperature rise of the transformer flask will blast and
CO2 spray on transformer for safety.

CHAPTER-7
PUMPS
PUMPS:
Circulate cooling water for coolers and condensers,#pump#out bilges,#transfer fule
oil,supply water#to the distilling plants, and are used for many
other purposes. The operation of the plant and of almost all the auxiliary machinery
depends on the proper operation of pumps Although most plants have two pumps, a main
pump and a standby pump, pump failure may cause failure of an entire power plant.
If they fail, the power plant they serve also fails. In emergency an, pump#failures
can prove disastrous.#Maintaining pumps in an efficient working order is a very important
task of the engineering department. The pumps with which you are primarily concerned
are used for such purposes as circulating lubricating (lube) oil to the bearings and gears,
supplying water for the coolers, transferring fuel oil to various storage and service tanks.
Centrifugal pumps of various sizes are driven by electric motors to move different types of
liquid. The fire pump and water service pump are two examples of this type of pump.
7.1 PUMP#CLASSIFICATION#&#CONSTRUCTION:
Centrifugal pumps may be classified in several ways. A single-stage pump has only
one#impeller,#a multistage pump#has two or more#impellers housed together#in one#casi
ng. In a#multistage#pump, each impeller usually actsseparately, discharging to the suction
of the next-stage impeller. Centrifugal pumps are also classified as horizontal or vertical,
depending on the position of the pump shaft. Impellers used in centrifugal pumps may be

classified as single-suction or double-suction, depending on the way in which liquid enters
the eye of the impeller. The double-suction arrangement has the advantage of balancing
the end thrust in one direction with the end thrust in the other direction. Impellers are also
classified as CLOSED or OPEN. A closed impeller has side walls that extend from the eye
to the outer edge of the vane tips; an open impeller does not have side walls.
CENTRIFUGAL PUMPS SPECIFICATION:-
Fig:- 7.1 CENTRIFUGAL PUMPS SPECIFICATION

CHAPTER-8
SWITCHYARD
SWITCH YARD
8.1 ISOLATORS:-
An isolator is one which comes brake the electric circuit when the circuit to be switched
on no load these are normally used in various circuits for the purpose of isolation for a
certain portion required for maintenance.
SWITCHING ISOLATORS:- They are capable of-
1) Interrupting transformer magnetizing currents.
2) Interrupting charging currents.
3) Load transformer switching.
The main application is in connection with feed or bank transformer feeders. This unit
makes it possible to switch out one transformer while the other is on still load.

8.2 CIRCUIT BREAKERS:-
A circuit‟s breaker is a device that can make or break circuit on load & even on faults, this
is most important and heavy duty equipments moving utilized for protection of various
circuit and separation at load. The circuit breaker is a switch yard is installed on movable.
It is tripped by relay of by a manual signal. The CB used in switch gear. now a days are
minimum oil circuit breaker, oil circuit breaker, vacuum CB and other types are used in
the switch gear the required from the CB is such that it should be compare to
* carry continuously minimum current of the system at P.B. of installation.
* make & break circuit under normal working condition.
8.2.1 OIL CIRCUIT BREAKERS:
Oil circuit breakers are used for transmission voltages up to 300kV, and can be subdivided
into the two types: „bulk oil‟ and „small oil volume‟. The latter is a design aimed at
reducing the fire hazard associated with the large volume of oil contained in the bulk oil
breaker. The operating mechanisms of oil circuit breakers are of two types, „fixed trip‟ and
„trip free‟, of which the latter is the most common. With trip-free types, the reclosing cycle
must allow time for the mechanism to reset after tripping before applying the closing
impulse. Various types of tripping mechanism have been developed to meet this
requirement.
The three types of closing mechanism fitted to oil circuit breakers are:
i. Solenoid
ii. Spring
iii. Pneumatic
CB‟s with solenoid closing are not suitable for high-speed auto-re-close due to the long
time constant involved. Spring, hydraulic or pneumatic closing mechanisms are universal
at the upper end of the EHV range and give the fastest closing time. Shows the operation
times for various types of EHV circuit breakers, including the dead time that can be
attained.

8.2.2 AIR BLAST CIRCUIT BREAKERS:
Air blast breakers have been developed for voltages up to the highest at present in use on
transmission lines. They fall into two categories:
A . Pressurized head circuit breakers.
B . Non-pressurized head circuit breakers.
In pressurized head circuit breakers, compressed air is maintained in the chamber
surrounding the main contacts. When a tripping signal is received, an auxiliary air system
separates the main contacts and allows compressed air to blast through the gap to the
atmosphere, extinguishing the arc. With the contacts fully open, compressed air is
maintained in the chamber. Loss of air pressure could result in the contacts re-closing, or,
if a mechanical latch is employed, re-striking of the arc in the de-pressurized chamber. For
this reason, sequential series isolators, which isolate the main contacts after tripping, are
commonly used with air blast breakers. Since these are comparatively slow in opening,
their operation must be inhibited when auto-re-closing is required. A contact on the auto-
re-close relay is made available for this purpose. Non-pressurized head circuit breakers are
slower in operation than the pressurized head type and are not usually applied in high-
speed re-closing schemes.
8.2.3 SF6 CIRCUIT BREAKERS:
Most EHV circuit breaker designs now manufactured use SF6 gas as an insulating and arc-
quenching medium. The basic design of such circuit breakers is in many ways similar to
that of pressurized head air blast circuit breakers, and normally retains all, or almost all, of
their voltage withstand capability, even if the SF6 pressure level falls to atmospheric
pressure.
Sequential series isolators are therefore not normally used, but they are sometimes
specified to prevent damage to the circuit breaker in the event of a lightning strike on an
open ended conductor. Provision should therefore be made to inhibit sequential series
isolation during an auto-re-close cycle.

8.3 BUS BAR:
Bus bars are defined as conductors which several incoming and outgoing lines are
connecting. This is essential component of switch gear. These are made of copper or
Aluminum. The bus bar section of high boring unit is connected by aluminum link. The
incoming and outgoing cables are provided with cables vanes, which welded steel
conductors. C.T. and P.T. used are of ring type they are fitted or insulation the installation
provided by cast-epoxy resin fitting.
8.4 POTENTIAL TRANSFORMER:
Transformer for measurement the voltage is called “Voltage transformer” or P.T. as short.
For the measurement of voltage the primary is connected to the voltage being measured
and the secondary to voltmeter. The potential transformer step down‟s the voltage to level
of voltmeter.
 C.T. is never open circuit.
 P.T. is never short circuit.

Infect instrument transformer are so important for insulating and range extension
purpose that it is difficult to imagine the operation of A.C. system without them.
ADVANTAGE:
There is low power consumption in metering circuit. the metering circuit is isolates from
the high power circuit hence insulation is no problem and the safety is assumed for the
operation.
8.5 Power Line Carrier Communications Techniques [PLCC]:
Where long line sections are involved, or if the route involves installation difficulties, the
expense of providing physical pilot connections or operational restrictions associated with
the route length require that other means of providing signaling facilities are required.
Power Line Carrier Communications (PLCC) is a technique that involves high frequency
signal transmission along the overhead power line. It is robust and there fore reliable,
constituting a low loss transmission path that is fully controlled by the Utility.
High voltage capacitors are used, along with drainage coils, for the purpose of injecting
the signal to and extracting it from the line. Injection can be carried out by impressing the
carrier signal voltage between one conductor and earth or between any two phase
conductors. The basic units can be built up into a high pass or band pass filter.The single
frequency line trap may be treated as an integral part of the complete injection equipment
to accommodate two or more carrier systems. However, difficulties may arise in an overall

design, as, at certain frequencies, the actual station reactance, which is normally
capacitive, will tune with the trap, which is inductive below its resonant frequency; the
result will be a low impedance across the transmission path, preventing operation at these
frequencies. This situation can be avoided by the use of an independent 'double frequency'
or 'broad-band' trap.
The coupling filter and the carrier equipment are connected by high frequency cable of
preferred characteristic impedance 75 ohms. A matching transformer is incorporated in the
line coupling filter to match it to the HV cable. Surge diverters are fitted to protect the
components against transient over voltages. The attenuation of a channel is of prime
importance in the application of carrier signaling, because it determines the amount of
transmitted energy available at the receiving end.

CHAPTER-9
START AND STOP SEQUENCE
OPERARING INSTRUCTIONS FOR MAHI UNITS:
Before starting the units the following precautions must be checked and ensured:-
1. AC-DC supply to control panels is on and all indicating lamps are healthy.
2. Draft tube gates are in fully raised portion and supported properly.
3. Penstock gates is fully raised and penstock gates ' opened' indication appearing on UCB
and control desk.
4. Draft tube drainage and dewatering system is healthy.
5. Cooling water system is charged and cooling water pressure after pressure reduces is
2/3 Kg/Cm2.
6. H.P. air supply system is healthy and pressure reduce is 42Kg/Cm2.
7. L.P. air supply system for brakes and turbine seal system is healthy and pressure in L.P.
air receiver is 5.0 Kg/Cm2.
8. Oil pumping unit system is operating and auto mode and maintaining normal working
pressure 37-40 Kg/Cm2.
9. ESV for emergency closing of guide apparatus is healthy and in reset position.
10. Air level in OPU sump and pressure vessel is normal.
11. Governor is in 'auto' mode.
12. OLU is healthy and operating on auto/manual mode.
13. CO2 fire extinguishing system is healthy and operating.
14. CGL system is healthy.
15. Oil level in all the bearing is normal.
16. Pressure in casing is normal i.e. 08.50Kg/Cm2.
17. Cooling water to turbine guide bearing is 'ON' and flow normal.
18. Clean water supply to turbine ceiling is on and flow normal.
19. Air pressure for isolating seal normal and seal disengaged.

20. Servomotor lock is raised.
21. Indication appearing on UCB and governor, before raising servomotor lock ensures
that governor limiter position is below 'Zero' -'ON'.
22. RTDs and TSDs are operative.
23. Cooling water to generator bearings are stator air cooler is 'ON' and flow normal.
24. Brake air pressure is normal to 45Kg/Cm2.
25. Brakes are released and brake relieves indication appearing on UCB.
26. All electrical and mechanical protection relays are reset condition and no any fault
abnormal indication appearing on communication panel and control panel.
27. PMGs switch (for governor supply) and station DC supply switch in electrical cabinet
of EHG is switch 'ON'.
28. Ensure generation circuit (GCB) and field circuit breaker (FCB) in 'OFF' position.
29. Ensure cooling water supply, pre-start check 'OK' unit ready to start indication
appearing on UCB.
AND UNIT IS READY TO START :-
SYNCHRONISING OF TWO ALTERNATORS:
For proper operation of alternators for synchronizing the following conditions must
be satisfied:-
 The incoming feed alternator must be it's terminal Voltage, Same as bus bar
Voltage
 The speed of incoming machine must be such that it's frequency must be
equal to PN/120 equals to bus bar frequency
 The phase of the alternator voltage must be intended with the phase of the
bus bar Voltage. It means that the switch must be closed at instant when two voltages have
direct phase relationship.
SYNCHRONIZING MANUAL:
The following steps have to be taken:-
1. Put check synchronizing switch (at bus coupler relay panel unit) at 'Synch In'
2. Select Sync switch SS-1 (at control desk) at manual mode and put on the synchronous
cope ON/OFF switch SS-3 (on Sync cope swing panel).

3. Compare and match Voltage and frequency by adjust AVR control switch and speed
setting case load switch.
When the synchronous scopes pointer is rotating clockwise and it is just crossing 12
O'clock position and synchronizes lamp can synchronoscope and sync panel glowing
bright close the MCB.
4. Put of SS-1 on Control desk and SS-3 on synchroscope.
5. Now increase load on unit by raising gate setting switch C4-4 (control desks up to
required loading)
6. Loading should be done by the raise/lower switch for speed/load setting on control
desk. If the balance current exceeds, the limit should be raised suitably by switch. If full
load is already reached. Lower by switch, whenever balance current exceeds the
depending on the grid frequency condition.
STOP SEQUENCE:
1. Reduce load to about 2Mw by gate setting.
2. Trip generator circuit breaker.
3. Hang over LT supply to station supply (LT panel at EL240)
4. Bring excitation to zero level.
5. Trip field circuit breaker.
6. Give unit stop command by IC0.
7. Watch application of break around 15Hz and starting of HS lab at about 35 Hz.
8. Gate limiter control switch should be left on AUTO mode for the next starting
operation.
9. Observe the stopping of HP cubical when speed comes to zero (If it does not stop in
auto mode put it OFF) Brakes will also be released.
10. Put guide vein lock in.
11. Close cooling water supply to turbine bearing and gland generator bearing and air
coolers transformers oil coolers after 30 min of stopping the unit.

CONCLUSION
Practice makes a man perfect.A student gets theoretical knowledge from classroom and
gets practical knowledge from industrial training. When these two aspects of theoretical
knowledge and practical experience together then a student is full equipped to secure his
best.
In conducting the project study in an industry, students get exposed and have knowledge
of real situation in the work field and gains experience from them. The object of the
summer training cum project is to provide an opportunity to experience the practical
aspect of Technology in any organization. It provides a chance to get the feel of the
organization and its function.
I have privilege taking my practical training at " MAHI HYDRO POWER HOUSE - I "
where power generation takes place in bulk. The fact that Hydro energy is the major
source of power generation itself shows the importance of Hydro power generation in
India
In Hydro power plants, the potential energy of water is utilized by the turbine to rotate coil
at high torque. The torque so produced is used in driving the coil coupled to generators
and thus in generating ELECTRICAL ENERGY.

REFERENCES
1.PLANT RECORD (Notes) : Files
2.A COURSE IN ELECTRICAL POWER : J.B. Gupta
3.PROTECTION OF POWER SYSTEM : B. Ram
4.POWER TRANSFORMER : Tata Magr.
Hill
5.ELECTRICAL ENGINEERING : Tata Magr.
Hill
6. MY GUIDE & FACULTY MEMBER
7. GENERATION OF ELECTRICAL ENERGY : B.R. Gupta
8.WEB-SITES:-
www.wikipidya.com
www.powersystems.com
www.powerengg.com
www.protectionofelectricalsystem.com
www.electricaltechnology.com

report on the Mahi power plant

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